Twl: I think that there is a BIG difference between poor tonal balance and proper timbre. Tonal balance has to do with frequency response linearity. Timbre has to do with pitch, harmonic structure and transient response. Judging from what the market is buying and manufacturers are selling, it doesn't seem as if either are important.
Jrd: For some manufacturers, the goal of achieving utmost accuracy and purity of signal leads towards price no object components. Other manufacturers ride the price escalation train and simply raise their prices without the associated effort or increase in performance. To be fair, it takes time, money and research to build the best product that you can. To expect phenomenal results at very low costs is simply day-dreaming. On the other hand, paying tall cash without obtaining some type of performance returns demonstrates a complete lack of value.
Drubin: For your reference on each review mentioned:
Fig 5 p 80 Legacy review states: "Legacy Focus 20/20, anechoic response on ribbon-tweeter axis at 50".... As a side note, the HUGE bass peak measured here would be even more prominent if sitting off axis of the tweeters. Given that the tweeters are 45" above floor level and an MTM array drastically limits vertical dispersion, one could expect an even boomier tonal balance. The phenomenal peaks at ( +5 dB's @ 6K and +8 dB's @ 12K ) may help balance this out though due to psycho-acoustics.
Fig 4 p 114 Piega C8 LTD review states "anechoic response on tweeter axis at 50". Once again, as one moves further off axis of the tweeter, either vertically or horizontally, bass response will seem to become stronger due to treble response softening. At least with the Piega, the tweeter appears to be closer to the average seated listening height. Compared to the Legacy which was reviewed in the same issue, Piega's would therefore sound "brighter" ( or "leaner" depending on perspective ) than the Legacy's with their tweeter positioned off axis. You have to compare apples to apples.
The Aerial review fig 5 p 137 states "anechoic response on tweeter axis at 50"... Given the height and position of the tweeter in this speaker, the perceived tonal balance might soften on top a bit compared to the Piega but would also be "hotter" than that of the Legacy. That's because the tweeter is centered between the two different speakers in terms of listening height.
As far as your comments about "non-humped" bass NOT sounding "right", that's because people aren't used to natural sound and don't listen to acoustically performed music. They have been "brainwashed" into thinking that elevated bass response, poor transient response and swapping more "apparent" bass aka "bloat" for true extension to be "normal" and how things should sound. As i've commented before, most people hear but they don't know how or what to listen for. Part of this could be personal preference, part of it could be a lack of familiarity with how instruments really sound.
As far as naming specific speakers go, that would be hard to do, especially in stock form. Can you point me to a well designed speaker that offers coherent arrival of the sound, linear in frequency response without major abberations, offers minimal ringing at any given frequency while producing good bass extension? Quite honestly, i can't think of a single modern day product that meets that criteria. Then again, finding one that was ever produced would still be tough : )
Nutella: Kudo's to you. Keep reading and learning. you'll end up with a better system and a lot more money in your pocket. Those that can't figure things out for themselves and get their information from the "candyman", who claims that sugar and starch don't cause tooth decay, are doomed to deal with a lot of "rot".
Agaffer: There are single driver speakers that produce deep and powerful bass, they just aren't made anymore. As to being "accurate", they can do that too, so long as spl's aren't climbing. There's much to be said for a speaker that produces the proper timbre with good dimensionality. If you don't know what timbre is, read my response to Twl.
Ed: Compared to many of the other offerings available, i would agree with you. That is, the Aerial probably is a better sounding speaker than most of the stuff out there. Given that i've never even heard these, i can tell that they have more design effort into them than many others. Reading the test results and knowing how to interpret them, it isn't hard to judge their over-all linearity, phase response, dispersion characteristics, etc... as being as good or better than much of the "high dollar" competition. Then again, there is obviously a LOT of room for improvement in this design, so what does that tell you? It tells me that either it costs more to build a great speaker than $23K will buy or the manufacturers aren't doing their homework.
Bigtee: I think that you are going to join me and a few others in the "outcasts of the audio society" if you keep saying things like this.
Drubin: Yes, linear response is the building block of both a pleasent and accurate system. If linearity doesn't matter, you might as well start using your old 10 band graphic EQ to colour the response to your personal tastes. After all, what's the difference in 5 - 8 dB's boost or cut if done at the speaker or at the EQ???
Bigtee: Thiel's and Vandy's both have problems with bass response linearity. Passive's are slower than ports in terms of transient response.
Other than that, my one major question is: Why don't speaker designers take into account the accepted "facts" of a normal installation and incorporate these attributes into their designs? Room gain, seated listening height, reflections, etc... along with linearity, transient response, etc... all seem to be "foreign words" to most of these folks. Sean
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Mejames: I have a LOT of respect for John Dunlavy even though i disagree with his point of view on the audibility of wire / cable changes in a system. Having said that, there are certain parts of his speaker designs that needed help. He acknowledged this when he upgraded / re-designed the SC 4's to the 4A's. While the 4A was "technically more correct", it seems like he fixed a few problems and introduced new ones. I think that a lot of the new problems were related to the new crossover design, which was far more complex. Parts heavy crossovers reduce the amount of control that the amplifier has over the drivers ( more "middle men" to deal with ) and reduce the detail that a speaker is capable of. My Brother's actively crossed quad-amped system is similar in design theory to that of the Dunlavy's. It is both more advanced yet much simpler in nature.
Lancel2000: You can't stop the bleeding once you've already got a wound. You can try to minimize the damages though, but various methods may introduce their own side-effects. Depending on the severity of the wound and the approach taken to try and "band-aid" it, the results and side-effects will vary.
Bigtee: I'm not quite certain how Vandersteen is working his "active coupler's", but they are some type of "fancy" passive radiator. I will give Richard credit though as he is a far more realistic designer than most speaker "engineers". He at least provides the ability to fine tune the electro-mechanical properties in his top of the line speaker and in the active subs. On top of that, he also uses more internal damping material than most vented designs, reducing internal reflections and reducing cabinet resonances. He needs to work on his tweeters though as there is something funny going on there. Most amps have a hard time loading into them, causing the top end to both soften in quality and fall off in output.
Gs: You are trying to introduce products designed for the "real world" here, but doing so in a back-handed manner that is not nearly as complimentary as it should be. From what i can tell, you slapped the people that you were trying to compliment and made a case against that type of product for those that seek "musical accuracy".
You basically said that if the device measured more non-linear in actual use after hand-tweaking but sounded "good", that was acceptable. As far as i knew, the whole idea behind hand tweaking / customizing is to improve linearity, which improves the sound also, under the actual operating conditions. It was not meant to introduce further signal degradation or specific colourizations. Then again, i want to hear what is on the recording, not have all the recordings sound the same or cater to a specific presentation. Maybe we have different goals.
Other than that, I'm all for products that are designed to work with their environment. I just don't know where they are or who makes them. To me, such a product is the MOST "technically correct".
The only problem with such an approach is that to market such a product and have the end user achieve the same results in their home, the product has to be operated within the boundaries of the original design parameters. Operating said product out of the design parameters basically negates all of the research and special attributes that went into making it what it is.
How many people ever read their product manuals? How many people actually follow detailed installation instructions? Not many from what i can tell. Between the lack of familiarity with the product, poorly written manuals and / or manufacturers that don't know how to design properly, most people never experience the joys that a good system that is PROPERLY installed can bring them. For that matter, most of the "professional installations" that i've seen were ALL wrong. With that in mind, how many "civilians" do you think can get it right???
As such, the manufacturer / sales rep / dealer / installer has to know the specifics of how a product is to be used and the end-user has to follow those directions. If one likes a product but it can't be used as intended in their specific installation, it should be avoided. Placing a speaker out in the room that was designed to be placed near the wall ( or vice-versa ) will negate any of the "real world" benefits of that design. Not only will such a product probably deliver far poorer performance, there will be quite a few side effects too. Hand tweaked / room optimized designs are only as effective as implimented.
Onhwy61: Good points, especially about the one-third octave averaging graphs. My guess is that the results weren't very flattering, hence their lack of inclusion. Sean
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Roy brings up some great and very valid points. Speaker design is obviously VERY complex and loaded with design trade-offs. Having said that, Roy's comments also point out that the room has to be taken into consideration i.e. how the drivers "blend together" and "load up" in the actual listening area. Since most designers / manufacturers don't take all of these factors into consideration, they end up with a product that lacks "universal" application and / or works well in some aspects but is quite limited in others. All of this for only a few thousand dollars : )
One of the points that Roy mentions is the phase shifts that take place within the audible band when using multiple drivers. Part of why people "love" single drivers is that this is less of a problem. Instead of dealing with multiple different radiation patterns, transient responses and phase shifts, you have one point source radiator. Most all of these problems are drastically reduced, resulting in a far more "unified" or "cohesive" presentation. You don't have to worry about how one driver blends with another because you've only got one driver.
This is one of the reasons that i love my Ohm F's as much as i do, as limited as they are. Being a single driver design with the horizontal radiation characteristics that they offer, they do some things that no other driver / speaker can offer. At least, no others that i've heard.
Drubin: Naming names gets hard to do, for both good and bad reasons. The "bad" reasons are obvious i.e. potential legal ramifications. Believe me, i've gotten more than a few emails about this subject. Only thing is, someone can't sue you for telling the truth using statements that are verifiable.
As far as the "good" goes, i have a hard time finding any "manufactured" speakers that are worth recommending in stock form. It's hard to use something as an example when you can't find a suitable sample.
If you want some basic recommendations, avoid ports and passives. Both introduce increased amounts of resonance and phase shifts into a system. I've posted links to a few discussions that cover this topic that i had over at AA, but i'll see if i can find them and post links to them again later tonight. Sean
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PS.... Obviously, i'm NOT familiar with EVERY speaker or audio product out there. It is quite possible that there are some excellent examples out there, i just don't know of them or enough about them to use them as a reference. |
No, using multiple woofers is not the culprit. Poor design skills, using too small of a cabinet for the given drivers and not enough internal damping material inside the cabinets themselves are the culprits. Larger cabinets produce resonance at a lower frequency, hence offering more linear bass extension. Poor tuning of the ports / improper bass alignment is what produces the single huge peak. The very wide bass plateau's are caused by not using enough damping material inside the cabinet. Just further evidence that too many "manufacturers" are using "computer software" to design their products. They do this because they don't really know how to build & design a speaker on their own, let alone tweak the results that the computer program itself provided.
As a side note, most people think that vented designs should use physically smaller cabinets than sealed designs. That is exactly the opposite of the truth in most cases. The general public has been lead to believe this because many companies use vents in very small speakers. This was not to give more bass extension so much as it was to "fool you" into thinking the speaker had better bass. What they did is give you more apparent bass with higher sensitivity i.e. quantity over quality. The whole reason that Edgar Villchur and Henry Kloss designed the acoustic suspension speaker was that it offered the best bass response characteristics that one could achieve in a smaller box.
At the time that they were designing the Acoustic Suspension speaker, other designs used some type of vent or open baffle and the cabinet had to be HUGE to get any kind of deep bass out of it. Not only do acoustic suspension speakers provide better transient response, they also offer a slower roll-off below the point of resonance. As such, a vented design that resonates at 45 Hz will be -24 dB down at 22.5 Hz ( one octave ). A sealed design that resonates at 50 Hz ( vents always look more impressive on paper ) is only -12 dB down at 25 Hz. You tell me which speaker has better extension in the real world. Then factor in transient response, which sealed speakers do better. Now ask yourself why a manufacturer would want to use a vent and you'll figure it out soon enough. They are cheaper to build, cheaper to ship, offer more apparent bass and take less power to pressurize the room. The bottom line is more profit, more bass, more sales.
With such a situation, how can they lose? There is only one way that they could. So long as they keep the consumer in the dark and hope that they never become educated or learn how and what to listen for, they'll keep racking up sales by pushing garbage out the door. High profit garbage at that. Sean
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Duke: Traditional vent systems typically tune the vent at the same appr frequency that the woofer resonates at. This produces two smaller "humps" rather than one larger hump. Bandwidth is increased and overall bass sensitivity also climbs over a wider region. By doing so, you've now got two resonant points, which are really nothing more than undamped oscillation from the driver and the vent. These are two points of oscillation that the amplifier can't load into or control ( due to impedance peaks ), producing twice the potential for music to excite them with the resultant increase in "slop" i.e. undamped / uncontrolled output. Couple this with the elevated output due to the increased sensitivity in this region and the "room gain" that naturally takes place and you can see why we've ended up where we are today with MOST vented designs. The other alternative to tuning a vent is to let the woofer resonate where it wants to in that cabinet and then tune the vent for whatever frequency that you want to try and extend output to. While this does increase extension somewhat and produce a shallower roll-off ( with resultant improvements in transient response ), the lowest region isn't as efficient as the upper region. This "can" produce a more natural presentation IF properly implimented, BUT, you've still got the associated phase shifts, lack of damping below the vent tuning frequency and reduced power transfer / lack of control associated with higher impedance peaks that vents typically demonstrate. In plain English, we've still got plenty of side-effects / problems to deal with using such an approach, even though they aren't as prominent as the more conventional designs. As far as various alignments offering a different set of trade-offs, I know this and you know this, but in order to educate and share with those less familiar with the subject, you have to start with a base-line that they may be familiar with. As you mentioned, this type of tuning is not commonly used. That is why i didn't base my descriptions / argument on this type of vented design i.e. it's not widely used. Having said that, there is one very well known ( but NOT widely respected by audiophiles ) manufacturer that advocates such designs. That manufacturer is Cerwin-Vega. As a side note, Stewart Hegeman used a very unique approach when designing vented speakers that some might consider to be similar to the above. I can see how it could have quite a bit of merit if properly applied. There is only one "manufacturer" that i know of using such an approach and that is Don Morrison Audio. While i've never heard these speakers, they do seem to try and tackle quite a few important aspects of speaker design. Don has been working with this design over time and seems to be on the right track from a technical perspective. If interested, Don also makes a small two piece preamp that some rave about. I am NOT "endorsing" or recommending either of these products although i will say that Don seems to be more than technically competent. Having said that, his preamp should go lower in frequency response though : ) Other than that, i know that Richard Shahinian of Shahinian Acoustics has acknowledged that Stewart Hegeman was a primary influence on his designs. Given that Hegeman was also one of the first that i know of to use metal cones ( not just for tweeters ) in his speaker designs, i would have to say that his thinking was ahead of many others. The first speaker that i know that used actual "metal" in it ( but not the whole cone / piston area ) was the Ohm A. While this was a revolutionary design in itself, i could be wrong here and there might have been others using "metal" in their drivers prior to the first Walsh based design. Sean > |
Hopefully, some of you folks that are interested in learning will be able to follow along with this.
To try and put things in understandable terms, the "Q" of a speaker relates to the amount of damping at resonance. The speaker with a lower Q has more damping. It is this damping that keeps the speaker from going into oscillation. Higher Q designs go into oscillation both easier and to a greater extent once excited. This is what causes both the higher output at resonance ( bass peaks ) and the poorer transient response. After all, if the driver itself is undamped and resonating, there is nothing to stop it from ringing. Ringing equates to poorer transient response and lack of definition. One note "blurs" into the next.
Think of a low Q speaker as having a lower noise floor i.e. more "inter-transient silence". A bass note will hit, stop on a dime and then play the next note. Once you hear such a system, the difference in definition, separation of notes and "speed" is quite apparent.
Having said that, most people that hear a sealed speaker with a Q of .5 or so think it sounds noticeably lean i.e. just like Clara Peller of Wendy's hamburger fame yelling "WHERE'S THE BASS" : ) For sake of reference, Dunlavy shot for a Q of .5 in his larger designs. AR aka Acoustic Research also used a Q of .5 in some of their larger models "way back when". If you do some research, you'll find that AR and Dunlavy shared many similar design philosophies.
A Q of .7 in a sealed design is much more common and still provides pretty reasonable damping / transient response. This gives you more apparent bass AND more extension without getting "sloppy". Just like the "bass hump" that designers / engineers are building into the ported speakers, the reduced amount of damping at resonance ( higher Q ) allows the speaker to look better on paper i.e. slightly lower F3. Personally, this is the highest Q that i find acceptable in a sealed design. As a side note, .7 to .8 is the "marketable" sound of a sealed speaker i.e. it still has enough bass to attract the "thump happy" folks that buy vented systems while retaining good enough transient response to not annoy those folks that crave "accuracy".
With all of that in mind, one has to take certain factors into consideration when designing a speaker. First of all, the lower Q really DOES have better transient response. Some people find this to sound somewhat "dry" though as the lack of ringing seems to cut the notes short. The truth is that they are just too used to listening to "slop" and need to get re-educated ( both ears and brain ) on the subject. Given that my Father has Legacies and i just went through and re-designed them, i'm going through this with him right now. He can hear that the bass has GOBS more speed and articulation, but he still thinks it sounds "lean". In comparison to the bloat that he had before, it does : )
On top of all of that, the Q of a system changes as the driver heats up. When throttling a speaker system, it would not be uncommon for the Q to start at .5 and climb up to a Q of .6 or possibly even a .7 or so. As such, speakers that start off with a .7 are now at a .8, .9 or possibly a 1.0 under heavy load. While this may lend more "drive" the music, it is also sloppier and less accurate. Then again, if you've had a few "liquid refreshments", you're probably less apt to notice this : )
The "temperature fluctuation" and "Q variance" are a few reasons why some designers shoot for a very low Q to start off with. Using this approach, the speaker system offers very fast / accurate transient response at low to medium levels. When pushed harder, the Q does climb, but not high enough to completely destroy the "speed" & "definition" that the listener is used to at lower volumes. If one started with a Q of .7 and ended up at 1.0 when hitting the throttle, the difference in "bloat" would be more apparent as transient response is now noticeably poorer than if one went from a Q of .5 up to a Q of .7 under load.
There are some speaker designs that utilize VERY high Q's. If i can remember correctly, the big Carver ribbons had a Q of well over 2 !!! While this seems phenomenally high ( it is ), it isn't quite as high as one might think in this specific application. If this were a more "normal" design with the woofers mounted in a box rather than free air, the bass would be attrocious. Due to being free air or "dipolar" in radiation, you get a LOT more cancellation from out of phase reflections. By introducing a HUGE peak at resonance, the bass that would normally be lost / thinned out due to cancellation is somewhat recovered due to having such a big peak. To anyone that has never heard the larger versions of these speakers, they are known for having over-powering bass. Not only is there too much bass, but what is there lacks definition and speed. If one were to take this design and substitute drivers with a lower Q, they would end up with a much better product. If this sounds like some speakers that are currently being marketed, just remember, they didn't copy the Carver's, the Carver's simply served as "inspiration" : )
Drubin: Very few companies market sealed designs. Even if the designer has enough integrity to market a great product, most reviewers and end users wouldn't know what to do with an accurate speaker. Probably the first thing that they would do was complain that it sounded "lean" because they are used to listening to "indistinct bloated thump". Sean
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*At one point in time, AR had over 32% of the loudspeaker market and only sold sealed designs. To put that into perspective, Bose is currently the largest speaker manufacturer in the world. As far as sales go, Bose products garner appr 13% of all speaker sales made. Granted, there are more people buying speakers today than ever before, but that should tell you how "powerful" AR was in the marketplace at their peak. As a side note, AR "invented" acoustic suspension ( sealed & stuffed ) designs AND they also invented the dome driver ( tweeters and mids ). As a general rule, the average dome is FAR more "linear" or "accurate" than the average cone driver. As has been previously noted though, linearity and accuracy went out the door a long time ago, so AR products fell out of favor. Not coincidentally, this took place at the same appr time that vented designs started to flood the market. Once again, quantity of sound won out over quality of sound. Having said that, the influence of some specific AR designs are highly evident in several different product lines. Believe it or not, one can show direct correlations between specific AR designs and some of Bill Dudleston's Legacy designs. The difference here is that AR actually used cabinets that were of suitable size for their multiple woofers and retained the sealed design. |
Drubin: Why do you think that i've said that it is difficult to reference "box stock" speakers? The pickings are phenomenally slim. Even those that do some things "right" are "hurting" in other areas. Bombaywalla: I don't doubt that Roy is capable of building a good speaker, i'm just not real familiar with anything that he makes. His input here has always come across as being both honest and intelligent. These are odd yet admirable traits for a product manufacturer on an audio forum. I guess that in itself speaks volumes about the way that he does things : ) Bigtee: I had subscribed to Hardesty's Audio Perfectionist for a time, but let my subcription run out. Quite honestly, I ran into problems downloading / printing it out. Richard was VERY good to work with though, making this less than trivial. I probably should renew my subscription as he at least has the "balls" to say what he thinks. I have to respect someone like that, even if i don't agree with them all the time. If someone isn't familiar with Hardesty's work, i would suggest taking a look at the "Watchdog" series of articles. Some of them are less relevent than others, but you'll at least get a feel for what he's capable of writing. Duke: When i first heard some CAR's, i thought that they sounded pretty good. They were somewhat "thrown" in a room with less than ideal placement and still managed to receive a standing ovation at an audio show. Given the less than stellar acoustics and lack of "hi-fi" installation, that says a LOT about a product to me. With that in mind, i thought that the bass was slightly tubby sounding and that there was s slight dip in extreme upper mids / lower treble region. As mentioned though, the bass problem may have had to do with less than optimum placement and show conditions, etc... Given that i wasn't familiar with ANY of the gear being used at the time, i don't want to throw stones at John's work. From what i could tell, it was quite good. Other than that, a shallow slope is great. Not only does this mean greater extension, it also equates to reduced phase shifts. My main concerns here would be the amplitude of the peak at resonance and the impedance at and near resonance. As you know, the bigger the peak that you have, the greater the oscillation. The greater the oscillation, the less control you have and the more ringing ringing. None of these are desirable traits. As far as impedance goes, the greater the peak, the less power transfer. The less power transfer, the less control. The less control, the poorer the sound. Both of these "problems" are common sore-spots with the mass majority of vented designs. For others that are just joining us or would like to re-visit some very "informative" threads that discuss low frequency characteristics of various designs, try these links over at AA. The first one here involves Dan Wiggins of Adire Audio along with Bobby Palkovic of Merlin. Needless to say, i made a LOT of "new friends" on this one : ) sealed vs ventedHere's a post that i made almost five years ago about this same subject over at AA. It really doesn't cover any new ground, but simply shows that i've been relatively consistent in my stance for many years prior to the current uproar : ) deep and accurate bass means...There are several other threads that specifically deal with vents & Legacy's that also contain technical info. I didn't post links to those as there is one that demonstrates that Bose are superior products to Legacy's. I didn't want any of the Bose fans here to think that i was "on their side" though : ) Sean > |
Drubin: How can i make this easier to understand? I'm not aware of any speakers in box stock form that i really like or think are phenomenally well implimented. On top of that, I don't know of any current production speakers that are sealed and of a low Q design. As far as sloppy bass response goes, head to your local audio salon and listen. If its got a vent of some type, you've got your answer. Dawgbyte: Glad i at least gave you something to laugh about. Even if it was me you were laughing at. If you read that entire thread, the guy that claimed to be an EE was asking for help in building / designing a subwoofer. As i mentioned in that thread, if he's an EE, why didn't he do the math himself? Didn't he trust his own skills and electrical engineering degree? As a side note, i had no idea who i was replying to or their level of skill or understanding, that's why i asked what i did. Besides that, just because someone has a degree ( IF they really did ) and sits at a desk engineering products, that doesn't necessarily mean that they want to get their hands dirty by building what they designed. That's the difference between a "desk jockey" and the laborers that actually make the products and keep the economy moving. Other than that, i didn't see anybody post any information that refuted the points that i made. In fact, several of the arguments that were presented to refute my statements ended up supporting the points that i was making. While you may find the biggest point to be at the top of my head, facts is facts and marketing is marketing. I didn't exactly see too many manufacturers willing to defend their "state of the art" products in that thread either. The ones that did didn't fare too well. One of the two that did participate partially acknowledged the points that i was making. At the same time, they also tried to convince me that one of their vented designs worked quite well for what it was. Given the limitations of the specific product being discussed, i agreed with his design approach. I also went so far as to state that their two-way design had better response than some large towers using multiple dedicated woofers. The other manufacturer admitted that sealed designs are superior, yet could be expensive if seeking the ultimate in both extension and spl capacity. Their designs concentrate more on quantity than quality. The fact that they presented info about their own products that demonstrated the lack of engineering involved only helped to prove my point. On top of that, other parts of their rebuttal displayed further ignorance of the amplifier / speaker interphase and the relationship that impedance matching plays between them. One questions for you. If i am / was "SO wrong" in what i was saying or how i was saying it, why didn't a knowledgable EE or speaker designer / manufacturer jump in there and slap me silly? If you don't think that HORDES of EE's, designers / engineers / manufacturers don't read that forum, guess again. By the way, i don't use "grease". This stuff works much better as a lubricant and comes in all forms. You might want to see if they offer a product that is consumable by humans. It may ease your problems with constipation : ) Sean > |
Transmission lines have potential but are phenomenally hard to build and fine tune. Given that most manufacturers can't design / build simpler products, i don't hold much faith in them getting a more complex product like a TL right.
As a side note, AudioXpress had some recent articles about a TL design. From what i walked away from that article with, my thoughts about them being very complex / hard to optimize were only reinforced. Tons of higher frequency rippling taking place, etc... along the length of the tunnel. Even more than a poorly designed port. Obviously, one would have to do a lot of experimenting with different types, densities and placement of damping materials to get things dialed in. As such, sealed and stuffed is hard to beat from either a mass production or hand built / tweaker point of view. In many cases, simpler really is better.
As far as "pressure relief" enclosures go, are you talking about Aperiodic's aka "vario-vents"? Sean
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Ernie: I am well aware that there are exceptions to the generalizations that i've made. From what i have seen and heard, they do exist. They just aren't commonly found or available due to going against the grain of the marketing hype that currently exists. Dealers don't want to carry products that don't sell and these products don't sell because the average consumer hasn't been educated or know what to listen for or how to listen for it.
For this, i blame the audio industry and the press. They are responsible for the "trick bag" that the "high end" audio industry has worked itself into. Due to their marketing games and the profit margins generated from under-designed products, the average consumer can't tell the difference from a "salon" speaker to a Best Buy speaker. That's because they all demonstrate severe forms of non-linearity. The only differences that they can tell is if one is louder than the others and if it produces more bass. I also forgot that they know how to look at the price tag, which has them scratching their heads and asking why they should spend THAT much more without getting measurably superior performance.
Duke: Given proper design, a TL will always be larger than a sealed design. To most people, size counts. Regardless of how many advancements have been made in TL design, they are infinitely more difficult to design / build / manufacture than an equivalent sealed design. Since manufacturers and DIYer's are less apt to venture into such waters, i've tried promoting a design concept that is both simple and cost effective to work with and produce while offering excellent sonic performance.
As i've mentioned before, i don't consider the simple sealed box to be the ultimate in design. I do consider it to be the best bang for the buck with the least skill and knowledge required. As Mr Dartford stated, the less potential to screw things up ( i.e. the simpler that you keep them ), the more likely you are to achieve a higher percentage of success.
Once one has achieved a high level of succcess through following sound ( as in "proper" ) design & engineering practices, refining the basic design and striving for the highest levels of performance enters into the world of diminishing returns. The last few percentile of measurable performance tends to cost more than what it would cost to build another system of similar stature.
As such, i would rather see folks get 80% - 90% of the performance out of their systems at a reasonable cost than to see them pay exhorbitant amounts for much reduced performance. The fact that many end up doing the latter rather than the former due to being fooled by advertising and marketing trends makes it harder to recruit civilians and keep this industry strong. It is difficult to justify added ( let alone exhorbitant ) expenses when the ends don't justify the means.
As with any type of system or project, should one choose to seek a higher level of performance than covering the basics with good design principles and proper implimentation, they should bring their wallets and valium with them. It is a steep slope that will have one stepping into uncharted territory. That is, as far as most audiophiles and even most "pro's" are concerned.
As such, getting past the marketing hype and high prices is only a small portion of why i promote sealed designs as heavily as i do. The fact that they have the potential to perform in both a measurably and sonically superior level compared to 95% of the designs out there while taking up less physical space could only be considered a benefit.
Either way, people can buy / build / spend their money on whatever it is they like. As i've said before, there's no sense in catering to someone else's preferences. As i've also said before, those that are interested in achieving optimum results without spending maximum cash need to educate themselves on the subjects. The more that an individual knows, the less likely that someone else ( me included ) is to steer them in the wrong direction. Sean
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Ernie: Sealed and stuffed is smaller than vented when the vented systems are properly designed. Most vented products aren't designed properly, hence their smaller size / built in trade-off's right off the bat. Sean
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Nothing is free. The trade-off with the "free" output is the increased roll-off rate below resonance ( 24 dB's per octave vented vs 12 dB's per octave sealed ), poorer transient response, increased potential for woofer damage when fed a signal below the tuning of the vent, out of band output leaking out of the port, etc...
In many cases, even though a sealed design may have a higher point of resonance than the vented design, the sealed actually has more usable output at a lower frequency. This is due to the shallower roll-off rate. Since the vented design rolls off twice as fast, the resonance of the vented design would have to be exactly half that frequency or lower to achieve the same output level at -12 dB down.
Even with the added "free" output, we've seen how most vented designs actually work in the real world. That is, they are far from "natural" sounding due to the peaks introduced at both the driver and vent resonance AND transient response is typically poorer. Is that "free" output really all that it's cracked up to be? This question becomes even more redundant when we consider how low the dollar per watt ratio of some pretty reasonable sounding amps are today. Sean
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Cdc: While i personally believe it takes "big power" to do bass correctly with most "audiophile approved" type speakers, this is only a very small percentage of the big picture. None the less, i put my money where my mouth is and have 1000+ wpc driving my dual subs in my main system, 1200 wpc driving my HT mains with 1600 watts driving just the subs in that system, a dedicated amp rated at 100 wpc driving the subs in my bedroom system, 800 wpc driving the speakers in my office system, etc...
As you mentioned, dynamic compression, rise and fall times, ringing, phase shift, frequency response linearity, loading characteristics ( Z aka "impedance" at resonance, etc... are all other important factors. Given that vented designs typically have poorer rise and fall times with increased ringing, and vents introduce multiple phase shifts rather then the one that sealed designs offer, and typically have peaks at resonance whereas low Q sealed and stuffed designs don't, and vented designs typically have a higher impedance, which translates into less amplifier control and ability to load power than a low Q sealed design does, etc... Obviously, you can see where i'm going with this without me continuing any further.
As to your question about "playing with the damping of vent", this can be done. This is much the approach of a stuffed Transmission line and a Vario-Vent or "Aperiodic" design. Both offer many of the benefits found in sealed designs and may even surpass sealed designs in some areas. These are both somewhat "tricky" to design though. Some of the old Dynaco speakers were "Vario-Vents" and produced very good bass output AND definition for their size. That is, so long as you kept the spl range within reason.
As far as the JMLab's speakers go, i thought that the they sounded "barrel-chested". I think that much of this could be solved by adding damping material into the cabinet. The reason that it sounds like a "barrel" is that you literally have a large open wooden chamber resonating away. By adding damping material, you reduce both the excitation of the cabinet itself and absorb some of the energy that would otherwise be bouncing around in the cabinet causing a "bass echo" or "ringing".
In terms of "tighter bass" sounding "lean", that is a common thought. That's why i've stated that people are just TOO used to "bass slop". When they hear what tightly controlled bass with minimal overshoot and ringing sounds like, the articulation and definition is readily apparent but they still can't get used to NOT hearing all of the overhang. Most equate "bass slop" with "bass weight", which isn't quite the same thing.
As to your specific questions, here goes:
1) As to your comment about Musical Fidelity gear, most that i've heard sounds noticeably lean. Haven't heard all of their models though, so can't answer that specific part of the equation.
As far as i'm concerned, you shoot for speed and neutrality throughout the entire system. If you try to go with any other approach, you're back to "complimentary colourations".
2) Properly designed speakers are designed to work with specific room boundary effects taken into account. If a manufacturer doesn't provide basic suggestions as to where the speakers should be placed, chances are, the speakers are going to sound VERY different from room to room. Since obtaining neutral response in a consistent manner should be the goal of most "audiophiles", speaker design and placement become key factors in what we hear and total system performance.
Other than that, most designs already suffer from bloated bass as it is. Adding further low frequency reinforcement by placing the speakers closer to a corner, rear wall or both, etc.. will only make the presentation sound thicker and slower. With that in mind, some high-tech speakers with a lot of research put into them are designed to be placed up against the wall. If you pull them out from the wall, you'll have too lean of a presentation.
3) It is not so much the roll-off that makes a speaker hard to set-up, it the "Q" of the peak at resonance. Q covers both the amplitude and bandwidth at resonance. Speakers with a lower peak at resonance will be easier to place because the bass sounds less "one notey". Speakers with a narrower bandwidth peak will also be easier to place because they have less chance of exciting the various multiple nodes spread over a wider frequency range that exist in every room.
What the shallower roll-off of a sealed design offers is greater usable output below resonance. Once a vent is done, it drops like a rock. Anything below the point of resonance on a vented system unloads ( minimizes damping ) on both the vent and the driver. Excursion of the driver increases and the bass becomes quite muddied due to the uncontrolled extension. Better vented designs, like that of the Merlin's, use some type of high pass filtering to minimize these problems.
As far as Thiel's go, the placement problems with them may be two-fold. First of all, they use passive radiators. Passive's are slower than ports in terms of transient response. Slower response sounds muddier, making it harder to find a position in the room where the "mud" is reduced AND nodes aren't excited. Couple this with treble response that may require slightly different speaker positioning to work optimally and you've got yourself a lot of work ahead of you finding a good compromise between the two.
This is why i said that properly designed speakers will take into account room reinforcement. The designer should be able to give you an idea of where the speaker will work best in your room. While every room is a little different and may require some trial and error, those suggestions should get you pretty much in the ballpark. After all, they are familiar with the bass peaks, roll-off rate and can factor in room reinforcement from there. On top of that, they should have taken into account these factors when designing the rest of the speaker too, so the mid / treble radiation pattern should be designed to compliment optimum bass reproduction.
As i've mentioned before, very few speakers take all of this into account. If they did, you would be seeing a lot more "oddly" shaped speakers with acoustic treatment on the baffles. Reducing diffraction of the baffle itself is one thing, but taking into account room interaction with that baffle is one step ahead of most designs. Sean
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Greg: Room gain is very difficult to calculate and will somewhat vary with size of the room and speaker placement within the room. This is why good engineers design a speaker for specific placement within a room. Bare in mind that i'm not just talking about bass loading characteristics either. That way, they can factor in specific low frequency reinforcement factors AND dispersion characeristics consistent with the placement that the speakers will be used in.
While many people don't take such things into consideration when making their purchases and can't figure out why their speakers don't sound good where they have them placed in their room, they may also be the same type of people that buy a 4 wheel drive SUV to drive around in the city and / or take long trips on the highway with. While one can argue "vehicles are a matter of personal preference", one can also say "mis-application of a product outside of its' intended use will deliver less than optimum results". One can use such a product and be happy with it, but that doesn't mean that something else that was more suitable for the task at hand wouldn't have worked even better.
This is why i've stressed factoring in room size and placement in varous threads. Great speakers in the wrong room and / or great speakers that are improperly placed soon become "bad speakers" that they can't get rid of fast enough. Too many folks end up buying speakers that were designed to operate in a different environment than how they want to use them and then end up paying the price.
Ernie: I would suggest that you read Vance Dickason's Loudspeaker Design Cookbook. Your understanding of cabinet size and bass extension / output needs some help. I don't mean this to sound rude, as i was under many of the same false assumptions when i first started reading / learning about speaker design myself*. The fact that there are loudspeaker designers / manufacturers that don't fully understand many of the variables involved speaks of how complex of an issue this really is.
Part of the extension / total output / lower F3 on a vented system comes from the fact that, with such a high amplitude peak at resonance, the output, which is frequency related, has to fall off quite a bit before going below the average output level.
For sake of an example, let's assume we have a speaker that averages 88 dB's across the band. Due to the undamped oscillation at resonance of the driver / vent combo, there is a +5 dB peak in the low frequency region. As we've seen, this high of a figure on a vented design is not unrealistic and is possibly even conservative on some designs. This means that at the point of resonance, the output of the speaker is at 93 dB's. It is only after the lowest tuning frequency of the vent occurs that the speaker begins to roll off. That means that roll-off starts AT the peak.
Starting off with such a high peak means that we now have to lose 5 dB's of output just to get back to the reference output level of 88 dB's. In order to find our actual F3 ( -3dB point ) of this design, we've still got to lose yet another 3 dB's of output. This would give us a total of an -8 dB drop before we actually made it to the frequency where F3 is measured.
As you can see, since roll-off occurs at the same rate that frequency is lowered, building in a bigger peak at resonance automatically gives you more extension. That is, as it looks on paper using a -3dB reference point. Other than that, one can introduce such a peak into a sealed system with an EQ and still enjoy the better transient response of the sealed box. If you want to mention the phase shifts that the EQ brings with it as being detrimental, i'd like to mention the phase shifts that the vent brings with it.
As to your question about "what's wrong with a 24 dB slope", that answer has to do with linearity, transient response and ringing. The sharper the slope, the poorer the transient response, the more ringing and the less phase accuracy. This is why most "high end" audio gear strives for wider bandwidth with gradual roll-off. Better out of band performance equates to better & faster in-band performance. Same goes for speakers.
The question here is does one want more total output with a lower F3 at the expense of added bass bloat aka "lack of control", reduced linearity, poorer transient response, etc.. or is a slightly higher F3 with improved transient response and linearity more desirable? Since F3 only tells a small percentage of the picture, take a look at this. For sake of clarity, these figures are based on the accepted principles that vented systems fall at a rate of 24 dB's an octave and sealed designs fall at a rate of 12 dB's an octave:
-3 dB's on a 40 Hz vented system
-12 dB's at 30 Hz
-24 dB's at 20 Hz.
-3 dB's on a 50 Hz sealed system
-12 dB's at 25 Hz
-24 dB's at 12.5 Hz
While the initial -3 dB point on the vented design looks better on a spec sheet, it actually offers LESS extension when all is said and done. This is true even though the sealed design looks "weak" at an honest 50 Hz rating. On top of that, the vented design has all of the other problems i.e. reduced transient response, increased ringing, more phase errors, out of phase leakage from the port into the upper bass / lower midrange region, etc... You have to deal with all of these sonic drawbacks as tis type of design tries to get you the limited extension that if does offer.
This is not to mention that the vented system is completely "unloaded" or "undamped" below 40 Hz. Any low frequency notes fed into the speaker below that point will only result in massive excursion with the potential for damage / increased distortion. If you've got vented speakers and play vinyl, DO NOT try to play massively warped records at high volume. This will cause MASSIVE "woofer flutter", possibly resulting in permanent damage.
As a side note, it is quite possible to design a bass hump / resonant peak into a sealed design. By increasing the Q, you get such a peak. Like the vent, the transient response is reduced and ringing is increased, but unlike the vent, the slope remains shallower and phase integrity is not damaged quite as badly. As such, it is possible to match the F3 of a vented design with a sealed design, but the benefits of improved transient response are partially negated.
Vented designs DO look "more impressive" on paper, but that is only because the spec's that we use to quantify the performance of speakers aren't quite as sophisticated as those that we use for electronics. On top of that, there is no such thing as electronics / room interphase like there is with speaker / room interphase.
Vents vs sealed boil down to quantity vs quality. Vents will almost always give you more total output, but at great expense. Sean
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*To be honest, i was under the impression that vented systems allowed smaller cabinet size and greater extension for many, many years. I could never understand why someone would want to buy a bigger cabinet that didn't play as low and took more power to operate. That's because i was reading spec's but didn't know how to interpret them, nor had i actually listened to a lot of sealed designs at that point in time.
The reason why the sealed cabinets were "bigger" was because they were properly designed and tuned for extension. The vented cabinets were tuned for more apparent bass and higher output i.e. the illusion of "deeper" bass via "more" bass. This is how most "Pro" speakers are also designed and you can see further evidence of this by reading Bill Fitzmaurice's articles in Audio Xpress. |
El: If such is the case, why not just run an equalizer to fine tune the sonics to what one wants to hear? One can achieve such results without spending much money at all. What does it matter what the source of colourations are so long as one enjoys the final presentation?
I think that a lot of people that were striving for accuracy and thought that they were buying products that would give them that have been lead down the rose path, thorns and all, by the manufacturers and dealers that took their money. Of course, neither the dealer nor the manufacturer could have done this by themselves without some help, so that is where the audio press comes into play. Promoting the "flavour of the month" mentality surely hasn't helped the industry / end-users in the long run.
High end used to be about achieving accurate and musical reproduction of what is on the recording. Non-linear reproduction is not accurate and super-imposing excessive bass / treble or both onto every recording isn't exactly "musical" either. If one prefers such a presentation, so be it. I don't think that most people reading these forums would call such a presentation "high end" though.
Other than that, i think i've more than expressed my point of view on this one. I'll give it a break and leave those that are annoyed alone. Sean
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Duke: How many "exceptions to the rule" that you describe above do you know of that are being marketed?
Aside from the aspect of roll-off rates, changing the box alignment still doesn't deal with the lack of transient response / out of band port leakage / lack of damping / potential for over-excursion that comes with all vented designs. You simply can NOT take an out of phase signal and use it to reinforce the in-phase signal without multiple drawbacks / repurcussions. With that in mind, it is up to the designer to prioritize which trade-offs are most / least important. When one can avoid most all of these and achieve relatively similar / better results ( except for sensitivity ), there is only one reason to accept the trade-offs that come with vents. That reason would be a lack of available power, which is no longer applicable with modern day designs / technology.
As one tries to achieve greater extension via manipulating the alignment of a vented design, the transient response gets worse. If you want better transient response with a ported design, you have to limit the low frequency extension. Even if you take this approach, the woofer is still unloaded / lacks damping at frequencies below resonance. The fact that you've raised the F3 to obtain improved transient response now exposes the woofer to even greater potential for over-excursion due to having a higher resonant frequency. The higher the resonance, the more potential for woofer overload at frequencies below that point. On top of that, we still have out of band vent leakage to deal with.
One can play all day long with computer simulations, but you can't fight the laws of physics. There are trade-off's involved with every type of design. Rather than try to bend and twist the rules, developing even more problems with increased levels of complexity, why not choose the simplest design with the least amount of trade-offs and work towards optimizing that? It seems that man has a way of making the simplest things in life more difficult than they need to be. Sean
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Good points Joe. Once again, you've added a brief but very cogent analysis of the how's and why's. In the future, i'll run my mouth / stir things up and you do the final presentation, okay ?? : )
Honestly though, the fact that you typically remain a "third party" in many of these posts and then summarize both points of view expressed sometimes helps me to see things more logically. There have been many times that you and a few others have added to the thread in such a manner that makes us think about the "big picture" and not just the subjects that we've gotten emotionally tied up in discussing in that thread. For that, i am grateful for your input and everyone else that contributes their thoughts. Even if they disagree with my thoughts : )
If anyone didn't follow what Joe was getting at, it looks like "high end" is following a logical progression. Some that never ventured into or just dabbled in a specific part of the "sonic stream" would actually call it "de-evolution" or "moving backwards".
If we think about things logically, most folks traded their warmer and more liquid sounding vinyl rigs as the primary source for more convenient digital based systems. Digital sounded like hell, but we somewhat got used to it over time. In most every case, digital was hard, bright, lean, lacked "PRAT" and was "soul-less" sounding, so in many systems over a gradual period of time, more and more tubes were introduced into the equation. This was done to try and make things both more listenable and "musical" again.
Given the added warmth and natural tendency to soften the treble response, this worked out pretty well. Only problem is, unless you have some of the best and most expensive tube gear available, tubes typically lack power output and current capacity. A such, the end users that didn't have "mega-dollar" / "built like a tank" tube gear ended up with bass was not what they were used to hearing.
To counter the shift in products being used, the manufacturers shifted from speakers that required a good amount of power with a more linear response to those that required less drive. While shifting to more sensitive i.e. "vented" designs, they also found that it was easy to artificially inflate the last few octaves of output. By doing so, the end users now had more bass, albeit all the time with less control, but their amps didn't have to work as hard to deliver low frequency output and current. This is because the speakers were already "hyped" in that region AND sensitivity is up. It was a "win/win" situation for those users that had systems that weren't balanced in operation and manufacturers / retailers that wanted to sell products.
The end result is that tonal balance was returned to sounding "warm & musical", even with using a digital source, but such results were achieved by introducing TONS of errors along the way. One "solution" created other problems that required further "solutions".
Same goes for those that stuck with digital and didn't use tubes. In many cases, they were using SS gear that was high in negative feedback, lacked both bandwidth and high current capacity and sounded "sterile" i.e. lean and hard. By adding quite a bit of measurable bass "weight" with the "new breed" of "audiophile approved" speakers, one didn't tend to notice how bright and piercing the treble was. Manufacturers were able to "kill two birds with one stone" i.e. both tube fans and those using lower grade SS electronics were satisfied.
As such, it would appear that the "high end" industry, their marketing departments and the "paid for by advertising" audio magazines aren't about "accurate musicality" at all. They are about selling complimentary colourations / sonic band-aids and telling you that they are accurate / sound "wonderful". Those that know how to read and interpret spec's know what is going on, but since the mass majority of user's don't know how to do this, the "audio guru's" were and still are "safe". Given the fact that we've been led down the path where "all amps sound the same" and "digital is perfect", most "critical" audio magazines have dropped test procedures and now rely stricly on subjective opinions. Those that can read spec's and interpret data on their own have been further alienated from finding out the "truth" and become disheartened with the industry as a whole.
As a side note, as much as i "bad-mouth" Stereophile, i still LOVE the fact that they provide some type of test bench measurements. Having said that, i still can't understand how someone could listen to a product and NOT know what they are hearing?!?! If all of this were not true, how could you explain someone ( end users & reviewers alike ) NOT noticing that a speaker has phenomenally bloated bass? To them, it doesn't sound "bloated" or out of place. This is probably because they've never heard a "linear" system with "accurate" tonal balance to begin with.
How could such a thing have happened? That's easy. They never had good vinyl rigs / proper phono stages "way back when" and were raised on "perfect sound forever". It's also possible that over the years, they've lost perspective due to lack of familiarity i.e. non-use of a good vinyl system. Obviously, this could skew one's perspective quite a bit.
As such, it seems like the culprit for all of our "troubles" and "major design changes" in the audio industry boils down to the introduction of sonically inferior digital technology some 20+ years ago. The audio industry and end users had to shift gears at that point in time, and looking back now, it would appear that it hasn't been a very smooth transition.
With all of that in mind, if you doubt that "digital is the devil" behind all of this, just ask Albert or Twl. They'll give you the low-down : ) Sean
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PS... If you like what you're listening to, that is what counts. As i've said before, "buy what you like as you are the only one listening to it". Saying and getting someone else to believe that is is "accurate" or "linear in reproduction" may be another story though. |
Ernie said: "Your posts are voluminous and helpful in reciting the liturgy, but in so doing sometimes mask objectivity. We know what we hear...and how it measured."
I guess that this is why "audio" will remain subjective forever. I know what i hear and know what i like. I'm sure that everyone else does too. The fact that what constitutes "poor sound" to me typically measures as such while others enjoy that sound makes the purchase of gear a personal decision, regardless of the facts involved. Knowing this, that's why i've stated many times over "buy what you like as you are the only one listening to it".
As a side note, there is gear that i like / is enjoyable to listen to even though it is highly "flavoured". Then again, i also realize this and would never consider such a presentation to be "accurate". Such a system would probably be owned and operated by a "music lover" more-so than an "audiophile". I don't think that either "label" is derogatory, they just signify different goals and listening preferences.
My comments were aimed at those that are interested in the "high end" reproduction of musical recordings i.e. those that seek both accuracy with musicality. Musicality by itself has many enjoyable flavours, but is only half the picture. If that is what someone prefers, so be it. I'm not here to tell them that they are wrong, i'm simply posting observations, comparing data and sharing a point of view. The fact that various points of view end up in debate is nothing new and is part of human nature.
I think that many folks have found themselves in one camp or the other, not by their own doing or ears, but by misguided suggestions from the press and marketing hype. Introducing facts into the equation may initially confuse and upset them, but in the long run, i was trying to help them become more informed and capable of making better long term decisions. After all, the more that you know about a subject, the more likely you are to be happy with the choices you make. Sean
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Firebat: I'm not real familiar with these speakers, so i'll refrain from putting my foot in my mouth. At least on this occassion : ) Sean
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