The first thing I would do is try to get a hold of KEF and see if they would be kind enough to send you a crossover schemetic, you never know what ideas you may get. Next I would go to audioasylum.com and visit the "tweaks" section and ask this same question there. There are a lot more DIY guys over there with a lot more experience. How ever if you are able to get schemetics then it should be fairly simple to make it happen. A lot of folks don't like modifying equipment because they assume that the manufacturer 'tuned' it when they designed it, but they also built it with in a certain price bracket and an easy way to trim some cost off the product is to use cheaper parts of the same value. I think you may be on the right track, just ask around a bit more and see if anyone else has done what you are trying to do.
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Tireguy, thanks for the reply. I know the KEFs have matched drivers and crossovers. I might at the minimum replace the push button connectors with quality binding post and the wire that goes from the board the the new binding posts. So far I am very happy with the sound (after all, KEF supplied most of the drivers for the Rogers and Spendor BBC monitors). I might try to make me a board adhearing to the factory schematic (and bypassing the overload protection circuit). This way I can simply keep the stock xovers intact and be able to put the KEFs back to how they cam. I'll check out audioasylum.com's tweaks section.
I lean pretty strongly towards--don't mess with it, if it isn't broken. Cross-overs are voiced for the speakers. In most cases, even with improved parts and wires, you will usually take 1 step forward and 3 steps back. I could go into examples--but everyone is different. Suffice to say, that even a simple wire upgrade in a speaker can actually give you much worse results because the crossover was voiced for the wire used and thus an "upgrade" causes a loss of "magic". If you do decide to experiment--save the old parts--and label where they go. Also--I don't necessarily feel this way about amps and other electronics because the do not have the "voicing" so to speak. Speakers are a transducer and thus the synergistic nature of the cross over and drivers (and wiring) can not be broken down into confined specifications of what is supposed to do without the other. In electronics--such as amplifiers--the power supply (or other subassemblies) can be broken down into specifications for ripple, noise, etc--which can be independently improved by better parts--i.e. capacitors etc.
I totally agree with Rives. It is very difficult, almost impossible to change crossover parts and maintain the speakers voice. You might get improvement in one area only to make the speaker un listenable overall.
I post this from experience, having rebuilt the crossovers on three high quality speaker systems with the Snell Type A being the biggest disaster.
The Snell I "ruined" simply had the wire replaced and swapped caps with EXACTLY same value, but better quality. The sound was so shrill they had to be returned to the factory to be restored to stock. Luckily this was many years ago when Peter Snell was still alive, so he bailed me out. (Bless him!) he was a wonderful person and a good friend.
Many of the "problems" that one runs into when modifying speakers are that the "high grade" replacement caps are not oriented with the proper "polarity". While some will question the validity of a comment that states that non-polarized caps can be installed with the incorrect polarity, please read on.
Caps have an inner winding and and outer winding. As such, one can orient two caps, which look the same and have the printing facing the same way, in the opposite directions within identical circuits. The end result is a fuzzy mess with a lack of focus and cohesiveness. Another common side-effect is blurring of imagery and an increase in harshness. As such, one should go to the trouble of "polarizing" the caps so that they all share common directionality prior to installation. Bare in mind that, just because the labels / printing on the caps are all facing the same direction, the caps may not share common polarities / connections inside the cases. There is a trick to finding the correct polarity and once you do this, you will instantly know what i am talking about. One can see the differences in polarity on a scope once you learn the "trick".
Once this is done, you will find that having all of the caps polarized in one direction will sound different than if you reverse the polarity of all of the caps within the circuit. In such instances, there is no right and wrong, so choose which orientation sounds best to you.
On top of that, caps used within speakers can take a long time to fully break in. Due to the very dynamic ( read this as being "sporadic" or "non-steady state" ) signals that are applied to them, the caps don't really "form" like those that are used in power supplies or line level signals that are relatively constant. As such, one can "form" the capacitors prior to putting them into a circuit using a signal generator of high amplitude and speed the process up drastically. Once you've done this, the differences in "sonic polarity" with the cap facing one way in the circuit and reversed will become more evident also.
Besides all of this, every wire and resistor will impose their sonic signature into the circuit. As such, it is best to use wires that you already know sound good with those speakers and to keep the legs of any component ) cap, resistor, etc... ) as short as possible and make a good mechanical connection prior to applying solder. In other words, the connection should be solid prior to applying the "electrical glue" aka solder. This helps to minimize the influence / sonic characteristics of the solder. If you don't do this, the solder becomes the conductor rather than the actual leads on the components.
Other than that, each product is built to a price point and most engineers / designers have their own likings. If you like a product and it was truly designed to be as neutral as possible, adding passive components that are even more "transparent" by nature will only improve the product ( if done correctly ). Otherwise, taking a product that has a "built in flavour" aka "colouration" and trying to hot-rod it can end up in something VERY different. Whether or not it is an improvement is up to you as an individual and how much you liked that specific colouration. Sean
That's where I wouldn't mess up at all. There are a particular values placed and zillion times tested for a particular optimal crossover point.
All you might do is just ruin it to the different parameters and don't try to force yourself that your speakers sound much better after crossover mods(I know that many 'phools do) cause they simply won't.
You can experiment with electronic crossovers and bi-amplification doing much less harm and knowing that you're not wasting money for parts.
Very interesting - as I posted in a recent thread, I had to have an under-spec'ed resistor that went bad "upgraded" on one of my Thiel 2.2's by the factory, whose tech stated that this particular resistor (at 1/4 watt) had caused many previous problems on this model. He just threw what he happened to have lying around (of the same ohm rating) in there instead - a 5 watt resistor of a clearly different type, and also gave me another one to install in my good speaker as a preemptive measure (he admitted that this wattage rating was actually overkill). I haven't done that yet, and this thread gives me pause. Maybe I should call back down to Thiel and see if I can speak to the head honcho himself by way of doing a little more research before breaking out the soldering iron. My one reassuring indicator so far - since I haven't yet re-broken in the fixed speaker, which also required two new drivers - is that the tech performed a quality-assurance anechoic test on the repaired speaker, and said it measured better (by which he presumably meant flatter, or within a tighter tolerance) than most examples of the model.
After reading these replies, I think that I will leave my crossovers alone. Sean and Rives have convincing arguments ( I've heard in the past about "breaking in" the caps and talk about the system aproach to crossover tuning ). I was just wondering if I was one of the few that had tried components upgrades with some NEGATIVE results. Thanks Albertporter for sharing your Snell experience (at least you got the Snells back to how they were). I will simply be happy with my current sound.
If you still want to try some upgrade here's two that don't involve changing crossover parts:
Put Bybee purifiers in line with the positive connection
to each driver.
Buy some sheets of Orca Black Hole Five(25" x 27"), cut
some piece to fit the inside walls of your speaker cabinets
peel & stick. Keep it free from the back of drivers and don't block the flow to any ports.
Outside of crossover tweaks, I will also add that if the drivers in your speakers make use of stamped baskets, damping them can make a HUGE difference. This is especially apparent in the upper bass / mids / lower treble as that is where the baskets tend to ring once excited. Cast baskets will benefit from this trick also, but not as much.
If you want to see if this "trick" will help you, pull a woofer or midrange driver from your speaker. Obviously, pay attention to how it came out, what was connected where, etc... Once you have the driver out, hold it by the magnet structure without touching any part of the driver. Now take your finger and "flick" the basket near the mounting flange. If it sounds like a bell and rings, you are hearing a source of colouration that IS apparent when listening. While it is true that the speaker is mounted and the ringing is reduced due to mass coupling, the resonance has simply been altered in amplitude and frequency. What you are trying to achieve is a basket / mounting structure that does not contribute to the output of the speaker once excited.
I was shown a trick by an industry professional that works like gangbusters for this situation. What he recommended was taking a tube of "Liquid Nails" and filling in the gap between the front plate of the magnet assembly and the rear of the basket. Depending on the driver in question, this can take quite a bit of "Liquid Nails", but the benefits are VERY obvious once you've done this. This approach drastically deadens the basket without impeding air-flow in or out of the driver. One can go further and coat the entire basket of the driver with liquid nails, but if doing so, you have to make sure that you don't get any on the driver, block air passages or interfere with how the driver is mounted.
My personal experience with this is that filling the gap between the motor assembly ( magnet ) and rear of the basket works GREAT and produces a frame that is FAR less resonant. Since you are filling in a "gap" that already has a form to it, you can simply pressure feed the Liquid Nails into the crevice and it takes care of itself. You'll know when to stop when the crevice is full.
As to coating the entire basket of the driver ( except for the mounting lip and area right behind it ), this can be trickier and a lot messier. First of all, it is hard to apply an even coat of material to the entire basket. Secondly, you'll probably end up trying to smooth it out by hand and end up making a big, very sticky, mess. My suggestion is to wear some latex gloves if you want to try this approach.
What i've found to work best is to fill in the crevice between the basket and the magnet with Liquid Nails and then to apply damping sheets that you can cut to fit the rest of the basket. While these sheets come with their own adhesive already attached, i've found that applying a very few dabs / thin layer of liquid nails to help keep the sheets in place works best. Obviously, if the basket of the driver uses very thin rails without enough area to attach damping sheets, you may be stuck with just using the Liquid Nails. Either way, something is better than nothing.
Using the Liquid Nails / damping sheet approach can result in a driver that is dead, dead, dead !!! The only sound being contributed to what you hear is coming out of the active cone area of the driver itself now. All of the other sympathetic resonances have been removed from the drivers themselves. In effect, you've tried to remove any outside influences from the sound just as a good quality manufacturer tries to minimize cabinet vibration from contributing its' own sonic signature to what you hear. The reason that most manufacturers don't do this is that it is very time consuming. As we all know, time equals money, especially if trying to mass produce a product.
Once you've learned to "tweak" using what i like to call "the total approach" concept, you'll find that your equipment is far more revealing and transparent. Whether or not you like the end results will depend on how much you like neutral sound and how high of quality the design was to begin with. This is not to say that your equipment will be more to your liking. It is possible that the "ringing" or "colouration" that the basket was adding may have been part of the "voice" of the speaker that you were used to. Removing this characteristic from the speaker may not be to your liking, BUT, the sound that you now hear is more representative of what the speaker system is truly capable of providing under optimum conditions. Sean
Agree...the added sonic benefits...if any...of crossover modding are not worth the effort...most of the R&D in hi-end speakers is performing listening tests on various crossover networks for a particular design...so what might seem simple in the end...is often years of research...I wouldnt try to "outsmart" the initial designers...they use specific parts and orders for a reason...and monkeying also hurts resale value if u want to upgrade...
Sean your suggestion about damping is a good one, could not hurt the driver and would remove some of the unwanted resonances.
Richard Vandersteen experimented with this many years ago and developed driver frames and baskets (computer aided) that reduce not only resonance, but reflections as well.
I've heard both versions and the results are astounding. Do it yourself members could follow your lead and get a nice improvement with almost no investment.
Sean, nice damping mod. I have used "Dyanmat" in the past (mostly automotive applications). I don't know why it never occured to me trying the stuff on mids / woofer baskets. Years ago I experimented with Altec Voice of the Theater speakers and remember adding foam insulation on the back of the horns to reduce ringing...and it helped. I think I'll try it.
One Audiophile: While Dynamat works, it is cost prohibitive to use in big quantities. Technically, while the Dynamat may work "better" in an all out effort as compared to the Asphalt or Vinyl based sheets i linked to above when used all by themselves, in all reality, there really isn't a noticeable difference in actual use. Combining the "Liquid Nails" and "generic" damping sheets approach that i listed above really does offer a HUGE bang for the buck.
As far as horns / horn bodies go, let's just say the differences between damped / undamped are pretty amazing : )
When using "foam insulation", did you use something along the lines of "Great Stuff" ( aka "foam in a can" ) or was it something different ? I've tried using that before but it was WAY too cumbersome to work with on drivers / horn bodies.
The one place that i did find it to work well was on the inside of folded bass horns in the corners. In order to minimize internal standing waves, i like to radius the corners in these designs. I do this by taking a sheet of paneling and bowing it out so that there is a gentle curve rather than a dead-end corner. Once you get the paneling tacked in place, you can fill in the gap between the cabinet and the radius created by the paneling with "Great Stuff", heavily packed fiberglass or something similar. The idea is to deaden the cabinet and offer some form of support for the paneling so that it does not contribute its' own resonance to the sound. This is another trick that can make a world of difference as it really cleans up upper bass / lower mids on such a design. Once again though, this is a very time consuming project that would kill a manufacturer if trying to mass produce a product. It can be done simpler than what i mentioned, but like anything else, the results are not quite as good using a "short-cut" approach either. Sean
Why don't you get a Outboard Active Crossover network so you can adjust the points and give you the capability of Vertical amping which will go a long way in performance.
The Pro's are doing alot of this now and it's what I am going to do.
There are many advantages.Do a search of Vertical Amping to see what the advantages are.
Unsound, Liquid Nails is a brand name, and implies that it holds like steel nails do, but it's simply a thick liquid glue. Reminds me a bit of Weldwood contact cement the way it sticks (and smells), but it can be applied much like GE Silicone from the pointy dispenser tube.
It comes in a "small projects" tube, about the size of a tube of toothpaste, and in large cylinders the size of painters caulk. Inexpensive and typically available at Home Depot.
Rope caulk also works well to damp driver baskets and is easily removed if you don't like the results.
I've replaced the resistors in my Dunlavy SC-III's with Mills wirewounds and the Solen capacitors with Auricaps (all but one large 62 uF). I've been very pleased with the results and haven't noticed any change in the "voicing", only a very noticable increase in clarity and detail.
I'm a big believer in crossover upgrading. If you try it and don't like the results you can always return to the factory configuration.
I actually have heard of and have used a similar approach to speaker basket ringing that Sean was telling about with the "Liquid Nails". Basically the only difference is to use
"non-hardening" childrens modeling clay. In 10 years time it still has been effective. One of the positive things about this is that it can be removed fairly easily. Another
positive change especially in the mid/lower bass that can be realized in some speakers is the removal of any poly-fil type dampening materials and replace with quality combed/fluffed real wool. I did quite a bit of experimenting on this, and I have nothing to back me up, except that I liked the bass/kick/thumps much better. Sounded much more "natural".
Pelv: Is this Elvis P in disguise ??? : )
Long fiber wool is the best for internal damping followed by fiberglass with everything else a distant third. Altering the quantity and density of damping material will alter tonal balance and attack characteristics. Increased quantity / density will enhance low frequency extension with a decrease in mid-bass output while a reduction will increase mid-bass output at the expense of low frequency extension. One can fine-tune the quantity to adjust for room acoustics and / or personal tastes.
As far as using modeling clay, i would be afraid of vibrating it off of the baskets over time. Sounds like a "quick & dirty" approach that may be worth checking out though. After all, if you've gotten ten years out of the clay with nary a problem, it sounds like it could offer the best of both worlds i.e. extreme mass with complete reversibility with minimal mess during application.
Capaudio: Reliable sources tell me that Audience Auricaps have been bettered by Moncrieff's latest caps, the "TRT Dynamicap's". The Audience caps are supposedly VERY good though.
For those interested in such things, a phenomenally well put together source for finding specific types / brands of caps was put together and can be found here on the Faradnet website that is free of charge. One can look up caps by dielectric material, manufacturer, etc... Very handy website if looking for "tweaky" caps, etc... Sean
The TRT Dynamicaps are very, very sensitive to heat. Too much and you change the sound(actually not all that much heat) Also, it is very easy to break the soldered leads of the caps. I have resorted to heat sinking the caps leads so as not to damage them.
As for which is better, the Dynamicap or the Auricap, I find I personally like the sound of the Auricap. In filter use, it seems to impart nothing to the sound as the Dynamicap seems to add a minute touch of grain IMO. I also feel the Auricap is a little better built in absolute terms.