Side firing bass designs - Pros & Cons?...

In an earlier "Adiogoner" thread someone asked if anyone had heard speakers from Amphion. I quickly went to their web site to see their speakers and noticed on the Xenon model they incorporated a side firing bass design. Based on the little bit of knowledge I've picked up from more knowledgeable audiophiles it seems to me this set-up would create time and phase coherency issues not to mention sending sound waves away from the listener instead of toward them.

Are there advantages in this type of design I don't know about, because Amphion isn't the only manufacture employing this side firing woofer strategy(Israel Blum uses it)? What are the pros and cons?
The pros are a narrower front baffle, for better imaging, like a mini-monitor. The cons are they require a little more care in setting up. If the woofers fire into the wall they can overpower the sound. Many manufacturers are going this direction now. Audio Physics, Canton and my Vienna Acoustics to name a few. They try to better blend a monitor/subwoofer in one cabinet. The days with all front firing drivers in a rectangular box seem to be dwindling. Even speakers that have all forward firing drivers tend to not be rectangular, going with a form of pyramid shape. The main goal is to make the front baffle as small as possible to eliminate early reflections that can muffle the sound a tad. My Strauss' have 10" side-firing woofers crossed over at 70 hz. So they are basically subwoofers, and low frequency is not directional, meaning humans cannot detect where the sound is coming from. That is why subwoofer placement isn't as critical as speaker placement. I have my woofers facing in. I've found that when facing out they had too much wall reflection and the bass was a little overpowering and slow. It is tighter and quicker when firing in, IMHO. My previous speakers had 10 forward firing woofers and a wider front baffle (12" compared to 7.7" wide)than my current ones. My current speakers image better, meaning I can locate instruments within the soundstage better than with the other ones. They almost image as well as the best small monitors, but with much better bass. I hope this was somewhat helpful.

If memory serves, frequencies below 200 Hz tend to be perceived as non-directional -- you can't tell where they are coming from. John is correct that a smaller front baffle leads to improved imaging, but some manufacturers compensate for that by utilizing material that absorbs high frequencies, like felt, on the surface of the baffle combined with rounded baffle edges to reduce reflections. If you are a time and phase coherence proponent, I would think it would be harder to design that into a side firing speaker. While you may not be able to tell the source of the low bass, it may take a lucky confluence of factors (e.g., room acoustics and layout) to compensate for the reliance on reflected sound. From my experience with Def Techs, that design could also lead to some problems with a smooth transitioning from mid bass to low bass. You're wise to suggest there are pros and cons -- there are with all speakers.
Using one woofer or multiple woofers on one of the sides of a cabinet can make placement very difficult. Using a woofer on opposing sides of the cabinet makes placement LESS difficult. This is because each driver excites the room in a different manner and direction, causing a more even overall response rather than just one major point of excitation in one direction.

If one has the computer download speed capabilities, i would suggest downloading and reading the owner's manual for the AR 9's found at this link. Be forewarned, it is a 53 page PDF file. As such, it will take a bit of time to download. Having said that, it is worthwhile as they provide several pages of charts comparing various speaker placements using their side firing design against more conventional front firing designs. Obviously, this was used as marketing material and should be taken with a grain of salt, but one can learn from some of the info presented in this manual. Sean

click to download 53 page AR 9 pdf file

PS... When is the last time you saw a 53 page owner's manual for a speaker ???
I agree with the placement difficulties, I had a pair of Definitive Technology 2004Tls with the side firing subwoofer... it was hard to get the room to really fill.

I think they figure that since under 100hz is non-directional, they can place the woofer on the side and make the speaker slicker and sexier and easier to get by the WAF, which would give them an edge on sales...

I think a pair of monitors and a good subwoofer works better than towers with a side firing woofer. cause that is basically what you are getting, is a monitor on top of a subwoofer.

At least that has been my experience.
Just get Vandersteen model 5 or 5A's and forget about it!

Sean -

Thanks for posting the AR 9 owner's manual link! Great info in the room acoustics section. Methinks the folks at AR tore a page from the back of Roy Allison's notebook.

Another speaker that used a room-boundary-conscious woofer system design was the Snell Type A.

Back in '86 I built a pair of speakers using a 30" tall Gold Ribbon Concepts planar driver and a pair of 7" Focal woofers. To keep the front baffle area to a minimum, I mounted the drivers on the side. It was kinda cool looking - from the front, all you saw were the ribbons. The woofers were physically about 1/6 wavelength farther away than the ribbons at the 200 Hz crossover point, which was negligible. Both the woofers and the ribbon were loaded into transmission lines. If by any chance you have the 4/86 issue of SpeakerBuilder magazine, you can see a picture of it. In retrospect there were some radiation pattern discontinuities that I wouldn't tolerate today, but at the time I didn't know any better. Still, they didn't suck too bad.

Duke: Roy Allison used to work for AR, hence the similarities in design. For that matter, so did Ken Kantor, who designed / helped design some of the NHT stuff. From what i understand, the woofers used in the 9's were made by the same company that makes the NHT 1259 woofer. Both drivers work best in big, low Q sealed boxes, which is what i like anyhow : )

Slappy: Bass doesn't become "non-directional" until pretty low. I think that even at 100 Hz, one can still pretty well "localize" the point of origin without much fuss if they know how to listen. This probably has a lot to do with the harmonics that the driver is radiating and the distortion too. Sean
Sean is right, you need to get very low in crossover point before it becomes impossible to localize it. Even a nominal crossover point of 100 Hz will still produce audible sound at several hundred Hz due to the crossover slope, and this is very easy to localize. Most full-range systems with side-firing woofers are crossed over at or above 100Hz, in some cases well above.
yeah, i agree that you can still tell where 100hz is coming from, but its not as easy to tell. I thought that 100 was where it was supposed to become non-directional
or is it that around 100 hz it starts to take non-directional characteristcs and the lower you go the harder it is to place?

either way, i think the side firing woofer is still a marketing ploy for audiophiles to get bigger spekers to pass the WAF, hence being able to sell larger models.

I mean, check out a set of those Vienna Accoustic Mahlers, those things are slick, they would fit in almost anywhere and are very non imposing for such a massive speaker.

then take a Vandersteen 3A, Big, bulky, darth-vader-esque, and rather difficult when considering the WAF.

It would be alot easier to get the Mahlers in the family room than the vandersteens.

heck, the mahlers almost look like pieces of artwork rather than a speaker
The Vienna Acoustics speakers are VERY placement sensitive from what i remember. Can't remember the model that i tinkered with, but it was a big floorstander with woofers on the side. The bass reminded me of Legacy's, which is to say, loose, flabby and lacking in definition. My Dad really loved them. Then again, he already owns Legacy's. I'm working on that though : ) Sean
Interesting perspectives here. My perspective is similar, with a couple of exceptions.
I have quantified a type of speaker distortion, which I have listed with my attorney, as a theoretical concept paper, which details a new quantification of distortion unique to dynamic loudspeakers. I have up to this point called it, in its working form ADD, or Air Displacement Distortion.
Let me explain.
In creating sound, all dynamic, and electrostatic, to a much lesser degree, but for the sake of comparison punch the air in the direction of the listener. I first noticed the great differences that the Pipedreams had, in presenting bass, with much less apparent (to me) distortion in the deeper bass than many other speakers which have good bass reproduction and bass extention. Their woofers are vertically loaded for those who are not familiar.
In working on a model, I started to experiment by switching from one speaker to another, comparing this displacement differential, since the Pipedreams subs, again, point vertically, and are not punching air in the exact direction of the listener. All the other speakers, of note, in replicating bass tones of say an upright,double bass, accoustic, seem to have an accompanying 'sound' which is not part of what I hear when I hear that instrument; so I concluded that the throw of the woofers (distance they move from their rest position) in the front firing woofers created an apparent air displacement, sound, unique to, and constant with this presentation, whereas the Pipes did not. That led to other comparisons, all of which took hours on end. I have concluded several things, too lengthy to list here, but they are, in essence, and in capsule this:
Electrostats, sound smoother, (albiet obviously less dynamic) since they don't punch the air, therefore, creating this amusical driver air displacement 'sound'. They move the air more like (I am supposing) their real accoustic counterparts, i.e. instruments. Even a concert bass drum is displacing air to the sides, when struck. So rarely is the air 'assulted with such force, than in the bass, and with large front firing woofers.
When we discuss phase coherence, and such, we have to consider that the drum is naturally coherent, even though the sound is loaded to the sides in the room, relative to the listener, assuming that he or she is in front. I am going to do more work on this, but some input would be welcome.
I am sure that driver noise, another, similar issue is also part and parcel of the difference that people report hearing in stats, versus dynamic speakers.
Remember, this, as most audio work is not completed, therefore not emperical, but at this stage suppositional again, at this stage of its development. I think back on the Maggies, with limited displacement (relatively), and similar to stats, and horns,(perhaps) and how different, and more lifelike they can sound...sometimes. The Sound Lab Electrostatic has 22 square feet or air pulsing in phase at all frequencies, for example, but moving air a slight amount, but in great volume (not as it relates to loudness, but amount of here). And regardless of individual tastes, most people love their sound, generally reporting it to be less distorted. This is consistant with the Air Displacement Distortion Theory. The SL's sound more polite, and maybe, less accurate, in some ways, dynamically. Thoughts and ideas are interesting here because of the obvious link to my theoretical work.
Also, one final thought, I owned the Mahlers by Vienna Acoustics, and liked their bass, not for the reasons that some do, but because they did not assault the ear the way some front firing woofs do, again, perhaps supporting this theory. I have many more hours to work on this, to finish a white paper theory, but it is interesting to me to contemplate. On the whole, at this time, I think, and am close to concluding something which may be obvious but rarely spoken of, "Driver Noise", which is part of ADD.
Thoughts? Further Ideas? Grant money?
But we should not forget the bottom line, it's our ears that do the listening regardless where we listen. In a recording studio, regardless which direction a drum is pushing air, we listen to the whole band at ONE location where you sit or stand. Recording does the same by placing microphone at some strategic locations to mimic what a listen should hear if we were there.

So speakers with side firing woofer, because of room interaction, will less likely to sound as integrated as other designs.
Lrsky, that's an interesting concept. The way I interpret it, the very act of moving a lot of air in a small space creates distortion -- call it atmospheric friction, but add eddy currents and whirls. By moving air more uniformly over a larger surface area, that distortion goes down and sounds more realistic. It sounds extremely plausible. Well done! (this is but one of many factors in the equation, and introduces more tradeoffs, but it is one more variable for consideration)
The distortion I am quantifying is not anything like the original signal created, therefore is a whole new form of distortion. Just like harmonic distortion, or transient intermodulation distortion, in amps. But this is created by the drivers. Their amusical, and unique sound is audible, which is part of the premise. That "noise" keeps us from hearing the recording independantly. So, if distortion is defined as "any change from the original..." this is fundamental to that.
You know, I personally have always had some issues with the Maggies and the Stats, but there WAS the better parts of their reproduction that were undeniable. Also, horns, which have colorations, but do not smack the air that we can hear like a dynamic that change has SOMETHING which we all have grown accustomed to, and we just filter it out. Sort of like television. Someone made a comment to me that: audio in its own way is much more perfect than video. You can actually close your eyes and listen and imagine that you are there, but nobody ever claims that video could EVER be mistaken for the real thing. Say you put a camera on a part of a scene, and introduced the video signal into the equation, and balanced the color, brightness, and everything perfectly; you still could never, NOT NOTICE. I had to agree with them in principal. ALTHOUGH, that really kind of enforces my point about audio; in that we block out the unreal parts. I further contend that this is part of LISTENER"S FATIGUE. The harder our brain has to work to recreate the real thing (a piano through speakers versus a real piano) the more fatigued we get. This is why sometimes our system sounds poor, and other times it sounds great. We are the X factor, our brain's willingness to 'complete' that incomplete equation, or not complete it. Think back, usually when you are mentally fatigued,sometimes that's when if you try to listen, and get in that perfect groove, wherein you can 'pretend' it's real, but your brain is not willing to do so, you just end up turning it off in frustration.
So, this annoying driver 'noise' is always in evidence, we just have 'learned' to disregard it. Bass, being the most obvious of all, because of the displacement severity, was the first place I really honed in on it.
Thanks for reading.
Lrsky, just about 2 weeks ago I read an article in the news papaer (NY Times or PH Enquirer, can't remember which) which reported on a story concerning a German cable channel that transmitted a signal of a fire that was intended to replicate a fire place. Well, an elderly woman called the fire department claiming that her TV was on fire. When the firemen were interviewed they said that this happens periodoically, and recently an elderly woman threw water on her TV in an attempt to extingush her burning TV. This caused an electical fire that spread to neighboring apartments and the building had to be evacuated. I can only imagine the blazing effect HDTV is going to have! BTW, the fireman suggested that most people should be able to distingusih a real fire from a televised one.
Was any alcohol involved in that story, you know, the nightly nip? HA!
There was no mention of alcohol in the article. I'm glad you got a laugh from it. I know I did. In fact all the international news that day was so depressing prior to that article, I stopped reading that days news, so that I could leave on a humerous note.
Lrsky: Your observations pertaining to distortion are right on the money. A large part of the distortions that we hear are THD, which are comprised of higher frequency harmonics of the orignal signal. Facing the drivers away from our ears "dillutes" the percentage of those higher frequencies that we hear. This causes them to blend in with the other signals being reproduce, minimizing their effects and noticeability.

As a side note, it is the harmonics of a lower frequency signal and the "leakage" through the crossover that allows us to localize low frequency signals. The more effectively that one can minimize the distortions that we hear and the harmonic overtones that the driver generates, the less likely you are to locate the source of bass. Obviously, facing drivers away from you and running a sharp crossover at a very low frequency is about the best that one can do in this respect.

As far as output levels go, if you want low bass at high volumes, you've got to move a LOT of air. While one can do this with a few drivers that can provide huge amounts of excursion, long excursion drivers tend to have their own problems and introduce distortions into the system. The other approach is to use multiple woofers in some type of array. If the array loads the room in multiple directions, you can achieve great bass output while exciting the room nodes in a more natural manner.

As a side note, the mains of my HT system each have a side firing 12" on opposing cabinet walls. The surrounds have side firing 10's arranged the same way. My bedroom system uses down-loaded subs that are currently crossed at 65 Hz and my main system uses four dipolar 12's per side in sealed low Q boxes. My office system radiates in a 360* horizontal pattern from a single driver, so it too loads into the room differently than most "conventional" speakers. The only "normal" speakers that i'm currently running at the time are front loaded horns and event these aren't "direct radiators" so to speak.

I'm also building s system for a friend that uses eight 12" woofers per cabinet. The baffles are as narrow as possible and make use of a very large line array of mid-woofers and tweeters ( power handling, high sensitivity, lower distortion due to reduced excursion and more linear radiation pattern into the distance ). Flanked on each side of the baffle sloping backwards will be four 12's per side in a stuffed but open backed cabinet ( damped open baffle ). I had to look carefully at the electrical characteristics of the woofers to do this, but i think that it will work quite well. Sean
Thanks. It took some time, years, in fact to quantify what is so obvious after we 'notice it'. I am pretty convinced that the distortions are of another order, (hence the idea for the paper)and of more significance, than just harmonic distortion, even though what you say is accurate, (usual for you Sean). When I think of harmonic distortion, it is more easily placed than this, since this has been part of our universal listening experience most of our lives. It's funny, but when some people would go bonkers over Stats, or Maggies, over the years, I wouldn't quite understand the magnitude of their objection to that pervasive distortion that drivers were making. I am pretty sure it is several forms, hence the new name ADD. ADD will be a combination of harmonic, transient intermodulation, and on and on...
When I look back, the people who loved Maggies so much, or Stats, so much, were usually newbies, (this is simply my isolated experience, and first hand retrospective observation, not emperical) who did not embrace universal driver distortions like the rest of us have. They only knew that it sounded more 'right'. From that perspective how can I disagree? The MBL's have much the same allure, as well as the original Heil Air Motion Transformer, which squeezed the air, rather than slam it. (I guess finesse wins again in some reality huh?).
I have a lot of work to do on this, but as I think about it,
I was enamored with, (and still am) the Pipedreams speakers for much the same reason, (forgetting bass here for a minute, and degrees of taste and particular 'audiophile bias') since they have 80 plus drivers moving fractionally the distance of typical speakers. Moving what has to be almost at the sonically invisible, magic point of distance from rest position. Think of the relevance of comments we all hear and use, relative to, "effortless" and "lifelike" that we hear in descriptions of well done multiple driver array systems. This is no colossal accident, but further potential evidence of the validity of this driver motion distortion, which I am working on and have (potentially) quantified.
Thanks Sean, your system that you are working on sounds interesting.
Von Schweikert Audio, and I (don't get me wrong it's Albert's baby, that's for sure)have been talking about a system which employs multiple woofers, in two separate towers, (limiting great excursion distance) with 11 drivers per mid/tweet towers, which hopefully will be released at the CES in Vegas, in Jan., 2004. The same thing as some older systems such as the Original IRS (I think it was Infinity Reference System). But back then, with limitations of crossover excellence and driver technologies, (not a criticism just noting the twenty year gap in time/technologies) it seems that they sounded a little confusing. But to replicate that today, with better drivers, that is exciting to me.
Sean, I feel like I'm your Dad. I lived with several versions of Legacy speakers from 1986-2000. I've since moved on to Vienna Acoustics. FWIW, I thought the Legacy speakers were a great value when I first heard them, in 1986. I think their quality slipped some over the years. The VA's are placement sensitive, you have to keep those side firing woofers away from surfaces that can be reflective, such as walls. When I had the woofer (1 in my Strauss) firing out towards the wall, the bass was slow and muddy, as I mentioned earlier. In my room, they need to be out at least 2.5-3 feet from the rear wall, with the woofers firing inwards. This will allow the rear port to 'breath', and the bass will tighten up quite nicely. In my experiences, you really cannot judge the true sound of the VA's in a Tweeter chain store, they really have no idea how to set them up. They don't use quality equipment either. I've actually seen them have the Mahler's ($10K) being demo'd with the speakers in a corner, being driven by a Denon 70 wpc receiver and a Pioneer dvd player. It sounded horrible. You'd think they'd put a little more effort into trying to sell $10K speakers.

BTW, I do have 3 sons, ages 12-19, one named Shane, but they don't have any interest in my hobby.

Lrsky, in multiple driver speaker designs like the Pipedreams and GR Research Alpha LS how do they take into account line source dispersion patterns? It would seem to me line source changes tone balance with listening distance.

Thanks for all the wonderful input, I knew I could count on you guys! :-)
That, my friend is an excellent question. The Pipedreams use a proprietary 'series/parallel' wiring configuration which ameliorate the lobing effects which is what you are asking about. Otherwise comb filter effects would cause a disturbing cancellation, pattern, which would make them very non linear.
The designer, who I know, won't talk about it in any detail, and I am honor bound to not discuss it more than I have mentioned already.
I hope this is enough to answer, what I consider to be a very good, and intuitive question.
You'll get comb filtering no matter what you do when using multiple driver arrays, but that can minimized by careful design and wiring. I ran across a website that was mentioned on Madisound when doing research on line array's that goes into detail regarding comb filtering, driver size and spacing, crossover frequencies and slopes, etc... I printed it out as it was worth having around. If i can remember correctly, the website was run by a gentleman by the name of James R. Griffin.

While i can't find his specific website, i was able to find one that had his work along with that of a lot of other line array advocates all compiled together as various downloads. At least some of Jim's work can be found here and is titled something to the effect of a "linus array". Sean

Line Array information
I think the key here is, 'minimized'.
Loudspeakers are all imperfect to me, versus real music.
The pipes do some things really well. Mostly micro, macro dynamics because of the drivers redundancy, plus the lack(make that lessening) of the earlier mentioned driver air displacement distortions.
The designer is tight lipped enough on this that he may have come up with the formula to make his filtering less than previously thought possible. Who knows?
They are great, though, in some ways, not all, of course.
Other than the AR 9's, 90's, NHT, Vienna Acoustics and Coincident Technologies, i can't really find any other speakers that made use of side firing woofers. I'm not counting Allison's and DCM Time Windows, as the woofers weren't so much "side firing" as the woofers were not side mounted so much as the cabinets were twisted sideways. Other than that, the only other thing that i can find was that EPI had a speaker that looked quite similar but used dual passive radiators where the 9's and 90's had active radiators. These were driven by one active 10" that was mounted up where the AR's mounted their 8" mid-woofer. If i can recall correctly, i think the EPI was a model 500 and made use of their popular and good sounding inverted dome.

Other than that, there might have been another company out of Europe selling a speaker with side firing woofers. I think i remember seeing some in one of Jerry Raskin's Needle Doctor advertisements, but i'm not certain. I thought i saw something about it using a Hiquphon tweeter, etc... Sean

PS... I'm not including the Fluance ( Flatulence ?? ) speakers as found on Ebay in this list. I have a hard time believing that someone can build and market 4 and 5 driver towers of any quality for well under $300 per pair. Then again, who knows. Maybe these would shock me in regards to what they offer for the money. I kinda doubt it though : )
Sean, check out Israel Blum's side firing designs. He places multiple drivers on the side. Thanks for the line array web site it looks very informative!
Sean, how about Audio Physics?
Some of the Joseph Audio line. In fact, the designer talked about some of the issues with side firing in his Sphile interview.
Dawgbyte: I mentioned the Coincident Technology aka Israel Blume's speakers. Glad you liked that website as i'm sure it is loaded with info.

Jmcgrogan: Thanks for the reminder. I'm sure that there are other speakers out there that i overlooked. I hope nobody feels slighted if i didn't mention the brand that they are running with side firing woofers : ) Sean