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

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
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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.
Best,
Larry

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.

Regards,
John

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! :-)

Dawg,
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.
Best,
Larry