Quad Drivers (ooooh =p )

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Ok, just hear me out first - it's my first time (on the board/building home audio components/etc). As with everything, I might have gone overboard and I'm planning on constructing a quad driver powered sub enclosure. First of all, would four (10"ers) really be too many, I haven't seen anything like it yet, so I'm thinking maybe there's a reason - dropping down to eights would be fine with me if<sigh>. (If not, then proceed to Q #2!)
I don't plan on building a simple sealed enclusure, as I hear they (for lack of a better word) suck, and provide limited frequency response; naturally a 'vented' enclosure would be better, right? But there are so many kinds..ACH! From what I've read so far, 4th and 6th order bandpass variations offer better response for less power, but the tradeoff is that they blow easily (easier?) because of the compression in the box. If I'm planning on 4 drivers (someone tell me if I should scale back to two..though I'd rather overkill =p ) would the compression just tear the speakers apart? Finally, what's the difference between actual home audio subs and car audio subs - if I'm strapped for cash could I use car audio in place of specific home audio units (or could someone direct me to discount driver). Ok, I hope that made sense to everyone, and responses would be appreciated - construction starts tomorrow ;)

(Would it be too much to ask for both power AND response throughout the spectrum - a tradeoff between the two would be nice, but I'd lean towards sacrificing brute power for sound quality if I had to)
well actually the very best tightest most accurate of bass comes from a sealed enclosure....

4 drivers wont be a problem but they should be mounted to form a square this will form what is effectively 1 driver with a Sd equal to 4 times that of a single driver, a Vd 4 times that of a single driver (cause Vd = Sd x Xmax and only Sd changes), Fs equal to that of a single driver, power handling 4 times that of a single driver and an efficiency 6dB greater than a single driver.

Also the baffle should be square and large to minimise the diffraction loss.

If you go sealed you'll need active equalisation but that aint too hard.

btw. @ least 2 ppl on this board have subs that make this look like a baby.
Hey Bryan,

Didnt anyone ever tell you it is dangerous to your health to operate a sub below 10Hz....... between 2-4Hz the resonant frequency of the human body is reached and well the rest ... well the rest lets just say it aint pretty!!!

@ 6-8Hz internal bleeding can be caused
@below 10Hz most people suffer nausea
Mine are mounted six vertically per side, ala line source, although at those wavelengths (xover @ 70Hz currently) it's not technically a line source.
Each driver (sorry, twelve 12" drivers, forgot to specify) is internally separated into its own T-S enclosure. Each cabinet is a bit over 7' tall. They're good down to mid to upper twenties at present, but I'm (slowly...glacially) headed towards a servo system with dedicated amps for each driver. I'm used to a sub that will go into the teens and I miss that last octave, although the current rig will produce more SPL, and is much, much tighter than its predecessor, which went deeper, but exceeded Xmax at even moderate volumes.
Four 10"? Only??? Surely you mean per channel...please tell me you mean to use a pair of these...please?
Seriously though, tens will be somewhat lighter and faster, but you won't have the surface area that larger drivers could give you. The usual give-some, get-some set of tradeoffs. Do what suits you, and what you can afford.
Go for it. There's plenty of room for new (ahem...junior...ahem, ahem) members in the Excessive Sub Club.

diyAudio Moderator Emeritus
Joined 2001

Bass is about moving air. Whether the enclosure is vented or sealed has a lot to do with it, too. But all other things being equal, the speaker that moves more air will produce bass at a higher SPL.

The air moving capacity of a speaker is the area of the cone times the distance it is able to move (cone excursion). So again, all other things being equal, the speaker with the larger cone will produce more bass.

Two 10' speakers have the same cone area as one 15" speaker, and will produce the same amount of bass if the cone excursions are equal.

Four 10" speakers will produce the same amount of bass as two 15" speakers, so your design is NOT excessive by any means. It sure ain't puny either, but you can't call it excessive.
When the 12 Shiva IB was constructed, there weren't any Tempests or DVC 15's in existance.

There is some cancellation between the lower and upper woofers as a result of the separation between them. However it doesn't pose any real problem with regard to performance....

If I was doing it now I'd probably get 4-15"s and put them in a square.
I know what you mean by going overboard at first. But if you do your homework before building then you'll do fine. I went with 4 15", in my main left & right speakers, didn't want to build a seperate sub, wanted main speakers that'd go that low. I'd go with a vented enclosure, working out the port diameter and length is really easy. As for you wanting power, believe me whatever enclosure you make, you'll have enough power. I wanted alot of power for my system, until I realised how loud it plays at relatively low power levels.
You want excessive? How about an 18" or 24" crossed over at about 20-30Hz as a sub-sub? I've run across people doing things like that now and again. I believe an earlier version of the Wilson WAMM used an 18" below 40-50Hz or so. I don't know what the current version uses. The Wisdom Audio folks are using 18" back-to-back in each end of a round enclosure (you listening, Bryan?), but I don't know the crossover point. Guess I need to do some web surfing and see what the commercial folks are up to these days.
(If I'm not careful, I'll talk myself into another project, here...)
Incidentally, the twelve 12" w/servo loop thing has been done for years; I didn't think it up. Arnie Nudell did it for the IRS back when he was at Infinity, and uses the same strategy now at Genesis. I've heard both the IRS and the Genesis Model 1s...and though I have reservations about some aspects of both speakers' reproduction, the low end in both was exemplary.

Please, Grey, you know how much I'd love to play with the new Aura 18 inchers, but I haven't the space nor money nor self control to apply any sense of reason into a project like that...

As for that Wisdom Audio sub, I haven't seen it mentioned anywhere. If you can dig up a link or a pic, let me at it. I'd be interested, considering the only other dual 18 inch offering I've ever seen was the Wilson XS.
Thanks, guys

Thanks, all for the feedback =p I'm really just 'testing the water' right now to see if this is something I'd actually like to get into - so far so good. Box construction is coming along nice, but I have a few (more) questions about that.

I'm using high density particle board, but what should I use to adhere the pieces together - would wood glue be acceptable, or screws and rubber gaskets...caulk? I'm using a 4th order bandpass (or trying to) with 4 8" drivers and am desperatly searching for a way to power them all, so if anyone has a link to a decent transformer layout (RMS will average around 500 watts, or should at least) it'd be greatly appreciated, as well as input boards (I don't know what else I'd call 'em, sorry..) and associated stuff for making a powered unit.

Again, thanks for the response so far
diyAudio Moderator Emeritus
Joined 2001

Your quote: "I'm using a 4th order bandpass (or trying to) with 4 8" drivers and am desperatly searching for a way to power them all, so if anyone has a link to a decent transformer layout....".

Why do you need a transformer? Hook them up in series or parallel if you are using two channels. If you use one channel, two pairs of series connected speakers will yield the original impedance when the pairs are hooked in parallel to each other.
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