# 30" Sub for \$700?

Discussion in 'Home Theater Projects' started by Peter Jessee, May 30, 2005.

1. ### Peter Jessee Stunt Coordinator

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I thought that might get your attention.

I've been daydreaming about a possible project and would like some feedback from Those More Knowledgeable Than I (not a real exclusive group....).

I've been trying to come up with a way to 1.) Build a sub with lots of cone area for good "Slam Factor"; 2.) That's capable of high (>115 dBA @ 2 m) output; 3.) That loads the room properly to avoid "peak and dip" issues; and 4.) Doesn't cost a fortune. Here's what I came up with:

Put four 15" Quatro drivers in a 12 cu ft. sealed box – four 15” cones = area of one 30” cone. The box is almost as tall as the ceiling, say 86” x 22” x 12” deep in a typical 90” tall room. The top and bottom drivers are located so that the center of the cones are exactly 1/4 of the room height from the floor and ceiling. The center two drivers are as close together as possible, centered around the half-way point between the floor and ceiling. Place the box at the exact center of the front wall, (assuming a front projector) or the center of a side wall if it would interfere with the video display.

I think a P.E. 500 watt 300-806 plate amp would run this quite well, with the drivers wired series/parallel to make a 4 ohm load, although the 1000 watt 300-808 would still be within the power handling limit for the total driver load. WinISD shows an output of 106 dBA @ 2 meters for ONE driver and 125 watts, so the combined output should be about 12 dB more, or 118 dBA. Add 3 dB for the 1000 watt amp, if desired. F3 is about 36 Hz, perfect for flat installed response of a Q=0.70 sealed box in a typical largish room.

Four 15" Quatro’s are \$322.00. The 500 watt amp is \$250 right now, allowing \$128 to build the box and still be under the \$700 mark. Shipping is free until Wednesday.

Has anyone tried a woofer array like this? It sure seems like this would be the next best thing to an IB system, without the holes in the wall. You would get huge air movement with small excursions, keeping distortion low. Depth charges and Death-Star explosions should pin you to the couch.

Comments? Criticisms? Reasons why this won’t work? I’m all ears.

Peter

2. ### Brad E Second Unit

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Sounds similar to what I'm building. I'm building a stage/sub to go underneath my pj screen. Sub will be 8'x3'x2', ported. Will be about 36 ft3 after bracing.
I have 2 Atlas 15's that should be here in the next couple of weeks that will be powered by a 350 watt amp.

The reason I decided to do a stage is because I wanted something big, and this seemed like the best place to put it. Rather than having it standing in a corner.

I say go for it, but look first at different drivers. The Quatro isn't really that great of a sub. 2 Atlas 15's would probably give the 4 Quatro's a run for their money and if there are any left (which I doubt, but the website doesn't say otherwise) you could get 3 of them for the price of the 4 Quatro's.

3. ### Peter Jessee Stunt Coordinator

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One of the design criteria was to maximise cone area and reduce necessary stroke for a given SPL, thus four 15" drivers. Even 1000 watts won't drive four Quatro's to their excursion limits in a sealed box this size, and 121 dBA should be more than I (and certainly my wife and neighbors) can deal with. For my purposes I don't think I need a 'better' woofer.

My cousin has a 15" Avalanche driver (unfortunately purchased pre-closeout) and a PE 500 watt amp that will be our next project. The array would be after that, if I can get my wife to approve (or at least not move out). Like you, I doubt there are enough 15" Atlas drivers left, and as I said, I think the Quatro will do the trick.

4. ### ThomasW Cinematographer

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Probably not, the box is too small = the Qtc too high. The best performing portable sealed boxes have a "Q" of 0.5.

Also I hope you're planning on a very low XO point. Given the very high Le of the Quatro, you probably don't want to run it much above 70Hz, and lower would be better.

A properly build box for this project is going to weigh about 400+lbs.

Don't hold your breath for chest crushing bass without more Xmax and power regardless of what the WinISD models say.

Were it me, I'd spend my money on a single high quality driver as opposed to 4 cheap ones.......but hey, that's just me...........

5. ### Bryan Michael Supporting Actor

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i spent the money on 4 18 and all i can say is wo w had to carch my breath. i think if i ever run this up to xmax the wall will come down

6. ### Patrick D Stunt Coordinator

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Since I'm looking at building a box for my own upcoming sub, I was wondering about materials.

I thought I had read that for subs, using regular plywood was acceptable given sufficient bracing, since the resonance of the box was going to be high enough to keep out of the sub's playing range. I see references to baltic birch plywood, but not regular plywood.

Can you use (regular) plywood for sub boxes, to keep the weight down? I'd rather add mass externally (granite tiles and such) so a huge ported cabinet can be moved with something less than a forklift.

7. ### Peter Jessee Stunt Coordinator

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Are you speaking from experience here? Have you used 4 drivers in a room? Have you used the 15" Quatro before? If so, I bow to your experience. If not, I will consider this to be your opinion, and await other, perhaps more informed comments.

A 15" cone moving 5mm will cause the same SPL, whether the driver has a Xmax of 6mm, 16mm or 26mm. Assuming the motor can control the cone within the linear range of operation I'm asking the driver to use, I'm pretty sure I'll get the same performance from a 15" Quatro, 15" DVC or 15" Avalanche. The point of the exercise is to get four times the cone area of a single 15" driver like the Avalanche or Bully for the same price, and see if that has performance advantages. I think it will.

Peter

8. ### lee ison Stunt Coordinator

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right now i'm using 2 quatro's in a 9 cu,ft ported cabinet in a 23x14x9 ft. room with only a 100 watts to each driver and it is more than enough deep,strong bass, i,m getting tired of chasing down all the things tht rattle.I can,t imagine what 4 would sound like, or do to my house&contents.

9. ### John t. Agent

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From what I've read, the Quatro is a pretty good driver. Even though it doesn't have as much xmax, it has very low distortion and it is very controlled (perfect for music), even more than some other 15"rs with a lot more xmax.

I believe you'll be fine with the Quatros. I'm even planning to use one for one of my subs to see how it performs.

10. ### ThomasW Cinematographer

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Please be so kind as to provide a reference to the testing that validates this statement.

Thanks,
Thomas

11. ### Peter Jessee Stunt Coordinator

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Thomas,

I'm sorry if my first reply to your comments was defensive in tone. I think I was in "Don't say my kid is ugly" mode. Since you have built multi-woofer systems before, I am interested in hearing your experiences.

You mention using 15" drivers in 18" X 24" X 20" boxes. That's about 5 cu ft, which as you say should give a Q=0.5 for a Quatro or a 15" DVC. Were these Quatro's or another driver? I have experience with a 15" DVC in a 4 cu ft box (Q ~ 0.6) with a Rythmik 350 watt amp, and it does an excellent job.

My proposal was to find out if more cone area moving a smaller distance would provide a more intense bass experience, or provide accuracy/lower distortion benefits. Others writing on this and other forums have expressed the opinion that sometimes drivers designed with lower Xmax and less rugged surrounds/suspensions provide better quality bass reproduction within their range of operation than the modern mega-woofers do. Thus my interest in using four of the much-less-expensive but still well-regarded Quatros to see if this might be the case.

It would seem that you don't embrace this opinion. But don't let me put words in your mouth. In your experience, does using several woofers have performance advantages over one, other than gross output advantages? Any comments you would agree to share would be appreciated.

Peter

12. ### John t. Agent

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Thomas,

I clearly satated From what I've read. I don't know if that was tested or not, but that's what I've read. Now if you want the links to the forums where I read it I'll post them.

13. ### ThomasW Cinematographer

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Peter,

I ran 4-modest excursion 15"s in sealed boxes in my first HT (1989). When DVD's came out I was bottoming the drivers all the time. That's when I threw in the towel and went for multiple drivers with much higher excursion.

Over the years I've found no advantage to multiple lower excursion drivers compared to higher excursion ones. It's actually easier to keep the distortion low with higher excursion drivers operating in the middle of their Xmax range, compared to low Xmax drivers operating toward the limits of their excursion.

You are correct in your thinking about having an over abundance of displacement. But to accomplish your stated goals you should consider drivers with 15mm or more of Xmax.

I have no direct experience with the Quatro drivers. They aren't something I'd ever consider using given their very high Le and low Xmax. If you do decide to use them I certainly recommend using ported boxes to decrease cone excursion.

BTW if you want a great deal on drivers John J at AE speakers is offering his AE-IB15" for \$100 each if 4 drivers are purchased. These drivers were originally designed by Nick at Lambda Acoustics and are certainly a step up from the Quatro units for not much more money.

14. ### Rory Buszka Supporting Actor

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If you don't want an IB-optimized woofer you can still get the rest of the former Lambda Acoustics product line from AE Speakers. Phone order only. Prices look nice and there's a special deal where if you order one, you get the second for \$99.

15. ### ThomasW Cinematographer

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Although marketed as such, the AE-IB15"s are certainly not IB sub 'optimized' drivers.

Not a low "Q" driver, they are certainly appropriate for other alignments. The low Fs and low Le are attractive features......

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