Large Dipole subwoofer?

**justin.kerr** · **03-03-08, 02:16 PM**

I am contemplating building (4) towers, each with 4 forward facing 18" drivers, and 4 rear facing drivers. The main idea here is to maximize the driver to floor space ratio.
The rear firing drivers would be 3"-8" away from the wall.
My question is, are there inherent problems with this design? It seems that it could create additional room nodes?
Is there any inherent benefits to this design?
I have heard about the opposing drivers canceling each others harmonics out?

**BoomieMCT** · **03-03-08, 02:27 PM**

First off, are you sure this is a dipole sub and not a bipole sub? The answers can be very different depending on how these are wired up.

I may have the terminiology all wrong but it is my understanding in a bipole sub the drivers all go out from the enclosure at the same time. In a dipole sub one goes in while the other goes out (or there is one driver in a baffle with no enclosure).

Also, how big is your room that you want/need 16 18" drivers!?! You get mad props for overkill!

**justin.kerr** · **03-03-08, 02:35 PM**

Well I did not want the heading of the thread to say, "Large Bi-pole"

Some may take it the wrong way.

It would be 32 18" drivers, 8 in each tower, 4 towers.

The room will be appx. 18.5' W x 23' D x 9' H

**BoomieMCT** · **03-03-08, 03:26 PM**

Make sure you have an engineer inspect your foundations first!

I don't think bipoles are too much different then monopoles for subs. The wavelengths involved are so long the extra path length shouldn't make that much of a difference. As far as advantages - it can be a more compact way to set up your subs. Also the vibrations from each driver should cancel each other out.

My only possibly negative thought would be that 3" may not be enough clearance for the rear four 18" drivers.

**justin.kerr** · **03-03-08, 04:04 PM**

On the rear clearance, I was hoping that I could play with that, hoping I could get it to work within a range of 3"-8"? Maybe it would require more space?

**Ricci** · **03-03-08, 09:44 PM**

Maybe upgrade your amplifiers that are driving the current 8 190v2's you have first? What do you have now, 4 EP2500's?

**justin.kerr** · **03-03-08, 10:04 PM**

Yes I have 4 EP 2500's, and I know that they are the weak link. I will replace them, but that would only be a again of around 2db? But my goal is to gain 12db.

**Geoff St. Germain** · **03-04-08, 06:56 PM**

I'm all for bass overkill, but I'm not sure I get the point. What are your mains? The two bass towers you have now are capable of about what... 126 dB @ 1m at 10 Hz and over 130 dB @ 1m at 20 Hz? And that's not factoring in any room gain. Can the mains compete with this? If it were me I'd look at spending some of that ~$5K on upgrading the mains if volume is a problem.

**justin.kerr** · **03-04-08, 09:54 PM**

Yes, the current mains can more than keep up now, but they will not be used in the new theater.

I am curious, for 5K, what do you recommend for mains?

As of right now the projected mains will be capable of 130db peaks, each, which would require 140db out of the subs, to match for cinema experience.

**Geoff St. Germain** · **03-04-08, 10:02 PM**

I'd look into the Lambda TD10/Fountek NeoPro5i MTMs discussed in this thread. They'll be capable of 130 dB peaks. Of course this is a DIY solution. These are the the 12" version of the midbasses.

**justin.kerr** · **03-04-08, 10:07 PM**

I have been E-mailing John with my needs. lol His speakers are my first choice, ATM.

**Geoff St. Germain** · **03-04-08, 10:11 PM**

Interesting coincidence. I've emailed John looking for pricing.

**Owen Bartley** · **03-05-08, 02:54 PM**

Aha, so this is the project! I'm still just blown away be the sheer woofage of what you're proposing. I mean, even building ONE of those towers has an insane amount of displacement, and would require a ton of work and materials to build and brace the box!

**justin.kerr** · **03-05-08, 06:51 PM**

I might be down to just 2 towers now, A new driver is coming out, that should get me my sound and spl goals with just 16 drivers! 20 tops, lol

**acoustat6** · **05-12-08, 10:39 AM**

Hi, It sounds great to me, I use 32 eight inch drivers in a stereo pair. There are (obviously) eight forward and eight rear facing drivers in each eight foot tower. Here are some pictures.
Bob

**Ricci** · **05-12-08, 02:36 PM**

Nice towers there Bob! That is a lot of 8" drivers. What's the amplification for them and how high do you run them before filtering?

**Blaser** · **05-12-08, 06:36 PM**

Just a question: why 32 8" subs? why not say X 15 or 18" subs? Did you chose 8" subs for some reasons? or is it just how things went?

**eyekode** · **05-12-08, 11:22 PM**

Quote:

justin.kerr wrote:

Yes, the current mains can more than keep up now, but they will not be used in the new theater.

I am curious, for 5K, what do you recommend for mains?

As of right now the projected mains will be capable of 130db peaks, each, which would require 140db out of the subs, to match for cinema experience.

Hrm... 120db is the threshold for pain right?! 140db ~ bleeding/bursting of ear drum. I am all for excess but why would you want to put yourself through this?!

**SQBubble** · **05-12-08, 11:59 PM**

I wouldnt consider 140db bleeding/bursting ear drum, although it is indeed very loud, its pretty much the limit for listening and enjoying real sound effect IMO(for me at least), above 140 is where it starts to get a bit too loud for listening, talking about sub-bass only of course....

But then again, some people can support more spl than other, nobody has the same ear...

**Blaser** · **05-13-08, 12:17 AM**

140 db is doable for bass but a killer for midrange for ex.. I sometimes crank 130++ from my car sub.

**acoustat6** · **05-14-08, 09:41 AM**

Hi Guys, Ricci, I use a pair of "vintage" SAE 2400 solid state 200wpc amps. The left channel in each amp drives the front eight drivers and the right channel drives the rear eight drivers. So a stereo amp for each tower. The interesting thing is that even on the loudest material I see only about a few watts on the power meters and on 75% of the music less than one watt! Of course there are 4 channels producing 1 watt and 32 drivers producing sound. The drivers, even when being driven hard are moving only 1-2 milimeters. They are currently crossed over at 120 hz but I will be trying 85hz (need a freq module from Marchand to change crossover points) as I am using REW now and it looks like 85hz may be a better choice.

Hi Blaser, It was fortuitous that I bought and built these subs. I was buying a used VPI TNT turntable back in 2000 and went to pick it up. The gentleman had a rather nice setup with the big Soundlabs electrostats and a pair of these subs. I have Acoustat sixes which are 8 feet tall also. I was using a number of subs but nothing fit the bill. He and another fellow, a friend of his is an audio designer with the same big Soundlabs, and they decided to build the "ultimate" subs for their system. They designed the speakers you see using custom designed Eminence eight inch drivers in a sealed box. The design also took into account materials for efficency and the fact that they would be using the Marchand Bassis EQ to deal with the inherent rolloff of a sealed box. They needed to buy 100+ drivers to get the price in line so 32x3 is 96 plus a few left over to get their discount price. They built their two sets and I bought the third set as soon as I saw and heard them. Plus I like the fact that they are easy to drive with very low distortion levels. These could easily be driven with a 50 watt amp.

Bob

**Ricci** · **05-14-08, 02:57 PM**

Very nice. I bet you have a very solid upper bass impact (slam)with those!

**Blaser** · **05-14-08, 05:25 PM**

Quote:

acoustat6 wrote:

The interesting thing is that even on the loudest material I see only about a few watts on the power meters and on 75% of the music less than one watt! Of course there are 4 channels producing 1 watt and 32 drivers producing sound.

Not surprising, with all these subs, efficiency must be very high!

Quote:

Hi Blaser, It was fortuitous that I bought and built these subs. I was buying a used VPI TNT turntable back in 2000 and went to pick it up. The gentleman had a rather nice setup with the big Soundlabs electrostats and a pair of these subs. I have Acoustat sixes which are 8 feet tall also. I was using a number of subs but nothing fit the bill. He and another fellow, a friend of his is an audio designer with the same big Soundlabs, and they decided to build the "ultimate" subs for their system. They designed the speakers you see using custom designed Eminence eight inch drivers in a sealed box. The design also took into account materials for efficency and the fact that they would be using the Marchand Bassis EQ to deal with the inherent rolloff of a sealed box. They needed to buy 100+ drivers to get the price in line so 32x3 is 96 plus a few left over to get their discount price. They built their two sets and I bought the third set as soon as I saw and heard them. Plus I like the fact that they are easy to drive with very low distortion levels. These could easily be driven with a 50 watt amp.
Bob

Thank you Bob!

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