Building A Sub

Reference this please?
Honestly ( coming from working in "Pro Sound" since the 60's ) I would keep it simple and build 2 single 18 cabs. Lighter, more transportable, positioning flexibility. And would allow for a simple 2 element sub array ( w additional delay ) .
Edited by WVSyd - 2/16/13 at 11:23am

Well, welcome to AVS.

It's not weird to want to get the most dBSPL of of a sub. You state PA use, is this primarily for live music, DJ'ing, can you be a bit more specific. The community here is strong, you've come to the right place, but a bit more info could really help.

Are you designing a vented sub? Are you familiar with such tuned designs? Have you considered other types of designs, horn loaded, tapped horn, etc?

Do you already have the amplification you'll be using?

The design you're describing does nothing I'm aware of that raises the SPL of the output. The wavelengths inherent to subwoofer's range aren't affected by the positioning of the drivers, ie, angling them inward like your example showed. Perhaps one can save some space by doing so, maybe a full blown face to face design like the old EV manifold stuff can possess benefits. But acoustically, I'm not sure anything is to gain by angling them in the manner in which you're stating.

A 3-10dB increase? ... sorry, that's not happening.

The manner in which acoustics increases work dictates a 3dB increase, is equal to doubling the power, ... and a 10dB increase equals a 10x increase in power! That's huge!

Everyone wants what you want. We all want as much out of our subs as possible. But the physics involved cannot be cheated.

I think if you posted a budget, and how many boxes you want, the group here will design something perfectly ideal, and it'll be the best possible quality, highest possible output for the money.

+1. It won't add any SPL, while it will reduce extension, as the interior volume is less than if the baffle was flat. How did you arrive at those dimensions? Did you use software to model the driver/enclosure?

Here's an interesting website, and it's a brief explanation of bass/subwoofer myths that are so prevalent. Also, after you've read those, look around a bit. That is the best subwoofer/driver testing website I'm aware of. The individual that started up the Data-Bass site, is also an avid AVS forum contributor.

Best of luck

Technically, wouldn't a 10db increase be a 6x increase in power (more or less)? Not that it has any relevancy to anything.

Nope, sorry ... 10x = 10dB

10 dB more SPL, equals a 10x increase in amplifier power.


When working with power, 3dB means 2x, and 10dB = 10x


edit; to clarify further, a 6x increase you mentioned above, would equate to 7.8dB

For example, using 100 watts as the reference;

200w = 3dB
300w = 4.8dB
400w = 6dB
500w = 7dB
600w = 7.8dB
1000w = 10dB


P(dBW) = 10 · log10( P(W) / 1W )
The power in dBW is equal to the base 10 logarithm of the power in watts
The example is one thing, but I had to go find that formula
Edited by FOH - 2/16/13 at 1:15pm

You need to spend a few days or even weeks here before even thinking about designing your own speaker:
http://techtalk.parts-express.com/showthread.php?219617-The-Speaker-Building-Bible

"I want to get the most db's out of this I can. I've read about designing the speakers to face each other will get more db's."

very minor increase, perhaps 1db of bass. the principal advantage seems to be in the low pass cutoff effect.

here is the spec sheet for a cab that employs this approach. at around 100db 1w1m for the bass end, it isn't much of an increase. there is a little increase up near 200hz before the rolloff, but i'm guessing that isn't what you are after.

http://www.rcf.it/c/document_library/get_file?p_l_id=251923&folderId=22487&name=DLFE-7309.pdf

That's a bit different. The drivers are at a tight enough angle that a true front chamber is created, making the cab a bandpass. It's not a very well done bandpass, it doesn't go low enough on the one hand and goes too high on the other, but that's what it is. The driver angle on the Nady is too shallow to accomplish anything useful, but Nady isn't exactly known for their speaker design expertise.

This will give you a reasonably realistic expectation of what that driver is capable of in cabs of various sizes
www.eminence.com/pdf/Delta_Pro_18C_cab.pdf

I'd like to read some good measured work on the subject.

I'd suspect the EAW subs, similar to the ubiquitous SB1000 type subs (found everywhere over the past twenty years) wouldn't possess much bandpass effect at all within the subwoofer range. I enjoy the all the wonderful benefits of a quad 18 manifold outlet quad 18 IB, without any apparent/measurable bandpass effects, negative or otherwise. It's akin to a big ol' quad entrant compression driver.

Myself, contemplating the physics, I've never considered any such design as anything but a means to tighter packing of the LF sources. I always thought the idea was tighter packing, and all the benefits associated therein.

Then, other "knock off" mfrs styled their stuff similarly ... many of which don't even enjoy the benefits of tighter spacing, they angle them slightly, like the Nady, for mere aesthetic reasons.

The SB1000 is pretty much the same as the RCF. A more extreme example would be the old EV MTL manifold subs, with the drivers directly facing each other, albeit reverse mounted. The dead giveaway that it's a bandpass is the steep rolloff in the midbass.

Berr, any update on your plans?

Good luck in what you choose


You're right, that's why I mentioned them in my first post in this thread. Now that's tightly packed sources! In the early/mid 90's, I encountered these a handful of times. But I believe I've only mixed FOH with them one occasion. I remember discussion of them being limited wrt top end extension, but you're right 200hz is about it. But realistically, I wouldn't want the big excursions of the bass energy interacting much higher than 200 anyway.

From a both a theoretical and practical perspective regarding cooling, I thought having the motor structure being exposed was a great idea.

I don't know how much success EV enjoyed with the MTL stuff, but their current X line, is phenomenal. Sure, every major mfrs. line array stuff is superb these days, but I'd not been exposed to many EV rigs in a long time. I was blown away by their capability. I encountered them associated with a mammoth, multi-act country stadium tour. I spent a few days enjoying the capability, all at the floor FOH mix position. I wasn't mixing, I was working for the house. But my point is EV hasn't been left behind, as was my previous perception, in the quest for state of the art pro audio.


Thanks