Inefficient Cab Design?

[fu22ba55]

Here goes...

How do I design inefficient 15" cabs? Shallower? Sealed? Open-Backed?

(For those of you not familiar with my "special needs", I LIKE cone distortion. I LIKE pushing speakers past their mechanical limts. I use an SVT turned up way too high. I don't use pedals. It sounds like this.)

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85% of the time, I need to be louder than loud. But there are times when I'd like to get the same sound at a lower volume. (WITHOUT TURNING DOWN MY AMP OR USING ANY GODFORSAKEN PEDALS.)

I find the TL606s move so much air... (they are nice and loud). I love my Sunn 215S, which is an even smaller box volume per speaker, but still ported, so it still flaps the pants.

I'm thinking maybe a pair of sealed, inefficient 1x15s?

I plan on building some fEarful 15subs this winter so I can get stoopid low and loud when I need to, but I figure if I have the saw and clamps and glue out, I should maybe try building some less efficient boxes too and see what happens. (I plan on using 3/4" ply because it's cheap and strong. I don't mind the weight.)

This is just an ill-advised, expensive experiment.

I don't mind replacing blown drivers every 18 months.

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Just to open the floodgates, I pulled up the Eminence Legend CB158. I don't really know how to use WinISD, but I got this far: If I calculated correctly, the optimum sealed volume for that driver is is 3.59 cu ft. So I punched in a 24" x 18" x 18" box and got 3.55 cu ft. Plotted, it looks like this:





If I wanted to start screwing around with LESS efficiency, what should I do? Shallower? Bigger? More Ports? Less Ports?

Do I want to stick with a sealed 15? (I've never ever played a sealed 15, so I'm curious what they sound like.)

Do I want to try and get more of a low-mid bump in WinISD?

1) I have the utmost respect for the accomplished cab builders and engineers on this forum. I know there is a wealth of info on building super-efficient boxes and uber-engineered BFM designs. (As I said... I plan on building some fEarfuls too...) I mean no disrespect to these fine artisans of acoustic engineering.

2) PLEASE DON'T TELL ME TO BUY A 200W AMP

3) PLEASE DON'T TELL ME TO USE A SPEAKER ATTENUATOR

4) PLEASE DON'T TELL ME AND MY BAND TO TURN DOWN

5) PLEASE DON'T TELL ME TO USE LESS CABS

6) I SWEAR TO THE BABY JESUS IF WORDS "PEDAL" or "VT BASS" APPEAR ANYWHERE ELSE IN THIS THREAD, I WILL EXPLODE LIKE THE DUDE FROM SCANNERS.

I'm curious how to build less-efficient boxes so I might be able find the sweet spot between volume and speaker punishment.

I'm entertaining the idea of building a 5-sided 24x18x18 box, and experimenting with an adjustable depth baffle to find the sweet spot.

I bow to you mighty speaker builders and your infinite knowledge. I am suppliant before thee. Have mercy on my soul.

[rpsands]

I think what you want to do is pick the right speaker. You can kill sensitivity under 100hz with weird cab design (e.g. sealing in a tiny box) but you can't kill midrange sensitivity as easily.

Find a speaker that distorts early but has lots of Xlim. The Delta 15A is what I would roll with.

They are cheap, so buy a spare.

* I'd consider a 3 cubic foot box tuned to 40hz, for the mad upper bass bump of oldschoolness (+3db centered at 100hz)

* Alternatively, for smooth low end, a 3 to 4.5 cubic foot box sealed.

[billfitzmaurice]

Sealed cab.

[fu22ba55]

Originally Posted by billfitzmaurice

Sealed cab.

Thank you Mr. BFM

Originally Posted by rpsands

Find a speaker that distorts early but has lots of Xlim.

I like the sound of "distorts easliy." I assume I still need to keep the high Xmax/Xlim since it's still reproducing bass guitar frequencies? (Otherwise, I'd be in guitar speaker territory and I'd be cooking speakers every 15 minutes? Is that the logic?)

Originally Posted by rpsands

* I'd consider a 3 cubic foot box tuned to 40hz, for the mad upper bass bump of oldschoolness (+3db centered at 100hz)

I also like the sound of "the mad upper bass hump of oldschoolness"

I will meddle with WinISD more and report back.

[rpsands]

Low xmax, high xlim is fine for reasonable power usage as long as you're OK with burning out drivers occasionally. Exceeding xmax is where distortion occurs, and exceeding xmax but not xlim over a long time will cause a woofer to wear out -- no real idea how long that takes.

With a 5mm xmax 15" woofer you're going to need a lot of power to cause speaker breakup. It will be brutally loud by the time you're distorting.

With 2.7mm xmax, you should need around 1/4 the power to cause distortion.

Try modeling the Delta 15 in:
3cf sealed
2cf sealed
3cf ported tuned to 40hz
4cf ported tuned to 40hz
4.5cf sealed

[babebambi]

isolated speaker box, then mic that

[Petebass]

Originally Posted by rpsands

Low xmax, high xlim is fine for reasonable power usage as long as you're OK with burning out drivers occasionally.

This, and sealed. You're basically designing a guitar cab.... have you tried one of those?

[rpsands]

Originally Posted by Petebass

This, and sealed. You're basically designing a guitar cab.... have you tried one of those?

Guitar speakers usually don't have a low enough Fs or high enough Xlim to work for this application.

The delta 15A is really the boss for this kind of application from what I can see.

[Sartori]

I'm curious to see how this turns out.

[seamonkey]

Originally Posted by babebambi

isolated speaker box, then mic that

and then add louvers/shutters like old pipe organs that you can open and close to control the volume.

[fu22ba55]

So I spent some time in ISD Online with the Delta Pro-15A, and got some pretty pictures, and I realized they meant very little to me without some kind of control. So I plotted some stuff that I know I like and don't like:

My ears like this:
EV15L in TL606 (Fb 55Hz, no stepdown cover)


My ears don't like this:
Kappalite 3015 in TL606 (Fb 55Hz, no stepdown cover)


I don't know if there's something magical happening with the 15L above 1khz that I'm not seeing in these graphs... but if I like the top graph above then the bar is set pretty low and I should have no trouble getting something I like with a newfangled driver in a poorly designed box.

On to the pretty pictures:

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Delta in a 3 cu ft sealed box:


Delta in a 1 cu ft sealed box:


Delta in a .66 cu ft sealed box:
(17" x 17" x 6.25 deep. It barely fits.)


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Then I read a bit more about what rpsands said about low Xmax and high Xlim, and I tried plotting the Kappa Pro-12A just for fun:

Kappa 12A in a tiny little sealed box:
(14" x 14" x 7.75 deep.)


This cute little 12" doesn't look half bad. I really tend to boost around 300K, (that's where much of my fuzz comes from), so I don't know that I'd miss much below 100K for this exercise.

I'm definitely going to try the 3 cu ft sealed Delta box, and maybe that cute little 12" box too.

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Are there no modern guitar drivers that would be worth trying out as well? I took a peek at some of the Eminence guitar drivers and they have almost no Xmax (which I hope means they'll distort like crazy), but they also didn't provide any Xlim, which is a bad sign.

With all the doom kids doing their droppitty-drop tunings and 9-string baritone guitars, I imagine they're pushing the low end of things pretty hard these days. There must be some guitar speakers out there I could try to cook in the name of fuzz science. Would any of them survive in a sealed 15" or sealed 12"? (Again... I'm only using an SVT, not some 4000 watt rig. And I rarely tune below standard E, so there might be something else out there worth trying.)

[fu22ba55]

Originally Posted by seamonkey

and then add louvers/shutters like old pipe organs that you can open and close to control the volume.

I really like this idea, (just because of how kludgy it is), so this might come up again later.

Or I could loosely mount some perforated layers of sheet metal in front of the driver so they would rattle like wind chimes. Like the rivets in a sizzle cymbal. I'm 100% serious.

[billfitzmaurice]

You won't see anything accurate above 200Hz in WinISD; I don't even graph above 200Hz. Above that you have to compare the driver data sheet SPL charts.

[rpsands]

Everything you like about the EV15L vs. the 3015 is happening above 400hz if not higher. I would guess it's the cone breakup modes above 1khz.

The 3015 is often called sterile in the mids and I believe that, based on the FR graph.

Based on you liking the EV15L I am pretty sure you would wind up liking the Kappa Pro-A series or the Delta 15a. I'd do the delta first since it's much cheaper. 70 bucks from Beach audio.

I would worry less about the bottom end and more about the midrange character.

[billfitzmaurice]

Originally Posted by rpsands

Based on you liking the EV15L I am pretty sure you would wind up liking the Kappa Pro-A series or the Delta 15a.

Low Qts/high Qts = Apples/oranges. Nothing approaches the EV highs anyway, they are the product of a much smaller gap than Eminence uses.

[rpsands]

Originally Posted by billfitzmaurice

Low Qts/high Qts = Apples/oranges. Nothing approaches the EV highs anyway, they are the product of a much smaller gap than Eminence uses.

qts aside, the midrange character of the delta 15a and 12a is much different than the 3015. I don't expect it to be like the 15L but closer than the 3015 would be.


BTW - when I was talking about the delta 15a earlier I meant the 12a. Much lower xmax, more distortion. Probably better for this application. WOOPS.

[fu22ba55]

Thanks guys. I really do appreciate you humoring my unorthodox requests.

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I realize the 15L is it's own thing, and I hope for this exercise the shiny highs don't really matter... I'm hoping that I like how it's low end drops off sooner than the modern drivers. (Which, when I turn things up, translates into more audible mids & low-mids, since the lows are absent. This is probably also why I don't like the 3015 as much... because it's so accurate.)

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Originally Posted by rpsands

BTW - when I was talking about the delta 15a earlier I meant the 12a. Much lower xmax, more distortion. Probably better for this application. WOOPS.

You mean all my pretty pictures were for naught? (Just kidding. I'm actually (finally) learning a little bit about this stuff, and it's a valuable experience. I plotted some of the fEarful subs and I can't wait to whack those boxes together.)

So, to be clear @rpsands, which speaker are you recommending I model?

Delta Pro-12A: 4.6mm xmax
Delta Pro-15A: 4.3mm xmax

Kappa Pro-12A: 4.8mm xmax
Kappa Pro-15A: 3.2mm xmax (xmas? Merry Xmas!)

You mentioned 2.7mm xmax in post #5 and I can't find a Kappa or Delta with xMax that low.

(I also like how on ye olde EV15L specs that I dug up online, "Xlim" was called "Xdamage.")

[fu22ba55]

Originally Posted by fu22ba55

You mentioned 2.7mm xmax in post #5 and I can't find a Kappa or Delta with xMax that low.

Whoops. Found it. Delta 15A & 12A NON PRO. (American Standard on Eminence site...)

Carry on...

[fu22ba55]

Whoa... plotting the Deltas (non-pros) now.

I have discovered the mad upper bass bump of oldschoolness of which you spoke earlier.

[rpsands]

I was wrong again actually, it was the 15a I was talking about, just the non-pro version. Rechecked my specs.

2.7mm xmax, 11.1mm xlim. That's the 15a.

The 12a looks like a good candidate too.

When you model those guys you'll see large upper bass peaks in ported cabs, and moderate upper bass peaks in small sealed cabs.

Sorry, I've been a bit scattered today!