Help with driver selection... (1 Viewer)

[Brian_E]

Welp, I've decided to build my sub. I used to be a car audio nut and so I've built 5 or 6 sub enclosures before. It sure was easy to get killer bass in a car.

So now I'm about to build a sub to compliment my Def Tech BP8B mains / C1000B center / BP1X surrounds. I want to keep the budget under $500 including amp, driver, box and materials (I have most tools). I'd say it will be about 70/30 for movies/music use. I don't listen to pipe organs or "1812 Overtures", but I have a broad taste in music so acceptable output to 20Hz would be nice. This will be used in a (26'x15'x8'total) living room that's open to the kitchen on one side. So about 3000ft^3. I listen to most of my movies at about -10db.
Now to get to the point...
My concern is box size, and I'm almost positive I don't want to do a sonotube. I just don't think I can finish it as well as a box (especially with a plate amp). Of course I want the box as small as possible; I'm thinking 3.5-4ft^3 max. I was just about ready to do the Shiva when I thought I would be able to get more output in the frequencies that mattered most to me (low 20's on up) with the Tempest in about the same size box. I've been using "Tempest Apps Vented Adire Alignment.box" from TempestDesigns.zip on Adire's web site for my basis. Change the box to 115L and tune to 20Hz. Then switch between the Tempest and the Shiva. What are your thoughts on this?
Now, to add another sub to the mix this thread got me thinking about the audiobahn ALUM12. It's the right price ($119) and it looks to have suprisingly similar T/S params to the Shiva. Take a look at them here . Has anyone used this driver? If the specs are right it looks like I would get much better performance than the Shiva in a smaller box.
Any and all of your suggestions are greatly appreciated.

 

[Julian Data]

I played with 3 drivers in LspCAD. I didn't know the BL, SD and other variables. So I used a BL of 14 (have no idea) and SD of 460 since the Audiobahn looks like a MASS. As for the others, I let the program calculate it.
Using 150W plate amp, 115L and with a Fb of 20Hz using one 4" port. This enclosure is a bit small for it. The Shiva is 2dbs under the Alum12 from 40Hz and down.
Again, I don't know what the BL, SD, Mmd, Mms, Cms, Cas, Rms are suppose to be. Also, the Xmax figure is rather confusing is it really 31mm p-p or one way? I think it's p-p.
jd
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[Brian_E]

Julian,
Thanks for taking the time to look at the ALUM12 in LspCAD. It would be nice to have the full version, since WinISD doesn't seem nearly as accurate.
I know some important data is missing from the T/S params, but I'm almost positive the Xmax is for p-p. A one way xmax of 31mm would be unbelievable.

I'm also a little curious about the sensitivity rating of 96.4db. I'm assuming all the specs were taken with the VC's in parallel, so that SPL rating is probably at 3ohm. It seems like a sub with real potential.
FWIW, I'll most likely be using the AVA250 or AMP350. Any suggestions on the Shiva or the Tempest in that alignment?

 

[Greg Monfort]

The ALUM12's sensitivity is more like 86.5dB/W/m. In doing some quick BoxPlot sims, in 115L/tuning to closely match FR, the Shiva is slightly underdamped, the Tempest somewhat more so, and the ALUM12 is a little less underdamped than the Shiva. Once you factor in VC heating, the ALUM12 will probably be ~ max flat, with the other two increasingly more underdamped.
On paper, at this cab volume, the ALUM12 is preferred, but I know nothing about them other than the listed specs, so YMMV.
GM
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Loud is beautiful, if it's clean

 

[Julian Data]

Brian,
I think the sensitivity was probably listed with the VC in parallel. It's amazing what manufacturers do, huh? Heck, some even post their BL with the VC in series to fatten up the specs.
It's a shame that most manufacturers don't list how the T/S parameters were measured b/c it makes a difference!
jd
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[Geoff L]

I too have a peeked intrest in the Audiobahn ALUM-12, at 119.00 and also the impressive ALUM-12X.
The latter being a 2OO1 model,and more costly.
They would apear decent performers from a quailty builder, given the limited info available from there site. It would be nice to see a complete set of TS-params, on these drivers.
Anybody else like the numbers their seeing?
Jack your always curious, have a look see.

 

[Marv]

I have the Audiobahn Alum15X on order and will post the T/S specs I get from it after a brief break-in. My intention is to use it in a sealed box with a Linkwitz boost filter. I ordered it from Zeb Audio for $225 but found it cheaper at Carmedia but it was not in stock there.
-Marv
Is it OK to post the links to the dealers?
Sorry if that is not permitted.
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[Jack Gilvey]

Looks pretty cool, although I had to bail on the site quickly because of the music they were pumping at me.
Forget the driver, though, this grill takes the cake:

Gotta get one of those.

 

[Geoff L]

Yes the grills are smoken.

But wew, even at 99.00, thier reduced priced, your wallet will be smoke to.
Oh, and the music you got t love it, NOT.
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Smoothe

 

[Brian_E]

Greg, I'm just curious...how'd you come up with the 86.5db/W/m rating? It does seem a bit more likely than the 96.4 audiobahn lists.
And I want to make sure my understanding of under/over-dampened (or is it damped?) is correct.
Underdamped = higher Q (more midbass hump, "typical" commercial sub alignment) ?
Overdamped = lower Q (smoother, flatter response, often cited as more musical) ?

 

[Julian Data]

Brian,
There are calculations that you can get the sensitivity of a driver. Adire site has this. LspCAD, let's you input all the known variables and does primarily the same calculations. After doing this, LspCAD say's the driver is 86.1dB @ 1W.
No need to fret though, the Earthquake is like 81dB although it's listed as being higher.
jd
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[Greg Monfort]

Some use slightly different formulas, but these seem to match measurements I've made:
When Vas is in liters:
n0 = (9.78*10^-10*Fs^3*Vas)/Qes
When Vas is in cuft:
n0 = (2.77*10^-8*Fs^3*Vas)/Qes
then:
SPL = 112.2+[10*Log(n0)]
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>And I want to make sure my understanding of under/over-dampened (or is it damped?) is correct.
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Damped.
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>Underdamped = higher Q (more midbass hump, "typical" commercial sub alignment) ?
====
Correctomundo!
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>Overdamped = lower Q (smoother,
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Yes.
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>flatter response,
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No. It will have a rising response. Maximally flat is a 0.707 Qb.
It just dawned on me though that my first response was technically correct, and changing the ALUM12 to overdamped was wrong.

An overdamped alignment doesn't occur until it's

 

[Marv]

Here are the T/S specs I promised for the Alum15X I received this past week. After about 1.5hr break-in the Fs=19.7hz, Qms=4.28, Vas=157.2L, Qes=0.484, Qts=0.434, Re=2.7Ohms, Bl=16.61Tm, Sd=829.4SqCm, Mms=399.98G, Le=2.89mH, Spl=86.1W/M, Xmax is stated as +/-19mm on the web site and because the basket has venting under the spider it is easy to see the amount of VC on the top side of the plate which "looks" to be ~19mm.
Now for the Good: This driver looks good, it's a shame most of it gets hidden in the box. Very nice solid trim ring. Woven leads in the spider. A very solid feel to the cone, I could not feel any flex in any part of the cone I pressed on with modest pressure. The terminals are also solid. T/S specs were close to the Mfg.’s.
Now for the Bad: Were they get 1.75" surround I have no idea, I measure 1" and maybe 1/16" edge to edge of the roll. Shipping damage, after unpacking the double box the 3rd box, which holds the driver, is wooden and was split/cracked in a couple spots. I opened the lid to find the (4) screws holding the driver were pulled through the wood and the driver was loose. It shipped with (8) mounting screws and only (7) mounting washers (stay with me on this missing washer).
Now for the Worse: During breaking I could only get a small amount of cone travel before I could here a ticking noise (it gets louder with more excursion). Well the pole piece vent has no screen in it so I don't know if that missing washer is in there or not. I would think not because it would surely stick to something before it could make it through the vent. When I manually move the cone in/out there is no hint of friction and I can't find anything loose on the driver. So I am at a loss to explain the defect and assume it has something to do with the VC windings. So it's time to test ZEB's customer service dept, I really hate the hassle and expense of returns.
So in fairness I can't give a thumbs up/down on this driver at this time other than to say it looks kick ass in your hands and on paper but that won't please my ears.
If any one has any ideas on that ticking sound I would like to hear them.
-Marv
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[Julian Data]

Marv,
I would return the driver and get a new one. The driver is screwed as it shouldn't be ticking..
jd
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[Geoff L]

Man what a downer. Will you try another?
Lets hope if you do, the ride to your home will be a little easier this time.
If you follow threw, what type of design do you have planed for this driver?
Good luck and let us no how Zeb's treat your problem, as im considering placeing an order threw them also.

 

[Marv]

Ok it took three weeks to get a replacement driver for my Alum15X. ZEB had me send it to the distributor that sent it to me and they lost my address to send the replacement too. ZEB was always polite and professional during the time it took to find the returned driver and paid shipping on the new driver. The new driver showed up better boxed but was still torn out of the wooden box (Audiobahn better start putting in all 8 screws). There was no damage and the driver test fine but has a higher QTS (.5) than the first driver. I plan on doing a small sealed box or an IB and it models well for both. I just may pick up another 15X because the driver puts me in awe when place it next to my other 15"er (name with held). I don't mind paying a little extra for all the eye candy, cast basket, rubber surround, woven leads, chrome trim ring, gasket and solid wire terminals. Let’s hope it sounds as good as it looks!
-Marv G
P.S. Geoff I have a stupid question. How do you pronounce your name?
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[Geoff L]

Marv,
Not the first time that questions be asked. Geoff is the same as Jeff. It's an english spelling.
The english pronounce it-- (Jawf-fray)
Cool or weird, you pick.
Geoffrey is how its spelled in full and normally used that way. I prefer Jeff to the more snobish sounding english.
Glad to here the driver made it ok and that ZEB seemed to treat you well. Hope your 15 monster lives up to its looks also. Keep us up on your progress!

 

[JonWB]

Marv,
Have you put together your sub using the Audiobahn ALUM15X subwoofer driver. I came across this driver here :
Seems like an awefully good deal at $130. I am looking to build a modest size sealed sub and thought that this looked good for an approx. 3cu.ft. stuffed box. I was also wondering how you wired it. 3, 6 or 12 ohms? I'm concerned that running one of the standard plate amps (AVA250, AMP350 or PE) at 3 ohms might be asking a bit much.
Thanks for any input!

 

[Robert_Gaither]

I found this link at www.carreview.com about someone using an Alum12 for an HT subhttp://www.carreview.com/Subwoofers/Audiobahn+AW-1200/PRD_3739_1808crx.aspx (date sept5/2000, I guess he posted in the wrong sub category) and was at one time considering several of their woofers for building an HT sub (the Alum series look awesome imho and one could clone many of the high dollar subs appearance this way) myself.

 

[Marv]

Jon, I ended up using my Alum15 in a band pass box that I had built for my 15"DVC after I smoked that driver. I personaly would buy the Alum15 over the 15"DVC especially at that price. If I had to build another enclosure for the Alum15 it would be sealed or IB. I am running it as a 3ohm load on one channel of my Carver753x. I don't know if your plate amp will get to hot at 3-ohms maybe someone here has some insite on that. The only advantage that the 15"DVC had over the Alum15 was slightly better efficiency. It almost seems a waste to hide this driver in an bandpass box because of its visual appeal but I needed it. I still use this sub but I'm experimenting with an IB. I'm using an Audiobahn 1805x that I picked up for $239 at Cardiscountstereos.com .