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The "designing the perfect subwoofer driver" thread...


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#21 of 734 OFFLINE   Hank Frankenberg

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Posted February 19 2002 - 12:06 AM

Dan, thanks for the dose of reality in pointing out the expense of the PR solution, which I thought would get out of hand. After all, DIY is not only about better than commercial performance, it's about low cost. I'm leaning towards sealed, myself. I'd like to have a musically fast, perfect sub that would also do justice to movie LFE's.

Brian, you're right about poly cones - they just aren't very good in any driver, sub or bass or midrange.

Jack, thanks for backing me up on suggesting two drivers, one optimized for sealed, the other for reflex configs.

Let the games begin!! Posted Image

#22 of 734 OFFLINE   Jack Gilvey

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Posted February 19 2002 - 01:03 AM

Quote:
Dan, thanks for the dose of reality in pointing out the expense of the PR solution, which I thought would get out of hand. After all, DIY is not only about better than commercial performance, it's about low cost.

Yeah, it's rarely the cheap way to go (well aware of that reality), but almost always a better alternative (from a performance perspective)than ports when one wants a reflex design for drivers like those proposed. Low Vas + high Vd = leaf blower. It would be interesting to see how output compares between, say, two of our theoretical drivers or one PR'd version, and how much power each option would take.
Quote:
I'm leaning towards sealed, myself. I'd like to have a musically fast, perfect sub that would also do justice to movie LFE's.
I think that the type of driver being tossed around could be just that perfect sub with something like a Linkwitz transform applied (or other eq). Imagine a sub with a Qtc of .5 (critically damped), and Fc of 16Hz, and more volume than you can use...

Quote:
Jack, thanks for backing me up on suggesting two drivers, one optimized for sealed, the other for reflex configs.

Didn't realize you had. :b I do think that might be the best way to go, no compromises for either app. Good idea Posted Image .

Quote:
For me, 115@20hz seems to be waay too much to ask for in such a small enclosure, and to be honest, I don't NEED that much horsepower. My priority is small size and GOOD performance....not over the top.

Well, this is the "over-the-top" thread. Posted Image And judging purely from a commercial sub perspective, that performance goal may be too much to ask, but give Dan a shot at it. Posted Image


Quote:
Wonderful discussion! Just so that I am clear on this; Dan, are you seriously considering this "imaginary" driver for possible production? I am just guessing, but I think you would have quite a market for it. Let's all hope.

If I'm not mistaken, Shiva was at least partly the result of just such a discussion on the Basslist. Dan's listening.

Quote:
If you can fit an 18" in a 4ft^3 box, fine, but a 15" is what I was thinking... at least I think it might suffice for most reasonably sane guys. Jack, you're SOL!

Hey, 15" makes sense to me! Especially in avoiding the breakup modes of an 18".

Quote:
What would it take to get that kind of efficiency? Edge wound coils? The old Altec VOT had edge-wound coils and they were scary efficient, like 96db or something, can you do that?

I don't there's any way to get even close given the other parameters we've expressed desire for. The old, big Altecs, JBL's etc. had big boxes and very high Fs.

Quote:
I think 115dB at 20Hz in a 3ft^3 enclosure would be every male's wet dream.
I disagree.
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#23 of 734 OFFLINE   Geoff L

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Posted February 19 2002 - 01:50 AM

Leave it to Jack to keep things in the proper Perspective

Yes, thats some serious *WOOFEN*

Posted Image Posted Image Posted Image

Keep it-->
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#24 of 734 OFFLINE   Brian Bunge

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Posted February 19 2002 - 02:14 AM

Jack,

Just the thought of Cathy there having sex with her grandfather is enough to turn me off. Still, for grace, sensuality, and beauty nothing beats Jane Seymour from the time period when she was in "Somewhere in Time" and "Lassiter." Not to mention that Playboy Pictorial!

OK, back to subwoofers!:b

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#25 of 734 OFFLINE   Randy G

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Posted February 19 2002 - 02:17 AM

>>Yes, that's some serious WOOFEN<<

If you meant WOLFEN, then I think VIXEN would have been more appropriate.

#26 of 734 OFFLINE   Kyle Richardson

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Posted February 19 2002 - 02:19 AM

I agree with the ability to be able to use this in a smaller sealed/PR box. 200-300 liters is just too big and can already be done with the Tempests or Maelstroms.

Mark, I agree with you on the PR cost issue. Why not just spend the money on another driver and throw two of them in a sealed box. Many people have not tried sealed boxes because they have heard they are not good for home theater. Let me be the first to tell you that a sealed box can ROCK for home theater! I have a Tempest in 3cuft sealed and it gets VERY loud with 350 watts. Could you imaging twice the throw of the Tempest and 2 drivers instead of one Posted Image Of course you could always use one driver and a couple of PR's if the EBP is in the mid range on this new driver.

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#27 of 734 OFFLINE   Jeff Rosz

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Posted February 19 2002 - 02:52 AM

jack wrote:
Quote:
I disagree.
and there it is, the Adire Audio CZJ line. an excellent choice, jack.

so i'll take a 15" in sealed box. eq'd?, ok. give me a lil efficiency on the side too. i dont wanna have to re-up cash on yet another amp. box size dont matter to me, after all wood is cheaper than electronics and how tall are those sonotubes folks have been building? so my vote is extension and efficiency.
why have one when you can have two for twice the price?

#28 of 734 OFFLINE   Randy G

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Posted February 19 2002 - 03:39 AM

2-12"ers working in bipolar fashion in a 1.5-2' box would fit the bill for me quite nicely.

#29 of 734 OFFLINE   Greg Monfort

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Posted February 19 2002 - 03:59 AM

>What would it take to get that kind of efficiency? Edge wound coils? The old Altec VOT had edge-wound coils and they were scary efficient, like 96db or something, can you do that?
====
Efficiency is basically a function of motor strength, compliance, and Fs. The simplified formula for efficiency is:

n0 = (K*Fs^3*Vas)/Qes

where:

n0 = reference efficiency in percent
K = 9.614e-10 (Vas in liters)
K = 9.614e-7 (Vas in cc)
K = 2.723e-8 (Vas in ft^3)

Once you have n0 then you can calculate the equivalent SPL/W/m:

SPLeff = 112.02+(10*log10(n0))

So if you want to see the effect each has on efficiency, play with the different values in a box program to find your 'ideal' driver WRT tradeoffs.
====
>I don't there's any way to get even close given the other parameters we've expressed desire for.
====
Not without using a servo motor AFAIK.
====
The old, big Altecs, JBL's etc. had big boxes and very high Fs.
====
Well, it takes big cabs to get any LF out of them, but their Fs ranged from ~18-25Hz, so I wouldn't call that very high. They were designed as a compromise to drive midbass horns (ergo their high efficiency) with some LF extension so needed the strong motors and high Vas that limited their LF peak output.

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#30 of 734 Guest_Anthony_Gomez_*

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Posted February 19 2002 - 05:00 AM

IIRC, edge would wire has a tighter packing ration which translates to a greater induced flux per coil length. ...so you ca get equal sensitivities with less wire...which means less inductance.

#31 of 734 OFFLINE   Vince Bray

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Posted February 19 2002 - 05:03 AM

Quote:
Hey, 15" makes sense to me! Especially in avoiding the breakup modes of an 18".


Note to chef, Jack Gilvey to be included in the 'reasonably sane' group! Posted Image

BTW, i disagree too Posted Image

#32 of 734 OFFLINE   James Mudler

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Posted February 19 2002 - 05:04 AM

Quote:
Still, for grace, sensuality, and beauty nothing beats Jane Seymour from the time period when she was in "Somewhere in Time" and "Lassiter."


Amen, simply the most beautiful women on earth....of course I am not counting my wife. I bought Somewhere in Time on LD years ago for that very reason.

Big subs get me excited ,but Jane well....................
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#33 of 734 OFFLINE   Hank Frankenberg

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Posted February 19 2002 - 05:52 AM

I'm so glad you boys like my cousin Jane Seymour. Honestly, her real last name is Frankenberg! Remember her film debut as Solitaire in the Bond film, LIVE AND LET DIE?

http://www.dvdempire....2&tab=5&back=1

Hmmm...you can marry DISTANT cousins, right? (rhetorical question)

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#34 of 734 OFFLINE   Brian Bunge

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Posted February 19 2002 - 05:55 AM

Hank,

In GA we marry distant cousins. Out there in TX y'all marry livestock!Posted Image

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#35 of 734 OFFLINE   Jack Gilvey

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Posted February 19 2002 - 06:00 AM

Quote:
Well, it takes big cabs to get any LF out of them, but their Fs ranged from ~18-25Hz, so I wouldn't call that very high. They were designed as a compromise to drive midbass horns (ergo their high efficiency) with some LF extension so needed the strong motors and high Vas that limited their LF peak output.

Gotcha, thanks Greg.

Quote:
Oh, we got that one covered already, then... Try a Brahma 12 in 3 cubic feet, tuned to 20 Hz with a pair of PR-15s (each loaded with 1100 grams of mass). You have an anechoic F3 of 18 Hz. Add in a crossover, and that drops down to the 17 Hz range.

And it will take a clean 1200-1300W straight out, without reaching Xmax (above 17 Hz). And you'll have SPL levels in the 110+ dB SPL range above 18 Hz. Spooky levels of output!
I'll say, that alignment looks incredible, and with none of the inductance issues of other "comparable" drivers I'd assume?

Quote:
Well, for the Uber-Tempest, probably a box in the 6-8 cubic foot range. Tuning to 19 Hz can be accomplished with an 8" diameter vent, 40" long. Big, but a vent nevertheless...

I really like the way Tempest looks in 10ft^3 with dual 6" flared ports, none of the early shelving rolloff seen in the high-excursion drivers. Maintain that response and I think that porting would be ok with twice the Vd.
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#36 of 734 OFFLINE   Hank Frankenberg

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Posted February 19 2002 - 06:45 AM

Now, Brian, be nice, boy. Actually, I heard that in Georgia, the cousin doesn't have to be "distant" to be marryin' material Posted Image

Back to the topic: Dan, what do you think about doing two designs, both 15", one the ultimate sealed, the other the ulitmate reflex? I can hear those gears turning!

#37 of 734 OFFLINE   Brian Bunge

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Posted February 19 2002 - 07:07 AM

Hank,

"Distant" is defined as more than arms length away!Posted Image

Dan,

I, like Hank, can see enough interest that separate sealed and ported 15" drivers might be warranted. Call the JU15-S (Jack's Ultimate 15-Sealed) and JU15-P (Jack's Ultimate 15-Ported).

Brian
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#38 of 734 OFFLINE   Jerry Parker

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Posted February 19 2002 - 07:10 AM

What about a HUGE driver that has the XBL (did i spell that right?) motor? An all out hardcore, best speaker that you could buy range. Im talking in the 21" to 24" diameter range! With something like 60mm peak to peak linear xmax, that would RULE, and you could get massive output at 20hz. Plus it would have better sensitivity than the smaller drivers. A less than 20cuft cabinet would be a must. Tuned with a 12" or larger port, this thing would rock. Plus you would only need like 1 crown K2 to power it! LOL, unfortunatly I cant even imagine how much something like this would cost, and it would definatly be out of my budget for the next few years, but for those that MUST have the best performance, and are willing to pay for it..... Posted Image

#39 of 734 OFFLINE   Michael R Price

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Posted February 19 2002 - 08:30 AM

I'd say it would be best to go with the two separate drivers (sealed and ported). The sealed one would have a high power handling (efficiency not as important), very low Fs and work in a small box (like 3 ft^3) for EQing. The ported one would be like a Tempest with twice the Xmax and work in a 8-12 ft^3 box where ports could be used. I think there'd be enough demand for such incredible drivers that it would be worthwhile to design separate ones for different applications.

By the way, how much Xmax is realistic for such a driver? 30, 35, 40mm... how do you design a driver to end up with so much linear throw? What makes the Brahma, for example, capable of its 27mm displacement whereas the Shiva is not?

#40 of 734 OFFLINE   DanWiggins

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Posted February 19 2002 - 10:26 AM

Hi all...

Man, this thread just pounds right along! Let me see if we can catch up...

1. Yes, I'm serious about rolling a driver for this design. There seems to be more interest in small/mid sized boxes, and equally split for sealed and vented. So let me see what I can do.

2. Yes, it will use XBL2 technology. And 30+mm is not a pipe-dream; it can be done.

3. We should start looking at a budget - would something in the $250-$300 range work?

4. So, a long throw 15" driver is a good target; that or a 12" unit. The 18" and the 10" really aren't that popular (funny, that's the way the market has pretty much always been...Posted Image).

5. You can't have efficiency, small box, and deep bass extension; violates Hoffman's Iron Law (Greg Monfort's post expounds on this). So if we go with smaller boxes and deep bass extension, then low efficiency it will be. Prepare for the assault of the kilowatt amps!

6. Jack, a Brahma in 3 cubic feet tuned to 20 Hz is a great thing...Posted Image And the inductance IS low - around 2 mH per voice coil (about 1/4 that of the typical ultra-throw drivers; it's actually lower than Shiva).

7. The goal is 115 dB SPL @ 20 Hz, anechoic, and somewhere around 1.5 kW powering it. That pretty much sets the defining size of the cabinet to 8 cubic feet (Hoffman's Iron Law). That's too big, isn't it? Would 110 dB SPL @ 20 Hz anechoic be a better goal? In a typical room, that should get you full reference levels...

I think I covered it all! Posted Image

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