The "designing the perfect subwoofer driver" thread... (1 Viewer)

[Hank Frankenberg]

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!!

 

[Jack Gilvey]

I think 115dB at 20Hz in a 3ft^3 enclosure would be every male's wet dream.

Link Removed

 

[Geoff L]

Leave it to Jack to keep things in the proper Perspective
Yes, thats some serious *WOOFEN*

Keep it-->

 

[Brian Bunge]

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

Brian

 

[Randy G]

>>Yes, that's some serious WOOFEN

 

[Kyle Richardson]

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 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.
Kyle Richardson
Acoustic Visions

 

[Jeff Rosz]

jack wrote:

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.

 

[Randy G]

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

 

[Greg Monfort]

>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.

GM

 

[Anthony_Gomez]

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.

 

[Vince Bray]

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!
BTW, i disagree too

 

[James Mudler]

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....................

 

[Hank Frankenberg]

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.com/Exec/v4_ite...2&tab=5&back=1
Hmmm...you can marry DISTANT cousins, right? (rhetorical question)
-Hank "over the top" Frankenberg

 

[Brian Bunge]

Hank,
In GA we marry distant cousins. Out there in TX y'all marry livestock!
Brian

 

[Jack Gilvey]

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.

 

[Hank Frankenberg]

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

 

[Brian Bunge]

Hank,
"Distant" is defined as more than arms length away!
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

 

[Jerry Parker]

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.....

 

[Michael R Price]

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?

 

[DanWiggins]

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...).
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... 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!
Dan Wiggins
Adire Audio