Lowish Qts subwoofer?

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I'm still obsessing over this Qtc = .5 subwoofer thing.

Most of the popular subwoofer drivers have a Qts around .4 - the Shiva is an example. A closed box for such a woofer yielding a Qtc of .5 would have to be around 8 cubic feet or a bit less with stuffing. That's larger than I would prefer.

The Peerless 12 inch XLS woofer has a Qts of .21. It would require a box of only a little over 1 cubic foot. But that low Qts means the Fs => Fb goes up by a factor of almost 2 1/2 when you put it in the box.

A Qts somewhere in between would be preferable, assuming the Vas and Fs are low enough.

Is there no such thing as a subwoofer driver with a medium lowish Q, maybe around 0.3, and reasonable Vas and Fs numbers? If there is, I can't find it.

Would it be reasonable to use the Peerless with a resistor in series to raise the Q?
 
>Is there no such thing as a subwoofer driver with a medium lowish Q, maybe around 0.3, and reasonable Vas and Fs numbers? If there is, I can't find it.

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Nope, you give away too much efficiency for most folks.

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>Would it be reasonable to use the Peerless with a resistor in series to raise the Q?

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At the signal level between the preamp and sub amp. If I'm going to trade efficiency for BW in a sub, then my preference is to mass load it and 'kill two birds with one stone' by lowering Fs and raising Qts.

2x mass based on published specs:

SPLeff'
81.777

n0'
0.0009456

Qts'
0.281

Qms'
5.233

Qes'
0.297

Fs'
12.799

mass ratio
2.000

m' (g)
406.459

Mass (g)
203.2290

Qts
0.199

Fs
18.100

Qms
3.7000

Qes
0.2100

Vas (L)
139.330

diameter (cm)
25.360

added mass (g)
203.230



GM
 
The old Peerless TA305F would have fit your requirements. I think that Zalytron still sells their knock-off version of it. Might be worth a look. I've got a couple of the originals (they're the drivers in the ugly TLs in my garage), but they need new surrounds, which I'll get to as soon as the 436 other things on my plate get done.
 
FYI
 

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I've used this driver, it's well constructed. I didn't suggest it since I thought it was long gone from the marketplace and its inductance is too high for the app. IMO. It wasn't a big seller.

Good luck getting it flat to 31Hz in-room though unless the room is either extremely small and/or extremely well built due to its highish inductance.

GM
 
Dave Jones said:
Anyone know anything about a "SAE 1204" from Apex Jr?

This is a driver built by Lambda for Stryke. I have one in a box and ChrisB has one in an 18" cube with a ParaPixen. It works really well. Like most drivers aimed at being subs it doesn't go all that high. i have yet to see any pictures on the net that do this beauty justice.

dave
 
planet10 said:


This is a driver built by Lambda for Stryke. I have one in a box and ChrisB has one in an 18" cube with a ParaPixen. It works really well. Like most drivers aimed at being subs it doesn't go all that high. i have yet to see any pictures on the net that do this beauty justice.

dave

What's a ParaPixen?

Now a real dumb question: How do you mount that driver? Do you just cut a hole in the baffle and drop the driver in from the outside?
 
GM said:
I've used this driver, it's well constructed. I didn't suggest it since I thought it was long gone from the marketplace and its inductance is too high for the app. IMO. It wasn't a big seller.

Good luck getting it flat to 31Hz in-room though unless the room is either extremely small and/or extremely well built due to its highish inductance.

GM

Please elaborate on the inductance. I've heard that low inductance is a Good Thing, but I'm ignernt as to why.
 
Dave Jones said:
What's a ParaPixen?

Steve @ ApexJr got his foothold with the DIY community by selling some 2K surplus ParaPix (Paramount Pictures) plate amplifiers. These are 2 x LM3875 with mono support circuitry. They cost $20 each + another $20 if you wanted a suitable power transformer. An excellent deal.

Now a real dumb question: How do you mount that driver? Do you just cut a hole in the baffle and drop the driver in from the outside?

The SAE 1024? Yep that will work -- the same as most drivers... if you want to be real tidy you can do a rebate too.

dave
 
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