Minimum recommended qts for OB use?

[vaughn]

I have a pair of Stephens Trusonic 120FR 12" speakers that I would like to try on an open
baffle. They have a qts of .475 and I am wondering if that is too low for open baffle use?

Looking at the 12" PHY speakers on Madisounds website I see that their qts is .62, not much
higher and yet it states that they are made specifically for open baffle use.

Thoughts?

I should also add that the Fs for the Stephens is listed as 30 hz.

[Nelson Pass]

It's a little low. The best overall results I've had with the Eminence
woofers (as a common example) is the Eminence beta with a Qts of
0.58. The Eminence Alpha is preferred by Martin King at 1.26.

It sounds good, but I have a slight preference for the Beta, which has
less of a bump above 45 Hz and more response below.

By contrast, the Gamma has poorer bass response than either of the
others, with a Qts at 0.30

Of course you can EQ this easily enough.

[vaughn]

Thank you sir...

I actually did a little experimenting today on some open baffles I had made a la JE Labs. These
are 32" high, 36" wide with wings that taper from 10" up to 5" at the top. I found a pair of
Electro-Voice 12 LT coaxial speakers the other day that appear to have a qts of about 1.6 according to info I could find on the web. The EV's sound great on the open baffles but the
Stephens are not as good at .475. I have no measuring equipment but my ears but the EV's have much better bass than the Trusonics on the baffle.

[croat47]

Mr. Pass,

What if one were to use two 15": a Beta and Alpha. On an 18" baffle, the Beta on the lower position and the Alpha on the Higher Position (FR, MT above those, of course). Could they compliment each other and smooth things out for a longer range?

Playing about with XBaffle to compare the two and thought I would ask the question.

[dobias]

Nelson Pass,
You said, "Of course you can EQ this easily enough."
Would you please direct me to a way to EQ my Wharfedale 12CS-AL speakers?

FS: 26.4 Hz
VAS 11.4 cu.ft.
Qts 0.26
Re 5.3 ohm
Le 1.48 mH
Eff. 95 dB/w/m

Each OB has one full range, augmented with two Super 3 tweeters (5 kHz) & a 12RS-AL mid bass (600 Hz.) I find I still need to have a pair of subs to provide decent bass.
Frank Dobias

[Cal Weldon]

Originally posted by croat47
What if one were to use two 15": a Beta and Alpha.

Try not to use different drivers to cover the same range. It's like using different tires on your car. One for traction , one for a smooth ride. Doesn't really work.

[Cal Weldon]

Originally posted by dobias

You said, "Of course you can EQ this easily enough."

You can but it puts a heavy demand on your amp. If you can, get a woofer in the range of Q = 1

[croat47]

Cal,

Thanks. You could cross between them if you were active, yes? Passive would cost a bit in coils as it would be in the "subwoofer" ranges for crossover. Too complex in the end, I suppose.

[Telstar]

In my opinion Qt is not everything. Even 0.4 can work. Xmax is more important, otherwise the driver will distort soon.

Of course a bass augmentation is needed with "thinner" FRs.

[ttan98]

Originally posted by Telstar
In my opinion Qt is not everything. Even 0.4 can work. Xmax is more important, otherwise the driver will distort soon.

Of course a bass augmentation is needed with "thinner" FRs.

If you ask Martin King he will disagree with you, he said Xmax is not that important, look at Alpha 15" its Xmax is low about 3.8mm.

If I am buying woofer I will be looking for Qts no less than 0.65 and low FS equal or less than 40hz. There are a few models from Goldwood drivers range that satisfy this criteria and they are cheap. Buy 2 per side instead of one.