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Old 15th October 2012, 09:39 AM   #1
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Default low Qts woofer equalization for open baffle

hi all,
i want to use 12"/15" woofers in OB (coupled with ff85wk). but the unavailability of eminence alpha15a, has forced me to settle for other woofers such as beta12A, which is having low Qts(which is not recommended for OB). now i want to know,
1) what all equalization would be needed for using woofer with low Qts value in OB?
2) can this be achieved with miniDSP?
3) after equalization, will the performance be as good as alpha15A?
4) i also have an option to use below driver which is easily available locally at lot lesser price than any of the eminence woofers.
Ahuja Sound Solutions
comment on its suitability.

thanks
Shivaprashanth
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Old 15th October 2012, 02:29 PM   #2
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I've heard the Alpha 15A a couple of times and both times wasn't particularly impressed. Sure, you'll get some LF from an open baffle using that driver, but it didn't sound right - I think perhaps the tiny magnet is part of the problem.

A miniDSP will be able to do everything you need to get a different driver working on OB.

I haven't heard of that driver you've linked to. My guess would be that it'll be better value than the Alpha 15A, maybe better sound (once equilised).

Chris
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Old 15th October 2012, 03:44 PM   #3
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Quote:
Originally Posted by soundnovice View Post
hi all,
i want to use 12"/15" woofers in OB (coupled with ff85wk). but the unavailability of eminence alpha15a, has forced me to settle for other woofers such as beta12A, which is having low Qts(which is not recommended for OB). now i want to know,
1) what all equalization would be needed for using woofer with low Qts value in OB?
2) can this be achieved with miniDSP?
3) after equalization, will the performance be as good as alpha15A?
4) i also have an option to use below driver which is easily available locally at lot lesser price than any of the eminence woofers.
Ahuja Sound Solutions
comment on its suitability.

thanks
Shivaprashanth
Sure, you can often equalize a driver to flat and this is no exception. One problem that you will encounter, however, is that you will likely run out of headroom with the MiniDSP. It has a relatively low maximum output voltage, and when you apply a lot of gain this is reduced even further. A practical solution that will preserve headroom is to attenuate the input signal before processing it by the same amount that you will boost it at low frequency. You may need to use a higher amplifier gain for the woofer to make up for that, or turn down the gain (in the MiniDSP or at the amplifier) for the other drivers.

The lower Q driver has a free-air 12dB/octave low end rolloff that starts gradually at a relatively high frequency. On top of this, you will have a 6dB/octave loss from the dipole to worry about. This is killing your efficiency at low frequencies, so you need quite a bit of power on tap. The gain requirements may be quite high at low frequencies below 50 Hz. In your favor is the higher sensitivity of the pro driver you are using, but it is only helping a little.

-Charlie
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Old 15th October 2012, 06:03 PM   #4
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this thread is moved to multiway section
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