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Old 4th December 2007, 01:20 PM   #1
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Default Does Q matter on the Alpha15A and Delta 15A ?

Simulating the Eminence Alpha 15a and Delta 15a drivers in an OB shows quite a bit of difference in the low end below 70Hz . The Delta is much more efficient but has a very drooping low end which might need some bass eq. The Alpha on the other hand goes down much lower but is less efficient. That's expected with the Qts of the Alpha being 1.26 and the Qts of the Delta being 0.53 .

I guess the Delta can be EQ'd to be similar to the Alpha's response.

The million dollar question is will the Delta sound better in this case ? Specifically will the "Qts" difference be audible ? A high Q will cause ringing on stepped signals . Will this be audible as floppier bass on the Alpha ? I know the argument will arise about the 'HF' harmonics of the bass will be 'crossed over'. But what about a single cycle of say 40Hz ?

I have read differing opinions on this issue. Some said the Alpha's bass is not 'tight' as compared to that of the Delta in an OB application.

Anyone tried the two drivers in identical OB's ?
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Old 4th December 2007, 01:29 PM   #2
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When you apply EQ to the lower Qts driver the transient response etc goes just as bad as the higher-Qts non-EQd driver.

Also I think there is more to bass quality than Qts. BL and other factors for a start, and a little bit of build quality and magic.
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Old 4th December 2007, 01:42 PM   #3
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You are right , there are a lot of factors involved in this.
The BL factor in the Delta 15A is much higher and so inherently it should damp much better. How the amp handles that is a different matter. We shall assume that all external factors apart from the driver and baffles are ideal !

Now any listening observations ?

Given a choice between an Alpha 15A and a Delta 15A , which would be a better driver to pick ? Active EQ'ing not being an issue at all. Just over all bass quality.
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Old 4th December 2007, 04:08 PM   #4
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What is the £RRP difference between the two? I guess the Delta is a bit more expensive? I would be tempted to go for the Delta as it has more BL and the lower Qts.
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Old 4th December 2007, 08:38 PM   #5
jnb is offline jnb  Australia
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No experience with the Alpha but the Delta does not sound floppy. When EQed and crossed for bass only, they sound much better that what I paid for them would suggest.
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Old 5th December 2007, 01:52 AM   #6
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The Alpha is about GBP 30/- and for the Delta it is about GBP47/-
How do you get the Pound sign ? Alt 156 or Alt 0163 don't seem to work ! The Delta looks more solid than the Alpha.
The Beta 15A isn't available.
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Old 5th December 2007, 02:00 AM   #7
tinitus is online now tinitus  Europe
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Noone tried the ToneTubby 12" Alnico yet ?

http://www.tonetubby.com/specs12a16.htm

Its in 8ohm too, if you only want one


Btw...there is a DELTA 15 LF with higher Qts


But actually I dont think the Qts is most important, I am more concerned about the relative high Fs on these drivers, which may be necessary due to the weak motor design...it might help a bit with multiple drivers

Strassacker has a KAPPA-18 with "low" Fs listed ... I havent seen it elsewhere
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