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Old 18th December 2011, 12:47 PM   #1
Dust is offline Dust  United Kingdom
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Default 4 15 INCHERS SOUND SLOOOOW

Hi there. I'm running a bi-amped open baffle system with fostex FE207s and
two 15 inch Eminence Alphas per channel. Dbx active XO. It sounds pretty darn good, but there is always a certain slowness/ woolyness to the bass which I can't EQ out. How can I tighten things up? I am using an old intergrated amp for bass that puts out around 60 watts a channel. Do I need a much more powerfull amp? It's a 4 Ohm load so maybe the amp is struggling? I've been looking at PA amps as they seem to offer much more wattage for not alot of dollars, but I'm not sure if it would be money well spent.

Thank you.
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Old 18th December 2011, 01:48 PM   #2
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Long shot here ... maybe your crossover point is set a bit too high

Those big 15's would rather go down in octaves than come up into the mid range ... if being crossed and used as base drivers

DISCLOUSER ... I am not familiar with your speakers or OB theory and operation but ...

Try crossing the 15's one octive above the 15's minus 3db point

Again not being familar with your set up ... but if those 15's are say -3db at 25 HZs ... then try setting the crossover at 50 HZs

Had you said "Fat" "Boomy" or "Bloated" ... I would agree that parametric EQing could reduce peaks and modal ringing ... but "SLOW" makes me think crossover point is a bit high

Won't cost nothing to roll the X/O freq. down a little ... give it a try and let us know
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Old 18th December 2011, 02:23 PM   #3
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I use a single Alpha 15 per channel and xover at 80hz...... push 100watts per channel and love it. There is NOTHING "slow" about them at all. In fact they are quite "fast" for a 15" driver.

Last edited by 503Timber; 18th December 2011 at 02:27 PM.
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Old 18th December 2011, 03:02 PM   #4
Zen Mod is offline Zen Mod  Serbia
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run them in series , for test

if they're loading oldie amp too much , that will be cure

if problem stays the same , problem is in xover implementation
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Old 18th December 2011, 03:44 PM   #5
Dust is offline Dust  United Kingdom
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Hey Dhrab. I must have crossed those thing at every frequency known to man! Still can't get the clarity I'm looking for...I settled on 250hz with steepest roll off I've got (24db.) same cut off on the fostex. As for the minus 3db point, if the lowest they can produce is 46hz, then for an octave would XO point be around 90hz? I'll look into running them in series for a test.

Thanks guys for all your replies.
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Old 18th December 2011, 04:09 PM   #6
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Perhaps the open baffle is the problem?
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Old 18th December 2011, 04:23 PM   #7
BHTX is offline BHTX  United States
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Try removing the added high-pass on the Fostex, and 1st order on the Alpha's?
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Old 18th December 2011, 04:28 PM   #8
Trebla is offline Trebla  United Kingdom
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I run my 15" Eminence drivers up to 350Hz. I tried other points from 100Hz to 700Hz, but hear more detail as they are now.
Wiring in series with the full range units was also a step in the right direction.
Best to ignore convention and let your ears decide.
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Old 18th December 2011, 04:35 PM   #9
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Quote:
Originally Posted by Dust View Post
Hi there. I'm running a bi-amped open baffle system with fostex FE207s and two 15 inch Eminence Alphas per channel. Dbx active XO. It sounds pretty darn good, but there is always a certain slowness/ woolyness to the bass which I can't EQ out.
That "Slowness" is probably due to the High Q in the 15" Alphas. There's nothing that can be done. It's the characteristic of the driver itself.

Here are some articles relating to loudspeaker Q.
Attached Files
File Type: pdf LOUDSPEAKER Q.pdf (36.5 KB, 113 views)
File Type: pdf LOUDSPEAKERS PHYSICS_Q.pdf (88.9 KB, 87 views)
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Old 18th December 2011, 04:40 PM   #10
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Heavy membran and the open baffel unsufficient airload gives huge membranexcursion and will be "slow" by nature. You need better acoustic loading
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