(Complicated) Guitar Cab Tuning Question - Page 2 - diyAudio
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Old 4th November 2009, 05:52 PM   #11
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ok that's what I thought
I read that acoustic foam helps absorb standing waves, cleaning up the sound, that's why I got it.
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Old 4th November 2009, 06:10 PM   #12
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Charles's law - Wikipedia, the free encyclopedia
Boyle's law - Wikipedia, the free encyclopedia

The stuffing supposedly soaks up temperature changes.
So you are only fighting one ideal gas law, and not both...
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Old 4th November 2009, 06:26 PM   #13
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I see what they're talking about.
Well I've done all my calculations, I have a volume of 2ft^3 after I take out speaker displacement, inductor, wood, and foam volume. So I end up needing 2 ports that are 2.75 in dia and 5 in deep.

So now I need to decide if i'm put them in the front or back. I'm afraid that if they're in the back the bass wont be as punchy.
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Old 4th November 2009, 07:09 PM   #14
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Irrelevant, cause ports don't punch. Cones do.
Your cones is located on the front, yes???

Assuming system is tuned punchy (Q <= 1)...
I mean, you still gotta tune your box not too
mushy for the driver to have punch. But port
placement??? Really nitpicking.

I'd shave an inch off the lower back. And hope
maybe the corner of the wall and floor will give
me a little horn loaded boost.

Keep the cutoff. If you later discover you need
to block off part of the vent. Screw it to the
bottom (on the inside) and abuse to adjust.

--------------------------

Also your circuit might be flipping over phase
around the crossover frequency? I don't know
your crossover circuit, is it more than just a
choke coil?

Tried seeing what happens if you deliberately
miswire woofs out of phase with the MOWs?
Sometimes that fixes phase, sometimes not...

Last edited by kenpeter; 4th November 2009 at 07:21 PM.
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Old 4th November 2009, 11:08 PM   #15
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ditch the acoustic foam and the inductor, this is a guitar amp.
If you can't get the sound you need from your AMP controls, this is where the problem lies...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 4th November 2009, 11:53 PM   #16
rcw is offline rcw  Australia
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This type of box is a part of a musical instrument and not intended to reproduce sound, look on it as the body and sound hole structure you find in a bass viol.

Bass guitar boxes in general have a 60Hz. punch peak, and you will find the typical bass guitar driver is uptimised for this. In general it is best to design the box for the formant you want, then tweak the tone controls.

Having a steep high pass filter about an octave lower than this is also advisable since bass guitars produce a very large d.c. component that causes a large cone offset, and this can be greatly increased by the technique of damping the strings with the hand.
The effect of this offset is to soak up large amounts of power and produce no more sound.
rcw.
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Old 4th November 2009, 11:59 PM   #17
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Quote:
Originally Posted by rcw View Post
This type of box is a part of a musical instrument and not intended to reproduce sound, look on it as the body and sound hole structure you find in a bass viol.

Bass guitar boxes in general have a 60Hz. punch peak, and you will find the typical bass guitar driver is uptimised for this. In general it is best to design the box for the formant you want, then tweak the tone controls.

Having a steep high pass filter about an octave lower than this is also advisable since bass guitars produce a very large d.c. component that causes a large cone offset, and this can be greatly increased by the technique of damping the strings with the hand.
The effect of this offset is to soak up large amounts of power and produce no more sound.
rcw.
the whole idea of the cab was to have a biamped/biwired cab.
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Old 5th November 2009, 12:02 AM   #18
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Quote:
Originally Posted by kenpeter View Post
Irrelevant, cause ports don't punch. Cones do.
Your cones is located on the front, yes???

Assuming system is tuned punchy (Q <= 1)...
I mean, you still gotta tune your box not too
mushy for the driver to have punch. But port
placement??? Really nitpicking.

I'd shave an inch off the lower back. And hope
maybe the corner of the wall and floor will give
me a little horn loaded boost.

Keep the cutoff. If you later discover you need
to block off part of the vent. Screw it to the
bottom (on the inside) and abuse to adjust.


So put the ports on the back panel towards the edges? And I'll switch the + & - on the basslites and see if that helps

--------------------------

Also your circuit might be flipping over phase
around the crossover frequency? I don't know
your crossover circuit, is it more than just a
choke coil?

Tried seeing what happens if you deliberately
miswire woofs out of phase with the MOWs?
Sometimes that fixes phase, sometimes not...
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Old 5th November 2009, 12:34 AM   #19
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You could try removing just the cap, running the MOW`s fullrange, then you`ll get more bass.
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Old 5th November 2009, 03:35 AM   #20
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Quote:
Originally Posted by Peter M. View Post
You could try removing just the cap, running the MOW`s fullrange, then you`ll get more bass.
from what I've read, that would give a funky load that the amp would see, you need to have the cap and induc as close to the same frequency as possible
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