(Complicated) Guitar Cab Tuning Question - diyAudio
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Old 4th November 2009, 04:51 AM   #1
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Default (Complicated) Guitar Cab Tuning Question

Ok, I built a guitar cab and have run into a problem, I need some opinions on how to tune the bass part of the cab. I made it completely sealed and with two compartments inside, top for highs, bottom for lows.
The speakers resonance frequency is 48hz so I would like to aim for that if possible (and unless it will muddy up the sound too much)

Here are some pics of the cab, you'll see what i'm talking about
Image hosting, free photo sharing & video sharing at Photobucket

The bass is way too quiet, especially since the Man O' Wars have a 5db higher SPL. So I want to port it. The only spots are in between the speakers, in the middle vertical of each other as you can see. I can fit a 3" diameter port on top and bottom, and if I had to I could squeeze in a 2" diameter in the bottom left and right, or some kind of combo of them all.

The internal dimensions of the box are 13⅜"h x 28"w x 11⅜" deep = a volume of 2.5 ft^3
The bracing is " h x 1" w and has a total length of 106" = a volume of .069 ft^3
So the volume of the box would be 2.431 ft^3

I need to know how I would calculate the volume of the 1" foam, the inductor, and the front loaded drivers (baffle wood is " thick)

Here are the specs of the drivers:
http://eminence.com/bassguitar_speak...2&SUB_CAT_ID=5

There are two drivers (obviously) so the port will have to be tuned for 300w.

I know it's a lot of stuff to comprehend, but that's why I'm here on DIY Audio.

Just tell me if I forgot to post some information, or have any comments on the cab too.
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Old 4th November 2009, 10:42 AM   #2
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Best thing would be to reference your drivers and post new/better links because those don't seem to work.
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Old 4th November 2009, 12:04 PM   #3
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Is this a bass guitar? If not surely you don't need tuning down to that frequency. Most of the guitar cabs I have come across are either sealed or open back, with the sealed giving slightly more weight to the sound.
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Old 4th November 2009, 02:54 PM   #4
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UPDATED
----------------------------------------

Ok, I built a guitar cab and have run into a problem, I need some opinions on how to tune the bass part of the cab. I made it completely sealed and with two compartments inside, top for highs, bottom for lows. Crossed over at 330hz
The speakers resonance frequency is 48hz so I would like to aim for that if possible (and unless it will muddy up the sound too much)

Here are some pics of the cab, you'll see what i'm talking about
Pictures by andrew-skaterrr - Photobucket

The bass is way too quiet, especially since the Man O' Wars have a 5db higher SPL. So I want to port it. The only spots are in between the speakers, in the middle vertical of each other as you can see. I can fit a 3" diameter port on top and bottom, and if I had to I could squeeze in a 2" diameter in the bottom left and right, or some kind of combo of them all.

The internal dimensions of the box are 13⅜"h x 28½"w x 11⅜" deep = a volume of 2.5 ft^3
The bracing is ¾" h x 1½" w and has a total length of 106" = a volume of .069 ft^3
So the volume of the box would be 2.431 ft^3

I need to know how I would calculate the volume of the 1½" foam, the inductor, and the front loaded drivers (baffle wood is ¾" thick)

Here are the specs of the drivers:
Eminence - The Art and Science of Sound

There are two drivers (obviously) so the port will have to be tuned for 300w.

The main question is: How do I calculate the volume of the foam, inductor? (I think I know how to do the front loaded drivers.)

I know it's a lot of stuff to comprehend, but that's why I'm here on DIY Audio.
Just tell me if I forgot to post some information, or have any comments on the cab too.
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Old 4th November 2009, 02:57 PM   #5
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Quote:
Originally Posted by ianpengelly View Post
Is this a bass guitar? If not surely you don't need tuning down to that frequency. Most of the guitar cabs I have come across are either sealed or open back, with the sealed giving slightly more weight to the sound.
I wanted to make a metal guitar cab that could handle the low tunings. Most guitar speakers drop off around 75hz. Also I can use it as a bass cab when my bassist comes over. He loves the sound he gets.
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Old 4th November 2009, 04:06 PM   #6
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The volume added by having front loaded speakers is .0941 ft^ so internal volume = 2.5251 ft^3
then I measured and think I have the inductor volume: .0039 ft^3 = 2.5212ft^3 total.
foam volume = .3745 ft^3 = 2.1467 ft^3
If i round down to take the wire volume into account then I get 2.14 ft^3 as the total volume of my box, now i can calculate the ports
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Old 4th November 2009, 05:00 PM   #7
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You can put stuffing in the lower half to make it adiabatic
(less temperature change with pressure), behave perhaps
as much as 15% larger inside, some claim 15% anyways...
But don't do that to the MOWs up top. Leave that part of
the cab hard, empty, and reflective inside.

You can port the bottom of the backside... Bass ports
won't care which side they are on, as long as you don't
push the back flat up against a padded studio wall.

Looks like your coils are strung in series (8+8=16 ohms)?
If so, have you accounted for this in your crossover?
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Old 4th November 2009, 05:18 PM   #8
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Quote:
Originally Posted by kenpeter View Post
You can put stuffing in the lower half to make it adiabatic
(less temperature change with pressure), behave perhaps
as much as 15% larger inside, some claim 15% anyways...
But don't do that to the MOWs up top. Leave that part of
the cab hard, empty, and reflective inside.

You can port the bottom of the backside... Bass ports
won't care which side they are on, as long as you don't
push the back flat up against a padded studio wall.

Looks like your coils are strung in series (8+8=16 ohms)?
If so, have you accounted for this in your crossover?


so what you're saying is take the foam out of the top and put it in the bottom?
and yes, I have it in series/parallel. drivers are in series, top and bottom are paralleled, i had to do it this way to get a good load and to use my crossovers
I did take the 16ohm load in consideration with the inductor/capacitor
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Old 4th November 2009, 05:20 PM   #9
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i used acoustic foam as you can see in the pics. is that ok?
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Old 4th November 2009, 05:46 PM   #10
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No, I'm talking about polyester pillow stuffing that can breathe, absorb and
release heat as pressure waves travel through it. That makes the cabinet
appear bigger inside, or so the theory goes...

I don't think your eggcrate type foam does much for enlarging an enclosure,
it only deadens the wood. Which is OK in the bass part of the cab, but not
the upper part, unless bass is making the whole cabinet rattle....
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