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Old 8th October 2007, 06:21 PM   #11
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Will the inferior wood cause any loss of performance? If so, what does that translate to in measurable terms (non audiophile)?

Well I guess by inferior wood you are refering to it "bending" or not being too stiff. Now remember you will have pressure inside the cabinet, lets say it will be a sealed cabinet, so a 15" woofer moving inside it will compress the air inside like a spring and then release going forward, if the wood is not stiff it will "blow" like a balloon. How does this affect sound, first of all you will loose force in the "spring" of the cabinet and second you will have a big surface moving. Most 15" drivers really move one mm or less while playing and they give good output becuse of the big area of the cone, now if you have a huge side of the cabinet moving less than a milimeter, it will give out sound, mainly distortion.
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Old 8th October 2007, 06:22 PM   #12
ppia600 is offline ppia600  United States
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I would think the box you are buying would be 3/4" mdf. That shouldn't be a problem. Some guys will of course tell you to go with thicker mdf or a different wood type, but thicker stuff can definately get heavy. If the box isn't at least 3/4" don't get it.
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Old 8th October 2007, 06:26 PM   #13
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Quote:
Originally posted by groover1234


haha so it is... please excuse my late night literacy skills.



In which case, assuming the wavelength at 45hz would be in excess of 7 metres, how then would any box size effect the output of the speaker apart from the amount of compression and possibly a cumulative increase in pressure? or have I misunderstood you.

Bracing myself...I don't claim to know anything so please be gentle

Well, the air mass in the box works by providing an impedance, so to speak, to which the moving cone works. That way, the cone movement is damped. There's a lot more to it, why you need a specific volume with a speaker with given properties like cone mass and resonance frequency.
The other thing is when exactly half a wavelength fits between two walls, then you get a kind of reinforment, the wave is bouncing between the walls and because the walls are half a wave apart, it starts to reinforce itself.
So, these are two completely separate things.

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Old 8th October 2007, 06:38 PM   #14
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Quote:
If the box isn't at least 3/4" don't get it.
I'd say its a chipboard or something. Doesn't look like MDF and doesn't say that it is either way.

What is the difference between having a box made out of MDF and chipboard? Does it alter the sound?
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Old 8th October 2007, 06:40 PM   #15
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the wave is bouncing between the walls and because the walls are half a wave apart, it starts to reinforce itself.
The reinforcement provides what additional benefit? Does it reduce the load on the speaker?

Thanks.
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Old 8th October 2007, 10:44 PM   #16
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To do the calculation is easy, it is 1/2ab so if the box is 30cms deep at the top and 40cms deep at the bottom and it is 30cms tall and 80cms long your calculation will be to separate the triangle from the equation so it would go 30 x 30 x 80 = 72L then you do the triangle so it is 1/2ab so that is 5 x 30 x 80 = 12L then add them together and you would get 84 litres...
Also 1Cuft is 28.3 litres if that is of any help.
So remember 1/2ab it is as simple as that.....

I hope that this helps some....
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Old 17th October 2007, 01:19 PM   #17
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just a follow up on what I found in case someone is looking at this in the future:

I have a compressed cardboard dual 12" box that my old 900W Earthquake subs were in. I found this local business (Sub Sonic Pro) who manufactures their own custom box design locally. It apparently reduces/ eliminates 'standing waves'.

Basically there's no flat reflecting surface, everything has some form of angle to it. They are made from 18mm MDF and are carpeted with no internal dampening.

I did a side by side comparison of the same sub in my 12" box and one of their boxes using a sweep track. I was astonished at how much of a difference it makes. Whether its because the boxes are "tuned" to a lower note I dont know but I really liked what I heard.

There was none of that harmonic overtone ringing sound that I would hear when pushing the compressed cardboard standard angular design.

Both boxes were similar in thickness but significantly different in shape.

Another thing I noticed was that the sub didn't seem to work as hard in the MDF box and could go much louder before starting to struggle.

I took it a step further and was able to take them home and I hooked them up to a sine wave in an additive synthesis (Reason with the Subtractor for those interested) and proceeded to go up the keys from ultra low.

I had them hooked to my Kenwood 200W RMS hifi amplifier so not as good of a test but I wasn't having it loud. I used Speaker A and Speaker B to switch between the both and a very careful ear.

I noticed that the compressed cardboard box had loud notes and quiet notes yet the MDF box was a lot smoother. At very low frequencies the cardboard box "warbled" and the MDF box sounded tight and clean.

Overall, I've been extremely impressed with the difference a good box makes.
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Old 18th October 2007, 03:45 AM   #18
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Weren't you wanting to know how to calculate the volume of the enclosure????
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Old 18th October 2007, 04:57 AM   #19
dnsey is offline dnsey  United Kingdom
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Will the inferior wood cause any loss of performance? If so, what does that translate to in measurable terms (non audiophile)?
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Old 18th October 2007, 04:58 AM   #20
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Quote:
Originally posted by groover1234

I found this local business (Sub Sonic Pro) who manufactures their own custom box design locally. It apparently reduces/ eliminates 'standing waves'.

Basically there's no flat reflecting surface, everything has some form of angle to it.

Hi,
Typically, standing waves are not an issue in a sub enclosure, as the wavelength of the frequencies involved are larger than the box dimensions.
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