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Old 15th January 2008, 10:00 PM   #1
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Default Speaker design questions: dimensions

I am considering building my first set of speakers: a 2.1 system for one of the rooms in my apartment. However, I would like to deviate from the suggested speaker enclosure dimensions. Specifically, I would like to make the speakers slimmer in depth than the "acoustic" ratio or even the golden ratio (and perhaps make the speakers wider to compensate for the lost volume).
What are the acoustic implications of less depth in the enclosure? Will this emphasize a higher frequency? Lower? Will the effect be overwhelming if the speakers are too slim? Or does the sound depend more on cabinet volume?

Also, my idea as of now is to team up a pair of speakers with a small subwoofer to fill in the lower end of the spectrum. What should I take into consideration beyond my modified cabinet design? I have a couple speaker building books to guide me through driver selection and whatnot.

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Old 15th January 2008, 10:17 PM   #2
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The only issue really is the increased chance of reflections back through the cone by the closer rear wall and less damping material inbetween. The wide baffle is favoured by those wanting a natural sound as it promotes wavelaunch and negates the need for baffle step correction in a lot of cases.
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Old 16th January 2008, 06:17 AM   #3
Svante is offline Svante  Sweden
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Apart from the effects on the box volume, the depth of the box has very little effect on the frequency response. The baffle width, on th other hand has quite some effect on the frequency response. I would suggest to alter the box height instead if possible.

How much do you want to change the dimensions?
Simulate loudspeakers: Basta!
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Old 16th January 2008, 06:49 AM   #4
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Should I compensate for the lost volume by making the enclosure wider/taller? Aside from careful driver selection, is there anything else I should consider?
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Old 16th January 2008, 06:49 AM   #5
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I am looking to reduce the depth to about 0.65 times its original value. So, assuming the base ratio is 0.79 : 1 : 1.26 (I haven't thought out what a good height/width would be yet...), the depth would become fairly slim compared to the height and width.

In absolute terms, the speakers I am thinking of aren't too large, maybe 12 inches in height? Let's say the depth is 5.5 inches (which is the area I am planning on, so long as it isn't too outrageous), should the speaker be any taller than 12 inches?

The reason for the slim speakers was mostly for better looks, would the dimensions I am throwing around be too ridiculous?
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Old 16th January 2008, 06:50 AM   #6
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...You'll have to excuse me, I get too used to the US using these ridiculous units.

when I said 12 inches I meant: 30.5 cm
5.5 inches: 14 cm
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Old 16th January 2008, 07:31 AM   #7
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volume is the most important thing, it has to remain constant. if you alter any of the dimensions you have to compensate with the others until the internal volume of the speaker is restored.

internal dimensions affect internal resonances with some shapes (golden ratio etc) being better in that respect and others (column shape) being worse but ultimately any shape's performance can be improved with the right acoustical damping materials.

width of the speaker will have a direct effect on frequency response so once you change the width it is no longer the same speaker you're building. if you're following some kind of an established design you will want to keep width constant too ( the other thing you're keeping constant is volume ).

overall height of the cabinet will not have that much effect (assuming the inside of the speaker is well damped) on sound as long as you dont change the height of speaker itself within the cabinet (relative to the floor). the speaker itself should remain at the same height that the original design called for (assuming the original design was a floor standing model) but the top of the cabinet may move up if you want.
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Old 16th January 2008, 10:12 AM   #8
sreten is offline sreten  United Kingdom
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Default Re: Speaker design questions: dimensions

Originally posted by sfhseric06

I have a couple speaker building books to guide me through driver selection and whatnot.

No doubt that where you got all the guff about ideal dimensions ......
The way to do it is a well designed, tested and documented project.

The purpose of your cabinet shape is not explained. If it is for wall
mounting note that this does restrict the sort of imaging and midrange
neutrality available from small standmounters, one of the powerful
arguments for a satellite / subwoofer solution.

It is personal opinion but the shape you describe does not look
better when placed away from room boundaries, it does look
better if placement is restricted near a boundary.

As you are using a subwoofer then it is very likely you can take
a vented design and convert it to sealed by reducing depth.

If you are considering near boundary placement one of Zaph's reduced
baffle step options in his designs may suit, but as he freely implies you
are likely throwing out the bay with the bathwater .....

Checkout : at - http://www.zaphaudio.com/

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Old 16th January 2008, 09:03 PM   #9
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Thanks for all of the tips, I appreciate it.

I will most likely be placing these speakers on stands on the sides of my desk, so they will be near the wall.

Thanks again. Perhaps I will post a reply once I finalize a design.
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Old 16th January 2008, 09:38 PM   #10
Byrd is offline Byrd  South Africa
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Originally posted by vasyachkin
volume is the most important thing, it has to remain constant. if you alter any of the dimensions you have to compensate with the others until the internal volume of the speaker is restored.
I think you are discounting certain types of enclosures where the dimensions and position of the speakers is just as important.
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