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Old 17th June 2003, 08:52 PM   #1
zcab911 is offline zcab911  United States
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Question Shallow Speaker

Is it feasible to begin with a proven pre-existing sealed-box loudpeaker design and reconfigure the enclosure dimensions so that the depth is no more than 6" while making sure that the internal volume of the enclosure is maintained?

I have been studying various books and internet material regarding the design of various enclosures.

What I would like to do is to begin with a proven sealed box crossover/driver/enclosure design and simply reshape the cabinet so that it fits more snuggly against the wall (spousal request) while maintaining a good, warm tonal quality. I have been very interested in Vienna Acoustics Waltz speaker concept (but am not married to it). Some of my thoughts have been along a shallow tower design which can be hidden in many ways using existing room furniture.

Could anyone comment on my assumptions?
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Old 18th June 2003, 12:00 AM   #2
7V is offline 7V  United Kingdom
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I've seen and heard a very impressive design called the Bandor Picture. This used a single Bandor 2" full-range drive unit and the enclosure was just 2" deep. The other dimensions were chosen to make the internal volume up to the necessary 1.5 to 2 litres.

There's no reason that this couldn't be done using two or four Bandor drivers to increase the SPL - I've considered doing this myself.

I can't think why you couldn't make your 6" design with conventional drive units.

Steve
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Old 18th June 2003, 01:01 AM   #3
zcab911 is offline zcab911  United States
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Should I be concerned about any odd acoustical effects (reflections) due to the depth (or lack of) behind the Mid/Bass speakers? I have seen mention about an ideal W/H/D ratio (I think this is called the golden ratio??), but not too much mention on how stringent this rule should be held to.
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Old 18th June 2003, 01:02 AM   #4
zcab911 is offline zcab911  United States
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Oh, and I can't find any info on the "Bandor Picture" speaker...
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Old 18th June 2003, 02:52 AM   #5
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My understanding is that the volume of air in a sealed enclosure is supposed to provide an "air spring" that is tuned for the particular driver that is mounted. The same for the various vented enclosures, except that the volume needs to be tuned to some frequency instead of some spring rate.

Theoretically, with a perfect fluid, no turbulence or a size that doesn't change due to the moving driver, only the volume and not the shape determines the tuning.

My view is that, at a practical level, the effects of shape are negligible. Otherwise, the various internal features such as braces, corners, ports, stuffing and even the driver cage would be "audible" to the well-eared.

I've also noticed that many commercially available transmission lines would be extremely thin when unfolded. Other than tuning the length of the line to right frequency, it appears that the critical dimensions are for the area of the profile. It might be possible to create a TL so thin that the driver magnet (almost) touches the back wall and making it sufficiently wide to maintain the appropriate profile area over the length. The wall could also be the sub.

Hmmm......

:)ensen.
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Old 18th June 2003, 05:42 AM   #6
asauer is offline asauer  United States
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I just became a member for this post...
and YES, box shape DOES have an affect on sound when the box is made to extreme dimensions as you have described. With a box only being 6 inches deep, you don't leave much room for mounting depth of bigger subs and it affects sound alot, I can't remember the "Golden Rule" but I'm sure alot of you know it...
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Old 18th June 2003, 07:06 AM   #7
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I will make a HUGE recommendation, that you put a deflex panel directly behind the driver on the opposing wall of the enclosure, this will rid you of any immediate problems with reflections off the back of the cabinet. I have a pair of the 6 1/2" Seas coaxes with the cocentric mounted tweeter in tiny custom fiberglass enclosures in my car. Adding a deflex panel to the back of each enclosure cleaned up the midrange a TREMENDOUS amount! I cannot recommend this enough!!!! I think you can get them from Parts Express now.
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Old 18th June 2003, 07:08 AM   #8
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I am right now using a pair of Spirit Absolute 2 studio monitors, (6.5" midbass - 45hz bottom, 1" silk tweeter, yummy) and they're wonderful, but the footprint is a bit large. If you made them 6" deep, with the current volume and porting, it would be.... strange to look at. Perhaps it would make more sense in a home-theatre setting.

If you'd like, I will get you the dimensions of everything and some pictures, but understand that driver / crossover choice is going to be tough, because these are completely custom drivers...
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Old 18th June 2003, 09:00 AM   #9
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The ratio of the dimensions in your cabinet do very much play a role in how your speaker sounds. The issue with a shallow speaker is that the reflection off the back wall of the cabinet is sooner, and has not had as much chance to be attenuated by any damping, so there is a much greater chance of this reflection being transmitted thru the cone and causing a noticeable time-smear. This can be minimized with serious absorbant or a relective surface that redirects the impinging wave away from the back of the cone (i believe this is what the deflex does).

dave
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Old 18th June 2003, 01:06 PM   #10
MadMax is offline MadMax  New Zealand
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Another problem with small depth is that other panels end up larger which means they are harder to control which means thicker panals and more bracing and damping, what about small saterlights and and sub.
Good luck Mark
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