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Old 24th September 2007, 05:41 PM   #1
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Default Please comment on my "built-in" subwoofer idea

Hi All,

A friend recently had a bad experience with a custom "built-in" entertainment center. It was a lot of money, and the builder didn't measure properly, so the thing wouldn't fit. I went over to his house and had a look at how the cabinet was put together. I'm in the middle of the planning phase for a pair of dipole subwoofers, but seeing the entertainment center made me realize that I might be able to DIY this thing as well.

I have a moderately sized family room, measuring 12 ft x 12 ft. One end opens into the kitchen. On an adjacent wall, there is a cutout or niche for an entertainment center. This space measures 2 ft deep, 5 ft wide, 8 ft tall.

The wife has learned of my plans and indicated concern over having 1-2 subwoofers populating the family room, and perhaps being out of place with her concept of decor.

So, putting 2 and 2 together, and perhaps coming up with 22, I sketched 3 concepts to explore.

I'll describe the first one in this post. I've posted a crude pencil sketch, but it should be adequate to show the idea.

The idea is to use the lower two feet of the niche for subwoofers, in this case an H-frame dipole.[list] - Lower two feet of niche used for subwoofers
- Two H-frame subwoofers - could use W-frames if need be
- Enclosure is not anchored to walls or remaining cabinetry
- Curved interior panel to direct sound out into room
How should I expect this design to perform?
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Old 24th September 2007, 05:45 PM   #2
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Default 2nd Concept - U frames

Hi All,

Here's the second concept, which places 2 U-frame dipole subs in the same space. Sorry about the crude sketch...

Oh, BTW, the drivers are Peerless 830845's.

The idea is to use the lower two feet of the niche for subwoofers, in this case an H-frame dipole.
  • - Lower two feet of niche used for subwoofers
    - Two U-frame subwoofers
    - Enclosure is not anchored to walls or remaining cabinetry
    - Curved interior panel to direct sound out into room, but tighter radii than with U-frame case
    - Cloth grill to conceal drivers

How should I expect this design to perform?
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Old 24th September 2007, 05:53 PM   #3
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Default 3rd concept - Hegeman style sub

And the 3rd concept.....

This is adapting a Hegeman / Morrison style sealed subwoofer to use the available space optimally. A great article was written on this subwoofer design by Cornelius Morton in 12/2003 "Audio Xpress".

The little golden books version is that this design uses multiple tuned pipes to flatten out the impedance curve broadly over the subs frequency range of operation.
  • - Wildly complicated enclosure, relative to a dipole
    - Much easier to equalize and integrate, relative to dipole subs
    - Uses fewer expensive drivers
    - May only need 1, rather than 2 subs
    - Uses space in lower half of media niche
    - Not physically bolted to wall or remaining cabinetry

I may build this design and one of the dipole designs to compare. The plan for all of these is to integrate via a DCX2496.

What do you all think?
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Old 25th September 2007, 09:27 AM   #4
tomp787 is offline tomp787  United States
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Default "built in" cabinets

Hello Rob,

I've always liked built in cabinets so I think you should give it a try. Built in cabinets were popular in the 1950s and 1960s. Jensen published some articles and plans which would give you another place to look for ideas. The Jensen Transflex is discussed in this forum as the tapped horn. It would make a good subwoofer. Another cabinet from Jensen is the built in version of their Imperial. I have used the built in Imperial with Altec 605 and enjoyed it. Let me know if you can't find the Jensen plans and I will send them to you.

Finally I suggest you look at infinite baffle enclosures. This is another great old idea.They have the smallest visual impact but they require a large adjacent space like an attic, crawlspace or closet to use as the enclosure. Your wife may like them particularly if you show her the refrigerator sized Imperial first. They are described here:

http://ibsubwoofers.proboards51.com/

Tom
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Old 26th September 2007, 06:11 PM   #5
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Default Re: "built in" cabinets

Quote:
Originally posted by tomp787
I've always liked built in cabinets so I think you should give it a try. Built in cabinets were popular in the 1950s and 1960s. Jensen published some articles and plans which would give you another place to look for ideas. The Jensen Transflex is discussed in this forum as the tapped horn. It would make a good subwoofer. Another cabinet from Jensen is the built in version of their Imperial. I have used the built in Imperial with Altec 605 and enjoyed it. Let me know if you can't find the Jensen plans and I will send them to you.
Thanks, Tom. I appreciate the encouragement. I'm going to try to design this such that they can be placed into the space, or moved out into the room.

Those Imperials are seriously large!

Regards,

Rob
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Old 28th September 2007, 05:28 AM   #6
tomp787 is offline tomp787  United States
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Hello again Rob,

I think the point of a built in system is to use the room boundaries as part of the design. So a built in system will not sound the best out in the room.

The built in Imperial may be large but it is the perfect size for your niche as it is 5 feet wide x 2 feet deep x 3 feet high. Since it is 3 feet high and 2 feet deep it can be replaced with kitchen base cabinets. You won't need two - one will fill your house with music.

So I suggest you change your plan to use the 36" kitchen base cabinet height for the speaker boxes. The you can build your dipole, Hegeman, and add some other fun ones like back loaded horn (Imperial), tapped horn and a push-pull design like djk's or the triple chamber bandpass JBL. (I would use a 15 or 18 inch driver for a woofer but you should use whatever you like.) Then if you have tried all those and are still not happy you can put cabinets in the bottom space and build an infinite baffle system in the attic.

Tom
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