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Old 12th January 2009, 06:07 PM   #1
Dr_EM is offline Dr_EM  United Kingdom
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Default Unusual speaker cabinet design

Hello all . I remember reading about an experimental enclosure which used many different length tubes inside of it, at least I think that was it. I believe it was produced and sold and was well regarded at the time.

I am interested in this concept, does anybody know of the design? Are there any guides for developing a DIY enclosure in a similar vein? What might the primary advatages be, I am assuming something like the tubes act as resonators and damp any peaks?

Any insight gratefully recieved
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Old 12th January 2009, 08:48 PM   #2
gedlee is offline gedlee  United States
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Personally I don't see any real advantages, just added assembly complexity. The tubes have resonances just like the box and both need to be dampened. The tubes will have the same LF resonances as the box if the total volume is the same. There is no free lunch here.
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Old 12th January 2009, 08:58 PM   #3
forr is offline forr  France
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Hi Dr EM,

It seems you think of the Hegeman cabinet.
http://www.morrisonaudio.com/morrison_history.htm

A DIY version has been described in AudioXpress by Cornelius Morton a few years ago and there are some more important details in the January 2009 issue. The impedance of the Hegeman speaker at low frequencies is very flat.
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Old 13th January 2009, 09:28 AM   #4
Dr_EM is offline Dr_EM  United Kingdom
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Thanks for your responses. It sounds like it acts a bit like a 1/2 wave closed end TL in terms of impedence at least. I was planning this type of enclosure but since the planned drivers has a low fs the pipe would need to be extremely long (5m or so!).

The AudioXpress article isn't up online so I don't know any more about the theory of it. Would the internal pipes need to be as long in the Hegeman cabinet?
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Old 14th January 2009, 03:25 AM   #5
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Greetings, all. Mr. Morton, a retired engineer (if there is such a thing), is a member of our Phoenix, AZ audio club, EMAC, or Everything Matters Audio Club. He has built several versions of this subwoofer, and we have enjoyed the fruits of his labor. The sound is indeed well damped. If you'd like, I will contact him to see if he'd like to participate in this thread
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Old 14th January 2009, 03:25 AM   #6
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http://phoenixhifi.com/Members_current_audio_syste.html

At this site is a picture of one of his woofer boxes, a straight tube with a 12" driver. The man pictured next to his system is our club president Dana Robbins.
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Old 14th January 2009, 08:23 AM   #7
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Quote:
Originally posted by Dr.EM
Thanks for your responses. It sounds like it acts a bit like a 1/2 wave closed end TL in terms of impedence at least. I was planning this type of enclosure but since the planned drivers has a low fs the pipe would need to be extremely long (5m or so!).

The AudioXpress article isn't up online so I don't know any more about the theory of it. Would the internal pipes need to be as long in the Hegeman cabinet?
I have one of these in the design phase. Very generally, the tubes lengths are selected to bracket Fs.
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Old 14th January 2009, 10:10 AM   #8
Dr_EM is offline Dr_EM  United Kingdom
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Thanks for the replies! I should be more clear on my application, the woofers in this system (Hi-Vi M8a) are being implemented with the expectation that subwoofers will be added. Deep bass response from them is not required especially. The bass response they give in sealed boxes is ideal.

I hope I'm right in assuming these boxes are closed and ultimately produce similar rolloff to a closed box and limit excursion naturally?

The aims of the box are mainly to give a very flat response up to 800hz or so where the driver is crossed over. I was attracted to the 1/2 wave TL as it would offer this and also impedence flattening which I would like. I realised a half wave pipe would be 5.2m long though for this driver and that was a bit off putting! I know it could be folded and tapered (perhaps even 20/1 since there's no vent noise to consider) but remembered this type of box and hoped it might be an alternative.

Any ideas on pipe diameters and numbers of pipes typically used?
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Old 14th January 2009, 10:40 AM   #9
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I don't understand the concept. Are there different length tubes inside the box with one end closed? How does this work?
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Old 14th January 2009, 02:14 PM   #10
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The latest aXp has a letter to the editor with more detail on pipe calculation.

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