Potential issues with long, thin boxes? (With pictures!)

Spasticteapot · 22nd January 2007, 07:17 AM

I'm working on a pair of enclosures made out of 6" PVC pipe for some 5.25" drivers. They'll just barely fit on the baffle, but I think that the rounded design may actually help acoustically. (That said, I have not the foggiest idea.)

I'm worried, though, that such a narrow enclosure (roughly 5" deep) could have reflection problems. Any suggestions?

Spasticteapot · 23rd January 2007, 07:13 AM

Anyone?

blank527 · 23rd January 2007, 07:33 AM

Hi,

Dampening the cabinet would be in my opinion the best possible.
Here is a site that has sort of the same design.
Not optimal though.

Greetz,
Remco

PeteMcK · 23rd January 2007, 08:41 PM

Hi Spastic,

I did something similar with 4" drivers (TL with baffle down the middle & Karlson type slot at termination); I think the rounded rear pipe helps reduce relections significantly , so much so that every time I see something drum shaped I wonder if it can be turned into a speaker cab... The resonance probs I had came from the other dimension, along the length of the pipe (I just padded each side of the baffle).

Cheers, Pete McK

owdi · 23rd January 2007, 10:23 PM

What's the fs of the 5.25" woofer? You may be able to do a stuffed TL.

Dan

Spasticteapot · 23rd January 2007, 10:57 PM

Quote:

Originally posted by owdi
What's the fs of the 5.25" woofer? You may be able to do a stuffed TL.

Dan

About 50hz.

I was thinking as much - it would make for some very simple speakers, and I've got tons of parts.

Plus, mounting the baffle at a slight angle might help with this, though I have no idea as to how I would go about it.

Eusebius · 23rd January 2007, 11:05 PM

going back to the original 6" pipes, isn't it possible to get a T junction so you get a round opening pointing forwards, into which you put the speaker? You could position this so as to get a quarter wave pipe, no?

Wondering about doing something similar with a Monacor 130AL unit which is a pretty good full range option. I have it in a reflex enclosure right now. Andy

454Casull · 24th January 2007, 12:20 AM

The diffraction will be pretty severe.

http://www.trueaudio.com/st_diff1.htm

Spasticteapot · 24th January 2007, 01:01 AM

Quote:

Originally posted by Eusebius
going back to the original 6" pipes, isn't it possible to get a T junction so you get a round opening pointing forwards, into which you put the speaker? You could position this so as to get a quarter wave pipe, no?

Wondering about doing something similar with a Monacor 130AL unit which is a pretty good full range option. I have it in a reflex enclosure right now. Andy

Not really. First, you run into baffle issues; second, they look awful and won't balance properly, and third, 6" PVC joints cost $12/each. (The PVC pipe was $2/ft.) I've tried it with 4" PVC pipe and some other drivers; the results were less than satisfactory.

According to my plans, I'll have 5" from the back of the baffle to the back side of the tube. I'll be using a 1" thick baffle, too, which might help a bit. Some good results were had by a Parts Express boffin using 7" woofers in 8" tubes - I'm using 5.25" woofers in 6" PVC.

Also, I could add the baffles at an angle, which would cause them to fire down to a greater degree, and might cut down on resonance a bit. I just switched to Linux (and hence have no SketchUp to model it on,) but you can see the general idea here:

http://t-linespeakers.org/projects/chris/index.html

My lametastic calculations tell me I'll need 1.9 meters (about six feet) of pipe to get a 50hz resonance, but I figure that, by stuffing, I can drop that to about four and a half feet.

Quote:

Originally posted by 454Casull
The diffraction will be pretty severe.

http://www.trueaudio.com/st_diff1.htm

I'm hoping that because the driver is rounded in the back with only a flat face for the driver, I can get sphere-like diffraction - I.E; not much.

That's the other big problem with the 90-degree bends: You get ridiculously awful baffle step diffraction. My method is intended to help reduce it, at least a bit.

Hezz · 24th January 2007, 04:13 PM

This type of enclosure has severe problems with internal standing waves and the enclosure acting like a one note resonator. This can be dealt with by heavily stuffing the inside of the enclosure. It needs to be overdamped which will kill the bass response.

From the perspective of the outside of the cabinet the shape may be useful.

If you are trying to make TL then it can work if you get the length right.

22nd January 2007, 07:17 AM	#1
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Potential issues with long, thin boxes? (With pictures!) I'm working on a pair of enclosures made out of 6" PVC pipe for some 5.25" drivers. They'll just barely fit on the baffle, but I think that the rounded design may actually help acoustically. (That said, I have not the foggiest idea.) I'm worried, though, that such a narrow enclosure (roughly 5" deep) could have reflection problems. Any suggestions?

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23rd January 2007, 07:13 AM	#2
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Anyone?

23rd January 2007, 07:33 AM	#3
blank527 diyAudio Member Join Date: Nov 2001 Location: Haarlem	Hi, Dampening the cabinet would be in my opinion the best possible. Here is a site that has sort of the same design. Not optimal though. Greetz, Remco

23rd January 2007, 08:41 PM	#4
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Sydney	Hi Spastic, I did something similar with 4" drivers (TL with baffle down the middle & Karlson type slot at termination); I think the rounded rear pipe helps reduce relections significantly , so much so that every time I see something drum shaped I wonder if it can be turned into a speaker cab... The resonance probs I had came from the other dimension, along the length of the pipe (I just padded each side of the baffle). Cheers, Pete McK

23rd January 2007, 10:23 PM	#5
owdi diyAudio Member Join Date: Sep 2003 Location: Bellevue, WA	What's the fs of the 5.25" woofer? You may be able to do a stuffed TL. Dan

23rd January 2007, 11:05 PM	#7
Eusebius diyAudio Member Join Date: May 2006	going back to the original 6" pipes, isn't it possible to get a T junction so you get a round opening pointing forwards, into which you put the speaker? You could position this so as to get a quarter wave pipe, no? Wondering about doing something similar with a Monacor 130AL unit which is a pretty good full range option. I have it in a reflex enclosure right now. Andy

24th January 2007, 12:20 AM	#8
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	The diffraction will be pretty severe. http://www.trueaudio.com/st_diff1.htm

24th January 2007, 04:13 PM	#10
Hezz diyAudio Member Join Date: Dec 2002 Location: Utah	This type of enclosure has severe problems with internal standing waves and the enclosure acting like a one note resonator. This can be dealt with by heavily stuffing the inside of the enclosure. It needs to be overdamped which will kill the bass response. From the perspective of the outside of the cabinet the shape may be useful. If you are trying to make TL then it can work if you get the length right.

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