Triangle-pyramid shaped speakers

kneadle · 22nd December 2002, 09:40 PM

Hello, I'm a true newbie to DIY speakers, and I did a search for the term "Pyramid." If you can direct me to where this has been discussed before, I'd much appreciate it.

I inherited a pair of triangle pyramid cabinets that were designed for a 10" woofer and a 3 1/2" driver for high frequencies. In the course of history, they were modified to hold two 5 1/2" drivers. The drivers were destroyed by a little brother's ignorant thumb (Augh!). There were no other electronics inside.

I'll give you the measurements, then describe what I'd like to do.

It's built with 3/4" presswood of some sort.

inside height from middle bottom to top peak is 14"
the length of each joint is 16"
According to V=1/3Bh, that comes to roughly 520 cu. in. right?
520 cu. in. comes to .3 cu. ft. or 8.5 liters

I went to Parts Express to search for parts (go figure) which might make these speakers into a nice 2-way system for about $200 or so. I'd like to replace the front-panel with a substantial Vifa driver (P21WO-20) that has decent frequency response so that with a decent tweeter (D27TG-05) the system might cover the whole range without a big dip somewhere in the midrange.

Firstly, is that a decent proposal? That's an 8" woofer in an enclosed configuration. I could go to 6 1/2", but I want that bottom end if at all possible.

Secondly, I haven't got a clue as to crossover configuration. I can solder and I understand impedance and capacitance, etc., but can I just buy one designed to crossover at 2500 or 3000 Hz? That would make my life much easier.

BTW, I'd like to see a discussion of the benefits of an equilateral pyramid as far as the whole "parallel surfaces" thing is concerned. No ports or anything, either. Hmm...

Thanks!

jleaman · 22nd December 2002, 09:46 PM

Can you post a pic of some how. ?

kneadle · 22nd December 2002, 09:59 PM

Will this work?

kneadle · 22nd December 2002, 10:03 PM

You can kinda make out where the 3 1/2" driver went. The 10" filled up most of the remaining panel.

planet10 · 23rd December 2002, 12:30 AM

Actually that looks like a tetrahedron... beauty.

You might actually get more bass from a 6" driver in such a small box. Personally i like an even smaller midbass (and add a sub later). A Vifa P13 perhaps.

dave

kneadle · 23rd December 2002, 12:50 AM

yes, tetrahedon. That's the shape. I said "triangle" to get that across. I'll do a search for tetrahedon now!

I'd like some more input, though. I'm sure I can learn a lot about why the 6" has better low-end response in this thing.

SkinnyBoy · 23rd December 2002, 01:17 AM

Are there any benifits in using that shape enclosure for ported speaker boxes? I ask cos I am doing woodwork next year and would like to make some speakers... ported, using 6inch Response speakers (from jaycar) and am not sure if the teacher will allow me to make just simple rectangular prism boxes..

ALSO!!!!! while I am here... how do the ReSponse 6inches compair to the Vifa P17WJs (sorry, couldn't find a link to info on them..

)

planet10 · 23rd December 2002, 01:26 AM

Quote:

Originally posted by SkinnyBoy
Are there any benifits in using that shape enclosure for ported speaker boxes?

This box has no parallel sides. It should be a decided improvement over a rectangular box.

dave

planet10 · 23rd December 2002, 01:33 AM

Quote:

Originally posted by kneadle
I'd like some more input, though. I'm sure I can learn a lot about why the 6" has better low-end response in this thing.

An 8 generally will need a bigger box than a 6. If you put a speaker in too small a box you end up with a high Q -- a big bump in the response which doesn't sound good. The smaller driver, with its requirement for a smaller box could well have a more realistic Q.

dave

kneadle · 23rd December 2002, 02:18 AM

Hmm. I tried all the calculating I could understand with pebox, and it seemed like the 8" I picked out could fit in a .3 cu. ft. box.

Maybe Im ignorant, though. That's why I'm here.

Oops! Upon double checking, I see that I was wrong! The 6 1/2" P17WO-20 (for skinnyboy: http://www.partsexpress.com/pe/showd..._ID=7856&DID=7 )

is actually made for a .28 cu. ft. sealed configuration, the size of my box within 2/100ths.

But that's my next question: Is a tetrahedron actually behaving like a .30 box or like a 1.0 cu. ft. box? Do you get my drift??

22nd December 2002, 09:40 PM	#1
kneadle diyAudio Member Join Date: Dec 2002 Location: Buffalo, NY	Triangle-pyramid shaped speakers Hello, I'm a true newbie to DIY speakers, and I did a search for the term "Pyramid." If you can direct me to where this has been discussed before, I'd much appreciate it. I inherited a pair of triangle pyramid cabinets that were designed for a 10" woofer and a 3 1/2" driver for high frequencies. In the course of history, they were modified to hold two 5 1/2" drivers. The drivers were destroyed by a little brother's ignorant thumb (Augh!). There were no other electronics inside. I'll give you the measurements, then describe what I'd like to do. It's built with 3/4" presswood of some sort. inside height from middle bottom to top peak is 14" the length of each joint is 16" According to V=1/3Bh, that comes to roughly 520 cu. in. right? 520 cu. in. comes to .3 cu. ft. or 8.5 liters I went to Parts Express to search for parts (go figure) which might make these speakers into a nice 2-way system for about $200 or so. I'd like to replace the front-panel with a substantial Vifa driver (P21WO-20) that has decent frequency response so that with a decent tweeter (D27TG-05) the system might cover the whole range without a big dip somewhere in the midrange. Firstly, is that a decent proposal? That's an 8" woofer in an enclosed configuration. I could go to 6 1/2", but I want that bottom end if at all possible. Secondly, I haven't got a clue as to crossover configuration. I can solder and I understand impedance and capacitance, etc., but can I just buy one designed to crossover at 2500 or 3000 Hz? That would make my life much easier. BTW, I'd like to see a discussion of the benefits of an equilateral pyramid as far as the whole "parallel surfaces" thing is concerned. No ports or anything, either. Hmm... Thanks!

23rd December 2002, 12:30 AM	#5
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Actually that looks like a tetrahedron... beauty. You might actually get more bass from a 6" driver in such a small box. Personally i like an even smaller midbass (and add a sub later). A Vifa P13 perhaps. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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22nd December 2002, 09:46 PM	#2
jleaman Banned Join Date: Apr 2002	Can you post a pic of some how. ?

22nd December 2002, 10:03 PM	#4
kneadle diyAudio Member Join Date: Dec 2002 Location: Buffalo, NY	You can kinda make out where the 3 1/2" driver went. The 10" filled up most of the remaining panel.

23rd December 2002, 12:50 AM	#6
kneadle diyAudio Member Join Date: Dec 2002 Location: Buffalo, NY	yes, tetrahedon. That's the shape. I said "triangle" to get that across. I'll do a search for tetrahedon now! I'd like some more input, though. I'm sure I can learn a lot about why the 6" has better low-end response in this thing.

23rd December 2002, 01:17 AM	#7
SkinnyBoy Banned Join Date: Nov 2002 Location: Adelaide, Australia	Are there any benifits in using that shape enclosure for ported speaker boxes? I ask cos I am doing woodwork next year and would like to make some speakers... ported, using 6inch Response speakers (from jaycar) and am not sure if the teacher will allow me to make just simple rectangular prism boxes.. ALSO!!!!! while I am here... how do the ReSponse 6inches compair to the Vifa P17WJs (sorry, couldn't find a link to info on them.. )

23rd December 2002, 02:18 AM	#10
kneadle diyAudio Member Join Date: Dec 2002 Location: Buffalo, NY	Hmm. I tried all the calculating I could understand with pebox, and it seemed like the 8" I picked out could fit in a .3 cu. ft. box. Maybe Im ignorant, though. That's why I'm here. Oops! Upon double checking, I see that I was wrong! The 6 1/2" P17WO-20 (for skinnyboy: http://www.partsexpress.com/pe/showd..._ID=7856&DID=7 ) is actually made for a .28 cu. ft. sealed configuration, the size of my box within 2/100ths. But that's my next question: Is a tetrahedron actually behaving like a .30 box or like a 1.0 cu. ft. box? Do you get my drift??

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