This is a quick mess-about, not for any kind of scientific testing purpose.
Anyway, I had some cardboard lying around, and 4 Visaton FRS8 speakers, so I decided to make a pair of near-field U-frame OB speakers. The amp you can see powering them was gutted from a pair of PC speakers, so it fits the bill nicely.
The sound
I'm not going to beat about the bush - it's not brilliant. The treble isn't quite right due to things like comb filtering, the bass is almost non-existant. Even so, it's not bad for what it is. I put them together with no calculations. The height for the sides was the height of the shoe-box I used, I only doubled the baffle thickness because I didn't want them to fold in half. But hey, it was fun - they don't go that loud, but they sound Ok for what they are, which is a half-hour build with the stuff in front of me.
If you've done anything like this, feel free to post it.
Chris
PS - I held it together with cello-tape
Anyway, I had some cardboard lying around, and 4 Visaton FRS8 speakers, so I decided to make a pair of near-field U-frame OB speakers. The amp you can see powering them was gutted from a pair of PC speakers, so it fits the bill nicely.
The sound
I'm not going to beat about the bush - it's not brilliant. The treble isn't quite right due to things like comb filtering, the bass is almost non-existant. Even so, it's not bad for what it is. I put them together with no calculations. The height for the sides was the height of the shoe-box I used, I only doubled the baffle thickness because I didn't want them to fold in half. But hey, it was fun - they don't go that loud, but they sound Ok for what they are, which is a half-hour build with the stuff in front of me.
If you've done anything like this, feel free to post it.
Chris
PS - I held it together with cello-tape
Attachments
I once built some test OB's with a pair of ikea boxes. I bet a fair number of us have done such things. Your pair appears to be much more thoroughly executed than mine was. Screws and everything!
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
About a year ago I built some car "back shelf" speakers out of some 3'' crappy 2W radio speakers, in cardboard enclosures with ports and bracing 
.
The "subwoofer" was a 5'' by 3'' whizzer cone speaker with a metal ring glued on the whizzer cone. This was placed face down on the back shelf, which resonated nicely.
I made the 3'' driver more compliant by wetting the paper surround and making it thinner and more flexible.
The system actually sounded half-decent with bass down to 70Hz, albiet with a 2W old tape/radio modded to take input from a 3.5mm jack...
Pity I can't put up any photos (car is gone, with the speakers). I wonder what the wrecker/scrap metal, etc. person thought when they saw them...
And yes, they were held together with cellotape.
@chris661: Yours look better than mine did .
. The "subwoofer" was a 5'' by 3'' whizzer cone speaker with a metal ring glued on the whizzer cone. This was placed face down on the back shelf, which resonated nicely.
I made the 3'' driver more compliant by wetting the paper surround and making it thinner and more flexible.
The system actually sounded half-decent with bass down to 70Hz, albiet with a 2W old tape/radio modded to take input from a 3.5mm jack...
Pity I can't put up any photos (car is gone, with the speakers). I wonder what the wrecker/scrap metal, etc. person thought when they saw them...
And yes, they were held together with cellotape.
@chris661: Yours look better than mine did
.
chris661...
you may not have noticed, but lots have cut their teeth on OB speakers. They can be quite a revelation. One thing I might suggest that you do is to actually make them a "U" from top to bottom, and make them deep enough to help with bass reinforcement.
If the drivers are suitable, a lot have fun can be had with OBs and are still my favourite type. Boxes always sound like boxes. OBs sound like nothing.
An interesting comparison was done between the Wharfedale SB3 loudspeakers and the Quad ESLs. The point made was that both had advantages, but the sound was closer than one might think. This was a contemporary comparison, not something done from memory but a true side by side.
you may not have noticed, but lots have cut their teeth on OB speakers. They can be quite a revelation. One thing I might suggest that you do is to actually make them a "U" from top to bottom, and make them deep enough to help with bass reinforcement.
If the drivers are suitable, a lot have fun can be had with OBs and are still my favourite type. Boxes always sound like boxes. OBs sound like nothing.
An interesting comparison was done between the Wharfedale SB3 loudspeakers and the Quad ESLs. The point made was that both had advantages, but the sound was closer than one might think. This was a contemporary comparison, not something done from memory but a true side by side.
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Yes, the drivers themselves are suitable - Qts of around 1, but the fs is too high for any meaningful bass (120Hz).
I did make, using the same drivers, a design that cancelled the rearwave of the OB speaker - this gave a 6dB/octave rolloff, without the need for a huge baffle. Meaningful bass down to 60Hz, not bad for a 3" driver.
I should probably re-do those, but with some kind of calculation for the sealed box behind the OB driver (LP around 300Hz), so the excursions come close to matching. The midrange was very nice, but the design itself wasn't suited to rock etc, where you need lots of noise. Did extremely well with girl+guitar things, light music (Paul Weller).
I know OBs sound good, but my room simply isn't suited to them - I have little space for anything large, and there's furnature everywhere (my bedroom), so my little OB+rearwave cancellers are all I can use from that category.
Chris
I did make, using the same drivers, a design that cancelled the rearwave of the OB speaker - this gave a 6dB/octave rolloff, without the need for a huge baffle. Meaningful bass down to 60Hz, not bad for a 3" driver.
I should probably re-do those, but with some kind of calculation for the sealed box behind the OB driver (LP around 300Hz), so the excursions come close to matching. The midrange was very nice, but the design itself wasn't suited to rock etc, where you need lots of noise. Did extremely well with girl+guitar things, light music (Paul Weller).
I know OBs sound good, but my room simply isn't suited to them - I have little space for anything large, and there's furnature everywhere (my bedroom), so my little OB+rearwave cancellers are all I can use from that category.
Chris
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