The principle of operation is that, for small cone separations (relative to wavelength), the air between the cones moves as though it were contained - and therefore the configuration is approximately equal to a single driver furnished with a U-shaped baffle. Which reduces the cancellation effect inherent with OB speakers.
Regarding back-to-back operation, I suspect it may be very slightly inferior - but surely this would be very straightforward to evaluate by experiment? And likewise the respective spacings...
I never tried back to back arrangement. I used one woofer behind the other for a short period of time before I went face to face.
The advantage, though, of the clam shell arrangement is the cancellation between the drivers which limits output from the sides in favour of front to back. This may explain why this arrangement is so room friendly, certainly in my room inciting very few modes compared to other designs. This was especially true of the U-frames I was using which cancelled all bass from my listening position
I would imagine that a pair of woofers positioned one behind the other might incite room modes as they would radiate sideways. Back to back might cancel if one is wired out of phase. Dont know.....just speculating.
Hi XRK....hope all good with you!
I was crossing around 275hz at the time of the PRV's but a lot has passed since then. At the moment I am using boxed speakers on top assisted by the UM's crossing at 70Hz.
I asked PSSound (who has a vid of his own superb OBs on YouTube) if he could recommend a car audio woofer for the clamshell approach. He pointed me to these: https://stereointegrity.com/product/ht-18-v3/
They look like they have the right specs to me, but would be interested in what the more knowledgeable members think - ?
They look like they have the right specs to me, but would be interested in what the more knowledgeable members think - ?
Yes....I think these V3 are fairly new, and almost half price vs UM18's.....could be a cheaper alternative.
My only concern is the venting holes which look fairly restrictive and could chuff which would be annoying in naked configuration.
I smell some problems with those twin tweeters and dipole mid in a wide baffle with angled wings... But the SLOB bass system is nice!
Very little info on the website. 6moons says more to come... https://www.lindstromaudio.com/products
Very typical 6moos stuff, extravaganza of loudspeaker design, beyond basic acoustics and common sense designs (IMO sorry)
in this Edge sim tweeters are on a plane board. But in Iso85 they are almost at 90deg angle to each other, so on-axis spl is very low compared to off-axis. It would be very interesting to see good measurements of this thing! Midrange looses dipole pattern around 600Hz, starts beaming around 2khz. No idea where xo is...
Very little info on the website. 6moons says more to come... https://www.lindstromaudio.com/products
Very typical 6moos stuff, extravaganza of loudspeaker design, beyond basic acoustics and common sense designs (IMO sorry)
in this Edge sim tweeters are on a plane board. But in Iso85 they are almost at 90deg angle to each other, so on-axis spl is very low compared to off-axis. It would be very interesting to see good measurements of this thing! Midrange looses dipole pattern around 600Hz, starts beaming around 2khz. No idea where xo is...
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I'm wanting to build something very similar to the circles, except the drivers suspended between 2 slim vertical poles.
a naked grs 3", naked grs 8"/10", under 10" naked midbass (not sure which yet), clamshell 12"/15", linkwitz Thor.
I would prefer to use the 10" grs, but money is any issue, and I already have the 8". I could go to 12" for the midbass if necessary for cost.
The Thor will come in at 50hz. Can I get away with a 12" clamshell? And if so what are the cheap options. Ideas for cheapish midbass too?
I've never built a speaker before. Will use active xover, Except the analogue one I already have with the Thor that I also already have. I actually have 2 Thors. I'm very Thor'd.
a naked grs 3", naked grs 8"/10", under 10" naked midbass (not sure which yet), clamshell 12"/15", linkwitz Thor.
I would prefer to use the 10" grs, but money is any issue, and I already have the 8". I could go to 12" for the midbass if necessary for cost.
The Thor will come in at 50hz. Can I get away with a 12" clamshell? And if so what are the cheap options. Ideas for cheapish midbass too?
I've never built a speaker before. Will use active xover, Except the analogue one I already have with the Thor that I also already have. I actually have 2 Thors. I'm very Thor'd.
Yes pricey, but if you were lucky enough to find some used ones at the right price . . .Send me 4 of them and I can test them for you
First impression is good: lots of xmax, FS of 25Hz, and a very open construction, always a good indicator there will not be trapped air. But pricy (I haven't looked at others, maybe their price increased as well...)
What you want to shoot for is to XO each driver before they start to beam. Doing this keeps the off axis response close to the on axis just down in level. Ideally the off axis response curve should be identical to the on axis (but lower in level), this becomes more difficult at high frequencies. If you get this right then the speaker power response becomes flat and the speaker will image better.
So having been inspired by the OP’s and Vic’s clamshell adventures I‘ve decided I’ve got to try this and all being well I’ll be acquiring 4 x 18” woofers. I anticipate using them up to c. 100Hz and I’m now starting to think about the 100 - 600Hz band that I need to cover. I want to agaIn go baffle-less / suspended. I already own some AE Dipole 12 drivers so I will be using those. I could just use 1 x 12” per side, but I‘d prefer to find a way to use 2 per side but without just mounting them one above the other as that would increase the height too much for the bi-radial horn that will sit on top. (Yes its going to be a hybrid OB / horn speaker.) Another clamshell would be one option, or I wondered about doing the opposite and have 2 drivers back to back, one facing forwards the other facing backwards? I’d welcome observations and suggestions (and yes I’m dead set on trying the OB / horn thing so don’t try and talk me out of that!).
12" for 100Hz seems a bit shy, but since you have the drivers and you are already set on it...go for it.
But 2x12" might be great. I think I read somewhere, maybe at Linkwitz site, the distance between the drivers was important (along their axis). Back to back would be worst, largest distance. You can try it and listen.
I think back to front, like Legacy Whispers, would keep that distance short and provide you one clean driver face looking at you. This might be important in your upper range. Eventually you could low pass the back 12" such that both play from 100Hz up to x and only the front driver plays from x (cap, or 1st order xo).
FWIW, I believe OP Bushmeister runs Eminence Deltalite 2515 from 120Hz (or 150?) to 600Hz.
But 2x12" might be great. I think I read somewhere, maybe at Linkwitz site, the distance between the drivers was important (along their axis). Back to back would be worst, largest distance. You can try it and listen.
I think back to front, like Legacy Whispers, would keep that distance short and provide you one clean driver face looking at you. This might be important in your upper range. Eventually you could low pass the back 12" such that both play from 100Hz up to x and only the front driver plays from x (cap, or 1st order xo).
FWIW, I believe OP Bushmeister runs Eminence Deltalite 2515 from 120Hz (or 150?) to 600Hz.
100-600Hz is well within the operating envelope for the Dipole 12s, but I do like the idea of just using one for the lower end of the band. - it should reduce the amount of EQ needed. Having them both facing forwards is definitely attractive in terms of aesthetics as I think they look very cool. The beauty of the suspended driver approach is that it should be relatively easy to try the different possible configurations.