If you are planning an first OB on a budget, I suggest you have a look at this thread.
Fast, fun, Inexpensive OB project
Some of the recent posts will give you an idea of the sound. In the post post there are links to the current versions.
Fast, fun, Inexpensive OB project
Some of the recent posts will give you an idea of the sound. In the post post there are links to the current versions.
first ob speaker build
Thank you for responding. I studied that speaker thread yesterday. I'm looking for
something a little more than that one. My budget is more flexible than that i guess. My past designs and builds have been a few three ways, some bookshelves, but mostly MTM, some floor standing, some with separate subs.
I'm really interested in a OB MTM with a soft or silk dome tweeter or maybe a
planar. Any suggestions, advice, input or experiences are welcomed. Good or bad.
Thank you Sir,
patiently awaiting
benb
sv572
Thank you for responding. I studied that speaker thread yesterday. I'm looking for
something a little more than that one. My budget is more flexible than that i guess. My past designs and builds have been a few three ways, some bookshelves, but mostly MTM, some floor standing, some with separate subs.
I'm really interested in a OB MTM with a soft or silk dome tweeter or maybe a
planar. Any suggestions, advice, input or experiences are welcomed. Good or bad.
Thank you Sir,
patiently awaiting
benb
sv572
Here you go. Paul Carmody's Sunflower. MTM OB hybrid.
Paul Carmody's DIY Speaker Pages - Dipole and Open-Baffle
Paul Carmody's DIY Speaker Pages - Dipole and Open-Baffle
When I think OB I don't immediately think 10" woofer, but with two per side you'd have a little more displacement than a singe 12". Somewhere between a 12 and a 15. Not bad.
I don't know the dipole 10" the OP mentions, but maybe it's their IB woofer? It has a very high Qts, low Fs and good x-max. Very inefficient, but maybe that very high Q would help in the bottom end. At least a 10" won't be too hard to cross over to a silk dome tweeter. A Planar could be fun, especially if you can take the back off.
I don't know the dipole 10" the OP mentions, but maybe it's their IB woofer? It has a very high Qts, low Fs and good x-max. Very inefficient, but maybe that very high Q would help in the bottom end. At least a 10" won't be too hard to cross over to a silk dome tweeter. A Planar could be fun, especially if you can take the back off.
MTM with a 10" ?
Crossover for 10” mtm
If parts don't fit, i.e. a pro midwoofer won't take abuse like a long excursion woofer, some changes are on the way. Essentially, I would follow (like at the beginning in of Fast, fun OB thread) the dome tweeter idea...since it's the component less stressed. And then apply the EQ (bi-quad, +10 dB @ 34 Hz as example) and... voilà!
Crossover for 10” mtm
If parts don't fit, i.e. a pro midwoofer won't take abuse like a long excursion woofer, some changes are on the way. Essentially, I would follow (like at the beginning in of Fast, fun OB thread) the dome tweeter idea...since it's the component less stressed. And then apply the EQ (bi-quad, +10 dB @ 34 Hz as example) and... voilà!
Two dome tweeters (front-back) would make the completed speaker dipole.
I like Pano’s idea of using a planar mid-tweet. The slim 8 GRS planar seems to be well liked, inexpensive, and dipole.
GRS PT6816-8 8" Planar Slim Tweeter 8 Ohm
New planar drivers at Parts Express
I like Pano’s idea of using a planar mid-tweet. The slim 8 GRS planar seems to be well liked, inexpensive, and dipole.
GRS PT6816-8 8" Planar Slim Tweeter 8 Ohm
New planar drivers at Parts Express
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Good afternoon Gentlemen.Thank all of you for your response.
Between interweb connectivity issues and getting called into work on my much needed days
of, I apologize for not being prompt.
The IB 10" driver that y'all have mentioned is the driver I'm considering. It does have a low sensitivity. Maybe 85 db with two per baffle ? I like the planar idea. I looked at both
the GRS pt6816 and the pt6825. On paper all these drivers look Ok, crossing over in the
640 to 800hz area. Do any of you have any experience with these drivers, i.e. real data?
As far as the baffle design goes I'm thinking of something that looks like a figure eight
floor stander, not sure. I realize the baffle plays a large part of the overall sound and design.
Your thoughts, recommendations, and all input will be much appreciated.
sv572
Between interweb connectivity issues and getting called into work on my much needed days
of, I apologize for not being prompt.
The IB 10" driver that y'all have mentioned is the driver I'm considering. It does have a low sensitivity. Maybe 85 db with two per baffle ? I like the planar idea. I looked at both
the GRS pt6816 and the pt6825. On paper all these drivers look Ok, crossing over in the
640 to 800hz area. Do any of you have any experience with these drivers, i.e. real data?
As far as the baffle design goes I'm thinking of something that looks like a figure eight
floor stander, not sure. I realize the baffle plays a large part of the overall sound and design.
Your thoughts, recommendations, and all input will be much appreciated.
sv572
It would be a good idea to plan on using several of those 10" woofers. The sensitivity is VERY low and with an OB you will lose a lot of low end sensitivity on top of that. Have you estimated the dipole gain/loss curve for your proposed baffle size? You might be surprised how high the low frequency losses will be. Don't set yourself up for failure by not checking this first.
Since the Re of the woofer is relatively high, you could parallel up to three of them for increased (+9dB) sensitivity at the cost of a low impedance load. You could use four per side, connect them series+parallel, and retain the easy-to-drive 8R load while still increasing the sensitivity by 6dB. The woofer is relatively inexpensive, so four per side is still relatively affordable.
Also, even though Fs is low and Qts relatively high, the driver doesn't have all that much total displacement (Xmax*Sd) since it is only a 10" driver. OB has much higher requirements in this area. Using several drivers will increase the total displacement as well.
Since the Re of the woofer is relatively high, you could parallel up to three of them for increased (+9dB) sensitivity at the cost of a low impedance load. You could use four per side, connect them series+parallel, and retain the easy-to-drive 8R load while still increasing the sensitivity by 6dB. The woofer is relatively inexpensive, so four per side is still relatively affordable.
Also, even though Fs is low and Qts relatively high, the driver doesn't have all that much total displacement (Xmax*Sd) since it is only a 10" driver. OB has much higher requirements in this area. Using several drivers will increase the total displacement as well.
Also, I would not recommend using the PT6816 tweeter below 800-1kHz because the distortion performance there is poor and it will sound bad. There have been some distortion measurements posted in this forum, one is shown below:
Also, the top end of the response rolls off a bit early for a tweeter.
A simple design that tries to marry this woofer and a tweeter as an MTM will have some real flaws. Are you sure that is what you want to try?
Also, the top end of the response rolls off a bit early for a tweeter.
A simple design that tries to marry this woofer and a tweeter as an MTM will have some real flaws. Are you sure that is what you want to try?
I was thinking of a figure 8 in such that the baffle narrows around the tweeter for a more
open sound or less diffraction. And to CharlieLaub, what you have pointed out is exactly
why I think an MTM would be ideal. Thank you for the info on the planar, Moving the crossover up to 800 or so should not be a problem, should it? Although I am open to other
suggestions. I just like the sound and accuracy of a planar. Do yall have any suggestions on a start for a baffle design other than what I've mentioned? Also do any of you know of
any real time measurements or use of the IB 10 woofer?
I'm about to head to work, but I'll be monitoring any insight on my cell. Probably be home
around 6, Thank you all for your insight and direction, I'm looking forward to getting back
to this discussion.
benb
sv572
open sound or less diffraction. And to CharlieLaub, what you have pointed out is exactly
why I think an MTM would be ideal. Thank you for the info on the planar, Moving the crossover up to 800 or so should not be a problem, should it? Although I am open to other
suggestions. I just like the sound and accuracy of a planar. Do yall have any suggestions on a start for a baffle design other than what I've mentioned? Also do any of you know of
any real time measurements or use of the IB 10 woofer?
I'm about to head to work, but I'll be monitoring any insight on my cell. Probably be home
around 6, Thank you all for your insight and direction, I'm looking forward to getting back
to this discussion.
benb
sv572
The woofer that is located above the tweeter in the MTM will create problems and the "figure 8" baffle will make the physical build difficult. If you want to make a 2-way it would be better to use an MT with the tweeter on top of the baffle, e.g. not within the baffle. Then instead of multiples of that OB woofer I would use a pro audio driver, for instance there is a 10" Eminence driver, the Deltalite 2510, that would work well up to 800-1k Hz where you need to cross over to the planar and has Re~8R. Keep the baffle width less than about twice the radiator diameter, e.g. W<=2*SQRT(Sd/3.14), or about 18 inches or less. The advantage will be that the single 2510 has very high sensitivity, and this will offset the dipole losses and better match the tweeter sensitivity. A pair of MT, in a modest baffle (e.g. not wide) with the 2510 near the top edge and tweeter above it, would work down to 100Hz. Then use one or more closed box subwoofers to get your bass.
I think that would work out much better than an MTM setup where the woofer is trying to both get down to e.g. 20Hz and up to 1kHz. That is too wide of a band for a driver in a dipole type application. 2-3 octaves per driver is more realistic for any driver besides the tweeter, which can play from where it is crossed over all the way up to the top.
I think that would work out much better than an MTM setup where the woofer is trying to both get down to e.g. 20Hz and up to 1kHz. That is too wide of a band for a driver in a dipole type application. 2-3 octaves per driver is more realistic for any driver besides the tweeter, which can play from where it is crossed over all the way up to the top.
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