Reading about @perrymarshall ’s Bitches Brew and other OB creations is an inspirational experience.
I already own some drivers etc that would could be used for a Bitches Brew inspired speaker. I have 4 x 18” woofers that have a sensitivity of 95db, so I’m thinking 2 per side. I also own a pair of ES 1200 biradial horns, so rather than use a coax for the mid + tweeter, I’m thinking this horn fitted with a 1” throat CD plus a suitable mid range driver. So I’m looking for suggestions for the mid range. It needs to be at least 98db sensitivity, be usable over say 150hz to 1500hz and to avoid beaming problems probably needs to be no bigger than 10”. All suggestions gratefully received.
I already own some drivers etc that would could be used for a Bitches Brew inspired speaker. I have 4 x 18” woofers that have a sensitivity of 95db, so I’m thinking 2 per side. I also own a pair of ES 1200 biradial horns, so rather than use a coax for the mid + tweeter, I’m thinking this horn fitted with a 1” throat CD plus a suitable mid range driver. So I’m looking for suggestions for the mid range. It needs to be at least 98db sensitivity, be usable over say 150hz to 1500hz and to avoid beaming problems probably needs to be no bigger than 10”. All suggestions gratefully received.
I've used Faital drivers and been happy with them (though I've not used these specific units). A couple of 10" candidates:
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101040120
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101040130
There are many other brands and drivers that will work. The main priority is the Bitches Brew design uses wide bandwidth drivers that can handle wide overlap. For example this is the current configuration I'm using - acoustic outputs from the individual drivers as well as their sum:
The objective is that after DSP crossover, the acoustic slopes are a low-Q 12dB/octave gentle slope with no surprises. I've talked about this a lot in other threads. So you want a 10" that can go up to 4-5K even if the official xover frequency is quite a bit lower.
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101040120
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101040130
There are many other brands and drivers that will work. The main priority is the Bitches Brew design uses wide bandwidth drivers that can handle wide overlap. For example this is the current configuration I'm using - acoustic outputs from the individual drivers as well as their sum:
The objective is that after DSP crossover, the acoustic slopes are a low-Q 12dB/octave gentle slope with no surprises. I've talked about this a lot in other threads. So you want a 10" that can go up to 4-5K even if the official xover frequency is quite a bit lower.
Maybe this one are appropriate drivers:
https://www.precision-devices.com/products/all-products/pd-103nr1/
and
https://www.eighteensound.it/en/products/lf-driver/10-0/8/10M600
Thank you for reminding me about PD. I meant to check their range as I live 12 miles from where they are based ! That driver does look good.
The 18sound FR looks to roll off at the bottom end a bit too soon to my eye, but maybe that just facilitates a nice low order crossover ?
The 18sound FR looks to roll off at the bottom end a bit too soon to my eye, but maybe that just facilitates a nice low order crossover ?
Its considered 95dB on open baffle. If its too low, good luck finding higher. I would be more worried about low power handling. Its been specifically designed for open baffle. Covers very wide range, sounds great and its cheap.
https://www.caintuckaudio.com/Betsy_Baffle_Questions.html
The combined sensitivity of a pair of the BMS woofers I have will be 98db. The CD will be even higher. It’s my belief that there is a correlation between sensitivity and how dynamic a speaker sounds. (I suspect Perry would also subscribe to that view.). So i don’t want to limit system sensitivity by using a mid with lower than 98db. Fortunately options clearly do exist. I would have been interested in the Betsy had it been just a few db more sensitive.
8" will crossover 1100 to 1300
So nothing larger than that. 92 to 93 dB is realistic, there could be others higher.
Im sure distortion and heavy rising response would be the tradeoff to go higher.
Likely a good match you'll experience 5 to 6 dB of bass losses or more in needed areas.
And a horrible peak regardless, its Dipole.
The crossover after correction will knock 95 dB way down
So nothing larger than that. 92 to 93 dB is realistic, there could be others higher.
Im sure distortion and heavy rising response would be the tradeoff to go higher.
Likely a good match you'll experience 5 to 6 dB of bass losses or more in needed areas.
And a horrible peak regardless, its Dipole.
The crossover after correction will knock 95 dB way down
I fully agree that higher sensitivity speakers sound more dynamic. Nothing new.
I am curious what you come up with.
Used to have mtm with FaitalPro 6fe200 open baffle, wait, i still have it in the storage.
If one mid is not enough, use two in mtm.
I am curious what you come up with.
Used to have mtm with FaitalPro 6fe200 open baffle, wait, i still have it in the storage.
If one mid is not enough, use two in mtm.
I see why you want an efficient midrange, but I'm puzzled by you saying that it has to be 98 dB. I assume, since you're taking inspiration from the Bitches' Brew, that your plan is to use the 18" woofers on an open baffle? (With wings?) If so the sensitivity you'll get in the bass range is going to be determined less by the nominal driver sensitivity, than by the effective baffle size and the rest of the driver parameters. To give an example, modelling a pair of 18N862 on a large effective baffle (1.5m square) you can get 98dB/2.83V at about 70 Hz and above. But if you want more extension (say -6dB in the low 30s) I don't think you're going to get more than 92-93 dB out of them. And if you're crossing at 150Hz you'll need to be careful about how deep your wings are. So my guess would be that a midrange with sensitivity around 92-93 would be sufficient.
@ianbo; yes I plan OB with wings, and you guessed right as regards the woofer model. I do want to get down to the low 30s so I take your point about baffle size. 150hz is just an estimate at this point; I’d go to say 100hz if the mid could be crossed there without compromise.
If you are right about the effective sensitivity of the woofers then that does open up the choice for the mids, albeit to my slight disappointment.
If you are right about the effective sensitivity of the woofers then that does open up the choice for the mids, albeit to my slight disappointment.
The woofers might produce only 90dB at 40Hz but if they're putting out 98dB above 70Hz, and if you're using the passive series crossover, then it's best if the mid SPL to be in the high 90s. If you're doing 3 way full active then the SPL of the mids is less of a priority.
At this point I’m not sure whether I’ll go semi-active (2 channels per side) or fully active (3 channels).
Yes, I can see that the passive crossover can help with a bit of filter gain. I guess the size of the baffle and wings is key to getting the sensitivity up there. And your DSP eq helps the extension a lot.
I noticed the post you just made with the current eq curve (https://www.diyaudio.com/community/...rshalls-live-edge-dipoles.424917/post-7959206) Do I understand it right, that you don't need any equalisation specifically for cavity resonance created by the wings? If so, I guess the slanting of the wings is important?
No EQ necessary for cavity effects with wings because that resonance is 150Hz which is above the crossover frequency. Plus the cavity residence is different for each of the two 15OB350s.
The sinewave shape of the wings is important, but they don’t have to be slanted wider apart, so as to be non-parallel. Though I suppose that might help a little.
The sinewave shape of the wings is important, but they don’t have to be slanted wider apart, so as to be non-parallel. Though I suppose that might help a little.
There is no free lunch with woofers on open baffle. Be carefull how much you boost low end (20Hz) since you may be bottoming woofers at one point or overdriving eq for woofers, assuming you have plenty watts available (hundreds)...
OP is very optimistic about bass efficiency, been there, been doing open baffle for 40 years. The drop is dramatic. You want 20Hz from open baffle, its doable, but not at 98dB efficiency.
Curious what mid he sellects.
Thete is no belief, only experience. Your bass cancellation will be significant. So you are doing bass open baffle, mid open baffle, but tweeter will be cd, that means basically dome horn loaded, not open baffle. How you address lack of back radiation?