Large baffles (and indeed large woofers) tend to provide a "big" sound. So in that sense you aren't wrong.
The problem is the use of the plate amp to achieve that.. it's just not a good idea.
Im sorry if I didnt explain enough here. in my preamp, I have my two outputs. one to the FR, one to the subs. I would add the crossover for the FR AND for the woofer in the pre amp. I would also mod my plate amp to also be able to set the low pass at 300hz. so with that, I think I would be fine?Large baffles (and indeed large woofers) tend to provide a "big" sound. So in that sense you aren't wrong.
The problem is the use of the plate amp to achieve that.. it's just not a good idea.
..add it "in the pre-amp"?
What I'm suggesting a full passive crossover for your Fullrange to Midbass driver. That would be Source>Preamp>Amp>Passive Crossover (as a part of your loudspeaker). No plate-amp at all there (..unless you also are using subwoofer(s)).
With the right sized baffle (and driver placement on baffle), bass driver enhanced efficiency (when compared to your fullrange driver), low freq. response, and crossover transition - it might be as simple as a parallel RC circuit to flatten the rise in impedance + a large inductor in series with an electrical first order around 60-90 Hz. That would be just your low pass filter for that part of your passive crossover.
Tony Gee's Mezo Galactic uses this technique:
http://www.humblehomemadehifi.com/download/Humble Homemade Hifi_Mezzo Galactica_copy.pdf
Description starts at the end of the 3rd page "The Crossover Network" heading. He also adds-in a paralleled LCR for the impedance rise from the driver's in-box resonance.
On the top of the 5th page you'll see the circuit - L1 sets the 1st order electrical behaviour for the low-pass (and also acts as an eq. to "flatten" the response). C1 and R1 form the RC to flatten the impedance rise at higher freq.s (and as a result allows L1 to function properly). LZ1, CZ1, and RZ1 form the optional LCR which lowers the driver's in-box resonance.
It's a good article to read, and re-read.
The thing is though.. passive crossover parts aren't cheap!
You might be better off with a more expensive driver that provides a better compromise.
Such other option would be:
AE Speakers Online Store
Where only an inductor is used for the low-pass portion (..and no RC, because this driver doesn't have much of a rise in impedance in your desired upper freq. bandwidth), AND
-the SECOND voice coil on the driver is "driven" by your plate amps.
The bummer is that there really isn't a comparable large driver (DVC) at a lower cost.. I wouldn't suggest any of the "thumpy" high-mass Auto-sound drivers, or even the cheap subs from Dayton Audio/Parts express..
Note the Inductor for the low-pass would be smaller (because the electrical and acoustic target would be similar not having to perform much of an eq. function).
The variable low-pass from the plate-amp and variable gain would allow you to "eq." the response for baffle step pressure loss.
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I'm gettin help from Thorsten Loesch. Here's what he told me to do...
"
The principle would be you get a box for the Alpairs to maximise how low they go. You then use an active filter at 300Hz to roll them off, so they play louder, cleaner etc. This should allow at least 75Hz or so cutoff. So you will two octaves below crossover for the fullrange to "overlap".
You then add the 15" Woofer with another 1st order crossover at 300Hz. This makes absolutely sure you perfect integration if your levels are right. Looking at the graphs the woofer is acceptably smooth to well past 1KHz, so again, you have 2 octaves overlap.
You use the standard plate amp's, but you add to them by adding EQ for the Boxes (use a so-called EBS6 alignment, this can easily go well below the drivers Fs) and modifying the capacitor values in the filter to be much smaller, so your "hard cutoff" moves to 1.2KHz..."
"
The principle would be you get a box for the Alpairs to maximise how low they go. You then use an active filter at 300Hz to roll them off, so they play louder, cleaner etc. This should allow at least 75Hz or so cutoff. So you will two octaves below crossover for the fullrange to "overlap".
You then add the 15" Woofer with another 1st order crossover at 300Hz. This makes absolutely sure you perfect integration if your levels are right. Looking at the graphs the woofer is acceptably smooth to well past 1KHz, so again, you have 2 octaves overlap.
You use the standard plate amp's, but you add to them by adding EQ for the Boxes (use a so-called EBS6 alignment, this can easily go well below the drivers Fs) and modifying the capacitor values in the filter to be much smaller, so your "hard cutoff" moves to 1.2KHz..."
The midbass in the Gedlee Summa is the B&C 15TBX100. It's a subwoofer, but due to being waaaay overengineered by B&C, it's good to 1khz. (Geddes crosses it at 900hz.) It sells for about $300 at Parts Express IIRC.
Before I bought my Summas, I tried to build a 'clone' of them myself. I used the P-Audio SN12MB. It sells for half of what an equivalent B&C driver costs. The main reason that the price is lower is that it doesn't have the power handling of the B&C, and it doesn't have shorting rings. Both of these features of the B&C increase the cost and complexity of the motor a great deal.
I know Geddes thinks the quality of P-Audio drivers is crap, but I've never had a problem with them. Have been running P-Audio for longer than B&C.
I believe the 15" version of the driver I selected has been discontinued, but they're easy to find on eBay, and I think Loudspeakers Plus still has some left. It's called the "SN15MB" and it sells for about $150 IIRC.
If you do opt for P-Audio, be sure to avoid the high power drivers they sell. Their inductance is too high to be used for a midrange. The whole reason that I selected the SN12MB wasn't that it was cheap, I selected it because it has low inductance and it's T/S parameters are appropriate for a midrange in a high efficiency cabinet.
Having said all that, I'll admit that I threw in the towel on that project, and simply BOUGHT the Gedlee Summas instead.
I just checked inventory at Loudspeakersplus, and they're sold out. But there are three for sale on eBay at a price of $140 each.
P Audio SN-15MB 15 Inch WOofer with NEO Magnet - GREAT PRICE! | eBay
here's the spec sheet, note that it's +/- 3dB from 300hz to 3000hz:
http://www.cannononline.info/pdf/SN-15MB.pdf
P Audio SN-15MB 15 Inch WOofer with NEO Magnet - GREAT PRICE! | eBay
here's the spec sheet, note that it's +/- 3dB from 300hz to 3000hz:
http://www.cannononline.info/pdf/SN-15MB.pdf
I hear your favored speaker is lite, and fairly cheap for neo.
But why you recommend Fs=47, if the Op wanted 30-300?
And I remind you, he's "not fussy about 25Hz"...
When put in a conventional box, I would expect Fs goes up.
Make life difficult operating below Fs, though it can be done.
I recommended Dayton PA380 cause its $58, 98.5dB, 28.3Hz.
With 23.5 Tesla Meters of heave, can really hurt something.
The back of whoever lifts it probably. Hey, but its 58 bucks!
!ts not light, got no shorting rings (but Qes is still very low)
Only 10 ohms at 300Hz, does this project really need rings?
But why you recommend Fs=47, if the Op wanted 30-300?
And I remind you, he's "not fussy about 25Hz"...
When put in a conventional box, I would expect Fs goes up.
Make life difficult operating below Fs, though it can be done.
I recommended Dayton PA380 cause its $58, 98.5dB, 28.3Hz.
With 23.5 Tesla Meters of heave, can really hurt something.
The back of whoever lifts it probably. Hey, but its 58 bucks!
!ts not light, got no shorting rings (but Qes is still very low)
Only 10 ohms at 300Hz, does this project really need rings?
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Altec Lansing GPA 414 414-8B 414-8C NEW | eBay
..or the alnico version for almost 100 more.
https://sites.google.com/site/drivervault/driver-measurements/tang-band-75-1558se/gpa-altec-414
It has unique characteristics of low mms (for it's Sd), low fs, and good eff..
Note: the 8 ohm version should have about 3db higher output than shown on the driver vault.
Move down a size to the 10" and your back to the Audax I mentioned..
dont worry about it, I understood you have 90db mid/fullrange
one of the SB Acoutic's 12" looks smooth enough for this
If it's kept under 200 Hz, yes. HOWEVER, to get that "large" sound often requires a lot more output into the upper mids..
http://www.zaphaudio.com/SB12.3/SB34NRX75-6-measured-FR-nearfield-2.07cuft.gif
worse - look at it's T/S param.s:
http://www.tymphany.com/files/XXLS-P830845 Rev1_0.pdf
The SLS isn't great either, but better:
http://www.tymphany.com/files/SLS-P830669 Rev1_0.pdf
Now here is one that's new to me, and it should work (mms 57grams, 23 Hz fs, 92 db):
http://www.parts-express.com/pe/showdetl.cfm?partnumber=292-580
http://www.visaton.com/en/chassis_zubehoer/tiefton/w300s_8.html
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