It's a few years since my last speaker build, and are thinking of something like:
Two 12" or 15" woofers crossed over to either 4 fostex 3"- 5" FR drivers or a large ribbon transducer. I would prefer to cross over around 400-500Hz, and in that case I think the Fostex' are the best bet since few ribbons go that far down?
But will the Fostexs be as detailed as a ribbon? Would it be better to cross over around 2kHz and use a ribbon?
Which Fostex 3"-5" would any-yous recommend?
Two 12" or 15" woofers crossed over to either 4 fostex 3"- 5" FR drivers or a large ribbon transducer. I would prefer to cross over around 400-500Hz, and in that case I think the Fostex' are the best bet since few ribbons go that far down?
But will the Fostexs be as detailed as a ribbon? Would it be better to cross over around 2kHz and use a ribbon?
Which Fostex 3"-5" would any-yous recommend?
SemperFi said:
More to the point, the outputs from the multiple FR drivers will comb with each other, causing lobing and progressively severe HF attenuation from ~4.5KHz upward (with the 3in drivers -about 2.75KHz for 5in), so you'll need to EQ them flat or add a tweeter. Close in you might get away with it with Jordan units, but those a) cost a packet, and b) I'm still unconvinced. Ted Jordan is one of the greatest driver designers in the world, but even he can't beat the laws of physics.
Line arrays using large numbers of FR drivers don't work, bluntly. They need huge Eq to lift the HF, and that does nothing about the lobing issues. As an illustration of what I mean, have a look at the plots presented here: http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html And that's using 2in drivers. When centre to centre spacing between drivers is greater than 1 wavelength of the highest frequency to be reproduced, you get this lobing effect. Fact of life, & there's nothing that can be done about it.
Most arrays are 2 way setups. With small dome tweeters, you can just about get away with it, but ribbons are usually favoured because they'll behave as a column. Problem with those is that it almost invariably involves needing to place an XO slap-bang in the middle of the telephone band, where our hearing is most sensitive. So the XO needs to be good. Very good.
The other alternative is a focused array, where the front is curved into a concave shape. That helps to an extent, though it's of more use in combatting the delay issues involved with column speakers where the output from the ends has to travel a greater distance to reach the listener than that in the middle.
Having said all that, Roger Russel uses 25 3in FR units in his array, then EQs out the HF loss (& the LF come to that, as they're sealed boxes, using high Fs drivers, so not much natural LF action without electronic correction), and some people think it's the best thing since the pre-sliced bread days. Ted Jordan advocates using 4 of his smaller drivers in a tiny array (the beaming probably helps). And Fostex suggest using two of their FF85Ks in one BLH (ditto, and they have a rising response, which probably helps compensate). So, as ever, YMMV. All I can say is that it wouldn't be my first port of call.
Most arrays are 2 way setups. With small dome tweeters, you can just about get away with it, but ribbons are usually favoured because they'll behave as a column. Problem with those is that it almost invariably involves needing to place an XO slap-bang in the middle of the telephone band, where our hearing is most sensitive. So the XO needs to be good. Very good.
The other alternative is a focused array, where the front is curved into a concave shape. That helps to an extent, though it's of more use in combatting the delay issues involved with column speakers where the output from the ends has to travel a greater distance to reach the listener than that in the middle.
Having said all that, Roger Russel uses 25 3in FR units in his array, then EQs out the HF loss (& the LF come to that, as they're sealed boxes, using high Fs drivers, so not much natural LF action without electronic correction), and some people think it's the best thing since the pre-sliced bread days. Ted Jordan advocates using 4 of his smaller drivers in a tiny array (the beaming probably helps). And Fostex suggest using two of their FF85Ks in one BLH (ditto, and they have a rising response, which probably helps compensate). So, as ever, YMMV. All I can say is that it wouldn't be my first port of call.
Maybe not in your price range, but here is a large ribbon:
http://www.sonus.de/php/p_produkte....engruppe2_id=1&warengruppe3_id=1&produkt_id=1
http://www.sonus.de/php/p_produkte....engruppe2_id=1&warengruppe3_id=1&produkt_id=1
These look nice for OTL.
http://cgi.ebay.com/Vintage-Pioneer...ryZ50597QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://cgi.ebay.com/Vintage-Pioneer...ryZ50597QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Thanks for good info.
Since the lobing effect occurs at high frequencies, is it safe to use several bass drivers and cross over somewhere in the low-mids? Say 4x12" bass drivers crossed over to a single Fostex FR around 400Hz.
That should present a relatively high impedance load for my OTLs at the low end, which is where most power is sucked out.
So then remains the question of which FR driver to select?
Hmmm, sitting here thinking of the expence of 4 bass drivers per side, and the size of the speaker that'll fit all those drivers, I realize a horn loaded FR may be best after all...
Since the lobing effect occurs at high frequencies, is it safe to use several bass drivers and cross over somewhere in the low-mids? Say 4x12" bass drivers crossed over to a single Fostex FR around 400Hz.
That should present a relatively high impedance load for my OTLs at the low end, which is where most power is sucked out.
So then remains the question of which FR driver to select?
Hmmm, sitting here thinking of the expence of 4 bass drivers per side, and the size of the speaker that'll fit all those drivers, I realize a horn loaded FR may be best after all...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.