NCBlueTJ Posted March 6, 2012 Share Posted March 6, 2012 I have been brainstorming about how to bi-amp a set of La Scalas that I have been restoring and was wondering if anyone has ever come up with a crossover specifically for the mid to high section. What I had in mind was to use a 2-way active between the bass bin and top hat, and then to build a seperate crossover to cross between the K55 and the CT125s I'm using (say a 500uH coil and a 4uF cap). I know the traditional advice is to biamp and then use the high section of the stock crossover to cross between the mids and highs, but I was hoping to simplify this. In the interest of removing as many components from the signal path as possible, I'd like to see if I can cross between the mids and highs with simply a cap and coil (thus removing the autoformers, etc.). I can level match between the bass and mid/high using the active, but how different will the efficiency be between the mids and highs? I know the K55 is more efficient, but is it not also 16ohm while the tweeter is 8ohm? Shouldn't that give the tweet a 3dB boost and get the levels pretty close? I originally planned on using a miniDSP (and may still), but just recently got big into vinyl for the first time, so I'm trying to come up with an analogue solution. Any and all advice is much appreciated. Thanks, Lee Quote Link to comment Share on other sites More sharing options...
RRFL Posted March 6, 2012 Share Posted March 6, 2012 For consideration, tri-amp, then you can time align all 3 drivers and easily balance between drivers. If you Bi-amp you can remove the CT125s from the box placing them above the box and physically line up the Mid & High diaphragms to achieve time alignment. You need to roll off the K55 to match with the CT125's. You need to check but I think the BEC A/4500 might do the job for Bi-amping. Quote Link to comment Share on other sites More sharing options...
NCBlueTJ Posted March 6, 2012 Author Share Posted March 6, 2012 I have considered tri-amping, but that adds the cost of a pricier active crossover and another tube amplifier (would like to do tubes on top and SS for the bass), which kinda blows my budget. As far as I know, the only way to time align by tri-amping is digitally, which is what I'm looking to avoid. I am building my own top hat enclosure(s), and will have the ability to physically align mids and tweeters. Please correct me if I'm wrong, but the 500uH inductor should roll off the K55 around 4500ish, and the 4uF cap should bring the tweeters in around the same spot. I just don't know how closely the levels will match between them without an autoformer. If the tweeters do not output enough sound, I suppose I will be forced to triamp (or use the autoformers). Again, any experience or advice is appreciated. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted March 6, 2012 Share Posted March 6, 2012 I can level match between the bass and mid/high using the active, but how different will the efficiency be between the mids and highs? I know the K55 is more efficient, but is it not also 16ohm while the tweeter is 8ohm? Shouldn't that give the tweet a 3dB boost and get the levels pretty close? You can always use an L-pad (16 ohm, 50 watts) on the mid driver if it is too loud. Quote Link to comment Share on other sites More sharing options...
AndyGrandy Posted January 14, 2023 Share Posted January 14, 2023 I realize that this is an old thread but I'm looking to do the same thing and was wondering if NCBlueTJ had accomplished what he was aspiring to do here? Basically rebuilding the passive xover for the mid/high, while actively crossing between them and the bass bin. Anyone have a schematic for such a passive xover? Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted January 14, 2023 Share Posted January 14, 2023 37 minutes ago, AndyGrandy said: I realize that this is an old thread but I'm looking to do the same thing and was wondering if NCBlueTJ had accomplished what he was aspiring to do here? Basically rebuilding the passive xover for the mid/high, while actively crossing between them and the bass bin. Anyone have a schematic for such a passive xover? If you click on a username you can see the last time they were on the forum. In this case it’s been almost ten years. Quote Link to comment Share on other sites More sharing options...
The Dude Posted January 14, 2023 Share Posted January 14, 2023 @Don Richard whatever happened to him? @AndyGrandy sending pm Quote Link to comment Share on other sites More sharing options...
Rolox Posted January 17, 2023 Share Posted January 17, 2023 On 1/14/2023 at 5:24 PM, AndyGrandy said: I realize that this is an old thread but I'm looking to do the same thing and was wondering if NCBlueTJ had accomplished what he was aspiring to do here? Basically rebuilding the passive xover for the mid/high, while actively crossing between them and the bass bin. Anyone have a schematic for such a passive xover? I'm doing it, with a air of ALK original "Universal" networks. I just bypassed the coil in line with the woofer and connected the crossover inputs straight after it to the rest of the network that deals with the mids/high crossover. Works pretty well and the various taps on the auto former allow me to further dial in the midrange with the rest. Quote Link to comment Share on other sites More sharing options...
mboxler Posted January 17, 2023 Share Posted January 17, 2023 8 hours ago, Rolox said: I'm doing it, with a pair of ALK original "Universal" networks. I just bypassed the coil in line with the woofer and connected the crossover inputs straight after it to the rest of the network that deals with the mids/high crossover. Works pretty well and the various taps on the auto former allow me to further dial in the midrange with the rest. Just to clarify, if your active crossover contains a low pass to the woofer AND a high pass to the crossover, you should connect your high pass amplifier to the crossover RIGHT AFTER the crossover's 48uf(?) capacitor. Mike Quote Link to comment Share on other sites More sharing options...
Rolox Posted January 19, 2023 Share Posted January 19, 2023 On 1/17/2023 at 4:54 PM, mboxler said: Just to clarify, if your active crossover contains a low pass to the woofer AND a high pass to the crossover, you should connect your high pass amplifier to the crossover RIGHT AFTER the crossover's 48uf(?) capacitor. Mike Yes I wrote that wrong, I bypass the whole high-pass section of the midrange. I connect the midrange leaving only its low-pass components and the autoformer. 1 Quote Link to comment Share on other sites More sharing options...
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