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Bi amp pros out there I could use some help! First time Bi Amping...

Just picked up a BAT vk 200 for the bass and using my Pass Aleph 5 for the mids and tweets. Ive never played around with bi amping so I apologize in advance for any lame questions My speakers are Dunlavy SC3's original 5.5 nominal load. The pass is 90 wpc at 4 Ohm and the BAT is 200 wpc at 4 ohm so Im guessing around 75 wpc off the Pass Amp and 150 plus with the Bat Amp. My pre amp is a Aleph P and Im running the Single ended through a XLR adaptor (cause the Bat is Balanced inputs only) and the pass Aleph 5 off the XLR outputs of the pre and inputs of the Pass amp. The PASS Pre Amp manual says there is a 6db differential between the RCA and XLR outputs  two and both can be driven at the same time. So the RCA is 9db and the XLR is 15 db. Gain is within 2db on each amp. So whats the best way to do this? Get a custom XLR "Y" connector and drive both off the XLR output of the pre? Or is there a way better way to get the magic? This is past my "WORLD" Map and experience so Id thought Id ask for the smart people for advice. 

Thank you in advance!

-ALLGOOD
128x128haywood310
58 responses Add your response
bdp24's avatar
bdp24
9,788 posts
 
Even the good active x/o's (Bryston, Pass, First Watt, Marchand) provide only "textbook" filtering: 1st/2nd/3rd/4th-order (6/12/18/24dB per octave). None of them provide compensation networks, which lots of loudspeaker x/o's include, even some employing 1st-order filters (such as Thiel). Look at the x/o schematic for your speaker to see how complex it is.
mijostyn's avatar
mijostyn
8,570 posts
 
I have bypassed quite a few cross overs although I can't say how many.
A good active crossover can pretty much compensate for anything. If it is a 3 way speaker you want to bypass only the woofer section leaving the midrange to tweeter cross alone. 
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erik_squires
16,056 posts
 
There's a couple of issues. The preamp has relatively high output impedance, making it a less than ideal candidate for using 2 amps at the same time.

The other is the possibility of having the amp gain mismatched. You'll need some way to adjust the levels appropriately.
bdp24's avatar
bdp24
9,788 posts
 

A line-level cross-over can not necessarily be used in place the speaker-level one installed inside that speakers' enclosure. The speakers' cross-over often contains electronic parts that are used in "compensation networks" needed to optimize the behavior of the speakers' drivers. You need to get a schematic of the cross-over, to see what you are dealing with.

Some loudspeakers come from the factory set up to allow bi-amping---for instance the older .6 series Magnepans, but most speakers aren't. Are your Dunlavy's?

unsound
7,329 posts
 

In addition to what has already been posted; the Dunlavy's with their 1st order cross-overs have significant overlap, ideally you would be using two identical amplifiers.

I would not recommend bypassing the Dunlavy cross-overs, as they are custom tweaked for each pair of speakers to a lab reference.

mrdecibel
3,063 posts
 
Specifically, the amp with the higher gain ( the amp that plays louder at the same preamp level ) would need to have a stereo input level control, so you can turn it down a bit. The Bay has plenty, just type in " passive level control ". Douk Audio comes to mind ( they make xlr and single ended ), and Schiit ( the company ) makes a passive called the Sys, which is single ended only. Hope this helps. Enjoy ! MrD.
mijostyn's avatar
mijostyn
8,570 posts
 
If you do not have gain controls on at least one of the amps you have a problem. The major benefit of biamping is to be able to bypass the crossovers in the speakers and instead use an electronic cross over between the preamp and the amplifiers such as the DBx 223xs. This allows  you complete control of levels and cross overs. I do not know of any unit that gives you just gain control although you could rig a box with just potentiometers in it. 
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