Biamp crossover question

[Steve Gonzales]

While I run my system in full triamp mode, I've often wondered what the effects of an electronic crossover being used in a biamp configuration are?. Here is an example: JBL 4343 in biamp configuration: Low pass into an amplifier, then into the LF input terminals of the 4343's crossover, then the HP is routed to an amplifier and then hooked to the top end terminals which then divides the signal passively. So what type of interaction between the electronic crossover and the passive is taking place?. If the electronic crossover has a 12db/oct slope and the passive circuit has a 12db/oct slope, what happens to the phase?. I have assumed, that since they add, a 24db/oct slope will be the outcome and remain in phase with the LP/LF section, assuming that the LP was an even order too?. What are the other effects going on here?. What can a pure passive crossover of high quality do better than a good electronic crossover and vice-versa? Another question I've wondered about is if a stock passive crossover can be easily modified to suit a completely different driver. Here is an example: An N220 passive is engineered to work with an LE5-9 midrange. Can just the midrange section of the network be modified to work with an LE85/H92 combo without touching the HP/LP filter sections in the network? It seems to me that it would effect the whole thing. Thank you for the information, Steve G.

[Ian Mackenzie]

information overload.

in the case of biamping a JBL monitor, the woofer low pass passive filter is usual completely bypassed and the high pass filter to the mid/horn etc is also bypaased so you only get the slope of the active filter (the 4435/35 is the exeception where the active and passive high pass filters do combine

As a rule electronic active filter do intrude on the tonality of loudspeakers for hifi use with soe rare exceptions.

To be continued:

[Steve Gonzales]

It seems to me that if a 4343's passive section was completely bypassed, the midbass,midrange and UHF wouldn't get filtered. Say you were to use an M552 and cross over at 250hz. I believe that the passive is still engaged because how else would the 10" midbass, 2307/2420 and 2405 "self filter" with respect to each other?.

[Ian Mackenzie]

Sorry but only only had one minute to reply.

I don't have time to upload a schematic but what happens is the mid cone high pass passive filter elements are bypassed so there is no series capacitors or inductor shunted across the signal. Nor does the woofer have a series inductor or a capacitor shunted across the signal. Normally the horn and tweeter continue to use their passive filter elements. In the case of the 3143 network as I recall the horn and and uhf signals were via the mid filter to provide better protection from amplifier transients.

Getting back to your question.

In th case of JBL engineered systems, the filters are tailored especially for the system at hand so either active or passive will provide nearly identifcal acoustic response.

Note this is seldom the case when a diy person attempts to bi amp an existing passive crossover..

The prime benefit is better performance from the woofer in most home brew active systems. In professional applications like monitoring it results in greater dynamic range and reduces power loss in the use of passive networks.

Active crossovers however do not necessarily mean a handshake for improved fidelity for home listening. It depends on the standard of your other equipment and that of your speakers.

Sorry I do not have time to consider your other questions and i am not sure how you have your system currently arranged. This would require a complete re design of the crossover network and is best left to an experienced / qualified person with test equipment such as Clio / Leap

[Robh3606]

Hello Steve

To keep it simple when you biamp a 4343/44 you remove the Low pass filter on the woofer and 1/2 of the bandpass filter on the 2121/22. You still have the other half of the bandpass filter in line for the 2121/2 to provide a smooth transition to the compression driver as well as the rest of the crossover.


Rob

[Steve Gonzales]

Kinda already knew that stuff, gents, thanks anyway. I want to know what's going on between the passive and electronic, is there something special about the blending of them that gives the speaker it's tonal quality or a compromise for the obvious reasons?. I just used the 4343 as an example. What I should have asked was: is it that difficult to achieve the same tonal quality in a 4 way with an all electronic crossover? I've had great success with my triamped system, so it doesn't seem a stretch to do it with a four way, I need to hear from someone that has heard both, picked one, and why. There is not a bi-amp capable passive crossover in the JBL inventory that is exactly what I need. I've considered having some built but don't want to go through that much trouble if I can expect the same performance from a quality electronic. Is there something particularly better about the way a passive sounds vs. an electronic of equal quality?