Question on Active Bi-Amp

[McNewbie]

I am running active x-over on the LF drivers of my 4-way speakers - meaning the top speakers (UHF, HF and MF) remain the same (passive network) and driven by a separate/smaller amp.

There are two pairs of binding posts on back of each enclosure and two jumpers to link or isolate the speakers. I have these jumpers removed for bi-ampiing the LF drivers using Ashly XR-2001 xover.

it seems to be that removing the jumpers would still leave the passive network intact for the LF drivers so basically I am feeding the Low output of the Ashly through the stock passive network. This just does not seem correct to me so hope someone with more knowledge can let me know if this is correct or not for active bi-amping.

To me (still very newbie), it would make sense to isolate the stock network for the LF drivers then run the Low output from teh Ashly directly to terminal on the drivers. Maybe it does not matter?

Thank you.

 

[Zonker92]

I think you are correct, and that approach is not desirable, unless your speakers happen to run the woofers directly off the LF terminals. What model speakers?

You may be able to wire the woofers directly to the rear terminals, and it might be easy if they have removable / faston connectors or some such.

Doesn't the Ashley go upstream of the LF amp? (Your query seems to say that you're connecting it to the LF inputs directly.)

 

[frommerstop]

Most jumpers on "bi-amp ready" speakers connect the bass to the upper frequencies, of the passive crossover. Removing the jumpers usually then allows a signal to be fed, unaltered to the woofer, but the signal going to the second set of terminals will feed the mid, upper mid & tweeter, through their respective passive network. In affect, if you have a 4way speaker, and actively biamp it this way, you have complete control over the woofer, and at what frequency the (lower)mid comes in, but the upper three drivers will act in unison through the built in passive network.
For example, this is how an AR9 is configured, a 4way, with jumpers used to tie the two 12" woofers to the other three drivers.

Think of it as a woofer, and a three way satellite sitting on top, you can adjust the balance, and frequency of the crossover between the two, but you'll not affect the upper two thirds of the speaker... does this answer your question?

 

[McNewbie]

What model speakers?
Doesn't the Ashley go upstream of the LF amp? (Your query seems to say that you're connecting it to the LF inputs directly.)

Thanks Zonker92. These are JBL 250Ti LE. Just to clarify the Ashly goes btw preamp and the mono amps for the LF drivers.

@frommerstop: I am not not clear on the response to my question whether I should take the passive network from this equation - meaning run the LF signal directly to the speaker terminals on the drivers. This means I will need to get inside the enclosures and isolate the LF speaker wires from the network.

Regarding the xover freq setting, the JBL spec for these speakers is 350 Hz and this is what I have it set on Ashly but when I ran REW to measure FR I think it shows the filter was at ~180 Hz so not really sure why this is or not reading the response curve correctly as I am still a newbie in this area and am trying to learn how to intepret response curve.

Thanks both for your input.

 

[Zonker92]

I think that frommerstop is saying that your LF terminals may be feeding the woofer directly, with no passive crossover in the circuit, when you use the LF inputs. He's saying that many "bi amp ready" speakers are set up that way. He may be right; I had not known that.

However, if your crossover is like, or a version of, this one, for the BQ model, then in fact your passive LF crossover components would still be in the circuit. Do you have the schematic? Or can you pull a woofer and check? The woofer's DC resistance should be about the same as those of the LF terminals standing alone, if it's direct-wired. Can you post a close-up of the back panel connectors / switches? Does the owner's manual say anything? My bet is, the passive components are still in the circuit.

 

[kahlfin1k]

Thanks Zonker92. These are JBL 250Ti LE. Just to clarify the Ashly goes btw preamp and the mono amps for the LF drivers.

@frommerstop: I am not not clear on the response to my question whether I should take the passive network from this equation - meaning run the LF signal directly to the speaker terminals on the drivers. This means I will need to get inside the enclosures and isolate the LF speaker wires from the network.

Regarding the xover freq setting, the JBL spec for these speakers is 350 Hz and this is what I have it set on Ashly but when I ran REW to measure FR I think it shows the filter was at ~180 Hz so not really sure why this is or not reading the response curve correctly as I am still a newbie in this area and am trying to learn how to intepret response curve.

Thanks both for your input.

The reason the xover point is wrong is because xovers are not immediately cut off. They're a curve who's slope will vary depending on the type of xover it is. So it doesn't cut off at 350hz it starts rolling off at maybe say 20dB per octave. The 20dB is a guess and you'd have to figure out what kind of xover network the speaker has. So essential you're adding another crossover (the Ashley) with an unknown slope to the passive with also an unknown slope and in the process just creating chaos. You could open up the speaker and re-wire it to bypass the passive xover but unless you know the roll off slope it's using and can duplicate that exactly with the Ashley you're going to change the frequency response of the speaker. IMO the only thing to gain from bi-amping passive xover speakers is if you have an amp that doesn't have enough power to drive the woofers well but does really well on the highs and mids such as a flee watt tube amp. On the other hand (as I recently discovered) going ALL active takes it to a whole new level.

 

[McNewbie]

However, if your crossover is like, or a version of, this one, for the BQ model, then in fact your passive LF crossover components would still be in the circuit. Do you have the schematic? Or can you pull a woofer and check? The woofer's DC resistance should be about the same as those of the LF terminals standing alone, if it's direct-wired. Can you post a close-up of the back panel connectors / switches? Does the owner's manual say anything? My bet is, the passive components are still in the circuit.

That's the network for my speakers hence the reason I asked if I should bypass the stock passive network or not.

 

[McNewbie]

The reason the xover point is wrong is because xovers are not immediately cut off. They're a curve who's slope will vary depending on the type of xover it is. So it doesn't cut off at 350hz it starts rolling off at maybe say 20dB per octave. The 20dB is a guess and you'd have to figure out what kind of xover network the speaker has. So essential you're adding another crossover (the Ashley) with an unknown slope to the passive with also an unknown slope and in the process just creating chaos. You could open up the speaker and re-wire it to bypass the passive xover but unless you know the roll off slope it's using and can duplicate that exactly with the Ashley you're going to change the frequency response of the speaker. IMO the only thing to gain from bi-amping passive xover speakers is if you have an amp that doesn't have enough power to drive the woofers well but does really well on the highs and mids such as a flee watt tube amp. On the other hand (as I recently discovered) going ALL active takes it to a whole new level.

I know what the stock xover is JBL spec for these speakers (250Ti LE. See schematic posted above in Zonker92's reply though no xover freq there): 350 Hz, 1.2 kHz and 5.5 kHz and this is why I am setting the Ashly to 350 Hz, is this not correct?Right now I am going active only on the LF drivers.

Here's the full range room measurements I just captured today using REW and calibrated umik-1 mic adn external sound card. I am still new so am not sure what this is telling me. Am I happy with the sound sonically? Yes. The whole point for me here, I want to learn more about how active bi-amping works and how the connection should be and at the same time educate myself regarding FR curves/data collection, placements of speakers, room treatment, RTA software, etc.

Any feedback on what the response means would be much appreciated. Thanks.

 

[Zonker92]

That's the network for my speakers hence the reason I asked if I should bypass the stock passive network or not.

OK, then my answer is, use the internal network by itself OR bypass it (and set the Ashley however it should be set*), but do not use it with the Ashley upstream of it.

*I'm not qualified to advise you on setting it.

 

[fred soop]

Rod Elliott has covered this. Start at the following link .....

http://sound.westhost.com/bi-amp.htm

Short answer, connect the low frequency amp directly to the woofer. Do not pass Go, do not collect resistance or inductance. Disconnecting the jumpers on the back of the speakers will usually only disconnect connections to the crossover but the signal will still need to go through part of the crossover to reach the woofer itself. My solution, which allows for quick changes, was to mount an extra terminal block on the back of the speaker with jumpers for the crossover to woofer connections so the woofer can be directly accessed or driven through the crossover without opening the speaker cabinet. Be sure to mark the terminals well because you will forget what terminal goes to what connection after a few years.

 

[McNewbie]

Rod Elliott has covered this. Start at the following link .....

http://sound.westhost.com/bi-amp.htm

Short answer, connect the low frequency amp directly to the woofer. Do not pass Go, do not collect resistance or inductance. Disconnecting the jumpers on the back of the speakers will usually only disconnect connections to the crossover but the signal will still need to go through part of the crossover to reach the woofer itself. My solution, which allows for quick changes, was to mount an extra terminal block on the back of the speaker with jumpers for the crossover to woofer connections so the woofer can be directly accessed or driven through the crossover without opening the speaker cabinet. Be sure to mark the terminals well because you will forget what terminal goes to what connection after a few years.

Thanks much for the link :thmbsp:and just skimmed through that quickly for now and have noticed one of the bi-amp diagrams (section 1, Fig 1) shows that preamp feeds signal to active xover then Hi output of the xover connects to HF amp and Lo output to LF amp then output of HF amp goes through passive network then HF speakers, but output of LF amp connects directly to LF driver.

My current connection is different than above in that my HF signal from preamp does not pass through active xover but LF signal does. The way I have everything hooked up, it would seem that I am passively bi-amping since all signals pass through passive network then to the speakers.

When I get a chance, I will open up the enclosures to modify the speaker wires as needed for biamping the LF drivers.

Thanks.

 

[grey]

This is the part that JBL left out of the manual. :yes:

Wire the woofer directly to the amplifier. C3 will still be in the way of some of the benefits of bi-amping.

There was some recent discussion here of how JBL did this on the xpl200. This can easily be applied here. I would leave the crossover point as is for now.

The passive components should cost no more than $20 if you wanted to mimic that layout exactly.

I have the same speakers, but I've not done this to the BQ network. The thought has crossed my mind dozens of times. They do quite well with a crossover point of ~70Hz. Subwoofers handle everything below.

Let me know if you need any clarification on any of this.

 

[McNewbie]

This is the part that JBL left out of the manual. :yes:

Wire the woofer directly to the amplifier. C3 will still be in the way of some of the benefits of bi-amping.

There was some recent discussion here of how JBL did this on the xpl200. This can easily be applied here. I would leave the crossover point as is for now.

The passive components should cost no more than $20 if you wanted to mimic that layout exactly.

I have the same speakers, but I've not done this to the BQ network. The thought has crossed my mind dozens of times. They do quite well with a crossover point of ~70Hz. Subwoofers handle everything below.

Let me know if you need any clarification on any of this.

Thank you grey. I will read the link you provided. For now, you lost me about "C3 will still be in the way of some of the benefits of bi-amping". There is no "C3" in the schematic for the LF (see schem in post #5). Did I misunderstand you? I do see C3 but it's on the MF circuit and I am not messing with those.

Thanks.

 

[grey]

For now, you lost me about "C3 will still be in the way of some of the benefits of bi-amping". There is no "C3" in the schematic for the LF (see schem in post #5). Did I misunderstand you?
Thanks.

Both schematics for the 250ti BQ and xpl200 have the offending capacitor labeled "C3". It's near the second black mark down on the left hand side in post #5.

I do see C3 but it's on the MF circuit and I am not messing with those.

To bi-amp properly requires removing the passive LP and HP filter components impacting the given crossover point. I urge you to study the link provided and the Rod Elliot link posted earlier. Take your time in digesting this. There should be no rush in modifying an already good pair of speakers.

Edit/note: L3 is also part of the HP components on the 250 BQ schematic.

 

[kahlfin1k]

I know what the stock xover is JBL spec for these speakers (250Ti LE. See schematic posted above in Zonker92's reply though no xover freq there): 350 Hz, 1.2 kHz and 5.5 kHz and this is why I am setting the Ashly to 350 Hz, is this not correct?Right now I am going active only on the LF drivers.

Here's the full range room measurements I just captured today using REW and calibrated umik-1 mic adn external sound card. I am still new so am not sure what this is telling me. Am I happy with the sound sonically? Yes. The whole point for me here, I want to learn more about how active bi-amping works and how the connection should be and at the same time educate myself regarding FR curves/data collection, placements of speakers, room treatment, RTA software, etc.

Any feedback on what the response means would be much appreciated. Thanks.

350hz is correct if you are completely bypassing the LF passive network. HOWEVER you will likely be altering the frequency response by using the active unless it uses the exact same slope as the passive network. This may be a trivial difference sonically or could be huge. The slope that tye active uses should be stated in the manual. To find the slope of the passive you will need to look at the schematic and figure out what type of crossover it is and compare it to the slope of the active. If they're pretty close (say both second order butterworths) they should sound about the same. However if they're totally different you may change the response of the speaker significantly.

Sent from my ADR6300 using Tapatalk 2

 

[edwyun]

You may be able to wire the woofers directly to the rear terminals, and it might be easy if they have removable / faston connectors or some such.

Easiest solution. Worked for me. :thmbsp:

 

[Son-of-Vere]

This is why I like having this,



Makes mods like you want to do a breeze. I may also bi-amp 'em some day.

 

[McNewbie]

Easiest solution. Worked for me. :thmbsp:

I have a little bit of time yesterday so went ahead and removed the LF drivers from the enclosures to disconnect existing speaker wires from them then ran separate wires from the drivers to directly to the LF amps.

I really didn't like the sound, bass is not as tight from the LF drivers and overall sound from the upper drivers was not as good as the way I had them setup before. Not sure what it is exactly but didn't have much time to play with it longer yesterday.

Thanks.

 

[McNewbie]

350hz is correct if you are completely bypassing the LF passive network. HOWEVER you will likely be altering the frequency response by using the active unless it uses the exact same slope as the passive network. This may be a trivial difference sonically or could be huge. The slope that tye active uses should be stated in the manual. To find the slope of the passive you will need to look at the schematic and figure out what type of crossover it is and compare it to the slope of the active. If they're pretty close (say both second order butterworths) they should sound about the same. However if they're totally different you may change the response of the speaker significantly.

Sent from my ADR6300 using Tapatalk 2

Well, I didn't like the sound when running wires directly from LF drivers to the amps (bypassing stock passive network). I set the slope at 6db on the Ashly but now also noticed the overall sound was just not as good as before, the bass from the LF drivers is not as tight. Seems the LFs are lacking with this setup.

I am not sure what adjustments are necessary to improve this. I will play with the Ashly settings more when I get a chance but does not seem to be much I could play with on Ashly.

Attached (not sure how to do this) is the speakers spec so not sure how to check "slope of the passive" per your suggestion. Can you provide guidance here from the schematic attached?

Thanks.

 

[dc270]

I have soom experience with what you are doing here, have and used the XR 1001 xover, etc.
Here is a switch pannel I made to allow or use the passive networks or the active networks
http://www.audiokarma.org/forums/showthread.php?t=580337

You will have to "dial" in the Asly to get the sound you are looking for. Passive nets works, especially on the low end are real power robbers. Get the right amp(s) and the Ashly set up correctly and you ncan effectively improve you sound. The Ashly if I am correct has a slope of -24/db/oct, probably -18 more than your passives.
I am sure you can get better sound with the right amp and some "me" time with your Ashly. You might get hold of "Tomlinmgt"- I think he has one of these and can help you get set up.
DC