JBl L7 crossover question...

[zxryder93]

So I have biamped my L7's and like how it's working. I'm sending full range input to the low end and using the internal crossover with terminal jumpers removed.

What I wanted to try is an active crossover for the low end. I know I can move the internal jumper on the crossover to bypass the LF components and use the active crossover instead. But I found active crossovers to be expensive. What I did find was an inline RCA active crossover emulator. There is one that does low pass at 150Hz that I want to try.

The problem is, this will not match up with the high end anymore. The bottom frequency for the high section will still cross at 180Hz, leaving a gap in frequency response. Is there any way to make changes to the high end crossover to lower it to 150Hz from 180Hz? Maybe use a calculator to find the right values for components? I wanted to do a recap anyway and don't mind experimenting, I can always put it back as long as nothing blows up.

 

[ic-racer]

S What I did find was an inline RCA active crossover emulator. .

the miniDSP?

 

[zxryder93]

This thing:

The Harrison Labs FMOD™ is an in-line active crossover simulator.

 

[homebrew]

This thing:
View attachment 1746831
The Harrison Labs FMOD™ is an in-line active crossover simulator.

Tried those a few years ago and found they robbed much of the life out of the speakers. Active crossovers can be expensive but they are the best way to bi-amp a speaker. Active crossovers also allow the user to more accurately adjust crossover frequencies, crossover slopes, and match speaker levels than passive devices.

 

[zxryder93]

Tried those a few years ago and found they robbed much of the life out of the speakers. Active crossovers can be expensive but they are the best way to bi-amp a speaker. Active crossovers also allow the user to more accurately adjust crossover frequencies, crossover slopes, and match speaker levels than passive devices.

Thanks for that info, I didn't know much about them but since they are fairly cheap thought I might try. I only want to use it on the low pass, I will use the internal crossover for the high end for now, so maybe the adverse effects wouldn't be as noticable.

I decided to recap using all the original JBL values, got Dayton audio for everything. Most 1% tolerance, all 250V so should fit on the board. I read a little on the small .01uF bypass capacitors and will take them out. The impression I got was they are there to help performance of the old electrolytic capacitors and may not be needed with newer capacitors. I'd be interested in what others think about that...

 

[DunnKrugs9]

So I have biamped my L7's and like how it's working. I'm sending full range input to the low end and using the internal crossover with terminal jumpers removed.

What I wanted to try is an active crossover for the low end. I know I can move the internal jumper on the crossover to bypass the LF components and use the active crossover instead. But I found active crossovers to be expensive. What I did find was an inline RCA active crossover emulator. There is one that does low pass at 150Hz that I want to try.

The problem is, this will not match up with the high end anymore. The bottom frequency for the high section will still cross at 180Hz, leaving a gap in frequency response. Is there any way to make changes to the high end crossover to lower it to 150Hz from 180Hz? Maybe use a calculator to find the right values for components? I wanted to do a recap anyway and don't mind experimenting, I can always put it back as long as nothing blows up.

I have my JBL L7s bi-amped with an active crossover, specifically a Heathkit vintage AD-1702.
This setup has been very succesful using a GAS Thoebe preamp to the crossover then a B&K
ST-140 for the HF and an Emotiva XPA-2 for the LF.

Your comments have me a little perplexed. The L7s are getting full range to both the HF and LF
inputs with the external shorting bars removed from a vertical (or horizonal) bi-amp setup with 2
matching stereo amplifiers? This would, as noted rely on the internal crossover to limit the spectrum
to the HF and LF. drivers. I ran the L7s in an asymmetrical horizontal bi-amp in similar fashion to you
with a slight input level mismatch but have found the full bi-amp setup a big improvement to it.

Also as you noted the crossover's internal jumper needs to be moved to the bi-amp position to enable
it. No big deal at all. DSP can act as an active crossover if need be though an active crossover need not
be very expensive. The Heathkit AD-1702 cost me about $300 is pretty flexible ans sonically has been a
pleasant surprise with the benefits it brings far outweighing any audible penalties. A contemporary 3-way
crossover from Sublime Acoustic for $600.

My setup comes close to the L7 maximum input rating of 450w with the XPA-2 ouputting ~400wpc into
6 ohms to the woofer with little observable compression or distress and with a joyous noise for sure.

 

[ernieS]

So I have biamped my L7's and like how it's working. I'm sending full range input to the low end and using the internal crossover with terminal jumpers removed.

What I wanted to try is an active crossover for the low end. I know I can move the internal jumper on the crossover to bypass the LF components and use the active crossover instead. But I found active crossovers to be expensive. What I did find was an inline RCA active crossover emulator. There is one that does low pass at 150Hz that I want to try.

The problem is, this will not match up with the high end anymore. The bottom frequency for the high section will still cross at 180Hz, leaving a gap in frequency response. Is there any way to make changes to the high end crossover to lower it to 150Hz from 180Hz? Maybe use a calculator to find the right values for components? I wanted to do a recap anyway and don't mind experimenting, I can always put it back as long as nothing blows up.

ive restored a pair of L7. I would recap the crossovers to factory spec. There’s a lot of engineering that went into this speakers. Too many cooks in a kitchen can ruin the dish so speak.

I did biamp my L7 using two RBH Sound SA-400 sub amps. That 12” driver outclassed most of my subs. What a beast.