External crossover/bi-amping setup

[TheOrb]

I’m hoping some of you knowledgeable SN folks can help me better understand the whole external crossover/bi-amping concept, or at least confirm my understanding. I recently purchased a Sansui CA-5 X-over/channel divider with the intention of connecting it to my old Sansui pre-amp and using it to bi-amp my speakers and run an active sub as well.

 

So I get that for ultimate bi-amping, you would not have passive X-overs, but if I set the active ones to match the speaker’s in-built ones, then everything should be fine, right? And it means I get to amplify higher and lower frequencies separately through the speakers and run the sub as well. Are there any pitfalls or other considerations I should be aware of? 

[sir sanders zingmore]

2 hours ago, TheOrb said:

I set the active ones to match the speaker’s in-built ones, then everything should be fine, right?

Not 100% sure what you mean but it sounds as if you’ll effectively be doubling up on the crossover. That is, unless you are going to disconnect the built in ones and only use the external one. 

[TheOrb]

Thank you, sir. Yeah, my point was, I know they’ll be doubling up, but if the cutoffs are the same or similar, then it doesn’t matter, right? I’m not actually trying to alter the speakers’ separation between high and low, other than for the sub. The goal is to bi-amp and have that sub channel (because the old pre-amp doesn’t have a sub out).

[sir sanders zingmore]

17 minutes ago, TheOrb said:

Thank you, sir. Yeah, my point was, I know they’ll be doubling up, but if the cutoffs are the same or similar, then it doesn’t matter, right? I’m not actually trying to alter the speakers’ separation between high and low, other than for the sub. The goal is to bi-amp and have that sub channel (because the old pre-amp doesn’t have a sub out).

If you are just adding a sub then you won’t be operating in the speakers crossover region at all (if I understand you correctly). You’ll be blending the sub with the natural roll off of the bottom end of your speakers (and not touching the region where your speakers cross between woofer and mids)

Applying an external crossover in this region can be very useful as you can “shape” the roll off of your speakers to blend better with the sub. You don’t need to limit yourself to just matching the speakers natural roll off

[TheOrb]

Ok that makes sense, except that I should set the low (subwoofer) setting on the channel divider at around 80–100, which would enctoach slightly on the speakers’ domain, which go down to 35, yes? And I’m thinking that given the speakers’ X-over is 3700, I should try to match that on the channel divider.

[Keith_W]

You are proposing running two crossovers in series? That would double the order of the XO. For example, if you had a Linkwitz-Riley 2nd order (12dB/octave) and you add another LR2 in front of it, it will become an LR4 (24dB/octave). It would also double the phase rotation, and the manufacturer of your speaker likely designed the crossover to ensure there was no phase cancellation at the XO point. Who knows what would happen if you were to do this. 

 

As @sir sanders zingmore said, a better approach is to bypass the passive XO inside your speaker and replicate the configuration externally. To do this, you need to look at your passive XO and understand what it is - what is the XO point, filter order, filter Q (Butterworth, Linkwitz-Riley, Chebychev, Bessel, etc), and note whether there are additional components in the XO such as all pass filters or notch filters. If you understand electronic XO design, you should be able to reverse engineer it quite easily. If you don't, then the only way is to measure it by sending a sweep through the XO and measuring the output to understand the transfer function. 

 

If you are going to the SNA show today we can meet up and chat. 

[andyr]

Mmmm ...

 

5 hours ago, TheOrb said:

I’m hoping some of you knowledgeable SN folks can help me better understand the whole external crossover/bi-amping concept, or at least confirm my understanding. I recently purchased a Sansui CA-5 X-over/channel divider with the intention of connecting it to my old Sansui pre-amp and using it to bi-amp my speakers and run an active sub as well.

 

OK - firstly, if you want to biamp your spkrs ... basically, to get any worthwhile benefit, you need to remove / bypass the internal, passive XO; you really only get a benefit from using more than two amplifier channels when you use an active XO.  If you want to understand why ... go to Rod Elliott's site.

 

5 hours ago, TheOrb said:

 

 

 

 

This Sansui device is very confusing; I would suggest you really need to get hold of the User Manual.

 

I note that it says "100v", tho - so you need to use it with a step-down transformer.

 

2 hours ago, TheOrb said:

Ok that makes sense, except that I should set the low (subwoofer) setting on the channel divider at around 80–100, which would encroach slightly on the speakers’ domain, which go down to 35, yes? And I’m thinking that given the speakers’ X-over is 3700, I should try to match that on the channel divider.

 

You haven't specified what spkrs you have - so we can't answer this Qu of yours "which go down to 35, yes?".  But your comment that "speakers’ X-over is 3700Hz" implies they are 2-way?

 

If so, as the others have said ... use the Sansui device simply as a 2-way XO between sub(s) and main spkrs - in which case, setting this XO point to 80Hz is a sensible idea.

 

Edited October 11, 2024 by andyr

[TheOrb]

Thanks to all

[Domo]

I don't use a sub but don't they usually have a crossover in them?

I'd try using your Sansui in 2-way mode on your main speakers, experiment with the crossover frequency, and wire the high and low frequency amp outputs directly to the speaker drivers, bypassing whatever's in the cabinets.

[andyr]

4 minutes ago, Domo said:

I don't use a sub but don't they usually have a crossover in them?

 

A "crossover" is a low-pass (LP) filter coupled with a high-pass (HP) filter - which allows you to roll off the mains, to match the sub's selected roll-off.

 

Some sub amps merely have a LP filter.

 

Edited October 19, 2024 by andyr

[Domo]

16 minutes ago, andyr said:

 

A "crossover" is a low-pass (LP) filter coupled with a high-pass (HP) filter - which allows you to roll off the mains, to match the sub's selected roll-off.

 

Some sub amps merely have a LP filter.

 

Oh right, yeah well if you want to cut the bass on the mains and leave it for the sub.

OP says he'd set the XO to "80-100hz" but photos seem to show the lowest frequency setting is 200hz. Dunno how that would go but might be fun to try it out.

Edited October 19, 2024 by Domo

[andyr]

2 minutes ago, Domo said:

Oh right, yeah well if you want to cut the bass on the mains and leave it for the sub.

 

Why wouldn't you want to "cut the bass on the mains and leave it for the sub"?

 

After all ... this is what the XOs in the mains do (roll off the lower frequencies at the same time as bringing in the higher frequencies)!