Active Crossover for Bi-Amping

[knotscott]

I'm considering trying an inexpensive active crossover in my horizontal bi-amp setup between the preamp and amplifiers....mainly for a high pass filter to limit the bottom two octaves in the tube amps feeding the mids/tweeters. (~ 80hz)

I've always been mainly in the "straight wire with gain" camp, and definitely have some concerns with adding another component directly in the signal path. I plan to experiment with it and see how it goes, but wondered if any of you think the benefit of removing the bottom octaves from those amps will offer enough benefit to offset any signal degradation? Opinions and experiences welcome!

Current setup configuration:


Possible setup for future consideration:

 

[swechsler]

If you're not going to rewire the internal crossovers to remove the built in high-pass for the high section, and the low-pass for the woofer, than it's probably not worth doing. IMO that's the whole point of using an active crossover.

 

[Tom Brennan]

I don't know what you're doing there or if you understand what bi-amping is. Anyway, like swechler said, if you don't remove the passive crossovers and go direct from amp to driver you're just putzing around.

 

[donprice]

Try and see how it sounds to you. MiniDSP and similar systems can add eq/room correction as a bonus and probably better control over the subwoofer.

 

[knotscott]

Thanks for the replies gents. I do understand bi-amping, but am not experienced at all with active crossovers. I know there are poor and excellent examples of each, and that bi-amping can be done horizontally or vertically, and with active or passive crossovers or both. This would be a horizontal configuration. I'm just not sure how audible or beneficial adding the active crossover will be. It's worthy of the some experimentation for sure.

The low pass passive crossover on the woofers is a candidate for removal, using just the active low pass options. The high and low pass passive crossovers on the mids and tweeters are top notch and likely to remain. The schematic Tom showed is more useful than my original pic, and has some similarities, but also some differences (shown below)



The subwoofer gets fed by the same amp that's feeding the main woofer.

For clarification, the mid/bass driver has an acoustical high pass roll off from the cabinet (no actual high pass crossover ), but the amp that feeds it currently gets a full range signal, and that's what I'm hoping to change in this "phase 1" experiment. The addition of an active crossover does pose lots of options going forward.

 

[Akustic]

My guess is yes ... But is it audible ???

I would be really interested in hearing about a comparison with, and without an active crossover ..
But that implies that you left the choke accessible..and it sounds like that may not be the case.

 

[Legrace]

Filtering the lower octaves prior to tubes as shown in diag post 5 will not deliver any SQ benefits, versus direct connection from preamp as shown in post 1, current configuration. Only adds to cabling, never a good thing.

 

[Legrace]

Recommend sub up to 100, tubes 100 to 1700, SS amp >1700. Insert sub high pass prior to tube amps.Tubes set to triode mode. Doesn't hurt to try....

 

[rothwellaudio]

If you only want to shave off some LF you could do it with a simple C-R high pass filter (capacitor - resistor) at the inputs to the power amps. If you know the input impedance of the amps you could use that as the R value and all you'd need is a capacitor in series with the input. The roll-off will only be first order (6dB/octave) but that might satisfy you. It would be a cheap and easy experiment and if you don't like it all you have lost is the cost of two capacitors and a bit of time. If you like it, happy days. Either way you'll have gained some knowledge and experience.

 

[twiiii]

I have used a Bozak N-106, 106 A and 106 B, two different Pioneer crossovers and two different UREI professional electronic crossovers. For the money I think the Urei does the best job. The Crown crossover works well as does the one made in Canada by Bryston. But if you want the ultimate Accuphase makes a great one; but, you can buy a car for the price of their crossover. There are others, Rane made good ones more for professionals as did other companies where the crossover is part of the digital processor. Shure brothers QSC, EV, Altec, JBL, Harmon, Crown, etc etc. professionally I liked Klarke-Tenik. For the dollar another great piece was the Professional Yamaha electronic crossover. I liked their professional stuff while consumer Yamaha always left me with a sour taste in my mouth sound wise.

 

[Bill Ferris]

This the one that I bought around 13 yrs. ago.
I find this very HQ digital (24 bit/96kz) loudspeaker management (AKA crossover) model to be a outstanding crossover, with a very handy firmware embedded time alignment program, that only requires one to provide a decent balanced XLR connector microphone to utilize it.

BSS Audio FDS-366T Omnidrive compact plus.
It`s now discontinued, but might find it used and attractively priced, on say eBay, etc.

 

[Legrace]

Hope OP is OK, normally would expect follow up by now.

 

[knotscott]

Hope OP is OK, normally would expect follow up by now.

All is well. Thanks for the input gang. Between a birthday and a birth this week, there have been a few family distractions from audio. All good stuff though!

An active crossover went in the system today. It's too early to draw any useful conclusions, but there are a lot of options to experiment with, and some sound differences noted. I'll start with some gross adjustments, then work to fine tune it over time. At the very least, I was enjoying what I was hearing tonight.

The concern for additional cabling is valid, and was a concern of mine also, but we'll see how it goes.

 

[knotscott]

If you only want to shave off some LF you could do it with a simple C-R high pass filter (capacitor - resistor) at the inputs to the power amps. If you know the input impedance of the amps you could use that as the R value and all you'd need is a capacitor in series with the input. The roll-off will only be first order (6dB/octave) but that might satisfy you. It would be a cheap and easy experiment and if you don't like it all you have lost is the cost of two capacitors and a bit of time. If you like it, happy days. Either way you'll have gained some knowledge and experience.

A simple capacitor/resistor high pass filter at the amp inputs is exactly where the idea started. I haven't ruled it out yet, especially if I get a better idea of what frequency to set it. It's simple enough that I may give it try. Thx.

 

[knotscott]

Update: I hooked up an active two way crossover between the amp and preamp earlier in the week, and played with the frequency options and gain settings for a few days. It sounded good....lots of air, space, and separation, but overall the crossover has added a hint of sizzle in the top frequencies that's not to my liking. It's very possible that it's cable related, and I will explore some more cable options at some point. For now, I've split the signal and have reconfigured the active crossover using only the low pass side through the solid state integrated amp, and am running the mids/tweeters through the tube amps without the active crossover. It offers more flexibility with fine tuning the bass from ~100hz down, so I still consider the experiment a positive experience at this point. I'll update again with my impressions if I make an more changes.

 

[rothwellaudio]

...overall the crossover has added a hint of sizzle in the top frequencies that's not to my liking. It's very possible that it's cable related...

Really?

 

[knotscott]

Really?

Unfortunately, yes. It's not severe, but's audible and is just one of those things I'm sort of averse to. It could be cables, or it could be op amps or something else in that circuit. It could even just need a little burn-in. The good news is that it sounds really good just using the low pass filter on the woofers. It's not an essential component in this system, and has been curiosity adventure from the get-go. I'll play around with some cables, and might even crack the hood of that crossover and see if there's any low hanging fruit to be harvested.

 

[knotscott]

In case anyone is interested, here's an update of my current layout. Three things are new for 2023.

1. Hagerman Bugle 3 - It's about 60% modified with the suggestions found here - (Impact - Significant)
2. Kenwood KA-3500 integrated amp - New to driving the woofers and frequencies < 100 hz (Impact - significant to flexibility, Moderate for overall sound)
3. Pyle PLXR-2B - Added as a low pass filter below 100hz. <$30 (plus the cost of a 12V wall wart). (Impact - Moderate)

 

[Akustic]

In case anyone is interested, here's an update of my current layout. Three things are new for 2023.

1. Hagerman Bugle 3 - It's about 60% modified with the suggestions found here - (Impact - Significant)
2. Kenwood KA-3500 integrated amp - New to driving the woofers and frequencies < 100 hz (Impact - significant to flexibility, Moderate for overall sound)
3. Pyle PLXR-2B - Added as a low pass filter below 100hz. <$30 (plus the cost of a 12V wall wart). (Impact - Moderate)

View attachment 2839799

Thank you ..

Yes I'm thoroughly interested and curious to hear what gains or deterioratons you are hearing in sound quality ..
In my experience the simplest circuit will result in the highest sound quality .. less is more.
I would guess that it would be hard to beat, or even match, the sound quality of a simple passive bi-amp ...
But pure passive seriously complicates finding the right crossover point which certainly isn't adjustable.

I have good results just using a level control on one of the amps with a pure passive setup ...
The speaker's designer chose the low frequency crossover point for reasons known to the designer ..
It's relatively easy to adjust the perceived balance of the upper and lower frequencies with the level control.

That said .. thank you for the notes on what you're hearing ..

 

[knotscott]

...In my experience the simplest circuit will result in the highest sound quality .. less is more.
I would guess that it would be hard to beat, or even match, the sound quality of a simple passive bi-amp ...
But pure passive seriously complicates finding the right crossover point which certainly isn't adjustable.
...

"Less is more" is pretty much how I cut my teeth once I jumped beyond a typical receiver setup, and I totally agree. The system sounds wonderful to me and has for years...I was just kind of curious what an active crossover could do. It definitely helps tame some room resonance near that 100 hz range....it certainly doesn't cure the room, but it helps me fine tune so that it's not emphasizing those room nodes, and most importantly, it doesn't mess up the vocals.

That said, this was a pretty cheap active crossover. Perhaps there's a cleaner sounding version that I could have tried that would have yielded different results...there may be some mods that can be applied to my unit, so if time allows I may take a look. There's also the simple capacitor/resistor high pass filter suggested by Rothwellaudio that I may try at some point, but it still raises my philosophical concern about trying to get sound imprpovements by adding something in the signal path. But it's cheap and easy, and can easily be undone, so likely worth a try.