Active bi-amping questions

[vnzbd]

Hello all, I have several questions concerning active bi-amping. My current system is Chorus II's with crossover upgrades and the mid/highs seperated from the bass. They are driven my an Emotiva 5 channel amp, 2 channels for the lows and 2 channels for the mid/highs. The upper end has been attenuated with a f-mod on the input of the high channels of the amp. Based on everything I have read this is passive bi-amping. I would like to experiment with active so here are my questions.

If I bi-amp the active crossover goes between the preamp and amp. The entire lowpass crossover(inductor and bypass cap) come out. Correct?

For the upper end the passive crossover stays in the circuit. Correct?

The active crossover will completely control the lowend, while the upper end does what? I am guessing that you would set it at or maybe an octave down from the passive cross over point to remove the low freqs.

In my experience in car audio crossing over for the sub is best with a steeper filter like a 24 db. The Chorus II cross over at 600hz, what type of slope is suggested for the low pass and high pass?

What active crossovers has anyone used that allows for different slopes and uses rca ins and outs?

Any input and education on this subject is appreaciated!

[DrWho]

Ideally you'd remove the highpass filter on the MF, and then use the active xover to get the blend at the xover frequency.

[Chris A]

The entire lowpass crossover(inductor and bypass cap) come out. Correct?

That's the way I'd do it, at least initially. If you want to time-align the midrange to the tweeter using delay in the active crossover (if it is a digital crossover), then you'll have to disconnect the midrange from the passive crossover and use three amplifier channels per speaker.

For the upper end the passive crossover stays in the circuit. Correct?

That's the way I'd do it if I weren't tri-amping.

The active crossover will completely control the low end, while the upper end does what?

It will highpass the high end (tweeter-midrange with passive crossover in between them). The tweeter-midrange relative gains will already be balanced due to the portion of your Klipsch passive crossover network that is still in the circuit.

what type of slope is suggested for the low pass and high pass?

As steep as you have available (e.g., 24 or 48 dB/octave) on the active crossover - I recommend Linkwitz-Riley (L-R) if you have a choice in crossover type.

What active crossovers has anyone used that allows for different slopes and uses rca ins and outs?

You've got me - I run XLRs and it's great at suppressing 60/120 Hz hum. Guitar Center stores have a lot of RCA-XLR cable types available. Some of the older Rane crossovers appear to use non-XLR (unbalanced) connectors, although they look to be 1/4" connectors.

Active Bi-amping/Triamping FAQ

Chris

[vnzbd]

Thanks for the input guys. Other than using the crossover as a crossover, what other uses(time alignment?) should I look for?

If a car audio product were avalable, any reason not to use it?

[Chris A]

Other than using the crossover as a crossover, what other uses(time alignment?) should I look for?

Look for dynamic range (100+ dB), low noise (e.g., -90 dB, etc.) and low distortion (<0.01% THD and IMD) if you can afford it. I'd stay away from units that have a lot of electrolytic capacitors in the main audio channels (i.e., this doesn't include the power supply), but you may not hear much difference it the unit has them. One unit that has been modded by folks to reduce/remove electrolytics is the Behringer DCX-2496 - which is a very low-cost unit.

I'd opt for a "2-In, 6-Out" unit over a "2-In, 4-Out" unit since you may wish to go with tri-amping later when you hear the difference in bi-amping and want to know what tri-amping will sound like.

I'd stay with digital active designs - not analog ones, but that's just my humble opinion. Digital crossovers have full capacity to do time correction for even very large bass bin delays - like the type you see in Khorns, La Scalas, Belles, and horn-loaded subs.

If you shop by price - better crossovers usually cost more.

If a car audio product were available, any reason not to use it?

My experience with car audio equipment in the far past hasn't been spectacular, but that was a lot of years ago: YMMV. If you can borrow a unit or get a unit very inexpensively, it may be "good enough".

Chris

[vnzbd]

I have been researching active crossover online and at local music shops and one that has been recomended was a dbx unit, 233xl. It is a 2 way unit, appears very simplistic(a plus for me!) and comes in well under $200. It has xlr ins and outs that should match well with my amps inputs. Any opinions on this unit?

Also as some of you out there use pro amps and related equipment, how about pro speakers? Do they not blend well into a home enviroment soundwise, waf, etc?

[Chris A]

one that has been recomended was a dbx unit, 233xl. It is a 2 way unit, appears very simplistic(a plus for me!) and comes in well under $200.

It looks like it will do the job. I've not heard one before.

Also as some of you out there use pro amps and related equipment, how about pro speakers? Do they not blend well into a home enviroment soundwise, waf, etc?

You can see in my profile the big black speakers in each corner. WAF isn't high visually but the sound that comes out of them is the WAF attribute. They blend very well with the other speakers in-room (they have a huge soundstage).

Pro speakers are often designed to be used together in arrays and usually have good directionality figures. If the designed coverage angle of the speakers is good for your room (60-90 degrees horizontally, 45-60 degrees vertically), then you actually have a better solution than many home audiophile speakers. For instance, the Danley Synergy series, EAW, etc. have very good directionality. Some companies have cinema lines separate from their commercial-touring lines. I'd look at the cinema lines first.

Look carefully at the frequency response and angular coverage patterns (horizontal, vertical), and whether or not they require active crossovers (suggested crossover points, EQ and delay settings), then determine whether or not they will require subwoofers.

Some manufacturers even quote distortion figures (THD, IMD at rated output)--something typically absent from home hi-fi speaker specs.

Chris

[DrWho]

I have been researching active crossover online and at local music shops and one that has been recomended was a dbx unit, 233xl

What are you using for amplifiers and preamp?

[Marvel]

Just to note that the DBX 223 is an analog crossover, so there would be no eq. or delay available.

Bruce

[Invidiosulus]

I would love to try one of the MiniDSP units,

http://minidsp.com/onlinestore/detail/15-minidsp-in-a-box/flypage/63-minidsp-2x4-revb?sef=hcfp

[Chris A]

I would love to try one of the MiniDSP units

Clearly, if cost were the driving factor and you are willing to DIY, I'd try the miniDSP for grins, however the total cost of implementation approaches the cost of a Behringer DCX2496 unit (I've seen them as low as ~$260US new) and there is at least one upgrade available for the Behringer unit (e.g., tubes, improved caps, etc.), and it is a 2 x 6 unit, which is perfect for tri-amping 3-way speakers.

Chris

[jorjen]

Don't forget to be mindful of any possible impedance mismatches, especially between the pre and the DBX unit. Input impedance on the 233 is 50k balanced and 25k unbalanced. You should be OK with a large variety of preamps but not all. Don't know what preamp you are using but tubes and pro gear can be problematic in this area at times.

[vnzbd]

My preamp/processor is a Marantz avr(8500) I use the pre outs into an Emotiva XPA-5(5 ch) amp. The amp has rca and xlr inputs. My thoughts were an rca to xlr conversion on the input to the crossover and xlr to xlr - crossover to amp.

As far as the dbx being an anolog unit vs digital, what does that mean to the end result? Is time alignment actually an adjustment to bring all the drivers voice coils in vertical alignment?

I will say my main interest is to see the effect on the bass without the passive crossover. I have some experience in the car audio world with passives being replaced by active and I can say the difference was significant in that enviorment. The thought of triamping is a little intimidating at this point but in time...

Thanks for all the input and education.

[Invidiosulus]

I would love to try one of the MiniDSP units

Clearly, if cost were the driving factor and you are willing to DIY, I'd try the miniDSP for grins, however the total cost of implementation approaches the cost of a Behringer DCX2496 unit (I've seen them as low as ~$260US new) and there is at least one upgrade available for the Behringer unit (e.g., tubes, improved caps, etc.), and it is a 2 x 6 unit, which is perfect for tri-amping 3-way speakers.

Chris

d'oh, I'm even a member of the 2496 yahoo group.

[kevinmi]

I've used the Behringer 2496 crossover and the background noise was too much for me. I have a Pyle Pro now and it is even noisier! But I'm using very low wattage tube amps (2 w/channel) and I've been told that can be a problem with some active crossovers.Many active crossovers are meant for pro use,and may not be as quiet as we would like for home use.

[DrWho]

My preamp/processor is a Marantz avr(8500) I use the pre outs into an Emotiva XPA-5(5 ch) amp. The amp has rca and xlr inputs. My thoughts were an rca to xlr conversion on the input to the crossover and xlr to xlr - crossover to amp.

As far as the dbx being an anolog unit vs digital, what does that mean to the end result? Is time alignment actually an adjustment to bring all the drivers voice coils in vertical alignment?

The reason I asked is because that particular dbx unit isn't exactly the most audiophile sounding piece of gear. It serves a purpose in the proaudio world, but for home audio, there are other options I would consider first.

The biggest advantage to time-alignment is the steering of the vertical lobe, and then improving the sound of sharp transients (like snare hits). Rane has an interesting article showing the vertical lobe considerations:
http://www.rane.com/note160.html

As far as the transient details, you will notice a bigger difference aligning the tweeter and squawker. Btw, the transients I'm talking about are different than the time-domain stuff mentioned in the Rane article.

[vnzbd]

DrWho, thanks for the responce. I will certainly read the rane article. I was poking around on the web and found and article on time alignment on the ChorusI (I have the ChorusII, but would expect the same results). It discusses time alignment with the Chorus with measurements and sound. It seems the sound was preferred stock but it measured poorly VS being aligned to measure well with less pleasing sound. I guess it is just all an experiment.

The link to the article: http://www.nutshellhifi.com/MLS/MLS3.html

As always thanks for the education.

[DrWho]

DrWho, thanks for the responce. I will certainly read the rane article. I was poking around on the web and found and article on time alignment on the ChorusI (I have the ChorusII, but would expect the same results). It discusses time alignment with the Chorus with measurements and sound. It seems the sound was preferred stock but it measured poorly VS being aligned to measure well with less pleasing sound. I guess it is just all an experiment.

The link to the article: http://www.nutshellhifi.com/MLS/MLS3.html

As always thanks for the education.

That's a very interesting article. Just to throw one comment out there in response....that is a perfect demonstration of how the power response is more important than the on-axis response. The tractrix profile beams a bit as you go higher in frequency, so you need that slightly tipped response. I agee that the chorus woofer is voiced a bit soft, and definitely prefer bringing it up, but you gotta keep the shape of the squawker with the tilted response. It is only when you go with a constant directivity speaker that the on-axis can be perfectly flat (that is the only way to have both a flat power response and flat on-axis response at the same time).