[oneinthepipe]

I was reading a thread on The Tube Circle that prompted my thinking again about bi-amping my HT2-TL.  With my current gear, I would use the AVA U70 on top and the AVA Insight 440 on the bottom.  If I were to try bi-amping, I would likely purchase a Marchand x-over. 

There might have been a thread some time ago about active bi-amping, but I just can't seem to find the thread.  Does anyone have any experience with actively bi-amping their Salks?  Also, if Dennis or Jim can tell me what crossover frequency and slope would be necessary, I will look into x-overs further.  I know that electronic x-overs can introduce additional noise into the amplification.  I wouldn't likely consider a pro-audio x-over.

Thanks,

1 INTHEPIPE 

[DMurphy]

I assume your objective here is to combine the "sweet" highs of a tube amp with the guts of a SS for the woofer.   Before I go any further, I'm willing to bet that any differences you might actually hear in the highs between a tube amp and a SS are due either to simple frequency response deviations or to higher harmonimc distortion with the tube device.  But I know you tubies are convinced, so I won't bother to try and change your religion.  (Just don't try to convert me.)  Those issues aside, any advantages that biamping might confer in terms of having a dedicated amp for each driver are outweighed by the sacrifice in precision that will accompany the forcing of 4th order electrical crossover slopes onto complex driver responses that require more careful optimization.  I've gone down that route before.  Back in the day, I bought a Dynaudio Gemini MTM kit from Madisound and wasn't happy with the passive crossover.  I didn't know how to design crossovers at the time, and ordered a fairly sophisticated and expensive electronic crossover with 4th order Linkwitz-Riley electrical slopes.  I actually preferred the active system , but revisited the issue when I acquired measuring and optimization software and learned how to use it.  I was able to design a very simple passive crossover that optimized the acoustic slopes of the drivers taking into account their inherent response characteristics, and it ran circles around the active version.  Plus, I didn't need all the expense, complexity, and jumble of  cables of the active setup.  So my advice is----don't go there.   But to more important matters--what happened to the AudioCircle link on Jim's web site? 

[TJHUB]

IMO, as a tube lover, you'd be missing the sweet midrange from the tube amp.  I wouldn't bother...

[oneinthepipe]

Settled, I am not going there.  Thank you both for your advice. 

Prior to your posts, I thought the contraindications to active crossovers were related to additional equipment costs and component noise.  Dennis was correct in his assumption about my inquiry, but I certainly would not want to otherwise modify the characteristics of the speaker or lose any of the benefits of Dennis' crossover design.   

Regarding the important matter, the AC link is on the Salk site in the top menu under COMMUNITY, then pull down to Forum.

[DMurphy]

Regarding the important matter, the AC link is on the Salk site in the top menu under COMMUNITY, then pull down to Forum.

I should have known a private investigator could figure it out.  But for us economists and other non-sleuths, I think that was a bad move. 

[jsalk]

oneinthepipe -

I see that you already decided not to go that route, but since you asked, I thought I might post an answer in case someone else was considering this.

There are two basic ways to accomplish this.  The first is to simply feed the preamp outputs into both amps and connect one amp to the tweeter section and one amp to the woofer section. In this case, you are still relying on the passive crossover to deal with the gain, slopes and phase.  This is the easiest way to do it.  HOWEVER, it will only work if both amps have the same gain.  You can check with Frank to find out if your AVA amps meet this criteria (I doubt they do, but it would be worth checking.  And Frank may be willing to adjust the gain of one or the other amps to meet this criteria.)

The second approach would be to go fully active.  You would simply use an outboard crossover rather than the internal passive crossover and the outputs of the active crossover would feed the two (or three) amps.  In this case, YOU MUST remove the passive crossovers and run wires directly from the drivers to the speaker binding posts.  This will NOT work leaving the existing crossovers in place!

Going fully active is not all that difficult to do with DEQX or TacT.  But with other electronic crossovers, you would have to determine the proper slopes, gain, etc. and know exactly what you are doing.  Make one mistake in the setup and your ribbon tweeter will be destroyed (I know, having destroyed a few ribbon elements by feeding them lower frequencies than they can handle.)

Finally, two additional comments: 

First, one advantage of going active (or bi-amping) is that you relieve a single amp from the duty of driving both the top end and deep bass.  This makes a lot of sense in a 3-way design like the HT3's.  It makes less sense for a typical 2-way in that the tweeter does not draw all that much power in the first place.

Lastly, my experience has been that active set-ups can do wonders with lesser drivers.  But with great drivers and Dennis Murphy crossovers, you simply can't get much better than the sound quality you get from a stock passively crossed speaker.  Dennis' crossovers are so good, there simply isn't much room for improvement - so don't expect it.

I hope this helps.

- Jim

[DMurphy]

Jim--you make a number of good points (not including your appraisal of my crossovers, of course).  And I think you may have tempted the pipester to try the simple biamp approach using the existing crossovers, since he seems to be more concerned about the quality of the tube sound, not just relieving the woofer amp of other duties.  I was going to suggest that, but I wanted you to make the fist move because I wasn't absolutely sure how you wire the crossovers.  I take it each filter has it's own separate ground, and that single amp operation is effected by jumpers between the two sets of binding posts? 

[jsalk]

Dennis -

Jim--you make a number of good points (not including your appraisal of my crossovers, of course).  And I think you may have tempted the pipester to try the simple biamp approach using the existing crossovers, since he seems to be more concerned about the quality of the tube sound, not just relieving the woofer amp of other duties.  I was going to suggest that, but I wanted you to make the fist move because I wasn't absolutely sure how you wire the crossovers.  I take it each filter has it's own separate ground, and that single amp operation is effected by jumpers between the two sets of binding posts?

That is correct.  If we provide bi-wire (or bi-amp) binding posts, the grounds are separate and we normally ship the speakers with jumpers installed (which obviously need to be removed if bi-wiring or bi-amping).

- Jim

[TJHUB]

Great information Dennis and Jim.  Thanks.  And geez Dennis, take a deserved compliment from Jim.   There are many of us Salk customers that want to believe you really are exceptionally amazing at engineering crossovers.  Don't take the dream away! 

BTW Dennis, you're missing out by not listening to tubes!!

[oneinthepipe]

Dennis -
That is correct.  If we provide bi-wire (or bi-amp) binding posts, the grounds are separate and we normally ship the speakers with jumpers installed (which obviously need to be removed if bi-wiring or bi-amping).
- Jim

I can't currently drive both amps from with the same preamp because of gain and/or impedance dissimilarities between the amps.  Frank has considered standardizing AVA amp input requirements in the future, I believe.

I should have known a private investigator could figure it out. 

Licensed and bonded. 

Confidentiality assured.   



"Membership in LPDAM has become an honor and privilege, a badge of professionalism recognized by the general public, the legal community and government agencies alike."
 

"You can run, but you can run." 

[DMurphy]

Great information Dennis and Jim.  Thanks.  And geez Dennis, take a deserved compliment from Jim.   There are many of us Salk customers that want to believe you really are exceptionally amazing at engineering crossovers.  Don't take the dream away! 

BTW Dennis, you're missing out by not listening to tubes!!

Actually, I listen to tubes all the time.  That's why I think Frank is such a genius.  He can make a modestly rated tube amp drive difficult loads--and sound almost as good as his SS amps. 

[oneinthepipe]

... Frank is such a genius.  He can make a tube amp ... sound almost as good as his SS amps.

 

[doug s.]

I can't currently drive both amps from with the same preamp because of gain and/or impedance dissimilarities between the amps.

http://www.tweakaudio.com/Ultimate%20Attenuators.html

or, if you know the exact gain mismatch:
http://www.tweakaudio.com/Fixed%20Volume%20Ultimate%20Attenuators.html

doug s.

[kip_]

oneinthepipe -


Lastly, my experience has been that active set-ups can do wonders with lesser drivers.  But with great drivers and Dennis Murphy crossovers, you simply can't get much better than the sound quality you get from a stock passively crossed speaker.  Dennis' crossovers are so good, there simply isn't much room for improvement - so don't expect it.

I hope this helps.

- Jim

You don't think 300db per octave crossovers or active room correction would be worthwhile?

[DMurphy]

Well, I haven't heard any advantage to the super-steep crossover slopes you can get with DEQX, but there's no denying bass management is potentially a significant benefit.  At least for one listening position, anyhow.  I think Jim was addressing the practical benefits of active crossovers in the normal crossover range. 

[jsalk]

kip_

You don't think 300db per octave crossovers or active room correction would be worthwhile?

Good question!  I did not address either of those issues.

As for the steep slopes, that is an advantage if you need them (an example of which might be dealing with nasty cone breakup).  But in general, I wouldn't regard this as a huge advantage.

Room correction is another issue and is one real strength of these systems.  But you don't really need to go active to take advantage of these capabilities.  DEQX, for example, is happy to correct for room modes with a passively crossed speaker.

If you take advantage of room correction capabilities by going active, on the other hand, be prepared to pay a high price.  With a 3-way, you are talking about six channels of amplification in addition to the cost of the active crossover component.  In the case of an HT3 set-up, this can easily double the cost of a system just to derive the benefit of room correction.  Often, judicious use of room treatments can get you a long way there at a much lower cost.

In the end, each approach is all about trade-offs and each person will find their individual sweet spot.

- Jim

[Nuance]

Dennis, you are "The Man."  Just accept it and carry on.