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I have a 7 channel amp (Halcro MC70) and only 5.1 setup at the moment, so I thought I would be clever and bi-amp my main speakers (revel studios) with the extra channels. That worked until I lost a channel and went back to single amp channels per left and right main. While on the "standard" set up, I re-booted my vinyl rig and was amazed at how wonderful and engaging the sound was, better than I remembered from before, a literal "main-line" to the recording session. It was fun seeing my friends faces as they listened. All of them naturally assumed the audiophile pose, eyes closed, rapt expression, feet tapping.Then... I got a replacement module for the amp and returned to bi-amp, using Y splitters from Audioquest, dividing the output from my Anthem D2 to two amp channels for Left and Right. I was excited to hear the results after single channel listening. Wow... what a let down! Dramatic loss of vitality, imaging and clarity.
So I went back to the single channel per speaker, connected to the high frequency posts on the speakers with the Revel bridging plates connecting the high and low frequency inputs, and voila! Awesome sound returned.
Not sure if there was loss due to the Y connectors, some kind of phase problem or maybe a bypass of the Revel crossover network in the speaker. But, done with bi amping for now..
By the way, Amy Winehouse's album "Frank" sounds awesome! She was so talented. I think this was the really "pure" Amy. "Back to Black" is awesome as well (obviously), but a little tainted by all the controversy and turmoil surrounding her at that point.. Really sorry we lost her so soon.
Edits: 01/31/17 01/31/17Follow Ups:
The input impedance of the amp is only 10k ohms. If that's correct, splitting might drop it to a level where problems occur.
If your preamp has a high output impedance, for example?
Too much is never enough
Is musically amongst the best albums I own, sonically it is a horribly compressed POS.
By denying scientific principles, one may maintain any paradox.
Galileo Galilei
easy... The output levels of the drivers changed in balance. Could be due to loading as another post suggested, or could be a mismatch in the amplifiers - a quick listen to pink noise wold bare that out. As neolith points out - you are not gaining a big advantage running full range signals through separate amplifier to both HP and LP so if you are happy stick with what makes you that way...
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
Ok, I have said it before. Biamping at the speaker level is a waste of time. In order to get the benefit of biamping, it has to be done at the line level - either actively or passively - and this becomes a big deal. Slopping a 4th order L-R at the approximate crossover frequency just ain't gonna cut it. The crossover has to be carefully designed to match the OEM that the manufacturer had in mind.
When one biamps at the speaker level there is no real crossover. What one has, is two parallel filters neither of which interacts with the other (i.e. the "rejected" high frequency from the low pass filter does not crossover to the tweeter and vv). This was not what the manufacturer set out to do.
Others may disagree, but they are wrong :).
I married the perfect woman. The downside is everything that goes wrong is my fault.
I completely disagree,Im not wrong and have been horizontally passively biamping with great benefit and no downside for over a decade. I used the exact same setup with one amp first then added the second so I KNOW.The speakers are two way and cross at 2.5K. You dont need an active crossover to prevent the HF amp from wasting its power on (unused) LF information for instance. With info fed to the HF amp the crossover in the speaker filters out everything below 2.5K at a third order slope (in my system). Because the LF info is filtered out and unused there is no load at those frequencies. No LF info has EVER lit the peak lights on the CJ amp, only midrange info like a snare hit, piano note or guitar twang has lit it. What does that tell you? The same is the case on the LF amp with HF info although one would likely not see the result of this ever anyway as bass consumes much much much more power. Frequencies under 300hZ likely consume 70% or more of an amps total power running full range. You know that right?
Passive biamp requires very stringent adhesion to the following IMO
1) same input Z, gain and sensitivity amps
2) horizontal for more equal loading of the amps channels
Oh wait thats it its actually pretty easy. However well over 90% of the time number one is not followed. I even recommend same manufacturer for the same voicing. I hope you are not one of these all amps sound the same folk too.....So tell me all the particulars of the horizontal passive biamp(s) you have implemented that didn't work for you? I hope you are not one of those people that decides everything based on theory and numbers without actually trying.....this place is full of those types.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Edits: 02/02/17
I am happy to agree to disagree with you about speaker level crossover and I am glad that you are pleased with your setup as that is a goal for all of us.The gain and sensitivity of the amp are essentially the same thing - just expressed differently (mathematically) and I absolutely agree that the two amps need to jive regardless if the crossover is at the line-level or speaker-level. Not having the same gain or having a means to equalize the gain will doom any attempt at biamping. And I also agree with you that it is better to have the amps from the same manufacturer if not from the same series or even better identical. I don't know where your comments about all amps sound the same came from, but that premise is as ludicrous as saying all speakers sound the same - we are in agreement about that.
I am not sure about the impedance of the amps being the same but I will concede that to you without any knowledge to say otherwise. As far as the 70/30 power split at 300 hz, I thought it was 50:50 - I refer to the article by Rod Elliott . Regardless one must also consider the sensitivity of the drivers and the type of music. For example if one likes a lot of bass heavy rock music then the power requirements on the low end may need to be more than those who listen to opera. Clearly if the bass driver is not as sensitive as the tweeter either more bass power is required or a padder is needed on the tweeter. Again this is true whether the crossover is line-level or speaker-level.
Finally I am not sure I follow you on using a horizontal (v vertical) arrangement of the amps to even the power load. With horizontal one stereo amp feeds the bass channels and the other the treble channels, so it would seem the power supply of "bass" amp would be doing more work than the PS of the "treble amp" - at least if you follow your 70:30 rule. It would seem to me that a vertical setup (one stereo amp for each speaker) would even out the load better. I am not disputing your statement that horizontal is better for speaker level biamping, I just don't follow the logic. To be clear I have not done speaker level biamping in over 30 or more years, so I will concede any argument about the fine points to you.
Oh yeah, I am not a "theory purist". I have had Magenpan speakers for almost 40 years (shit I am getting old) and have always had them biamped one way or another until I got the 3.7i which unfortunately have a series XO and are not readily amenable to biamping.
BTW, I do not like to use the term "passive biamping" as it is confusing. While speaker level is passive, not all passive biamping is at the speaker level. Line-level biamping and can be active or passive - I have used both. One other point, with the Magnepan speakers, which are notorious power hogs, I have used line-level crossover with superb results. Speaker-level was not as successful. With other speakers that don't suck up watts like the Magnepans, the line-level biamping may not be as advantageous. The point being that different approaches are needed for different systems. That is why I put the ":)" in my first post "Others may disagree but they are wrong :)" .
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 02/03/17 02/03/17
Thanks for the detailed reply. I have always heard the horizontal is left right and vertical up down so vertical has one amp per speaker horizontal one amp per section if you will which in my case is LF/HF.
Cheers!@
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
I follow your comments about the parallel inputs to the speaker not interacting through crossovers in the speaker. I am confused as to your comment about it needing to be line-level. I split the output to the amplifier channels at the preamp audio out RCA jack, is this not line-level? Where else can I split the signal for each channel to get the bi-amplification of the speaker?
If I am understanding correctly, are you suggesting an external crossover that splits the high and low frequency from dual amplification for each channel prior to connection to the speaker?
And so... Output from two amp channels into left and right external crossovers, then dual outputs to the high and low frequency speaker posts?
Seemed to me that the internal crossovers would handle the full range inputs from the amplifier to the high and low freq posts and voila!, great sound. To me, it seemed more of a phase coherence problem - cables not perfectly matched or amp channels not identical.
Sorry if I seem confused... want to learn from my mistakes. Prob my next move is to call Revel..
Thanks for your feedback!
If I read your post correctly, you are taking the full signal from the preamp and splitting it into two parallel but identical signals. For the most part this is fairly innocent but this is not a crossover*. From there each amplifier is fed a full signal and only when the signal reaches the speaker crossover is the signal divided into high and low frequencies.
Here is a diagram of a vertical active biamp setup which uses to identical amps:
and a diagram of a horizontal setup which is generally used if the amps are different but could be also be used for identical amps.
* I say fairly innocent because in the rare case of using a tube pre-amp [these typically have a relatively high output impedance (> 1 kohm)] with some SS stereo amplifiers that have low input impedances, the desired ratio of > 10:1 (load to preamp out) may not be maintained. Signal splitting puts the two amplifiers in parallel and the load impedance seen by the preamp is halved.
Specifically in your case the Halcro has 10K ohm impedance which when split puts a load of 5000 ohms on your preamp that has an output impedance of 300 ohms (unbalanced). This means the ratio is 17:1 - this should be ok. However if you are using the balance connectors then the preamp impedance is 600 ohms and the ratio would drop below 10:1.
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 01/31/17
You have summarized my prior "bi-amp" setup correctly. Counted on the speaker network to handle the crossover duties. If one feeds the speakers from an external crossover, as your diagrams show, wouldn't the resulting signal be subject to additional filtering in the speaker?
Anyways. Probably gonna walk away from this one. The sound without "bi-amping" is so wonderful that I pray that nothing breaks for the rest of my life! (haha)
Thanks again for your help. Great diagrams and you clearly looked up the specs on my equipment, so thank you for that too!
Best wishes!
All the new connections you created. Did you use the same interconnects as when you were only using 5 of the 7 channels? What new cables did you introduce besides the Y's?
Also you ran seven channels of the amp for the first time. I have never seen a multichannel amp or receiver able to run all of its channels to full output. The FTC does not require them to spec wise either. So the power supply in the amp had to work a lot harder to drive seven channels than five and was not likely up to it.
When I was in the biz we measured good expensive gear that would easily give the rated output on each channel with two, three and sometimes four, but never five channels driven at once. Never.
Also some of the Revels are 6 ohm. When you remove the shorting bar to bi-am[p measure the DCR of each set of terminals with an ohm meter. If the LF section is only four ohms that also would provide a tougher load to drive and may be an issue in your attempted implementation.
So while Im glad the switch back is an improvement you owe it to yourself to do that extra research and find out some things.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
I used DiMarzio 1m interconnects. Have a set of 7. Used matching pairs interconnects for the left and right. The Audioquest Y splitters were very close (?touching) at the back of the processor.
Fascinating about the 7 channel issue. Of course, I was running analog direct stereo, so the other three channels were not being used.
I am curious about Revel in bi-amp mode with regards to your discussion. I doubt the Halcro would have much trouble, even with a 4 ohm load. I will try to measure the the resistance as you suggested. If something interesting emerges, will follow up.
Thank you so much for your thoughtful and helpful response!
I didn't realize you were not using all seven channels. The interconnects are the same. Did you use the all metal Y like this one? I used them without issue, so that means I'm at a loss then. I thought it was an Anthem amp I doubt a Halcro would have a problem either.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Similar Y adaptor, only both female connectors are on the side instead of end and side, like the image you included in your response. I would have rather had the end/side connectors, as the side/side form that I have were pretty awkward on the back of my D2.
Yeah, when listening to vinyl, have the D2 in AnalogDir mode (stereo, analog pass thru), so only two channels (or 4 if bi-amp) being used. Fascinating to think that audio or movies in 7.1 might lead to loss of sound quality.
Not sure exactly how the speaker network is configured, but since there are shorting plates, I'm pretty sure the high and low freq inputs have their own high and low pass filters and then internal crossovers to distribute the sound to the individual drivers. So, I think the problem is likely slight differences in resistance between the interconnects, crosstalk due to the close proximity of the y connectors on the back of the D2 or slight phase differences between the amp channels used to bi-amp each main channel.
From a hobbyist point of view, I'd love to figure this out. But... The sound is so good with single amp channel to each main speaker that I'm happy to throw in the towel, pour a tall frosty one and enjoy the music!
Cheers!
Maybe it is the way the crossover works?
If you used an external crossover to allow only the highs to high, lows to low, that network may suck.
Or.. if you left full range to each, the crossover system inside the speaker may not have had an easy time coping with the full range signal to each part.
My guesses...
Yes, full range. No external crossover network.
The studios seem to encourage biwiring or biamping with the low and high frequency posts. There are probably high pass and low pass filters and crossovers for the split b/w tweeter and midrange. There are two woofers that look identical, so not sure what kind of cross over exists on the low freq. side.
My guess is a problem upstream from the Revels, likely due to phase differences induced by the paired interconnect runs or subtle differences between the amp modules. Dunno. Anyways, done with the bi-amp experiment for now - sounds too good to mess with!
Full range Drivers?? And you are stuffing Two amps thru.
Clearly there's a complete lack of comprehension at work/on display.
I wws left hanging at the end of your comment. Please let me know how you would set up the system?
I wws left hanging at the end of your comment. Please let me know how you would set up the system?
Listening while I work
Not sure how you're getting work done with Amy on the screen. ;-)
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