With a decibel meter from Radio Shack. Send music or tones through each amp and get a reading. Set the level controls on the amp so they match the output for the tones on each amp. Make sure everything is the same - that is same tones and same distance from speaker for the meter with each amp. You can attempt to do this by ear but the meter is more accurate. |
How to perform a gain match two amp if they are the same made but different model has different power output? However both of them have output control L/R too. |
even if you have 2 amps of the same model, I would still be weary of a vertical setup, unless they are a monoblock pair sold as such, or at least factory matched.
amps are like people, to a certain extent, it's a nature/nurture kinda thing.
IF you've got 1 amp that is used 12 hours a day, hard, and another amp that is used only for 30 minutes on weekends, it doesn't matter that they are sequential serial numbersa, they are going to be different sounding (to some extent).
With a Horizontal setup, the highs will sound the same from right to left, and the lows will sound the same from right to left.
With a vert setup, one speaker would be getting the benefit of a more broken in amp, while the other speaker would suffer comparatively from the newer amp.
Some manufaturers will match the amps, output wise for a fee.
Unless the amps were a pair of monos, or had been factory matched, I'd still use the horizontal setup, basically for right to left continuity and consistency. |
I would think that shunting the input should negate all but the highest levels of crosstalk. After all, the input is where the "leakage" would have the most chance to be picked up and amplified as that is where the circuitry would offer the most gain. Shorting the input jack to ground would in effect shunt the "leakage" to ground at the same time, making the test far less realistic in terms of real world operating conditions. That is why i thought a Cardas Cap might be worthwhile, as you would only hear the "internal leakage" within the amp itself with minimal influence from outside sources.
One other thing just came to mind. I would guess that someone with HIGHLY sensitive speakers might hear more "crosstalk" simply due to the fact that the speakers allow more to be heard with less amplitude signal sent to them. As such, someone with K-Horns, K.A.R's, etc... may think that their otherwise "excellent" amp is "leakier" than someone with an amp that is actually much poorer with a pair of 86 db speakers. I guess that is why it is "good" to have test equipment and dummy loads to document such things. You at least end up with consistent and repeatable conditions that can be used from component to component. This allows one to have a specific baseline to work from. Sean
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Sean, the unused channel should probably be grounded, although that doesn't actually simulate operating conditions. So, I'd suggest alternately terminating the interconnect with another bit of local gear (like the output of a CD player not playing but on...
In lab tests the other channel is usually grounded.
Obviously the best separation is going to be a set of monoblock amps with separate supplies and chassis. That should be nearly infinite. Everything else is less.
I don't have any figures at hand for commercial amps, but they should be close to the noise floor unless there is a problem modulating the power supply at high loads (there can be). But this should not show up until you really suck some power. Or, on occasion there is radiation due to the current drawn through a conductor.
(you can make a nifty thing using a loop of wire as a transmitter, like around the room, and an inductor on the input of a preamp fed to an earphone - you can "broadcast"
directly on audio that way) |
Bear, good idea about the dummy load and listening for "bleed through". Simple and quite effective. Do you think that removing the interconnect from the input of the "dead" channel and using something along the lines of a Cardas cap be of any further assistance while doing this test ?
While i have never done any "controlled" testing and taken measurements, i would think that -30 to -40 db's "should" be pretty easy to achieve. What are some figures of amps that you would consider to offer good to excellent channel separation ?
I agree with getting the passive crossovers out of there. It is amazing how much even a single "high grade" cap in a simple 6 db crossover can destroy the sound of a speaker.
I also agree with your comments regarding the Carver amps. Those speakers are capable of performance well beyond those specific amps, especially if the passive crossovers are bypassed.
Mar, in vertical bi-amping, let's say that we have amp A and amp B. You would hook up amp A to one speaker and amp B would go to the other. Amp A's right channel would drive the woofers and the left channel would drive the ribbons. Amp B's right channel would drive the woofers on the other speaker with the left channel driving the ribbons.
Obviously, i selected left / right channels just for demonstration purposes as one channel should be the same as the other and they don't have preferences as to what they drive. Sean
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Thanks to all for the in depth advice. I believe I understand the set up to do the horizontal bi amp,
how would the hook up for vertical bi amping differ as
this is the set up most use with the carver amazing speakers
according to my research on the Audioreview site?
Thanks again for all the imput.
Mar4004 |
Choose wisely, Luke Skywalker! That's the best advice for bi-amping. I would NOT use Carver amps at all for anything except maybe Sub Bass. Why? Because they are not particularly low in distortion or pleasing in subjective quality to my ears...
Having said that, I agree with Sean about the relative merits of "vertical" vs. "horizontal" amp application.
You can check your crosstalk by putting a dummy load on one
channel of your amp, the speaker on the other, play the signal ONLY into the one channel with the dummy load at normal listening levels, and see what you hear (if anything) from the speaker. That's your crosstalk in practical terms.
It should be >30-40dB down worst case.
I'd try to find a very high quality amp for the top end... since that's whats going to effect the overall quality of the sound that you hear. The highs have an inordinate contribution to what you perceive out of a speaker...
If you bypass the crossover in the speaker, and go with an electronic crossover, you might be pleasantly surprised at how much better the ribbons can sound without the Carver
parts in there... Since the ribbons themselves without the xover are almost completely resistive, it is a very easy load to drive, so you only need a sweet sounding amp, not one that is both sweet and can drive wierd loads!
similarly, I'd swap out the caps if they are not already Polypropylenes in the HP section immediately regardless...
If you do decide to use the internal crossover, I'd set up a little box with a 1st order high pass (a cap and some resistors) to feed the HF amps (or do it internally) so that that section sees a 6dB/oct rolloff from about 1 octave below the Carver's crossover point. This will keep all the LF energy out of those amps. Automatically less intermodulation, no matter what.
Regardless, look for some nice sounding amps for the ribbon part of the speaker, imho.
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Vertical bi-amplification will work "better" if you have speakers that are a benign load on the higher frequencies and you have an abundance of power in both channels. Since the highs are relatively "coasting" in terms of power draw, the "excess" power that the supply is capable of is now available as reserve to help feed and control the much more demanding woofers. However, i must point out that this is NOT true if the amp that you are running is of true "dual mono" design since each channel has its own dedicated transformer and filter caps. As such, the supply is not being "shared" so one channel could not draw from the other. This method is more convenient than it is anything else, as it allows the amp to be placed closer to the speakers should one desire to do so.
If you have speakers that are reactive on top and multiple and / or low impedance woofers down low, each section of the speaker is pulling equally hard on the power supply. In this instance, horizontal bi-amping may provide greater benefits as you have a dedicated power supply that can cope with the demands of each frequency range on their own. This minimizes sagging of the supply for both frequency ranges simultaniously and presents a more stable stereo image. This is not to mention that this can result in less clipping being seen by the high freq drivers, which is a good thing in terms of reliability. I say this because the woofers would no longer have the capabilities to starve the power supply feeding the mids and tweeters, thus assuring them of always having adequate power to reproduce the signal.
If you gain a drastic amount of channel separation by vertically biamping, something is wrong with the design of your power amp. I say this because horizontal bi-amping is theoretically the same as running a single amp in normal stereo mode. The benefit is that you now have a dedicated power supply to each frequency range rather than to each channel. If you can hear a very noticeable difference in channel seperation using vertical over horizontal, your amps are simply poorly designed, lack channel seperation and are high in crosstalk between channels. If you are able to obtain excellent channel separation and imaging in stereo mode with one of these amps, you should be able to do the same with two of them in horizontal mode.
Obviously, the one drawback to vertical bi-amping is that you obviously need two identical amps to do this. One can horizontally bi-amp with two different amps, so long as their gain is relatively matched.
Obviously, the ultimate set-up would be to bi or tri-amp using monoblocks. This allows dedicated power supplies for not only each channel, but for each frequency range used. Channel separation and dynamic headroom are no longer part of the equation as you should have achieved the best possible in such a situation. That is, if the amps were selected so as to easily provide enough power under any conditions to each of the drivers it is connected to. It is possible to use a dedicated amp for each driver and still starve the driver IF the amp was too small to start off with to achieve the desired listening level. Sean
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Go to the thread on the speaker forum -- Tube and solid state biamplification for additional info. |
I have had the best luck with horizontal bi-amping. I have heard that if you can bi-amp vertically, you should be better off, because then you are actually running monoblocks. Give a separate power supply to each channel. In my experience, while using the exact same amplifiers, I lost all separation. Hence the reason I stuck with the horizontal bi-amping. I say try them both and see which one you like best. |
I aggree with Drrdiamond. When you horizontal biamp you will most likely bypass the speakers crossovers. Vertical biamping gives you the same benefits of horizontal biamping while keeping the speakers crossovers intact. Vertical biamping in my opinion is the prefered way to go.
Michael |
For what it is worth:
I actively bi-amp my speakers and set up the amps the way G13 said (horizontally), but I have two different amps. I have been told by many (including Dan D'Agostino of Krell fame) that if I had two of the same amp, I would be better off vertically bi-amping.
There reasons for this are two fold; one getting the separation advantage of monoblocks and since the bass will usually draw far more power than the highs, one amp is not responsible for delivering it all by itself.
I would be interested in why the preceeding threads recommend the horizontal configuration.
Richard |
G13 hit it on the head. I too would recommend horizontal bi-amping for this specific situation. Sean
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Not much more would need to be said Gthirteen guided you very well. |
OK,
there are 2 ways of doing this.
I would advise that you use 1 amp to drive the lows (or the bottom pair of binding posts) on each speaker, and use the other amp to drive the highs.
The only problem is that I don't know if you have 2 sets of pre outs on your preamp, or just 1.
IF you have 2 sets or pre-outs, then you connect 1 set of outputs to the top amp with interconnects, then connect this amp to the top set of binding posts of each speaker with your speaker cables.
Then connect the second set of pre-outs to the bottom amp using interconnects, then connect this amp to the low binding posts of your speakers.
So, you have 1 amp driving your woofer (or mid if your speaker is a 2 way), and another amp driving the midrange and high frequency drivers (or just the tweeters if your speaker is a 2 way).
I bet that you only have 1 set of pre outs on your preamp.
IF that is the case, and there's not a set of LINE LEVEL OUTPUTS ("RCA OUTS") on your amp, then you need a splitter, basically it's a "Y" with a male rca on the bottom of the "y", and 2 female rcas on the top parts of the "Y".
SO, you plug the bottom of the "Y" into your pre-out on your preamp, then you plug 2 sets of interconnects into the 4 "top" parts of the "y"s. THen, 1 right, and one left to each amp.
THen connect the speaker cables as mentioned above.
'Once you're SURE that all cables are properly connected, then plug in the power, and juice 'em up.
IF you did it right, turning off 1 amp will leave the highs on, while the lows go off, or vice versa.
good luck.
(If there is a set of INs and OUTs on one of your amps, then you go into that amp from the preamp, then out of the outs of that amp, into the second amp, connect 1 amp to the right and left high post, and connect the other amp to the right and left low posts)
Then |
