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tom collins
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bi-amping question

Ok Gurus:

After a long search, I finally found and Arcam P80 to biamp with my Arcam A80. I hooked them together via a new interconnect and unfortunately, had to use $2.00 18 guage speaker wire from a roll while my nordost biwire cable is reconfigured for biamp (I could start another cable battle over my perception of the difference in sound, but I digress).
Now for the questions:
When mentioning my intention to another audio enthusiest, he asked if I was going to use a crossover between the amps as there might be intermodulation as the full spectrum of sound was going to both the woofers and the tweeters. Well, I never thought of that as the manual just showed the way to wire the amps up and said it is a great idea for improved sound. Well, that part is correct as in "hello bass, nice to meet you." And, with the cheap cable, I can't tell whether their is im distortion or not, but will be getting the Nordost back soon and will surely hear any problem, so that is why I wanted to ask if anyone here has had prior experience with bi-amping? If so, did you use a crossover? And if so, how did it sound? Could I be lucky enough that one of you actually did the bi-amp with Arcam equipment and could relate your experience?
I can already tell, it was the best $500 I spent on the system.
Thanks in advance for your constructive advice.

Tom

Kal Rubinson
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Re: bi-amping question

I will keep this constructive (mostly).

You simply cannot add an external crossover unless you have one custom designed for your specific speakers. No off-the-shelf electronic crossover is suitable to balance the drivers (in and out of defined bandwidth) in a way comparable to the built-in crossovers. In addition, of course, you will have to remove the built-in crossover since you do not want both filtering the signals.

That said, doing all that is the only useful way to bi-amp, imho.

Kal

RGibran
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Re: bi-amping question

Why would one think using identical amps to biamp would yield some difference or improvement? I'd suspect any differences would be more attributable to the cabling than the biamp arrangement.

RG

tom collins
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Re: bi-amping question

RG: it doubled the available power from 65 per channel to 130 per channel. the woofer now has its own 65 watt amp, trust me, you can hear the difference.

tom

Kal Rubinson
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Re: bi-amping question


Quote:
RG: it doubled the available power from 65 per channel to 130 per channel.

On paper. But, since the majority of the power is used by the woofer either way, the effective increase is marginal because it is limited by the 65w devoted to the woofer.


Quote:
the woofer now has its own 65 watt amp, trust me, you can hear the difference.

Sure.

Kal

Elk
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Re: bi-amping question

If the speakers are meant to be b-amped the appropriate parts of the crossover are already in place.

That is, once you remove the connection between the two sets of binding posts on the speakers you have direct access at exactly the correct place in the crossover; the high pass filter for the tweeters are in place and low pass for the woofers.

There is no need for an external crossover (unless I am really misunderstanding what you are doing).

The question I always have is how people bi-amp with dissimilar amps where the gain is different for each. I assume one adds an attenuator for the more powerful of the two amps so that its gain is now the same as the other amp.

RGibran
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Re: bi-amping question


Quote:
RG: it doubled the available power from 65 per channel to 130 per channel. tom

The mid/tweeter binding posts and woofer binding posts still see the same 65 watts. You are sending the entire music signal to both amplifiers and both amplifiers are amplifying the entire signal, but you are allowing the passive crossover network to filter the amplified signals. I can

dcstep
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Re: bi-amping question

Are you bi-amping or bi-wiring? I think that you want to bi-wire, if your speaker is designed for it. The advantage of biwiring is that the feedback from the drivers, particularly the woofers, is shunted back to the amp, where resistance is very low. With a single wire, the electrical current generated by the woofer may feedback into the crossover and potentially interfere with the mids and upper response drivers. Good crossovers are designed to cope with this, but a speaker designed for bi-wiring will almost always sound better bi-wired, particularly when playing a complex signal with lots of energy in both high and low frequencies.

Bi-amped systems usually come with an external crossover to split the signal before it goes into the two amps. I suppose that you could bi-amp a bi-wire speaker by sending a full range signal to both amps and then wiring each amp to the separate posts. There's worry that the two amps will not be at the same levels, but with a test CD or LP you could probably get the levels correct.

You should probably wait until you get your good cable back before worrying too much with the fine tuning.

Dave

tom collins
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Re: bi-amping question

Elk: you are the winner.... i finally thought of that late last night. yes the speakers are set up for bi-wiring. in regard to the gain, the manual specifically states that the gain is properly adjusted with these 2 units. i suspect that the integrated amp is mostly one of their p80s with the control set from their stand alone preamp added, so it is a hybrid of a monoblock setup.

other folks: the difference is not subtle at all, it went from a suggestion of bass to the bass playing an equal part to the other instruments, no one would miss it, and strangely, the vocals seem better too. the bass is a little flabby now, but i need to work on my speaker positioning again as i think it is now too close to the rear wall and will probably resolve nicely further in the room and with the nordost back in place.

thanks for all the feedback, anything else would be welcomed.

dcstep
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Re: bi-amping question


Quote:

other folks: the difference is not subtle at all, it went from a suggestion of bass to the bass playing an equal part to the other instruments, no one would miss it, and strangely, the vocals seem better too. the bass is a little flabby now, but i need to work on my speaker positioning again as i think it is now too close to the rear wall and will probably resolve nicely further in the room and with the nordost back in place.

When you're moving the speakers to resolve the bass issues and balance the mids, don't just pull them so far out into the room that you lose most of the bass impact. Bass nodes will come and go every few inches that you move from the wall and corners. So, start with them back too close to the wall and move the left one out an inch or two at the time (turn the right speaker outward so that you don't hear it). Listen carefully to a recording with lots of bass and mid energy. Listen first to the bass and try to find the spot where you've got great, even bass, with no node that sticks out. Generally at that point, moving only an inch at a time, you can get the mids on equal footing and stress free and not muddied by the bass. When you've done that, do the same thing with the right speaker (it will NOT end up exactly the same distance from the wall as the left speaker.

Make sure the speakers are perfectly level across the fronts and then moving them fractions of an inch get them time aligned, so they're not fighting each other at all. Then toe them so you can see the inside edge, just barely. Final, set the rake for the biggest most balanced energy and image (usually a few degrees back).

Enjoy,

Dave

tom collins
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Re: bi-amping question

muchos gracias dave.

tom

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