Bi-Amping 3 channels ? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 27 Old 09-17-14, 07:04 PM Thread Starter
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Bi-Amping 3 channels ?

Good evening gentlemen,

Looming for an amp to provide an additional 30-50 watts to my left, center, and right channels. Want to utilize the HF & LF terminals on each of the speakers. Heard some talk of it making zero difference, but why would the company design them like that? For looks? Has to sound better or operate more efficiently for a company to add thextra additional cost to manufacturing

Noticed an Emotiva amp I've never seen called the stereo flex that delivers
100 x 2. Is the only way to bi-amp them a 5 channel?

Appreciate any assistance or recommendations
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post #2 of 27 Old 09-17-14, 07:19 PM
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Re: Bi-Amping 3 channels ?

Quote:
TomFord wrote: View Post
Looming for an amp to provide an additional 30-50 watts to my left, center, and right channels. Want to utilize the HF & LF terminals on each of the speakers. Heard some talk of it making zero difference, but why would the company design them like that? For looks? Has to sound better or operate more efficiently for a company to add thextra additional cost to manufacturing
Adding an additional 30-50 watts isn't going to make any audible difference unless you're at 30-50 watts. Double the watts adds 3dB of volume. Passive Bi-amping and Bi-wiring does nothing except make cable manufacturers more money. Yeah sure it adds to the cost of manufacturing but probably not by much and they probably pass it along to the consumer. Speaker companies make speakers that way so they don't alienate people who believe in passive bi-amping and bi-wiring. It makes sense for a manufacturer to add the bi-wiring because it entices the people who believe in it and the people who know bi-wiring does nothing just ignore the "feature". This link explains why passive bi-amping and bi-wiring does nothing:
http://www.chuckhawks.com/bi-wire_bi-amp.htm

Active bi-amping is another story altogether however...
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post #3 of 27 Old 09-17-14, 07:31 PM
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Re: Bi-Amping 3 channels ?

First the cost is minimal. Isolating the woofer crossover in most cases involves eliminating one circuit trace. Then add in an extra set of terminals or solder points on the crossover board, an extra set of binding posts, jumpers and some wire.

Got to agree on the Active vs. Passive bi-amping. You may hear some difference with passive bi-amping but to hear it both you and your system would have to be especially capable.

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post #4 of 27 Old 09-17-14, 08:27 PM Thread Starter
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Re: Bi-Amping 3 channels ?

Thanks. I'm now looking at the Emotiva 5 & 7 channel amps. By active bi-amping you mean where I'd be able to adjust certain aspects opposed to strictly sending power correct?
I've never used a power amplifier (almost 3 months with Home Theater experience) with the quality of a Emotiva. Understand the circuitry well, it's just been a decade since I became a certified electronic technician due to having only 2 classes Sr year & Vo-Tech being free so I thought it'd be very beneficial with the cpu boom going on at the time.
We mainly learned of the internal parts you see on a board. The designs Emotiva uses (I'm sure many others at the price range as well, but don't see them showing internals) are amazing to be at the prices they offer. Particularly the UPA 500 & 700. Do these allow the adjustments to be active? Was reading on their site & it wasn't very clear on what you're able to adjust. Or would I need a separate EQ for it to be active bi-amping?

Trying to have all of speakers at their peak performance/efficiency (KEF rep said they operate best at 10-30 watts over the recommended 150 speaking in terms of least likely to any damage) before the KEF R50 ships & I install the 2 ceiling speakers unsure of the models, when the Dolby Atmos firmware update comes on 9/28.

Important question I haven't asked. My Onkyo TX-NR838 is 7.2 channel yet is able to play the zone 2 from the same source as other 7 channels unlike the lower models. I will have to get rid of my front height speakers which is what the KEF R50's will run on, do i use the surround back for the 2 ceiling speakers? Know I have to use the heights for one, yet unsure of the others.
Wish I was able to add an additional AVR to this one

As always, truly appreciate any assistance or advice fellas
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post #5 of 27 Old 09-17-14, 09:21 PM
 
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Re: Bi-Amping 3 channels ?

An example of Active Bi-Amping would be this...

1: Disconnect the current crossovers
2: Get a MiniDSP for a crossover (a 2x4 can do 2 channels Bi-Amped) There are other options but the MiniDSPs are inexpensive and do the job
3: Hook up to 2 channels of amplification for each speaker preferably with individual volume control
4: Hook up your wires to the amps, and then configure the crossovers
5: Tune your setup

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post #6 of 27 Old 09-17-14, 09:25 PM
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Re: Bi-Amping 3 channels ?

In active bi-amping the crossover is "active" (read powered) and comes before the power stage. The passive crossovers in the speakers are removed or didn't exist in the first place. By isolating the frequency spectrum for each speaker prior to power amplification the amps are only fed those frequencies.

Before I dropped serious coin I'd take the time to get the most of the system as is. Separate PAs aren't a bad idea especially for the fronts, but I like baby steps not giant leaps. You'll appreciate the journey more IMO.

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post #7 of 27 Old 09-17-14, 09:39 PM
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Re: Bi-Amping 3 channels ?

Boy, walk away for a minute and ... ninja'd

MiniDSP is an affordable option I had over looked. But setting up crossovers isn't exactly plug-n-play. You'll need to do full range sweeps on individual drivers to get the data you'll need to find optimal cross point(s). Can you recognize cone break-up on a sweep trace? Then which profile to chose; Butterworth, Linkwitz-Riley, Bessel of what order? What about time alignment? Phase issues? Baffle stop loss management?

Not trying to dissuade just full disclosure.

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post #8 of 27 Old 09-18-14, 12:24 AM
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Re: Bi-Amping 3 channels ?

Going active isn't for everyone. It has extra setup steps and if you don't get them right you might fry a tweeter if you do the DIY building of your own or converting an existing pair. There aren't many consumer active speaker setups outside studio monitors.

The benefits are the amps are more efficient since they only have to amplify a narrower bandwidth along with less amp power lost to heat dissipation from the passive Xover, the amps have direct control of the driver (better damping factor), and the woofers no longer influence the tweeters (in a passive setup if the woofer starts to distort it forces the tweeter to distort even if it normally wouldn't at that level). There's also the convenience of being able to tweak drivers in real time.

To me active speakers feel a bit more dynamic and more alive than passive.

Once the warranty is up on my MartinLogan EM ESL's I plan to convert them to active.
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post #9 of 27 Old 09-18-14, 02:57 PM Thread Starter
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Re: Bi-Amping 3 channels ?

Trying to address multiple posts. Also, this is something I would need to do a lot of research on before attempting & wouldn't do so on one of the KEF's intially.
In order for let's use one speaker in this example the KEF Q700. It has 2 6.5 ABR woofers, 1 6.5 LF woofer, 1 6.5 Uni-Q with a 1 inch tweeter. Currently it's internal crossover is at 2.5kHZ. I would need to determine the ranges on the tweeter, Uni-Q, LF, & ABR woofers. Here's where I'm a bit confused, remove the crossover inside the tower & wire them so that each (in this case the 2 ABR acting as one) speaker is receiving it's own amplification? Having the watts being supplied only to the frequency range of each speaker? For example on the LF woofer (rough estimate) sending only 20 Hz - 200 Hz. Am I on the right path?

Don't believe this would be the case yet you don't mean me doing the math & soldering the capacitor & coil combination that creates the proper crossover for each correct?

I'm going to look into & learn more of the DSP & how they operate. If you know any source material that'd be beneficial I'd appreciate the recommendation as I'm clearly confused never having heard of this. See what I can learn
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post #10 of 27 Old 09-18-14, 04:19 PM
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Re: Bi-Amping 3 channels ?

If you'll note the Q700's are a 2.5 way design which means they are using one of the drivers for baffle stop compensation. 2.5 may be descriptive of the function but in application there are three distinct seperate driver freq bands being developed. The 2.5kHz xover listed isolates the upper freqs for their "Uni-Q" driver while everything lower going to to the rest. If it truly is a 2.5 one of those is crossed lower to accommodate the baffle stop loss that comes from having a narrow face on the front of the speaker cabinet. It's physics and you can't avoid it. The big red flag for me would be that they don't give you any info on the crossover except that is low order. That second cross has to be lower in freq to get back the low end lost to the 8.3" wide baffle without bloating the mid-low end above the baffle stop. In any event if you go active their xover has to go and you'll need 3 amplifier stages per speaker not just 2.

Good luck. Don't throw the KEF xovers. I'm betting you'll put them back in.

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