Bi-Amping with a twist - AVS Forum
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post #1 of 17 Old 08-11-2014, 05:13 PM - Thread Starter
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Bi-Amping with a twist

I am wondering what type of benefit if any bi-amping will give me. When I talked to the QSC rep. he highly recommended it for various reasons. Here is some background. The speakers I own are QSC 2150 I'll post some specs later. They have an option when wiring your speakers to select either Passive or Bi-amp. Apparently the internal crossover takes over from there. I am wondering what difference I would hear if I ran a Crown XLS 1500 in bridge passive (1050 W @ 8 ohm, 1550W @ 4 ohm). Does the crossover automatically run both my HF, & LF at 8 ohms or 4 ohms. As you can see from the specs below each operates at a different level.

Here is a link to the 2150 specs, it did not appear as I formatted it. http://qsc.com/products/Loudspeakers...eries/SC-2150/


Second question: Let's assume bi-amping would be beneficial. I'm not even sure how to do it. Is this correct? Would I wire one 4 pole Speakon cable with the +1 and -1 and use that for my HF and connect to output channel 1. Then wire my second 4 pole speakon cable with the +2 and -2 for my LF and connect that to output channel 2. Then wire them to my speakers bi-amp connections? If this is correct do I need a Y cable to connect both RCA ch 1 &2 outputs into the back of my AVR single input? And of course enter my amps setup and change to bi-amp mode.
This would be a much cheaper option and take up less space than buying 3 more Crown XLS amps and running them bridged. ie 6 separate amps. I was also considering the X1000 for $99.00 If I could bi-amp like above that would be awesome. I could buy 3 instead of 6.

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post #2 of 17 Old 08-11-2014, 07:29 PM
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Unless those speakers have an active crossover, biwiring will be of no benefit ( except to the person who sells wire)!
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post #3 of 17 Old 08-11-2014, 07:55 PM - Thread Starter
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Not bi-wiring, Bi-Amping. The wire is free, I have 200 feet. lol Im curious if I which benefit is greater. Leaving my Crown XLS 1500 bridged and sending 1050 watts directly to 1 speakers or "BI- AMP" the speakers and send 300 watts to the HF and sending 525watts to the LF. According to the specs that should be sufficient. IF it is just bridged how is it distributing the power through the crossover. How much wattage and what OHM to my LF and HF ?

According to the description they DO have an active crossover, otherwise the specs wouldn't change?

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post #4 of 17 Old 08-11-2014, 10:01 PM - Thread Starter
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Just in case I did want to test the bi-amp mode. Is the wiring solution in the 1st post correct? As far as the second question goes. I guess I see your point about bi-wiring vs bi- amping they are basically the same. But since the speaker specs changed I thought it was a different solution than bi wiring. Still a noob.

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post #5 of 17 Old 08-12-2014, 10:20 AM
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They are exactly the same. The confusion comes from a misunderstanding of the difference between active and passive biamplification. You are talkina about passive biamplification which is of no value and you don't really want to get into active biamplification without knowing what you are doing.

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post #6 of 17 Old 08-12-2014, 12:09 PM - Thread Starter
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Quote:
Originally Posted by FMW View Post
They are exactly the same. The confusion comes from a misunderstanding of the difference between active and passive biamplification. You are talkina about passive biamplification which is of no value and you don't really want to get into active biamplification without knowing what you are doing.

Fred
What do you mean by "its of NO value" The speakers are made to run either "passive" or "bi-amp" via an external switch. According to QSC website specs the bi-amp mode "does" change the characteristics of the HF and LF driver. (I understand about 50%). If I enter the Crown XLS amp setup, it will allow changes to the HF and LF frequencies to allow the Crown as an external crossover. What I am basically asking is "will I hear a difference" It is justified to bi-amp? will it provide more headroom to my LF drivers?
What is the difference if I run my crown in passive bridge mode 1050 watts per speaker. v.s bi-amp 525 watts to LF and 300 to HF vs Denon 4311CI 150 watts per speaker? Can you explain the pro's and con's to each setup?

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post #7 of 17 Old 08-12-2014, 02:38 PM
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Quote:
Originally Posted by rlhaudio View Post
What do you mean by "its of NO value" The speakers are made to run either "passive" or "bi-amp" via an external switch. According to QSC website specs the bi-amp mode "does" change the characteristics of the HF and LF driver. (I understand about 50%). If I enter the Crown XLS amp setup, it will allow changes to the HF and LF frequencies to allow the Crown as an external crossover. What I am basically asking is "will I hear a difference" It is justified to bi-amp? will it provide more headroom to my LF drivers?
What is the difference if I run my crown in passive bridge mode 1050 watts per speaker. v.s bi-amp 525 watts to LF and 300 to HF vs Denon 4311CI 150 watts per speaker? Can you explain the pro's and con's to each setup?
This has been discussed endlessly but I\ll spend a few words. The biamplification they are talking about is called active biamplification. It involves putting an active crossover between the mixer and the amplifier. That provides total isolation between the drivers and an adjustable crossover point. You do not use the passive crossover in the speakers.

Passive biamplification doesn't have any meaningful effect on sound or power delivery. I don't have the energy to explain why for the umpteenth time. I'll let you search the forum and read it for yourself.

You may want to look into the negatives of amplifier bridging as well since you will only be using about 20 watts per channel anyway. That and active biamplification are pro audio techniques not intended for home use. Best of luck to you.
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post #8 of 17 Old 08-12-2014, 03:11 PM - Thread Starter
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NM. Its all good.

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post #9 of 17 Old 08-12-2014, 05:29 PM
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To me, when you bi-wire all you are doing is moving the jumper from the speaker posts to the amp/receiver posts and adding the additional wire to the xover.
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post #10 of 17 Old 08-12-2014, 06:37 PM
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Originally Posted by kjfalls View Post
To me, when you bi-wire all you are doing is moving the jumper from the speaker posts to the amp/receiver posts and adding the additional wire to the xover.
That's exactly what it does, and electrically it gives exactly the same result both ways.

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post #11 of 17 Old 08-12-2014, 06:42 PM - Thread Starter
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but im not bi-wiring, I am bi-amping. The speakers I am using are Professional Cinema Theater Speakers not your average best buy speaker with 4 binding posts.
http://qsc.com/products/Loudspeakers...eries/SC-2150/ Then click on the specifications tab. As you can see the LF and HF are different when bi-amping.

As you can see via the specs the LF and HF use different OHM's as well as a different crossover frequency. This is not just bi-wiring to the internal crossover rather bypassing and using an external crossover (crown xls 1500). Im just curious "IF" I would hear a noticeable difference or if leaving the crown amp in bridged mono mode will give the same result.

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post #12 of 17 Old 08-12-2014, 06:51 PM
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Quote:
Originally Posted by rlhaudio View Post
Im just curious "IF" I would hear a noticeable difference or if leaving the crown amp in bridged mono mode will give the same result.
If you're actually using an electronic crossover and there will be no passives in place then you will get lower THD and IMD. If this is going to be a stereo setup you will need four channels of amplification.

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post #13 of 17 Old 08-12-2014, 09:28 PM - Thread Starter
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so really NO good reason to bi-amp. Will using the crowns in bridge mode provide any positive results? OR should I just let the Denon 4311CI handle all 9 channels by itself. The manual does say each channel is 140 wpc discrete. When I bridge my Inuke 100dsp I do notice significant spl (much louder) I have been playing with the options. Im not looking for louder im looking for clarity and deep hard bass from the dual 15's. as well as articulate vocals. The other reason I have been asking so vigilantly is because the new Crown X1000 bridged is 600 watts. Not a huge change but significant from 140 watts via the Denon and you cant be the price of $99 per crown.

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post #14 of 17 Old 08-13-2014, 05:09 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
If you're actually using an electronic crossover and there will be no passives in place then you will get lower THD and IMD. If this is going to be a stereo setup you will need four channels of amplification.
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so really NO good reason to bi-amp.
That's not what he said!

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post #15 of 17 Old 08-13-2014, 07:41 AM
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in active mode those speakers need you to supply the active crossovers ahead of the power amps. They give the specs for the crossovers you should use. Without outboard filters, you'd be sending full range (full bass) signals to the mids, and easily could damage them. And of course they'd sound weird without the appropriate crossovers dividing the signal between woofer and the mid/high unit.

It's not active biamping unless the crossover filters are in front of the INput to the amplifiers . . .
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post #16 of 17 Old 08-13-2014, 10:13 AM
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He knows all that. Read what he wrote:
Quote:
Originally Posted by rlhaudio View Post
This is not just bi-wiring to the internal crossover rather bypassing and using an external crossover (crown xls 1500).

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post #17 of 17 Old 08-13-2014, 10:58 AM - Thread Starter
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I connected my speakers bi-amped and didn't really care for the sound. I was using an Inuke 1000dsp so I could change the fields as I went. I did hear some differences here and there but nothing earth shattering and certainly NOT worth the headache of nearly blowing a speaker. SO, new question... sorta. Would connecting my speakers in bridged mode be more beneficial than using my Denon AVR? I will be running an 11ch setup (not 100% sold on Atmos) but if I were, it would be an 11 ch Atmos player as well.

SO, will I hear a difference if I bridge my speakers? will 600 wpc sound any different than 140wpc? I am not looking for higher SPL, im asking about more clarity and detail with vocals, instruments, sounds, explosions, etc. I already know it will play louder than I would ever want.

Does it really all come down to the speakers sensitivity? ie. if your speakers are 100db sensitivity connecting a 500wpc Krell amp will sound the same as a 600 watt bridged crown and a 140wpc Denon. due to the 100db sensitivity.

Secondly if your speakers are 90db sensitivity and you connect the same 3 amps then you WILL hear a very noticeable difference with clarity, soundstage, vocals, etc and the Krell would be the clear winner?

I ask this question because I owned a pair of B&W 802D speakers and when powered with a standard AVR they sounded like crap, but when I connected them with a McIntosh 200wpc amp they really opened up and sounded incredible. completely different speakers. I guess this is the point/question I am trying to understand. Perhaps with pro speakers it will make no difference due to the type of atmosphere they are played in.
**If I had connected a Crown amp and ran that in stereo, ie 500wpc @8 ohm would the B&W 802D sounded as good as the McIntosh?

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