AVS Forum banner
Status
Not open for further replies.
1 - 20 of 25 Posts

·
Registered
Joined
·
1,554 Posts
Discussion Starter · #1 ·
Hello I am thinking about trying to bi-amp my B&W 9NT’s using four channels of my Rotel 1075 and my question is this, I am concerned that this might be to much power how do you figure power ratings when you are b-amping?


As far as connection I would split the preouts and run in to the RF/RS and LF/LS. Is bi-amping a good or bad idea. I am just trying to get more power to the NT’s as my amp upgrade has been put on hold for a while.


Any other thoughts on bi-amping is welcome as well
 

·
Registered
Joined
·
609 Posts
Are you currently clipping the amp at your normal listening volumes?


Your amp is rated 120wx5, your speakers recommend 50-200w, I believe.


You will gain some headroom. I wouldn't worry about over powering your speakers by doing this.


You may or may not see any difference in doing this unless you are clipping your amp currently.


When passive bi-amping always use identical amps.


Your speakers will still use the same watts bi-amped or not.


Bottom line is it won't hurt to do it. It may or may not do much for your sound though.
 

·
Registered
Joined
·
129 Posts
I use my citation 7.1 a 4 channel amp and I bi-amp my NHT 2.9's. I think it help tighten up the bottom end. Make sure you remove any jumpers on your speakers when doing this.

Allen
 

·
Registered
Joined
·
1,554 Posts
Discussion Starter · #4 ·
DrSpike yes I have a huge area and I have clipped in two channel, this isn't normal listening levels but sometimes I like to crank it up. My ultimate goal is to add a beefy 2 channel amp in the future but it keeps getting put off. I think I am at least going to play around with and hear what happens!

Thanks
 

·
Registered
Joined
·
332 Posts
I'd like to throw on a follow on question, something I've always wondered but never researched. I've always assumed that bi-amped speakers function like two speakers wired in parallel when the shorting straps are in place, so that if you remove the shorting straps on an 8 ohm speaker, in terms of your amplifier, you would then have the equivalent of two 16 ohm loads on your amps when you bi-amp. Is my assumption correct, or is there something in the wiring inside of the cabinet that I don't see that would cause the speakers to be 8 ohms either way?
 

·
Registered
Joined
·
609 Posts
JeffC, Absolutely give it a shot if you are clipping. Do remember to remove the jumpers on the speakers. :) Good luck!
 

·
Registered
Joined
·
609 Posts
jehrico76,


Just bi-amping or -bi-wiring will not take an 8 ohm and make it a 16 ohm. The rating is nominal, thus an average. Woofers tend to dip to less ohms than tweeters in given frequencies. So that wouldn't work. :) The average speaker impedance varies depending on the frequencies being played through a particular driver. Either way your average or nominal of your 8 ohm speaker is still 8 ohms.
 

·
Registered
Joined
·
410 Posts
You won't overpower your speakers. All the amps are still amplifying the full spectrum and will still clip at the same point. The x-overs are simply absorbing the part of the frequency range spectrum that's not being used by that driver.


Let's also be clear that what you're doing is *passive* bi amping. Passive bi-amping really doesn't return much in the way of results when driving efficient speakers.


Bi- amping, or active bi-amping as some call it, removes the passive x-overs entirely and makes tremendous gains in phase correction, efficiency, SPL, and detail.
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by Az Barber
You won't overpower your speakers. All the amps are still amplifying the full spectrum and will still clip at the same point. The x-overs are simply absorbing the part of the frequency range spectrum that's not being used by that driver.


Let's also be clear that what you're doing is *passive* bi amping. Passive bi-amping really doesn't return much in the way of results when driving efficient speakers.


Bi- amping, or active bi-amping as some call it, removes the passive x-overs entirely and makes tremendous gains in phase correction, efficiency, SPL, and detail.
Az,


Exactly.


If one bi-amps, i.e. "active bi-amping"; one puts a x-over ahead of the amps [ which is why

one can dispense with the passive x-over on the speaker end].


In the case of "active bi-amping", you gain a lot in headroom for the high frequency

drivers - because the high frequency amp doesn't have to contend with big swings in

the signal voltage caused by the low frequency component.
 

·
Registered
Joined
·
1,000 Posts
I'm currently doing this "passive" bi-amping on a set of Nautilus 804s. What I find is that the bass performance of the speaker is a bit more refined and extended. I'm vertically biamping with 2 Carver TFM-25s. They put out 225W a side. My feeling on the subject is this. Even without an active crossover placed before the amp, there are benefits by doing this "pseudo" bi-amping. The loading on the amp is less because one stereo amp only has to deal with the impedence dips and current demands of one set of drivers and not two. Basically you've upped your current capacity by introducing another power supply into the mix. I don't know if I'm right at all since I haven't done any type of scientific measurements. But I have heard improvements in my case. But I'm intending on adding a Bryston active crossover so I can make the next step in my setup. As far as running out of headroom, I haven't even come close. I remember the time whenI was really jamming with the system. It was summer and I had the windows open in my family room. My neighbor said he heard the Jazz CD I was playing from over a block and a half away.
 

·
Premium Member
Joined
·
2,468 Posts
Allen619:

Just curious, have tried bridging the channels on your Citation 7.1 instead of bi-amping ? Any comments on this with your 2.9's ?


Of course an alternate to bi-amping is instead of using 4 "lesser" amp channels to drive your speakers, sell it off and get a better 2-channel amp.

Same goes with speaker cables -> 1 pair of better cables may be better than 2 pairs in "lesser" cables.


... there many ways to spend your money


- Andy
 

·
Registered
Joined
·
1,554 Posts
Discussion Starter · #12 ·
Thanks for the responses AZ/Morbious thanks for the informative responses makes total sense. Andy yep agreed and the amp upgrade it is coming just not soon enough and I was hoping to get a little out of the setup without the new amp
 

·
Registered
Joined
·
332 Posts
Quote:
Originally posted by WonHung

My neighbor said he heard the Jazz CD I was playing from over a block and a half away. [/b]
He wasn't too upset with you, was he?:rolleyes:
 

·
Registered
Joined
·
129 Posts
Quote:
Allen619:

Just curious, have tried bridging the channels on your Citation 7.1 instead of bi-amping ? Any comments on this with your 2.9's ?
I ran the the amp in bridge mode for a while. Then I heard some speakers at a audio store and the bass in them was really tight then the guy told me that they were only a 1000.00 a pair I couldn't believe it. We talked about how good the bass sounded on them and he said by removing the cheap metal strips and running a second set of wires would help the bass and it did help. So later on I just wanted to try to bi-amp the speakers and I thought it helped a little more so I left it like that. I do have my svs 16-46 sub running off of a citation 5.1 in bridge mode with no problems.


Allen
 

·
Registered
Joined
·
1,000 Posts
Quote:
He wasn't too upset with you, was he?
Nope. Actually he was a bit jealous. :D
 

·
Registered
Joined
·
78 Posts
Morbius -


Could you please explain in detail - active bi-amping? What do you mean by "put a x-over before the amp"?


I am planning on buying a two channel amp for each speaker and running one channel to the upper terminals and one to the lower. Is this bi-amping or do I have to have two monoblocks?


Thanks,


Paul
 

·
Registered
Joined
·
3,947 Posts
This is bi-amping. That the two amps share a chassis and power supply doesn't change anything.


Still, there needs to be something that steers the highs to the tweeter and the lows to the woofer. If you simply Y-cord the amp inputs, the speakers' crossovers will take care of this as usual.


The better way to bi-amp is to use an active (electronic) crossover ahead of the amp inputs, so each channel doesn't even see frequencies outside of the range it's being asked to amplify.


The one thing that is necessary to do when actively bi-amping is to bypass the speakers' crossover components, so each amp channel is wired directly to its driver terminals, which usually voids the warranty.
 

·
Registered
Joined
·
332 Posts
Quote:
Originally posted by Larry Fine
This is bi-amping. That the two amps share a chassis and power supply doesn't change anything.


Still, there needs to be something that steers the highs to the tweeter and the lows to the woofer. If you simply Y-cord the amp inputs, the speakers' crossovers will take care of this as usual.


The better way to bi-amp is to use an active (electronic) crossover ahead of the amp inputs, so each channel doesn't even see frequencies outside of the range it's being asked to amplify.


The one thing that is necessary to do when actively bi-amping is to bypass the speakers' crossover components, so each amp channel is wired directly to its driver terminals, which usually voids the warranty.
Why would it be necessary to bypass the speakers crossover? I don't believe that is accurate. The crossover filters out out-of-range frequencies for each output on it. If those frequencies have already been filtered out by the crossover before the amp (and, assuming that the crossover is set the same as the internal xover on the speaker), then the correct freq's simply pass through the crossover to the drivers. No need to bypass it. The only reason to bypass it is if you feel that the xover freqs that the speaker natively uses are wrong, and you want to control that yourself. Also, considering the fact that most bi-ampable speakers are three way (or more), then you definitely still need the internal crossover between the midrange and the tweeter. Bypassing the crossover is not necessary for active bi-amping.


Now, you could add the argument that in the event that the xover before the amp is set exactly the same as the xover in the speaker between the woofer and the midrange, then it's an unnecessary component that is in the system, thus unnecessarily affecting sound quality, and that you'd be better off bypassing it. But that still doesn't make it necessary to remove the xovers to bi-amp the speakers.
 

·
Registered
Joined
·
20 Posts
I've experimented with passive bi-amping my Totem Arro's with 4 channels of my NAD 762 reciever. For me the change was pretty subtle with a bit tighter low end. I found that a bigger change was gained from by-passing the cheap binding straps on the speaker terminals. I'm currently bi-wiring since I had the cable from my bi-amping experiments but I assume a speaker wire bridge between terminals would work as well.


From my experience's in car audio, active bi-amping displays much more benefit then passive bi-amping as stated by others above.
 

·
Registered
Joined
·
3,947 Posts
Jehr, there are other factors that are involved. First, what you addressed directly: The redundant crossovers in the speaker aren't transparent even when the frequencies fed into them happen to match.


The slopes will combine, so, for example, a speaker crossover with a 12 db/octave slope and an electronic crossover with an 18 db/octave slope will combine and create 30 db/octave slopes, or maybe something wierd.


More important (at least to me), crossovers work both ways, meaning that an amplifier's damping factor can't control driver motion outside the passband of the crossover section, and especially around the crossover region.


Direct amplifier-to-speaker connections provide the best, lowest-impedance connection which makes for the cleanest, best-controlled sound, and best energy transfer; no voltage is dropped across inductors, capacitors, and/or resistors.


This is, of course, just my opinon. Afdmittedly, I havent removed the crossovers from my signal chain yet, and I may one day, when I get a round tuit. We're talking idealistic theory here.
 
1 - 20 of 25 Posts
Status
Not open for further replies.
Top