Benefits of bi-amping 704

[BTB]

Hi all. I'm currently using a single Rotel RB 1070 to amplify a pair of 704's. Because my room is large, I feel I could occasionally use a few more decibels than the amp seems to be able to deliver comfortably.

Because I've only recently bought the amp, I'm not too keen to sell it, but will if it makes more sense. I'm thinking about getting a second 1070 and bi-amping. I don't intend using the "bridged" facility on the amp because of what I've read about the machines self noise in this configuration. Has anyone tried this exact combination? Should I expect significantly higher replay levels, or at least a quality improvement? Or am I better off just getting the bigger RB 1080? Just to be clear, I'm no headbanger, just in search of better quality sound at slightly higher than average levels.

I know this type of debate happens pretty often in the Rotel forum, but I had hoped to hear from B&W owners specifically. Any advise or comments would be appreciated.

[Kobus]

Bi-amping will not give will NOT give you extra dB. I bi-amp my B&W, there is a perceived difference (might be in the mind only). Most certenly not worth it if you have to purchase another amp.

You WILL be better off if you purchase a bigger amp.

Regards

Kobus

[BTB]

Hi Kobus, thanks for the reply. I see you're from Cape Town. So am I. Nice to get a reply from someone at home.

What are the percieved benefits you mention, although the rest of your answer is pretty clear. Just for interest.

[Kobus]

Bi-amping does not send more power to the speaker. The same watts goes to the highs / mids and the woofer, but because they goes seperately "they say" that you should get more headroom etc.

Now if you do this A/B comparison yourself and you only get to do it once then you quickly have to decide whether the sound has changed, not louder, but changed. Now in my opinion in my mind I wanted it to be better .........

Other people will give you other stories.

So it sounded better, .......... or did it ?

Kobus

[ShadowZA]

Hi BTB

Welcome to the forum. Totally GREAT to have another ZA member here AND you're in the mother city too.

Here's quite a good article on Bi-amping:

http://sound.westhost.com/bi-amp.htm

My opinion is the same as Kobus's. A bigger amp would certainly be better.

[BTB]

Hi Shadow ZA

Thanks, I'm feeling pretty welcome already. I must admit, I had a feeling things were going to go this way, but I was hoping I'd be able to get away with not having to go through the whole second hand sales hassle...too bad.

My wife's going to love this!!!

[LikeCoiledSteel]

Hi BTB,
I have the older model speaker to the 704, the CDM7NT, and it will really open up with the right power. Biamping is more complicated and I think you will be better off with a bigger amp. Perhaps move the 1070 to the rears for surround duty. I was using 200 watt Outlaw monoblocks and then went to a Krell 250 watt, these spaekers have nice tight bass with the right amp.
Steel

[BTB]

Hi Steel,

thanks for the info, I run a 2 channel system, so unfortunately your (otherwise) good idea to power rear speakers with the 1070 won't apply in my case. I like the sound of the Rotel and I reckon the 1080 will be the ticket, until I can afford something as nice as a Krell! This is my 4th pair of B&W's since getting hooked 3 years ago and they always seem to thrive on large doses of power despite high rated sensitivity. I suppose I should've factored that in when I was shopping around.

By the way, great pic of your dog!

[Karma]

HI BTB,
Biamping offers two main advantages. First, you can use very high quality active crossovers in front of the amps. These offer much better control of the crossover frequencies and slopes than the passive crossovers in the speakers.

Second, with a specific frequency range assigned to each amplifier there is a reduction of intermodulation (IM) distortion.

Biamping is controversial. I think this is due to the difficulty of doing it right. But when it is done right it's the best, IMO.

Sparky

[sikoniko]

well.. someone should have told abbey road they didnt need to biamp their ca-m400's then because they have their 800d's biamped..

[LikeCoiledSteel]

Hi BTB,
Thanks, his name is Dugan, aka the destroyer of speaker cables. Rotel and B&W mate well, the 1080 will work nicely. 4 sets in 3 years? That is what I call upgraditus. Better see a doctor about that, or an amp dealer...
Steel

[Kobus]

well.. someone should have told abbey road they didnt need to biamp their ca-m400's then because they have their 800d's biamped..

On a fairly unlimited budget, in the search of perfection I would also biamp.
I do biamp, but only because I have spare amps available. Bottom line is, it would always be better to go bigger than double up on a smaller amp. Unless you want to go the route of active biamping.

ps: I think active biamping is what it is called when you "undo" speaker crossovers etc.

[sikoniko]

Im sorry but I dont buy it. Lets take my amps for instance.. I have ref9's rated at 330w. According to that article, if I use 2 amps to passively biamp, I am still only effectively getting 330w total. My question would be then, what is one active and one on standby? if biwiring uses the high pass filter and the low pass filter, then why wouldn't biamping send power from each amp to each filter? effectively making it 330w to the high pass and 330w to the low pass? I understand that this is the same as having 1 660w amp biwired, but for someone who can't afford to buy 2 660w amps at one time, but can afford to buy 2 330w amps now, and six months from now add another 2, why not?

my personal conclusion is:

1 660w amp = 2 330w amps biamped

If you can afford to go the route of 1 amp, then more power to you, but for those of us who can't then I see it as a way to get there over time.

[JKalman]

Hi all. I'm currently using a single Rotel RB 1070 to amplify a pair of 704's. Because my room is large, I feel I could occasionally use a few more decibels than the amp seems to be able to deliver comfortably.

Because I've only recently bought the amp, I'm not too keen to sell it, but will if it makes more sense. I'm thinking about getting a second 1070 and bi-amping. I don't intend using the "bridged" facility on the amp because of what I've read about the machines self noise in this configuration. Has anyone tried this exact combination? Should I expect significantly higher replay levels, or at least a quality improvement? Or am I better off just getting the bigger RB 1080? Just to be clear, I'm no headbanger, just in search of better quality sound at slightly higher than average levels.

I know this type of debate happens pretty often in the Rotel forum, but I had hoped to hear from B&W owners specifically. Any advise or comments would be appreciated.

I don't think the 704 has an active crossover so bi-amping won't do anything for raising your dB ceiling before clipping. As for your other option. To get any significant change in dB you would need to raise your watts/ch much higher than is even reasonable. The change from 130 to 200 watts/ch while looking like a big number does not do much at all to raise your dB ceiling. You will actually only gain around 2 dB. This is due to the relationship of watts to dB. For a very large increase in watts you only gain a couple of dB. If you go from 200 watts to 400 watts you only gain 3 more dB and from 400 to 800, only around 3 more! As you can see, you spend a lot for little gain. To be exact, for every doubling of your power you only gain 3 dB. That is why getting a speaker with high sensitivity is useful, since it starts out louder. To double the perceived loudness you would need ten times the power! That would be a very expensive amp, and I'm sure you are starting to see why some people say that watts/ch are not nearly as important as the quality of the amp, because it is true!

You might be fine with the setup you have, considering your speakers. Going hog wild on amplifiers might not help a whole lot, so I would demo stuff with your speakers before purchasing. You might find you are limited by them.

The best thing you could do, if you absolutely feel compelled to get better sound, is to try and change companies to a better quality amplifier producer. This could help with your problem. This will improve your sound quality at least at louder volumes. Otherwise, you can only get the kind of heavy duty rise on your clipping ceiling you are seeking by getting an amp with much higher watts/ch. Moving between the two models you mentioned would be a waste of money, you won't accomplish your goal. I would move up to a company at the higher end and sell the Rotel gear. If you buy an amp that can double its load into a lower impedence, you will find it will sound better when playing loud and under heavy loads. For example, Ayre, Classe and Krell, all double their loads from (I'll use 200 as an example) 200 watts/ch to 400 watts/ch when the impedence goes from 8 ohms to 4 ohms. Like I said though, demo it with your speakers first, since they might be a limiting factor.

Here are some useful tools at least, so you can understand why what I am saying makes sense.

SPL Calculator

Some basic dB info

More Background Info (more thorough)

Another explanatory link

Hope that helps and good luck! :T