# Biamping B&W 603s



## Hakka (Sep 10, 2006)

I have a pair of B&W603 series 1 main speakers. I have been interested in biamping these for a while.
The 603s have a tweeter, a powered mid/bass and a passive bass driver. They have 2 sets of binding posts on the back of them. 

I have looked at the 603 series 3 specs and it lists 2 crossover frequencies 150hz and 4khz, the bass driver is obviously powered in the later models. The manual for the 603 series 1 lists only 3khz. So if I were to biamp I would have one channel powering the tweeters and another channel powering the mid. From what i have read the normal setup is to have one channel on the tweeter/mid and the other on the bass.

Would I gain anything by biamping these speakers?? How would I go about balancing the power levels between the mid and the tweeter? Is it even safe to connect a 130w amp to a tweeter?

(amps are rotel RB-1070 and RMB 1075).


Thanks.

Harry.


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## Otto (May 18, 2006)

Hi Harry,



Hakka said:


> The manual for the 603 series 1 lists only 3khz. So if I were to biamp I would have one channel powering the tweeters and another channel powering the mid. From what i have read the normal setup is to have one channel on the tweeter/mid and the other on the bass.


Well, it depends on your particular speaker. Since yours is a two-way system, you'll power each with one amp. I'd consider the kevlar driver in the 603 s1 as a mid/bass driver. Some 2.5 way systems will power mid/tweet together and bass separately, as you note, and some will allow you to tri-amp 2.5 and 3-way systems.



> Would I gain anything by biamping these speakers?? How would I go about balancing the power levels between the mid and the tweeter? Is it even safe to connect a 130w amp to a tweeter?
> 
> (amps are rotel RB-1070 and RMB 1075).


I'm not sure how much improvement you will get. I guess it depends on your goal. What's your mix of music and movies? You might realize a little more detail or control with biamping, but I think this will show up more in critical listening and less in movies. You should theoretically be straining each amp less, so distortion and such should be held lower. 

To match levels, it would probably be best gain controls on your amps. Some people use identical amps and then don't have to worry about level-matching. It looks like your 1070 amp is 130 WPC and your 1075 is 130 WPC. These are "pretty close." If there is no gain control on either (well, I would guess it to be more important on the 1070), you can still give it a try. Try the 1070 to the mid/bass and the 1075 to the tweeter. Then swap and see how you like that. If you find you like it, but that you need to level match, I'm sure there are little passive devices out there that will knock one of the levels down a bit.

Yes, it is safe to connect a 130 W amp to the tweeter; it's designed for it.

Good luck and have fun!


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## JCD (Apr 20, 2006)

Based upon nothing but hearsay, I'm not a big believer in bi-amping speakers UNLESS you have an active crossover. There are some that are big proponents, but I just haven't heard it yet.

Of course, with my tinfoil ears.. :hush: 

JCD


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## Hakka (Sep 10, 2006)

Otto said:


> Hi Harry,
> 
> I'm not sure how much improvement you will get. I guess it depends on your goal. What's your mix of music and movies? You might realize a little more detail or control with biamping, but I think this will show up more in critical listening and less in movies. You should theoretically be straining each amp less, so distortion and such should be held lower.


I'm probably 70/30 HT/music. I dont have any goals, just keen to try it.



Otto said:


> Hi Harry,
> 
> To match levels, it would probably be best gain controls on your amps. Some people use identical amps and then don't have to worry about level-matching. It looks like your 1070 amp is 130 WPC and your 1075 is 130 WPC. These are "pretty close." If there is no gain control on either (well, I would guess it to be more important on the 1070), you can still give it a try. Try the 1070 to the mid/bass and the 1075 to the tweeter. Then swap and see how you like that. If you find you like it, but that you need to level match, I'm sure there are little passive devices out there that will knock one of the levels down a bit.


My Rotels dont have any gain controls, they are power amps connected to a Denon 3803 receiver. 
I would have thought that the sensitivities of the two drivers would be pretty different to each other.
I was gonna try it using 4 channels of the 1075 to biamp the mains, if I like the results I will add another RB1070 and use 2 of those.


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## Kerbango (Jun 22, 2006)

I bi-amp my Paradigm Monitor 11s with a 4-channel dbx BX-2 power amp. I used Y-adapters to take the two Front pre-outs from the receiver to the four inputs of the power amp. The outputs on the power amp are fixed so I don't have to worry about levels. The speakers have two sets of binding posts. I removed the shorting bars and connected the speaker wires. I then used the built-in YPAO and external mic to set levels for Front, Center, Surround, etc... Of course you could also use Avia or another DVD and an SPL Meter. 

I noticed an improvement immediately. Here is my theory why there was a dramatic difference.

My AVR is a Yamaha RX-V2500 which is rated at 130 WPC RMS 20-20 kHz into 8 ohms. The dbx has four independent amps rated at 90 WPC RMS 20-20 kHz into 8 ohms - ALL CHANNELS DRIVEN! 

The Yamaha has been tested independently. The result is more like 70 WPC with all channels driven. So I went from 70 Watts potentially feeding the Left and Right to 90 Watts feeding the Left and Right tweeter and 90 Watts feeding the Left and Right mid/bass. Would a 2-channel 180 WPC power amp achieved the same results? Probably. 

Similar tests on Denon receivers achieved somewhat better results, but still nowhere near the stated wattage when all channels are driven.

So, if you have the amps available, by all means bi-amp. If I didn't have the dbx power amp laying around I would have never even tried this.

BTW I tried bi-wiring and found no discernable improvement.

Hope this helps!

Chuck


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