Amp for B&W 804D

[BWguy]

I am currently running my 5 channel system with B&W 804D in the front and 683's in the rear. I am powering them with a Rotel 1095 amp, which has 200 watts per channel. Even though the maximum recommended power for the 804's are 200 watts, would I be better served to add a 2 channel amp, say 300 watts, when I listen to 2 channel music? I would keep the rears powered with the Rotel. I know B&W needs a lot of power.

 

[jinjuku]

You should be fine with the Rotel you have. I have some 2 way speakers I built for my Wifes office with a 20 WPC T-AMP and you can't stay in the room with them cranking. You B&W's are most likely a lot more efficient than the ones I built.

 

[AcuDefTechGuy]

I would use only the Rotel 1095 amp as well. That looks like one high quality amp that can drive even the 800D2 to greatness.

I'm assuming you listen to sensible volume like many of us from no more than 12FT distance.

 

[BWguy]

I sit about 12 to 13 feet away. I do like to crank it pretty loud at times.

 

[AcuDefTechGuy]

I sit about 12 to 13 feet away. I do like to crank it pretty loud at times.

How loud is "pretty loud"?

4m distance, 90dB/2.83v/m, SPL 100dB from 2 speakers (2.0 mode, no subwoofers) would require 80W into 8 ohms or 160W into 4 ohms.

In 2.0 direct mode (2 speakers, no subwoofers) the loudest I've listened was ~94dB Peak from ~13FT away. So in my case, it would only require 20W into 8 ohm or 40W into 4 ohms.

 

[BWguy]

Thanks for the reply. "Pretty loud" is anywhere from -12 to -5 on the volume setting. Sorry, I am not that well versed on the technical aspects.

 

[walter duque]

Thanks for the reply. "Pretty loud" is anywhere from -12 to -5 on the volume setting. Sorry, I am not that well versed on the technical aspects.

I don't know if your processor has a volume limit setting (mine does). I would find a save zone that you are comfortable with at loud volume, you kind of get the feeling at one point where you might think something is gonna blow, so set it to that setting or just don't go above -5. You got a good amp and 200 watts is not bad at all. But than again not all material can be played at that zone either. Primus for instance I have to play at a much lower setting because something will go, it's just a loud recording to start with.

 

[PENG]

I am currently running my 5 channel system with B&W 804D in the front and 683's in the rear. I am powering them with a Rotel 1095 amp, which has 200 watts per channel. Even though the maximum recommended power for the 804's are 200 watts, would I be better served to add a 2 channel amp, say 300 watts, when I listen to 2 channel music? I would keep the rears powered with the Rotel. I know B&W needs a lot of power.

B&W specs say 50-200W. Give them 500W each and they will sound better to you.

 

[walter duque]

B&W specs say 50-200W. Give them 500W each and they will sound better to you.

That's what I had in mind, but I don't always want to go overboard. I am just a power freak. To me entry level is 200 watts. I would go between 350+500 watts for those speakers and run the rears with the Rotel. And yes you will hear a difference and you'll get the most out of your investment.

 

[crossedover]

Other than 3 ohm nominal and that lying just above 100hz, the phase angle is not difficult so stick with your current amp for either 2 or 5 channel. If you want to placebo the difference get a crown pro amp and have a Blast

 

[BWguy]

How about the emotiva XPA-2? I believe that would get me 300 wpc for the mains.

 

[AcuDefTechGuy]

How about the emotiva XPA-2? I believe that would get me 300 wpc for the mains.

Well, first, if the speaker does not require that much power, using a more powerful amp doesn't give you any cleaner power.

2nd, if the speaker does require 300W because the volume is 115dB, the 300W will probably blow the diamond tweeters. Diamond tweeters are quite fragile.

 

[AcuDefTechGuy]

Other than 3 ohm nominal and that lying just above 100hz, the phase angle is not difficult so stick with your current amp for either 2 or 5 channel. If you want to placebo the difference get a crown pro amp and have a Blast

Nominal impedance is 8 ohms (800Hz-10kHz). Minimum impedance is 3 ohms around 100Hz. From 700Hz-11kHz, it's above 4 ohms. Doesn't look very difficult to drive.

 

[canelli]

Nominal impedance is 8 ohms (800Hz-10kHz). Minimum impedance is 3 ohms around 100Hz. From 700Hz-11kHz, it's above 4 ohms. Doesn't look very difficult to drive.

I have considered B&W speakers fairly hard to drive due to the amount of phase shifting that occurs around the impedance of 3 to 4 ohms. This occurs at lower frequencies (higher amplitudes) which I understand makes the matter worse. This effect reduces power delivered to the speaker and increases the transistor power dissipation.

For some ICE amplifiers, I have heard audible distortion while driving B&W speakers at moderate levels.

Hopefully someone with a much deeper understanding can comment.

 

[AcuDefTechGuy]

I have considered B&W speakers fairly hard to drive due to the amount of phase shifting that occurs around the impedance of 3 to 4 ohms. This occurs at lower frequencies (higher amplitudes) which I understand makes the matter worse. This effect reduces power delivered to the speaker and increases the transistor power dissipation.

For some ICE amplifiers, I have heard audible distortion while driving B&W speakers at moderate levels.

Hopefully someone with a much deeper understanding can comment.

I suppose it depends on the SPL, distance, type of music (bass heavy), and surround mode (2.0 vs 2.1).

But the 802D2 didn't seem difficult to drive at all with just a Denon AVR-3312 (in 2.0 direct mode) when I owned the 802D2.

On one occasion the B&W dealer used a NAD 160WPC x 7Ch amp to drive the B&W 800D2 (2.0 direct mode) without any kind of issues.

 

[Swerd]

I have considered B&W speakers fairly hard to drive due to the amount of phase shifting that occurs around the impedance of 3 to 4 ohms. This occurs at lower frequencies (higher amplitudes) which I understand makes the matter worse. This effect reduces power delivered to the speaker and increases the transistor power dissipation.

Stereophile did a review of these speakers, with their usual assortment of measurements and graphs. Here is their impedance curve:

The reviewer said this about power:

My estimate of the 804 Diamond's voltage sensitivity was 89.3dB(B)/2.83V/m. While this is slightly lower than the specified 90dB, it is still usefully higher than average. The plot of the 804 Diamond's impedance magnitude and phase against frequency is shown in fig.1. The speaker is a moderately difficult load for the partnering amplifier to drive. Not only does its impedance reach a minimum value of 3 ohms at 108Hz, there is a combination of 4.5 ohms and a 53° capacitive phase angle at 72Hz, and the impedance remains below 4 ohms for much of the midrange and the top octave.

For a "moderately difficult load" I think a 200 wpc amp would be sufficient, as long as the amp is stable below 4 ohms.

Remember that doubling the power to 400 wpc will produce a barely noticeable difference. To make a truly audible difference, a 10-fold increase in power would be needed. How many 2,000 wpc amps are there, and at what price? Even if you lower the bar to the square root of a 10-fold increase, about 3-fold, you have to ask how many affordable 600 wpc amps are there?

For the available info on the 804D, 200 wpc is fine. (Unless you're Walter .)

 

[canelli]

I think a 200 wpc amp would be sufficient, as long as the amp is stable below 4 ohms.

When referring to the B&W speakers as difficult I was not inferring to the amount of wattage. Even today some amplifiers do not handle certain loads very well. Throwing more wattage at the issue doesn't fix the real problem.

Also, saying Brand X amplifier sounded just fine at some wattage does not imply that Brand Y will do the same.

The ICE amplifier I used with B&W speakers claimed stable down to 4 ohms. I could hear the distortion during explosions / loud volumes and was amazed that no other review site or reviewer mentioned this potential problem. Only after purchasing a Parasound amp did I find this review:

Driving 4-ohm loads was an entirely different story. The SC-07 simply fell apart when running full bandwidth (20Hz to 20kHz) continuous power measurements. As I tested at frequencies above 5kHz with only 1 channel driven, the internal cooling fan would instantly come on right before the receiver would go into gross distortion and shut down at levels above 100 watts.

Pioneer SC-07 Measurements and Analysis | Audioholics


This is not the only amplifier reviewed here that had issues with complex loads.

We feel like we finally got to the bottom of the issue: It wasn’t due to a faulty amp or the speakers being wired out of phase. Rather, Gene, Paul, Ryan, and I all concluded that the audible problems had to do with the ability of the M1000ASP B&O ICEpower modules to handle the load that the Salon2s presented at those more difficult to handle frequencies that the Salon2s had shown in their measurements. Gene also reminded me that some ICEpower modules we've previously measured at Audiohoics struggled with speakers that dipped into 4 ohms at higher frequencies.

Red Dragon M1000 MkII and M500 MkII Setup | Audioholics

 

[canelli]

My only point to my previous posts is that I ended up spending a lot of money to fix an issue caused by the amplifier section of a receiver. If I had been able to figure out the problem at first, I would have returned the damn thing and gotten something else and saved a ton of money.

 

[PENG]

My only point to my previous posts is that I ended up spending a lot of money to fix an issue caused by the amplifier section of a receiver. If I had been able to figure out the problem at first, I would have returned the damn thing and gotten something else and saved a ton of money.

You are talking about ICE amp that is very different and is relatively new. B&W recommends 20 to 200W. Surely one can match it to a 500W (I mean a real 500W average, 20-20,000 Hz, <0.1% THD+N into 8 ohm class AB/AAB amp safely if used sensibly and as I said it would improve the sound to the OP, mostly Placebo'ly.. That does not mean a 200W amp won't bring out the best of the 804 Diamond that does not seem hard to drive base on the Stereophile review and the manufacturer specs. I do understand you are affected by your experience with that PIO ICE amp.

 

[AcuDefTechGuy]

When referring to the B&W speakers as difficult I was not inferring to the amount of wattage. Even today some amplifiers do not handle certain loads very well. Throwing more wattage at the issue doesn't fix the real problem.

Also, saying Brand X amplifier sounded just fine at some wattage does not imply that Brand Y will do the same.

The ICE amplifier I used with B&W speakers claimed stable down to 4 ohms. I could hear the distortion during explosions / loud volumes and was amazed that no other review site or reviewer mentioned this potential problem. Only after purchasing a Parasound amp did I find this review:
Pioneer SC-07 Measurements and Analysis | Audioholics


This is not the only amplifier reviewed here that had issues with complex loads.


Red Dragon M1000 MkII and M500 MkII Setup | Audioholics

Good point. I've never used ICE amps. All the amps I use are solid class A/B amps for all speakers and subwoofers.

But the Rotel 1095 isn't an ICE amp. It is class A/B.

So perhaps B&W speakers are "difficult" to drive if you're using ICE amps. But it's not difficult to drive if you are using solid A/B amps.