Power amp, By wiring question, the next weekest link.

[Andrew @ Bristol]

Hi,

New poster alert.

My children have just about left the nest and finally the time has come that I can re-invigorate the home entertainment system and use it without the constant 'Dad turn it down comments'

Horror of horrors when sitting down a couple of weeks ago I noticed one of my speakers had a faulty driver, nothing other than the perfect excuse to go and buy some new main's so I went for B&W 603 S2 anniversary addition tower speakers to replace some mission Audio Silvers.

I have put a few hours on them and they are breaking in nicely but I noticed that under load, I have been getting clipping in the mid/base where the mission audios were not, looking at the specks I suspected that my AV receiver (FMJ380) is not up to the job, it sounded fine on unfussy music but tasked with lots of mid/base it left the sound week, just sounded like it was out of power. Excuse 2 to invest in a new Power amp a Arcam PA720. While waiting for that in the mean time I have set the cross over point to 60hz (form 40) for the Sub which seems to have helped

My question is how best can I wire the front speakers up, the PA720 has 7 channels, I am running a 5.1 set up with a REL sub, so I will have 2 spare channels on the PA720, is there value in bi wiring the 603's on 4 channels or just leave on 2 I would need to split/duplicate the single? I would also be interested if anyone else has a similar set up what cross over they run at?


Thanks in advance

Andrew

 

[highfigh]

Hi,

New poster alert.

My children have just about left the nest and finally the time has come that I can re-invigorate the home entertainment system and use it without the constant 'Dad turn it down comments'

Horror of horrors when sitting down a couple of weeks ago I noticed one of my speakers had a faulty driver, nothing other than the perfect excuse to go and buy some new main's so I went for B&W 603 S2 anniversary addition tower speakers to replace some mission Audio Silvers.

I have put a few hours on them and they are breaking in nicely but I noticed that under load, I have been getting clipping in the mid/base where the mission audios were not, looking at the specks I suspected that my AV receiver (FMJ380) is not up to the job, it sounded fine on unfussy music but tasked with lots of mid/base it left the sound week, just sounded like it was out of power. Excuse 2 to invest in a new Power amp a Arcam PA720. While waiting for that in the mean time I have set the cross over point to 60hz (form 40) for the Sub which seems to have helped

My question is how best can I wire the front speakers up, the PA720 has 7 channels, I am running a 5.1 set up with a REL sub, so I will have 2 spare channels on the PA720, is there value in bi wiring the 603's on 4 channels or just leave on 2 I would need to split/duplicate the single? I would also be interested if anyone else has a similar set up what cross over they run at?


Thanks in advance

Andrew

What does the FMJ380 show for the volume level when you use it at its highest output level, what are the dimensions of your room and how far from the speakers is the main listening position?

 

[Andrew @ Bristol]

Thanks
I tend to set the amp at 80/100 and use the Blu Sound (Streamer and DAC) to turn it up and down, if I run it at more than 100% on the DAC the distortion cuts in at around 65/100 on the amp if that makes sense The room is 5mrs by 4 mtrs and my listening position is circa 3 mtrs from the the speakers that point down the length of the room.

 

[highfigh]

Thanks
I tend to set the amp at 80/100 and use the Blu Sound (Streamer and DAC) to turn it up and down, if I run it at more than 100% on the DAC the distortion cuts in at around 65/100 on the amp if that makes sense The room is 5mrs by 4 mtrs and my listening position is circa 3 mtrs from the the speakers that point down the length of the room.

You never want to raise the level to anywhere near 100%, especially if you don't know the voltage sensitivity of the piece receiving the signal or the output voltage of the piece that's sending the signal. I have to think that you're familiar with the sound of distortion used for guitars- raising the output of one device to a level that exceeds the needs of the last piece in the signal chain is exactly how they get that sound. It's called 'overdrive' and while it's desired for some music, it's impossible to achieve clean sound in a music reproduction system. You want to cut the level from the BluSound, not the AVR.

If you need to set the AVR's level to 80% and the BluSound to 100%, you need more power. However, your new speakers are rated for amplifier output of 200W, which will only provide an increase of 3dB over a 100W amplifier.

Since we live in three dimensions, post the height, too.

 

[Leemix]

Usually for the best sound you would want the bluesound at a fixed output (which probably is 100% but its a setting) and use the AVR for the volume control but i guess you are using variable output on the bluesound for the ease of the in app volume control?

Are you using a digital out or analogue out from the bluesound?


Sent from my iPad using Tapatalk

 

[PENG]

Excuse 2 to invest in a new Power amp a Arcam PA720. While waiting for that in the mean time I have set the cross over point to 60hz (form 40) for the Sub which seems to have helped

It may be a good excuse to get an amp but in terms of "power", the PA720 is not going to help much. Between the two, the difference may be up to 1 dB at best, more likely closer to 0.5 dB.

Setting XO to 80 or even 100 Hz (definitely not 40 Hz) would help a little but no much as the impedance dip to 4-6 Ohm over the range of around 100 to 500 Hz if the S2's impedance characteristics (no measurements found) is similar to the S3's (Stereophile measured it). It would be worse if it it more similar to the 603's.

Backing off the volume obviously would solve the problem, otherwise I would suggest you follow B&W's advise:

Recommended amplifier power
30W - 200W into 8Ω on unclipped programme

and get a power amp rated at least 200 W 8 Ohm, 300 W 4 Ohms and not the little PA720.

 

[Andrew @ Bristol]

Thanks for the answers and advice. I will try some higher cross over values @ 60 and 80, I do hope the PA720 does have a bit more oomph as the manual does suggest that in 2 channel mode it is a higher WPC, 140w - if it struggle then perhaps i will change for the PA240 for the fronts if i can't bi-amp the 2 spare channels.

I have tried both the digital and analogue out on the Blusound, on the old speakers i recall using the DAC in the Blusound was better, on the B&W, the amp DAC has sounded better which really surprised me.

room Hight is 2.3 mtrs.

 

[PENG]

Thanks for the answers and advice. I will try some higher cross over values @ 60 and 80, I do hope the PA720 does have a bit more oomph as the manual does suggest that in 2 channel mode it is a higher WPC, 140w - if it struggle then perhaps i will change for the PA240 for the fronts if i can't bi-amp the 2 spare channels.

I have tried both the digital and analogue out on the Blusound, on the old speakers i recall using the DAC in the Blusound was better, on the B&W, the amp DAC has sounded better which really surprised me.

room Hight is 2.3 mtrs.

You can compare their specs as follow, based on the info from their manuals.

Two channel driven, PA720: 140 W into 8 Ohms, at 0.2% distortions vs the AVR380's 115 W at 0.2%.
So numerically it seems like a lot, but in terms of dB that is only 0.86 dB.

It will likely make more difference into 4 Ohms, but that's just my educated guess as the AVR380's manual did not provide an output spec for into 4 Ohms. Still, even if we assume the PA720 can do 1.5X better than the AVR380 into 4 Ohms, the difference in dB will still be less than 2 dB. You need 2X the output to get 3 dB more SPL.

The PA240 would be a good choice, if you want to stick with Arcam.