How much amplifier power do I need?

[mac mini]

My Adcom 555 power amplifier has died and I'm thinking of replacing it with a Bryston 3Bsst. On paper, the Adcom is more powerful and I'm wondering if a decrease of 50 watts will be missed. My listening habits are low to moderate volume unless alcohol or unexplained mania takes hold, then its time to get out The Who Live at Leads.

The Adcom is rated 200 watts @ 8 ohms 20 Hz to 20kHz .09% total harmonic distortion and 325 watts into 4 ohms with .25% total harmonic distortion.

The Bryston is 150 watts 8 ohms .005 THD +noise, 250 watts 4 ohms .007 THD.

My room size is 23 ft by 13 ft with a vaulted ceiling 9ft on the ends and 14 ft at center for a total of about 3500 cubic feet. It adjoins a kitchen eating area with 23 ft by 12 ft by 8ft totaling 2200 cubic feet. The kitchen and family room are partially separated by 4 ft wall 6 feet long. My present speaker's efficiency are 87 db 4ohm (3.2 ohm minimum).

What do think, is the 150 watt Bryston OK, or should I stick with 200 watts?

 

[AudioMayhem]

What kind of speakers?

 

[catfish]

'but this volume goes to 11' ~ Spinal Tap

 

[mac mini]

What kind of speakers?

AR9lsi, but I'm thinking about moving on to something different, what I don't know.

 

[AudioMayhem]

Once I thought about it for a minute I realized you probably won't be able to hear a difference, 1.5db. Checkout the following link.

http://forums.soundandvisionmag.com/showthread.php?434632-IG-COF-How-much-power-do-you-need

 

[bobaloniny]

Im just curious, how many times have you listened at more than 75 watts ( I just picked a random number).
If you are thinking of switching speakers too, then maybe shoot for more efficiency into 8 ohms. Then you could rest assured the cutting down to 150 wpc would be a non issue.
The up list in my sig is running in about the same cubic area and seems plenty at about 45 wpc.

 

[mac mini]

Once I thought about it for a minute I realized you probably won't be able to hear a difference, 1.5db. Checkout the following link.

http://forums.soundandvisionmag.com/showthread.php?434632-IG-COF-How-much-power-do-you-need

By that chart a low efficiency speaker will produce 112 decibels at about 225 watts. I googled how loud is 110 db and got a motorcycle, subway, rock concert and baby crying. None of which I want to hear in my house. Maybe I'll try to borrow a sound meter from work.

 

[1tumbleweed]

I'm betting the Bryston has more real power than the Adcom. Not that the Adcom isn't a good amp, just that the Bryston is built to a higher standard.

The Bryston may prove a bit more colorless than the Adcom, too. Or, conversely, the Adcom may sound more "hifi" than the Bryston. It depends on your speakers. In the past, I've found Brystons to be a bit...um...too neutral for my taste. Just my opinion, YMMV.

 

[whoaru99]

The calculator I use is here: http://myhometheater.homestead.com/splcalculator.html

Seems to jive fairly close to my crude measurements.

Bear in mind those are peak levels. At full, clean power the average level will be 10dB less than these peak numbers.**

**Depends on music type and dynamic range. 10dB is a good average number, IMO.

 

[whoaru99]

I'm betting the Bryston has more real power than the Adcom. Not that the Adcom isn't a good amp, just that the Bryston is built to a higher standard.

The Bryston may prove a bit more colorless than the Adcom, too. Or, conversely, the Adcom may sound more "hifi" than the Bryston. It depends on your speakers. In the past, I've found Brystons to be a bit...um...too neutral for my taste. Just my opinion, YMMV.

I'd say the Bryston likely is rounded down in the ratings, but probably not 50 or more watts worth. That much sandbagging is usually the territory of the amps that show doubling down in their specs.

 

[mac mini]

Im just curious, how many times have you listened at more than 75 watts ( I just picked a random number).
If you are thinking of switching speakers too, then maybe shoot for more efficiency into 8 ohms. Then you could rest assured the cutting down to 150 wpc would be a non issue.
The up list in my sig is running in about the same cubic area and seems plenty at about 45 wpc.

Isn't a 4 ohm speaker more efficient than an 8 ohm assuming that both have the same rating, i.e. 86 db? The rated efficiency is identical but most amplifiers are 1.5 times more powerful at 4 ohms as opposed to 8 ohms. The problem is a lot of amplifiers don't do 4 ohms very well. Or are most 8 ohm speakers just inherently more efficient i.e. 90 db or greater?

 

[whoaru99]

^^^
No, not necessarily. You have to be wise to the way the speakers are rated.

If the spec is "X" dB/W/m then the sensitivity is the same. If the spec is "X" dB/2.83V/m then the sensitivity is 3dB different because 2.83V is 2 watts at 4 ohms but only 1 watt at 8 ohms.

 

[mac mini]

The calculator I use is here: http://myhometheater.homestead.com/splcalculator.html

Seems to jive fairly close to my crude measurements.

Bear in mind those are peak levels. At full, clean power the average level will be 10dB less than these peak numbers.**

**Depends on music type and dynamic range. 10dB is a good average number, IMO.

Cool chart. I like how it does the math for you. Using an efficiency of 87 and wattage ratings of 250 (Bryston @ 4 ohm) and 325 (Adcom) there is only a 1 decibel difference, 109.2 vs. 110.4.

 

[mac mini]

^^^
No, not necessarily. You have to be wise to the way the speakers are rated.

If the spec is "X" dB/W/m then the sensitivity is the same. If the spec is "X" dB/2.83V/m then the sensitivity is 3dB different because 2.83V is 2 watts at 4 ohms but only 1 watt at 8 ohms.

Why would a speaker's efficiency be rated in the 2.83 V format, isn't the whole idea of a rating to give a quick reference without having to do math?

 

[AudioMayhem]

Why would a speaker's efficiency be rated in the 2.83 V format, isn't the whole idea of a rating to give a quick reference without having to do math?

I think the marketing department picks whichever voltage helps the speaker sell more.