[felix_suwarno]

i have never heard people discussing it in here. well i havent tried the search function though, but it seems to me that everytime i see ama thread asking about amplifier recommendation, damping factor is never mentioned.

a friend of mine, an acoustic expert / sound engineer helped me with my choices on an amplifier.

i think i need 5 or 7 channel amp, around 125 watts per channel. if i found a 200 watts per channel amp for 5 channels not much more expensive than 125 wpc for 7 channels, i think i would prefer the 200 wpc 5 channels.

okay, so i found
b&k reference s2 125.7. msrp 1399 bucks.
sherbourn 5/1500. msrp 1750 bucks. this one seems to be discontinued, i couldnt find it on sherbourn's website. so i compared the b&k with sherbourn 7/1250A for 2000 bucks msrp.

my friend asked me to compare their damping factor, and it turned out that b&k amp's damping power is rated at 180 at 50 hz. the sherbourn is below 150 on the lower freq, if i am not mistaken on reading the graph.

http://www.sherbourn.com/PDF/7_1250A...250aReview.pdf
page 5

http://www.bkcomp.com/pdf/8445%20bkR...tsht.1.0.2.pdf
page 2

so, my friend recommended b&k. cheaper as well.

what do you guys think?

while we are on it, any recommendation on an amplifier, around 1500 dollar, 5 or 7 channels, not less than 125 watt per channel?

thank you.

[John Wes]

If your looking to spend under 2 grand on a 7 channel amp with 200 watts, look at the MPS-1 from Emotiva.

http://www.av123.com/products_produc...s&product=18.1

Hopefully this is ok here.....

Audioholics rates it as the amp of the year.

http://www.audioholics.com/productre...ductawards.php

[alan halvorson]

Damping factor is the inverse of output impedance. As the output impedance of an amplifier is part of the load, it changes the frequency response of a speaker, especially at the lower end; thus, it is desirable to keep the output impedance as low as possible/damping factor as high as possible - to minimize this change. How high is good enough? Opinions vary, but certainly 100 - maybe lower - is quite adequate. On the other hand, my amp, a Crown Macro Reference, makes a big deal about a damping factor in the many thousands. Undoubtedly overkill, but it does have the best bass of any amp I've had in my system (the only difference between amps I've ever been able to identify).

If damping factor is important to you, stay away from tube amplifiers, particularly SE designs. Tube amps typically have output impedances of 1-3 ohms, sometimes higher, which really disrupts the frequency response of a speaker.

[Doug_]

felix,

You may also want to look into Outlaw amps. They are putting out a new model within the next few weeks. Here are the spces on their old 7-channel amp:


Power output: 200 watts RMS x 7 (all channels driven simultaneously into 8 ohms from 20 Hz to 20 kHz with less than 0.05% total harmonic distortion). 300 watts RMS x 7 @ 4 ohms

Signal to Noise: 119dB "A" weighted

Power Bandwidth: 5 Hz - over 100 kHz (+0/-3 dB)

Crosstalk: Greater than -90 dB from 20 Hz to 20 KHz

Damping factor: 850 (10 Hz - 400 Hz)

Gain: Voltage gain of 28 dB.

Slew rate: 50 Volts/microsecond

Remote Trigger voltage: 3 - 32 volts DC

Power requirements: 115 V 50-60 Hz

Power consumption: 1,800 watts (maximum)

Dimensions (W x H x D): 17.2 x 7.75 with feet x 18 (inches)

Weight: 90 (lbs)



I have 2 of their 5-channel 755 models and have been very impressed with them. They shouldn't set you back as much as the Emotiva MPS-1 as well.

[Chu Gai]

As a singular figure of merit, the specification of damping factor is about as useless as tits on a bull. It is frequently presented by a company's marketing department to perhaps influence sales in some fashion. The damping factor or its proportional inverse, the output impedance, typically varies not only with the output level but with frequency. However, if the damping factor is exceedingly low (a high output impedance), what you'll find is that the amp will behave somewhat like an equalizer when driving a speaker load.
With the two amps your friend suggested, there is no reason to pick one over the other based on the published DF's. For that matter, would one necessarily choose an amp whose published DF was 1000?
I'd consider basing your purchasing decision on such factors as availablity of service, resale value, warranty, features (needed or desired), and to some extent the amount of power you need based on your speakers sensitivity, listening distance, and the volume you listen to as well as the program material you play. You might want to give some thought to perhaps purchasing a 3-channel amp to simply handle the fronts.

[ChrisDixon]

While I don't have an analogy as imaginative as Chu's bull, I have to agree. I seem to recall that the math proves out that a damping factor of 11 is all that's needed for an 8 ohm load. Obviously you'd like a little padding, so 100 is more than enough. As others have said, a larger number above what is needed will not improve performance in any way.

Chris

That assume that everything else remains equal between an amp with a DF of 100 and one with say 1000 which we know likely isn't true. The NuForce mono blocks I'm now running claim a DF of 1000 or so and I must say they've got very very good bass response but I don't know enough about the rest of their design to say that its solely a result of the DF being so high. Regardless you don't choose cars based on horsepower alone so lets look at some of the other factors you will want to consider. Which speakers do you own? How large is your room and how loud do you listen to music/movies. Do you own a large subwoofer or are your fronts uses as large for movies or music?

[felix_suwarno]

thanks guys.

i dont live in the states. so outlaw is out of the question. i checked their website and i think they dont sell internationally except canada.

i am planning on a new living room with a home theater ( not the other way around, so cozyness or, "living roomness" is more important...appearance of my hardware should be aesthetically pleasing without sacrificing performance by purchasing bose, bang olufsen, or anthony gallo stuff ).

size of the room would be 2.8 meter high, 4.5 meter wide, 11 meter long ( half of the room would be used as my working space and library with big bookshelves covering the entire back wall and half of side wall - hope you get what i mean ).

i WANT monitor audio gold signature gs20 as mains, gs lcr as center, and gs10 for the surrounds and back surrounds. for the back surrounds...perhaps i might consider silver rs or the older gold reference 10.

i dont like the idea of purchasing heavy to drive speakers, such as the 4 ohm ones.

i am into both music and movie. hmm let me think.... perhaps 80 percent music 20 percent movies? i will work in this room as well, so the music will always be turned on.

the room itself is still in its early planning stage. it will have ht related treatment on the wall, ceiling and floor. dunno how much money i will spend on everything, it is a long on going project.

chu's advice makes sense to me. thanks.