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200 vs 400 watts per channel


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I was wondering if I were to get a sunfire multichannel amp to push my 5 forte II's and two quartets is a 400/channel over kill and just a waste of money. Would the 200 watt/channel be adequate. My HT area is about 22 wide by 20 deep. I plan on keeping the amp for a long time with upgrades of other components.

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It will give you a little more headroom, but remember that doubling wattage will give you only a 3dB increase in SPL.

Then again, its always better to have more watts than you need. Exactly how many more than you need is up to you though. If the 200watt/channel amp is of the same quality as the 400watt/channel amp, the 200watter should be fine.

Your speakers are very efficient and as far as I know don't have any low impedences that any amp would have difficulty driving.

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The forte is listed in the heritage brochure with an spl of 96 recommended power of 20 watts and a continuous power of 100 watts. 100 watts should provide an spl of 101db, whereas 400 watts will only provide an spl of 102db assuming the drivers could handle it, which the documentation states they can not. Return on investment going to 400 watts as opposed to 200 watts is just not there.

Some folks report more head room and dynamic range when using over sized amps as opposed to amps that closely match a speakers upper limit. This has some to due with the all channels driven rating of both amps. It is rare for an amp with a shared power supply to produce the same out put at 7 or 5 channels driven that is can at 2 channels driven. Those that can have a very high inrush current and tend to pop circut breakers.

Compare amps at their all channels driven rating, you may need a 130 watt amp rated at 2 channels driven to actually get a 100 watt amp rated at all channels driven.

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ummmm....for a 96dB speaker at one meter:

100W is 116dB

200W is 119dB

400W is 122dB.

But the Forte is a 98dB speaker and the Forte II is a 99dB speaker. That means at one meter that:

1W = 98/99 dB

100W = 118/119 dB

200W = 121/122 dB

400W = 124/125 dB



All these numbers of course assume that there is no power compression

with the speaker. At maximum power handling I would expect at least 3dB

of compression. In fact, looking at the specs online they're rated to

119dB peak output, with a peak 500W peak power-handling. So the forte

(due to its "small" 12" driver) is experiencing over 6dB of compression

at its peak. And probably 3dB of compression at 200W. The speaker will

probably do a clean 116dB with about 50W of power.

To stay out of the distortion range of the amplifier, I find it a good

rule of thumb to have a good 10dB of headroom. So if you ever wanted to

jam cleanly at 116dB (the theoretical limit of clean output from your

speakers), you would need a 400W amp. 116dB is freaken loud. I'm sure

someone is going to mention that the sound gets quieter the further you

are from the speaker, but let's not forget to add 3-6dB to all those

numbers for having two speakers playing (6dB if both sides are playing

the same thing - which is usually true for the bass. 3dB if both sides

are playing different things - usually true for the higher frequencies

where stereo seperation is occuring). Also, the closed space of the

listening room is going to keep the volume from dropping off (when you

really start cranking you'll hear the noise floor get louder).

So all that to say, if you want the maximum performance from your

fortes, then 400W is not unreasonable. A 200W amplifier will yield a

clean 113dB, which is still very loud. I would say 100W minimum for

your speakers. You really only need to go higher if you plan on

exceeding rock concert levels.

Hope this helps.

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Like DrWHO said,200W per channel is plenty.And Remember a quality amp gas 2-3dB headroom for peaks so a 200W/ch amp can deliver 400 and in many cases more.On short peaks,as your speakers would have roasted VC from thearmal overheating would you ever try to run them @ 200W continous(impossible to do with muisc/HT).

And yes anything above even 114dB at listening position is bad news for your hearing,And plus lets not forget even if you had speakers capable of an uncompressed 130dB (very large horn loaded mains monitors are capable of these absurd levels) your hearing will go into protection mode and compression is still an issue.So above 110dB unless you are a cyborg,is almost of no practical use(those deaf among us will say YES you need 120dB playback,let these hearing impaired brag [;)] ).

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Jacksonbart, It's a 65 mustang 2+2 fastback. I got it when I was 16 and totaled it out twice. It's obviously been redone which took more cash input than it's worth but I still have it for sentimental reasons.

The reason I'm asking about the power of the amps is not to get more db's. It is for more clarity and punch. I presently have a Denon 3805 which I think is rated at 120 or so watts/channel. Loud I don't need, I want calrity and definition or what ever at the same db level. I'm kind of partial for sunfire from what I've read, but have never heard one yet. I just wanted to know if I would be wasting $'s by going for the 400 watts/channel over the 200 watts/channel of the same multichannel amp.

PS edit: I plan on using the 3805 as the pre/pro for awhile. Just curious about the external amp and which would make the biggest difference and bang for the buck.

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Denon's claimed 120W per channel,is true if ONE channel is driven.The Sunfire power amp,even the least capable one will leave any Denon receiver in the dust.

You will have both much more reserve,and Sunfire amps are very smooth making them ideal mates for Klipsch speakers.Smoother sound,any agression present in the Denon amp,gone.A definite good buy,if you get the more potent SUnfire for not much more than the 200W go for it.Or at least if budget permits

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Smoother sound,any agression present in the Denon amp,gone.

Will this still hold true if he uses the Denon as a pre-amp? Or does the aggression come from the Denon's internal amp, which would be by-passed if used as a pre?

One of my questions was going be is how does the 3805 work out? For I have my eye on the 3806 which I believe is basically the same. But by the sounds of it, the Ear says Denon and Klipsch are not a good match???

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Smoother sound,any agression present in the Denon amp,gone.

Will this still hold true if he uses the Denon as a pre-amp? Or does the aggression come from the Denon's internal amp, which would be by-passed if used as a pre?
One of my questions was going be is how does the 3805 work out? For I have my eye on the 3806 which I believe is basically the same. But by the sounds of it, the Ear says Denon and Klipsch are not a good match???

Yes it will hold true,I use a Denon 4806 as PREAMP in a smaller system I have,and outboard amps...as yes amps.The preamp section is the Denon while not of audiophile grade(ultimate transparency and inaudible operation)is quite good in quality.

So yes the Denon will match well with the Sunfire in a prepro/power amp setup.

no no and no,I never said the Denon as a preamp is not a good match with Sunfire,it will do fine.SImply its internal amps are several steps down from Sunfire power amps.

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As far as reciever pre-amps go, Denon has always been my favorite. The amplifier sections in recievers are never optimal, but the nature of the device shouldn't require them to be.

As far as which amp to get...how big of a factor will buyer's remorse be? If you get the 200W/channel are you going to be double thinking the 400Q amp? The way I see it, "too much" amp just means "more headroom" which usually means lower distortion.

One thing, I notice is that they rate their output at 1kHz, not a 20-20kHz full bandwidth signal. Also, if you look at the power ratings for their amps, both amplifiers will draw no more than 1800W from the wall before the fuse flips. Assuming pefect efficiency, the 200W amplifier will draw up to 1400W. The 400W amplifier will draw up to 2800W....which means the 400W amplifier isn't going to be able to deliver all of its power where the 200W amplifier will. You couldn't expect much more than 250W of real power from the amp (assuming very good effiency). Granted you'll never be pulling peak power from every channel at the same time either.

I'm not exactly sure how I would interpret all of this information so I'm sharing in hopes of spurring conversation. One thing I've picked up about amplifier design is that it's usually less harmful to overdraw the power supply than to over supply the transistors doing the amplifying. The first results in clipped output whereas the second usually results in smoke. I'm by no means an amp expert and I don't know if this holds true for all toplogies - seems to make sense though.

From the specs, I wouldn't doubt if the 7400 and 7200 shared the same power supply; making the 7400 limited by the powersupply and the 7200 limited by heat. It's kinda silly to be talking about the clip point of amps though considering you should be running the amplifier in a linear region of its output (we're only looking at a 3dB difference here). The only question that comes to my mind is what sacrifices (if any) were made to the low signal behavior with the 7400 to achieve the extra power handling. If I were in your position I would contact Sunfire and see if you couldn't get any distortion measurements at 100mW, perhaps with a full bandwidth signal too. It's not exactly an inexpensive purchase to be making.

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Thanks everyone for your input. I'm not going to take the plunge just yet I was kind of keeping my eye on Audiogone for a used model. Then debating going with the 5 channel amp to try it first and just run my rear centers off the denon. Or maybe if your going to go bear, go grizzly, and get the 7 channel model. I've seen some come up once in a while. My nearest sunfire dealer I can find is Chicago and that is 3 hrs away. Oldbuckster do you have the oldman's disease and can't sleep in the morning or have you just been up all night?

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I have the Sunfire Theater Grand IV With the 200 x 7 amp.

Now, I use La Scalas.. (7) of them too, but it is more than enough power.. Amp never gets hot, even running all day and part of the night too...

I would go for the 200 x 7, you might use the channels later or for a separate feed? And having to buy a 200 x 2 later would be expensive. I know of a Sunfire dealer here in Indianapolis, IN to get you good prices if interested.. Sunfire sounds pretty excellent (IMO) with Klipsch too. Great headroom seems fast and pumps out music and movies effortlessly. Most people just walk in and their jaws drop. It's that awesome. The picture grabs them first.... yes... But the sound.. OMG the sound, just compliments the whole experience.

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Wait, I thought the crack everyone made on receivers is the multi channel amp not being robust enough to deliver rated numbers to all channels. I am not talking about el cheapo receivers either. Why would you go with a 7 channel amp then? It would suffer the same fate. In most cases with multi channels of say 120 watts or more the limiting factor is the UL rating for a 15 amp circuit breaker/outlet. Are the people cracking on higher end receivers running dedicated 30 amp service to there amps or simply plugging it to a wall socket?

I don't know, but think you get much more bang for your bucket with acoustic treatments/room changes

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