THE ALL CHANNELS DRIVEN FALLACY

[MACCA350]

Well, they are not talking about 3600W, just 1000W or so. Many car alternators can in fact deliver over 100A at 12V or slightly higher voltage. No doubt the current draw will be high but most music don't demand 1000W continuously, nor can any normal people withstand that kind of SPL inside a car of normal size.

Yes, I didn't say they were, it's merely an observation.

Most car alternators are made to produce enough to run the car with a bit of headroom, I suppose if your looking at drawing this much you'd check if the alternator is up to the job and possibly beef that up.

Also there are many that would put more than one their car, and that would quickly eat up the available power. In which case I guess you'd add a few batteries pump up your alternator and maybe add a few caps to cover it.

cheers

 

[mantol]

Actually dynamic power is relevant to sound quality. The Krell amp you are so fond of likely has alot of overhead past its 125wpc rating, especially when driving low impedance loads. Again, see my post above for other reasoning. Regardlnt ess, this thread was not discussing sound quality as much as the validity of a very conditional and unrealistic test (that isn't followed as consistantly as it should be) as well as the reasoning why some amplifiers don't do well with these tests b/c their design goal is to deliver real world dynamic range in an economical package.

This is a broader point of view for you have taken into consideration not only the users point of view but also that of the manufacturers. The manufacturers when designing a product must be able to predict or determine the real world scenario for it will have a great impact on the production cost and bottom line as a result. That's why engineers are there to apply engineering economics in any equipment they produce. In short they don't over design a product if this is not really needed normally. To satisfy every whims of so few people is not a good business strategy.

For home products, we don't need this all channel driven scenario for all we want is to enjoy music and not to permanently damage our ears. The specs is correct on per channel basis because it is designed that way. However, to design a power supply on the basis of all channel driven is pointless for this is not the real world scenario (incl. NEC standardsfor every home convinient outlet) and not good engineering economics. You can still economize by considering the load factor under which a power supply is subjected to under normal condition, say 50% or 70% of the overall supposed load.

For a venue like a big auditorium, there are separate units available for this application and there are some who follow this route even for home applications, just to make sure that their units are rated all channel driven.

 

[jcrobso]

Just some FYI,,

If you analyze power usage by octave you find out that about 80% of the power is used at 150hz on down. You are more likely to run out of power on you sub before you mains. John

 

[skizzerflake]

Hello:
I'm in the process of setting up my dedicated home theater/music room. The room is 18' X 12', so of mid size. I've read with great interest the entries on this forum for several months and have a feel for which components I'd like to purchase.

My question concerns Amp Wattage.... If I buy a 130 watt per channel A/V reciever, is this enough to produce quality sound for a room of this size. Or should I buy a 200 Watt per channel Amp and use my reciever as a pre/pro. How much audible difference is there between 130W and 200W?

My speakers are Anthony Gallo Ref3s, plus Anthony Gallo Dues used for surround. I listen 50/50 to music/movies. My budget for receiver is about $3500.


Any help appreciated!!

There isn't as much difference between 130 and 200 watts as you might think, only about 2 decibels, which is barely audible if at all. Most of the time your speakers will be running at a couple watts at the most and the high power only kicks in for a second or two when cars blow up or the big one hits California. As long as you have a good, self amplified subwoofer (low frequencies are what really eats power), 130 WPC should be plenty. It is more important what an amp does when it approaches its clipping point but you probably won't know that until you stress test it.

Actually there is a stark limitation in how much current a receiver can draw and that's what would require a high voltage power cord (like what you use for an electic dryer) in order to qualify for a UL approval or not blow a fuse. A 200 WPC unit (which would draw 200 X 7 X about 50% efficiency = 2800 watts) might limit current to what would be drawn by the lower power unit and would NOT be able to supply 200 watts to all channels at the same time (an unlikely event at tolerable volume levels). Don't worry about the exact power too much; 130 WPC will rock the house).

 

[Buckeyefan 1]

There isn't as much difference between 130 and 200 watts as you might think, only about 2 decibels, which is barely audible if at all. Most of the time your speakers will be running at a couple watts at the most and the high power only kicks in for a second or two when cars blow up or the big one hits California. As long as you have a good, self amplified subwoofer (low frequencies are what really eats power), 130 WPC should be plenty. It is more important what an amp does when it approaches its clipping point but you probably won't know that until you stress test it.

Actually there is a stark limitation in how much current a receiver can draw and that's what would require a high voltage power cord (like what you use for an electic dryer) in order to qualify for a UL approval or not blow a fuse. A 200 WPC unit (which would draw 200 X 7 X about 50% efficiency = 2800 watts) might limit current to what would be drawn by the lower power unit and would NOT be able to supply 200 watts to all channels at the same time (an unlikely event at tolerable volume levels). Don't worry about the exact power too much; 130 WPC will rock the house).

That depends on if you're using a $800 130 watt per channel Yamaha receiver in two channel mode, versus a 200 watt per channel $5000 dedicated amp or $800 pro-audio amp. This power comes in nanoseconds - not hours, and every extra nanosecond means quite a bit as far as output goes. Don't believe everything you read. RMS ratings has its issues.

 

[Seth=L]

200 watts RMS @1Khz.

 

[Tyreman]

Something I have wondered for years but don't see to much comment about it.
Maybe somebody knows.
After Bob Carvers magnetic field amp stuff went around it was at one time supposedly being developed by various companies in their receivers and amps in their own configurations and schemes.
I guess I just figured another design for that was in fact in use by home theatre receiver manufacturers for these 5.1,6.1 or 7.1 channel and counting designs.
Basically the power is apportioned as dictated by channnel/program demand.
Here is poop sheet specification from a large name brand receiver too.
I found interesting
"• Maximum Power Consumption [General model only]
6ch, 10% THD ................................................................. 1100 W"

 

[no. 5]

Here is poop sheet specification from a large name brand receiver too.
I found interesting
"• Maximum Power Consumption [General model only]
6ch, 10% THD ................................................................. 1100 W"

10% THD?? bet it's at 1kHz too.

 

[Malice]

If you analyze power usage by octave you find out that about 80% of the power is used at 150hz on down. You are more likely to run out of power on you sub before you mains. John

Or if your mains go as low as 30Hz then it makes sense to consider bi-amping to supplement the lower ranges.

Here's the lab test report on the Denon3805 which shows how the power output across the channels change with different number of channels running.

 

[djsHTnut]

I have been obsessed with getting a new receiver or separates. I have a Sony STR-DE998 Receiver; I like how it sounds and never get close to the max volume and still enjoy it. At the same time I am always paranoid that I may be missing something as far as sound goes. After reading this article, which has been very helpful, I am inclined to not even look at WPC ever again and am wondering if spending more money on more electronics is even going to give me anything extra to add to the experience when watching a movie or listening to music. Sony is knocked around by a lot of people about not being good receivers, so that is partially why I am always afraid I am missing something. As it is I only paid $160 at CC as an open box on the 998, so as far as value goes I think I made out there. I have been willing to pay close to $700 to find a new receiver, but I don’t think it is worth it anymore. Also reading how manufacturers can easily manipulate ratings without adding any value has made me disappointed. I think now would be a good time for me to focus on other things like room acoustics and presentation rather than worrying about what I missing as far as gear goes.

Does anyone have an opinion on this in anyway, whether it is the quality of the receiver and if I am really missing anything or thoughts on any of the subject? I guess I am kind of venting, but this article has educated me more and also enlighten me to the ways of manufacturers.

 

[Seth=L]

While I agree that power ratings are skewed you have to consider many other factors.

If you never push a receiver, or amplifier to its limits then power should probably not be a concern. The problem with manufacturer specs is that they can be completely untrue.

What gets called into question with Sony with most of us here is their quality control. With Sony it is basically hit and miss, sometimes they release something decent and reliable and other times they release total crap. Truth is, just about any manufacturer does this, but I believe Sony is more prone to this type of problem.

What you should really looking for in a receiver are its features(and reliability). Connections, processing, multi-zone capabilities if you need those, ergonomics, and other amnemities you would like.

 

[Aholloway17]

Among the other things you will have to contend with...I agree with DaveOCP. Recent studies revealed that many well known HT amps (Sony, JVC, Denon etc) loose almost 25% of thier rated power when driving all channels over 30% output. In fairness, that difference you may never see or miss but why go down that path in the first place. Checking with a reputable store with intelligent reps
can provide you with those details on amps that you like.

Good Luck

 

[BobMcD]

speaker recommendations?

[/QUOTE=Pyrrho;102084]With 8-ohm speakers with a sensitivity of 88 dB/1 Watt/1 metre, and rear speakers rated at 8 ohms with a sensitivity of 89 dB/w 2.8v (1m), 130 watts should be more than enough. The actual results will vary by room (and speaker placement and seating location), but you can subtract 3 dB per extra meter you are from the speaker, and then calculate the sound level to get a rough idea of what you are likely to get. Assuming you are 2 meters from the speakers, you should get about 95 dB at 10 watts, which is quite loud. You should get about 105 dB with 100 watts (keeping in mind that we are talking about only one channel; each additional channel would add 3 dB to the figure, assuming the same efficiency speakers, and assuming that the sound from each speaker does not cancel out the other speakers due to being out of phase, etc.). If you were 3 meters from the speakers (you could not be that far from all of them in your room), we would be talking about approximately 82 dB at 1 watt, 92 dB at 10 watts, and 102 dB at 100 watts, with only one channel driven. As we are also talking about continuous power, your peaks should be able to be louder./QUOTE]

Can anyone recommend an inexpensive but pretty efficient speaker to use in a home theater? I don't want to get buried in responses, so focus on the "inexpensive" part. Thanks

 

[westcott]

Can anyone recommend an inexpensive but pretty efficient speaker to use in a home theater? I don't want to get buried in responses, so focus on the "inexpensive" part. Thanks

Well, one of the most efficient\sensitve designs is the horn loaded speaker. Two manufacturers that come to mind are Klipsch and the new HSU Research HB1. The latter is probably less expensive at $130 per speaker. The center HC1 is around $200. The Klipsch RB10 or the B-3 are probably the closest in price to these. There are cheaper horns in the Klipsch line. Just run over to their site and see what fits in your budget. I would not lower my standards too far though. Speakers are important and it is money well spent.

 

[BudgetAudiophil]

Nice budget... go with separates.

Hello:
I'm in the process of setting up my dedicated home theater/music room. The room is 18' X 12', so of mid size. I've read with great interest the entries on this forum for several months and have a feel for which components I'd like to purchase.

My question concerns Amp Wattage.... If I buy a 130 watt per channel A/V reciever, is this enough to produce quality sound for a room of this size. Or should I buy a 200 Watt per channel Amp and use my reciever as a pre/pro. How much audible difference is there between 130W and 200W?

My speakers are Anthony Gallo Ref3s, plus Anthony Gallo Dues used for surround. I listen 50/50 to music/movies. My budget for receiver is about $3500.


Any help appreciated!!

If you go with Outlaw or Emotiva separates, you can get your 200 watts/ch, have the flexibility of separates, AND stay under your $3500 budget. Both companies currently have sales, too (assuming you haven't already bought... I read a few pages of this string, most of which was argument regarding "all channels driven").

A 990/7700 will comes in under $2900 (combo deal) and they'll ship for free. Emotiva's flagship setup (DMC-1 / MPS-1 ) combo is just under $3200 and is also shipped for free. There are less expensive combos available on both sites. You have a lot of options at this price range.

As far as the "all channels driven" contraversy goes... this forum seems to have covered it well with regards to the usefulness of this test. It's not real world, and is only an indicator of an amplifier's POTENTIAL. Personally, I wouldn't call the measurement useless, but it's not something to hang your hat on, either. It say little about actual performance. The longer-winded testing I've seen done by reviewers on this forum are far better indicators of how well an amp will drive speakers/loads.

With that said, I'm of a mind that when it comes to _quality_ amplification, there is no substitude for horsepower. Certainly, the amount of power you will need/use depends entirely on your speakers, room size and accoustic qualities, and volume at which you listen. What beefier amplifiers give you (in most cases, still speaking of high quality amplifiers) is enough reserve power required for musical transients, potential for better base performance/cone control, and the ability to play louder without compression. All of these things are very important in the real world. [I'll let others argue the subtleties of musical reproduction between amplifiers and stick with a more scientific approach.]

A benefit of going the separates route is flexibility in your upgrade path, dedicated power supplies for each component, lower noise floor*, and better overall performance, all else being equal.

As far as 130W vs. 200W... all else being equal, there's less than a 3dB difference between the two (there's a 3dB difference between 100W and 200W, which is deemed an audible difference in total volume). A more useful figure is how much headroom each amp has. Even more pertinent is the efficiency and load of your speakers, and the volume at which you want to listen. Room size and accoustics are also critically important in a proper HT setup, and play a role in how much power reserve you need.

If you listen at reference levels, go with more power. You can't go wrong having extra power reserves at your fingertips.


* I've done direct A/B, level-matched comparisons between a high-end Arcam reciever vs. a similarly power rated Arcam pre-pro/amp combination. Speakers were Thiel CS1.6s. I was expecting any differences to be subtle in nature, but was floored by the completely different sound between the two. To save a lot of typing, the difference was akin to putting a not-quite sound-transparent cloth over the speakers when listening through the reciever. No doubt it was due to lower noise floor (clarity differences) and higher quality amplification of the separats. Perhaps the pre-amp section was less clean in the receiver, too, but that's just a guess I have no way to verify.

In my own tests at home, using a Pioneer Elite reciever vs. my new Outlaw Audio 990, I came to a similar conclusion.

 

[BudgetAudiophil]

oops

I guess I should have checked the date before replying...

 

[Audioholics]

Lol... welcome to the forums anyway!

 

[recess1978]

amps

both of those are great

 

[TLS Guy]

Power and speaker efficiency

Whether you have enough power or not depends om the efficiency of the speakers. That I could not find at the Gallo website. Remember the decibel scale is a log scale.

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/sound/u11l2b.html

So if you want to double the loudness of a 130 watt amp with speakers of the same efficiency, then you need a 1300 watt amp, So going from 130 watts to 200 watts is only a few db increase in loudness, and not very significant.

The speaker efficiency will have a lot more impact, and they are all over the map. Speaker efficiencies vary from 83 db 1 watt one meter to the high 90s. So a speaker with an efficiency of 93 db one watt 1 meter will play twice as loud as a speaker with an efficiency of 83 db one watt one meter with the same power input. So if you want to double the loudness from your system you in fact need 1300 watts per channel.

You seem to be putting a nice system together. I would strongly recommend using an audio visual preamp with separate power amps.

 

[annunaki]

Becareful with you use of the term "efficiency". You mean check sensitivity ratings. Efficiency numbers on drivers themselves are very low. I am sure you knew that already though judging by your other posts.