# How do I know if my receiver has enough power not to "clip"?



## goodears (Jan 2, 2013)

How do I know if my receiver has adequate power for 7.1 HT? So I can play it loud enough to get good accuracy and clarity. I don't mean ear bleed but loud enough but at the same time not clip and blow up a speaker tweeter. What power rating should I look for? Is this why people buy amps to go along with their receiver (so they don't blow something up)?


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## AudiocRaver (Jun 6, 2012)

It depends a lot on your speakers. Do you already have speakers or know what you want to get?


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## goodears (Jan 2, 2013)

AudiocRaver said:


> It depends a lot on your speakers. Do you already have speakers or know what you want to get?


Tsi300 at the moment cs20 but I don't know if I will keep them.


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## AudiocRaver (Jun 6, 2012)

There are a lot of factors, here is a one way to approach it:

Start with speaker efficiency, add for Dolby reference level, add for headroom, add for the room, add for other factors.

Per channel:

Start the calculation at 0 dB.
The TSi300s have an efficiency rating of 90 dB, I assume with 1 W RMS at 1 m, that is the "standard." For Dolby reference level (85dB), subtract 5 dB (85 dB - 90 dB = -5 dB).
For headroom (highest instantaneous peaks), the Dolby standard says add 20 dB.
For home theater seating at 10 feet (3 m), (distance x 3) add 4.8 dB (6 dB theoretical for each doubling of distance in open space, but in a typical HT/listening room it is closer to 3 dB).
This example adds up to (0 - 5 + 20 + 4.8) = 19.8 dB relative to the 1 W reference point for the TSi300s, or 95 W available amplifier power needed (19.8 dB is 95x for power). It would allow you to run at Dolby reference level and experience the full dynamic range of Blu-rays & DVDs.

Fudge factors:

If your individual preference was to run your movies a bit louder then the Dolby reference level once in awhile, cranking it up 6 dB, which is roughly 1.5x louder, that quadruples the peak power you would need, but the speakers are only rated to 150 W peak, only 2dB higher than 95 W, so they couold not handle that amount of power.
If for some reason the room is REALLY DEAD, lots of sound absorption (you hear no echo or reverb at all with a good hand clap), then the 4.8 dB for distance above becomes 9.6 dB instead of 4.8 dB, another 3x the power. Not likely, though, and, as with the last calculation, your speakers wouldn't be able to handle it.


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## JDEaston (Dec 30, 2011)

AudiocRaver said:


> There are a lot of factors, here is a one way to approach it:
> 
> Start with speaker efficiency, add for Dolby reference level, add for headroom, add for the room, add for other factors.
> 
> ...


I agree with your numbers, the math is spot on. I will add that the 20db dolby recomends for peaks, would be dynamic power, rather than continuous. So to get a more exact answer one would have to know what kind of dynamic power their amp can produce, and subtract that from the 20db dolby recomends. Also in my experience most people listen below reference level, every 3db's below cuts the amount of power you need in half. 

In my opinion, 35wpc is all anyone with 90db sensitivity speakers would ever use in real world scenarios. But as far as the OP goes, its really impossible for anyone to give you an accurate answer without knowing your listening preference in decibals. I will tell you first hand that 2wpc, stereo, on my uncles la scalas will run most ppl out of the room.


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## AudiocRaver (Jun 6, 2012)

JDEaston said:


> Also in my experience most people listen below reference level, every 3db's below cuts the amount of power you need in half.


Good point, 85 dB is quite loud as a "normal" volume level, then you get multiple channels running on top of that. Most people are likely to run lower rather than higher.

Perhaps an exception would be a well-treated HT room. The 85 dB level is not as grating in a dead room, reflections well controlled, low reverb time.



> In my opinion, 35wpc is all anyone with 90db sensitivity speakers would ever use in real world scenarios. But as far as the OP goes, its really impossible for anyone to give you an accurate answer without knowing your listening preference in decibals. I will tell you first hand that 2wpc, stereo, on my uncles la scalas will run most ppl out of the room.


Agree. The 70 to 80 W per channel common in mid-level AVRs allows for a lot of headroom with efficient speakers, the way most people listen most of the time. The OP has to ask himself, "Do I want to be able to CRANK it once iin awhile?" Then the cranked level probably equates to the Dolby 85 dB numbers. If crankability is not a requirement, then probably half that power (-3 dB) is enough.


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## JDEaston (Dec 30, 2011)

AudiocRaver said:


> Good point, 85 dB is quite loud as a "normal" volume level, then you get multiple channels running on top of that. Most people are likely to run lower rather than higher.
> 
> Perhaps an exception would be a well-treated HT room. The 85 dB level is not as grating in a dead room, reflections well controlled, low reverb time.
> 
> Agree. The 70 to 80 W per channel common in mid-level AVRs allows for a lot of headroom with efficient speakers, the way most people listen most of the time. The OP has to ask himself, "Do I want to be able to CRANK it once iin awhile?" Then the cranked level probably equates to the Dolby 85 dB numbers. If crankability is not a requirement, then probably half that power (-3 dB) is enough.


Yeah, it all depends on how loud a person prefers to listen and the sensitivity of their speakers. If one prefers a few db's below reference, pretty much any avr on the market can provide adequate power, as long as your speakers have decent efficiency. 

Although if you want enough headroom to listen at reference level on occasion, you need double the power, or will likely see problems, which puts you around the midlevel avr price bracket. And last, if you prefer reference level, you should allow yourself a few db headroom, which in my opinion means you should be looking at separates, amps/processor. Though a flagship avr may suffice if you have efficient speakers. 

Long story short for the OP, your speakers efficiency and your own listening preferences are the biggest factors in how many wpc you need. Just a few db's in either direction makes a huge difference in the wattage you need. So unless you plan on a major upgrade (ie: from 70wpc to 140wpc) your not likely to notice much of a difference, if any at all.


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## 8086 (Aug 4, 2009)

[PIE]How do I know if my receiver has enough power not to "clip"?[/PIE]


All amplifiers will clip at some point, typically the early stages of clipping happen somewhere past the 50-60% :meter: of it's volume or power capacity. More is always better and the best advice I can give is to get the most you can afford.


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## AudiocRaver (Jun 6, 2012)

I second that thought, to a degree. There are areas in a setup where you have to decide how conservative you want to be, and what you are willing to pay for it. Another factor of 2x available power? 4x? How conservative do you want to be, why, what is the potential gain, what is the available budget, the budget priority relative to other needs? I would be plenty comfortable with an extra 2x factor for available power (8 ohms speaker, typical two way or three way design, NOT electrostatic), to be confident in having really clean dynamics.

Then again, if you have money to burn, go WAY higher.


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## mvision7m (Feb 9, 2013)

Keep in mind how most AVRs are rated when reviewing them also. Not sure if someone else already said this but all but a few AVRs are power rated with only one or two channels driven from 1 meter away and only at the 1kHz range so it's max power rating isn't true especially with all channels going at once. The truly top notch AVRs out there are power rated with all channels driven so generally their power is truer and most times even higher than their rated output. The initial power rating on most AVRs however may seem enough but in a 5.1/7.1 set up driving all channels that power will dip significantly while still needing to provide headroom for peaks. Also, I may be wrong but I think I read somewhere that most AVRs with auto calibration systems calibrate output to 75db at the 0 position. That's 10db lower than actual reference level and unless you live in a palace, 75db in a home setting with peaks that will hit above that reference mark is plenty loud for movies and music. I bring that point up in regards to your question about clipping, if my info is correct, and please, someone correct me if I'm wrong and you know differently, you should not get any clipping up to that 0 volume position (once the system is properly calibrated) but I'd never venture past that. I have a Yamaha RX-V3800 which boasts 140w x 7 channels (again, not true with all channels driven), it's volume goes from -80db to +16db. Every time I run the auto calibration program (called YPAO), before outputting any of those calibration signals the receiver will set its volume to 0 as the reference point. So, my thinking is that if the reference point is 75db at the 0 position then I should be able to listen at 0 safely without clipping coming in. You've also got to account for peaks which may not leave enough headroom at 0 so I have a max volume set at -5db to be sure that I don't get any clipping. Even with all of that in mind, I've never found a reason to listen to any program material at higher than -10db although my A/V room is probably just under average in size. I hope my input was helpful to you in some way. The more true, clean power, the better. Good luck.


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## BruceW (Feb 5, 2013)

Thank you for the information..


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## jackfish (Dec 27, 2006)

mvision7m said:


> Keep in mind how most AVRs are rated when reviewing them also. Not sure if someone else already said this but all but a few AVRs are power rated with only one or two channels driven from 1 meter away and only at the 1kHz range so it's max power rating isn't true especially with all channels going at once.


Any amplifier sold in the US must have a power rating with at least two channels driven (unless it only has one channel). And "1 meter away" has nothing to do with amplifier power ratings.


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## mvision7m (Feb 9, 2013)

jackfish said:


> Any amplifier sold in the US must have a power rating with at least two channels driven. And "1 meter away" has nothing to do with amplifier power ratings.


You may just be right about more recent amps sold in the U.S. but I don't know if that was always true. if not, depending on the age of the amp/receiver, it may have been rated "the old way". 

I'm certainly not an expert but I have read (and no, I don't believe everything I read) that some receiver manufacturers claim certain power specs that are only achieved under very specific conditions that would hardly, if ever be recreated at home. And, I also read that to achieve those bogus, trumped up power ratings they have only one channel driven at a relatively easy frequency, usually 1kHz. 

I mistakenly added the part about measuring from one meter away, that applies to speaker testing not amp ratings. Thanks for correcting me on that.


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## JDEaston (Dec 30, 2011)

jackfish said:


> Any amplifier sold in the US must have a power rating with at least two channels driven (unless it only has one channel). And "1 meter away" has nothing to do with amplifier power ratings.


I have seen lower end avr's rated at 1ch driven with a 1khz sine wave, even though they were 5.1ch receivers.


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## jackfish (Dec 27, 2006)

JDEaston said:


> I have seen lower end avr's rated at 1ch driven with a 1khz sine wave, even though they were 5.1ch receivers.


OK, document that please, where? Cite or URL, thank you. Again, all amplifiers sold in the US must have, at a minimum, the rated power specification for two channels driven. Most spec sheets for AVRs will show power ratings for the "associated channels"; one rating number for the Front channels, right and left driven; one rating number for the Center channel; one rating number for the Surround channels, right and left driven; and, one rating number for the Rear channels, if applicable, right and left driven. Hence, the ratings at a minimum reflect two channels driven, even though the center channel as an individual "associated channel" is given it's own rating value which is usually equivalent to the wpc with two channels driven.


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## JDEaston (Dec 30, 2011)

jackfish said:


> OK, document that please, where? Cite or URL, thank you. Again, all amplifiers sold in the US must have, at a minimum, the rated power specification for two channels driven. Most spec sheets for AVRs will show power ratings for the "associated channels"; one rating number for the Front channels, right and left driven; one rating number for the Center channel; one rating number for the Surround channels, right and left driven; and, one rating number for the Rear channels, if applicable, right and left driven. Hence, the ratings at a minimum reflect two channels driven, even though the center channel as an individual "associated channel" is given it's own rating value which is usually equivalent to the wpc with two channels driven.


A quick look at yamaha's website does show 1ch driven at 1khz on their lower end models. You are right though, because it also gives a 2ch measurement, though only with a 1khz tone, not 20hz-20khz. My point though, was that retailers often list only the 1ch spec when advertising these units. A lot of the boxes these avr's are packaged in also advertise this way.


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## jackfish (Dec 27, 2006)

Yeah, and the FTC amplifier rule does not apply to advertisements, only product literature. Thanks for the info.


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## Owen Bartley (Oct 18, 2006)

AudiocRaver said:


> Per channel:
> 
> Start the calculation at 0 dB.
> The TSi300s have an efficiency rating of 90 dB, I assume with 1 W RMS at 1 m, that is the "standard." For Dolby reference level (85dB), subtract 5 dB (85 dB - 90 dB = -5 dB).
> ...


This is great, how have I not seen this calculation laid out so clearly before? Thanks AudiocRaver, I'll have to remember those steps and store it away somewhere.

To the OP, many people find that reference level can be uncomfortably loud, so get an idea of what target you actually want to achieve and work back from there. If you're just looking for headroom, most good quality equipment today should be OK, unless you try to pair really hungry speakers with a budget receiver or something.


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## JDEaston (Dec 30, 2011)

jackfish said:


> Yeah, and the FTC amplifier rule does not apply to advertisements, only product literature. Thanks for the info.


It makes no sense for the ftc to mandate that amplifiers be tested with two channels driven, but have no protocol on how the manufacturer advertises. Nor do they seem to mandate full range frequencies to be tested. It seems like its just a way for the ftc to make themselves money to me. It shows that the tests are flawed, in many ways, and are basically pointless.


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## JDEaston (Dec 30, 2011)

Since the way manufacturer's rate power was discussed in this thread I figured I would post something I found odd, to say the least.

A new line of Denon receivers were anounced today, called the E series. I noticed the power specs reported in the press release to be off the charts for an entry level model line. The top of the entry level offers "A maximum of 185 watts per channel." As stated in the press release.

No other wpc figures were given in the press release, other than 165 and 175 "maximum" wpc for their bottom and middle entry level tier avr's.

After a closer look, it appears they are advertising dynamic power, which this is the first time I have ever seen a major manufacturer market this way. It is misleading to say the least.

On Denon's website I found that the 185 maximum wpc translates to an actual 90wpc, 20hz-20khz. It also appears they arrived at 90wpc with only one channel driven, or at least that is what I gathered from the little info provided in the spec sheet.

http://usa.denon.com/us/product/pag...atid=avreceivers(denonna)&pid=avre400(denonna)


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## TheHammer (Dec 16, 2012)

AudiocRaver said:


> There are a lot of factors, here is a one way to approach it:
> 
> Start with speaker efficiency, add for Dolby reference level, add for headroom, add for the room, add for other factors.
> 
> ...


This is a great mathematical model. Thank you for posting it.

One portion I found especially interesting:
"For headroom (highest instantaneous peaks), the Dolby standard says add 20 dB."

Manufacturers are always gaming their specs. Following the FTC guidelines is the best way to compare amps. But when discussing headroom and instantaneous peaks, dynamic power would be a better way to compare amps, if there was a standardized way of measuring the ability of an amp to produce these instantaneous peaks.

This discussion has been going on in audiophile circles for at least 40 years: what is the best way to measure amplifier power that relates to listening to music? Are tightly regulated power supplies desirable, or are ones that allow more dynamic power? I think the FTC guidelines have their shortcomings in regards to being able to measure an amps ability to reproduce dynamic sounds. Yet these same guidelines are a huge improvement over the frequently fictitious peak power vs RMS ratings that used to occur.

I am less impressed with the need to run all 5 or 7 channels at full power at 20 - 20 kHz. There is ample testing to indicate that this never happens in playback of music or video and chasing this spec just adds needlessly to manufacturing costs with no real world benefit.

I agree with the comment that if one needs a large increase in power, that separates are the way to go. It gets to be awfully tough to cram 7 channels capable of 250 watts plus into an A/V chassis. But one should keep in mind that going from 125 to 250 is only a 3 db jump and that is pretty small at what is likely to be a huge jump in cost. A better investment would be into more efficient speakers or pass off some of the load into two powered subwoofers.

http://www.audiokarma.org/forums/archive/index.php/t-329286.html


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## Wolfgang (Feb 17, 2011)

Thanks to AudiocRaver for his mathematical model - it’s the first time I’ve seen something like that. I was able to understand the model after a little head scratching (I’m a mechanical engineer, not an electrical engineer – I wasn’t taught this stuff). After some more reading and head scratching, I created the attached spreadsheet which might be of interest to others :nerd:. I also made a couple of tweaks, one of which is to account for the number of speakers. I found the model helped to put things into perspective, and get a feel for which values make a big difference.

I think most people who’ve contributed to this thread know the following already, but for those less familiar:
•	Placing a speaker near a wall or corner will change its sensitivity. This should depend on the port arrangement and the distance to the wall(s), and should be borne in mind. This effect is also frequency dependent.
•	As I understand it (again, I’m not an EE), these calculations are based on speaker sensitivity at a fixed impedance. Impedance will vary at different frequencies, so this isn’t 100% accurate, but it gives you a decent start.
•	There’s been some discussion in this thread about manufacturers being a bit cheeky with their specs. I’ve seen some speaker reviews include sensitivity testing, so this could help in that regard. In terms of amps, there are a few things to be careful of (as discussed in this thread). One of the better examples on this front is that Emotiva go so far as to publish THD plots and a range of other data for their amps. It might pay to look around a little.
•	In the spreadsheet, the values in the darker blue are the main variables. The lighter blue values are also variables, but perhaps better left alone in most cases.
•	I took some measurements with my SPL meter to get a feel for listening volume. I found 65dB to be a quiet background volume – the kind of volume I’d have when watching the news. 75dB was loud but sustainably so – I could comfortably listen for quite some time at that volume. 85dB was “cranked” – I wouldn’t be comfortable listening to more than a single song when it’s that loud (but I’d sure enjoy it while it lasted). These values might help to provide guidelines for some, when working to a listening volume.


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## tba (Jun 10, 2013)

goodear said '' loud enough''. This is a very important point to start. There are fellows who love 120db as in rock live concerts. I would also point out that the tweeters are mostly blew out by underpowered amps. In the pro area, the recommended amp power is from 1,5 to 2,5 of the speakers power. I am using a preamp + individual power amp/channel. I am using an old Aphex Studio dominator as a limiter and I never blew out any speaker.
tba


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## 3dbinCanada (Sep 13, 2012)

goodears said:


> How do I know if my receiver has adequate power for 7.1 HT? So I can play it loud enough to get good accuracy and clarity. I don't mean ear bleed but loud enough but at the same time not clip and blow up a speaker tweeter. What power rating should I look for? Is this why people buy amps to go along with their receiver (so they don't blow something up)?


I'm purposely leaving the Dolby specs out because very few people listen to their Hometheater at Dolby reference levels because its plainly just too loud. Things to consider are, the size of the room, distance of the speakers relative to the listener position, and what SPL you are truly going for. 

With the exception of NAD who advertises full bandwidth x all channels driven, few AVR manufacturers list full bandwidth at all channels driven. Why? Its not that relevant. There are very few DVD/BluRay that contain equal volume across all channels. I own over 300DVD/BluRay and there is not one in my collection that I can point too that contains equal volume across all channels. There are exceptions but are rare as hens teeth. Couple that with the fact that any bass material is routed to the sub when setting speakers to small. I'm more interested in the 2 channel test results because most of the information in a movie soundtrack is contained across the main left/right and center channels. Most AVR specify their out power in 2 channel driven using full bandwidth.


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## tonyvdb (Sep 5, 2007)

3dbinCanada said:


> few AVR manufacturers list full bandwidth at all channels driven. Why? Its not that relevant. There are very few DVD/BluRay that contain equal volume across all channels.


Actually its not required so they choose not to do it. Many movies have full levels sent to all channels but it usually only lasts a few seconds (enough to drain any reserves that the amps may have), I have a full 8 channel meter array hooked up and have confirmed this with many action movies.



> I'm more interested in the 2 channel test results because most of the information in a movie soundtrack is contained across the main left/right and center channels. Most AVR specify their out power in 2 channel driven using full bandwidth.


 They are only required to test using a 1kHz test tone not full bandwidth Some do choose to post their full bandwith 2 channel readings but most bench tests I have seen (and thats many) do not come very close at all to what they state. They also only test at a distance of 1 meter (who sits that close to their speakers).


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## 3dbinCanada (Sep 13, 2012)

tonyvdb said:


> Actually its not required so they choose not to do it. Many movies have full levels sent to all channels but it usually only lasts a few seconds (enough to drain any reserves that the amps may have), I have a full 8 channel meter array hooked up and have confirmed this with many action movies.


I would agree with your assessment if and only if the AVR is expected to power all channels full range using full range speakers. However, this usually NOT the case as most typical set ups involve setting all the surrounds to small which channels most of the bass energy to a sub. Since the vastly predominant setup in HT involves using a sub and steering bass away from all the channels, an AVR will easily handle the few seconds of all channels firing. My RX-V1800 can drive my PSB Image suite of speakers well into ear bleeding territory without strain or fuss. 




tonyvdb said:


> They are only required to test using a 1kHz test tone not full bandwidth Some do choose to post their full bandwith 2 channel readings but most bench tests I have seen (and thats many) do not come very close at all to what they state. They also only test at a distance of 1 meter (who sits that close to their speakers).


That's why I read only those audio mags that provide test results and leave the subjective "fluff" reviews alone. Most AVR manufactures now provide a full bandwidth test into two channels. Check out their sites.


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## AudiocRaver (Jun 6, 2012)

Wolfgang said:


> Thanks to AudiocRaver for his mathematical model - it’s the first time I’ve seen something like that. I was able to understand the model after a little head scratching (I’m a mechanical engineer, not an electrical engineer – I wasn’t taught this stuff). After some more reading and head scratching, I created the attached spreadsheet which might be of interest to others :nerd:. I also made a couple of tweaks, one of which is to account for the number of speakers. I found the model helped to put things into perspective, and get a feel for which values make a big difference.
> 
> I think most people who’ve contributed to this thread know the following already, but for those less familiar:
> •	Placing a speaker near a wall or corner will change its sensitivity. This should depend on the port arrangement and the distance to the wall(s), and should be borne in mind. This effect is also frequency dependent.
> ...


Wolfgang:

Nice job on the spreadsheet. That is a handy tool.

Room gain: you assumed 6 db loss per distance doubling free field, 3 dB in a room. That means 3 db of "room gain," It will vary somewhat depending on the room. It can be measured and put into the formula as a variable, with 3 db as default if the user does not want to do the measurement. Best way to measure is wide-band pink noise, I think. There is a thread discussing it right now over here. Anyway you could say Play Pink Noise through one speaker; measure SPL at 1 m, measure SPL at 2 m, then Room Gain = (6 dB - (MEAS_at_1M - MEAS_at_2M)).

It is a little hard to know what to do about number of speakers (mono=1, stereo=2, home theater=3?, 5?, 7?), safety factor, etc...

Anyway, nice work.


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## Wolfgang (Feb 17, 2011)

Thanks AudiocRaver.

You're right about room gain of course. I'd deliberately left it as a variable for that reason, but I just didn't know how to work it out any more accurately than that. I now see your comment/formula on room gain, and this makes a lot of sense to me. I see in the thread you linked, there are effectively questions over how room gain is defined in terms of what frequency it's measured at. Pink noise seems a sensible practical concession - there'll still be a gain variation with frequency, but what else do you do?

I presumed the number of speakers would only be complicated if you have 5+ speakers. 1, 2, 3 (although not included in the spreadsheet) & 4 speakers seem relatively straight-forward, according to the reference I put in the relevant xls comments. When you get more than that, it seems there are some complicated cancellation/reinforcement actions taking place. For various reasons, I'm practically limited to a 2.1 or 2.2 system, so my care factor for higher numbers of speakers is somewhat diminished... :whistling:


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## CMiller747 (Jul 15, 2013)

Great calculator/spreadsheet!

I think the best way to ensure your receiver will not clip when processing 7.1 is to get one with line level output jacks for the front channels (at least). As already mentioned using an external sub unloads the AVR from large amounts of LFE power handed off to the external amp. Getting an AVR with external connections, allows for connection of an external amplifier and "unloading" even more of a burden from the AVR. The front mains (almost always) have the highest power demanded by the source material, and will likely be the first to "clip".

If the calculator/spreadsheet is used to properly size the wattage of the receiver this will likely provide adequate power and clipping will be negligible. But if it is noticeable at some point in the future (or present), the jacks are an easy way to upgrade the system. 

Also, the Dolby recommendation for 20 dB of headroom results in 100x the wattage.


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## AudiocRaver (Jun 6, 2012)

Wolfgang said:


> Thanks AudiocRaver.
> 
> You're right about room gain of course. I'd deliberately left it as a variable for that reason, but I just didn't know how to work it out any more accurately than that. I now see your comment/formula on room gain, and this makes a lot of sense to me. I see in the thread you linked, there are effectively questions over how room gain is defined in terms of what frequency it's measured at. Pink noise seems a sensible practical concession - there'll still be a gain variation with frequency, but what else do you do?
> 
> I presumed the number of speakers would only be complicated if you have 5+ speakers. 1, 2, 3 (although not included in the spreadsheet) & 4 speakers seem relatively straight-forward, according to the reference I put in the relevant xls comments. When you get more than that, it seems there are some complicated cancellation/reinforcement actions taking place. For various reasons, I'm practically limited to a 2.1 or 2.2 system, so my care factor for higher numbers of speakers is somewhat diminished... :whistling:


Yes, there are a lot of variables one could play with. I like what you have done, it's a very nice tool.


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## phillihp23 (Mar 14, 2012)

Help me figure out how many watts I need per channel on a receiver. I plan on running 4 floor standing tower speakers and a center on the amp. The other 6 speakers will run off the receiver. 11.2 system.
I filled out the formula sheet as provided above. Just don't know how to interpret it. 
Thanks in advance.




CALCULATE AMPLIFIER POWER FOR GIVEN LISTENING VOLUME 

Speaker sensitivity 89 dB (1W RMS at 1m) 

Distance from seating to speakers 3.8 m 
Volume reduction, for distance doubling 3 dB 3dB for inside rooms, 6dB for open space / anechoic 
Additional volume required for distance 4.5 dB 

Average listening volume 65 dB Dolby reference level is 85dB 
Difference of average & peak volumes 20 dB Dolby standard allowance for headroom is 20dB 
Peak volume at listening position 85 dB 

Number of speakers 8 Enter 1, 2, 4 or 8 speakers 
Volume increase due to no. of speakers 6 dB 

Peak volume at 1m from speaker 83.5 dB 

Required amplifier power per channel 0.3 W RMS To achieve no clipping at peak listening volume


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## AudiocRaver (Jun 6, 2012)

phillihp23 said:


> Help me figure out how many watts I need per channel on a receiver. I plan on running 4 floor standing tower speakers and a center on the amp. The other 6 speakers will run off the receiver. 11.2 system.
> I filled out the formula sheet as provided above. Just don't know how to interpret it.
> Thanks in advance.
> 
> ...


You know your listening habits, so this is not disagreement with your numbers. Are you sure the volume never goes above 65 dB average? That seems pretty quiet. But if that is your number, then the calculation looks correct.

You will not find an AVR with power that low. Perhaps your approach in picking an AVR would be to focus on features you want but with lower available peak power. Minimum you will find in a good brand will probably be in the 60 watt/channel range, which would give you lots of reserve power. That's one way to look at it anyway.


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## Wolfgang (Feb 17, 2011)

I agree with AudiocRaver that getting a better understanding of your listening volume is the first place to look at. In the spreadsheet, I think you want the average listening volume to be the highest that you're likely to listen to on a semi-regular basis. It might be that you only crank it for the odd "demo run" for friends, so perhaps you can skimp on that a little - but I'd be surprised if you never reached 75dB average.

If, however, you never listen at more than 65dB, then yes, you need practically no power to drive your system at that volume.


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## Glen B (Jun 11, 2013)

Check out this Peak SPL calculator: http://myhometheater.homestead.com/splcalculator.html


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## AudiocRaver (Jun 6, 2012)

Glen B said:


> Check out this Peak SPL calculator: http://myhometheater.homestead.com/splcalculator.html


Another handy tool!


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## Wolfgang (Feb 17, 2011)

For reference, the myhometheater link calculates peak SPL, and doesn't have room gain as a variable. There's a difference in the volume reduction for distance that I don't have my head around. :huh:


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## phillihp23 (Mar 14, 2012)

This is the results from the link when I typed my data in:

SPL CALCULATOR 
Speaker Sensitivity: *89* dB SPL (1 W/1 M) 
Amplifier Power: *150* Watts 
Distance: *10* feet 
No. of Speakers: *11* usually 2, more for multi-channel 
Speaker Placement (Choose 1): Away from walls (or do not consider placement) 
* x* Near a wall (within 2 to 4 feet) 
In a corner (within 18 to 24 inches) 

RESULTS 

*21.8* dB Gain from amplifier 
*-9.7 * dB Loss due to dispersion (distance) 
*10.4 * dB Gain from sonic reinforcement (multi speakers) 
*3 db* Gain from placement (reinforcement from reflected sound) 
*114.5 * dB SPL at listening postion


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## AudiocRaver (Jun 6, 2012)

Wolfgang said:


> For reference, the myhometheater link calculates peak SPL, and doesn't have room gain as a variable. There's a difference in the volume reduction for distance that I don't have my head around. :huh:


I gave it another look. Everything that is there seemed to work OK.

No room gain, which makes quite a difference. Your room gain assumption of 3 dB is the way to go. My suggestion of doing a measurement is impractical for a lot of of users, you're better off with the assumption. The "close to wall" and "in a corner" adders are interesting, not sure where those values came from. That seems to be the author's idea of room gain, but it is not really the same thing. They are adders you might consider for your spreadsheet if you could figure out what the numbers should be.

What was it about the volume reduction for distance that bothered you? Unless I missed something, it looked like 6 dB for each distance doubling, which assumes zero room gain. No?


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## Wolfgang (Feb 17, 2011)

AudiocRaver,

I mentioned the reduction in volume due to distance, because I get a different result in this regard between the spreadsheet I posted & the myhometheater link. If you download the myhometheater spreadsheet, the formula is expressed differently (within the cell), and I'm not knowledgeable enough to say whether it's an appropriate approach or not.

I agree with your comments about the speaker positioning & sensitivity tweaks. I had a look around the interweb, and I think I found the source for that. Of course, I've now lost the link. From memory, it was an ex-stereophile guy, writing for a speaker company, saying how the company's tests had shown a certain dB difference between one location and another. He then used this as a hard number to represent every similar circumstance. :doh: I wish I could find the link again, but I suspect that's where this has come from.

I think these changes are going to vary depending on the port arrangement (for example, forward-facing ports should be less sensitive in some regards), how close it is to the nearby surfaces, and also vary with frequency. I'm not sure how I can practically model something this complicated, although I agree it would be nice if I could.


phillihp23,

What you've entered into the linked calculator says you're feeding 150W to every one of the 11 channels, and that all 11 speakers have an 89dB sensitivity (as stated on the webpage). I suppose this is possible, but it sounds unlikely. My understanding is that unless all the channels are identical, the math to work out the variances in power & sensitivity is very complicated. Moreover, there's some further complications relating to sound cancellation & reinforcement associated with so many channels (as stated in one of the links in my posted spreadsheet) that's not covered in the link, and is also very complicated to calculate. You might want to do some further reading to understand what simplifying assumptions could be made to suit your situation.


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## AudiocRaver (Jun 6, 2012)

Wolfgang said:


> I get a different result in this regard between the spreadsheet I posted & the myhometheater link.


There is a minor error in your formula in cell F10, it should be

=F9*LOG10(F8)/LOG10(2)

The 1 m distance is the reference, so the formula needs to give 1/4 the power for every doubling of the 1 m distance (when testing the formula, to get nice round numbers - most of the time - use F9 = 6.0206 or 3.0103)

then with F9 = 6.0206:
2 m distance gives -6 db
4 m gives -12 db
10 m gives - 20 db
etc

same goes for cell F36



> I agree with your comments about the speaker positioning & sensitivity tweaks. I had a look around the interweb, and I think I found the source for that. Of course, I've now lost the link. From memory, it was an ex-stereophile guy, writing for a speaker company, saying how the company's tests had shown a certain dB difference between one location and another. He then used this as a hard number to represent every similar circumstance. :doh: I wish I could find the link again, but I suspect that's where this has come from.
> 
> I think these changes are going to vary depending on the port arrangement (for example, forward-facing ports should be less sensitive in some regards), how close it is to the nearby surfaces, and also vary with frequency. I'm not sure how I can practically model something this complicated, although I agree it would be nice if I could.


You are right, it gets messy. Leave it out, call it good!


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## Wolfgang (Feb 17, 2011)

I understand what you're saying, and perhaps I'm wrong (I'm still not claiming to be an expert), but I think the formula in cell F10 is correct. :scratch:

From the example in the spreadsheet, 86dB would be present 1m away from the speaker, for 1W input power (i.e. 86dB sensitivity). The listening position is 3.8m away from the speaker itself, so only 2.8m should be needed to account for distance, as we already know the volume 1m away from the speaker?


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## tonyvdb (Sep 5, 2007)

The big unknown is room acoustics, the calculator does not take any of that into consideration nor does it know if your room is open or high ceiling. all of this plays a huge part in what you will hear at the listening position.


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## AudiocRaver (Jun 6, 2012)

Wolfgang said:


> I understand what you're saying, and perhaps I'm wrong (I'm still not claiming to be an expert), but I think the formula in cell F10 is correct. :scratch:
> 
> From the example in the spreadsheet, 86dB would be present 1m away from the speaker, for 1W input power (i.e. 86dB sensitivity). The listening position is 3.8m away from the speaker itself, so only 2.8m should be needed to account for distance, as we already know the volume 1m away from the speaker?


Hmmmm...

Set the distance number to 1 m and you should get 86 dB, but you get a formula error (Log(0)). You should even be able to go closer, i.e. at 0.5 m the level should be 6 dB higher. The model we use for this assumes a point source and an expanding sphere. One meter is the common reference chosen but you could choose any distance and calculate from there. Going TOWARD the speaker the SPL theoretically approaches infinity, which of course is not quite true in reality. Your formula should give the following results, assuming 0 room gain:

distance, loss, result
1 m > 0 dB > 86 dB
2 m > 6 dB > 80 dB
4 m > 12 dB > 74 dB
8 m > 18 dB > 68 dB
16 m > 24 dB > 62 dB

.5 m > -6 > 92
.25 m > -12 > 98
.125 m > -18 > 104
.0625 m > -24 > 110

At least that's the way I learned it.


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## Wolfgang (Feb 17, 2011)

:doh:

I stand corrected - thanks for that. Revised spreadsheet attached.


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