Looking for advice on power (1 Viewer)

[Jeff1125]

Howdy from Texas folks. As I mentioned in another post a few weeks back, my wife and I are in the process of building a home with a dedicated media room. It will be wired for a 5.1.4 setup, and the size of the room is 14'-11" x 17'-6" x 9'. As the completion of the house draws near, I am starting to look more and more and what kind of equipment I need, and have been doing research lately on power ratings, wattage, impedance, RMS, peak power, etc. Different sites seem to have differing opinions on how much power is needed for a room of this size. I won't constantly be looking to blow the roof off the place, but I will at times want to crank up the sound and "feel the boom" from movies and music, as well as to show off the power to friends and family. My question is, is there such a thing as a rule-of-thumb for power\wattage based on the size of a room (min vs max power), or is it just a matter of what sounds best to me? I have been looking at receivers like the Yamaha RX-A2080 and the Denon AVR-X3700H. I'd like to have something that I can use for the next several years, and my budget for a receiver is about $1000 - $1500.

I am by no means an expert when it comes to electricity, and without a lot of options to go somewhere and listen to a setup these days, I'm not exactly sure what my range should be. Any advice is appreciated! Thanks!

​

 

[Wayne A. Pflughaupt]

My question is, is there such a thing as a rule-of-thumb for power\wattage based on the size of a room (min vs max power),

There is not. The reason is that it largely depends on the speakers selected. Speakers that are very efficient can be driven to ear-bleeding levels with maybe only 20 watts, while inefficient speakers may require 150 watts to get the same volume.

That said, both AVRs should have no problems driving any speaker with efficiency ratings in the 86-89 range as loud as you want. However, between the two, the Yamaha appears to have a more robust amplifier section.

Regards,
Wayne A. Pflughaupt

 

[ManW_TheUncool]

In addition to what Wayne said, you should probably understand that it takes 10x the watts to yield 2x the apparent/perceived loudness (or increase of 10db on the decibel scale), so for instance, it takes 200 watts to yield 2x the loudness (or 10db increase) of 20 watts given the same set of speakers. And yeah, once you get near/into the 200 watts territory, it's generally not about getting perceivably louder anymore, but about yielding best sound quality throughout w/ capacity to deal w/ transients, ie. spikes in loudness -- well, that should be true at lower power levels too of course, but you're not as limited (in terms of power) at getting louder from the lower levels.

Speakers are usually rated at db per 1 watt at 1 meter distance, so speakers rated at 86db/W/m, which is fairly common amongst avg efficiency, good speakers, would need 10 watts to get to 96db and 100 watts to get to 106db (from 1 meter away). But remember, the rating is typically for 1 meter away while you typically lose 6db for each doubling of distance, eg. -6db at 2 meters, -12db at 4 meters, so in practice, that same combo of speakers+AVR ratings would yield ~91-to-97db, ie. 106db - ~9-to-15db, from your normal viewing/listening position (of say 3 to 5 meters) depending on what that is. That's probably loud enough for most, but not all, folks, especially at 3 meters or so... and not all AVRs (and dedicated amps) yield the same quality and capacity for dynamic range, etc (across all aspects of the signal/sound) for what's (usually vaguely) specified by manufacturers.

Also, room size and other environmental factors (like floor coverings, ceilings/walls, furniture, etc) will/can affect perceived loudness possibly adding (or less often subtracting) upto a few dbs...

_Man_

 

[Dave Upton]

Howdy from Texas folks. As I mentioned in another post a few weeks back, my wife and I are in the process of building a home with a dedicated media room. It will be wired for a 5.1.4 setup, and the size of the room is 14'-11" x 17'-6" x 9'. As the completion of the house draws near, I am starting to look more and more and what kind of equipment I need, and have been doing research lately on power ratings, wattage, impedance, RMS, peak power, etc. Different sites seem to have differing opinions on how much power is needed for a room of this size. I won't constantly be looking to blow the roof off the place, but I will at times want to crank up the sound and "feel the boom" from movies and music, as well as to show off the power to friends and family. My question is, is there such a thing as a rule-of-thumb for power\wattage based on the size of a room (min vs max power), or is it just a matter of what sounds best to me? I have been looking at receivers like the Yamaha RX-A2080 and the Denon AVR-X3700H. I'd like to have something that I can use for the next several years, and my budget for a receiver is about $1000 - $1500.

I am by no means an expert when it comes to electricity, and without a lot of options to go somewhere and listen to a setup these days, I'm not exactly sure what my range should be. Any advice is appreciated! Thanks!

​

Hi Jeff,

I'm in TX too! There's a fair bit of nuance to this, as it really depends what speakers you will be driving.

Do you already have speakers picked out or in mind?

Speakers have two attributes that determine what sort of amplification you need.

1) All speakers have an electrical impedance they present to the amplifier. This is measured in Ohms, and is typically listed at 2, 4 or 8 Ohms. The impedance is often not quite what is advertised (note all speakers are a 4 or 8 ohm load, so the value is often rounded) and can vary quite a bit.

2) Each speaker has a sensitivity factor that denotes how easy they are to drive. This used to be measured in SPL/w/1m - so sound pressure produced by 1W at 1m. This is now changing to SPL/2.83V/1m - which is a more accurate measurement that good designers are adopting.

Here's a screengrab from our forum sponsor SVS' website, showing both values for the Prime towers:

These speakers have an 8 ohm impedance, and are 87 dB sensitive.

Here's what you would do to figure out how much amp you need. First, note the sensitivity and plug it into this calculator I threw up, along with your approximate seating distance from the speakers:

https://www.hometheaterforum.com/amplifier-speaker-spl-calculator/

This will give you a required amplifier power.

The important thing to note is that there is average power, and peak power. Average is the amount you need 98% of the time. Peak is what you need during big explosions or the loudest segments of a movie.

I typically recommend using a target average SPL of 85dB, and a peak SPL of 99dB (peaks in some movies might go slightly higher, but this is rare). It's also worth noting that you typically want some headroom, or extra power in the amplifier to ensure you don't run out. I recommend 3dB. That means you would want to aim for 102 dB in the calculator if your goal was to always have extra power.

Plugging in some basic values you provided (assumed listening distance of 4m/12ft), you'd need 251 watts to accomplish true 102 dB reference level listening in your theater with the speakers above. If you don't turn it up to reference level, you could get by with 126 watts to reach 99dB.

Now, look at your given receiver, and look up its power output into your speakers impedance. Here is the spec page from the RX-A2080:

From this, we can see that you're likely to see approximately 165 watts from this unit.

Going back to our trusty calculator, 165 watts means you'll get a max usable SPL of 100.1 dB and should be just fine.

I hope this helps!

 

[SmCaudata]

To add, impedance varies with frequency.

In looking for home theater speakers, I came across the downloadable spec sheet for the architectural (in-wall) speaker. They show db drops off access at different frequencies along with dB output at different frequencies using 2.8e V. All speaker companies should give data like this for all speakers.

300 IWLCR6 - 3-way in-wall loudspeaker - Focal

The 300 IWLCR6 built-in loudspeaker is made in France and dedicated to a home use. This LCR (Left, Center, Right) loudspeaker is perfect for a Home Cinema set-up with no compromises, in rooms of up to 320ft².

www.focal.com

 

[ManW_TheUncool]

To add, impedance varies with frequency.

In looking for home theater speakers, I came across the downloadable spec sheet for the architectural (in-wall) speaker. They show db drops off access at different frequencies along with dB output at different frequencies using 2.8e V. All speaker companies should give data like this for all speakers.

300 IWLCR6 - 3-way in-wall loudspeaker - Focal

The 300 IWLCR6 built-in loudspeaker is made in France and dedicated to a home use. This LCR (Left, Center, Right) loudspeaker is perfect for a Home Cinema set-up with no compromises, in rooms of up to 320ft².

www.focal.com

Only problem w/ digging that deep into specs is, well, it probably becomes much too complicated and very difficult to navigate and use for vast majority of folks.

In the end, it's about system synergy that probably requires plenty of careful auditioning and trial-and-error (typical of the audiophile hobby) once you get to that level of minutiae. That or simply avoid speakers that present excessively strange and difficult loads unless you already know good, viable matches. Having the data *might* help narrow down the choices to try, but then again, maybe not... unless amp makers provide more useful data to match...

_Man_

 

[JohnRice]

To add, impedance varies with frequency.

In looking for home theater speakers, I came across the downloadable spec sheet for the architectural (in-wall) speaker. They show db drops off access at different frequencies along with dB output at different frequencies using 2.8e V. All speaker companies should give data like this for all speakers.

300 IWLCR6 - 3-way in-wall loudspeaker - Focal

The 300 IWLCR6 built-in loudspeaker is made in France and dedicated to a home use. This LCR (Left, Center, Right) loudspeaker is perfect for a Home Cinema set-up with no compromises, in rooms of up to 320ft².

www.focal.com

..and they won't, because the impedance swings of most speakers tends to be rather extreme. Better brands and designers will take this into consideration and produce better sounding speakers. The late speaker designer Jim Thiel always contended that a reasonably flat impedance curve was extremely important, but it's difficult and expensive to achieve. The crossover is a major factor in achieving this, and crossovers aren't exciting, so they don't promote people to buy one speaker over another.

 

[ManW_TheUncool]

..and they won't, because the impedance swings of most speakers tends to be rather extreme. Better brands and designers will take this into consideration and produce better sounding speakers. The late speaker designer Jim Thiel always contended that a reasonably flat impedance curve was extremely important, but it's difficult and expensive to achieve. The crossover is a major factor in achieving this, and crossovers aren't exciting, so they don't promote people to buy one speaker over another.

I suspect a big factor of the issue is the generally accepted (audiophile) notion/principle that it's generally better to subtract than add to the signal/sound.

If these impedance variances generally lead to (not too much) subtraction, instead of addition, to the signal/sound where they occur, it probably usually sounds fine (enough) to us. It becomes more a matter of which losses we find acceptable and not detract too much (or at all) from our enjoyment.

That's probably why a lot of good speaker designers/makers prefer to sacrifice deep bass response (even before subs became popular and very good) and sometimes also roll off the extreme high frequencies a bit. They're also often fine w/ small dips in the upper bass region where crossover is typically needed between drivers.

You don't usually find good speakers (or electronics) presenting upward spikes OTOH. Just mostly dips and rolloffs...

_Man_

 

[Jeff1125]

There is not. The reason is that it largely depends on the speakers selected. Speakers that are very efficient can be driven to ear-bleeding levels with maybe only 20 watts, while inefficient speakers may require 150 watts to get the same volume.

That said, both AVRs should have no problems driving any speaker with efficiency ratings in the 86-89 range as loud as you want. However, between the two, the Yamaha appears to have a more robust amplifier section.

Regards,
Wayne A. Pflughaupt

Thank you Wayne, the Yamaha is the model I'm leaning towards.

 

[Jeff1125]

Hi Jeff,

I'm in TX too! There's a fair bit of nuance to this, as it really depends what speakers you will be driving.

Do you already have speakers picked out or in mind?

Speakers have two attributes that determine what sort of amplification you need.

1) All speakers have an electrical impedance they present to the amplifier. This is measured in Ohms, and is typically listed at 2, 4 or 8 Ohms. The impedance is often not quite what is advertised (note all speakers are a 4 or 8 ohm load, so the value is often rounded) and can vary quite a bit.

2) Each speaker has a sensitivity factor that denotes how easy they are to drive. This used to be measured in SPL/w/1m - so sound pressure produced by 1W at 1m. This is now changing to SPL/2.83V/1m - which is a more accurate measurement that good designers are adopting.

Here's a screengrab from our forum sponsor SVS' website, showing both values for the Prime towers:

View attachment 87484

These speakers have an 8 ohm impedance, and are 87 dB sensitive.

Here's what you would do to figure out how much amp you need. First, note the sensitivity and plug it into this calculator I threw up, along with your approximate seating distance from the speakers:

https://www.hometheaterforum.com/amplifier-speaker-spl-calculator/

This will give you a required amplifier power.

The important thing to note is that there is average power, and peak power. Average is the amount you need 98% of the time. Peak is what you need during big explosions or the loudest segments of a movie.

I typically recommend using a target average SPL of 85dB, and a peak SPL of 99dB (peaks in some movies might go slightly higher, but this is rare). It's also worth noting that you typically want some headroom, or extra power in the amplifier to ensure you don't run out. I recommend 3dB. That means you would want to aim for 102 dB in the calculator if your goal was to always have extra power.

Plugging in some basic values you provided (assumed listening distance of 4m/12ft), you'd need 251 watts to accomplish true 102 dB reference level listening in your theater with the speakers above. If you don't turn it up to reference level, you could get by with 126 watts to reach 99dB.

Now, look at your given receiver, and look up its power output into your speakers impedance. Here is the spec page from the RX-A2080:

View attachment 87488

From this, we can see that you're likely to see approximately 165 watts from this unit.

Going back to our trusty calculator, 165 watts means you'll get a max usable SPL of 100.1 dB and should be just fine.

I hope this helps!

Thanks Dave, and howdy neighbor! This is indeed very helpful. It's one of the more understandable explanations of all power and how it works.

I haven't chosen any speakers yet. I've always been drawn to SVS, but I'm also looking at some from Yamaha, just to match brands.

One question on watts per channel. When a receiver specs for this like rated output power, max effective output power, is the wattage indicated per channel, or the total watts available across all channels in use? In other words, is a 200w receiver really 200w per channel, or does it "depend?"

 

[Jeff1125]

To add, impedance varies with frequency.

In looking for home theater speakers, I came across the downloadable spec sheet for the architectural (in-wall) speaker. They show db drops off access at different frequencies along with dB output at different frequencies using 2.8e V. All speaker companies should give data like this for all speakers.

300 IWLCR6 - 3-way in-wall loudspeaker - Focal

The 300 IWLCR6 built-in loudspeaker is made in France and dedicated to a home use. This LCR (Left, Center, Right) loudspeaker is perfect for a Home Cinema set-up with no compromises, in rooms of up to 320ft².

www.focal.com

So in looking at the spec sheet for this speaker, do the dB level and distance variations indicate that a speaker's efficiency rating vary depending on how far away the listener is? Efficiency rating is not necessarily a static number?

 

[JohnRice]

Sensitivity is typically measured at 1 meter, for comparison. Nobody actually listens to speakers that close, so what happens in a room is more complicated.

 

[Dave Upton]

Thanks Dave, and howdy neighbor! This is indeed very helpful. It's one of the more understandable explanations of all power and how it works.

I haven't chosen any speakers yet. I've always been drawn to SVS, but I'm also looking at some from Yamaha, just to match brands.

One question on watts per channel. When a receiver specs for this like rated output power, max effective output power, is the wattage indicated per channel, or the total watts available across all channels in use? In other words, is a 200w receiver really 200w per channel, or does it "depend?"

Jeff,

The specs for most receivers will define both if you dig a little deeper. For example, using the Yamaha above, we can find the following on their website.

To translate this to plain english, this means:

In ideal situations using a test tone playing at a single frequency (1kHz) you are rated to get 155 watts for two channels (left and right).

When playing all frequencies more like real life/movie watching, you get 140 watts for the left and right channels.

This is all a pretty clever way to avoid mentioning how power drops with all channels driven. Some manufacturers will share this number too, but it's becoming harder and harder to find numbers one can trust.

I would say as a general rule - you should plan to lose a fair bit of that power on all channel loads. Here's a review of the last iteration, the RX-A2070 by Sound&Vision, which had identical specs to the 2080, and shows a substantial loss in power with all channels:

The moral of the story here is that one needs to be very cautious when buying a receiver, as the devil is in the details and most specs intentionally lie.

For folks who are more serious about home theater, I almost always recommend moving to separates, where you have an amplifier that you keep for the long haul, and your receiver becomes a processor, basically a receiver without the amplification section. There are several excellent amplifiers on the market you could consider, but you'd likely have to spend towards the upper end of your budget, and go for a used processor/receiver to feed it. I would definitely lean that way if you're amenable.

 

[JohnRice]

I haven't chosen any speakers yet. I've always been drawn to SVS, but I'm also looking at some from Yamaha, just to match brands.

Jeff, there is no reason, none at all, to match your electronics brand with your speaker brand. In fact, electronics brand speakers are usually low quality, or at least a lot lower than you can get from speaker manufacturers. There are exceptions, but to the best of my knowledge Yamaha isn't one of them.

 

[JohnRice]

View attachment 88098

The moral of the story here is that one needs to be very cautious when buying a receiver, as the devil is in the details and most specs intentionally lie.

For folks who are more serious about home theater, I almost always recommend moving to separates, where you have an amplifier that you keep for the long haul, and your receiver becomes a processor, basically a receiver without the amplification section. There are several excellent amplifiers on the market you could consider, but you'd likely have to spend towards the upper end of your budget, and go for a used processor/receiver to feed it. I would definitely lean that way if you're amenable.

I just thought this graph was worth repeating. Look at that drop in power when you use all the channels.

 

[SmCaudata]

I just thought this graph was worth repeating. Look at that drop in power when you use all the channels.

How about the stepwise route? For instance I was planning on getting the Anthem 1140 for my new setup. It seems that the preamp outs from the receivers have actually improved enough that the AV receivers make good processors. In this way, you could add amps later if needed and then down the road get a new processor for new tech?

The Audioholics review of the new SR8015 from marantz showed that there was a cuttoff so that when using RCA outs there was no noise from it when turning up the volume, this was apparently not the case with the 8013. I'm assuming with these new designs where outputs are assignable and when there are more processing channels than amp channels, this will be the case. You give up balanced XLR connectors, but does that really matter?

 

[Dave Upton]

How about the stepwise route? For instance I was planning on getting the Anthem 1140 for my new setup. It seems that the preamp outs from the receivers have actually improved enough that the AV receivers make good processors. In this way, you could add amps later if needed and then down the road get a new processor for new tech?

The Audioholics review of the new SR8015 from marantz showed that there was a cuttoff so that when using RCA outs there was no noise from it when turning up the volume, this was apparently not the case with the 8013. I'm assuming with these new designs where outputs are assignable and when there are more processing channels than amp channels, this will be the case. You give up balanced XLR connectors, but does that really matter?

Nothing wrong with the stepwise route at all. And Anthem receivers have some of the best amp sections out there. One of the few brands where separate are going to be only a moderate vs massive leap in performance.

XLR/Balanced gives you a cable arrangement where the conductors natively reject noise a bit better. This is good where you have EMI/RFI (think noisy devices, bad wall warts, running the cable near power wires, radios etc).

Inherently, XLR has a 6dB lower noise floor than unbalanced, so I always tell folks if you have the option of both, there is no reason to go unbalanced when you could go balanced.

 

[SmCaudata]

Nothing wrong with the stepwise route at all. And Anthem receivers have some of the best amp sections out there. One of the few brands where separate are going to be only a moderate vs massive leap in performance.

XLR/Balanced gives you a cable arrangement where the conductors natively reject noise a bit better. This is good where you have EMI/RFI (think noisy devices, bad wall warts, running the cable near power wires, radios etc).

Inherently, XLR has a 6dB lower noise floor than unbalanced, so I always tell folks if you have the option of both, there is no reason to go unbalanced when you could go balanced.

I won't have the cash outlay for some really nice amps at the beginning, but do you think the Outlaw 7-channel and 5-channel amps are pretty good? If I go 7.2.4 out the gate I would need 11 channels of power. I can get an outlaw 7 and 5 along with the AVM70 for about $900 more than the 1140. Wondering if that is a good $900 spent...

 

[Dave Upton]

I won't have the cash outlay for some really nice amps at the beginning, but do you think the Outlaw 7-channel and 5-channel amps are pretty good? If I go 7.2.4 out the gate I would need 11 channels of power. I can get an outlaw 7 and 5 along with the AVM70 for about $900 more than the 1140. Wondering if that is a good $900 spent...

I actually posted about this in another thread here, but my short answer is no, I would avoid Outlaw. Their recent customer service and quality track record has left something to be desired. @John Dirk can likely add his own recent story on that topic.

 

[SmCaudata]

I actually posted about this in another thread here, but my short answer is no, I would avoid Outlaw. Their recent customer service and quality track record has left something to be desired. @John Dirk can likely add his own recent story on that topic.

Thanks for that insight. Maybe I'll save some more $$ for the MP monolith 11 channel. Power output looks great with more power for the front 3.