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#338841 - 02/16/11 11:23 PM Re: How much power is needed to play M80s at reference [Re: solarrdadd]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10399
Loc: Calgary, Alberta
You might actually want to use the in room response of 95db for your calculations, it makes quite the difference. I suspect your Yamaha would be sufficient on it's own as I can hit 105 db peaks easily with my Denon 3808 in my ~4000cf room and I am sitting 12 ft away from my M80s with a single PB13 ultra.
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#338846 - 02/16/11 11:31 PM Re: How much power is needed to play M80s at reference [Re: jakewash]
SBrown Offline
aficionado

Registered: 11/16/10
Posts: 813
Loc: Victoria,BC
I know my M80's actually shut off my Sherwood at higher volumes playing BD tunes , yet to test the Onkyo.
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#338959 - 02/17/11 06:05 PM Re: How much power is needed to play M80s at reference [Re: JohnK]
DanLW Offline
frequent flier

Registered: 07/30/10
Posts: 11
Wow, thanks for all the replies! I would have responded much earlier, but my internet was down for most of the day. So this will be a long reply.

Originally Posted By: JohnK
Dan, welcome. First, forget about the Crown calculator. It has no relevance to use in reflective home listening rooms and grossly overestimates the power necessary for such use.


I double-checked, and it seems to be working correctly. If I put in 91db as the sensitivity, 91db as the desired listening level, and 1 meter as the listening distance, I get 2 watts. (3db headroom) This is correct. If I make the distance 2 meters, I get 8 watts. This falls in line with the rule that with each doubling of distance, 6db is lost. (I know, you have 3db per doubling... I'll get to that) So at 4 meters, we would be 12db down. So, we should have 32 watts, which is what the calculator gives me. At 3 meters, we should be 9db down, and require 16 watts. The calculator gives me 18 watts, but I suspect that is because they are using a bit more of a complex formula.

So, 91db at 1 watt at 1 meter. Move 3 meters away, so approx. 9db down. 82db. I want 105db, which is 23db higher. So, 1*10*10*2=200. Plus 3db for headroom, 400 watts.

But why am I using 6db considering...

Originally Posted By: JohnK

I calculate as follows: use 90dB as the 1 watt sensitivity for the M80 at 1 meter. 100 watts would result in a 110dB output at that distance. Since, as Dr. Toole and others have reported, sound level in a typical home listening room falls off(taking into account both direct sound and room reflections)about 3dB per doubling of distance, at a 10' listening location the 100 watts are used for about a 105dB listening level on brief split-second peaks. Typical receivers rated anywhere in the 100 watt area are ample. Relax and enjoy.


I'm sure that is correct, for the typical home listening room. The typical home listening room is a completely untreated acoustic "hall of mirrors". If my room was typical, it would have the .45 second RT60 I measured before I started putting my treatments up. But now that I have done the front wall (the Air Force deployed me to Afghanistan before I could do the sides, back, and bass trapping) my room's RT60 is now .25 seconds in the 250-10KHz range. I know that sounds low, but from some of the charts I've seen, I should be shooting more for .21 seconds.

So, my room is probably going to have a greater than 3db attenuation per doubling of distance. If I were home, I'd whip out my SPL meter, play pink noise out of a speaker, and I'd have an actual measurement for you. Perhaps that is what I'll have to do when I get home. That way I'll have a better idea of exactly how much amplification I need.

And here's some antecdotal observations. We (me and my wife) can now listen to movies with the volume turned up louder than before. I'm fairly certain this is because of the reduced reflections (i.e. noise) in the room. I'm probably butchering the term signal to noise ratio, but basically with less reflections, the room's signal to noise ratio is better, so we can play louder without the "noise" being as loud.

Originally Posted By: Dr.House
The Behringer EP2500 will do that into 4 ohms and then some. It will also provide about 1000 watts into 2 ohms (verified by 3rd party testing). These would be the most cost effective solution and offer better performance than the Emotiva but you would also have fan noise to deal with which will be an issue if you do any low level listening smile or have to mod the fan on the unit(s).


I'll look into the Behringers, but this is the first I've heard of quality issues with the Emotiva amplifiers. (their signal processors are a different story)

I found something disturbing on Behringer's EP2500 page, however...

Originally Posted By: Behringer
Selectable low-frequency filters (30 Hz or 50 Hz) remove distracting infra-sound frequencies


Wha? GAA! EVIL! EEEEEVIL! THE POWER OF CHRIST COMPELS YOU!

Sorry... seeing as I plan to get two PB-13 Ultras, and plan to run them in sealed mode, that statement... I could go on quite a rant about that.

Of course, I know I wouldnt be routing the LFE channel through the external amp, but just the thought that an audio company considers low frequencies distracting... I need to wash my eyes after reading that.

Anyhow, their price doesn't seem bad. I'd definitely fan mod them, though.

Originally Posted By: solarrdadd
my HT room is 15 x 16 x 8 and the 16 side opens via a 4' passage all the way to the other end of the house which is 30'. i have an emotiva XPA-5 powering my front 3 which includes a pair of M80v3's and a VP180v3 center.

if i have my volume about 1/4 of the way up while watching a blu-ray movie, lossless (action movie) it's loud but good, just where it's tolerable and not ear damaging. if i turn it up to 1/2 the way it's almost deafining and i'd have to go all the way back to the other end of the house,at the 30' wall to stand it. 3/4 of the way up there is no way i can stand it even at the 30' wall, it actually hurts my ears, head, it's just too damn loud...


Where is reference level on your amplifier? I'm guessing it would be somewhere at the 1/2 way point. At least, in my calculations, 105db would be somewhere around the half power point. Of course, that's 105db peaks. The whole soundtrack shouldn't be at that level. I'd be interested to know what SPL white noise calibrated to -30db plays at for those settings.

Originally Posted By: jakewash
You might actually want to use the in room response of 95db for your calculations, it makes quite the difference. I suspect your Yamaha would be sufficient on it's own as I can hit 105 db peaks easily with my Denon 3808 in my ~4000cf room and I am sitting 12 ft away from my M80s with a single PB13 ultra.


Again, I wish I was at home so I could check to see where my room stands. I'll have to experament with my current speakers and see how they measure in relation to their rated sensitivity. Hmmm. But I'm not sure how to assure I am sending exactly 1 watt to them without buying expensive test equipment...

So, to conclude, looks like I'm going to have to do some measurements in my room to see which set of calculations to use in determining how much power I will need. It's likely going to be somewhere between 6db per doubling and 3db per doubling of distance, since my room is not anechoic, nor is it a typical listening space. Well, I have 5 1/2 more months before I get back home. So I'll have plenty of time to get more educated.

In the meantime, for those of you with well treated theater rooms, I would be curious what db loss you measure per doubling of distance. Or perhaps somebody already has such information?

Thank you!

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#338961 - 02/17/11 06:23 PM Re: How much power is needed to play M80s at reference [Re: DanLW]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13339
Loc: Iowa
The dB loss you measure per doubling distance would be the same in any situation. Proper treatments will assist in a flatter frequency response within your room (bass traps, panels) however most people with properly furnished rooms will be fine. You will come to a point where you will rather just enjoy the system versus worrying about 1-2dB's which you can't perceive anyway.
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M22-OWM22-VP100-Denon2805
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#338963 - 02/17/11 06:34 PM Re: How much power is needed to play M80s at reference [Re: SirQuack]
DanLW Offline
frequent flier

Registered: 07/30/10
Posts: 11
Originally Posted By: sirquack
The dB loss you measure per doubling distance would be the same in any situation. Proper treatments will assist in a flatter frequency response within your room (bass traps, panels) however most people with properly furnished rooms will be fine. You will come to a point where you will rather just enjoy the system versus worrying about 1-2dB's which you can't perceive anyway.


The thing is, people on this site are saying 3db per doubling, and elsewhere it is 6db per doubling. At 3 meters, that can mean either 4.5db down or 9db down. 4.5dbs makes quite a difference, considering it can mean the difference between needing a 200W amp and a 500W amp.

Ah, another question I forgot to ask in the last post. How much headroom is generally recommended? Is 3db a good rule of thumb? If it is more like 1 or 2db of headroom, is that sufficient, or flirting with disaster? I mean, let's say I know I need 226W to get to 105. And I calibrate my system so that 0 on the volume knob is reference. Would getting a 250 or 300W amplifier be "safe", or should I really go for that 3db of headroom, and get a 500W amp?

I guess the real question is, how many movies have peaks above reference? Properly mastered movies should peak out at 105db... but it seems there is no shortage of movies with bad mastering...


Edited by DanLW (02/17/11 06:37 PM)

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#338964 - 02/17/11 06:39 PM Re: How much power is needed to play M80s at reference [Re: DanLW]
solarrdadd Offline
local

Registered: 05/04/10
Posts: 278
Loc: Alexandria, VA
Originally Posted By: DanLW
Wow, thanks for all the replies! I would have responded much earlier, but my internet was down for most of the day. So this will be a long reply.

Originally Posted By: JohnK
Dan, welcome. First, forget about the Crown calculator. It has no relevance to use in reflective home listening rooms and grossly overestimates the power necessary for such use.


I double-checked, and it seems to be working correctly. If I put in 91db as the sensitivity, 91db as the desired listening level, and 1 meter as the listening distance, I get 2 watts. (3db headroom) This is correct. If I make the distance 2 meters, I get 8 watts. This falls in line with the rule that with each doubling of distance, 6db is lost. (I know, you have 3db per doubling... I'll get to that) So at 4 meters, we would be 12db down. So, we should have 32 watts, which is what the calculator gives me. At 3 meters, we should be 9db down, and require 16 watts. The calculator gives me 18 watts, but I suspect that is because they are using a bit more of a complex formula.

So, 91db at 1 watt at 1 meter. Move 3 meters away, so approx. 9db down. 82db. I want 105db, which is 23db higher. So, 1*10*10*2=200. Plus 3db for headroom, 400 watts.

But why am I using 6db considering...

Originally Posted By: JohnK

I calculate as follows: use 90dB as the 1 watt sensitivity for the M80 at 1 meter. 100 watts would result in a 110dB output at that distance. Since, as Dr. Toole and others have reported, sound level in a typical home listening room falls off(taking into account both direct sound and room reflections)about 3dB per doubling of distance, at a 10' listening location the 100 watts are used for about a 105dB listening level on brief split-second peaks. Typical receivers rated anywhere in the 100 watt area are ample. Relax and enjoy.


I'm sure that is correct, for the typical home listening room. The typical home listening room is a completely untreated acoustic "hall of mirrors". If my room was typical, it would have the .45 second RT60 I measured before I started putting my treatments up. But now that I have done the front wall (the Air Force deployed me to Afghanistan before I could do the sides, back, and bass trapping) my room's RT60 is now .25 seconds in the 250-10KHz range. I know that sounds low, but from some of the charts I've seen, I should be shooting more for .21 seconds.

So, my room is probably going to have a greater than 3db attenuation per doubling of distance. If I were home, I'd whip out my SPL meter, play pink noise out of a speaker, and I'd have an actual measurement for you. Perhaps that is what I'll have to do when I get home. That way I'll have a better idea of exactly how much amplification I need.

And here's some antecdotal observations. We (me and my wife) can now listen to movies with the volume turned up louder than before. I'm fairly certain this is because of the reduced reflections (i.e. noise) in the room. I'm probably butchering the term signal to noise ratio, but basically with less reflections, the room's signal to noise ratio is better, so we can play louder without the "noise" being as loud.

Originally Posted By: Dr.House
The Behringer EP2500 will do that into 4 ohms and then some. It will also provide about 1000 watts into 2 ohms (verified by 3rd party testing). These would be the most cost effective solution and offer better performance than the Emotiva but you would also have fan noise to deal with which will be an issue if you do any low level listening smile or have to mod the fan on the unit(s).


I'll look into the Behringers, but this is the first I've heard of quality issues with the Emotiva amplifiers. (their signal processors are a different story)

I found something disturbing on Behringer's EP2500 page, however...

Originally Posted By: Behringer
Selectable low-frequency filters (30 Hz or 50 Hz) remove distracting infra-sound frequencies


Wha? GAA! EVIL! EEEEEVIL! THE POWER OF CHRIST COMPELS YOU!

Sorry... seeing as I plan to get two PB-13 Ultras, and plan to run them in sealed mode, that statement... I could go on quite a rant about that.

Of course, I know I wouldnt be routing the LFE channel through the external amp, but just the thought that an audio company considers low frequencies distracting... I need to wash my eyes after reading that.

Anyhow, their price doesn't seem bad. I'd definitely fan mod them, though.

Originally Posted By: solarrdadd
my HT room is 15 x 16 x 8 and the 16 side opens via a 4' passage all the way to the other end of the house which is 30'. i have an emotiva XPA-5 powering my front 3 which includes a pair of M80v3's and a VP180v3 center.

if i have my volume about 1/4 of the way up while watching a blu-ray movie, lossless (action movie) it's loud but good, just where it's tolerable and not ear damaging. if i turn it up to 1/2 the way it's almost deafining and i'd have to go all the way back to the other end of the house,at the 30' wall to stand it. 3/4 of the way up there is no way i can stand it even at the 30' wall, it actually hurts my ears, head, it's just too damn loud...


Where is reference level on your amplifier? I'm guessing it would be somewhere at the 1/2 way point. At least, in my calculations, 105db would be somewhere around the half power point. Of course, that's 105db peaks. The whole soundtrack shouldn't be at that level. I'd be interested to know what SPL white noise calibrated to -30db plays at for those settings.

Originally Posted By: jakewash
You might actually want to use the in room response of 95db for your calculations, it makes quite the difference. I suspect your Yamaha would be sufficient on it's own as I can hit 105 db peaks easily with my Denon 3808 in my ~4000cf room and I am sitting 12 ft away from my M80s with a single PB13 ultra.


Again, I wish I was at home so I could check to see where my room stands. I'll have to experament with my current speakers and see how they measure in relation to their rated sensitivity. Hmmm. But I'm not sure how to assure I am sending exactly 1 watt to them without buying expensive test equipment...

So, to conclude, looks like I'm going to have to do some measurements in my room to see which set of calculations to use in determining how much power I will need. It's likely going to be somewhere between 6db per doubling and 3db per doubling of distance, since my room is not anechoic, nor is it a typical listening space. Well, I have 5 1/2 more months before I get back home. So I'll have plenty of time to get more educated.

In the meantime, for those of you with well treated theater rooms, I would be curious what db loss you measure per doubling of distance. Or perhaps somebody already has such information?

Thank you!


Truth is i have no idea where reference level is with my amp. i don't get that deep into this stuff. i do know when something is too loud for me to enjoy myself! perhaps someone else with an emotiva XPA-5 amp and my pre-amp know at what point you hit reference level. when i watch the news on tv the volume is set at 40 absolute. when watching movies or sports the volume is between 50 to 60 absolute or -32db to -22db relative. the settings just listed are great/perfect for me/us watching movies and it never gets louder than mentioned or it's unbearable! on my preamp, to hit 0db, relative (which is 82 absolute) that's about at the half way point and it can go higher up to 100 absolute or +18.0db relative which are the max volumes and no, i never want to make a mistake and somehow hear that!
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OnkyoPR-SC5507P pre-amp
Emotiva XPA-5,UPA-2amps,
14 Speakers, All Axiom
Oppo 105D&93

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#338976 - 02/17/11 08:26 PM Re: How much power is needed to play M80s at reference [Re: solarrdadd]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10399
Loc: Calgary, Alberta
The point at which you hit reference level would be dependant on the output voltage of the pre/pro and that voltage varies between manufacturers and even models within the same company.

DanLW, I may hive missed this, but why are you even trying to achieve 'peak reference level 105db'? I know movies are mixed for peaks to reach 105db but that is also with normal noise in the 85 db range which is actually quite loud and not many people listen at this level in a home theater. I believe I listen to movies with normal range around 75-80db with peak levels around 95-100db.


Edited by jakewash (02/17/11 08:28 PM)
_________________________
Jason
-----------------
TTTHHHPPPPPTTTT!

My HT

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#338977 - 02/17/11 08:26 PM Re: How much power is needed to play M80s at reference [Re: jakewash]
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17789
Loc: NoVA
Pretty sure he said peak at 105.
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I am the Doctor, and THIS... is my SPOON!

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#338978 - 02/17/11 08:28 PM Re: How much power is needed to play M80s at reference [Re: Ken.C]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10399
Loc: Calgary, Alberta
You would be correct and that was what I meant, I have now corrected it.
_________________________
Jason
-----------------
TTTHHHPPPPPTTTT!

My HT

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#338984 - 02/17/11 09:24 PM Re: How much power is needed to play M80s at reference [Re: SirQuack]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16288
Loc: Leesburg, Virginia
Originally Posted By: sirquack
most people with properly furnished rooms will be fine

What, pray tell, is a properly finished room? What if I really like concrete furniture??
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