How much loudness is enough for HT?

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Just curious about how loud speakers should play in a home theater environment. I thnk the 5.1 encoding allows for 105dB for the main channels and 115dB for the LFE.

After calibrating my receiver I normally listen to movies at least -10dB and usually -20

Is that 105dB supposed to be at the listening position? If that's the case, can I get away by sizing my amps/speakers for 95dB at the listenin position?

Assuming a 10' distance would that mean the speaker itself needs to be ~100dB/1m? Would then the LFE need to be 110dB1/m?

Thanks!

P.S. My room is dedicated and will be acoustically treated to an RT60 of about .35, (pretty dead and absorptive), if that makes a difference.
 
Hi Phil,

How loud you want it is strictly up to you. I like it loud and am running a H/K 55 watts for L-C-R and 25 watts for the rears in a 5.1. I also run a powered woofer.

The speakers I use are about 90-92 dB sensitive (total driver count: 24) and the room is about 250 ft^2. I am about 12 feet from the mains. That is more than loud enough and there is no shortage of headroom. By the time we get to 100dB, it's scary loud. Here's the right front:
 

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Interesting question, one I've been podering for a bit as I have some large mains under construction and have been trying to figure out what sort of poweramps to use. For music, I'll use my tube jobs as they'll be loud enough (speakers are >100dB/W/m), but will use some SS for background and HT.

In my audio travels I've discovered I am conscious of dynamic effects and distortion, so I designed for a >120dB capability (with sufficient power) for the mains. I don't think it'll ever hit that even on peaks, but it's nice to know it'll be idling most of the time.

I'm also trying to work out specs for the design of the rears (FR, SPL etc) and power for them too.
 

GM

Member
Joined 2003
Greets!

DD/DTS reference is 85 dB/channel, 95 dB/LFE (assuming the other channels are nominally flat from 20-20 kHz) at the listening position with 20 dB dynamic headroom, hence the 105, 115 dB limits/listening position. If all mains/surround channels are set to 'small', then the LFE channel in theory must be able to handle ~122 dB/listening position peaks for 5.1, ~122.8 dB/6.1, ~123.5 dB/7.1.

This is too loud for most folks in a typical HT due mostly IMO to the fact that the typical speakers used (even many $$$ units) can't handle the SPLs at the vanishingly low distortion required for low listening fatigue, so tend to dial it back to suit the most sensitive viewers and/or to protect the speakers/whatever during high SPL effects scenes.

WRT loss over distance, SPL requirements will vary by frequency due to the speaker's directivity, placement and room gain, so no simple solution short of designing to the 6 dB/doubling of distance 'worst case' scenario.

GM
 
Cal,

If I calculate right your 55W will give about 107dB but being 4m away will knock that down to about 95. You'll be aided by reflections if your picture is any indication, (nice speakers by the way!). 95dB is indeed loud.

Brett,

Sounds like you're going the pro driver route. Awesome! I thought about it but really didn't want to deal with the large cabinets required.

In my limited knowledge, I think sound quality depends on the type of distortion. If I recall, clipping is very bad and quite noticable, while IM and THD are much less important. Somewhere I read that even 10% may not be that noticable but have no knowledge if that is correct or not. I'm sure it's personal preference like every thing else so like most things, 10% of the population will be super sensitive, 80% will be somewhat sensitive, and 10% will be tone deaf. :D

GM,

Thanks, that's kind of what I remember. I did forget that the fall off is 6dB, not 3dB. The good news is that most of time, movies are rather quiet.

The speakers I am designing should have wide directionality so I've got that going for me! :D I'll have low end room gain somewhat but since I'll have a lot of base trapping going on I won't know how much until I'm farther along and can measure it.

It would be great to have a spreadsheet that everyone could use to determing speaker requirements and therefore amp requirements. One would have to guestimate live room/dead room corrections, etc. but it could be a good ball park tool.

If I recalculate, I'll need about 116dB/126dB at the listening position. Knocking that down 10dB, will give me a reasonable 106dB/116dB Main/LFE to shoot for as a minimum considering my listening preferences.

One consequence for me is that it has eliminated the simpler gainclone amp designs since my speakers will not be terribly efficient.

Any thoughts on standards regarding distortion specs, rules of thumb, etc.?
 
Phil Olson said:
Brett,

Sounds like you're going the pro driver route. Awesome! I thought about it but really didn't want to deal with the large cabinets required.
Indeed. I don't use anything else these days, though I am contemplating a waveguided Fountek neo5, but that's as close as I can see me ever going to typical 'phile drivers again.

Phil Olson said:
In my limited knowledge, I think sound quality depends on the type of distortion. If I recall, clipping is very bad and quite noticable, while IM and THD are much less important. Somewhere I read that even 10% may not be that noticable but have no knowledge if that is correct or not. I'm sure it's personal preference like every thing else so like most things, 10% of the population will be super sensitive, 80% will be somewhat sensitive, and 10% will be tone deaf. :D
Yep, clipping of amps, or drivers over excursing is plainly audible to me. However dynamic compression and THD also annoy me, so I'm looking to build something with the efficiency alnd low distortion of horns, with fewer drawbacks.
Phil Olson said:
If I recalculate, I'll need about 116dB/126dB at the listening position. Knocking that down 10dB, will give me a reasonable 106dB/116dB Main/LFE to shoot for as a minimum considering my listening preferences.
Seems like a good target, but even with efficient speakers that needs a lot of power.

Phil Olson said:
One consequence for me is that it has eliminated the simpler gainclone amp designs since my speakers will not be terribly efficient.
Ditto. I'm looking at some of the class D and (I'm shocked to hear myself saying this) AB SS designs.

Phil Olson said:
Any thoughts on standards regarding distortion specs, rules of thumb, etc.?
I've been looking on the DD and DTS sites for specs, and also googling but can't seem to find anything definitive.
 
Cal,

I'm going to do a WMTMW or MTMWW for the same reason. My current Snell LCR's actually have two tweeters most likely to get the volume up at reasonable distortion.

Brett,

It's definitely more than a couple hundred watts but should be doable with the 49830 and multiple FET pairs. I probably could do a BPA-400/500 as well but the FETs seem easier.

If you find any specs on distortion please let me know. It seems most of the companies, including THX, are rather tight lipped about their specs.
 
Brett said:

Something tangible, thanks. Do you know of a link to detailed specs with distortion figures etc? Might as well aim for the standard.

Not AFAIK, folks pay a 'pretty penny' to become THX certified and try to earn a living off the knowledge, but if we look at a cinema's requirements we can 'backdoor' it close enough IMO and not surprisingly it boils down to having controlled directivity/~flat power response to suit the seating distance/layout in our acute hearing BW and sufficient dynamic headroom to keep distortion low just like for a multi-channel cinema, so for a typical HT some form of waveguide or CD horn is required/channel combined with 6 - 8 dB of dynamic headroom.

The room obviously is a big part of a sound system, expecially for a multi-channel one, so dialing in the desirable RT60 seems a 'no-brainer'. JBL's cinema design manual has a nomograph and if your room is < 1 k ft^3, then it ideally needs to be able to do double duty as a ~aneochoic chamber.

GM
 
GM said:
Not AFAIK, folks pay a 'pretty penny' to become THX certified and try to earn a living off the knowledge,
I thought as much, but I'd hoped you may have known if some info had snuck out and was posted somewhere.

GM said:
but if we look at a cinema's requirements we can 'backdoor' it close enough IMO and not surprisingly it boils down to having controlled directivity/~flat power response to suit the seating distance/layout in our acute hearing BW and sufficient dynamic headroom to keep distortion low just like for a multi-channel cinema, so for a typical HT some form of waveguide or CD horn is required/channel combined with 6 - 8 dB of dynamic headroom.
Sounds like what I'm working towards in most of the details. I'm basing a lot of my design ideas around Jack Bouska's speakers and the Drew Daniel's cinema design, with my own twists of course. Now if I could only get those 4 BMS 18N840 v2's I need.....
GM said:
The room obviously is a big part of a sound system, expecially for a multi-channel one, so dialing in the desirable RT60 seems a 'no-brainer'. JBL's cinema design manual has a nomograph and if your room is < 1 k ft^3, then it ideally needs to be able to do double duty as a ~aneochoic chamber.

GM
The room here isn't the best, but my porcelain library book for the last few weeks has been Alton Everest so I have several ideas about how to work around that.
Phil Olson said:
Can you post the link to the JBL document?
I'd like to see that too. I checked the Tech Library on jblpro.com and didn't see it, but it's 0230 and I shouldn't be awake now so I may have missed the obvious.
I logged on hoping the 'Do all amps sound the same' thread might act as a soporific.
 
Dr. Geddes and his wife did a study on home theaters and levels. I think they found that typically HT users were running at 120db c-weighted. So speakers needed to be capable of that.

Now what I don't know is whether that was at 1-meter or other. I am assuming that is on peaks. I also don't know if that is mains or LFE but it seemed to imply mains.
 
I wonder why it is that virtually every time I leave it for someone to do a little 'due diligence' (Googling) I seem to be the only successful one?

http://www.google.com/search?hl=en&rls=org.&q=jbl+cinema+design+manual&btnG=Search

Or in this case, using JBL's search feature: http://www.google.com/custom?q=cine...w.jblproservice.com&sitesearch=www.jblpro.com

Pg. 11, fig. 11

FWIW, being a chronic insomniac I'm always on the lookout for a web based 'soporific' in the wee hours and this one knocked me right out: http://www.diyaudio.com/forums/showthread.php?s=&threadid=120101

GM
 
Hmm, I can't help but wonder whose HTs the good doctors measured since few consumer HT speakers are capable of these implied SPLs at low distortion. It's a well proven fact though that as distortion levels drop, folks will tend to listen at higher average/peak SPLs........

For instance, back when I had a pretty much 'full tilt boogie' wide BW stereo system most folks would be intimidated by their sheer size and its high SPL/my apparent 'deafness' connotation, so I quickly learned to always let them set the volume and at some point they would turn to me to comment on something only to find it was so loud they couldn't hear themselves. Indeed, I was initially surprised that young women tended to set it higher than I was comfortable with and why I was stunned to find that WAF/SAF/SWMBO/whatever held such sway WRT speaker size/low in-room sound level when I joined the audio 'net in '96.

GM
 
GM said:
I wonder why it is that virtually every time I leave it for someone to do a little 'due diligence' (Googling) I seem to be the only successful one?
LOL. Thanks. I did look before, honest! When I got up again after a 15 min 'nap' I scrolled down the page I was on before and found it. I'm surprised I didn't have it either as I seem to have downloaded the entire site over the years as there's a wealth of great info on it.

GM said:
FWIW, being a chronic insomniac I'm always on the lookout for a web based 'soporific' in the wee hours and this one knocked me right out: http://www.diyaudio.com/forums/showthread.php?s=&threadid=120101

GM
That on has had me amused too. Some good points in both threads, but a poor S/N ratio.
I get to go on a field trip for work today so I know as soon as I'm on the seat in the (special) bus, I'll be asleep.
GM said:
Hmm, I can't help but wonder whose HTs the good doctors measured since few consumer HT speakers are capable of these implied SPLs at low distortion. It's a well proven fact though that as distortion levels drop, folks will tend to listen at higher average/peak SPLs........
True. Most I've ever experienced do 'modest' OK, then go to hell as the levels go up a small amount

GM said:
For instance, back when I had a pretty much 'full tilt boogie' wide BW stereo system most folks would be intimidated by their sheer size and its high SPL/my apparent 'deafness' connotation, so I quickly learned to always let them set the volume and at some point they would turn to me to comment on something only to find it was so loud they couldn't hear themselves. Indeed, I was initially surprised that young women tended to set it higher than I was comfortable with and why I was stunned to find that WAF/SAF/SWMBO/whatever held such sway WRT speaker size/low in-room sound level when I joined the audio 'net in '96.

GM
When I had my big horn system (corner loaded LABsubs, hyppex midbass and trax's from there up) with lots of power, I had a guy come over wanting to see what my 'crazy' system was about. He set the level and after watching most of a BUS (blow up stuff) action movie, I pulled out the ratshack SPL meter and it was banging the stop constantly on the top range. Both our ears rang for ages. I'm quite sensitive to distortion and dynamic compression after having that rig. Typical phile 6" 2ways sound like headphones now, hence the desire for a large high capacity ssytem again.

The SPL meter mentioned before was kept in the rmote box on the coffee table as I found out how easy it was to listen very loud with that system and checked myself with it often. It also kept the neighbours happy most of the time as I'd come to an agreement with them about day and night SPLs at the property boundaries, then measured inside the house, and tried never to exceed them.

I'm looking for something with that sort of capability now, but DR not horn except >1kHz or so. It's gonna be big and full of pro drivers. I seldom do loud now, but the lack of compression and the ability to sound basically the same at low and very high levels makes it very easy to relax and listen/watch, at least for me.

Lots of reading to do tonight.
 
GM.

Thanks for the link! My brain has been fried lately so I wasn't even sure what to search for.

That 120dB must be peak LFE at 1m unless they limited their sample to pro stuff. Even most 'commercial' subs will have trouble putting out that much. The one's I'm building run out of steam at 118dB/1m unless they are overdriven a bit.

Moreover, from ancedotal evedence, most people listen about 10 dB below reference so something doesn't smell right with that data.

I think the best test of speaker transparency, subjectively speaking, is whether it can fool you or not. Perhaps I'm getting too old but my decade old Snell LCR's do this on a regular basis.

I remember during one movie I heard some scratching and growling in the corner of the theater and thought a cougar may have snuck in an open door or something. I paniced enough that I went turn on the lights and grab my 45. Of course when I hit the lights there was nothing there. The wife and I both had a laugh over that.

Doorbells, door knocks, phones and voices are other things that make me head for the lights. The funny thing is that we don't even have a doorbell! :eek:
 
Phil Olson said:

Thanks for the link!

Even most 'commercial' subs will have trouble putting out that much.

Moreover, from ancedotal evedence, most people listen about 10 dB below reference so something doesn't smell right with that data.

.......but my decade old Snell LCR's..........

Doorbells.........The funny thing is that we don't even have a doorbell!

You're welcome!

Yep, few consumer speakers or subs can do DD/DTS reference, even some that claim such.

Yeah, again, folks tend to set the volume based on audible distortion, so with most speaker systems it's lower than reference.

Right, Snell is one of the few brands worthy of recommendation.

Yeah, my stereo corner loaded horns do the surround sound trick on well recorded soundtracks too even though horns can't image and corners destroy a speaker's imaging/sound-staging, or so the 'audio ignorati' claim.

GM
 
GM said:
Yeah, my stereo corner loaded horns do the surround sound trick on well recorded soundtracks too even though horns can't image and corners destroy a speaker's imaging/sound-staging, or so the 'audio ignorati' claim.

GM
Before I built my big horns, I had some KHorns with ALK xovers. These were the speakers my poodle consistently went looking for the source of sounds with, usually movement noises in movies. He's rarely done it with others, but to nowhere near the consistency of the KHorns.
 
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