SPL targets for speaker design

[gedlee]

There has been a lot of discussion bantered about on what the actual SPL requirements for a loudspeaker system design are. I recently read a book "Sound Systems: Design and Optimization" by Bob McCarthy. In it he has a table of SPL values (figure 1.14). Since his numbers are completely consistant with what I have been saying, I thought that I would quote them here. This makes two highly credible references for design goals in terms of SPL.

These are listening levels at the seating position and all numbers are dB SPL with no weighting.

High Level Music: 103 - 112 dB with peaks to 115 - 124 dB
Medium Level Music: 91 - 100 dB with peaks to 103 - 112 dB
Low Level Music: 79 - 88 dB with peaks to 91 - 100 dB

Now if these are at the seating position then typically we would want to add 3-6 dB for the 1 meter levels, but this, of course, depends on the room.

Clearly to design a system where one wants to be able to handle High Level Music without major overloads the design target must be 125 - 130 dB at 1 meter. A speaker like this would never overload under any conditions even in a fairly large home room or home theater.

A 90 dB 1 watt 1 m speaker (a common small two-way) would need 10,000 watts to achieve this. A 100 dB 1 watt 1 m speaker (about the limit of design) would still need 1000 watts. A 100 watt amp is going to be clipping for the 100 dB speaker for some of the peaks when listening to High Level Music (which may be tolerable, based on my experince it would be). The 90 dB speaker will clip virtually all of the peaks on even Medium Level Music (based on my experience this would sound pretty bad.)

I suspect that these numbers are much higher than what most people suspect, but are completely consistant with my own opinions, experiences and observations. These are the numbers that I design to - and achieve. Others may target the Low Level or Medium Level, but clearly they will not be capable of achieving "High Level Music" or work in larger rooms without serious overload quality degradations or failure.

[badman]

100dB peaks would be called 'loud' by most people (not in here though). 110 dB peaks I think would be called 'high level' by most people in here.

I think the 'requirements' get skewed because max SPL isn't so necessary to achieve, but high SPL speakers tend to have some advantage at more modest reproduction levels- in other words, the design of such speakers has some features that lead to both high max SPL AND dynamic production at more reasonable levels.

This is all in the context of home music reproduction of course. I tend to like speakers that have a ton of headroom but I listen at pretty modest levels most of the time. I find that these types of speakers are able to maintain an expanded dynamic envelope at low volume pretty often.

A good counterexample would be heavy, high damping cone speakers- people tend to need the 'hifi' 4 way behemoth towers to get cranked to enjoy proper reproduction dynamics, but a similar sized driver complement with pro style (high SPL, high Qms, monster motors) tends to retain a more dynamic sound at lower levels.

So IMO, the high SPL requirement has more to do with the coincidence of the features needed to meet this with those needed to achieve good low-level dynamics.

[x. onasis]

Design considerations aside, a check with a meter at listening positon suggests to me music volume levels in the 70's dB is loud enough to make most speakers "sing."

In the 80's dB, it's loud enough to make one shout to be understood just a few feet away- and in the 90's you'll likely be experiencing temporary threshold shift (TTS), in seconds.

Listening to music for extended periods at higher levels will cause permanent hearing loss. Be warned, OSHA suggests that with 20 years of loudness levels at 70dB your likelihood of permanent (Rated at -25dB) hearing loss is about 15%. At 95 dB it 35% and at 100dB it's a whopping 70%!!

I do wonder about that "singing" thing. Some speakers do low volumes really well, some have to be turned up to a certain level to reach their "sweet spot." Could it be my hearing loss?

[gedlee]

Originally posted by x. onasis
Design considerations aside, a check with a meter at listening positon suggests to me music volume levels in the 70's dB is loud enough to make most speakers "sing."

In the 80's dB, it's loud enough to make one shout to be understood just a few feet away- and in the 90's you'll likely be experiencing temporary threshold shift (TTS), in seconds.

Listening to music for extended periods at higher levels will cause permanent hearing loss. Be warned, OSHA suggests that with 20 years of loudness levels at 70dB your likelihood of permanent (Rated at -25dB) hearing loss is about 15%. At 95 dB it 35% and at 100dB it's a whopping 70%!!

I do wonder about that "singing" thing. Some speakers do low volumes really well, some have to be turned up to a certain level to reach their "sweet spot." Could it be my hearing loss?

You are dramtically mistating reality.

No hearing loss occurs at levels below about 80-85 dB - ever! The OSHA standards allow 100 dB for two hours without protection!! My wife is an audiologist, I live with this stuff and your numbers are incorrect. I stand by the numbers that I posted above. They are correct.

20 years at 100 dB is absurd. Damage is a time AND level effect and your times are excessive. NO one spends 20 years at 100 dB, so where did those numbers even come from. Ridiculous.

[kstrain]

just in case there could, perhaps, be some argument* it might be useful to say what "peak" means in this context.

I guess it is just the instantaneous (and, as you said, unweighted) maximum. In that case, with most music, it bears little connection to any issue of exposure or safety.

*though personally I don't see why: I'm listening to very modest 90db rms and 100~103 dB peaks at the moment and it certainly fits the description of medium level.

(I think high level would make my ears ring a little though, after ~ an hour.)

Ken

[ShinOBIWAN]

http://www.osha.gov/pls/oshaweb/owad...ARDS&p_id=9735

[Salas]

Originally posted by gedlee
I suspect that these numbers are much higher than what most people suspect, but are completely consistant with my own opinions, experiences and observations. These are the numbers that I design to - and achieve. Others may target the Low Level or Medium Level, but clearly they will not be capable of achieving "High Level Music" or work in larger rooms without serious overload quality degradations or failure.

These numbers are pretty real in pro reinforcement practice. I.e. loud clubs and live events. I have lived that reality as a live sound engineer and general applications pro installer. There, the audience yelling and activity, keeps the noise threshold very high, and the anticipation for fun preconditions people for peak levels they will not normally tolerate for listening to recordings at home.
I would subtract roughly10dBs out of each number mentioned in your post for home listening.

[gedlee]

Originally posted by salas



These numbers are pretty real in pro reinforcement practice. I.e. loud clubs and live events. I have lived that reality as a live sound engineer and general applications pro installer. There, the audience yelling and activity, keeps the noise threshold very high, and the anticipation for fun preconditions people for peak levels they will not normally tolerate for listening to recordings at home.
I would subtract roughly10dBs out of each number mentioned in your post for home listening.

All of these later posts are reasonable and if you want to subtract 10 dB for home listening thats fine.

Thanks for the OSHA posting. Note that those are dB(A) and "Slow" meaning more like 110 dB(C) (a guess) and peaks to 120 dB are allowed by OHSA for 2 hours. Two hours at that level would deflate me too.

[graaf]

Originally posted by gedlee
There has been a lot of discussion bantered about on what the actual SPL requirements for a loudspeaker system design are. I recently read a book "Sound Systems: Design and Optimization" by Bob McCarthy. In it he has a table of SPL values (figure 1.14). Since his numbers are completely consistant with what I have been saying, I thought that I would quote them here. This makes two highly credible references for design goals in terms of SPL.

These are listening levels at the seating position and all numbers are dB SPL with no weighting.

High Level Music: 103 - 112 dB with peaks to 115 - 124 dB
Medium Level Music: 91 - 100 dB with peaks to 103 - 112 dB
Low Level Music: 79 - 88 dB with peaks to 91 - 100 dB

Now if these are at the seating position then typically we would want to add 3-6 dB for the 1 meter levels, but this, of course, depends on the room.

(...)

in larger rooms without serious overload quality degradations or failure.

"a room"? "a larger room"?


how much larger?

aren't "sound systems" from McCarthy's book a "Public Address sound systems"?
from Amazon descritpion:

definitive guide to sound reinforcement design and optimization
The book follows the audio signal path from the mix console to the audience and provides comprehensive information

an audience and a PA system in a living room ?

[graaf]

Originally posted by salas


There, the audience yelling and activity, keeps the noise threshold very high

noise threshold is very important because human hearing is sensitive to relative SPL
so the lower the ambient noise the less dB and Watts is needed