I've been reading up on the general opinion concerning what SPL levels one should design for.
There is however one aspect that confuses me somewhat.
For argument sake let's assume a 90dB average SPL. (I think this should be loud enough for most people?)
Add 30dB max for peaks and we get max 120dB peak SPL.
At what frequencies should you expect the peak SPL?
Should one design the bass for 120dB but the midrange could probably get away with 100-105dB?
What's the thinking regarding max SPL vs frequency?
There is however one aspect that confuses me somewhat.
For argument sake let's assume a 90dB average SPL. (I think this should be loud enough for most people?)
Add 30dB max for peaks and we get max 120dB peak SPL.
At what frequencies should you expect the peak SPL?
Should one design the bass for 120dB but the midrange could probably get away with 100-105dB?
What's the thinking regarding max SPL vs frequency?
What!? Are you talking about speaker sensitivity, such as 90dB/w/m?
If your speaker is 90dB but your amp is 5W, it will never be as loud as 200W amp with 80dB speaker. Loudness depends on distance and voltage applied to the speaker (or watt)
When speaker response is made flat, it means it is independent of frequency (in the intended audio band).
120dB/w/m for bass? With crossover? That is rare. We pad down tweeter because woofers in general do not have comparable sensitivity.
If your speaker is 90dB but your amp is 5W, it will never be as loud as 200W amp with 80dB speaker. Loudness depends on distance and voltage applied to the speaker (or watt)
When speaker response is made flat, it means it is independent of frequency (in the intended audio band).
120dB/w/m for bass? With crossover? That is rare. We pad down tweeter because woofers in general do not have comparable sensitivity.
You're correct, but with a 90dB sensitivity speaker, you would need 16 watts to hit 103 dB, while one with 80dB sensitivity would require 240 watts to reach the same 103dB SPL.
FWIW: Most people don't have a real appreciation of how loud even a 90 dB spl actually is.
Best Regards,
TerryO
Absolutely true, although I would have included the word "permanent" to the above.
Best Regards,
TerryO
important questions
all answers can be found here: http://www.diyaudio.com/forums/multi-way/121893-spl-targets-speaker-design.html
have You read that?
I'm working through that thread as I'm writing this. 
It would appear my question was a little vague.
Naturally the sensitivity will be the same for both the bass and the mid/high.
I'm talking about the frequency distribution of music. Will the mid-range have to play as loud as the woofer or is the bass generally louder in the recordings? I'm talking about the peak SPL here.
Does the mid-range and treble have as high SPL peaks as the bass?
Acording to the Fletcher/Munson curves we will percieve mid-range as louder compared to the bass given the same SPL.
What are the actual requirements here?
It would appear my question was a little vague.
Naturally the sensitivity will be the same for both the bass and the mid/high.
I'm talking about the frequency distribution of music. Will the mid-range have to play as loud as the woofer or is the bass generally louder in the recordings? I'm talking about the peak SPL here.
Does the mid-range and treble have as high SPL peaks as the bass?
Acording to the Fletcher/Munson curves we will percieve mid-range as louder compared to the bass given the same SPL.
What are the actual requirements here?
I'm working through that thread as I'm writing this.
It would appear my question was a little vague.
Naturally the sensitivity will be the same for both the bass and the mid/high.
I'm talking about the frequency distribution of music. Will the mid-range have to play as loud as the woofer or is the bass generally louder in the recordings? I'm talking about the peak SPL here.
Does the mid-range and treble have as high SPL peaks as the bass?
Acording to the Fletcher/Munson curves we will percieve mid-range as louder compared to the bass given the same SPL.
What are the actual requirements here?
Markus,
Your first statement is correct for any well designed speaker.
If the sensitivity is the same then they will play just as loud. The recording engineer has already determined the balance that's on the recording.
The Fletcher-Munson curve is, and you mentioned it above, how "we" perceive the balance at different SPL levels. Unless you only listen at a certain, predetermined average SPL level, it's not a good idea to design around the F-M parameters, as it would only have an octave to octave balance at a certain setting. Recordings don't come with a prescribed average SPL level so I can't imagine how it could ever sound right. It would be like designing a speaker that could only play one song on a recording well, and that would only be at certain level.
Best Regards,
TerryO
Acording to the Fletcher/Munson curves we will percieve mid-range as louder compared to the bass given the same SPL.
Yes but those curves are embedded in the records by the guys who make the records because they make the records using ears that follow those curves, so ... don't worry about that!
Yes but those curves are embedded in the records by the guys who make the records because they make the records using ears that follow those curves, so ... don't worry about that!
Well it depends on several things probably the most important is what are your anticipated listening levels going to be and what type of music do you listen too. If you want anything approaching realistic peak levels you may want to up your speaker efficiency above 90db.
The main issue is most speakers are on the wrong side of the power curve. You really want to start out with a system close to 100db @ 1 watt 1 meter. The 1 meter number is one thing but remember you need to design for your desired SPL at your listening position which is dependent on distance. It's very obvious when you work the numbers out that once you need over 100 watts to get to your SPL goal the power requirements simply get out of hand. 3db is 200 6db is 400 and 10db is 1Kwatt. You are much better off starting on the higher sensitivity side of the curve.
My average listening level is in the mid 80's but my speakers are set-up to reach over 115db peaks at my listening position. That's through their entire bandwidth from about 25Hz and up. It all depends on what you want.
Rob
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Well, imo recording companies are free to design the mix the way they want to meet market demand. Fans of some music genre may like bass a lot, and their majority of system is a boombox with critical 100Hz frequency.
It's all about trade-off. Many high-end speakers are noted to sound bad with bad recordings.
It is common to design a (cheap) bookshelf with tilted response before bass roll-off (high Q). Or to tailor the response such that they are going down with frequency (padding down tweeter).
But the most high-end owners seem to prefer a straight wire. May be because once you get a flat response down to 30Hz, you don't need any artificial compensation. And because loud is good if it is clean, meaning that if there is no distortion, there is nothing wrong with midrange being at the same SPL or even more (midrange/tweeter distortion is less acceptable than bass distortion)
For that small a room I'd say it's fine, especially if it's on a desktop and you're sitting at the desk.
Your spl/watts figures are correct.
Best Regards,
TerryO
My room is 11.5x18' and the critical question is as always how loud will I play?
By your standards I doubt it'll be considered especially loud. I live in an appartement and I can't play too loud since I don't want to disturb the neighbours.
I should just borrow a SPL meter and that would pretty much be the end of it?
My worries are that I'll be using a "full-range" driver in a two-way combo and it might not be able to handle the peak SPL?
105dB will probably be very close to the limit for this project. (Physical excursion limit)
With music being compressed the way it is today I figure I'll be fine, however there are some material out there with a larger dynamic range than 20dB crest and that might prove too much.
By your standards I doubt it'll be considered especially loud. I live in an appartement and I can't play too loud since I don't want to disturb the neighbours.
I should just borrow a SPL meter and that would pretty much be the end of it?
My worries are that I'll be using a "full-range" driver in a two-way combo and it might not be able to handle the peak SPL?
105dB will probably be very close to the limit for this project. (Physical excursion limit)
With music being compressed the way it is today I figure I'll be fine, however there are some material out there with a larger dynamic range than 20dB crest and that might prove too much.
It's going to be a panel X'ed somewhere in the 250-350Hz area and I havn't built it yet so I can only estimate the figures.
105dB is estimated at listening position. (2.4m)
Being really conservative I could say 100dB but than again being optimistic I could just as well say 110dB. (I haven't ran the numbers for max excursion, just using a rough estimate at the moment.)
I'm not really sure why a subwoofer would be relevant? Building the LF unit isn't the dealbreaker? It'll be the panel setting the max peak spl. I can do whatever I want for the LF part?
I'll be shooting for a 90dB/1W/1m sensitivity with the panel but really, if it turns out to be lower I'll just use a bigger amp. The woofers sensitivity will probably be higher but EQ'd to match the panel. Mixing point source with line source makes it pretty much a necessity. I'll be bi-amping it...
Atm my monoblocks are rated 200Wrms but I'll be building new amps to match the speakers as soon as I have some irl measurements to go with.
A subwoofer is definately an option I'm considering.
105dB is estimated at listening position. (2.4m)
Being really conservative I could say 100dB but than again being optimistic I could just as well say 110dB. (I haven't ran the numbers for max excursion, just using a rough estimate at the moment.)
I'm not really sure why a subwoofer would be relevant? Building the LF unit isn't the dealbreaker? It'll be the panel setting the max peak spl. I can do whatever I want for the LF part?
I'll be shooting for a 90dB/1W/1m sensitivity with the panel but really, if it turns out to be lower I'll just use a bigger amp. The woofers sensitivity will probably be higher but EQ'd to match the panel. Mixing point source with line source makes it pretty much a necessity. I'll be bi-amping it...
Atm my monoblocks are rated 200Wrms but I'll be building new amps to match the speakers as soon as I have some irl measurements to go with.
A subwoofer is definately an option I'm considering.
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