SPL formula?

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Poormanq45

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Posted: January 01, 2005 at 1:17 PM / IP Logged

Well, I thought that formula may apply to our discussion. I havn't yet equated it out yet.

Well, what is the best formula for calculating SPL right now? Is it still the basic 3Db increase requires 2x Power? Or is there a little bit more accurate formula out there?

I'm curious, do you think it is even possible to make a formula to calculate SPL for all drivers? I would assume that it must take into consideration alot of variables, including Enclosure size, Driver cone material, The resonance of the driver, and what else?

stevdart

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Posted: January 01, 2005 at 1:31 PM / IP Logged

"...I'm curious, do you think it is even possible to make a formula to calculate SPL for all drivers? I would assume that it must take into consideration alot of variables, including Enclosure size, Driver cone material, The resonance of the driver,..."
Uh, should we just flip back to page one at this point??

kfr01

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Joined: April 30, 2003

Posted: January 01, 2005 at 5:24 PM / IP Logged

Correct you are, Stevdart. Poormanq, start again at page 1.

Remember the difference we pointed out between excursion limited maximum SPL for a given frequency... (the linkwitz sheet seems to be the best for this)

and SPL NOT LIMITED by excursion. If xmax isn't limiting the movement of the driver, it is a non-issue, and yes, you go back to the doubling of amplifier power = 3db rise.

Of course all of this is kinda moot with the help of modeling tools that do all the math for you for specific enclosures... So, learn to use a tool like WinISD for all your driver purchase decisions and you're good to go.

I think this topic is probably dead. Anyway, I won't be able to participate - I just got married on New Years Eve and will now be taking a week in Jamaica at an all-inclusive. Needless to say, I will not be posting to the board. ;-)

New Project: 2003 Pathfinder

stevdart

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Posted: January 01, 2005 at 7:26 PM / IP Logged

Hey kfr01, you and your wife have a good time in Jamaica! My wife and I did an all-inclusive there, stayed at the Wyndam Rose, and had the time of our lives. Red Stripe beer and Blue Mountain coffee, each some of the world's finest...not to mention other stuff I won't mention....;) Tip: take a suitcase of toilet paper and shampoo (the regular big bottles, not the hotel freebies...). BIG bargaining and purchasing power with those items on the local economy. Better even than US dollars.

Poormanq45

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Joined: October 27, 2004

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Posted: January 01, 2005 at 9:34 PM / IP Logged

So then, if WinISD is able to accurately "predict" the spl for drivers then there must be a formula for doing this.

I don't really like just imputing some numbers into a program and then having it "spit-out" an answer for me. I like know how the answer came to be. Does that make sense?

haemphyst

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Posted: January 02, 2005 at 12:43 AM / IP Logged

The answers are derived from the OTHER parameters of the driver. THEY DONT GIVE A DAMN ABOUT THE EXCURSION CAPABILITIES OR NON-CAPABILITIES OF THE DRIVER! Forget Xmax - it does NOTHING for the formula... Just forget it!

Also, there is NO program that will accurately predict the maximum output of a driver, once that system ends up in a close boundary area - read: living room, theater, car trunk, etc. The results are derived from X driver with Y parameters in Z enclosure, true, but it is figured in a virtual reality anechoic chamber. YOU CAN'T GET THERE FROM HERE! Oh, and one more thing - FORGET XMAX - it does NOTHING for the formula!

BTW, have fun in Jamaica!

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Poormanq45

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Location: United States

Posted: January 02, 2005 at 5:36 PM / IP Logged

Ok, I've forgotten about maximum excursion.

So, if WinISD does not actually provide us with any information, then why do most of the "senior" members recommend it?

Also, [quote]"Also, there is NO program that will accurately predict the maximum output of a driver, once that system ends up in a close boundary area - read: living room, theater, car trunk, etc."[/quote]

So, by this statement you yourself are saying that there is a formula to calculate SPL for subs. And you yourself said that to do this your Must be able to completely control the environment of the sub.

So, lets assume that the drivers are in an anechoic chamber. Can a formula be developed then?

stevdart

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Posted: January 02, 2005 at 10:09 PM / IP Logged

Just to be helpful here, Poorman, because this thread has grown a few pages and hasn't satisfied your curiousity:

May I suggest you ask the authors of the WinISD program your questions relating to their equations at http://linearteam.proboards12.com/index.cgi

Another forum where you might find members who are interested in your subject might be http://www.diyaudio.com/

There are published sources as well, some of which are linked to on this site: https://www.the12volt.com/caraudio/caraudio.asp

Please keep in mind that this is a car audio forum and the general interest is in car audio gear and the situations that we all encounter with the installation of it. Good luck with your inquiries.

Poormanq45

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Joined: October 27, 2004

Location: United States

Posted: January 03, 2005 at 7:54 AM / IP Logged

Thanks for all of your help, everyone.

I realize that it is very difficult to calculate things that I am talking about, but I think it may be possible to get a fairly accurate equation if some variables are controlled.

Stevdart: Thank you for the links. I'll check out those forums and see/read what they have to say. Also, here are a few other Audio Forums that have good info:

CarSound and Performance Forum

TermPro Forum

Sound and Vision Magazine Forums

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SPL formula?

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