dB estimate

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jeffchilcott

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Posted: February 03, 2004 at 4:40 PM / IP Logged

i would say it probably measures close to a guy i installed the same stuff in a 90 cougar...about the same size car maybe a little bigger. he measured 121.3 db so maybe that will answer your question.

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forbidden

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Posted: February 03, 2004 at 4:44 PM / IP Logged

This "spec" has a real meaning, it however does not tell you how something will sound or how it will react in a vehicle or enclosure. It is a measurement of how loud the speaker plays as compared to all others. This "spec" is also one that has an agreed upon standard in the industry. In general terms this is what it is.

The speaker is mounted in an anechoic chamber (a dead room - no reflections)

The speaker is fed pink / white noise (think of a dead channel on a tv)

The speaker is fed exactly one watt of power.

The speaker has a microphone exactly one meter away from the speaker.

The microphone measures how loud that speaker "plays" the test signal and records it in decibels.

Thus the speaker is given a "spec" of in this case 87db/1w/1m

A speaker that is more efficient, say 92 db will play much louder with the same amount of input power, a speaker that is less efficient, say 82 db will play much quieter with the same amount of input power.

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sssssss27

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Posted: February 03, 2004 at 4:59 PM / IP Logged

I'm going to have to agree with forbidden, while I don't have much hands on experience, I have been reading as much as I can the math side of things. I have always heard in order to increase 3db you need to either double the surface area or double the power. Like the other people are saying though there are a lot of variables.

Maxst

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Posted: February 03, 2004 at 5:44 PM / IP Logged

forbidden is right. The speaker isnt even in any box..its just sitting there.

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geepherder

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Posted: February 03, 2004 at 6:43 PM / IP Logged

Julian59, Rob is correct. The numbers do not lie, as you put it. There is a theoretical 3 dB increase for every time the power is doubled. If you increase the power tenfold, the decibels increase by a factor of 10. That being said, if the woofer in question has a sensitivity rating of 87, and we feed it 100 watts, we should get 107 dB's. Now, if we feed it 400 watts, as in the original post, we'll get (+3+3) 113. Double that to feed max power, and we end up with 116. Mind you, this does not take into consideration cabin gain or the fact the woofer is in an enclosure. I think it's safe to say our friend will be above the 120 dB mark, but there's no telling how much without a meter.

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jpranwez

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Posted: February 03, 2004 at 8:27 PM / IP Logged

Thanks for the explanation. I appreciate it.

forbidden

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Posted: February 03, 2004 at 8:31 PM / IP Logged

Your welcome.

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geepherder

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Posted: February 03, 2004 at 9:32 PM / IP Logged

Yeah, Rob that was good, I never knew before how that test was conducted. Jpranwez, do not get efficiency confused with sensitivity. Sensitivity is what Rob posted about, measured in dBs. Efficiency is always expressed as a percentage- how much input power is converted into sound (93% or whatever).

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Julian59

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Location: United States

Posted: February 03, 2004 at 10:25 PM / IP Logged

jpranwez wrote:

Exactly what does the efficiency rating mean. I was told it's the sound level that a sub is most efficient but that sounded odd.

Well it means diffrents things to some and a lot to others. OK lets say you have two 12" subs, if these speakers are rated at 89db @ 1 watt/1meter and you have an amp that rated at 200 watts your basiclly getting 92dbs out of it (not SPL) now if you have a pair of 12" speakers that are rated at 101db @1watt / 1meter with a 2 rated amp at 75 watts each you'll get 101dbs. Yes I know these guys don't agree with me. That's cool. Here's something you will agree with. If you shop around for the most efficent speakers you can find you'll need less power to run your system, that mean less money spent for Amps(power) and less money spent on a huge charging system to run all that raw power that you need for your boom,boom. You can have a system that powered with under 500 watts and sound like 1200 .

There is another power test for speakers (using spectrum specifed in EIA Standard SE-013 Section SE3)

30 ft. at .001 watt input = ?? dbs 54dbs

10 ft. at 1 watt input = ?? dbs 93dbs

4 ft. at 200 watts input = ?? dbs 124.5dbs

the 2nd dbs is the rating of my sub speakers. My 1963 Chevrolet Impala SS Convertible has tested at 120 dbs and has an SPL of 132 8 speakers. 2 -15s, 2-mid mids, 2 high mids, 2 tweeters. total power of 420 watts

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bberman1

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Posted: February 04, 2004 at 1:08 AM / IP Logged

forbidden's calcs and DB estimates look good to me.

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