need to understand the Db and OHMS in speakers - AVS Forum
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post #1 of 14 Old 10-10-2013, 07:10 AM - Thread Starter
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Can someone explain real fast what am I looking for in speakers as far as OHMS and DB ?

 

is the higher DB better or lower number better? like is 91db better than 88 db?

in ohms, is lower better ? i see most is 8 ohms

 

is there anything else i need to look for in a speaker?

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post #2 of 14 Old 10-10-2013, 07:20 AM
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The dB on a speaker's spec is the sensitivity. This means that if a speaker has a 89dB sensitivity, it will take 1 watt of power to make that speaker produce a loudness of 89dB from 3 feet away. As you move farther away, the loudness decreases, and so more power is needed to maintain a specific volume at a certain distance. A higher sensitivity means the speaker will play louder when given the same power. However, you need a 10dB increase to have a perceived doubing of volume.

The ohms is the impedance of a speaker and relates to the power handing. A lower impedance means the speaker will put a larger load on the amplifier. So an 8ohm speaker is easier to drive than a 4ohm speaker.

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post #3 of 14 Old 10-10-2013, 07:34 AM - Thread Starter
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so is 91db better than 88db in a speaker?

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post #4 of 14 Old 10-10-2013, 07:39 AM
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Quote:
Originally Posted by nycguy718 View Post

so is 91db better than 88db in a speaker?

91db will be louder than 88db for the same amount of amplifier power. Whether or not that is "better" is up to you to decide.

Here's some more information on speaker impedance to help you out: http://news.cnet.com/8301-13645_3-9790255-47.html

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post #5 of 14 Old 10-10-2013, 07:43 AM
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Quote:
Originally Posted by nycguy718 View Post

so is 91db better than 88db in a speaker?

That depends. If it's the same speaker manufacturer, generally speaking, yes. If you're comparing between two different speakers, there are many other factors ( including sensitivity ) that contribute to whether the speaker is " Better " then one another. What speakers are you comparing?

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post #6 of 14 Old 10-12-2013, 01:01 PM
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Originally Posted by cel4145 View Post

91db will be louder than 88db for the same amount of amplifier power. Whether or not that is "better" is up to you to decide.
... if they are measured at constant voltage. If they are measured @1w, then you would also need to know the ohm resistance. 88db@1w@8ohm and 91db@1w@4ohm is the same volume-for-power.
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post #7 of 14 Old 10-12-2013, 01:21 PM
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Originally Posted by Sean Spamilton View Post

If you're comparing between two different speakers, there are many other factors ( including sensitivity )
That, and not all manufacturers are totally honest with their sensitivity ratings. Some fudge their specs by a good 6dB.

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post #8 of 14 Old 10-13-2013, 03:15 AM
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Quote:
Originally Posted by Transmaniacon View Post

The dB on a speaker's spec is the sensitivity. This means that if a speaker has a 89dB sensitivity, it will take 1 watt of power to make that speaker produce a loudness of 89dB from 3 feet away. As you move farther away, the loudness decreases, and so more power is needed to maintain a specific volume at a certain distance. A higher sensitivity means the speaker will play louder when given the same power. However, you need a 10dB increase to have a perceived doubing of volume.
.

I thought +3 dB increase was a doubling of volume.

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post #9 of 14 Old 10-13-2013, 03:37 AM
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Quote:
Originally Posted by NuSoardGraphite View Post

I thought +3 dB increase was a doubling of volume.

uh uh nope nada they say generally it takes twice the wattage say 100 watts increased from 50 watts to gain 3dB in loudness on a given speaker ,that is barely noticeable if even at all at higher levels especially if you have room gain

Bills the expert here some of the other folks seem to have a good handle on things also .I belive reference level for THX movie sound tracks in theater is something like ~ 85dB average level?


ofc there is more to THX than that but that will kinda will give you an idea 3dB is not much gain or loss of loudness barely perceptible I think.

someone might want to ad to that .

Google says .............. Barely Perceptible Change @ 3dB http://www.gcaudio.com/resources/howtos/loudness.html

Luckily the resident double blind listening test hearing perception all knowing 'Phd's ' have not appeared yet , must be past their bed time biggrin.gif
Some times it gets ugly when they try to postulate and the folks disagree threads can go off on a wild tangent for days although there are one or two possibly more here that aren't so bad and quite knowledgeable and actually contribute some useful dialog.

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post #10 of 14 Old 10-13-2013, 04:41 AM
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Quote:
Originally Posted by nycguy718 View Post

so is 91db better than 88db in a speaker?

Not better. Not worse. Simply a difference in sensititivy. Don't spend any time worrying about it. The impedance (ohms) is a measure of the speaker's resistance to AC current. The lower the number, the more current the speakers will draw to achieve a given loudness level. For the most part you can ignore that as well although, in rare circumstances, a very low impedance can cause speakers to try to draw more current than the amplifier can supply. That is bad. Unless you listen at crazy volume levels, it isn't a problem. If you do listen at crazy volume levels then go for a speaker system of 6 ohms or 8 ohms.
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post #11 of 14 Old 10-13-2013, 04:59 AM
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Quote:
Originally Posted by NuSoardGraphite View Post

I thought +3 dB increase was a doubling of volume.
Double the power for an increase of 3 db.
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post #12 of 14 Old 10-13-2013, 11:19 PM
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Quote:
Originally Posted by NuSoardGraphite View Post

I thought +3 dB increase was a doubling of volume.

Double Power is +3db
Double Volume is +10db

It takes a little over 10x the power to get double the volume, assuming equal sensitivity.
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post #13 of 14 Old 10-15-2013, 12:25 AM
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Quote:
Originally Posted by Dasteru View Post

Double Power is +3db
Double Volume is +10db

It takes a little over 10x the power to get double the volume, assuming equal sensitivity.

Ah yes, that's right. Thanks.

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post #14 of 14 Old 10-15-2013, 01:44 AM
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Edit
2 x amplifier power only results in +3 dB acoustic loudness barely perceptible increase .
.To double acoustic loudness ( X 2 ) = +10 dB SPL more that requires 10 times more amplifier power.
To quadruple acoustic loudness (X 4 ) = +20dB the amplifier needs 100 X power


http://www.sengpielaudio.com/calculator-levelchange.htm

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