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Old 02-23-2010   #1
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Default The facts about speaker sensitivity ratings!

I thought about posting this a month or so back due to some responses in a thread about a particular subwoofer and it's high sensitivity...artificially inflated sensitivity I might add because it was a D2 measured with the coils in parallel, but never did, but again today I saw more members misunderstanding speaker efficiency ratings.

So here it goes:

When you see a sensitivity rating, look carefully at exactly what it says, don't just read 93db and run with it. If it says 1w/1m, you're good to go. If it says 2.83v/1m you aren't.

Here's the deal, 2.83v/1m ONLY means 1 watt if it's an 8 ohm speaker, if it's anything else, it isn't 1 watt.

2.83v seems to be the norm these days so when you encounter it, make sure you look closely at the impedance of the driver. If it's a dual voice coil, it's almost guaranteed that the measurement was with the coils in parallel and that will always artificially raise the sensitivity spec.

Let's look at an imaginary subwoofer and let's say it's available in 8, 4, 2 and 1 ohm, but it's otherwise the same and it's rated at 2.83v/1m. Here's what it would look like on paper:

10" 8 ohm = 85db
10" 4 ohm = 88db
10" 2 ohm = 91db
10" 1 ohm = 94db

In reality they are all 85db, because 2.83v = 1 watt at 8 ohms, but it equals 2 watts at 4 ohm, 4 watts at 2 ohms and 8 watts and 1 ohm. So the 1 ohm speaker is actually measured 8w/1m.

So in summary, check whether it says 2.83v/1m or 1w/1m and then check the impedance it was measured at. They can't magically make a subwoofer with a sensitivity of 93db without sacrificing something else. Efficiency is not free, hence Hoffman's Iron Law.


I hope this clears up some confusion on the subject.
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Old 02-24-2010   #2
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Default Re: The facts about speaker sensitivity ratings!

I really thought this would be useful as I see misunderstanding of sensitivity ratings all the time here, but maybe not.

Hopefully no one had a comment, but it was useful.
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Old 02-24-2010   #3
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Default Re: The facts about speaker sensitivity ratings!

Good post.

Can you please change your Avatar or icon? Her eyebrows bother me. lol

It is very easy to conflate cause and effect that are unrelated in audio design. In fact, the entire audiophile industry is based upon this ease of fallacy.
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Old 02-24-2010   #4
 
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by cubdenno View Post
Good post.

Can you please change your Avatar or icon? Her eyebrows bother me. lol
LMFAO

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Old 02-24-2010   #5
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by 89grand View Post
I really thought this would be useful as I see misunderstanding of sensitivity ratings all the time here, but maybe not.

Hopefully no one had a comment, but it was useful.
I just recently ran into this as well in a thread. Maybe that was the thread you were were reading. Either way, it's useful information, and made me take a second to step back before pulling the trigger on a D4 sub. Thanks.

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Old 02-24-2010   #6
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Default Re: The facts about speaker sensitivity ratings!

I think 2.83V is easier to compare than 1W. An amplifier gives more power at lower impedances because it's output stays stable down to 2 or 1 ohm. It gives you the same voltage at 2 ohm as at 4 ohm, but thanks to Ohm's Law: the same voltage results in double the power at half the impedance....

Since the output voltage of an amplifier stays pretty stable, using the 2.83V efficiency spec is easier to compare drivers with different impedances than using the 1W spec.

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Old 02-24-2010   #7
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by Candisa View Post
I think 2.83V is easier to compare than 1W. An amplifier gives more power at lower impedances because it's output stays stable down to 2 or 1 ohm. It gives you the same voltage at 2 ohm as at 4 ohm, but thanks to Ohm's Law: the same voltage results in double the power at half the impedance....

Since the output voltage of an amplifier stays pretty stable, using the 2.83V efficiency spec is easier to compare drivers with different impedances than using the 1W spec.

greetings,
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Assuming an amplifier puts out more power into a lower impedance, yeah ultimately it would get louder, in other words a dual 4 ohm sub wired in parallel for 2 ohms will get louder with an amp rated at say 600 watts at 2 ohms than the same woofer would with the coils wired in series and the amp putting out say 250, but the speakers sensitivity rating is still the same.

My point was that rating at 2.83v gives some people the impression that a given subwoofer with a D2 voice coil wired in parallel is much more efficient than the same sub with a single 4 ohm, but it's not, The specs just make it look like it is.

1w/1m puts them all on the same playing filed and is much easier to compare drivers because you don't have to take the impedance into account like you do with 2.83v. Either way, 2.83v seems to be the norm and it's here to stay, I just wanted people to understand what it truly means.
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Old 02-24-2010   #8
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Default Re: The facts about speaker sensitivity ratings!

You're right about the sensitivity ratings of DVC subwoofers, but off-course it's not realistic to stare at the sensitivity rating of a DVC subwoofer wired in parallel if you're planning to wire it in series.
Sensitivity rating of a subwoofer wired in series is NOT the same as the same subwoofer wired in parallel, but it's possible you won't find the series-wired spec in the specsheet. You can calculate it out of the parallel-wired-sensitivity rating though...

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Old 02-24-2010   #9
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by Candisa View Post
You're right about the sensitivity ratings of DVC subwoofers, but off-course it's not realistic to stare at the sensitivity rating of a DVC subwoofer wired in parallel if you're planning to wire it in series.
Sensitivity rating of a subwoofer wired in series is NOT the same as the same subwoofer wired in parallel...

greetings,
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How would the sub produce more sound (have higher sensitivity) with 1 watt of input wired in parallel vs wired in series with 1 watt of input?
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Old 02-24-2010   #10
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Default Re: The facts about speaker sensitivity ratings!

Good information and I agree it needed to be addressed for quite some time.
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Old 02-24-2010   #11
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by 89grand View Post
How would the sub produce more sound (have higher sensitivity) with 1 watt of input wired in parallel vs wired in series with 1 watt of input?
It doesn't, but it does produce more sound with 2.83V of input wired in parallel vs wires in series
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Old 02-24-2010   #12
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by Candisa View Post
It doesn't, but it does produce more sound with 2.83V of input wired in parallel vs wires in series
Exactly. That's precisely what this thread was supposed to address, the misunderstanding of what exactly 2.83v means when looking at driver sensitivity.

Basically I've been seeing some threads where someone says "Holy shit, this new (insert name) subwoofer looks great, really high sensitivity too". What they didn't notice was that it was a D2 subwoofer with the coils wired in parallel, so the 2.83v was at 1 ohm, or 8w/1m. I just want to help people understand what they are seeing. It's not some sub that defies the laws of physics, but a numbers game that makes it look like it has a higher sensitivity than other similar subwoofers.
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Old 02-24-2010   #13
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Default Re: The facts about speaker sensitivity ratings!

Correct, that's why I'm not against using the 2.83V norm, but I'm against using it wrong. It is very easy to calculate what the dB/2.83V/m rating of a DVC sub wired in series is, if you know the dB/2.83V/m rating of it wired in parallel.
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Old 02-24-2010   #14
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Default Re: The facts about speaker sensitivity ratings!

Quote:
Originally Posted by Candisa View Post
Correct, that's why I'm not against using the 2.83V norm, but I'm against using it wrong. It is very easy to calculate what the dB/2.83V/m rating of a DVC sub wired in series is, if you know the dB/2.83V/m rating of it wired in parallel.
It is easy to calculate...if you know what you're looking at and what it means. I think we have some members that don't/didn't know that, hence this thread.
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Old 02-24-2010   #15
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Default Re: The facts about speaker sensitivity ratings!

Okay
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Default Re: The facts about speaker sensitivity ratings!

Unless the manufacturer specifically states how they got their sensitivity rating in the first place it's pretty much useless whether it's rated at 1w or 2.83v. One manufacturer may list sensitivity at 1khz while another may use the average of a 500hz-2500hz sweep and if we're talking about subs then what good is a sensitivity rating taken at 1khz anyways. For example, this sub is rated at 99db sensitivity but if you look at the response below 100hz it's well below that 99db rating

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Old 02-24-2010   #17
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Default Re: The facts about speaker sensitivity ratings!

I try not to look too much into sensitivity ratings unless they're like 80-82db (then I shy away), or if they're like 94 & higher (which would be pro audio, or there's something going on that requires some looking into).

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Default Re: The facts about speaker sensitivity ratings!

Don't know if its just me, but when speaker companies use sensitivity specs to rate their speakers in decibels (dB) are they doing so because they feel that the consumer will not understand the spec if it were a percentage? That is, are the using the word "sensitivity" interchangeably with "efficiency"? I'm assuming that both "sensitivity" and "efficiency" mean the same thing when talking about speakers. If so, do the companies feel that if a certain speaker has a higher "sensitivity" spec that it will attract more buyers as opposed to another speaker company that prints the nominal efficiency of their speakers? I'm guessing yes because I think more people would be inclined to purchase a speaker with a 95db sensitivity rating versus a speaker with 3% efficiency rating.
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Old 02-24-2010   #19
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Default Re: The facts about speaker sensitivity ratings!



True, it's really just marketing...but it does seem to work since a number of people have been impressed by higher numbers, not knowing what they really meant and that they where pretty much inaccurate.

Hopefully this thread will help eliminate that.
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