dB per Watt Ported - Realm of Excursion



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Old 10-19-2006   #1 (permalink)
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Old 10-19-2006   #2 (permalink)
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Default Re: dB per Watt Ported

Any thoughts on the outrageous difference between the Dayton and every other woofer?
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Old 10-19-2006   #3 (permalink)
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Default Re: dB per Watt Ported

because it could only withstand 100 watts....

since at most, you'll only get a 3 db gain from doubling power.. if it were to withstand more power... its numbers would be in line with the other drivers..

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Old 10-21-2006   #4 (permalink)
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Default Re: dB per Watt Ported

Quote:
Originally Posted by Raven
Any thoughts on the outrageous difference between the Dayton and every other woofer?

This is a bit misleading and should be called db/watt at manufactures recommended RMS Power handling, but in reality is sort of bogus if you look closely…

For instance, in the extreme case of the Fi BLT which clearly has a much higher sensitivity rating than many of the drivers, it actually did worse in this quasi dynamic sensitivity measurement. The reason is that 2000 watts clearly puts this driver into either a power compression state, a bl limitation state or a compliance limited state or other or a combination. Either way, you can keep putting more power into the driver and not get much more output relative to what you can get going from 100 watts to 200 watts for example. At 1000 watts or 500 watts, the BLT would probably walk away with the db/watt title with ease. Sure, its loudest at 2000 watts, but you’re clearly beyond linear limits observing its baseline sensitivity. That, or you have low voltage amplifiers that can’t deal with back EMF.

Secondly, and probably more pertinent, the db per watt ratio is completely ambiguous anyway. The first db gives you the sensitivity which can range from 80 to 90ish dB among those drivers. Hypothetically speaking, if a manufacture rated their driver at 1 watt RMS, then the db/watt ratio would be off the charts. Even if the driver maintained a perfect linear excursion up to infinity which is impossible, the db/watt would eventually drop to 0 because if you take the limit of (3x)/(2^x) as x goes to infinity, you get zero. 3x/2^x would be the ratio of perfect linearity as the dB increases. If you look down the line, the watts decrease from high to low perfectly, so it does tell you much at all, lol.

Sigh…

Therefore, I quickly derived a different formula to use which compensates for Thiele small sensitivity and gives a number more or less like db/watt. Call it the dynamic sensitivity rank. Its more or less some bull**** I just made up, but at least it works.

[ ln( 1 / RMS watts) ] / [ ln (2) ] + ((Measured SPL at RMS power) – (Sensitivity at 1 watt)) / 3

That will just give you a number much like db per watt. (it may be negative depending on the type of box)

The formula resides around the fact that doubling the power gives you 3 more dB if you are within linear limits.
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Old 10-21-2006   #5 (permalink)
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Default Re: dB per Watt Ported

wasn't anything special about the db /watt... just a simple thing we added... Power used / average SPL... that's about it..

you sure act like you know alot about the BTL.. Kyle from TC sounds..

I thought you learned your lesson about going out on a limb in past experiences..

you're trying to make a point out of nothing...

just another piece of data to list.. whether or not it has any meaning, aside from a number to look at.. I really don't care.. lol

I couldn't recite a single efficiency spec from any of the drivers tested.. we test.. they do what they do..

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Old 10-24-2006   #6 (permalink)
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Default Re: dB per Watt Ported

No need to get offensive here, if you're going to leave it up to your readers to interpret the graphs without explanation, you should expect comments like these, no?
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Old 10-24-2006   #7 (permalink)
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Default Re: dB per Watt Ported

No need to get offensive here, if you're going to leave it up to your readers to interpret the graphs without explanation, you should expect comments like these, no?
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Old 10-24-2006   #8 (permalink)
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Default Re: dB per Watt Ported

well most of the readers aren't here with the sole determination of trying to prove I didn't test a certain woofer correctly...

or maybe you didn't say that to several people..

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Old 10-25-2006   #9 (permalink)
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Default Re: dB per Watt Ported

The only difference in testing any of the woofers I saw , was after all regular test were completed . Those that were designated 'bang on em' were then spanked wide open by the sundowns
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Old 10-25-2006   #10 (permalink)
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Default Re: dB per Watt Ported

Quote:
Originally Posted by bigbassman
well most of the readers aren't here with the sole determination of trying to prove I didn't test a certain woofer correctly...

or maybe you didn't say that to several people..

Loyd L.
uhm...
you lost me bro, I'm just trying to help out with the presentation of the data, thats all.
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Old 10-29-2006   #11 (permalink)
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Default Re: dB per Watt Ported

I do notice a trend in that the "least efficient" drivers on this page are the ones taking in the highest amount of power. Judging from the Power inputs given it's right at RMS power.

In a way this makes perfect sense. Rather than give your run of the mill 1w / 1m rating, it's a simple matter of dBs / watts (mathematical division) while the driver is driven at rated power.

In other words, what you see it what you'll get from each driver in it's given sized boxed at RMS power, but only under those conditions. While the Oz Power may look pitifully inefficient on that chart, if the input power it was tested at were to drop to the same 100 watts the Dayton was given, the story would be amazingly different.

Am I getting close?
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Old 10-31-2006   #12 (permalink)
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Default Re: dB per Watt Ported

Quote:
Originally Posted by Raven
I do notice a trend in that the "least efficient" drivers on this page are the ones taking in the highest amount of power. Judging from the power inputs given it's right at RMS power.

In a way this makes perfect sense. Rather than give your run of the mill 1w / 1m rating, it's a simple matter of dBs / watts (mathematical division) while the driver is driven at rated power.

In other words, what you see it what you'll get from each driver in it's given sized boxed at RMS power, but only under those conditions. While the Oz Power may look pitifully inefficient on that chart, if the input power it was tested at were to drop to the same 100 watts the Dayton was given, the story would be amazingly different.

Am I getting close?

Yes, but my point is, simply dividing the dB by the power still makes no sense even if all of these drivers were NOT in a power compression state and they were so its even worse and more arbitrary, which perhaps was the point because RMS in general is pretty darn arbitrary and mostly inflated to sell speakers.

Here is a good counter example.

Driver x has an sensitivity of 90dB at 1 watt at 1 meter and an RMS = 1024 watts
Driver y has an sensitivity of 80dB at 1 watt at 1 meter and an RMS = 128 watts

If driver x could take 1024 watts without ANY compression but anymore would put it into compression, then it would do 120dB at 1 meter in an IB (more or less)

If driver y could take 128 watts without ANY compression but anymore would put it into compression, then it would do 98dB at 1 meter in an IB (more or less)

Driver x scores: 128/1024 = 0.124

Driver y scores: 98/ 128 = 0.766

Driver y wins by a mile but it actually loses by a mile.

Driver x is CLEARLY more sensitive and can take more power and yet scores far worse.

The measurements are OK for this test, the math does not contain any meaning or value.
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Old 10-31-2006   #13 (permalink)
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Default Re: dB per Watt Ported

Kyle what if the ln of the sensitivity was used? I think one of the problems is that they are dividing numbers that are on a logarythmic scale incorrectly. The way they've done it, half of 100 db would be 50 db. But that is incorrect half of 100 db is 97 db. If the logarythmic scale was taken into account, and the graph was redrawn, it may have more meaning.



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Old 10-31-2006   #14 (permalink)
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Default Re: dB per Watt Ported

Quote:
Originally Posted by Fallen
Kyle what if the ln of the sensitivity was used? I think one of the problems is that they are dividing numbers that are on a logarythmic scale incorrectly. The way they've done it, half of 100 db would be 50 db. But that is incorrect half of 100 db is 97 db. If the logarythmic scale was taken into account, and the graph was redrawn, it may have more meaning.

yes, you are right

now what i REALLY wanted to see was THD measurements.... and a true A/B test

maybe next time...
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Old 11-02-2006   #15 (permalink)
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Default Re: dB per Watt Ported

Surely you have the know how, maybe donate your expertise next time they do it.

There are some other drivers I'd like tested.

Hey Shon think you could donate a ID OEM to a good cause (if they ever do a round for 15's that is)



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Old 11-02-2006   #16 (permalink)
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Default Re: dB per Watt Ported

Kyle can do it himself...

since woofers aren't supposed to be tested in vehicles with power... under conditions that normal users go by..

I didn't set out to A/B test the woofers... I set out to provide them the proper rated power, in the proper box, and measure what they did on the meter... and show what each woofer can do in a normal install, which I feel is revelent to the majority of people who buy equipment..

Kyle wants to spend his time doing lab type testing, and point out things that are lost on the vast majority of users... he can go for it... I already told him he can test one of my mags if he chooses...


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Old 11-04-2006   #17 (permalink)
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Default Re: dB per Watt Ported

so long as he doesnt try and copy it like i was told he was plannign to do .... o snap did i say that ... oh well
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