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"TRUE" 18" Driver Reference Efficiency Calculator

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levyte357 View Drop Down
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    Posted: 18 May 2012 at 3:01pm
For those sick of dubious manufacturer sensitivity figures.

Originally posted by <br><a href=http://www.mh-audio.nl/Reference.asp target=_blank rel=nofollow>http://www.mh-audio.nl/Reference.asp</a>
http://www.mh-audio.nl/Reference.asp wrote:



This calculator is intended to help you determine the reference efficiency of any loudspeaker.

There is no standard for stating the efficiency of a loudspeaker, so some manufacturers will give a rating at 1kHz for a subwoofer. This makes the speaker seem like it is a lot more efficient, but it is unfair when comparing to another subwoofer with an efficiency rated at 100 Hz ( and not many subwoofers are used at 1kHz anyway :-) ).

This formula will give you a reference number that will allow you to compare subwoofers on an equal basis.


http://www.mh-audio.nl/Reference.asp





Edited by levyte357 - 18 May 2012 at 6:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2012 at 3:27pm
Figures so far,

(Excel spreadsheet image)




Edited by levyte357 - 14 June 2012 at 12:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PauliePaul Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 10:24am
Do the Fane Colossus 18B and 18B600 too..... it may Shocked a few!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 10:34am
Ray, what is the bottom BMS drive unit?

If you want to stick a BMS driver up that is more representative of the rest on the list then you should have chosen the 18S430v2

Tony


Edited by Tony Wilkes - 19 May 2012 at 10:47am
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SBC Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 10:50am
Originally posted by PauliePaul PauliePaul wrote:

Do the Fane Colossus 18B and 18B600 too..... it may Shocked a few!!

that goes for many drivers...

this calculator basically just take this thread (which has been up for ages) one step further by putting it into a dB figure. http://forum.speakerplans.com/calculating-real-subwoofer-efficiency_topic36294.html
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanD Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 11:22am
If you want a formula that relies on physical parameters rather than calculated ones, you can use:

dBref=20*LOG10(BL*Sd/(Mms*SQRT(Re)))+59.4

-- the reason should be obvious, it's proportional to (BL/sqrt(Re) and Sd, inversely to Mms.

V18-1000 97.6
Turbomax 1800i 97.4
etc etc

I've found that the physical parameters often seem more realistic than the derived ones like Vas and Qes, but this may not always be true...


Edited by IanD - 19 May 2012 at 11:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 11:29am


The driver No=% is for the octave between the EBP and the Mass Corner, and as we can see is not a good indicator of how the driver will produce bass (we need a speaker program for that).

From the above example, the least efficient driver produces the most bass below 100hz.

The most efficient driver is 3.39dB more efficient, but requires about 3dB more power to play as loud as the least efficient driver (in the bass), and even then will probably not be able to play as loud due to power compression.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SBC Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 11:30am
from real world listening however, i will say, and i think a few will agree, the chart at the beginning of the thread is very realistic compared to results of the above calculation. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanD Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 11:55am
Of course reference efficiency doesn't tell you how a driver will perform in a cabinet especially at the bass end, this totally depends on the cabinet (reflex, bandpass, horn, tapped horn, hybrid...) -- drivers with high efficiency have bass rolloff because of low Qes unless you use a cabinet suited for such drivers, which tends to mean a big horn.

But it is one of the basic "how efficient is the driver" parameters, and is the one that manufacturers should use to describe efficiency -- not the response at 500Hz for a sub driver like some do...

If you want to compare the "derived" (first post) vs. "physical" numbers (my equation):

Driver               Derived          Physical        Difference
V18-1000         97.5               97.6              0.1
V18-1200         95.4               94.7              0.7
18NLW9600     94.8               95.0              0.2
Tmax 1500       94.8               97.9              3.1
18SW115         94.6               94.7              0.1
Tmax 1800       94.6               97.4              2.8
BMS 18N860    92.5                92.6              0.1

It should be obvious which manufacturers have consistent parameters and which don't (Turbomax)...


Edited by IanD - 19 May 2012 at 12:13pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 12:27pm
Originally posted by SBC SBC wrote:

from real world listening however, i will say, and i think a few will agree, the chart at the beginning of the thread is very realistic compared to results of the above calculation.


+1

Is very easy to get lost in equations/graphs, without a realistic point of reference, i.e., having heard most of the above drivers in the chart.

Ask anyone who has, and they will tell you, Turbomax/Celestion CF18JVD require huge amounts of power to do anything useful, where as V18-1000 sounds louder than mighty 1850 with same amount of power.

The initial calculator/chart mirrors the actual driver performances/comparisons in reality (have personally heard/compared all of them except the Neos), therefore I won't be considering any other theorem in this thread.

Originally posted by Tony Wilkes Tony Wilkes wrote:

Ray, what is the bottom BMS drive unit?


http://www.lautsprechershop.de/pdf/bms/bms-18n830.pdf

I just put up BMS drivers I've seen mentioned on SP, or drivers members say they have bought.


Edited by levyte357 - 19 May 2012 at 1:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2012 at 1:06pm
Originally posted by Tony Wilkes Tony Wilkes wrote:


If you want to stick a BMS driver up that is more representative of the rest on the list then you should have chosen the 18S430v2

Tony


Driver added.

Would expect this driver to have a "very" warm sound, and drop very deeply indeed.

Even though "honest" Xmax of 8mm is detailed, by other manufacturers "fudge factor", the Xmax would be approx 10mm.

If BL was higher, would be such a serious contender for the big boys, especially at the price.




Edited by levyte357 - 19 May 2012 at 1:09pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2012 at 12:04pm
Just updated table, to include FAITAL PRO 18HP1020. Thumbs Up
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