Author Topic: Can I Measure A Speakerís Sensitivity?  (Read 174 times)

Offline James Edward

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Can I Measure A Speakerís Sensitivity?
« on: June 30, 2021, 03:18:27 PM »
In another thread I have been recounting the rebuilding of a friendís speakers- new drivers, rebuilt crossovers, etc. They were originally specíd at 84 db 1 watt. I have a sound meter, test cdís, etc. I am curious more than anything if things have changed much. Any thoughts?
To be honest, my friend is not an audiophile, and an accurate measurement wonít do much other than assuage my curiosity.
Thanks.
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Offline James Edward

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Re: Can I Measure A Speakerís Sensitivity?
« Reply #1 on: June 30, 2021, 05:23:57 PM »
You know what- on second thought, Iíve experienced enough variation on what a speaker manufacturer specifies to know that the outcome is Ďelasticí to put it kindly. Iíll just report back my impressions.
Thanks.
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Offline Nick B

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Re: Can I Measure A Speakerís Sensitivity?
« Reply #2 on: June 30, 2021, 05:49:22 PM »
You know what- on second thought, Iíve experienced enough variation on what a speaker manufacturer specifies to know that the outcome is Ďelasticí to put it kindly. Iíll just report back my impressions.
Thanks.

Your results should make your non-audiophile friend quite happy  :thumb:
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Offline S Clark

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Re: Can I Measure A Speakerís Sensitivity?
« Reply #3 on: July 01, 2021, 08:43:43 AM »
Easiest is to get the specs from the manufacturer.  To measure it yourself you need a power meter (in watts), a calibrated mic (or accurate dB meter), a 1Khz signal, a test box, and an amp.  Set the mic one meter from the center of the speaker.  Set the volume for 1W on the meter.  Or see if Rich will measure it for you. 
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Offline James Edward

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Re: Can I Measure A Speaker’s Sensitivity?
« Reply #4 on: July 01, 2021, 03:32:30 PM »
The specs are from the original in 1980- when SEAS made a complete speaker, cabinet and all. The rebuilds are like Abe Lincoln’s axe at this point- different head, different handle…
After 40 years, only the upper bass driver is still in production. The woofer, upper midrange, and tweeter are all best attempts at replicating the Thiele/Small parameters of the original drivers. Brian at Madisound was quite helpful in this regard. I was able to contact SEAS Norway via email and they sent me pdf specs of the cabinets, drivers, and crossovers. The crossover diagrams were helpful to Scott at SG Custom Sound who rebuilt the crossovers.
I realized after I posted this that there is no way I can do an accurate measurement- nor, it seems, is a definitive way of measuring observed by manufacturers.
I’m excited to hear what has transpired- my friend is refinishing the cabinets, so this could take a while.
« Last Edit: July 01, 2021, 03:39:45 PM by James Edward »
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Offline HAL

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Re: Can I Measure A Speakerís Sensitivity?
« Reply #5 on: July 01, 2021, 07:48:01 PM »
A more modern measurement is with an input to the speaker of 2.83Vrms at 1KHz.  A constant voltage is easier to measure than getting a true rms power meter and most DMM's will do that measurement at 1KHz.  That does not change for different impedance speakers, where 1 watt varies depending on load impedance.  A test CD or any PC program like Audacity can make a 1KHz test tone and play it through your CD player or DAC.

A Scott discusses, use a calibrated mic or SPL meter at 1 meter from the tweeter center.

This is going to be pretty loud, so do not do it for long times and with hearing protection.   You do not want to cook the repaired speaker.

Good luck with the testing.

Offline tmazz

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Re: Can I Measure A Speakerís Sensitivity?
« Reply #6 on: July 03, 2021, 04:25:17 PM »
The other thing to keep in mind is that when a manufacturer  they do so in an anechoic chamber, which kills all of the room reflections to they can measure the response of the speaker alone. When you do it at home you will be measuring the speaker plus and interactions the room has with it. the best you can do at home is move it to the center of the room so it is as far away from any reflective surfaces as possible. This won't be perfect but it is about the best you can do without covering all the walls.
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