do different drivers play louder at the same rate? - diyAudio
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Old 18th March 2013, 07:42 PM   #1
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Default do different drivers play louder at the same rate?

When desigining a mult-way speaker how do you know that the different drivers will play at the same relative SPL over for all input voltages. T/S sensitivity is measured at only one power level (1 watt) and often only at one frequency. How do you know that two drivers will play at the same relative SPL for 2,10,20,100 watts, etc...?

Of course I can measure the speaker at different levels once assembled. But what should I look at when evaluating drivers?
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Old 18th March 2013, 08:04 PM   #2
fpitas is offline fpitas  United States
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Not sure I understand the question. If they're at all linear responding, the output will scale with the drive level.
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Old 18th March 2013, 09:04 PM   #3
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That's basically my question. When you consider all of the different speaker designs (cone, dome, horn, ribbon, ...), materials used (paper, metal, fabric, sandwich,...) and physical size. Is it safe to assume that any driver will have SPL scale linear with input power?
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Old 18th March 2013, 09:06 PM   #4
adason is offline adason  United States
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linear to certain level, yes...
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Old 18th March 2013, 09:08 PM   #5
fpitas is offline fpitas  United States
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Exactly. If they're so non-linear the output is no longer more or less proportional to the input, they're probably unlistenable.
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Old 18th March 2013, 09:14 PM   #6
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Good question!!!

To a first approximation, drivers are linear input-output devices. But every driver has its limits due to a finite voice coil length, so each will run out of excursion capability at some SPL, distortion will increase (a lot) and SPL will level off even if power input is increased. Then there is the issue of power input and heat generation. Remember that over 99% (typical for home audio drivers) is dissipated as heat. When a voice coil heats up, its resistance increases. This causes the sensitivity to a given voltage input to go down. This annoyance is very important for pro sound speakers! Thus, even if you are operating within the mechanical limits of the driver (e.g. within Xmax) if you deliver a lot of power over time to the driver the SPL will drop, and not necessarily in a fashion that is independent of frequency either. Each driver will do this differently, depending on its design.

So I guess the answer depends on the conditions you are operating under: short high power bursts or longer heat building continuous operation at moderate power levels.

-Charlie
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Old 18th March 2013, 09:48 PM   #7
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Quote:
Originally Posted by CharlieLaub View Post
Good question!!!

So I guess the answer depends on the conditions you are operating under: short high power bursts or longer heat building continuous operation at moderate power levels.
I understand that all drivers will behave differently at their limits.

I should have thought more before asking the question. I was thinking of the problem more mechanically: how can drivers of such different mechanical designs all have the same SPL/power response? But now that I think back to my physics education, I know that energy has to be conserved. So as the power increases, the SPL needs to increase proportionately until the point that the physical characteristics of the driver change (xmax, or coil overheating). At which point a larger percentage of the power is dissipated as heat.
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Old 18th March 2013, 10:01 PM   #8
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Originally Posted by falconsprint View Post
Is it safe to assume that any driver will have SPL scale linear with input power?
Linear with respect to voltage........supposedly.
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Old 18th March 2013, 11:19 PM   #9
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Ah, but..

If the THD of one driver rises faster than the other, would that driver sound louder than others given the same drive voltage?
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Old 18th March 2013, 11:29 PM   #10
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by chris661 View Post
.. would that driver sound louder than others given the same drive voltage?
yes, but hope you wont be listening to it

very often its the crossover is causing a peak....been there a few times too
its tricky
it will sound like its the driver, but it really isnt
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