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What would the measurements of a speaker taken inside the speaker cabinet look like?

Razorhelm

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I was just wondering what the measurements taken by a microphone inside a speaker enclosure would look like and how they would compare to those taken from outside like normal.

Would it act like an infinite baffle, would it be like the inside of a car?

Anything useful to be gained from this kind of measurement?
 

AudioStudies

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Most speaker enclosures are quite a bit smaller than a car's interior. I think the answer would depend on whether the speaker has a sealed enclosure or is ported. Unless it can be shown that there is a correlation between a measurement inside the cabinet with outside behavior in an anechoic chamber, I cannot think of anything useful. I would think inside that standing waves would be more problematic than even in a very small room or car interior. I would think whether or not it would be infinite baffle would depend on the compliance ratio, which in turn depends on cabinet size and properties of the driver.
 

AudioStudies

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Would the goal be to ultimately stick your head inside the speakers (not sure how you'd do this with only one head) to listen to music?
I think you have unleashed a two-headed monster . . . more than one will claim "better imaging" with heads inside cabinets . . . and they will start making cabinet interiors look like "audio jewelry" . . .
 

tomtoo

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Muffeld.High and Midranges are usually closed ack.
How does that compare with a bar piano . . .

Bar piano is bright against.
I mean depending on the speaker. I talk about a typical 3 way. With a fullrange things would be completly different.
 
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DVDdoug

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Of course you'd only hear the woofer. if you have a ported speaker you can stick your ear up to the port and that might be close to what it sounds like inside. Or, you could stick a microphone inside and record it.

A sealed enclosure should go-down to almost zero Hz inside, or all the way to zero if it's perfectly sealed. I suppose you could put a wireless microphone inside a sealed speaker without permanently altering the speaker... Or I know... Stick your cell phone in there and make a recording!

My subwoofers are big enough for a small child to fit inside but last time I stuck a kid in there I forgot to ask what it sounded like! :D:D
 

AudioStudies

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Would the goal be to ultimately stick your head inside the speakers (not sure how you'd do this with only one head) to listen to music?
I think this is something the "mono is better" crowd could really . . . eh hum . . . get their head into . . .
 

Wes

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a Unik mic will not need a very large hole, if you want to find out
 

NTK

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The typical maximum rated SPL for measurement mics are 140 dB SPL (UMIK-1 is 133 dB), which is 200 Pa (89 Pa for UMIK-1). That is equivalent to about 0.002 atm. I believe the typical pressure fluctuations (due to the woofer diaphragm displacements) inside a speaker is a lot higher than 0.002 atm.
 
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Razorhelm

Razorhelm

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I might just have to stick my Umik through a port!
Thanks for the answers!
 

Zvu

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I was just wondering what the measurements taken by a microphone inside a speaker enclosure would look like and how they would compare to those taken from outside like normal.

Would it act like an infinite baffle, would it be like the inside of a car?

Anything useful to be gained from this kind of measurement?

Measurement like that is very usefull if you don't have anechoic chamber flat to 20Hz and you can't lift the loudspeaker on 20m pole to measure its low end.

It is used for anechoic measurements of frequencies up to about 100-120Hz. It doesn't work very well above that. You drill a hole through a side of a loudspeaker test cabinet and set the mic half way between port and woofer. Response that you get is the real low end response of your ported cabinet.

Merging separate measurements of port and transducer to be able to combine it later always allows for a certain degree of error. This way, provided your mic is calibrated down to 10Hz, you get very accurate result.

You shouldn't put a mic through port though, it can mess up the measurement accuracy.
 
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Sphinx

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So a head would mess up the measurements even more ?
How are we to know without measuring ?
Another project for Amir...
Anyone has a Swiss speaker with enough holes in it to send to him ?
 
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