speaker measurement

[steve s]

i'm going to measure the frequency responce of my speakers again, The last time i connected my sig gen to the amp and measured from the customary 1 metre and then the listening position with my sound meter..

i had a reading through the frequency range and measurements through it in db's

my question is at what volume or db's should the readings be taken,
to compare with the tests done in the mag..

cheers steve

[NickG]

Don't know if its any use, but I had a play with this some time ago (its why I have some carpet stuck to my ceiling :-)). I meant to find the link again for Paul. Think there is still a free trial.

http://www.acoustisoft.com/

[vitalstates]

Hi Steve

As I was saying the other day you ideally need a test rig such as mllsa(mellissa?) or similar. These run through the entire audio range, measuring as they go. The figs are usually quoted as 1 watt at 1 mtr on axis. The 1 watt equates to 2.83 volts. If you have problems I'm sure I can figure a way to transport my set-up as you live so close.

Regards

Ed

[steve s]

Originally Posted by vitalstates

Hi Steve

As I was saying the other day you ideally need a test rig such as mllsa(mellissa?) or similar. These run through the entire audio range, measuring as they go. The figs are usually quoted as 1 watt at 1 mtr on axis. The 1 watt equates to 2.83 volts. If you have problems I'm sure I can figure a way to transport my set-up as you live so close.

Regards

Ed

Ed thanks for the offer.. i had forgot about the 1 watt...

does that mean that low effiency speakers would measure better as they would produce less volume and result in lower amount of db variance ?


i am quite happy to use the sig gen and sound meter at the moment. just want to know i'm comparing eggs with eggs...

thanks steve

thanks steve

[andrew ivimey]

But does your sig. generator give a steady voltage output as you sweep through the frequencies ?????

How do you measure and keep constant your 1 watt output?

How do you know that the mic. on your sound level meter is 'flat' across the
frequency range you wish to measure?

A Maplin meter may be, but hey! for £40 you will get that level of accuracy?

Is your soundfield i.e. the room in which you measure whatever is happening exactly the same as it was when you measured another pair of speakers?

And where were you when you took the measurements? It matters.

Just moving your meter a few inches to the/any side changes the readings very significantly, (I know I've done these experiments) so how acccurate do you want to be?

How accurate is your meter anyway? Or am I a fool to pay several thousand pounds on a calibrated meter, and then a special chap to come and re- calibrate my soundfield (at work) annually?

Otherwise it is sloppy, and very relative, as is any dB scale anyway.

sorry to be so negative but right now that's how I feel.

[steve s]

thanks for those kind words of encouragement Andrew...

But why are you feeling so negative.. surely not my post?

you've got lots of good points

my 'calibrated' fluke has just measured 3 sig gens, one has an almost flat output.. but only up to 14 khz.. but as I don't hear much above that.. hey..

and yes i do have a maplins sound meter.. a digital one..... i have no way of testing that.. have you tested one against your calibrated set up at work?

i quite agree about positions/ locations and some drivers are much worse than lowthers at being directional ..
in any case for me the important measurement point is where i sit..

what i was after was simply a reference to how the db's variance was measured and at what volume level...and I now suspect low effiency speakers have a head start in the measurement stakes?

the main reason for my post is i'm planning some changes to my amp and i want to measure the frequency response before and after.. so its only a reference point...

thanks for the input.

cheers steve..

[NickG]

If you have a meter with a out connector, the software I mentioned will use that as a input, and will give you FR charts, and more info than you need in a few moments. You may be able to find a calibration curve for the meter you use as well.