How to 'measure' subs

I think I am going to have to take 'basic' measurements with my 'basic' instruments. I think solely for comparisons sake it will suffice.
Thanks for all the help Rog/Dref.

Any suggestions for USB preamps? Without costing a fortune.......

Rog Mogale wrote: M Audio fast track

Or something with similar specs.

But in your case where your measurement microphone has its own build in usb sound card then there is no need for one with phantom power, you only need a sound card with an output. So you could just use your pc's build in sound card or maybe a Behringer UCA202 if the on-board sound card is not working properly.

When recording SPL, obviously some drivers handle more power than others.......so how do you get the most out of the driver/cab combo without accidentally cooking the driver? Also what is the preferable signal for measuring SPL? Sine wave sweep? Pink noise? Full range? etc. etc.

SPL or frequency response?

For the latter, a signal high enough to outclass any background noise. A signal low enough to keep the differences of power compression figures between different drivers small. Personally wouldn't go over 100 W/10 mtr.

I prefer pink noise, usually full range, though sometimes band limited for neighbour-sake (on subs).

Best regards

Cubo

RS, are you asking about max. SPL?
If so, most manufactures only estimates this figure (relatively optimistically ).

As far as I am aware of, there is no foolproof way of getting to a drivers limit without exceeding it (if it is unknown). A good place to start is the ratings given by the manufacturer, if you can get it.
Also if you carefully increase the power you feed the driver while measuring the increase in SPL, then you can get a measure of the power compression. This will tell something about how hot the voice coil is getting (you need to know what metal the voice coil is made of, preferably). It will not tell you when the driver is going to fail though, because that depends on the glue, voice coil former material etc.
But if you keep the power compression low then you should be safe in most cases.

As we are talking about subwoofers here, it is very important to keep an eye on the excursion when you try to push your cabs.

I prefer a sine sweep when measuring frequency response.
But band limited pink noise (in the range where the speaker is designed to be used) might be the best if you want to make a real life max. SPL figure. Because excursion, effectivity and impedance differences will have a significant impact on the output and thermal situation.

Thanks for the replies....
For example, if I am testing multiple drivers in a particular cab, let's say the up scaled hog. Some drivers will reach xmax with more or less power than others regardless of what the manufacturer estimates..........due to chamber size and other characteristics of the cab. Yes? There must be a way of measuring this without cooking drivers.

The point at which the different drivers reaches their Xmax depends a lot on how the drivers are build. Of course on how large the Xmax actually is(because of voice-coil lenght and magnetic gab size) but also on the stiffness of the suspension and the motor strength of the driver.
And of course as you state their interaction with the system (your horn). The interaction with the system will also be different from driver to driver. The exact effect will be hard to predict without simulation based on their Thiele/Small parameters.

You are not necessarily going to cook the drivers just because they get past their Xmax.
If you get them past Xmech you will break them though.

Sines waves is the easiest way to reach Xmax with low powers

Santa came early!

interested if the santa come to my home. i just have brought the new laptop. but now no hv money to buy. i think to use the internal soundcard before buy new external usb. guy if measure please post on here.