which"driver mounting" method for testing (TS parameters,distortion,response curves) - diyAudio
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Old 10th January 2013, 10:21 AM   #1
Dezza is offline Dezza  Australia
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Default which"driver mounting" method for testing (TS parameters,distortion,response curves)

I have just started learning to use Soundeasy for my loudspeaker projects and would
like to know if I can do the initial testing, including distortion, SPL, TS parameters &
response curves using a suspended driver arrangement,

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or do I need to build a infinite baffle of some kind to mount the drivers ?
I am guessing the suspended method will be suitable for TS parameters but
there will probably be reflections from the tripod resulting in inaccuracies
for the other tests.

What methods are available ?

This is my first hurdle Any suggestions please.
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Old 10th January 2013, 10:41 AM   #2
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for impedance measurements the driver should be in free air. The tripod will work but you may get some error in your measurements because of gravity. ie the cone will be being pulled down by gravity which will affect the measurements somewhat. If the driver will be mounted in an up firing position, then this shouldn't be an issue.

I usually clamp (or screw) the driver to two vertical pieces of wood. They need to be sturdy to ensure minimal vibration. pics attached of the last two T/S measurements that I did. I think for my 10" woofers I mounted them between two saw horses...

Now onto the acoustic measurements. I assume you will be doing these for crossover modelling? If so then you really need to do them mounted in the final enclosure that they will be used in. The baffle geometry will have quite an effect on the final response curve of the finished speaker so you really want to measure that effect if you want to be able to do accurate modeling.

Tony.
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Old 10th January 2013, 12:24 PM   #3
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You can do a response curve like that, but you won't get any lows...

The curves published are all on an IEC baffle, which is spec'd online. Basically a big
flat board of pretty large size, like a sheet of plywood or MDF for example.

I've done free air and T/S by merely hanging the driver in the air by a thick steel wire, like a hook, just to get it away from surrounding objects. Seems to work ok for me.

Personally, I don't try to get too fine with T/S measurements, since the reality of the performance in the box seems to be somewhat different than simulated anyhow. Also only the in box performance really counts.

Also, there is no definitive *single* frequency response measurement, it changes with position no matter what you do.

The closest to "ideal" conditions might be hung in the air outdoors or in a very large building (like a gym). But that doesn't reflect how the speaker is going to be heard.

One thing that messes up frequency response big-time is "floor bounce". That's an in-box, in-room phenomenon.

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Old 10th January 2013, 02:33 PM   #4
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Dezza

I just started with SoundEasy as well so I am going to follow this thread for the info. There is some very good info on this subject If you haven’t seen it here: Zaph|Audio

I would also be interested in what you are using for a computer and a sound card. I have a Dell Laptop and am considering an M-Audio Profire 610 sound card M-AUDIO - ProFire 610 - High-Definition 6-in/10-out FireWire Audio Interface with Octane Preamp Technology and a calibrated Behringer mic from these guys: Cross·Spectrum Labs - Sound | Vibration | Engineering

Thanks
Matthew
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Old 11th January 2013, 04:14 AM   #5
Dezza is offline Dezza  Australia
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Thanks for the tips guys, very helpful. I think I will use the suspended method for TS parameters
& Impedance. some useful information here regarding this method woofertester.com

For measuring distortion and response curves prior to modelling, I think maybe building an infinite
baffle will give me the best result. Of course followed by more testing in the suitable speaker box.

The equipment I will be using is a metabox laptop. I don't think the type of computer matters.
The soundcard is a emu 0404 usb. I don't think you can buy these anymore. My microphone is
a Dayton EMM6 from cross spectrum labs.
I haven't started any testing yet.
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