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[George Reiswig]

I am having a hard time finding EASE/GLL data for my speakers, so I'm thinking about learning to make these measurements myself using Open Sound Meter software, my UA Apollo interface and...well, that becomes question #1.

1. I have a choice of microphones I could use: I could use an Avenson STO-2 mic, but since most of the test setups that I see are done outside, with the mic on the ground, it got me wondering if one of my Crown PZM-30FS mics might not be as good or better in some regards because of the PZM part? Or is that just introducing another variable that I should not?

2. Is there an established standard for this measurement that would make my measurements more helpful to others? E.g. what decibel level is registering at the mic, what distance from the speaker the mic is placed, etc.?

I want to make (or obtain) measurements for my dB Tech IG4T speakers, my Bassboss VS-21 Mk2, and my Electrovoice PXM-12XMP speakers. I managed to find the data for my Yamaha DXR-10s on their web site.

Thank you!

[Rob Timmerman]

dB has a GLL for the Ingenia IG4T available for download on the product page: https://www.dbtechnologies.com/docs/299/2349/IG4T_EF3_V1.1.gll.zip (one of the downloads at https://www.dbtechnologies.com/en/products/ingenia/ingenia-ig4t/ )
 
The official measurement guidelines that are used in creating GLL files are published at https://www.afmg.eu/en/we-are-loudspeaker-company-do-you-have-measurement-guidelines-creating-loudspeaker-data-files-gll

[George Reiswig]

dB has a GLL for the Ingenia IG4T available for download on the product page: https://www.dbtechnologies.com/docs/299/2349/IG4T_EF3_V1.1.gll.zip (one of the downloads at https://www.dbtechnologies.com/en/products/ingenia/ingenia-ig4t/ )
 
The official measurement guidelines that are used in creating GLL files are published at https://www.afmg.eu/en/we-are-loudspeaker-company-do-you-have-measurement-guidelines-creating-loudspeaker-data-files-gll

Thank you very much, Rob!

[John Schalk]

It is frustrating when you can't find GLL files for your own speakers but you're in luck in that dB Tech has a GLL file for your main PA speaker.  As far as subwoofers are concerned, unless you are wanting to look at the prediction in EASE Focus for a specific sub frequency at a specific point (listener) in your design, you can use a GLL file for a sub that is of the same general type.  Frankly, since you only have one main subwoofer (for now!) I'm not sure how much predicting you need to do The sub is going to go in the center, if space allows, or on one side if it doesn't.

If you are interested in modeling different subwoofer deployments then I recommend using Meyer's MAPP 3D software.  Meyer's 900 LFC is a front loaded, single 18" powered subwoofer so it makes a nice building block for trying out spaced pairs versus center clusters as well as more complex designs.  The acoustic principles are the same since your sub is also a front loaded (vented box) speaker.  Sure, the actual frequency response and SPL levels will be different, but the interactions of multiple boxes will be the same.

[George Reiswig]

I think looking for GLL files likely is not what I thought it was. In any case, I don’t have PC’s so I’m having a hard time viewing the files anyway.

What I am really trying to do is phase- and time-align my sub to the mains, and try to ensure they are working together properly. My thinking is that if I can establish a baseline measurement that applies to when they are equidistant from the listener, then I could apply additional delay based on distance and temperature in the field.

Another thing I thought of that may make this point moot is that I might need to test this with the mixer and whatever effects (e.g. EQ) applied, in case that is affecting phase by adding latency. IDK.

[Frank Koenig]

What I am really trying to do is phase- and time-align my sub to the mains, and try to ensure they are working together properly. My thinking is that if I can establish a baseline measurement that applies to when they are equidistant from the listener, then I could apply additional delay based on distance and temperature in the field.

If that's all you want to do one of the ~$100 measurement mics from Rational Acoustics or Parts Express will do fine. Lay it down on a piece of flat material (plywood) to keep it out of the dirt. You're dealing with 10 ft wavelengths so it's not too critical. The bigger problem is your measurements getting confounded by nearby reflecting surfaces.

I use the Rational Acoustics mic for this and keep the good measurement mic at home. BTW, except for the top octave, where the cheap mic is a little hot, they match almost perfectly.

Establishing a "reference delay" is exactly what I do. Saves time and is good enough for throw and go.

--Frank

[John Schalk]

I think looking for GLL files likely is not what I thought it was. In any case, I don’t have PC’s so I’m having a hard time viewing the files anyway.

What I am really trying to do is phase- and time-align my sub to the mains, and try to ensure they are working together properly. My thinking is that if I can establish a baseline measurement that applies to when they are equidistant from the listener, then I could apply additional delay based on distance and temperature in the field.

Here is a link to Merlin's subwoofer alignment process.  He shows how to perform an alignment "at the shop" to set a baseline which you can then adjust for distance out in the field.  He has helpful videos for each step in the process too.  I would recommend having your mixer included in the measurement path if it is performing any DSP functions.  For instance, I mix on the X/M 32 platform, and I use the polarity and delay features on the Outputs of the mixers to do my alignments so I include my X32 Rack in the signal path when I am checking my system's alignment in my driveway.

https://www.merlijnvanveen.nl/en/study-hall/166-subwoofer-alignment-the-foolproof-relative-absolute-method

[Frank Koenig]

I'll add that in a pinch, if you're in a small room lousy with modes, you can get a decent sub alignment using nearfield measurements. The magnitude may be off but the phase will be close enough and a whole lot better than nothing. Place the mic alternately between the grilles of the sub and the LF part of the top and carry on as unusual. Apply additional delay as needed based on the sub-top distance difference at the listening position.

--Frank

[George Reiswig]

Thank you to everyone for contributing here. I’ve managed to start capturing some data that seems to show good coherence.

I still am curious as to whether a good PZM might be a good way to do these baseline captures, versus placing a measurement mic on the ground? Maybe at the wavelengths we are talking, boundary effects of the ground on a measurement mic don’t really matter? 

[George Reiswig]

Thank you to everyone for contributing here. I’ve managed to start capturing some data that seems to show good coherence.

I still am curious as to whether a good PZM might be a good way to do these baseline captures, versus placing a measurement mic on the ground? Maybe at the wavelengths we are talking, boundary effects of the ground on a measurement mic don’t really matter?

So I did a bit of an experiment, using my Avenson STO-2 as the measurement mic, and a Crown PZM-30S as the reference signal. Up to about 2kHz, they were in excellent agreement. And I know the Crown is not flat above that point. So...I guess it doesn't matter, really.

[ProSoundWeb Community]