Speaker and room measurement idea

[B-format]

Hi All,

I have an idea to 'build' a grotbox (a poor quality speaker) so that i can A/B my mixes on them for refence. At the moment i tend to do this in the car or bounce a project to my phone, but it would be nice to do this live. There are commercial ones available on the market (Auratone etc) but i thought this could be a fun project.

So, my idea is to get a 6x9 car speaker in a box with amp and go out into a field and take the frequency response, spectral decay measurements etc. This will give me a near anechoic/free field response of the system. Then bring the system back into my workspace and repeat the measurements. My thinking is that the difference between the two will give me my room characteristics which i could eq out of the signal chain to just leave the free field response of the grotbox but inside my workspace (im not trying to get a perfectly flat response, i want the inaccuracy of the grotbox only).

Can anyone see an issue with this method? I did live sound engineering at uni a while back and something is in the back of my head saying i've missed something but i'm more than a little rusty in this area.

Many Thanks

 

[mjwin]

Hi & Welcome to ASR!

If I understand you correctly, what you're attempting to do is to create an "EQ setting" which you can apply to your DAW to simulate the sound of a "grotbox" through your (presumably accurate) studio monitors.

This is ok in principle, but the problem is that a simple EQ setting does not equate to a full simulation of a transducer. You can roughly simulate on-axis response at a specific signal level, but your EQ will not account for level related distortion, off axis response (spinorama curves) nor all manner of other non-linearities which might befall your poor audio signal when actually played through such a device.

If you're going to the trouble of building a "grotbox", why not just wire it up with a length of bell wire, stick it on a shelf somewhere in your studio & connect it up when you need to.

It seems to me that the simplest solution would be the best in this case.

 

[B-format]

Hi thanks for the reply.

I'm think about building one rather than eq my studio monitor. What I'm proposing is essentially eqing the room out of the equation by taking free field measurements before hand. I know the whole eqing the room thing is controversial and will only go so far. Just wondering if it's at all worth it from technical point of view. Basically I'm trying to warrant buying a measurement microphone and messing about with ‍

 

[andreasmaaan]

The problem as I see it is that your ears/brain do not hear what the steady-state in-room measurements show. Your auditory system will quite effectively separate the direct sound from the grotbox from the sound field it generates in the room (especially at mid and high frequencies, and especially for later-arriving reflections), whereas it will only be the sound field that your mic measured in-room.

In other words, your attempts to alter the in-room sound field to match the quasi-anechoic output of the grotbox will result in a direct sound from the grotbox that is very different from its (unaltered) anechoic output - and it is primarily this that your brain will interpret as the grotbox’s sound.