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Author Topic: Bet nobody's asked something like this before :)  (Read 1868 times)

Matt Ion

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Bet nobody's asked something like this before :)
« on: February 16, 2011, 05:38:11 pm »

Howdy, all... boy, haven't been around here since, oh, about the heyday of the Mixerman saga, and my, how the place has been spiffed up!

Couldn't really find a section specifically appropriate to this question, and this one seemed to be the most "generic", so hopefully this will be the right place for what's probably a unique, but still audio-related question...

We've been doing drive-thru intercom systems for years (primarily CCTV, some access controls), but I've run into a situation here that the boss doesn't have an answer for, and with my audio background (two-year audio engineering post-secondary program, several years working with live and studio audio), I've been charged with "just making it work".

Pretty basic setup: drive-thru order intercom, speaker post by the menu board (about 6"x6"x3' high, on a base and the curb), single speaker at about car-window height (5.25" speaker is about 3.5'-4' from the pavement), half-duplex operation, induction loop in the driveway, and a 3M D-15 intercom base and loop detector in the store.

Problem is, the speaker works TOO well when functioning as a mic, and picks up as much car/engine/traffic noise as it does voices... although it seems to be very selective, particularly to frequency - some voices come through clearly, others are drowned out be ambient noise.  This is an issue with almost all drive-thru setups, but this one seems especially bad.  The cone having gotten wet and not being a particularly weatherproof design seems to have made it really frequency-selective as well.

Anyway, my thinking is, I need to make the speaker more "directional", whether by putting a tube in front of it, or whatever... a horn type of idea, except I don't think your typical compression driver would work that well as a mic.  My audio theory is almost 25 years behind me, so I'd be hard pressed to actually do the necessary calculations today.

That, or see if the base will support a separate mic and speaker, and add some sort of directional (hypercard or better) mic to the post... waiting to hear back from 3M on that, but I suspect it's a non-starter.

Anyone got any other ideas??? 

Many thanks in advance!

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Art Welter

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Re: Bet nobody's asked something like this before :)
« Reply #1 on: February 16, 2011, 06:23:49 pm »


Pretty basic setup: drive-thru order intercom, speaker post by the menu board (about 6"x6"x3' high, on a base and the curb), single speaker at about car-window height (5.25" speaker is about 3.5'-4' from the pavement), half-duplex operation, induction loop in the driveway, and a 3M D-15 intercom base and loop detector in the store.

Problem is, the speaker works TOO well when functioning as a mic, and picks up as much car/engine/traffic noise as it does voices... although it seems to be very selective, particularly to frequency - some voices come through clearly, others are drowned out be ambient noise.

Anyway, my thinking is, I need to make the speaker more "directional", whether by putting a tube in front of it, or whatever... a horn type of idea, except I don't think your typical compression driver would work that well as a mic.  My audio theory is almost 25 years behind me, so I'd be hard pressed to actually do the necessary calculations today.

That, or see if the base will support a separate mic and speaker, and add some sort of directional (hypercard or better) mic to the post... waiting to hear back from 3M on that, but I suspect it's a non-starter.

Anyone got any other ideas??? 

Many thanks in advance!
Loudest noise at the microphone wins, built in compression may lower the less loud voice information too low to hear.

A speaker makes a sensitive microphone with peaky response, why some voices come through clearly, others don't.

Directionality won't help much, the range of the talker can vary over a wide angle (SUV to sports car, stopping to far forward or back) so it would help some if the talkers are on axis, and hurt if they aren't.

There is a huge difference between a cheesy speaker/microphone and a good microphone. The $1.70 microphone in almost any telephone answering machine or telephone would probably sound better than a very good speaker/microphone.
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ProSoundWeb Community

Re: Bet nobody's asked something like this before :)
« Reply #1 on: February 16, 2011, 06:23:49 pm »


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