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Old 7th November 2006, 01:14 AM   #1
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Default Open baffle driver eyeball test

I haunt charity shops, garage sales etc and often see old speaker drivers naked or in boxes, but have no chance to measure them other than by eye and finger press or sometimes multimeter or battery test to check VC.

Can anyone describe the general external appearance of drivers suitable for open-baffle full-range use in terms of such things as cone style, magnet size/type/material, cone suspension surround (rubber, foam, accordian-pleat) or spider type as general guidelines.
I AM aware of the "suck-it-and-see" test, by actually listening to them, but I am trying to avoid buying too many duds. (I have enough already)
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Old 7th November 2006, 12:25 PM   #2
Rudolf is offline Rudolf  Germany
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I can only state some things that IMHO would disqualify a driver for FR on OB:

Drivers with really BIG magnets (relative to cone dia.) tend to have lowish Qts - being bass shy in OB.

A dustcap that is much larger than the voice coil diameter will not properly work as a high frequency radiator - or it might even cover the HF radiating area below.

Thick and heavy cones in conjunction with a fat surround indicate that the designer focused on low frequency.

Metal and plastics cones are much less likely to deliver FR than paper cones.

An accordean pleat suspension in a furniture style box would indicate that the driver is probably FR rather than PA.

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Old 7th November 2006, 04:25 PM   #3
Dumbass is offline Dumbass  British Antarctic Territory
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Drivers that come in something open-backed, like a TV console, stereo cabinet, etc, probably are pretty well-suited to open baffle (because that is essentially what they are in).
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Old 7th November 2006, 05:42 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

Carry a paper clip with you. Get used to tapping the cone of drivers.
Indicates Qms. Now short the terminals and repeat. Indicates Qts.

May help.......

/sreten.
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Old 7th November 2006, 06:05 PM   #5
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sreten,

I like the idea. Perhaps you can elaborate on what he should be listening for?
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Old 8th November 2006, 12:48 AM   #6
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Default FR driver eyeball + tap test + ...

Thanks for all your suggestions.
>>Carry a paper clip with you. Get used to tapping the cone of drivers. Indicates Qms. Now short the terminals and repeat. Indicates Qts.

Thanks sreten. I sortof get your idea-- first tap you assess cone + suspension, second tap with VC shorted you assess damping generated by coil and magnet. Is that the idea? Could you please elaborate on the sounds...

Can anyone suggest a checklist for a "walk by" inspection eg: Lightweight paper cone, Small(ish) or not too large magnet, etcetera. Unfortunately some sellers do not appreciate me tapping their wares. While old console radio spkrs are obvious candidates, they are usually v expensive if still attached to the radios ;-( Finding a matched pair is also difficult. Has anybody had success with drivers from vintage and veteran electric organs?
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