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November 26, 2021, 03:03:13 PM

Author Topic: FR Testing  (Read 586 times)

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Offline Jamier

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FR Testing
« on: August 14, 2021, 09:13:03 AM »
I’m setting up an amp for FR testing of some speakers. Using a CLIO Pocket. I only need one channel, can I, should I place an 8 ohm resistor across the unused posts, if I am testing an 8 ohm speaker?

Jamie
James Robbins

Offline Paul Birkeland

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Re: FR Testing
« Reply #1 on: August 14, 2021, 10:20:41 AM »
If it's one of our amps, you don't need to.  If it's pretty much anything else, it's not a bad precaution to take!
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jamier

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Re: FR Testing
« Reply #2 on: August 14, 2021, 12:27:47 PM »
So, I’m assuming that, when measuring a Coax, the mic is leveled at the center of the Woofer ( which is also the center of the horn exit)? Right?

Jamie
James Robbins

Offline Doc B.

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Re: FR Testing
« Reply #3 on: August 14, 2021, 01:18:16 PM »
Depends on what you are trying to achieve. A reasonable approach is to measure the speaker in room from the listening position, since that is the position you will be, um, listening from. Expect some HF rolloff in the response curve, that is normal. There will be big bumps below 200Hz from your room modes.

If you want an "actual" frequency response of the speaker take the speaker outside to a wide open, quiet place. Set it up on a ladder to reduce the effects of ground reflections. Put the mic at 1 meter, directly on axis at the tweeter height. Then measure at 15 and 30 degrees horizontally off axis. 
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Jamier

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Re: FR Testing
« Reply #4 on: August 14, 2021, 01:29:42 PM »
So, if I "gate" the response, can I do the measuement inside (?),  I realize it won't reflect what's going on below, around 200Hz, but at this point I'm trying to see what's going on above 200. 200Hz and below will be handled by a separate driver and at that point I will try to do a complete curve. Taking it all outside will require some, well, some significant planning.

Jamie
James Robbins

Offline Doc B.

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Re: FR Testing
« Reply #5 on: August 14, 2021, 04:43:45 PM »
Yes, that will give you a pretty good idea of what the speaker is doing. If you are trying to see the actual response of the speaker as is would be in free air set the mic 1M from the speaker. If you are more interested in tuning the speaker for best response in the room measure at the listening position.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.