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Author Topic: RTA shows big drop at 1.25khz  (Read 20523 times)

Tim McCulloch

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Re: RTA shows big drop at 1.25khz
« Reply #10 on: July 18, 2012, 09:32:36 am »

I use a Phonic PAA3.  If I remember correctly I think that it will do some sort of test for phase.  I will have to get my manual out and take a look.  Thanks -  Brian

You are confusing phase with polarity.
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Samuel Rees

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RTA shows big drop at 1.25khz
« Reply #11 on: July 18, 2012, 10:05:01 am »

Is anyone else not concerned that there is a BBE Sonic Maximizer in the signal chain while RTA/tuning a speaker? Not to mention that it doesn't "delay" the high or low frequencies?
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Brian Wombaugh

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Re: RTA shows big drop at 1.25khz
« Reply #12 on: July 18, 2012, 10:22:02 am »

I talked to a tech at BBE and he told me that the unit needs to be on and included in the RTA process to get an accurate reading of what is actually being heard.  I do not know a lot about how this unit processes sound, but I will tell you the sound is much clearer and crisp with the unit in the on position.  I will try bypassing the unit and see if the 1.25 drop is still there or is less severe.  Thanks -  Brian
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Timo Beckman

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Re: RTA shows big drop at 1.25khz
« Reply #13 on: July 18, 2012, 12:07:04 pm »

Is anyone else not concerned that there is a BBE Sonic Maximizer in the signal chain while RTA/tuning a speaker? Not to mention that it doesn't "delay" the high or low frequencies?

I have worked for the dutch distributor for BBE a really long time ago (+15years ago) . Indeed it would be the first to get rid of but i think it's there to "fresh-up" the sound and should not have anything to do with the allignment of the loudspeakers within the cabinet .
By the way when you do the RTA thing are both sides playing or just 1 side ? And do you have the same response on both sides of your set-up ?
« Last Edit: July 18, 2012, 12:10:14 pm by Timo Beckman »
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Brian Wombaugh

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Re: RTA shows big drop at 1.25khz
« Reply #14 on: July 18, 2012, 12:28:44 pm »

Both sides are playing and the response is about the same in various areas of the sanctuary - give or take a little either way.   Thanks - Brian
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Kevin McDonough

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Re: RTA shows big drop at 1.25khz
« Reply #15 on: July 18, 2012, 01:31:01 pm »

hey

In terms of the sonic maximiser, if the OP plans to us this in his gigs all the time then its probably best he EQ's his system with this in place, so he gets a flat response with this included.

However adjusting this unfortunately wont help you with fixing your problem. Any changes you make in delay or phase will be before the crossover, and so be applied to both drivers. You need to apply a change to one driver only, AFTER the crossover. Ideally this would inside an active crossover, but as its passive you have far less options.

Someone suggested changing polarity and that's a good idea to try, but again as its a passive crossover the only way to do this is to unscrew the front from the cabinet and swap over the wires on either one of the drivers. I would suggest the compression driver because if you swap the woofer you may then run into problems down the line of its bottom crossover now being out of polarity with subs. But that's another thing you'd probably want to measure and investigate.


k


« Last Edit: July 19, 2012, 09:26:17 am by Kevin McDonough »
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Doug Fowler

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Re: RTA shows big drop at 1.25khz
« Reply #16 on: July 18, 2012, 02:19:12 pm »

I use a Phonic PAA3.  If I remember correctly I think that it will do some sort of test for phase.  I will have to get my manual out and take a look.  Thanks -  Brian

Most likely, the popper will report negative polarity in HF if it is wired correctly.  I have seen those things mis-used SO many times, with the user blindly accepting the result.

If the HF is controlled by a passive third order crossover, the popper should report "incorrect" when it is indeed correct.
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Timo Beckman

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Re: RTA shows big drop at 1.25khz
« Reply #17 on: July 18, 2012, 02:20:08 pm »

I sugested to reverse polarity (the high's most likely) but if it's a passive x-over within the cabinet he has to take the high driver out of it and reverse the wireing on it .
Again i'm guesing but al depends on what kind of filters are in there .
Again without measurement data there's no way to tell what's happening ....
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Doug Fowler

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Re: RTA shows big drop at 1.25khz
« Reply #18 on: July 18, 2012, 02:26:22 pm »

I sugested to reverse polarity (the high's most likely) but if it's a passive x-over within the cabinet he has to take the high driver out of it and reverse the wireing on it .
Again i'm guesing but al depends on what kind of filters are in there .
Again without measurement data there's no way to tell what's happening ....

It's an inexpensive passive loudspeaker. I agree, swap polarity in HF.

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Jay Barracato

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Re: RTA shows big drop at 1.25khz
« Reply #19 on: July 19, 2012, 06:51:30 am »


Again without measurement data there's no way to tell what's happening ....


My initial thought based on a negative result was that the OP is seeing the result of a cancellation due to mic/speaker positioning, especially since he later said he was measuring with both sides of the system on. The fact that the response does not change with eq supports that this is an interference issue. The cancellation he is seeing may be the first where the cancellation is as wide as the band measured on the RTA. The cancellations that are at higher frequencies would be narrower than the resolution of the RTA bands and would be averaged with the constructive interference before being displayed.
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Jay Barracato

ProSoundWeb Community

Re: RTA shows big drop at 1.25khz
« Reply #19 on: July 19, 2012, 06:51:30 am »


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