Is something wrong with my Center speaker? REW measurements included. - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 17 Old 02-14-15, 12:13 AM Thread Starter
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Is something wrong with my Center speaker? REW measurements included.

Sorry if this is the wrong forum for this post but I'm hoping people more experienced in reading REW would be more likely to see this post than in the main Speaker forum. Mods move if needed please.

I've measured my MartinLogan Motif and personally I feel like there's something off about the frequency response but when I contacted ML about it they said nothing was wrong.

Measurement I sent to ML:


ML Response:
Quote:
At first glance it would not appear that there is anything wrong with the Motif. I don’t see anything to indicate a non-working or out of phase driver in the speaker. Please note the following:



1. The “On Wall” position on the back of the Motif will reduce the speakers output by 3 to 5 dB below 500 Hz. You might experiment with this switch to see what gives you the best results, regardless of the placement of the speaker.

2. This response might suggest more of an issue with surfaces in proximity to the speaker that could possibly cause some phase cancellations. ( IE, reduced output between 240 and 700 Hz.) Or it may be simply an issue with trying to get an accurate measurement in your particular space. With panel speakers sometimes you can get a more accurate reading by measuring slightly off axis ( say 20 to 30 degrees).

3. I would also check the settings in your processor or receiver. In general you would want the center set to “small”, but again experiment and see what sounds best to you.



In short, if everything sounds ok, it probably is ok. Go with what sounds best to your ears regardless of any graph that may be generated.
I dunno, that 240hz to 700hz looks wonky to me, I know a narrow dip isn't that audible but man it really drops off over a large band IMO.

So I did some more measurements:

On/Off Wall switch changes:


Off Center Measurements:


My Motif was a refurb so that adds to my doubt. I know it's different speakers and placements but I don't notice any of my other ML speakers having that behavior and for comparison my previous center, ML Encore TF:


Anyone have any ideas? Am I just over thinking it? I know it'll never be "flat" but to me it looks either defective (like I said it was a refurb so it fuels my doubt) or intentional and due to ML response it makes me believe they tuned them this way.

Thinking back on it I didn't measure with the phase reversed. I should measure it like that. Anyhow I can get the mdat if needed too.

Thanks!
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post #2 of 17 Old 02-14-15, 12:35 AM
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Re: Is something wrong with my Center speaker? REW measurements included.

I agree, it does not look right to me. That is definitely an audible deficiency, not explainable by wall proximity, and I cannot imagine anyone saying it was normal.
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post #3 of 17 Old 02-18-15, 01:15 AM Thread Starter
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Re: Is something wrong with my Center speaker? REW measurements included.

Thanks for the reply. I thought it might've been a ceiling reflection at first but after changing the position and off center measurements prove that it's not. I should email them the extra info but given their first reply basically reducing it down to "In short, if everything sounds ok, it probably is ok. Go with what sounds best to your ears regardless of any graph that may be generated." doesn't really give me the best vibes about it.
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post #4 of 17 Old 02-18-15, 11:09 PM
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Re: Is something wrong with my Center speaker? REW measurements included.

A ceiling reflection, or any single reflection, will not cause a frequency response disruption that dramatic. Try a close-up (4 to 6 inches away) measurement straight on-axis for each driver. You should see the crossover frequencies clearly, and the response for each driver should be very flat over its active frequency range.
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post #5 of 17 Old 02-19-15, 01:19 AM Thread Starter
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Re: Is something wrong with my Center speaker? REW measurements included.

I emailed ML the other graphs and they set up an RMA for testing. I'll have to try those measurements before sending it out. From my knowledge of audio I'm thinking the crossover might have a issue like one of the components is bad/out of spec but I'm not very knowledgeable about passive crossover design. I haven't measure a lot of speakers but the ones I have do not have a dip that broad and odd at the crossover points, usually it seems to be a sharp narrow dip. The crossover freq are 450 & 4000 Hz. My other thought about it is the problem of horizontal MTM style centers having lobing issues despite this being more of WMTMW (I suppose since the panel is so wide). Measuring them in the way you suggest should at least show me if it's a lobing issue. I guess I know what I'm doing after work in the morning LOL.
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post #6 of 17 Old 02-19-15, 08:34 AM Thread Starter
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Re: Is something wrong with my Center speaker? REW measurements included.

Quote:
AudiocRaver wrote: View Post
Try a close-up (4 to 6 inches away) measurement straight on-axis for each driver. You should see the crossover frequencies clearly, and the response for each driver should be very flat over its active frequency range.
Here are those measurements, I clipped the tweeter but I'm not that interested in that measurement too much at the moment...



I averaged it just for fun...


That's ideally more or less what I guess what it "should" be.

mdat: https://www.dropbox.com/s/2iz5s84tz8...vers.mdat?dl=0
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post #7 of 17 Old 02-19-15, 02:03 PM
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Re: Is something wrong with my Center speaker? REW measurements included.

Thanks for including the .mdat file, that is helpful. Looking at the more recent measurements included in that file, they do appear much closer to what would be expected for that kind of design.

Interesting that the big drop from 200 Hz to 300 Hz does not appear in these measurements. Without it, the remaining anomalies in the earlier measurements are more explainable as cancellations from reflections. Don't know exactly what is different about the measurements, but the later ones do appear fairly normal.
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post #8 of 17 Old 02-20-15, 12:31 AM Thread Starter
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Re: Is something wrong with my Center speaker? REW measurements included.

I've merged all the previous measurements other than the one from measuring the drivers individually into a single mdat and with proper notes:

https://www.dropbox.com/s/ef3atr8zfc...ents.mdat?dl=0

I can do more if you have any suggestions before I send out my center as I don't want to end up paying for shipping and finding out that it was just fine and some anomaly in my measuring. My room is about 12.5 feet wide, 20ft long, and 8ft high. The biggest two things of note is that the first and oldest measurement was done with a CSL Dayton UMM-6 measured on top of the TV about 53" off the floor and the crossover was set to 80hz. I sold the UMM-6 and got a CSL miniDSP UMIK-1 (in case I ever went with one of miniDSP's Dirac products) so all other measurements were done with the UMIK and below the TV on a stand about 10" off the floor and the crossover is set to 100hz.

Last edited by |Tch0rT|; 02-20-15 at 12:53 AM.
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post #9 of 17 Old 02-20-15, 05:55 AM
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Re: Is something wrong with my Center speaker? REW measurements included.

Is the speaker inside a cabinet or entertainment center of some type?

Regards,
Wayne



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post #10 of 17 Old 02-20-15, 07:48 AM
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Re: Is something wrong with my Center speaker? REW measurements included.

Quote:
|Tch0rT| wrote: View Post
I've merged all the previous measurements other than the one from measuring the drivers individually into a single mdat and with proper notes:

https://www.dropbox.com/s/ef3atr8zfc...ents.mdat?dl=0

I can do more if you have any suggestions before I send out my center as I don't want to end up paying for shipping and finding out that it was just fine and some anomaly in my measuring. My room is about 12.5 feet wide, 20ft long, and 8ft high. The biggest two things of note is that the first and oldest measurement was done with a CSL Dayton UMM-6 measured on top of the TV about 53" off the floor and the crossover was set to 80hz. I sold the UMM-6 and got a CSL miniDSP UMIK-1 (in case I ever went with one of miniDSP's Dirac products) so all other measurements were done with the UMIK and below the TV on a stand about 10" off the floor and the crossover is set to 100hz.
Thanks for the additional mdat file and all the additional detail about the measurements. With all the additional detail in mind, it does appear that the unit could be in spec and that the frequency response variations are explainable by cancellations from reflections. To experiment with seeing the difference a floor reflection can make, for instance - it is an experiment only, not at all practical for normal use, but it can help you see if your speaker is behaving - it takes several layers of thick, fluffy blanket with each layer further thickened by bunching and wrinkling it, all precisely placed to eliminate a floor reflection.

Based on your most recent info, I would probably not return the speaker, but of course that is your call.
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