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Multi-Way Conventional loudspeakers with crossovers

Midrange depression in room response
Midrange depression in room response
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Old 29th March 2020, 06:09 AM   #1
MtBiker is offline MtBiker  United States
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Default Midrange depression in room response

I recently finished building a new set of active 3 ways and am happy with v1.0 of the crossover, but need some advice on the room response.

The red trace is one 3way speaker from 20" run full range. The light blue trace is from the listening position and is crossed over to a sub at 80Hz. My question is what to make of the depression between 200Hz and 1kHz at the LP. I took measurements along the couch and the width of the depression narrows as you you move along the couch, but never goes away 100%. Filling it in with EQ sounds subtly wrong.

Does everyone EQ the modal region and then forget ignore everything above it?
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Old 29th March 2020, 07:11 AM   #2
Douglas Blake is offline Douglas Blake  Canada
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Quote:
Originally Posted by MtBiker View Post
I recently finished building a new set of active 3 ways and am happy with v1.0 of the crossover, but need some advice on the room response.
What are the crossover points on your speakers?

If you look closely you will see a dip in both graphs at about 160hz also at the 1k region on both there is an exaggerated rise in output leading into the highs. On a 3 way system that could represent a phasing issue in the crossover regions between your woofer-mid and mid-tweeter. Whether that is true here or not would depend on your crossover frequencies.
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Old 29th March 2020, 08:19 AM   #3
TNT is offline TNT  Sweden
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If you have a low crossover to LF and a narrow baffle you are suffering from increased poor coupling of the midrange. This together with the out of phase floor bounce could be the reason for this.

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Old 29th March 2020, 09:05 AM   #4
fatmarley is offline fatmarley  England
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How do they sound? I had a similar dip in my speakers (when measured near-field though). Michael Jackson - Man in the mirror, sounded very different compared to my headphones. Vocals were grey or dry sounding.
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Old 29th March 2020, 09:53 AM   #5
giralfino is offline giralfino  Italy
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Quote:
I recently finished building a new set of active 3 ways and am happy with v1.0 of the crossover, but need some advice on the room response.
It's hard to diagnose without a proper measure. You really need to perform a gated FR measure, in a moderate sized room you should be able to attain 200Hz precision or even better, and then you'll easily see if the FR is really flat or not. I suspect you didn't account for baffle step loss.

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Old 29th March 2020, 10:22 AM   #6
AllenB is offline AllenB  Australia
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Midrange depression in room response
Quote:
Originally Posted by MtBiker View Post
Filling it in with EQ sounds subtly wrong.

Does everyone EQ the modal region and then forget ignore everything above it?
This is useful information. Irregularities at the listening position can be an indicator of a problem. Sometimes you can EQ to it and sometimes you cannot. It depends on the issue.

I agree with the others that there needs to be more information. In addition to what's been said I'd ask for a photo and/or a description of the speaker.
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Old 29th March 2020, 11:25 AM   #7
chris661 is offline chris661  United Kingdom
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It seems very odd that there'd be such a broad-band effect. Normally, acoustic issues will tend to show up at a particular frequency, maybe with a few harmonics: floor bounce etc.

A near-perfect 6dB loss across two octaves is quite impressive, really.


An alternative theory would be that you're using dipole mid/bass and monopole HF with a ~1kHz crossover. The room excitation would vary according to frequency. With some broad-band absorption behind speakers of that description, I can imagine getting similar response curves.

Knowing what the speakers are would help. Taking the sub out and running the speakers full-range would also be informative.

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Old 29th March 2020, 12:44 PM   #8
scholl is offline scholl  United States
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Can you take the speakers outside to measure? Might help to discern a room or speaker problem.
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Old 29th March 2020, 05:38 PM   #9
MtBiker is offline MtBiker  United States
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I started off doing gated measurements with Holm, but was getting nearly identical results with REW and was tired of the two apps fighting over ASIO control, so I abandoned Holm once I felt comfortable with the correlation between the two apps. The only obvious benefit with Holm was that it provided smoother FR near 1kHz.

The first pic is series of outdoor measurements comparing of BSD for
  • The midrange from Edge in red
  • The actual 2ft measurement in blue
  • 2ft spliced to ground plane in green
  • 1cm comparison

My theory for the discrepancy between Edge and reality is the baffle is slightly curved and has huge roundovers, so the shape is correct, but reality is shifted up in frequency. That and the fact that other investigations I have seen of BSD don't agree with Edge.

The crossover points are 1.6kHz, 250Hz, 80Hz, all LR4.

I am happy enough with my midrange measurements and I get a decent reverse null at 1.6kHz, but my GP woofer measurements don't show much baffle step (maybe that's just closer proximity to ground?) and I don't measure a good reverse null at 250Hz (at least indoors).

The time delays for T-M-W were set using measurements taken at 6ft, and the delay to Subs determined with a measuring tape and confirmed to provide smoothest FR with various delays at the LP.

I can take the speakers back outside eventually, but it's a big affair and the weather has to be cooperative. I ran out of daylight last time.

Maybe the midrange suckout in the room response is just a result of reflections. The 2nd photo is various positions along our long couch, taken before EQing out room modes below 100Hz.
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File Type: png 321 Mid BSD comparison.png (49.4 KB, 169 views)
File Type: png 328 LP center to corner.png (72.4 KB, 167 views)
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Old 29th March 2020, 08:18 PM   #10
MtBiker is offline MtBiker  United States
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