HLAM Measurements

[Alleric]

Wading in here because I've got a lot of time in using REW, tuning for an unmovable MLP, multiple subs, et al...


1. Close mic measurements: No, the nulls and peaks will not show on close-mic measurements, because taking the measurement that close removes the effect of room interactions. This is the standard mic placement behavior when recording guitars, bass, etc... mic the speakers in the guitar/bass cabinet super close, get the room out of the frequency and time behavior as much as possible.

2. The null always being there regardless of receiver, processor, amp, whatever... Your main listening position (MLP) is sitting in a null for those frequencies. I think you mentioned your MLP is against a wall? You also mentioned your speaker placement is kind of set in stone? I am in that club. Check out the following three images:

REW_MLP_s.jpg

REW_L_s.jpg

REW_R_s.jpg

The first pic is measured from my MLP, center of my couch. Second shot is the left seat on my couch. Third seat is the right seat on my couch. I have two SVS SB3000's flanking the console that holds my television and front 3 speakers.

Please notice the nulls that happen from each position between 100hz and 153hz. Notice how each seat sees different null behavior. The exception is the 153hz null. That null encompasses my ENTIRE COUCH and I cannot get rid of that because MLP cannot change, speaker location cannot change, subwoofer location cannot change. Regardless, the null patterns moving when you move the mic to any of the seats on my couch is the point. If you have mains speakers that stay in the same place every time, and an MLP that stays in the same place every time, no receiver, no amp, no EQ, is going to remove the null pattern measured at that MLP. Ever.

If you want the null to move or vanish, speakers have to move or listener has to move. But, as you move these things other nulls will show up. The only way to do that is to remove the room interaction via bass traps. Not broadband absorption. Bass traps. Midbass and bass frequencies bouncing off your walls from the fixed speaker position are interacting reflections from those walls with the direct sound that goes in a line from your speaker cones to your microphone. Some of that interaction is heavily out of phase with the direct sound. That's what causes the nulls. You have to live with some of them.

You may notice that my nulls aren't that bad. There's a reason for that. You say you have four subwoofers in the room controlled by a minidsp. I have one of those as well. Two input filter banks, 10 a side, then four output filter banks, 10 each. I am not sure how you have configured yours, but if it was by sub crawl and manual testing, I have a suggestion for you: https://www.andyc.diy-audio-engineer...tml/index.html

You will have to do some very tedious measurements from each of your subs, one at a time, with zero eq or processing of any kind from your receiver or processor. Once you have the measurements from your subs, in REW, you save those in a specific format that the instructions will tell you, and you load those into Multi Sub Optimizer. When you tell it to process them, it brute force checks level, phase and time interaction possibilities using all four of your subwoofers to get them, by themselves, to be as flat in your room as you want. Know ahead of time that because each of your speakers sees your room differently, each of your subs sees your room differently, that the configuration it generate will look possibly completely insane (-30db cuts in certain passbands, etc). Regardless of how crazy the config of each individual sub is... once you get a successful measurement, processing, and config pushed to your minidsp... your subs will be as flat as you can possibly get them in your room.

Prior to using that tool I had a massive room null at MLP at 17.7hz. Prior to using that tool, every null you see on those pictures between 100hz and 153hz was utterly massive. Use the sub optimizer, get your 4-sub-config perfect, then re-visit your whole room measurements, and perhaps give the room correction another try.

This is my MLP full range:

REW_MLP_full.jpg

Sierra 1's, dual SB3000's. In my room, if I turn all room correction off and solo the L and R Sierras? Massive, massive bloom of bass between 32hz and 80. Peak on it is 10db. Some of that is the Sierras, some of that is my room. The subs see it as well.

You have all of the hardware. Now you just need to take the step to tune the room.

Oh, and this site is quite technical, but if you want to learn exactly where your nulls are in your room: https://amcoustics.com/tools/amroc?l...t=true&r60=0.6

Cheers.

[Alleric]

Oh, and for the record my crossover between the mains and subs is 60hz. If I go higher than that, the subs have a null they like to accentuate. If I got lower than that, the mains have a null they like to accentuate. 60hz crossover, optimized subs, room correction on the mains but NOT the subs from the AVR (the minidsp handles it).

REW is a dangerous rabbit hole. There's a lot of effort to digging out from it. Sometimes looking behind the curtain is dangerous.

[Hlam]

Thanks for the detailed post Alleric.
I do not get the time to visit this site very often.
I tried MSO and did not get any improvement. I have not tried it in the last 3 or 4 years though.
Bass traps and other room treatments are out of the question. This is a living room setup.
I get the best sound out of my system by using REW to EQ the subs and no other REQ on the speakers.
What smoothing do you use on your graphs?
I have listened to more test tones than music in the last 5 years. I think that that is kind of sad to say.
I got a lot of enjoyment out my systems before I had all of these tools to help improve my listening experience.
I purchased my first system back in the 70's and thought that it sounded wonderful. Ignorance was bliss. You could drop a needle on a record or plug in an eight track and enjoy some tunes. You younger folks may have to google that last one, LOL.

[racrawford65]

Eight track - I remember those! Parents car had a player.

[Alleric]

Thanks for the detailed post Alleric.
I do not get the time to visit this site very often.
I tried MSO and did not get any improvement. I have not tried it in the last 3 or 4 years though.
Bass traps and other room treatments are out of the question. This is a living room setup.
I get the best sound out of my system by using REW to EQ the subs and no other REQ on the speakers.
What smoothing do you use on your graphs?
I have listened to more test tones than music in the last 5 years. I think that that is kind of sad to say.
I got a lot of enjoyment out my systems before I had all of these tools to help improve my listening experience.
I purchased my first system back in the 70's and thought that it sounded wonderful. Ignorance was bliss. You could drop a needle on a record or plug in an eight track and enjoy some tunes. You younger folks may have to google that last one, LOL.

1. MSO is quite finicky. I lost count of the number of runs I did on it, with various filter configs, to get what I wanted. It's a pain in the butt, but once you hit a config that works it immediately becomes worth it. I only run 2 subs, so I ran my simulations with 10 input filters, 10 output filters, so 20 filters per sub. So 20 filters, with various SPL normalization strategies concerning frequency range, SPL compliance, whether to take the mains into consideration or not. It's a ton of trial and error both on the theory side and the implementation side. But I don't get that response under 60hz in this massive room without it.


2. I don't use bass traps either, but then my jaggies aren't that bad. I have a friend who has FAR more annoying nulls in his room between 100-200. Because of the shape of my room, I functionally have no side walls flanking my listening positions. The only early reflections I get are from the floor an ceiling. On the floor I have a massive shag rug That is wider than my front sound stage. So I have the normal null chatter up past 1k, but not too much more to really worry about.

3. My subs are time-aligned, phase-aligned, EQ'd and gained within an inch of their lives. My mains and surrounds? Whatever Audessy MultEQ-X scanned out and then I think it's like 5 parametric filters on L/R, 3 or so on C, and nothing on the surrounds. I'm just generally smoothing things out. All of my graphs are variable smoothing, but I can re-post anything with any smoothing level you'd like.

4. I got started in audio listening to Bugs Bunny LP's on my parents' Magnavox console stereo. My first "real system" was a rack setup and two cheap towers from JC Penny. My first really-real system was a Pioneer receiver and a couple of Pioneer CS-G403's when I went off to college. No time correction, no EQ, no phase alignment, no T60. I still think ZZ Top's "La Grange" only sounds correct on a pair of 6x9's in the rear deck being pushed by a Sparco 50 watt "Power booster". Is it clean? Nope, but it's correct.

[davef]

I get the best sound out of my system by using REW to EQ the subs and no other REQ on the speakers.
What smoothing do you use on your graphs?

Yes, in most cases it is best to only EQ bass.

I have listened to more test tones than music in the last 5 years. I think that that is kind of sad to say.
I got a lot of enjoyment out my systems before I had all of these tools to help improve my listening experience.
I purchased my first system back in the 70's and thought that it sounded wonderful. Ignorance was bliss. You could drop a needle on a record or plug in an eight track and enjoy some tunes. You younger folks may have to google that last one, LOL.

This is a very good point that I try to explain to most consumers these days. Since decent hobbyist level measurement software is available to everyone, a trend has developed towards achieving "perfection" with in-room measurements. This leads to constant tweaking, constant changes and it isn't what this awesome hobby is meant for. It takes away from the enjoyment of the system.

We go to a live concert, we enjoy - we don't think about measurements. Believe it or not, I do not use EQ on any of my systems, including our demo room (we have bass traps and room treatments, but zero EQ). I recommend you kick back and enjoy your system

[Alleric]

Yes, in most cases it is best to only EQ bass.



This is a very good point that I try to explain to most consumers these days. Since decent hobbyist level measurement software is available to everyone, a trend has developed towards achieving "perfection" with in-room measurements. This leads to constant tweaking, constant changes and it isn't what this awesome hobby is meant for. It takes away from the enjoyment of the system.

We go to a live concert, we enjoy - we don't think about measurements. Believe it or not, I do not use EQ on any of my systems, including our demo room (we have bass traps and room treatments, but zero EQ). I recommend you kick back and enjoy your system

Or trying to EQ to some standard, be it flat, some house curve, whatever. Or seeing every null or peak as something that can and should be conquered. You want the best sound you can get in your home, not the best sound you can get in an anechoic studio live room.

And frequency response is not the end-all-be-all of speaker attributes.

[MDinno]

Oh, and for the record my crossover between the mains and subs is 60hz. If I go higher than that, the subs have a null they like to accentuate. If I got lower than that, the mains have a null they like to accentuate. 60hz crossover, optimized subs, room correction on the mains but NOT the subs from the AVR (the minidsp handles it).

REW is a dangerous rabbit hole. There's a lot of effort to digging out from it. Sometimes looking behind the curtain is dangerous.

So what is one suppose to do if there is no 60HZ option available on their AVR? It's either 80 or 50 with my Pioneer Elite. Would sealing the port on the speaker compensate for easier integration between sub and speaker??

[racrawford65]

So what is one suppose to do if there is no 60HZ option available on their AVR? It's either 80 or 50 with my Pioneer Elite. Would sealing the port on the speaker compensate for easier integration between sub and speaker??

IMO, the issue / cross-over setting that Alleric describes is based on his room and equipment. Others may or may not have similar issue. I wouldn't seal / damp the speaker port unless the manufacturer confirms it is ok - could introduce more problems. If x-over limited, moving speakers and/or sub and/or listening position a bit could help correct. Or, a good reason to upgrade the AVR :-)

[MDinno]

IMO, the issue / cross-over setting that Alleric describes is based on his room and equipment. Others may or may not have similar issue. I wouldn't seal / damp the speaker port unless the manufacturer confirms it is ok - could introduce more problems. If x-over limited, moving speakers and/or sub and/or listening position a bit could help correct. Or, a good reason to upgrade the AVR :-)

I already upgraded my AVR with the Pioneer SC-LX 704. I'm looking at the LX right now to upgrade my speakers. It's probably not a big deal to cross them at 80 when I think about it. It's not a brick wall so the advantages the speaker has under 80 will still be there.