2 subs and oh man I give up....(music 2 channel)

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MONKEYWICKEDMONKEY

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2 subs and oh man I give up....(music 2 channel)
« on: 21 Aug 2020, 06:04 pm »
My room is an open room. Its bad for bass.  So I bought 2 subs (Rythmik L12's). Using AudioTools (iPhone) and the Dayon calibrated mic I started running sweeps.

Room
https://i.imgur.com/f9EP4xH.jpg

Sub behind couch (main listening position)


Sub on front wall in top left corner


The plots are subs only, no mains. Suggestions on where else to try to place them? I recently tried inside the right speaker and the first sweep I did was excellent but subsequent sweeps looked more  like these.

Does volume make a difference?

Also, is there a treatment that would also help with this?


JWL.GIK

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #1 on: 21 Aug 2020, 06:11 pm »
The bottom graph looks better than the top. Keep in mind we're only really concerned from teh crossover frequency on down, usually around 80Hz or so. What it does above there is less critical.

If you have 2 subs, there are some strategies you can use to use cancellations in your favor to get a flatter response. Details in this article on my blog.

MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #2 on: 21 Aug 2020, 06:28 pm »
Thanks, yeah I have been trying those out as best I can. I have the subs set at 60hz with a 12db slope. Front wall phase at 0 and rear wall at 180.

Given my room, some of the strategies aren't workable. Whats weird is they all look super similar. No matter what I do so I wondered about treatments.

Early B.

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #3 on: 21 Aug 2020, 07:34 pm »
Experiment with placement. A sub behind a couch doesn't seem like a viable option. Try both subs near the front wall.

Mike-48

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #4 on: 21 Aug 2020, 08:15 pm »
I agree with others that you'll have to experiment. James's link gives some ideas. I also agree that the 2nd graph looks better.

According the the Rhythmik site, your subs have continuously variable phase controls. Good! In evaluating a setup, run a full-range sweep (mains + subs) with the mic at the main listening position, and adjust the phase control for smoothest response around the crossover frequency.

This is really important to get the main and sub speakers working with, not against, one another. Using stereo subs, I do this for each channel individually. You can check later with a mono sweep to see what that looks like, if you want.

P.S. Try different sub xover frequencies and slopes. Measure and listen. In my experience, shallower slopes can measure better but sound worse. The effects of changing xover frequency I find a bit unpredictable.

MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #5 on: 21 Aug 2020, 09:18 pm »
I agree with others that you'll have to experiment. James's link gives some ideas. I also agree that the 2nd graph looks better.

According the the Rhythmik site, your subs have continuously variable phase controls. Good! In evaluating a setup, run a full-range sweep (mains + subs) with the mic at the main listening position, and adjust the phase control for smoothest response around the crossover frequency.

This is really important to get the main and sub speakers working with, not against, one another. Using stereo subs, I do this for each channel individually. You can check later with a mono sweep to see what that looks like, if you want.

P.S. Try different sub xover frequencies and slopes. Measure and listen. In my experience, shallower slopes can measure better but sound worse. The effects of changing xover frequency I find a bit unpredictable.

When you say Crossover frequency, you mean the sub's cross over? mains?
Thanks. The mains (Klipsch Heresy 4's) roll off at 48hz so I had been sting in the low 50's but at 60 and even 70 I get much more. I did run sweeps with all mains and subs and honestly they look like the 1st graph. Hump at 44hz then dives down around 63 and then back up at around 125. I moved the rear sub to half way along the left side wall and set the phase at 90, then 45, then 135 and they all basically looked the same. As of  this morning they are both on the front wall and it all seems more cohesive (could be placebo) but I have the same dips just in front of the listening position as I'm sure its all bounsing off the wall behind me (18" back or so). Also I noticed that the louder I do my sweeps the worse they get. My volume knob isn't marked so thats going to be an issue.

I guess I'm running out of ideas being as the right side of the room is way open (though there's good, not bloated bass in the dining area). Also, to the listener's right of the couch in front of the hallway opening there's ridiculous bass. Like huge bass there. So I was thinking some treatment on the back wall. So many rabbit holes....

charmerci

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #6 on: 21 Aug 2020, 09:19 pm »
You can also try the sub crawl trick where you place the sub at the listening position and crawl around the room to find the best sub position.

MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #7 on: 21 Aug 2020, 09:25 pm »
You can also try the sub crawl trick where you place the sub at the listening position and crawl around the room to find the best sub position.

I started with that which is how I ended up with the front left corner and rear by the listening position.

Mike-48

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #8 on: 21 Aug 2020, 09:37 pm »
When you say Crossover frequency, you mean the sub's cross over? mains?
Thanks. The mains (Klipsch Heresy 4's) roll off at 48hz so I had been sting in the low 50's but at 60 and even 70 I get much more. I did run sweeps with all mains and subs and honestly they look like the 1st graph. Hump at 44hz then dives down around 63 and then back up at around 125. I moved the rear sub to half way along the left side wall and set the phase at 90, then 45, then 135 and they all basically looked the same. As of  this morning they are both on the front wall and it all seems more cohesive (could be placebo) but I have the same dips just in front of the listening position as I'm sure its all bounsing off the wall behind me (18" back or so). Also I noticed that the louder I do my sweeps the worse they get. My volume knob isn't marked so thats going to be an issue.

I guess I'm running out of ideas being as the right side of the room is way open (though there's good, not bloated bass in the dining area). Also, to the listener's right of the couch in front of the hallway opening there's ridiculous bass. Like huge bass there. So I was thinking some treatment on the back wall. So many rabbit holes....
I thought you are running the mains full-range and using a low-pass filter for the subs. So what I meant was changing that frequency to see what setting gets the smoothest FR.

Yes, rabbit holes! Hooking up subs is not trivial, especially if you care about even FR and not just boom. Many users prefer to use a crossover for both mains and subs and possibly even DSP (manual or automatic PEQ) to smooth out the bass. But, especially if you are running an analog system, that entails more complication. I am not sure how far you want to go. Really far? Maybe something like a miniDSP SHD. A little? Maybe one of the cheaper miniDSP units. Very little? a graphic equalizer, used in the bass circuit only.

Bass traps do help FR a little, but in my experience, the main effect is to reduce overhang (ringing), which manifests as boominess.


Achieving even bass in in multiple positions in a domestic room is very difficult, if not impossible. Some who use 4 subs report better success. (Google "Swarm subwoofer system".) Without many subs, the best I've ever been able to get is even and smooth bass at the central listening position and close by.

FR = frequency response
PEQ = parametric equalization
DSP = digital signal processing


MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #9 on: 21 Aug 2020, 09:56 pm »
I thought you are running the mains full-range and using a low-pass filter for the subs. So what I meant was changing that frequency to see what setting gets the smoothest FR.

Yes, rabbit holes! Hooking up subs is not trivial, especially if you care about even FR and not just boom. Many users prefer to use a crossover for both mains and subs and possibly even DSP (manual or automatic PEQ) to smooth out the bass. But, especially if you are running an analog system, that entails more complication. I am not sure how far you want to go. Really far? Maybe something like a miniDSP SHD. A little? Maybe one of the cheaper miniDSP units. Very little? a graphic equalizer, used in the bass circuit only.

Bass traps do help FR a little, but in my experience, the main effect is to reduce overhang (ringing), which manifests as boominess.


Achieving even bass in in multiple positions in a domestic room is very difficult, if not impossible. Some who use 4 subs report better success. (Google "Swarm subwoofer system".) Without many subs, the best I've ever been able to get is even and smooth bass at the central listening position and close by.

FR = frequency response
PEQ = parametric equalization
DSP = digital signal processing

Yes, you are correct, mains at full and the subs to fortify. OK I see what you are saying. One thing too is that I once set the subs to 120hz crossover and the graphs looked the same, which, I don't know. I'm definitely not above DSP but my reading suggests I need to get this handled first and then use DSP as the secret sauce?

Mike-48

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #10 on: 21 Aug 2020, 10:16 pm »
DSP will help even out the bass response at the main listening position.
I agree, do the best you can before adding DSP. But below 100 Hz or so, there is not a lot can be done with traps, unless they are extremely big and thick. Below 60 Hz or so, traps are pretty useless unless you use some kind of tuned absorber.


I always think, the big 4 things to address with acoustic treatment are
  • Slap echo - use enough absorption/diffusion to reduce it everywhere
  • First reflections from sidewalls - kill them! and ceiling too if possible
  • SBIR - to reduce this, position speakers so woofers are differing distances from side walls, front wall, ceiling, and floor.
  • Bass trapping - will reduce boominess & improve intelligibility
But not everyone wants to do that much.


WGH

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #11 on: 21 Aug 2020, 10:39 pm »
Thanks. The mains (Klipsch Heresy 4's) roll off at 48hz so I had been sting in the low 50's but at 60 and even 70 I get much more.

When I read your reply, my first thought was "of course the graphs look so terrible, you are crossing over way too high." It's a subwoofer, not a mid-bass woofer.

My speakers roll off at 34 Hz, I have my sub set at 32 Hz. The frequency response is nice and flat. With a higher crossover you are adding bass to bass and as you have noticed the nodes are huge. Try setting the sub crossover lower, 45 Hz as a starting point, you may end up at 38 Hz. Subs work really well in corners, they use less power in a corner too, less power = less distortion.

Recommended reading:
Loudspeakers, Rooms, and Subwoofers - Audiophile Articles
https://www.audiocircle.com/index.php?topic=58304.0

The bottom of the first post has a link to the Harman Room Mode Calculator. The calculator will show you room modes, move your couch into a mode and get tons of bass. Right now your couch may be in a null which is why you want to bump up the crossover point for more oomph.


Videos - No reading required


How to set up a sub crossover
https://rel.net/how-to-set-the-crossover-on-your-subwoofer/

Tackling the Deep End: How to Set up a Subwoofer
https://www.youtube.com/playlist?list=PLaShG1I6_hHXPPWT05eHxYLb1d6SDYbxi

The procedures will work for all subs.

Mike-48

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #12 on: 21 Aug 2020, 10:43 pm »
Not to be contentious, and I know the suggestion to use a room mode calculator is being made to be helpful. Still, if you try it and it doesn't agree with what you actually measure in your room, you won't be alone. Frequently, such calculators are way off, because of construction materials, furniture, and similar factors. Yet, as @WGH suggests, worth a try.

WC

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #13 on: 21 Aug 2020, 10:53 pm »
You can also try the sub crawl trick where you place the sub at the listening position and crawl around the room to find the best sub position.

That only works when you have 1 sub.

Early B.

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #14 on: 21 Aug 2020, 10:58 pm »
I suggest that you set the measurements aside for a while and just listen. Your ears and common sense will tell you where the best locations in your room are.  Afterwards, you can fine tune with measurements and settings.

Many of us place our stereo subs next to the front speakers. Start there.
 

timind

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #15 on: 21 Aug 2020, 11:49 pm »
That only works when you have 1 sub.

What reference do you have for that. I'm only using one sub, SVS SB3000, but am considering a second. I set mine up using the sub crawl and was under the impression if I wanted to add a second I would use the crawl's second best location.

MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #16 on: 21 Aug 2020, 11:56 pm »
When I read your reply, my first thought was "of course the graphs look so terrible, you are crossing over way too high." It's a subwoofer, not a mid-bass woofer.

My speakers roll off at 34 Hz, I have my sub set at 32 Hz. The frequency response is nice and flat. With a higher crossover you are adding bass to bass and as you have noticed the nodes are huge. Try setting the sub crossover lower, 45 Hz as a starting point, you may end up at 38 Hz. Subs work really well in corners, they use less power in a corner too, less power = less distortion.

Recommended reading:
Loudspeakers, Rooms, and Subwoofers - Audiophile Articles
https://www.audiocircle.com/index.php?topic=58304.0

The bottom of the first post has a link to the Harman Room Mode Calculator. The calculator will show you room modes, move your couch into a mode and get tons of bass. Right now your couch may be in a null which is why you want to bump up the crossover point for more oomph.


Videos - No reading required


How to set up a sub crossover
https://rel.net/how-to-set-the-crossover-on-your-subwoofer/

Tackling the Deep End: How to Set up a Subwoofer
https://www.youtube.com/playlist?list=PLaShG1I6_hHXPPWT05eHxYLb1d6SDYbxi

The procedures will work for all subs.

OMG. Setting it too high. I never would have thought of that and yet the graphs back it up. Wow. I feel dumb.

I’ll check the vids on a few , going to turn the crossover point down and listen to what’s happening.  :idea: :idea:

MONKEYWICKEDMONKEY

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #17 on: 21 Aug 2020, 11:57 pm »
I suggest that you set the measurements aside for a while and just listen. Your ears and common sense will tell you where the best locations in your room are.  Afterwards, you can fine tune with measurements and settings.

Many of us place our stereo subs next to the front speakers. Start there.
I have to remind myself that it’s a journey
And not a problem.

JLM

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Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #18 on: 22 Aug 2020, 12:09 pm »
Suggest reading Floyd Toole's "Sound Reproduction" 3rd edition, it is the consummate audiophile primer for understanding how speakers/subs interact in-room.  Toole worked for the National (Canadian) Research Council for decades before retiring from Harmon International.  He invented Spinorama, an anechoic testing method that predicts in-room speaker performance.  He and other acousticians like Earl Geddes recommend multiple subs (3 or 4) to help control bass peaks/dips that are inherent to all residentially sized rooms.  The Rythmik L12 is a very good choice for use in a multiple sub setup. 

He would avoid putting subs side by side and especially all lined up along the front wall with the mains.  Sound behaves as waves up to the transition (Schroeder frequency - roughly 300 Hz).  If you think of a bathtub with 4 inches of water and moving your hand in the water back and forth from end to end, waves are created.  As the waves hit the ends they bounce back where they meet the next wave and either double, cancel, or interfere with each other.  Now imagine a second hand doing the same from from the side of the tub.  The waves would still energize the water but at a more uniform way.  So using side by side subs would just double the bass peaks/dips. 

I have 3 subs in my 8ft x 13ft x 21ft room (could do 4 but 3 is enough).  They are set up along the walls (where subs work best).  One is fairly tight to the front right corner, one is about 2.5ft from the front left corner, and the last one is roughly midspan along the left side wall.  My mains are 5.5 ft from the front wall and 1.5 ft from side walls, severely toed in, with the chair in the middle of the room (mid-field).  Also have six 2ft x 4ft GIK 244 full range panels, four 2ft x 4ft GIK 244 bass traps, three tall open randomly filled bookcases on side walls to act as casual diffusers, and use <500 Hz Dirac room measurement/correction software.  Found that 60 Hz crossover sounded better than 80 Hz. 

Toole recommends getting the right speakers first, then adding room treatments for bass second, although in his own home he violated that to maintain better views from expansive windows which he accepted as a challenge.  Third step would be bringing in the subs.  Finally apply DSP, but always best to solve physical problems via physical means (quoted from Earl Geddes).  BTW my room, done independently, is almost identical to Earl's and follows Fibonacci ratios, ala Cardas.  Toole gives several examples of 4 sub setups in his book.  One of the best is centering them on all four walls.  Another good one was in each corner.

Early B.

Re: 2 subs and oh man I give up....(music 2 channel)
« Reply #19 on: 22 Aug 2020, 01:33 pm »
Suggest reading Floyd Toole's "Sound Reproduction" 3rd edition, it is the consummate audiophile primer for understanding how speakers/subs interact in-room. ... 
He would avoid putting subs side by side and especially all lined up along the front wall with the mains. 

Setting both subs on the front wall next to the main speakers will react in the room in the same way as floor standing speakers that dig down deep, but few audiophiles would argue against the use of floor standers with low bass based on Toole's theories.