Speaker/Room calibration

[jpv]

Bruce,
One suggestion, When doing this just change one item at a time. By doing that it will make it much easier to see what each change is making. by changing 3 setting and posting a graph we can't see exactly what each control/ move is doing. Also when looking at the bass freq. show the graph 20 - 200hz., no smmothing, and with limits of 105 to 45db. When looking at the higher freq. thats when we add smoothing to eliminate comb filtering.
Looks like the radio shack meter wasn't that far off.
John

 

[theguesswho]

Hi, in the second to last graph which is very similiar to the Radio Shack meter graph, I still see just a couple of db peak. Absolutly no reason to use an equalizer. That would be Bruces last 1-3% improvement he is looking for. Unfortunatly it adds an EQUALIZER and another set of cables to muck up the sound.
Don't forget Bruce loves the sound of his system so why change it to make a cheap Radio Shack meter happy? And if a Radio Shack meter is the same as a "calibrated" mic, that just goes to show I would not trust any of this stuff.
Listen to your ears! Neither Bruce nor has anyone else, including whoever set it up initally, has heard any problem with his system before and it was set-up by competent acoustition or dealer.
I am beginning to think its the room.

Jack
POE143
"If the first octave sucks, why continue?"

 

[DonH50]

About 20 dB variation max to min but overall looks much better to me. There's only so much you can do with relatively coarse controls, and we tend not to hear closely-spaced peaks and valleys. The large dip is almost certainly the fundamental room mode.

theguesswho: "I am beginning to think its the room." -- I think we all realized that all along... Anechoic speaker responses have little relation to reality in most rooms.

 

[rbbert]

FWIW, in my similarly proportioned room, I ended up with my speakers 1/5 of the way in from both the front and side walls and the listening position 1/3 of the way in from the back wall. Both of the recommended locations from Evolution Acoustics

http://www.evolutionacoustics.com/support/speaker-placement/short-wall-placement/

ended up with far too much mid-bass (~70 - 120 Hz) for my taste.

 

[FrantzM]

Bruce response is very good .. Yet the more I look at such response the more I realize how important DRC is ... I have been on the fence for along while ... flipping this way and that way ... That's it!!! .. I am gone to the DSP driven world of DRC and speaker correction. There is NO way the coarse control of the speakers can do much better than what Bruce has already obtained, next step is the fine-grain and targeting abilities of DRC.
I know the thread is not about DRC, so I am exiting.

 

[Bruce B]

Thanks so much for the feedback guys. Very helpful.

John, I will set all controls back to default and just do positioning first. Then I will do an overlay of before and after. I think that will help determine what changes were made.
I will show only 20 - 200Hz with no smoothing with limits suggested.

Frantz.. I'm not totally against DRC. I'd rather try EQ in the analog domain first.

Appreciate all that are following along.

 

[Roger Dressler]

The large dip is almost certainly the fundamental room mode.

A room mode calculator shows the first length mode is 26 Hz and width is 42 Hz.

theguesswho: "I am beginning to think its the room." -- I think we all realized that all along... Anechoic speaker responses have little relation to reality in most rooms.

And apparently neither do bass traps. That null at 40 Hz is pretty severe, and I suspect is not what you are hearing because you are measuring each speaker by itself, but playing them together. Assuming most recordings with 40 Hz content carry it roughly equally in both channels, your audible results may be vastly different. Easy way to tell is to run the REW response again while feeding both speakers. No need to sweep beyond 100 Hz for this test.

 

[Roger Dressler]

Bruce response is very good .. Yet the more I look at such response the more I realize how important DRC is ... I have been on the fence for along while ... flipping this way and that way ... That's it!!! .. I am gone to the DSP driven world of DRC and speaker correction. There is NO way the coarse control of the speakers can do much better than what Bruce has already obtained, next step is the fine-grain and targeting abilities of DRC.
I know the thread is not about DRC, so I am exiting.

Neither speaker controls nor DRC will have any effect on the 40 Hz null. Adding a subwoofer or two, now that's a different story. Or, as we may soon find out, so may be driving the two mains together.

 

[bblue]

Here is what I ended up with by moving my listening position about 2' closer, changing the bass filter to 150 and bass level down 2dB

Any more suggestions?

In all of the plots I've seen so far, it looks to me like there is a pretty serious set of node resonances/dips at about 40Hz and 120Hz. Those aren't something that are likely going to be changed significantly by speaker adjustments on the back panel. I think this points either to speaker placement relative to rear or side walls, and/or the need of some strategically placed deep bass traps. Until those can be smoothed out, I'd leave the speaker controls to the most neutral setting as possible.

I've been fighting with similar nodes in my much smaller but also 'designed acoustically' room. I've tried various additional traps and found that any room corners when additionally trapped made an improvement, but the biggest improvement so far was putting all the traps in the rear corners from floor to ceiling. It's as if the built-in full wall slot trap is not doing what it is supposed to be doing.

You might want to look at waterfall plots and general room characteristics in REW and see how they compare to what you're currently getting.

--Bill

 

[Bruce B]

In all of the plots I've seen so far, it looks to me like there is a pretty serious set of node resonances/dips at about 40Hz and 120Hz. Those aren't something that are likely going to be changed significantly by speaker adjustments on the back panel. I think this points either to speaker placement relative to rear or side walls, and/or the need of some strategically placed deep bass traps. Until those can be smoothed out, I'd leave the speaker controls to the most neutral setting as possible.

I've been fighting with similar nodes in my much smaller but also 'designed acoustically' room. I've tried various additional traps and found that any room corners when additionally trapped made an improvement, but the biggest improvement so far was putting all the traps in the rear corners from floor to ceiling. It's as if the built-in full wall slot trap is not doing what it is supposed to be doing.

You might want to look at waterfall plots and general room characteristics in REW and see how they compare to what you're currently getting.

--Bill

This is an acoustically designed room. Over a third of the cubic volume is bass trapping. The corners are triangulated, from floor to ceiling with bass traps, the whole front wall is a bass trap and the overhead soffit is a bass trap.

 

[Roger Dressler]

This is an acoustically designed room. Over a third of the cubic volume is bass trapping. The corners are triangulated, from floor to ceiling with bass traps, the whole front wall is a bass trap and the overhead soffit is a bass trap.

How much of that trapping reaches 6' from the hard walls?

 

[Bruce B]

How much of that trapping reaches 6' from the hard walls?

About 60 sq. ft. of surface is 6' deep

Most of the other is 4' deep

 

[microstrip]

This is an acoustically designed room. Over a third of the cubic volume is bass trapping. The corners are triangulated, from floor to ceiling with bass traps, the whole front wall is a bass trap and the overhead soffit is a bass trap.

I have seriously considered this option - building a full front wall bass trap, as I have plenty of depth. But never could figure what should be the target frequency.

Your room response puzzles me - 41 Hz is the second fundamental room mode - the longitudinal one is around 25. Can the dip around 41 Hz due to excessive bass trapping at the bass trap ressonance? But except for this large dip it looks really nice and well balanced!

 

[Roger Dressler]

Your room response puzzles me - 41 Hz is the second fundamental room mode - the longitudinal one is around 25. Can the dip around 41 Hz due to excessive bass trapping at the bass trap ressonance?

Consider what happens with an infinite bass trap: playing the speakers outside. There is no dip. The dip means the bass is in fact not being trapped.

It's so much more effective to kill these bass modes with multiple subs, no room should be designed without them.

 

[NorthStar]

Roger, what would be the right (ideal) number of subwoofers in Bruce's room, you think?

 

[Bruce B]

Here is the general layout of the room. Red line is the soffit above.

 

[jpv]

Bruce,
Can you tell us where the listening positon and the speakers are located.
Also can you move the mic so it is 4'6" from the rear wall centered left and right and post that for us.
John

 

[rbbert]

Roger, what would be the right (ideal) number of subwoofers in Bruce's room, you think?

I do wonder if it is even possible to get really good (fairly flat, clean and fast) bass in a room this size without additional subwoofers. Even assuming the MM3's are good down to 20 Hz or so, I would think adding one or two more subs (i.e. a total of 3 or 4) is necessary for truly good bass response.

 

[NorthStar]

I do wonder if it is even possible to get really good (fairly flat, clean and fast) bass in a room this size without additional subwoofers. Even assuming the MM3's are good down to 20 Hz or so, I would think adding one or two more subs (i.e. a total of 3 or 4) is necessary for truly good bass response.

Yes that was my point. I know that Roger is using four subs in his own room.

* I guess Bruce would have to experiment first with two, then three, and finally four.
And to have them perfectly balanced in levels, from the main listening position.

And that would be what I would do myself first to smooth out peaks and dips,
even in Bruce's fantastic room.

And Roger is using his own method to calibrate his room to taste; with his Classe preamp and some external equalizers.

Me, I don't know enough on how to 'strangle' myself with a system like TacT for example.
And I don't use REW either. I only rely on Audyssey (Auto) in my own system & from my very humble two subs. But the qualitative results are tenfold compared to without Audyssey (XT flavor only, till I upgrade to XT32). For both Movies (multichannel) and Music (2-channel) listening.

 

[jpv]

You guys are moving way to fast. Bruce posted 2 graphs, Hasn't shown what the contros are capable of dong and you have him getting 3 to 4 subs. Nothing like throwing gas on the fire.
He needs to get a base line, figure out that he can achieve thru speaker and listening position, what the EQ options are, ect..
REW is a great tool and can really help - so move slowly and with purpose.