Before and after diy bass traps,see mdat

[Dirt9]

I built ten of these simple corner absorbers with r30(16"x28"x48") and installed eight of them,front and back corners stacked.
The microphone was not moved or unplugged,no smoothing,eq or other treatments in the room before or after.
I'll nock that 50hz peak off when I finish treating the room.

 

[Adhoc]

It looks like the microphone was placed fairly close to the room's centre and all 4 subs were connected with same polarity. You can try and check out how the measurement turns out if both subs at the backwall are connected with switched polarity.

If the microphone is placed in the same place, I presume you will even out the peak at about 51 Hz, while the SPL will increase quite a bit at close to 25 Hz. A peak down there "for free" might be welcomed with movies and usually not very bothersome for music, Do you have a filter engaged to protect the subdrivers or lightweight drywall on studs in your room, doors/windows open? -As the response is falling off below about 25 Hz. (My room has a lowest length mode of about 21 Hz. Due to massive concrete walls + floor + ceiling and with a similar set up as yours for the subs, the room enters pressure mode below 21 Hz and I get an increasing SPL, about +10 dB down at 10 Hz.)

 

[Dirt9]

It looks like the microphone was placed fairly close to the room's centre and all 4 subs were connected with same polarity. You can try and check out how the measurement turns out if both subs at the backwall are connected with switched polarity.

If the microphone is placed in the same place, I presume you will even out the peak at about 51 Hz, while the SPL will increase quite a bit at close to 25 Hz. A peak down there "for free" might be welcomed with movies and usually not very bothersome for music, Do you have a filter engaged to protect the subdrivers or lightweight drywall on studs in your room, doors/windows open? -As the response is falling off below about 25 Hz. (My room has a lowest length mode of about 21 Hz. Due to massive concrete walls + floor + ceiling and with a similar set up as yours for the subs, the room enters pressure mode below 21 Hz and I get an increasing SPL, about +10 dB down at 10 Hz.)

I have two subs.one front and one rear,here's a graph of the LF cut turned up a little.
don't have a way to switch the polarity without pulling the driver.i have tried 180 phase but it was not constructive ,I also spread the rear bass traps out across the rear wall instead of stacked because I felt they pulled down 60hz to 100hz to much,
Yes room is builders grade with light drywall,two windows and a door but not open,I have not ran any eq yet as i'm still in the set up phase with these treatments....a work in progress

 

[John Mulcahy]

Your mic cal file has also been loaded as a soundcard cal file so it is being applied twice, should remove it from the soundcard cal.

 

[Marc Lombardi]

I built ten of these simple corner absorbers with r30(16"x28"x48") and installed eight of them,front and back corners stacked.
The microphone was not moved or unplugged,no smoothing,eq or other treatments in the room before or after.
I'll nock that 50hz peak off when I finish treating the room.

Great job! But doesn't it suck that you can put that much into bass traps and the resonances below 100Hz are SO hard to treat. It just isn't practical to get the traps far enough from the wall for resonances that low. Luckily that peak will iron out easily with some DSP. Are you considering a miniDSP so you can do very fine time delay and gain adjustments, and apply the PEQ to the combined result with filters made in REW?

 

[bvocal]

Are your units open faced, as in no membrane?
Have you listened to this yet, or just measuring?

 

[Dirt9]

Your mic cal file has also been loaded as a soundcard cal file so it is being applied twice, should remove it from the soundcard cal.

Thank you John,with the asio4all soundcard file cleared there is a huge difference in the high frequency readings,I was wondering why the 5k-20k range always swooped up.thought it was the nature of the speakers lol.

 

[Dirt9]

Great job! But doesn't it suck that you can put that much into bass traps and the resonances below 100Hz are SO hard to treat. It just isn't practical to get the traps far enough from the wall for resonances that low. Luckily that peak will iron out easily with some DSP. Are you considering a miniDSP so you can do very fine time delay and gain adjustments, and apply the PEQ to the combined result with filters made in REW?

I really want to get a miniDSP 2x4 but i'm not sure there would be a improvement.I bought a antimode s-ii last year before i knew how serious i was going to get haha lol.
It works wonderfully but takes thirty minutes to run and you never really know what you get after it runs.I find myself running it over and over again obsessing over the measurements lol

 

[Marc Lombardi]

I really want to get a miniDSP 2x4 but i'm not sure there would be a improvement.I bought a antimode s-ii last year before i knew how serious i was going to get haha lol.
It works wonderfully but takes thirty minutes to run and you never really know what you get after it runs.I find myself running it over and over again obsessing over the measurements lol

I used an Antimode for about 6 years before I got the XMC-1 with Dirac. It definitely measured really well and the system sounded great too. A miniDSP does not have as many PEQ filters as the Antimode so it may not do as well with the equalization. But being able to use it to time and gain align multiple subs is a great feature.

 

[Dirt9]

Are your units open faced, as in no membrane?
Have you listened to this yet, or just measuring?

These are the simplest absorbers I think someone could make.All they are is a piece of plywood top and bottom stick framed with four 1x2's making four open sides.
I used three batts of R30 in each.peeled the paper off the middle batt and left the paper on the two outside batts for convenience.Then wrapped them nice and tight with the cheapest material I could find...black bed sheets.
Yes I have been listening and measuring.The sound has improved a ton,it sounds much more full and tight.The voicing went from kind of hollow to full and thick.
I also have noticed what I would describe as spaciousness behind me.maybe from the rear wall refections being more controlled?
It really does make a dramatic difference just treating the corners.definitely has a long ways to go but but this graph is literally going from a empty room to absorption in all four corners.nothing else was done.no eq,speaker repositioning or mic repositioning.

 

[Marc Lombardi]

These are the simplest absorbers I think someone could make.All they are is a piece of plywood top and bottom stick framed with four 1x2's making four open sides.
I used three batts of R30 in each,removed the paper from the middle batt and left the paper on the two outside batts for convenience.
Yes I have been listening and measuring.the sound has improved a ton.it sounds much more full and tight,voices went from hollow sounding to natural and thick.I even am hearing what I would describe as spaciousness behind me.maybe from the rear wall reflection being controlled better?
It really is a dramatic difference just treating the corners with thick absorption.

How about the waterfall plot? I bet the time domain has tightened up a lot and that's the real benefit of the absorbers that you can't get from DSP.

edit: Okay I just saw you posted the .MDAT. The waterfall looks good. The traps did fill in some of the nulls, which you really can't do well with EQ so that's a big plus. Oddly, the 50Hz looks like decay is longer with the traps. Am I seeing that right? BTW, I have some 40Hz noise from the refrigerator in the nearby kitchen and HVAC that sometimes skews my results at what happens to be my main resonance.

 

[DavidK442]

I'm no expert, but the waterfall plot before room treatment looked great. The traps may have smoothed out a null around 95 Hz, but otherwise they just sucked energy from the room above 60 Hz.
I have seen a few of these "before and after" absorptive bass traps experiments and I'm even more convinced that I won't waste the money or effort again.
Using multiple subs, as has been done here, gives the best result. Thanks Mr. Geddes / Olive / Toole and thanks Dirt9 for taking the time to measure and post.

 

[Dirt9]

How about the waterfall plot? I bet the time domain has tightened up a lot and that's the real benefit of the absorbers that you can't get from DSP.

edit: Okay I just saw you posted the .MDAT. The waterfall looks good. The traps did fill in some of the nulls, which you really can't do well with EQ so that's a big plus. Oddly, the 50Hz looks like decay is longer with the traps. Am I seeing that right? BTW, I have some 40Hz noise from the refrigerator in the nearby kitchen and HVAC that sometimes skews my results at what happens to be my main resonance.
[/QUOT
With the asio4all sound card file cal error pointed out John Mulcahy i've decided pull everything out of the room and start over.i'll keep posting the data for everyone.

 

[Dirt9]

How about the waterfall plot? I bet the time domain has tightened up a lot and that's the real benefit of the absorbers that you can't get from DSP.

edit: Okay I just saw you posted the .MDAT. The waterfall looks good. The traps did fill in some of the nulls, which you really can't do well with EQ so that's a big plus. Oddly, the 50Hz looks like decay is longer with the traps. Am I seeing that right? BTW, I have some 40Hz noise from the refrigerator in the nearby kitchen and HVAC that sometimes skews my results at what happens to be my main resonance.

With the asio4all sound card file error pointed out by John Mulcahy i've decided to pull everything out of the room and start over,I'll keep posting the data for everyone.

 

[Marc Lombardi]

With the asio4all sound card file error pointed out by John Mulcahy i've decided to pull everything out of the room and start over,I'll keep posting the data for everyone.

You're a good engineer Dirt9 !

 

[Eric SVL]

I'm no expert, but the waterfall plot before room treatment looked great. The traps may have smoothed out a null around 95 Hz, but otherwise they just sucked energy from the room above 60 Hz.
I have seen a few of these "before and after" absorptive bass traps experiments and I'm even more convinced that I won't waste the money or effort again.
Using multiple subs, as has been done here, gives the best result. Thanks Mr. Geddes / Olive / Toole and thanks Dirt9 for taking the time to measure and post.

But subs don't help your modes in the 100-300 Hz range.

 

[Norbertino]

Hi! I have a problem with the bass. There’s a lot of bass in the room and I want to improve the acoustics. I'm a beginner. What is a good bass trap? What kind of bass trap do you offer?

 

[Kakkadu]

The problem with simple wool absorbers is that you need a quarter wavelength thickness of wool to have maximum absorption. For super low frequencies you'll want a diaphragmatic or helmholtz resonators.

 

[Norbertino]

Thanks

 

[Kakkadu]

Keep in mind that both diaphragmatic and helmholtz are so called tuned resonators. They damp only a tuned frequency. That's why it's imperative that you measure your room first, determine the problem frequencies and then build / have built resonators to solve the problem. You might need several resonators if the room has concrete/brick walls.

The Helmholtz resonator is just like a bass reflex speaker without the driver part. And a diaphragmatic resonator is a bit like a speaker box with a passive driver. For low frequencies you may need to build a box that has either a limp mass resonator or solid appearing MDF sidewalls and damping material. The 1" MDF actually flexes and resonates at around 50hz.