Room treatment project!

[Purité Audio]

It might be interesting to examine a few acoustically untreated rooms , look at the measurements, room layout etc and suggest some inexpensive improvements.
Hopfully bringing a real improvement for minimal cost.
I have volunteered Thomas!
Keith

 

[March Audio]

Shall I start with my recent treatment? Room that is..........

 

[Purité Audio]

Please do...
Keith

 

[Thomas savage]

my room is full of treatment of sorts... i wont go first, but will look on with interest.

what do i need to carry out the measurements? i will at some point buy it as will no doubt get obsessed and be constantly measuring my roo response for the next year or so...

so thanks for that in advance!

bass is too loud at some frequencies and hangs about a little too long at some frequencies too, by my estimation.

 

[Ethan Winer]

This will get you started Thomas:

Room Measuring Primer

 

[March Audio]

my room is full of treatment of sorts... i wont go first, but will look on with interest.

what do i need to carry out the measurements? i will at some point buy it as will no doubt get obsessed and be constantly measuring my roo response for the next year or so...

so thanks for that in advance!

bass is too loud at some frequencies and hangs about a little too long at some frequencies too, by my estimation.

You will need a microphone, simplest and cheapest option is the mini disp umik USB mic. It just plugs in a USB port and away you go. It comes with a calibration file.

https://www.minidsp.com/products/acoustic-measurement/umik-1

(I think Keith also flogs them )

Then of course the software. Room EQ wizard. Free and brilliant. It also knows about the umik mic, will automatically ask for the calibration file.

http://www.roomeqwizard.com/

The sweep tones from REW can be output from your PC / laptop sound card headphone socket into your amp, however the sound cards frequency response may be dubious. Otherwise you can use an external USB sound card, or as I do, output to a USB to SPDIF converter which inputs to my DAC, or directly into my theatre amp.

That's it! Plenty of help available here when you are ready to take measurements.

 

[Purité Audio]

'Flogs'! Please I am a purveyor of high quality audio engineering!
I have offered to lend him a microphone, but you know what these subjectivists are like!
Keith.

 

[Thomas savage]

'Flogs'! Please I am a purveyor of high quality audio engineering!
I have offered to lend him a microphone, but you know what these subjectivists are like!
Keith.

yea they like to buy their own... leave the spongeing to you guys

i will do this, then you can poke you prejustice where your mic dont fit

 

[Purité Audio]

If you are going to poke it there ,you are going to have to buy your own!
I have mics here, all USB and really straightforward to use, you are welcome to borrow one.
I would try the Dirac free trial, because the measurement is really straightforward, they talk you through it step by step, the graphs are easy to understand and then you can ask the software to 'optimise' the room so you can hear what Dirac believe it should sound like.
Keith.

 

[March Audio]

OK, going to make a start on relating my experience.

Firstly I have been acoustically measuring rooms for many years. About 15 years ago I bought my TagMcLaren AV system which was one of the first to implement a room EQ system. That pretty much cured my serial upgrading habit because the penny dropped and I realised the room was the important bit and changing the CD player for the Nth time really was going to make very little difference. John Malcahy who was the technical director at TAG is the author of REW.

Although I am used to measuring rooms, I have never actually had the opportunity to implement passive treatments before now, its was just never domestically acceptable. However now we have built our new house I had the opportunity to build a dedicated theatre and listening room. So this was a bit of a learning curve.

The room is 6m x 4.5m x 2.8m, brick walls, concrete floor and has a 133" Screen Inovations curved Black Diamond cinemascope screen and Epson LS10000 with Prismasonic anamorphic lens.

Here are the pre treatment measurements, room EQ off. Room EQ Wizard and MiniDSP Umik usb mic.

Needless to say the room in this form sounded bad. Boomy and confusing. Flutter echo etc. Just for a sense of the sound, here is a clip of a hand clap.

http://gofile.me/2vnEF/71xdznPvD

I do a lot of headphone listening and prefer a "drier"sound. I dont want to hear the reverb of the room and is the biggest issue in the room as far as I am concerned. Not sure I understand some of the advice you see saying a music listening room should have higher reverb times than a theatre room. As such I was aiming for a reverb time of about 0.3 seconds..

Regarding the lower frequency modes it seemed unlikely that passive treatments would be able to address them, being excessive in size, so I will use DEQ to deal with those (Audyssey in my current amp).

As mentioned I have no previous experience of implementing passive treatments, so apart from reading on the various forums, it was difficult to decide precisely the quantity and composition of the types of treatment required - absorption, diffusion and bass traps. So I ended up concentrating on the vicoustic range of products.
http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/absorption

Looking at the data I went for the following panels:
Cinema Rounds - http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/absorption/panel/327
Super Bass Extreme membrane corner traps -http://www.vicoustic.com/images/pdfs/panels/technical_files/Super-Bass-Extreme-Nordik.pdf
Flexiwood A50 Diffuser/Absorber - http://www.vicoustic.com/images/pdfs/panels/technical_files/Flexi-Wood-A50-Nordik.pdf
Multifuser DC2 Diffusers - http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/diffusion/panel/308

A big pile of boxes and mild intoxication due to glue fumes.

I performed the installation in phases so I could measure and listen to the effect. Corner traps first. This is where I realised my first mistake - where I had installed the power sockets meant the traps could only go down to a certain level, limiting the number to 3 on the front wall and 2 on the rear wall (also due to window).

Measurements after traps installed

That seemed to work, not enough though. So essentially following the Vicoustic recommendations I continue to add panels including an additional 2 corner traps at the rear of the room.
http://www.vicoustic.com/hifi-home-cinema/tools/acoustic-simulator/acoustic_mb/40

Long story short ended up like this.

Low frequency reverb times could still reduce. How does it sound? Clean, tight, detailed and nuetral with excellent wide sound stage. It doesnt sound over damped or dull. In fact the Audyssey curve needs to be dialled down a little at HF, which I can do as I have the pro kit.

 

[Purité Audio]

Alan very interesting, did you consider the ratio of the internal dimensions or the method of construction before the build commenced?
Keith.

 

[March Audio]

Alan very interesting, did you consider the ratio of the internal dimensions or the method of construction before the build commenced?
Keith.

Dimensions yes, however it still had to be within certain boundaries. It does fit within the various definitions of "good ratios".

Materials no, the house is brick on a concrete slab. Not good for low frequency absorption.

 

[Purité Audio]

Alan Hi, so the last and best FR plot is just using passive treatment or did you have to EQ down the 30Hz peak?
Here I found my 28Hz to be impossible to treat passively.
Keith.

 

[March Audio]

The above is with EQ. Below are with and without EQ. Without EQ you will never practicaally deal with a 30Hz mode. Those corner traps are limited to around 60Hz. They are fairly broadband. They do another version (wavewood) which has a broader curve, depends on your room. They also do some tuneable traps which go down to 50Hz, but I have no experience of them. http://www.vicoustic.com/hifi-home-cinema/products/acoustic-treatment/basstrap/panel/470

With and without Audyssey

 

[Sal1950]

Alan, a very impressive build in both the room construction and the gear.
Very admirable job on the tuning, I'm sure it sounds incredible.
Congratulations!

 

[amirm]

Vicoustic products are attractive and very low priced. The issue with them is that they don't do much in low frequencies. They simply are not thick enough.

 

[March Audio]

Vicoustic products are attractive and very low priced. The issue with them is that they don't do much in low frequencies. They simply are not thick enough.

Yes, the corner traps are membrane types and more effective than just foam (just foam being pretty much non effective ) but you can see from the plots there is a way to go.

Any suggestions for alternative products or additions to bring this down a bit more?

One question, if there are still discrete narrow band modes kicking off at low frequencies, how useful is an RT60 number?

 

[amirm]

RT60's main use to gauge the overall reflectiveness of the room. The "standard" is to look at the value at 500 Hz. There, you have a value of 0.25 which is very close to the minimum of 0.2 you should have so you are good given your preferences.

On your frequency response, you should run it at 1/12 octave for low frequencies. Set the max to 400 Hz and run that again. At 1/3 octave smoothing, you can't diagnose bass problems. That is only useful to determine overall target curve. Post that and we can then go to the next chapter .

 

[March Audio]

RT60's main use to gauge the overall reflectiveness of the room. The "standard" is to look at the value at 500 Hz. There, you have a value of 0.25 which is very close to the minimum of 0.2 you should have so you are good given your preferences.

On your frequency response, you should run it at 1/12 octave for low frequencies. Set the max to 400 Hz and run that again. At 1/3 octave smoothing, you can't diagnose bass problems. That is only useful to determine overall target curve. Post that and we can then go to the next chapter .

That confirms my thoughts about the RT60. Yep appreciate that 1/3 is no good for looking for the modes.

1/12 Audyssey on/off.

 

[amirm]

Depressing, isn't it? 12 dB variations remain...

Where you are is that you have so much treatment already that if you add more to tame the low frequencies, you will be building an anechoic chamber . The most effective solution is to use multiple subwoofers to cancel the modes. Then let EQ pull down the peaks that remain.