Room acoustics experience

[johniboy]

Hi!

 

I would like to share with you some experience I recently made with room acoustics.

 

My system: PC->RME9632->DCS Elgar Plus->Linn 2250->Dynaudio C2

 

I made some significant updates in the last couple of months by changing my CD player by a computer/Dac combination and it was a huge improvement in sound quality. The next logical task was to improve the listening room. I read the book Harald suggested: http://www.amazon.co.uk/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?ie=UTF8&qid=1248772127&sr=8-1 WONDERFUL!

 

Its great reading and the first thing I learned: Do not put panels to the side walls to decrease the first reflection points. Its BAD. The second thing I learned: Only care about frequencies below 200HZ. Bass-traps will not really help, try speaker positioning and careful equalization. Good. That helps to avoid spending money on panels you don´t need.

 

So I went and did a little google-ing. I bought a Behringer ECM8000 micro and a behringer micro-preamp. Downloaded a lot of freeware:

- RoomEQ wizard (http://www.hometheatershack.com/roomeq/)

- DRC (http://drc-fir.sourceforge.net/ and http://www.duffroomcorrection.com/wiki/Main_Page and a DRC documentation written in German by a guy called Fujak)

- convolver plugin (convolver.sourceforge.net/)

- SIR convolver (http://sox.sourceforge.net/)

- SOX (http://sox.sourceforge.net/)

 

First I made some measurements with RoomEQ wizard. Its a really easy to use and nice piece of software. I was astonished how quickly a novice like me got it working with my RME soundcard. Well the results didn´t look that discouraging. I did have some usual peeks at lower frequencies but nothing really dramatic. On the other hand, I had a dip of about 5-10 db that was worried me more.

 

As a next step, I thought I would try to build a correction filter with DRC and use a convolver to correct for my room effects. The short story: It did not work. I mean technically it was all OK but due to the large decrease in overall sound power, the music was not enjoyable anymore. Then I tried the same using roomEQ wizard. I just corrected the frequencies below 200 hz and generated a filter for the convolvers. Again the same problem. The convolvers sucked the music out my system. Lifeless. Just to make it clear: The correction filters were selected carefully and should not have such a big effect on overall sound. They should have decreased 1-2 room nodes a bit but not more. I believe the real-time convolvers ruin the sound. That was my impression.

 

So I gave up on the equalization part for now and played around with speaker and listening positioning. I made about 50 sweep measurements with all kind of setups and probably drove my neighbors crazy. Just imagine a guy playing 5-20k Hz sweeps the whole entire day at around 75db... Finally I think I found a pretty good compromise. The big frequency dip is gone. There is one peak left but its pretty high Q and shouldn´t be such a big issue.

 

Finally the listening experience: It was another big improvement in sound quality, even without equalization. I can just recommend everyone to buy a good micro and a pre-amp if you don´t have one and do the exercise. Its worths the 100$! With regard to equalization: I am not sure whether introducing another software / hardware is worth it. The damage you do by digital manipulation or an additional ad/da conversion may be larger than the improvement by correction for room artifacts. This might be different for other rooms however.

 

Thats all. Thanks for reading through this long post. Hope it helps others to improve their sound system. If anyone is interested I can post some graphs of my measurements.

 

Greetings from the sunny Berlin.

 

[sshd]

Did you use a calibrated microphone that comes with a correction file?

 

It really makes a major difference. It took several target curve experiments with the uncalbrated microphone and the result was never completely satisfactory.

 

The calibrated microphone changed that. The "mostly" horizontal curve works very well.

 

[manisandher]

Great post johniboy - really insightful. I think this is something everyone could do with trying...

 

sshd, the Behringer mic looks very linear below 2KHz - not sure how much a calibrated mic with a correction filter would help. Having said that, I know that companies like DEQX recommend using them.

 

As an aside, a few years ago, I tried a DEQX unit. I asked DEQX why they didn't add a USB or firewire port to the unit (actually, it does have a USB port, but only to enable software control of the unit, not to pipe music to it). DEQX replied that the unit is intended for audiophile use, not computer audio! I returned the unit and got my money back (I much preferred my analogue x-overs anyway).

 

Mani.

 

[johniboy]

well, i did not actually get a calibrated micro but you can download calibration files for the ecm8000. i know its not perfect because there are still differences between the different units but i believe its a good estimate. i also calibrated the soundcard / dac combo but that was unnecessary. they resulted in a straight line... peeeeeep.

 

i never had a chance to listen to a tact or similar unit but i heard from people that they are not the best d/a converters in the world and sound more on the harsh side.

 

[sshd]

I do not know the brands and models of the original microphone and micro-amplifier. It was something my neighbor purchased for around €200 and it was supposed to be very linear and very good.

 

We use Audiolense as the software and it does not allow to just adjust some frequencies. The target curve with the uncalibrated microphone has to be tweaked a lot to follow the meassured curve a lot more than desired. It did improve the sound, but a major problem around 5 kHz remained.

 

The meassurement with the calibrated microphone is somewhat different. Not major differences, but they are clearly there. The target curve is almost linear between 50 Hz and 9 kHz. It rolls off at both ends to follow the natural curve of the speaker. It really sounds excellent and the problem arond 5 kHz is gone. Additionally a few cds I had previous written off as being badly recorded now suddenly sound fine.

 

My neighbor has similar positive experiences with the change with his setup.

 

The calibrated mic+amp is even cheaper than the original equipment:

http://www.content.ibf-acoustic.com/catalog/product_info.php?cPath=30&products_id=35&osCsid=53c20ea3896f7cb1107ccdf6b21bc1d1

 

[johniboy]

i looked into audiolense and it looks pretty similar to roomEQ Wizard with some additional features. nice.

 

my question: what kind of mediaplayer and convolver are you (and your neighbor) using? I have less problems with the generation of filters than the convolving process itself. The ones I tried were not very satisfying, but maybe i was doing something wrong. My first worry is the dramatic loss of overall output volume. I played around with the parameters but it did not help too much. Maybe you could give me a hint on this part?

 

 

 

[tomE]

Years ago when I was single and could get away with it I did experiment with a LE/DE set up that did use absorbtion/diffusion devices with VERY good results. Of course I didn't know it was bad. Wish I could play with that kind of thing again but my SO is pretty fussy about decor etc and I do not have a dedicated listening room!

 

[sshd]

We use foobar2000 with the plugin foo_convolver. It works perfect, but may change the volume to much. The convolver plugin has an auto adjust setting. Additionally I use replaygain + preamp to maintain a proper volume. The replaygain part does not work for my neighbor - he claims it destroys the dynamics.

 

The convolver in ffdshow does not work - it has too few taps.

 

I was unsuccessful in getting convolver.sourceforge.net to work also.

 

 

 

[johniboy]

well, my better half knew from the beginning that i am an audio freak. she thinks i´m crazy but accepts my disabilities. ;-) once i even audited resonators from acoustic systems (little bells sticked to your wall). thats when she started laughing: why would you put jewelry on the wall and not in my finger??

 

i don´t have a dedicated listening room either and was ready to decorate it with at least some foam until i started reading acoustic books. very enlightening! my conclusion for all this is: we are all too different and you just have to listen to it yourself. and this means a lot of tinkering and playing around. but thats why its a hobby!

 

[johniboy]

maybe i will also give foobar a try.

 

i did get convolver.sourceforge.net to work using jriver. just had to install a directx plugin. i usually use mediamonkey as playback software - i like its usability and sound - but for plugins jriver is much more flexible. i also tried the sirs convolver, which is a vst plugin and also works with mediamonkey using a vstbridge. both convolvers, using both mediaplayers had the same issue: significant loss of volume and loss of dynamics.

 

i was thinking about maybe trying to get a behringer FBQ2496 for equalization. any experience with that??

 

[sshd]

Let me know if you find foobar2000 better.

 

PS: The Peak Meter visual is excellent to determine the preamp level.

 

I don't know anything about the specific piece of hardware you mention, and I am not really interested. My current sound with foobar2000 is simply fantastic. My only problem is that I cannot get the convolver to work in Media Player Classic for movies.

 

[wgb113]

This reminds me that I have to go back and measure my room again and possibly adjust settings now that we've changed furnishings, placement, and added some things that could very well have changed my room's response.

 

I use Rives Audio's Test CD 2 with my RadioShack meter because it contains a set of tracks that are corrected for the errors of the meter.

 

Bill

 

[Steelman]

Hi John,

 

Your experience with equalization was similar to mine.

 

I used the excellent and free RoomEQ software with a Behringer mic (using the RoomEQ mic calibration file, although for best results, the www.hometheatershack.com people say you should send the mic off to be calibrated).

 

* In the final analysis, the RoomEQ software was most helpful in learning how to best place the sub and mains, and integrate them properly; it made a huge sound quality difference and helped me think carefully about lower frequencies

 

* Flat low frequencies sound terrible; check out the RoomEQ site and www.goodsoundclub.com for some insightful comments relating to "knees"

 

* EQ-ing higher frequencies was a futile exercise in my experience

 

* I used a Behringher DEQ2496 to EQ the system but pulled it out as it was not transparent when run through all the speakers. With the DEQ connected just to the sub, the processing caused a delay (a foot or two if I remember correctly) which I disliked (the mains are time aligned so the difference was especially noticeable)

 

* The DEQ was fun as you can fix lousy engineering on your favorite music; it also has a great dynamic loudness function that helps with low-volume listening. But I found the system sounded better without the DEQ and optimizing speaker placement.

 

Steelman

 

 

 

[Synfreak]

Hi!

 

To "johniboy":

 

Not only because you are from Berlin, but this forum (german only) might be interesting, too:

http://www.casakustik.de

 

The guy behind it (Andy, ASB) is also from Berlin, so a "howdoyoudoit" meeting should be possible ;-).

 

Cheers

Harald