[WGH]

After gathering up a series of articles regarding speaker placement, I was wondering how my room sized up. My listening room is also the living room with three doorways on three different walls and windows on two different walls, so seating and speaker placement is very limited.

I have to sit close to the only wall without a doorway, the opposite wall with the speakers is open to the kitchen so the speakers see more volume than the room's 1,553 cubic feet. With an old springy wood floor over a basement, wall-to-wall carpeting, acoustical tile ceiling (don't ask), overstuffed couch and large leather chair and ottoman, the room is well damped with absolutely no echo or ringing. All in all, I am happy with the room's acoustics.

The speakers are my modified Von Schweikert V2's which have a 25 Hz (-3dB) low frequency response.

Just for fun I plotted out my speaker and listening positions using the Harman Room Mode Calculator



Though my head is only 1 foot from the wall, the speakers sit at a 2nd harmonic null.
Since I sit centered on the rear wall, I am also in the middle of the 126Hz and 251Hz standing waves but the speakers are at a 3rd harmonic null.
The speaker's port and woofer are 1' and 2' above the floor with my head about 3' up (when not nodding off).

Comments appreciated or add your own graph.

Wayne

[youngho]

With the doorways, windows, and opening to the kitchen, I would not expect room mode calculators to be particularly helpful. I am a little surprised you sit so close to the wall behind you, though a similar setup has been suggested by Joachim Gerhard, formerly of Audio Physic and now with Sonics by Joachim Gerhard.

[WGH]

The seating location is not as bad as it looks on paper. It is a small room, if the couch was moved closer to the speakers then the front door would not open all the way. The room also is used as a mini-theater, the projector is above the couch.

A quick pano looking through the kitchen opening.


Yes, all the openings change the room modes, that is why I did the layout just for fun. I am hoping to inspire others to look at their speaker layout in a new way and improve their sound by knowing where the modes graphically lay out. Looking at just numbers is interesting, but doesn't help with speaker location. A 3-D virtual reality model of a room would be a lot more helpful than the too simple 2-D graphs.

Wayne

[Ethan Winer]

Though my head is only 1 foot from the wall, the speakers sit at a 2nd harmonic null.

I agree with youngho that this is not a good place to sit. If you must sit there, you need broadband absorbers on the wall behind you to reduce the severe comb filtering off that wall. You'll also benefit from bass traps, and broadband absorbers at the side-wall (and ceiling) reflection points.

--Ethan

[bpape]

Agreed.  If you must sit back there that far, then you're sitting in the spot where all the bass builds up - not just the modal frequencies.  Thick absorbers behind your head (and potentially straddling the wall/floor behind the couch) would help to minimize this issue - though it's not going to do anything to give you a better surround effect.

Bryan

[WGH]

Thanks guys for the suggestions. The sound really isn't that bad, I may be more of a "casual listener" than some but I will look at what is offered for wall treatments.

I built my surround speakers before DVD's or Dolby Digital was available and used the Madisound Vifa Surround Kit. The surround sound is definitely more diffuse than using regular speakers, but that is OK because most movie sound tracks use the surrounds for ambiance anyway. All 8 speakers in the 2 surrounds are now wired in phase which helps with Dolby Digital localization.





Wayne

[WGH]

More fun stuff:

I did some tests with Room EQ Wizard software from the Home Theater Shack using a Radio Shack 33-2050 sound level meter.

I set up the meter at the location where my head would be when listening and set the volume to 75-80dB with a 1000Hz test tone at C weighting.

Why is the bass response on the two graphs different? I dunno, maybe because the bottom graph is a frequency sweep so the room resonates differently than with pure test tones.

[bpape]

Try setting the horizontal scale to just 20-300Hz and the vertical so it's a total of 60db.  Then, take a look not only at the FR but also at the waterfall plot.  That will tell you a lot and give you a lot more detail about what's actually happening.  REW is pretty accurate.  Looking at it's plot, you have over 30db variation from 20Hz-10kHz.

Bryan

[mfsoa]

Hi Wayne,
This probably won't change the measured response much, but have you tried playing around with what's behind your Von's?

W/ the rear-firing driver on my VR4JRs, this can have a big effect on the sound. I have some GIK D1 diffusors that work great for this app., and am hoping to get more.

Yust a thought, since you are so aware of the room interaction thing...

-Mike

[Ethan Winer]

Why is the bass response on the two graphs different?

Because the upper graphs looks to be averaged into sixth octaves (not very useful at bass frequencies), where the lower REW graph is at a much higher resolution. Also, as Bryan said, you should adjust the graph to show more of the active dB range vertically.

--Ethan

[WGH]

Hi Wayne,
This probably won't change the measured response much, but have you tried playing around with what's behind your Von's?

W/ the rear-firing driver on my VR4JRs, this can have a big effect on the sound. I have some GIK D1 diffusors that work great for this app., and am hoping to get more.

Yust a thought, since you are so aware of the room interaction thing...

-Mike

I like what my ambiance enhancers do. The carpet and acoustic tile ceiling attenuate the highs in my room.



I might have time to play with graphs and waterfall plots this weekend.

What am I aiming for?
What would a perfect room response graph or waterfall plot look like? Any examples?
So far my graph looks like a Fletcher-Munson equal loudness graph (except for the peak at 60 Hz).
With my 60 year old ears and a lot of rock concerts behind me, more highs are not a bad thing and none of my (old) friends say my system is bright.



Wayne

[WGH]

Mike - did you see what I did to my VR2's woofers?
http://www.audiocircle.com/index.php?topic=58143.msg514732#msg514732

Wayne

[WGH]

I slightly changed my speaker locations since the graphs in the post above were made and new batteries in the Radio shack meter now give much more consistent results.

I did a few different setups to see what various mike locations would do the the sound, and and then went back and double checked the readings.

The final results show that even though I sit with my head about 1 foot from the rear wall, that is actually where I get the smoothest response, maybe Joachim Gerhard is on to something.

20-300 Hz, default seating on couch, 1/24 octave



20-300 Hz waterfall plot, default seating on couch



20-300 Hz, meter 42" from rear wall, 1/24 octave



20-300 Hz, meter 60" from rear wall, 1/24 octave



20-9,000 Hz, default seating on couch, 1/3 octave


Wayne