B&W speakers vs Room Acoustics, master thread

[BassThatHz]

I'd like to start a master thread about B&W speakers vs Acoustics, with supporting measurements there of.
Many people have had problems with finding optimal B&W speaker placements, and perhaps this thread could be used a starting "reference point" for those seeking advice in that regard.
The B&W research and engineering team has put a lot of effort into taking endless acoustical measurements in their creation(s) to achieve the ultimate in design and quality.
So it only makes sense to continue that process within our home systems too. :T

So there are really two main target audiences here:
1) Those that are new to placing B&W speakers in a room and don't know what to do and/or where to start (ie those seeking the advice)
2) and those that have placed/installed them a zillion times, optimized them to no end, and possibly have even installed acoustical treatments and taken measurements. (ie those offering the advice)


The key here is a decent mix of Measurements & Advice along with the questions and solutions.
Not all of one and none of the other, and vice versa.

A good starting point would be:
1) System pictures or room layout diagrams, ideally with measurement graphs and possibly even budget goals/limits
2) Followed by (or including) questions and advice.

The goal is to optimize the B&W listening experience.

[BassThatHz]

I guess I'll put my neck on the chopping block first :W

Hopefully some of the newer people you can use this as a template of sorts?
I don't know...

(Not sure how long imageshack will host these images for, it is what it is.)



Now before you get all excited, these subwoofers pictured here aren't even powered up yet. That's right, the bass measured below is from my "small" subwoofers.

Dual 15's (small) vs >10x 18's (big) 8O

As you can see from the color of the top-plate, the big subwoofers aren't done yet. Just like Duke Nukem - Forever: "its done when its done!" :lol:



Measurements by REW V4/5 software, done with an CM-140 SPL meter with C-weighting mode and meter correction values applied.
(No EQ, ie pre-eq)

Note: 1000ms = 1 second, 500ms = 0.5 seconds etc

This is a spectrogram and plots time on the Y-axis, Frequency X-axis, and SPL in db's colored on Z-axis: Its main use is to highlight timing issues in the bass region.

From this graph you can see that it is pointing to two potential problems here (likely room distortions): a -20db null at 65hz and poor decay at 38hz.

(On that note, it is natural for deep bass to take longer to decay; but nothing should stick out unnaturally like at 65 and 38.)

This is a waterfall graph and it is exactly the same as the spectrogram, but instead of using colors it uses a 3d viewing angle. x: frequency, y:db z:time

You can see here that the decay above 200hz is exceptionally good, thanks to all the acoustical panels I have and the fast FST-mid.

Because of the lower noise floor of 45db, it is very clear that the bass under 200hz is still decaying after 0.6seconds; this is likely because of all the glass windows I have which are flexing and thus storing the bass energy for longer.
Ideally it should be -60db after roughly 0.4seconds. I'm getting -35db @0.3 <40hz.

Here is the frequency response graph:

Other than 750 hz and my excessive basshead cravings, it looks like a reasonably behaved system. Dare to graph yours un-eq'ed like this?

I wouldn't bet my life on the accuracy of these numbers or the software.
Looks like my SPL meter cannot be trusted below 60hz or above 10khz; although to be fair I haven't had it professionally tuned either.

Here is the Reverb Time -60db plot:

You want a relatively smooth and flat line here, not exceeding 0.4 (unless it is a big-ish room.)

Most recording studios booths and control rooms, such as Abbey Roads, are between 0.4 and 0.2seconds. That's considered the sweet-range.

An anechoic chamber would be near 0.0 flat-line; a reverb chamber would be 1.0+

Looks like my RT-60 is a bit on the dry side ops: but apparently that's how I like it because I'm fairly happy with what I'm hearing.

[Briz vegas]

OMG :E

I see a couple of issues with your approach. You have taken a very measurement based approach to "sound quality" (our ears are the best measuring devices I would suggest) and you seem to be completely OTT with the bass at the expense of the rest of the audio signal. You certainly don't give the sound from your "main" speakers any breathing room and it must be reflecting off those cabinets.

I will be blunt, who puts sub woofers in front of their speakers (I thought this was a photoshop job when I first looked at it). Well obviously you do and you love your bass. I suggest industrial deafness is a likely scenario in your future.

It may be fun, it may be valid for a limited audience, but it does not qualify as hifi in my book. Sorry for being so blunt, but that system just looks wrong.

[Charlieu]

I'm pretty sure they are sitting there just so he could get them in the picture. He mentions that they aren't hooked up.

It looks like the room is heavily treated and I would be interested in seeing a diagram of the room with the speaker positions and descriptions of the acoustic treatments. While it may be more than most of us could get away with, the hows and whys might help someone realize more of the awesome sound B&W builds into each of their speakers.

[beden1]

The OP is obviously single, as I know my wife would have a sh_t fit when she saw this display! :E

[cat-like]

What a great thread start, classic! 8O

[Frank Helmling]

Very useful idea!

This is my setup:

Just look at the 2 cinema lounge pics
My 683's are very valuable for their price but are way to "overbassed", so I cut them at 100 Hz using 3 subs (and a antimode 8033c, of course) which lead me to the following graph (with my ROTEL RSX 1550):

Frequenzverlauf Helmling neu

Funny thing is, I borrowed a Marantz SR 7005 recently and used the parametric EQ to the following extend:

Frequenzverlauf Helmling mit Marantz

But! despite the better frequency response the Marantz didn't sound as good as the ROTEL! So I learned the fact that frequency response isn't all about sound there are much more parameters that influence a good amplifier!

[bigburner]

The OP is obviously single

Just because a guy has a couple of whips mounted above his fireplace it doesn't mean he's single. Well maybe it does...

Seriously though, if we can broaden the discussion into straightforward advice that the non-EE members can understand then I'll definitely keep an eye on this thread.

Nigel.

[mb225]

I'm working on some room acoustics right now and I would be really interested in measure my room before and after treatment. I think this is a great idea for a thread.

Can you put together a room acoustics primer? What do I need to run these tests?
- Software
- Microphone
- Laptop
- etc?

[HedgeHog]

I'm working on some room acoustics right now and I would be really interested in measure my room before and after treatment. I think this is a great idea for a thread.

Can you put together a room acoustics primer? What do I need to run these tests?
- Software
- Microphone
- Laptop
- etc?

Hope Tim doesn't mind but here's his post on AVS: http://www.avsforum.com/avs-vb/showp...postcount=1173

-H

[mb225]

Hope Tim doesn't mind but here's his post on AVS: http://www.avsforum.com/avs-vb/showp...postcount=1173

-H

Thanks! This might be something fun to mess around with.

[BassThatHz]

Here are some virtual images of my room layout (ignore the equipment-list it is not anatomically correct; only the quantity and placement is correct.)
For virutalization software this Google Sketch software is uncanny, it's almost like being there in person!
As you can see my room is an odd shape. I placed everything where the front and side-walls were most consistent; rotating everything by 90 degrees created an unbalanced sound.

Software?

I used REW: http://www.hometheatershack.com/roomeq/
To measure room-acoustics properly its most important have a graph of the waterfall and RT-60, more so than the frequency response; and that is only feasible with software asist.

If you could choose only one graph to look at, it should be the waterfall everytime. It tells you the most out of all the graphs.

Its free and also has many advanced features for when you need that extra investigative breathe. I highly recommend it.

Keep in mind that my SPL meter and software, has a total deviation of +-5db (or more)... and even if it were ruler-flat(which it's not) it can/does/will skew the results regardless.

You have taken a very measurement based approach

No, actually I placed everything by ear first and then took measurements.
The measurements thus had no influence on the config, simply because I found exactly that... that I trusted my ears more than some random mic recording.

On that note, I should have taken a "before and after" measurement.
However... my SPL meter has been dead for over a year now, I just got a new one prior to taking those measurements; haven't had any time to EQ anything yet. (Which was after it was all in place already...)

For critical listening I turn the subwoofers way way down (<75db).

The Marantz didn't sound as good as the ROTEL.

Electronics can make a huge difference in sound IMO. (at least with all the amp's i've tried, good and bad...)

You don't give the "main" speakers any breathing room.

True, but unfortunately my room is too small to support the level of sound that I like, it's a compromise. My opinion on this may change once I fire them up... but I believe (from my ears and measurements) that placing the subwoofers elsewhere isn't an option, it is more important to have stereo bass, and for timing reasons have them as close to the "main" speakers as possible.

The absorber acoustical foam is 96sq ft in volume at 4 inches and 32cu ft for the corner bass-traps. As you can see from the graphs it doesn't make a huge difference below 200hz even with roughly a ~40% coverage.

The diffusors I made myself and are made of birch hardwood, as are the subwoofers too.

[cdika17]

got woofers?

[Briz vegas]

I have seen an interesting solution for achieving your sort of OTT outcomes.

The original idea was to dig a long trench :W, no seriously. The designer of the system had a big property and was building a house. His plan was to basically put the woofer down the other end of the yard so that he could accommodate the long wavelengths involved in very low frequency sound. In the end he went with a couple of pits in his lounge room and built the subs into his floor.

I do still worry about your hearing Mr Hertz. I never go to gigs these days (can't believe I still go to gigs) without earplugs. I would hate to stuff my hearing further than I have already.

Have fun but please watch those high SPLs.

[Charlieu]

I'm not certain those extra subs will do anything for you. It looks like your room is already out of control in the bass region. From 60Hz on up, it looks good. Maybe a bit sterile in the upper frequencies. With all the ringing from 60Hz on down, I would think you wouldn't get any definition out of your subs. You could decrease the volume on the subs and that would help a lot. They are way too hot. Adding the 18 inchers will just add to your problems unless you have them turned down so low that the amp may not provide the power needed to drive them properly.

[wettou]

4 Subs is best, two will give you 95% read Toole's book and you will see.

[Pio]

4 Subs is best, two will give you 95% read Toole's book and you will see.

:agree:

4 subs rock!

[BassThatHz]

I got all four subwoofers rockin' and rollin' now: -3db @ 11hz's
a little hot at +20db, but +-3db from 90-11hz (un-eq'd/raw C-weighting).
It's funny how I placed them almost exactly where Toole recommend they be at for the most optimized quad configuration. :lol:

I think I need to be upgrading to some 802Di's, the 803's just aren't cuttin' it for me anymore :B