[zydeco]

Another first-time poster. My room is small – 16ft (long) x 12ft (wide) x 10ft (high) – with double-brick construction and suspended wooden floors. The room is filled with a range of furniture that reduces the effective size and demands creative use of room treatment.  The set-up is more-or-less near-field with the speakers and listening position forming an equilateral triangle with lengths around 8 fit. Speakers are toed in slightly to minimize room effects. A sketch of the set-up is attached.


Over the past 12 months I’ve started with room treatment. A thick rug on the wooden floor as well as removable plywood board to seal the fireplace that sits between the speakers. Some 4” acoustic foam has also been located on the plywood board to reduce reflections on the front wall between the speakers, as well as on the first reflection points on the rear wall. All this worked well with noticeable improvements in imaging. The next major change came when some large (4ft x 2.5ft x 4”) acoustic foam bass traps came up in the local trading post and then set-up 2-high to straddle the left / right corners. This change had an obvious impact on room acoustics – reverberation was noticeably reduced but at the expense of ambience – and the dark-grey panels remained an eyesore.

All this made me realize the importance of the room and, after listening to a few high-end rooms, I’m now rather dejected by the limitations within which I’ve got to work. I’ve contemplated the idea of headphones but thought that the right answer was to give room treatment a proper crack. The start point, I guess, is to sort-out the front corner bass traps so that these are both effective and the visuals work within the room. Current default plan is to extend the bass traps floor to ceiling as well as add a small mid-bass corner trap behind the larger bass-trap to fill in the air gap. This will require a little work to make the visuals work but it should be possible.

The concern is that this large amount of foam will kill ambience while, potentially, not providing the best possible bass performance. Is it possible to dress the foam in a manner that avoids killing the ambience (perhaps wood strips)? Or, alternatively, would it be better to move to either super-chunks or a commercial product such as Real Trap’s Mini / Mega Traps or some kind of Tube Trap? I’ve found it hard to find concrete reports on relative performance so feedback from folks who have tried both approaches would be very helpful. Another question is what is the second priority once the front corner traps are completed. You can see from the sketch that the right rear wall corner isn’t an option due to the location of book-case. My thinking was the left wall corner, and, then, the wall-ceiling interface at (in order of priority) the rear, front and sidewalls. Advice on this would be great.
 
Regards
Zydeco

[max190]

Welcome Zydeco,

You've come to right place.
Take a look at the products that these companies offer on these sites.
http://www.gikacoustics.com/products.html
http://www.realtraps.com/

They also provide test results - Hz to absorption coefficient
The owners of these companies check in here often.

BTW, I have a ded room that is smaller than yours, 12'.6"W x 15'.5L x 8' though I do not have any furniture other than a loveseat and my cd rack.
   

[Nyal Mellor]

Always the same question, but what problems are you trying to fix?

The main uses for treatment are:

1) RT60 reduction
2) Creating a reflection free zone
3) Bass trapping

Measure first, decide improvement strategy later.

[zydeco]

@ Steve - Thanks. I've seen Real Traps and GIK Acoustics not available Downunder.

@ Nyal

You’re right a more detailed description of objectives and how I got to this place are needed. The set-up is a 3-way active system that has had to be moved from a much larger room into this small room in a new abode. This move saw sound-stage become smaller and more two-dimensional while the bass became less smooth to the point where I’ve wound down the woofers amplifiers.

The thinking was to focus on solving the bass as this might be simpler and, in doing so, allow more careful evaluation of subsequent changes on the mid-range / sound-stage. I’ve used a Radio-Shack meter, and REW, to conduct a series of simple tests. The starting point was a traditional sweep with the meter at listening position which is shown below. And  walking around the room with the SPL meter during a 30 to 300Hz white noise signal found the front corners and rear wall-ceiling interface were+6dB and +3dB louder than listening position.



All these measurements don’t, to my uneducated eye, look too bad. Then again, music tells another story and, interestingly, adding the large stacked bass traps had a noticeable effect that wasn’t seen on the measurements. So, then, that’s the situation – it’d be great to get your take on the nature of the issue and priorities – I’m not precious about a change of direction but just want to learn and get a better sound.

Regards,
Zydeco

[Ethan Winer]

@ Steve - Thanks. I've seen Real Traps and GIK Acoustics not available Downunder.

If "Downunder" means Australia, we have a dealer there that's listed on our Prices page. Here's the direct link:

http://www.awave.com.au/

--Ethan

[Nyal Mellor]

What resolution is Room EQ wizard set to on those measurements? 1/24th oct?

The bass is pretty flat below 100Hz, not sure what problems you are hearing when listening to music?

And your right on in your approach - sort out the bass first, then the mid and higher frequencies.

[zydeco]

@Ethan

Thanks for the heads up regarding www.awave.com.au. It’d be good to get your advice on the merits of treating the front corners with a Mondo Trap (at mid-height in the room) versus stacking a couple of mega-traps from the floor (noting that floor to ceiling will be too expensive).

@Nyal

Well, I don’t believe that there is any smoothing (or at least 1/3 octave smoothing is off). The bass is good and I’m able to detect any specific problem frequencies. That said, it doesn’t have the three-dimensional, encompassing, character – or integrate as well with the mid-range – as it did in the larger room. Also, when I listen to music while working at the desk (2ft behind listening position) the bass become even more overwhelming. Part of idea, I guess, is a sense "I don't know what I missing" but that bass could just be a lot better.

[Ethan Winer]

It’d be good to get your advice on the merits of treating the front corners with a Mondo Trap (at mid-height in the room) versus stacking a couple of mega-traps from the floor

Generally, whatever covers more total surface area is best. In this case the surface areas are close, but the MegaTraps are much larger. So two MegaTraps (four feet high) will be better than one MondoTrap.

--Ethan

[bpape]

@ Steve - Thanks. I've seen Real Traps and GIK Acoustics not available Downunder.


Zydeco

While we don't have a dealer in Austrailia (don't have any dealers actually...) we have certainly shipped products to there before. 

Your current room response doesn't look too bad realistically down in the deeper bass.  I'd be interested in seeing the decay time plots for the room.

Bryan

[Nyal Mellor]

@zydeco

From your explanation of what you hear I would be almost tempted to think that you are talking about lack of envelopment which is a very different problem to solve than bass resonances.

Honestly looking at that frequency response it is pretty flat, especially if your talking about a measurement with no smoothing. Maybe the only thing you could look at would be figuring out what path length differences are causing those nulls from 100-200Hz. They are probably front wall and side wall related.

Your room is quite narrow and small and may be overdamped (i.e. rt60 too low), so you may want to actually pull some of those bookshelves out and use some diffusion like RPG BAD panels.

Maybe you could post RT60 and the spectral decay plot from room eq wizard? That would help

[zydeco]

@ Ethan / Bryan – Thanks for the information

@ Nyal

Interesting. I’d describe not being immersed in the music so you’re idea regards lack of envelopment might be correct. The additional RT60 and Impulse response for the 20 to 500Hz sweeps are attached. I limited the measurements to this range given the limited accuracy of the Radio Shack meter but, if it’s useful, then I could set-up the measurement system again to provide a 20 to 10,000Hz measurement .







You mentioned figuring out path length differences. I’ve run this  calculator www.harman.com/EN-US/OurCompany/Technologyleadership/Pages/Calculators.aspx?CategoryID=Calculators with the attached results.



The idea of removing the bookshelves has crossed my mind but it’s a difficult ask in our small home – but some stand-mounted diffusion panels (which can removed when not in use) would be acceptable to the better half.

Thanks for all your assistance.

Zydeco

[Nyal Mellor]

@Zydeco

Need RT60 over a larger frequency range to evaluate. Hypothesis we're testing here is that your RT60 is too low.

Could you post the waterfall or spectral decay plot (think this is called the CSD in room eq wizard).

The calculator you used is a room mode calculator. I was referring to speaker boundary interference when I talked about path length difference. Basically you need to subtract the direct distance from the speaker to the listener from the indirect distance via one of the primary reflection (i.e. mirror) points.

[zydeco]

@Nyal

Thanks. I'll report back in a couple of days when I've had a chance to set-up the measurement equipment and a few full-range frequency sweeps.

Zydeco

[Nyal Mellor]

And look here for information on SBIR and a useful calculator http://www.realtraps.com/sbirlbir.htm

[jimdgoulding]

I got something for you to try.  Make your triangle 7.0' or 6.10' or 6.8' (my room is 12'W, also).  This will enable you to pull your speakers out further to match up the legs of your triangle.  This will change things up appreciably.  Your stage may even expand.  Think of this as a wholistic approach to optimizing your loudspeaker/room interaction (borrowed that phrase from Duke).  Having done that, try listening again with and without that plyboard covering your fireplace.

[zydeco]

@ Nyal

Ok, it’s taken some time but I’ve made moved the listening position a little closer to the speakers and re-set all the books to, hopefully, improve diffusion off the sidewall bookcases. All this does seem to have helped increase the openness but the music still doesn’t envelop the listener and there is a slight harness.

I’ve managed to conduct some additional REW sweeps (which entailed fixing the desktop computer) over the range 20 to 10,000Hz using the Radio Shack and have attached the results. The overall frequency response looks, like before, quite reasonable but the RT60 seems to have a large peak around 3-4kHz. I don’t understand the significance of this anomaly. One point is that might be relevant in the interpretation is that my cross-over from mid-range to (silk dome) tweeter is around 4kHz.








Edit: Well, I've redone the measurements after making an ever-so-small adjustment to the gain applied in the active x/o to the highs. You'll see that this has more or less removed the RT60 peak so the entire range of 20 to 10,000Hz is in the range 0.2 to 0.6. The impact on music, however, isn't profound - yes there is a little less detail but still not quite enveloped in sound. Any and all advice welcomed.


Regards,
Zydeco

[bpape]

My guess is that you have something in the structure or something in terms of furnishings in the room that is ringing at that higher frequency peak.  I'd play that tone (watch the level) and wander around the room and see if you can pinpoint what it is.  Vases, glass for any cabinet doors, ceramic lamps, etc. would be potential candidates.

Bryan

[zydeco]

Here's the updated RT60 following the change to the x/o.




Regards,
zydeco

[eclein]

Can I jump in here and ask a question. The corner bass traps help to increase or decrease bass output?? I'm guessing lower freqs. down like corners in rooms and your bass output will increase with corner traps. Is that correct? Sorry to jump in but its something I need to learn more about. Thanks
 Ed L.

[Nuance]

Can you post the waterfall plots, perhaps the before and afters of adding bass traps?  Bass ringing should have decreased dramatically after installing the traps.  Also, use the default REW graph limits (Top - 105 and Bottom - 45).  For displaying the frequency response (filter adjust tab) set the left to 15Hz and Right to 500 or so.  Also, you can apply 1/3 octave smoothing if you're going to post a full range sweep.  When displaying the waterfall's, use 15-100 for one pic, then take another separate one of 100-500Hz and maybe 500-1000Hz.