Room treatment to fix issues and add depth

[No.4]

19 hours ago, Endo said:

 do the floor-to-ceiling, album-lined shelves contribute to rooms effectiveness?

 

 

Based on what I have read here and elsewhere, I would say they help. I'm not sure if they would absorb the reflections or diffuse them, or probably both. Along the way as I have made changes to my room such as a new larger thicker rug, different furniture, large plants etc. the differences in sound can be very noticeable. This really led me to the point where I am now. I think treating the room is the next logical step in the quest for the highest fidelity. hopefully I can achieve improvements this way that will be more noticeable than component tweaks. I have made an unofficial  promise to myself not to change any system elements until I address the issues that are present in my room. however since I started this thread I did swap out the k401s for some eliptracs. So..starting now.

[No.4]

@Chris A I revisited the group delay and spectrogram plots based on some of the different settings you appeared to be using in your previous posts. There appears to be a substantial peak just below 400hz in both of these plots. On the spectrogram there is quite a bit of activity below 400hz but it seems that the response is fairly smooth from @900hz to 8khz where it begins to have some pretty large peaks. Are the peaks in the 9k to 12k region representative of reflections?  

 

I have to admit I have been looking at digital crossovers this morning, but in staying with my promise from my previous post, for now I want to see how dialed I can get without digital correction. plus they are a little pricey.  

I really like contrast of the dark background too!

[Chris A]

26 minutes ago, No.4 said:

Are the peaks in the 9k to 12k region representative of reflections?  

Yes. All of that hash on the excess GD plot is due to early reflections.

 

Try taking a measurement with lot and lots of absorption on the floor and adjacent walls--within about 4-6 feet of the microphone.  Those group delay issues will typically disappear.  So will the "confusion" of the soundstage imaging to your ears...

[No.4]

Great, thanks Chris! I have already added a few thin denim panels around the left channel, which I will measure. Then I will add blankets and couch cushions, measure and compare. The right channel will be more of an issue to address because of the window. I don't have too many WAF issues but if I cover the window I may run into some. I should also add that even just seeing the SPL with the sub and making adjustments to the plate amp have yielded better results already. Tuning elements by ear has worked for me but I think I became complacent.

[No.4]

4 hours ago, Chris A said:

Try taking a measurement with lot and lots of absorption on the floor and adjacent walls--within about 4-6 feet of the microphone.  Those group delay issues will typically disappear.  So will the "confusion" of the soundstage imaging to your ears...

I utilized every cushion and pillow I could. There is a very noticeable change on these plots. there is still a huge peak between 300-400hz though.

[Chris A]

Try flipping the polarity of the bass bin woofer connections, then run another sweep to see if that jump in group delay at 300-400 Hz changes significantly.

 

Also, you appear to have mild reflections at about 6 and 9 feet on the tweeter portion of the spectrum.  That could be ceiling bounce (the 9-foot reflection) and side wall bounce, or perhaps a coffee or something solid that's reflecting back to the microphone. 

 

Try placing something absorptive above the tweeter to absorb the energy going toward the ceiling...and have a listen. 

 

Chris

[RoboKlipsch]

Room treatment fixes so much few really understand!  Lowering and balancing decay times and ringing is everything in playback.   A speaker...any speaker or component cannot replicate the benefit of adding absorption.   Few understand the scary booms and peaks are not desirable and are in fact limitations of their room not having too big a speaker.    So many are used to 30db peaks that shouldnt exist.  Friends come watch at high volume and realize they can have a very different experience.  Keep going!

[No.4]

19 hours ago, Chris A said:

Try flipping the polarity of the bass bin woofer connections, then run another sweep to see if that jump in group delay at 300-400 Hz changes significantly.

I reversed the connections and the peak is still there, but has been reduced by half.

19 hours ago, Chris A said:

Also, you appear to have mild reflections at about 6 and 9 feet on the tweeter portion of the spectrum.  That could be ceiling bounce (the 9-foot reflection) and side wall bounce, or perhaps a coffee or something solid that's reflecting back to the microphone. 

 

Try placing something absorptive above the tweeter to absorb the energy going toward the ceiling...and have a listen.

 

there are several items that could be reflecting very close to the tweeter like the side wall and the audio rack and sides of the amp. Part of my plan is to build a new rack that will be low enough to not have any components extend above the bass bin. With a new lower rack I can build a panel that will extend entire span between the speakers.

18 hours ago, RoboKlipsch said:

Room treatment fixes so much few really understand!  Lowering and balancing decay times and ringing is everything in playback.   A speaker...any speaker or component cannot replicate the benefit of adding absorption. Keep going!

 I foresee a lot of building, listening, and measuring in the near future. The key to this will be joining the functional with the asthetic. Should be fun.

 

I will post some plots soon. I have been having some internet issues this morning.

[Endo]

Regarding ceiling bounce: Dope from Hope, Dec. '60; PWK writes about Dr. Boner's convex designs in masonite. I realize these may not be practical for a lot of us; but imagine if there were another material, like maybe cloth with batting of some kind? Just a thought.

 

The ceiling has always seemed to me as one of the largest players in this game that gets the least attention.

[No.4]

these are the original measurements and the one of the most recent. I say one of because I lost most of what I measured yesterday and this morning. doesn't pay to be in a hurry!

[No.4]

[Chris A]

So if your SPL and phase plot also looks better, then perhaps the reversed polarity on the bass bin better matches the midrange phase at the crossover point. 

 

At what crossover frequency are you crossing from your midrange driver to your tweeter?

 

Chris

[No.4]

@Chris A 4500hz

[No.4]

3 hours ago, Endo said:

Regarding ceiling bounce: Dope from Hope, Dec. '60; PWK writes about Dr. Boner's convex designs in masonite. I realize these may not be practical for a lot of us; but imagine if there were another material, like maybe cloth with batting of some kind? Just a thought.

 

The ceiling has always seemed to me as one of the largest players in this game that gets the least attention.

I was thinking about something similar to this earlier. An effective sound absorber that is highly transparent would be very useful, especially for my large window. I will have to read that article. Maybe there is a modern material that would be better suited for this application.

[No.4]

A bundle of roxul rockboard 80 is in route. Hopefully this will be enough to cover the mid and high frequencies in the room. Once these are in place I can move on to address the low frequencies. Apparently the setup in the photo below was not going to fly.

[No.4]

@Chris A do you use any diffusion in your room, or just absorption? Several of the resources I have found recommend diffusion between the speakers and absorption to the sides. 

[Chris A]

The diffusion in my room is incidental: masonry bricks on the front wall, a large CD/DVD/BD rack and wooden shutters over windows on opposite side walls, books and LPs in a tall open bookcase, etc. that serve to break up HF and midrange frequencies. 

 

Having a room that's 40 feet deep handles the midbass and low frequencies quite well--no added diffusion is required.

 

I found that the only treatment that was needed was absorption around the K-402 horns--within 3-6 feet of the horn mouths.  I added absorption panels across the front wall to taste vs. the natural diffusion of the brick masonry. 

 

The smoothness of the group delay plot (below) shows the effectiveness of the room's absorption in controlling early reflections.   

 

The measured reverberation times vs. frequency are also plotted below for reference.

 

 

Measured group delay of the left Jubilee and subwoofers (crossed at 40 Hz) vs. frequency (note the vertical scale):

 

Chris

[pbphoto]

I always suspected my room had a few early reflections but struggled to accurately measure them.  Several times, my La Scala 2's ended up surrounded by pillows and blankets like No'4's photo above, but my impulse and RT60 graphs didn't significantly change.  I thought maybe I could hear a difference but it could have been a placebo.  However, the excessive group delay graph has helped me now - thanks Chris!  What I learned is even though I have a carpeted floor with padding over a concrete slab, it is the source of a significant amount of early reflections.  It's a commercial carpet with low loop pile.  Layering a blanket or pillow over the carpet in front of the speaker really improved my group-delay graph.  Outside of this, I took a lot of measurements with pillows and blankets everywhere, and the other major reflection point I found was the back wall about 18 feet away.  Charts below.  All measurements left speaker only, 1 meter.  I'll work on the right speaker next.

 

Excess group delay: no room treatment

 

Excess group delay: blankets on floor

 

Excess group delay: blankets on floor and rear wall

 

RT60 with blankets on floor and rear wall

 

 

 

 

 

[Chris A]

@pbphoto  Excess group delay was one of the topics discussed in D'Appolito's book Testing Loudspeakers (pgs. 112-114 and pg 135) and was mentioned that excess GD was very good way to measure phase and time misalignments.  But I've found this only works when the early reflections in-room are controlled, otherwise the phase/group delay measurements are "corned beef hash", particularly the phase measurements.  I also found that controlling those early reflections in-room also strongly affects soundstage/phantom-center imaging--something that you can easily hear.

 

The peak in your group delay plot at 3.8 kHz is likely due to tweeter/midrange horn time misalignment, since the acoustic centers of the tweeter and midrange compression drivers are not aligned with respect to the vertical plane of the La Scalas.  Since the bass bin woofer is almost within 1/4 wavelength of the midrange compression driver due to the similar path lengths of the midrange horn and the bass bin at their crossover frequency in the La Scala, the group delay of the midrange/bass bin is basically all due to the crossover filter itself: 90 degrees of phase delay on the lower frequency driver/horn relative to the higher frequency for every order past first order.

 

By the way, your room isn't "dead" by any stretch of the imagination--looking at your RT60 plot, which is showing 0.45 for reverberation time, which is relatively live.  There is a lot of conflicting information regarding how much--or whether or not--absorption treatments in-room, but the fact remains that early reflections in the immediate vicinity of your horn mouths creates imaging issues (defects in the soundstage and phantom center image) that most hi-fi enthusiasts typically turn a blind eye towards.  Once you control those early reflections, then the inherent imaging performance of the loudspeaker suddenly appears.  This is also referred to as live-end, dead-end (LEDE) treatment (...the original definition that puts the absorption at the loudspeaker-end of the room).  For best soundstage/imaging, it only takes a few absorption pads/panels around the loudspeakers to achieve large resulting sound improvement.

 

I find that there are a lot of people that either believe in or hide behind the notion that "absorption as is commonly applied is bad...diffusion which is not commonly used, is good...".  My experience is that diffusion panels of the type used by hi-fi enthusiasts are really only needed in home listening rooms having little or no furnishings and relatively small dimensions and/or low ceilings.  When was the last time you went to a movie theater and saw those "little random square block" diffusion panels that some hi-fi enthusiasts taut as "necessary" covering the walls?  Most small rooms in regular homes usually have enough furnishings, as well as wall texture and drywall compliance that do a fairly credible job of breaking up the acoustic reflections off the room boundaries: for instance carpet, bookcases, chairs, racks, tables, etc.  And most people don't realize that the diffusion panels that they see placed on walls and ceilings of some hi-fi enthusiast's listening rooms are usually only effective at midrange frequencies.  So what about midbass and bass frequencies...which typically have much more effect on the music we hear? 

 

I find that most all "audiophiles" tend to focus on the subjects that they're aware of and which they have easy answers to (focusing entirely on electronics, sharp pointed feet on loudspeakers, and "equipment synergy" ideas), but to the total neglect of doing something about the other elephants in the room--that they choose to ignore.  Early reflections happens to be one of those elephants, I've found.

 

Chris

[ClaudeJ1]

30 minutes ago, Chris A said:

I also found that controlling those early reflections in-room also strongly affects soundstage/phantom-center imaging--something that you can easily hear.

This is the EXACT reason why my Danley SH-50 horns have a VERY strong phantom center image. In many sound demos, I have to pull the connector from my center speaker to prove that it's not ON.

 

Artto, an Architect and Bass player from Chicago area, has the best stereo room I have ever heard. For a long time, he had R & L Khorns with a Belle Center channel and was featured in a few magazine articles. Around 2012, he then invested in 3 SH-50's, thinking he needed a center. After a complete change in layout, he sold me his center unit because it was simply NOT needed with Synergy horns R & L. His 3D imaging is second to none, in that room IMHO.

 

In my case, I'm using the same room/speaker/electronics/setup for both 6.2 movies and 2.2 music. The center is off for stereo, as, again, the phantom center is so very STRONG with that setup, so I am, essentially, doing the same thing as he has done for stereo listening.