A difficult one for laymen as myself (maybe Rives could help here). My spontaneous reaction would be to tame 1st reflections on the side walls, and check for hard reflecting surfaces elsewhere. OTOH, as your imaging is good, I wonder if that's the culprit.
You may want to check out nodes with a simple standing waves calculator at marktaw.com: you just enter your room dimensions for a simulation of standing waves in your listening area. Rives' site also has some info/guidelines.
But you've probably done that already... Good luck |
Tom, I would suggest that you obtain a Radio Shack SPL meter and a Stereophile (or similar test CD) and make readings over the entire audio frequency at both the listening position and from 1-foot from each speaker. This will tell you if the problem lies with the room or equipment - if it's the room, the speaker readings will be relatively flat while the listening position readings vary. If the speaker readings are not flat, and the listening position reflects the same pattern, it's most likely the equipment.
You might find that it's not a bright room - doesn't sound like one, but I'm not the expert (ask Rives). But you might find that the low frequency standing waves are not uniform around the listening position. Just a start, not a solution. |
I suggest you experiment with treating the "notched out" area behind the sofa. If this helps, you can explore some permanent treatments.
JD |
Tom, You have nice stuff and a nice set up. The one thing you don't mention is the toe in of your speakers. Many speakers are hot if you listen to them on axis. A lot of manufacturers recommend that they be pointed straight ahead for proper imaging etc for just that reason. If you have a wall just 2 feet away you could easily get excessive reflections. I have speakers that should be, optimally pointed straight ahead. I had an idea one day, tried it and it worked just great in a room of similar size and speaker placement as yours. I measured the angle from the line perpendicular to the speaker when it was pointed straight ahead to the head at the listening chair (it was about 20 degrees) and then to duplicate the exact same sound waves from the speaker and eliminate the reflections I toed the speakers in 20 degrees past the listening position. It looks unusual but it really worked! By the way it also helped with ceiling reflections (I have 9'ers). And as side benefit - If you sit to either side of the listening position in a chair in front of the speaker you get a pretty good center image, due mainly to the distance that the signal has to travel is off set by the roll off of the signal as it goes further off axis in the speaker directly ahead. This does not occur with other set ups where the center image wants to remain right in front of you. Sort of neat in a way. Anyway, its fun to play with. Good luck. |
Disclaimer: I am a dealer for Eighth Nerve.
Tom,
Hello...Do you here any echo when you clap your hands (even the slightest amount can cause significant increases in "brightness")? Also, do you here this on all recordings?
Very good (and sanely priced) room treatment products can be purchased from Eighth Nerve. The majority of room treatment products work well, but the prices are usually quite ridiculous. We searched for a LONG time before finding this company and have been VERY impressed with their products and service. Anyway, you may not need any room treatment at all, just wanted to bring this company up as a possibility. I don't believe that your system is the culprit. Do the B&W speakers sound brighter to you than the Von Schweikert's?
Regards...Mike - Father & Son Audio |
thanks for the responses so far
I'll check into the side wall reflections (usually they are less in a long wall setup), and the ceiling direct arrival.
The back wall probably needs dampening - maybe I can test it out with simple tapestery or rug and then go further The spl meter and test cd sounds like a good step. The imaging is quite good, but perhaps it can be better.
Speakers are slightly toed in 5-10 degrees, did a lot of placement to get my imaging but haven't tried over towing them.
Has anyone tried RPG, ASC, Acoustic First or other diffusor and absorbtion materials? Are there companies you'd recommend who will sell products based on a full room analysis approach?
thanks
Tom |
Have you tried any vibration/isolation tweaks? Sometimes vibration problems can show as extra brightness at higher volumes. |
Sorry to enter the discussion so late, but I was travelling last week. I've said this before in other discussions, but you have 2 approaches. One is a trial and error, which is not as bad as it might sound for the basics, the other is to hire a group like ours to do the plans. In the trial and error method I would look at the first reflection points, both ceiling and walls. If possible try diffusion on the ceiling and absorption on the walls. The second area is to work on speaker placement (including toe in). If you go to our site there is a tutorial on speaker placement in the "listening room" section. http://www.rivesaudio.com/listroom.htmlThere are many tips in the listening room section and hopefully it will help considerably if you like the experimentation aspect (it is actually fun if you have the patience for it). Two tools that are useful for helping you determine the severity of your problem and possible solutions. One is the Radio Shack SPL meter (already mentioned), but either use our Test CD which corrects for the non-linearities of the meter or download the correction values which are found on the instructions. (This can be downloaded from our site as well). The other tool is the CARA 2.1 software. It is an room acoustics simulator and can help determine what some possible solutions for your problem might be (we sell this as well, so I may be a bit biased here, but I do think it is a very good value). You can basically model your room, make changes, and see what the theoretical results of your changes are. It does take some time to use and is not the most intuitive program--but is very very flexible and the best I've seen of it's kind so far. One caution on hiring groups that sell pre fabricated material, they are in the business of selling material. We only sell designs and have no interest in filling up your room with unnecessary items. In fact, we try to use existing furnishings and standard products where ever possible to keep costs down for our clients. In many cases our design costs are offset by the savings in acoustical treatment. |
Thanks for all the imput so far.
I bought the SPL from Radio Shack and am awaiting the test discs in the mail
I tried the clap tests and get a clap with some overtones from the walls (not a long delay seperate echo but a spread out clap) then there is a reflective sound maybe 1/4 to 1/2 sec after that rises in pitch/volume and seems high freq. This may be a reflection from the glass on my cd cabinet (I think I'll remove the glass and see if things improve.) |
The analog RatShack SPL meter is better - shows peaks better due to faster response. I tape mine to a wooden cloth drying rack as reflections from your body / sofa etc. will affect frequency response.
As people have said, 1st reflections are importnant to fix but I had glass windows behind my speakers and putting blinds over them helped some too. Also carpeting on floors.
What I did was masking tape heavy blankets to all the walls and put some on the floor. This is a cheap experiment but blankets may not attenuate the harmful frequencies. For that you can buy absorbing pads tuned to absorb certain frequencies.
One other thought, if your amps produces it, your speakers will too. If the source or amp is the problem, room treatment can't do much to fix the problem which is already there. But this is my unscientific opinion and may not have any merit. |
Hang blanket(thick one) around the wall, and see if the echo from clapping hands disappear or getting less. The brightness should be gone if it is the cause. You can even find specific area of wall is crucial. Congratulations! a few hundred bucks of treatment will make your $$$ set up sound like the price tag should be. If you don't mind the look, 100 or 200 bucks may be enough. If you or your family care a better looking room, get some pro-look stuff.
This is most efficient tweek IMH, much better than people arguing about which CD player is beter. A good treatment will make all CD's/LP's sound better. |
I brought a pair of JM Labs 926 home to audition this weekend. Like the Von Schweikerts they disappear and image well in the room.
These also sound congested at higher volumes. Quieter passages especially with acoustic guitars or piano sound tonally correct and more vibrant passages sound congested and are harder to listen to for long periods of time
Sounds like I may need to treat the room - slap echo effect?
I need to run the radio shack/stereophile frequency tests to see the spectrum end |
I did the spl tests with the stereophile cd and found distinct differences between the 3ft away source and the listening position. Will post later (at home). Not sure I believe all the distinct differences and want a second source test to verify
Rives I ordered your test cd and the Cara room software
Will investigate tube traps for the corners, absorbtion and removing all glass possible from the room.
Tom |
The reason you are doing two measurements is to determine if the problem areas are solely at the listening position (sitting in a peak or a null), or if the problem is broader than that--a true frequency "suck out" or boost. Most cases are a combination of the two. The first thing you want to do is get to a position with the least problems. The CARA software will help you do this much faster. Once you are there you want to take another series of measurements and see how close or far off from a flat response you have. |
RIVEs
thanks for the input
Yes, I'm aware of the near field / far field differences, my results were a little confusing as the levels between the two were a bit variable. Hence looking into your Radio shack spl equilibrated test disc.
Yes it appears my seating area has more room effects associated with it. I ordered your disc and the Cara software to better help decipher these issues.
thanks
Tom |
It was hard to match levels with the levels going down all the way to the 55-60 spl end, so I had to increase volume for the test
here are my results nearfield and listening position
freq near listening
20hz 51 77
25 51 84
31.5 55 87
40 55 94
50 58 90
63 69 85
80 69 86
100 75 92
125 75 92
160 85 94
200 84 92.5
mid
250 84 93
315 88 91
400 89 89
500 92 92
630 92 94
800 93 88
1k 96 91
1.25 97 93
1.6 95.5 91
2 97 88
highs
2.5 97 89
3.15 98 91
4 99.5 93
5 101.5 95
6.3 99.5 91
8 100 89
10 97 88
12.5 94 85
16 91 79
20 86 76
speaker low freq rolloff is expected, looks like the room has overemphasis in the bass and lower midrange and some attenuation in the high end.
Now to go from measurements to treatments? |
Looks like something happened to our post. We went into some detail on what to look at and some caveats--but I returned to the thread to find that it's not there. Anyway, you do have a few frequencies giving you trouble such as 160. 40 Hz appears to be a placement issue. Mid range could probably use some diffusion and high frequency appears to be overly damped. I can't say all of this for sure without more information, but it seems most probable. Two things to do from here. One is download the SPL instructions from our site, if you haven't already. It goes into some of the caveats that you may run into from this point forward. The other thing is once you get CARA and model your room compare it to these measurements. If they are close--that is very good and you can then further use CARA to simulate changes in the room and discover what it is likely to do to the frequency response and reverberation times. As you can see, this is not the easiest part of a sound system to tackle. It's not like--well let's listen to CD player A vs CD player B. That's why the room is so often ignored as you pointed out at the beginning of your post. Everything is interconnected and very dependent on each other in the room--but you are going about it in the right way--continue, take your time, and it will pay off. |
Rives
I borrowed an assortment of tube traps - old not all cosmetically there, from my local dealer - he had these in a storage area. Looks like it tamed a lot of my lower freq problems - did more measurements and much less bass bloating, sounds better but I'm not quite there
Anyway, I'll print the new results and can't wait to get my hands on the CARA software
thanks
Tom |
I probably wouldn't have recommended those traps, but since you have the traps (and they were free), work on their placement critically. The distance from the corner determines the peak frequency attenuation. Off center will broaden this band symetrical placement in the corner will narrow the band. To complicate matters the distance of the speaker to the trap and the corner also play an important role. There are actually multiple combinations that can be used for a variety of results--too lengthy to go into here. I'll be interested in your results. There is no question you can and will make improvements, but I probably would have pursued a different route if you had to pay full price for the traps. |
Rives
I didn't get them free, I am merely trying them out
Even though I've been a loyal customer, this dealer wants top dollar for most things, even cosmetically flawed older pieces, we will see what he offers.
I did measure the responses again with the traps in and the bass bloat is nearly all gone. Will post later.
So what type of recommendations were you leaning to?
The Cara software was on my doorstep (2day turnaround, wow, thanks!) and I've built the room (has notches) and a couch so far, slow but I'm learning
thanks
Tom |
The problems with bass traps is they generally absorb broad band, and are usually not efficient enough to do the job. Yes, they claim efficiency of 90%, but that's for a very small area relative to the walls that are creating the problem. The result is usally a change of about 5%, which almost not detectable. The tips I gave you on placement will help considerably, but it's still kind of inefficient. There are other designs that we do, and a few companies make some pre-fabricated designs that are similar that are capacitive type. They are more efficient and actually counter balance the frequency that has the problem. They are also much narrower in bandwidth, which means they hopefully won't degrade frequencies that do not need correction. Now that being said, you have a set of bass traps to use, do it! It's not costing you anything yet--except time (which can be expensive--but fun too). You may be able to get them to work for you in your situation and if you can, then that's what makes sense to do. If you can't get them to work and find the limitations I've mentioned a problem, then you might consider one of the alternatives.
I'm glad you got the CARA fast. We try to get all orders out that day or at the latest the following business day. We use USPS for all software orders and quite frankly have been consistently impressed with how fast it's delivered. |
