how to tame the highs through room treatment?

jeremyjustic

jeremyjustic

Analog
Hi Guys, in the last couple of weeks I have been completely rethinking my entire system. I have gone from a bi-amped mcintosh system using a dbx driverack pa for auto room correction and mcintosh c33 preamp to a Threshold s300 amplifier and a custom SirByrd passive preamp. Well all I can say is the passive/threshold system has a level of transparency and life like detail like I have never heard. suddenly I completely understand what people mean when they say a preamp "gets out of the way of the music" or "it sounds like nothing". The passive really makes you feel closer to the music. the openness of the sound is outstanding.

here's the problem. The highs are just a touch bright for my taste, not so much that it is shrill or fatiguing but a little forward and on certain recordings stats to break up a bit. The sound is truly a radical departure from the processed, room corrected, ultra warm sound of the mac's. I have tried using the dbx with the passive and it sucked the life and all this new found transparency and openess out of the music, also tried going back to the Mac preamp, while it is very polite and sounds great, again it just isnt as open as the passive.

With all the talk of room treatments being the better way to go over tone controls I thought maybe some treatments would allow me to tame the highs a bit and still have the open , transparent sound of the passive/threshold system. I really just dont know where to start and could use some help.

The room: The room is plastered walls and odd shaped. I have a small diy room treatment in the first reflection point and one behind the system hanging on the wall.

are there specific treatments to tame high frequencies? what should I be looking into? any and all advice would be greatly appreciated. thanks so much guys.
 
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Last year I tried DRC with a dbx Driverack. :scratch2:

It lasted two days in my system. :no:

I think you'll find the organic approach to "room correction" more fruitful and pleasing.....even if it isn't dead nuts accurate. Can you throw up some pics of the room from several different vantage points?

Describe the construction of the panels that you already have.

If you haven't read this, then take a gander and follow the links as well (it sounds like you're already familiar with the subject matter, but there are suggestions for panel placement in there as well).....

http://audiokarma.org/forums/showthread.php?t=446798

One thing you likely will not be able to get total control over with anything less than a very aggressive acoustic treatment scenario is the the first few octaves (125Hz and lower). The silver bullet for that region is distributed bass.

- Michael
 
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Room dimensions and speaker placement within room (including toe in) are the most important parameters. Walls are bad. Volume level impacts this too. ymmv
 
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jeremyjustic said:
Thanks guys, when I get home tonight I will post some photos and a diagram of the room. I really appreciate the help!
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I appreciate you asking for help and can assure you I'll derive great pleasure from assisting (a little creepy? maybe? probably? My hands ARE NOT in my pockets right now...just to be clear). :yes:
 
Taming the highs is the easy part. Well, not always easy as there's plenty to do wrong, but certainly doable. Taming the room modes (low end of the spectrum) is the hard part.

High frequencies are directional for the most part so they behave like beams. Putting absorbers at the first reflection points is the first step.

Depending on your room geometry and size and your listening position inside the room, a QRD diffuser in the back wall will help diffuse the reflections without taking away the energy as an absorber does.

In order to do this properly you need an energy-time graph that s/w like REW can produce for you. Being able to move things around in the room is sometimes essential - the more freedoms of choice available the better.

But let me ask you: How have you reached the conclusion that it's the room at fault here? Sometimes things like capacitance load matching for the phono cartridge can fix this (provided that's your source).

You could start by measuring your room (decay rate and ETF charts) to see that there's something to fix there. Otherwise, trying to fix something when it's not at fault, can add to the problem.

Giving out a floor plan as well as pictures of the room across all four directions would help understand the situation.
 
ok thanks for all the help guys, here are some photos and dimensions.

The room is 21' wide all together, the front side of the room is 13'deep by 12'wide then it goes down to 11' deep by 9' wide. so the couch sits in a bit of an alcove with a 2' wall right next to my listening position, this has been the crux of my set up since I moved in to this house. I have a diy absorption panel next to the couch to catch the standing bass waves in that corner, I also tried to position the speakers with the right one about even with that side wall.

Speakers are Dali Ikon 6

speaker placement: they are positioned about 20" from the back wall, 5.5' from the left wall and 7.5' from the right wall (facing the speakers)

I do have a little bit of slap echo so I made two more diy absorption panels, one in the left first reflection point and one hanging behind the system, the square piece hanging on the wall wrapped in the green and white vintage japanese wrapping cloth.

ok so please excuse the mess in my living room, the whole house seems to be in flux right now so stuff in thrown around a bit, also pay no attention to the dead ass couch! hahahaha







thanks again guys, I have been playing with speaker placement and moving the right speaker over a touch seems to have tamed the highs a bit. I also tried the Sonus Faber concertinos in place of the dali ikon 6's. now they dont have the slight harshness in the highs, they also dont have the same 3d holographic highs that the ikon 6's are known for. I cant really decide which I like better. both sound great.
 
Just a quick glance at the side boundary layers reveals a lot of reflective surface area from glass, walls (sheet rock, I presume), wall art and other hard surfaces such as the books on the shelves (I don't buy into the "staggered books for diffusion" thing....at best they will scatter sonic content in an uncontrolled fashion and the distribution of frequencies is so random there is no telling what frequencies are being directed at the listening position). A few questions and observations...

1) Is the DIY absorption panel at left wall first reflection the blue fabric inside the green frame above the green chair? If so, then it looks like the bottom of that device is four-and-a-half, maybe five feet off the floor.....which is too high. You need the center of the panel to be even with your head when you're in your seated listening position.

2) I'm guessing the DIY absorption panel you have next to the couch (to address the standing wave) is shoved down between the couch and wall. I'd be willing to bet the couch is a better absorber of LF content than that panel. To get effective absorption below 125 Hz you have to have 6" of OC703 or a thin, absorptive membrane over 4" or 2" (depending on what range of LF content you're trying to absorb) of OC703. It doesn't look like there's any more than a few inches of thickness with that panel next to the couch. I think you should commission that panel to attack mid range content, so it would better serve you up on one of the walls catching an early reflection.

3) Just what are those DIY absorption panels made of, anyway?

4) Do you use the chair close to the couch as your listening chair (moved to the center for listening) or is the couch your primary listening position?

5) And just to be clear....the front wall (wall behind the speakers) is 21' wide and the distance from the front wall to the rear wall is what?
 
tomlinmgt said:
Just a quick glance at the side boundary layers reveals a lot of reflective surface area from glass, walls (sheet rock, I presume), wall art and other hard surfaces such as the books on the shelves (I don't buy into the "staggered books for diffusion" thing....at best they will scatter sonic content in an uncontrolled fashion and the distribution of frequencies is so random there is no telling what frequencies are being directed at the listening position). A few questions and observations...

1) Is the DIY absorption panel at left wall first reflection the blue fabric inside the green frame above the green chair? If so, then it looks like the bottom of that device is four-and-a-half, maybe five feet off the floor.....which is too high. You need the center of the panel to be even with your head when you're in your seated listening position.

2) I'm guessing the DIY absorption panel you have next to the couch (to address the standing wave) is shoved down between the couch and wall. I'd be willing to bet the couch is a better absorber of LF content than that panel. To get effective absorption below 125 Hz you have to have 6" of OC703 or a thin, absorptive membrane over 4" or 2" (depending on what range of LF content you're trying to absorb) of OC703. It doesn't look like there's any more than a few inches of thickness with that panel next to the couch. I think you should commission that panel to attack mid range content, so it would better serve you up on one of the walls catching an early reflection.

3) Just what are those DIY absorption panels made of, anyway?

4) Do you use the chair close to the couch as your listening chair (moved to the center for listening) or is the couch your primary listening position?

5) And just to be clear....the front wall (wall behind the speakers) is 21' wide and the distance from the front wall to the rear wall is what?
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Thanks for the input Tom!

1) No that is just a painting, the diy panel is at the bottom next to the chair, I feel this wall is my biggest obstacle.

2) I'll try moving the couch over and see , before I thought it put my listening position too close to that side wall. I'll give it a try and see if that helps, I could use the panel in other ares for sure.

3) I made them with ownes corning 703, a 2" wood frame with the 703 on top of it and burlap. I have 3 more 2x4 pieces of the 703 to use also.

4) The couch is my listening position, my girlfriend loves chairs so the blue rocker has to stay, I think the extra padding in the room cant hurt, I could easily move it over to in front of the couch for listening if you think that would help, I'll try it tonight and see.

5)so the wall with the gear is 21' wide, the room is 12' deep and 9'deep.

again thanks so much, listening to some cd's this morning and was stunned at the sound. The passive preamp really gives the highs a open, airy sound. 3d like you can walk around on the soundstage. I dont think it will take much to calm the room down and get some really serious sound. Very excited about this project.
 
also I am in need of some more record room so I will be building some more record boxes that could possibly be strategically placed to help as well.
 
Ok, so that gives me some more good info to work with. First, please let me be clear I'm here to offer more than just a solution to taming any high frequencies that may be out of control....I want to see you get as much spectral content under control as possible while taking into consideration how far you're willing to take this endeavor. Fortunately, I think your starting point is a good one as you already have accepted your situation is less than ideal, show a desire and willingness to improve it, have already attempted some improvement with your DIY devices, and have a room that is not too difficult to work with.

If you want to keep the couch where it is and continue to have that as your primary listening spot then that's fine....we can work with that, no problem. Any reflections or acoustic issues created by that wall next to the couch can be dealt with. If you're willing to rearrange some wall art then we can proceed with a proper treatment scenario that I'm confident will offer a noticeable improvement to fidelity. First, we need to establish exactly where side wall first reflection is. But before that I need to know if you have the speakers positioned exactly where you like them. I generally position them for best bass production (as heard from the listening position) and then deal with optimizing imaging and sound stage by adjusting toe in and letting the room treatments "do their thang". Once you've determined the speaker placement that creates the most balanced LF response (not necessarily the deepest) then find the side wall first reflection location to the left and right using the mirror technique and describe exactly where those points are located on the left and right walls.

And is there around 19-20' between the general location of the speakers and your listening position on the couch?

- Michael
 
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Michael, thanks, sorry I called you Tom earlier. I just looked at the user name and guessed.

ok so I am excited to start this endeavor. I am ready willing and able to try just about anything, but please keep in mind I do have a girlfriend and while she is very understanding some things are nonnegotiable, you know how it is. I am perfectly willing to rearrange anything on the walls. I am pretty happy with speaker placement, front of the speaker is 32" from rear wall, no toe in.

The first reflection on the left side in right next to the green chair where the small diy panel is. Man after reading your earlier post I realized it is too low to really do anything and should be higher up at tweeter height to work, makes perfect sense. right side first reflection is one of the book cases, not much I can do there, my girl is a librarian so we have a ton of books in the house. at least that book shelf is mostly paper backs.

my seating position is about 9' from the speakers, I wish my room was big enough to sit 19'-20' from the speakers!

I have some weekend projects so it will be a day or two before I can really dive in. where should I start? whats the first order of business?

Thanks, Jeremy
 
Let's start off with some experimentation (just testing the waters here). Two things.....first, can you run audio from a computer or smart phone through your rig? Second, do you have any burlap left over?....because I'm eventually going to want you to take those unused 703 panels and start trying them in different spots around the room but doubt you and your chick would appreciate the stray glass fibers the naked panels have a tendency to leave behind (if you don't have enough burlap to wrap 'em up then just be very careful to not agitate them when moving them around and place towels underneath them wherever you set them down). But before you do any of that take that panel you've wedged down between the couch and the wall and prop it up on the back of the couch behind your head and see what happens. If you hear a change for the better then pick a few reference songs that you know inside and out, backwards and forwards and give each of them several listens.

Once your ears have had a chance to cue in on the changes the next thing I'd like you to try is to take the coffee table that's sitting in front of the couch, place it against the left side wall at first reflection and set the DIY panel you have at that location on top of it so it can be brought up to a proper height. Then take one of the unused 703 panels and (temporarily) set it up at first reflection on the right side (and yes, get something under it so it can be raised off the floor at least a foot). What I want to determine here is if you're really even going to benefit much from absorption at the side walls. You see, with the room being 21' wide and the listening position being only 9' from the speakers the vector directly from the speakers to your listening position is quite a bit shorter than the combined vectors of speakers to side wall first reflection and side wall first reflection to your listening position.....so you may have enough of a delta between those vectors that the reflection from the side walls is not an early reflection. The wall behind the couch is creating your earliest reflection followed by the floor and ceiling (and since you have carpet on the floor you already have some control of the reflection from the horizontal boundary layers) so once it's been determined what happens when you get reflections from those surfaces under control you may find absorption at the side walls unnecessary. By just chewing on the numbers a bit I'd say you're right at the borderline of needing/not needing. And it may be a situation where having absorption there doesn't do much to tighten up the images or improve sound stage resolution, but an improvement in tonal clarity is realized. You'll just have to try it and see. :) :smoke:
 
Success!

Ok so I didnt have much time today to mess around but I did have some success. First I took the diy panel out from next to the couch, pushed the couch over and put that panel behind my head on the back of the couch. This had a pretty dramatic effect. I immediately noticed a reduction in the high freq ringing, like someone turned off the reverb. I didnt even realize how bad the reverb was until it wasnt there. What was really nice about this experiment was it was real easy to take the panel away and put it back so A/Bing was quick and very informative.

This evening I took both panels and set them on top of each other in the first reflection point on the left side, the closest wall, set two pillows behind the couch and put on Kind of blue....WOW! best sound I have had in my system yet. 3d imaging, clarity and airiness to the highs, excellent soundstage width and depth, absolutely no harshness and retained the openness and transparency I am falling in love with. a huge step in the right direction.

Even though we are really just getting started I am pretty excited with the results of this easy experiment so far.

One Thing I did notice is the bass seems to be a lot more prominent to the point that I pretty much turned the sub all the way down and still have a little bass bloom. I would like to get it a little tighter in the lower octaves.

what I was thinking was making a large panel for the left side first reflection, one whole piece of the 703 which is 2x4' I think. sticking the two smaller one I already have behind the speakers and making a wide thin one to go behind the couch under the map, even with my ears and one on the side wall next to the listening position. How does that sound?

also in very exciting news I spoke with my girlfriend tonight and she is on board with whatever room treatments we need to put up, perfect.

And yes I have a laptop in the system running foobar playing flac through a dragonfly.
 
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jeremyjustic said:
Ok so I didnt have much time today to mess around but I did have some success. First I took the diy panel out from next to the couch, pushed the couch over and put that panel behind my head on the back of the couch. This had a pretty dramatic effect. I immediately noticed a reduction in the high freq ringing, like someone turned off the reverb. I didnt even realize how bad the reverb was until it wasnt there. What was really nice about this experiment was it was real easy to take the panel away and put it back so A/Bing was quick and very informative.

This evening I took both panels and set them on top of each other in the first reflection point on the left side, the closest wall, set two pillows behind the couch and put on Kind of blue....WOW! best sound I have had in my system yet. 3d imaging, clarity and airiness to the highs, excellent soundstage width and depth, absolutely no harshness and retained the openness and transparency I am falling in love with. a huge step in the right direction.

Even though we are really just getting started I am pretty excited with the results of this easy experiment so far.

One Thing I did notice is the bass seems to be a lot more prominent to the point that I pretty much turned the sub all the way down and still have a little bass bloom. I would like to get it a little tighter in the lower octaves.

what I was thinking was making a large panel for the left side first reflection, one whole piece of the 703 which is 2x4' I think. sticking the two smaller one I already have behind the speakers and making a wide thin one to go behind the couch under the map, even with my ears and one on the side wall next to the listening position. How does that sound?

also in very exciting news I spoke with my girlfriend tonight and she is on board with whatever room treatments we need to put up, perfect.

And yes I have a laptop in the system running foobar playing flac through a dragonfly.
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Excellent! I think all of your proposed implementation ideas are solid and almost exactly what I'd suggest you do next. Now that I know the left wall is closer to the listening position than the right wall I can confirm for you that having any absorption on the right wall is less of an issue. It may ultimately be beneficial to put some there when you get down to some fine tweaking, but on a macro scale you should be fine just treating the left wall only (and yes, with a 2x4 panel). Panels on the front wall (behind speakers) will help tighten up mid and upper bass, but if you want to get that entire range of mid/upper bass content (down to 125 Hz) you're going to have to have either 4" thickness of 703 or 2" thickness with at least 12" of airspace between the panel and the wall. Obviously, the former would be much less intrusive into the room than the latter and you can simply double up your 2" panels to get the 4" of absorption thickness. And having those panels closer to the floor or ceiling rather than near the center of the wall is more effective since LF tends to accumulate in horizontal corners just like it does vertical corners. A 2x4 panel mounted about 6" off the floor and using 4' as the vertical dimension has worked well for me. A third panel behind the equipment rack will only tighten up the LF response that much more, but panels straddling or butted into the vertical corners is even better. The number of panels you elect to implement just depends on how far you're willing and able to take your treatment scenario based on your own situation. I have a feeling it will take a lot of panels before you start to find that room of yours becomes too "dead" and up to that point every panel will help. But as you've already realized, it doesn't take much to start to hear improvement. But also noteworthy is you didn't realize you had problems/the extent of the problems until you corrected them ...and such is the case in almost every example I know of when one starts to implement acoustic treatments into their listening space. That's why when someone with no treatments claims "Treatments? I don't need no stinkin' acoustic treatments.....my room doesn't have any issues...it's fine" I'm compelled to raise an eyebrow.

The reason I asked if computer audio can be a source for your rig is because you can use some online tone generators to get some measurements of your room.....that way we can get a better idea of what's really happening in there. This will also take much of the guesswork out of getting your sub dialed in for optimum integration, placement, etc. You'll also need a spectrum analyzer/output meter app for your smartphone and the one I like is Octave. See if you can get that one (I have it on my iphone 5) or something similar.
 
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ok so I have realized I need to sort some things out in the room before going to much further. first we are getting a new couch, not sure the size or layout yet. second is I need to build some more record boxes because I am one record shopping day away from pushing maximum capacity.

I will keep you guys posted and get back to this project when we get the couch and record storage sorted. hopefully this week.......
 
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