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Hi Ethan,
I would like your advise regarding a weird problem im facing in my set-up. My room is 22ft long by 16 feet wide by 10 feet high. I have placed my speakers ( Monitor Audio GS 10) on the shorter wall, 4ft from the front wall & 3 feet from the side. I am sitting at the 38% you suggested. I use a Mark Levinson 331 Power amp with a Proceed Pre & Arcam Alpha 9 Cdp. No matter what isolations i try, the performane of my set-up is Forward, which i dont like, as the mid just comes at me. Im using 13 inch tubetraps in the front-corners & 9 inch right behind each speaker, & 9 inch at the 1st reflection points on the side-wall. I have just one 13 inch on the back wall behind me at the center. Please advice as to what i must do to cure this midrange being forward, I highly appreciate....
Thanks
Junaid
Follow Ups:
Is there any way you can try a long wall setup. My room is 1' shorter than yours in each dimension and it works wonderfully. Pics are in my gallery
"Man is the only animal that blushes - or needs to" Mark Twain
hi,
I too love the longer-wall setup up u mentioned. It changes the entire equation each time i put my speakers there. But in my room its just a bit not practical, coz it brings the speakers in the walking area, being prone to get moved unintentionally otherwise...
Do u use the GS 10's too?
A ship is safest at the harbour, but that's not what its made for....
Vandersteen 2Ce Signatures and I could never get them - or any others - to sound right on the short wall.
"Man is the only animal that blushes - or needs to" Mark Twain
I'd say the main problem is not having suitable absorption at the side-wall refection points. One 9-inch tube on each site is nowhere near large enough for a room that big. Same for the rear wall.
I suggest you try an experiment: Take all of your tube traps and put half on each side wall, making sure the absorbing side is facing the room. If that helps, then there's your answer.
You'll also benefit from much more bass trapping, but that's a different issue.
--Ethan
Ethan's right about the narrowness of the 9" trap as a treatment. That's the reason I said "They're only 9" wide traps so placement will need to be spot on."
A standard 2' wide panel of the sort often used for treatment of first reflections will cover a wider angle of the sound wave emitted from the speaker than a 9" trap at the same distance. Place the absorption device closer to the speaker and it covers a wider angle. You can get the same angle of coverage from the 9" trap by moving it much closer to the speaker. You still need to keep it on the line between the first reflection point on the wall and the tweeter (or inner edge of the front baffle for the front wall first reflection).
I can remember reading a review of the ASC tube traps by Jonathan Scull in Stereophile many years ago. What he did as one of his trap setup experiments was to create a wall of traps placed close to the outer edge of the speaker but aligned roughly along that first reflection path. Instead of placing half of the traps along each wall as Ethan suggests, try placing the 9" trap you're currently using on each side very close to the speaker but along the line of that first reflection path. That will ensure the trap "captures" sound from a wider angle of the speaker's radiation pattern than it will if placed close to the wall, giving you a similar kind of benefit to what you would get using a wider trap closer to the wall.
You may need to fiddle with the trap position a little in order to get maximum effect because of the narrowness of the trap but you should get absorption of a wider angle on either side of the first reflection path with the trap close to the speaker. Unfortunately by placing it that far from the wall you'll probably lose some of its effectiveness at lower frequencies but they're less critical when you're dealing with first reflections so you may still get good results.
Otherwise, if you need wider coverage close to the wall, panels are a more effective and economical approach than cylindrical traps.
You would probably get better results dealing with the side wall first reflections using Ethan's approach but then you lose the benefit of corner placement for your big traps. If you don't want to buy more traps or panels, placing the traps for the first reflections closer to the speakers may be more effective than a single trap on the wall while retaining the benefits of some corner bass trapping. What you're going to have to do if you run with the traps you have is balance the advantages of traps in the corner vs the advantages of wider coverage at the first reflection points and it's your call on which you prefer overall. There are advantages and disadvantages to both approaches.
David Aiken
Hello Mr Ethan & Mr. David,
Im very thankful for your suggestions. Does it mean that the wall reflections at the side are causing the midrange to be forward? I Do have curtains( thin ) covering the 1st reflection area, but im sure they do nothing acoustically, as they are almost see-through. I certainly do not mind adding panels, or even substituting my traps at the sides with panels. I have custom-made 2x4' panels exactly copying a DIY recipe from the internet, but have not been using them due to aesthetic reasons. But now im totally frustrated with the imbalance in sound, even after spending so much on the entire set-up, so i really do not mind in adding any amount of absorption anywhere in the room.
And Ethan, i do have the full version of ETF software since a long time, but i have never known how to use it to blend my bookshelf speakers to my subwoofer. I have been reading a lot of posts in AA by you & David & also Jon Risch, & i consider you people as Masters in the Audiophile world. You people have absolutely tremendous knowledge in both acoustics & electronics.
Given the size of my room & my set-up, what else do you suggest to improve the overall balance??? I dont mind making more panels or traps. My only regret is that. even after giving so much time & interest in setting up the whole thing, it still sounds not even close to high-end...
I don't know whether side wall first reflections cause the midrange to image too much to the front. I think there's too many variables involved with those reflections, or any reflections, to predict some effects reliably. The strength of those reflections are affected by the speaker's polar distribution pattern and angle of toe in and also by the reflectivity of the walls.
Definitely try the 2' x 4' panels at the first reflection points. I think your results will improve. That will leave you with the 9" traps spare and if your room is high enough you can try stacking them on top of the traps in your front corners which should help a bit more with control of bass modes.
You said your DIY treatments were unwrapped. If they're fibreglass and you have the fibreglass exposed, I think you should at least wrap them in a thin covering of polyester batting in order to prevent fibre release. Fibreglass may not be considered carcinogenic but fibres in the lungs can cause other problems. I think it would be hard for an adult to get a high enough concentration from exposure to unwrapped traps unless the fibreglass material was deteriorating badly but if you have carpeted floors any loose fibres are likely to collect there and small children playing on the floor are likely to receive higher exposure levels because they're more likely to disturb any fibres trapped in the carpet and also because they're going to have their mouth and nose much closer to the carpet than an adult which means they're more likely to breathe in any disturbed fibres. I'd still prefer to cover them with a cloth cover as well. Jon Risch recommends burlap which you may know as "hessian" which is what it's called here in Australia.
David Aiken
Yes, real fiberglass panels that are at least two inches thick will be infinitely better than thin curtains you can see through.
ETF will show you reflections, but you don't really need that. David and I already told you what you need to do.
--Ethan
Are you using ASC tube traps? If so, how do you have the reflective side of them oriented? I would try rotating the traps in pairs (front corners, front walls, side walls, rear wall which is single, of course) in order to see if that helps.
Another thing that comes to mind is that you have traps immediately behind each speaker. I'd try moving those traps to the first reflection points on the front wall.
You will need to be careful in placing the traps at the front and side wall first reflection points. They're only 9" wide traps so placement will need to be spot on. That won't be directly in front of the reflection point on the wall, but centred on the line between the reflection point on the wall and the speaker so it will be a little to the speaker side of the location of the reflection point on the wall. How far to the side will depend on how much space you leave between the trap and the wall. The greater the space, the further to the side. Actually increasing the space a little may help a bit and also leave you a little more leeway for error in placement.
I suspect that your best results will be with the reflective side facing away from the speakers for the traps at the first reflection points. You may get slightly better performance in the bass with the reflective side of the trap facing you or towards the speakers for the corner traps on the front wall. Having the reflective side facing forward into the room for the trap on the back wall may help provide a bit of diffusion. Ideally I'd tend to try to mirror the front wall treatment on the back wall if I could.
Now for one further suggestion which may or may not work to your taste. In his book "Sound Reproduction", Floyd Toole indicates that most people prefer the side wall first reflection points untreated because that enhances a sense of spaciousness that many people prefer but he also says that some people are very sensitive to those reflections. I don't know which group you'll fall into but I'd try moving the side wall traps to the back corners and see if that helps. It will change the sense of the spaciousness of the sound and that may take some of the forwardness off things for you, but it's also likely to change the breadth of individual images and some other aspects of the soundstage/imaging effects as well. You may prefer things with those traps in the rear corners or you may prefer it with them at the side wall first reflection points. The only way to find out is to try both locations.
David Aiken
Hi David,
Im extremely thankful that you have taken the time & interest in helping me solve my problem.
I do not have ASC tubetraps, but i have made them as per the Jon Risch recipe. The 13" traps that i have kept at the corners of the front-wall are bare with no reflector, & i have also left them un-wrapped. The reason for not covering the traps is that i have tried many fabrics, but all tend to alter the sound. So i gave-up & preferred to leave them bare, as i was unable to get an Acoustically Transparent fabric here in India. I will try bringing the 2x4' panels i have, into the room & try substituting my traps with them at the side walls.
And i cannot place any traps at the rear corners of the room, because there are doors at both those corners, one leading to the staircase, & the other leading to the bedroom. Thats exactly why i have kept a 13" midway on the back-wall. I want to upload a picture of my room so that you can have a clear idea of the entire thing. Is it possible to upload a photo on AA?
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