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I recently moved to a new apartment and a smaller listening/living room. It is 12x16 with one wall of windows, cement walls and an elevated wood floor (typical Japan). So far I've got heavy drapes with blackout liners on their way. The wall opposite the windows is all book shelves with the books pulled out in an alternating pattern to help with diffusion. There is a similar book case behind the listening chair and the room is otherwise sparsely furnished. My speakers are the wonderful Altec model 19's which are against the back wall and about a foot from the side walls. Speakers are 7' across from cone to cone and I am 10' away centered.
So far the image is stable from the mid-range up it does a decent job. The bass is so far the problem. When sitting in the listening chair it significantly decreases but once I stand it is present and boomy seeming to fill the room. The bass is equally loud when I walk into the kitchen or side bedroom which open into the living room. I'm going to lift the 19's about 4" off the floor but I can't pull them out of the corners much. I would like to work with some bass traps of some sort but am a little short of room for the Owens 703/705 2'x4' jobs. Being in Japan, fiber insulation is hard to come by in any form. I could use the foam type though I don't know if they would have enough attenuation. Any recommendations?
Thanks,
Aaron
Follow Ups:
First off thank you for your service Aaron. Lucky to have a room that size living in Japan.
I’m going to suggest an odd item that if you can buy used from Audiogon you could always sell for your money back if it did not work for you. Try the bass unit from Acoustic System Resonators. You should be able to find one used for ~$150.00. Better yet get two silver and one bass but that will cost a fair amount of cash. I’m low budget but find them to be indispensable.
Since the bass is generally too loud--when you are standing, or out of the room--it seems like you should try to correct for that first. Moving the speakers away from the wall would help because the closer a speaker is to a wall, the more it reinforces the bass. Generally, speakers work better away from the back wall because they will image better and the bass will not be boomy. If you move the speakers away from the wall, you may find that the geometry of the nodes changes so that you don't get cancellation at your sitting position. It's worth a try anyway.
There are 2 causes of "cancellation". One isn't really so much a cancellation. The high and low pressure zones that occur with a room mode are fixed in location and moving the speakers won't change them in the slightest. There is also a cancellation that occurs for the frequency whose wavelength is 4 times the distance of the speakers from the wall behind them. The frequency of this wavelength will change as you change the distance between speaker and wall but you can't avoid the cancellation by doing so. All you can do is change it's frequency. That can be used to advantage at times by moving the speaker until the frequency at which this cancellation occurs coincides with the frequency of a troublesome room mode peak so that you use the cancellation related to speaker distance from the wall to weaken a peak related to one of the room dimensions.
The problem with moving the speakers to weaken bass in this case is that the room is small and that means that there's less flexibility in how much distance you can place the speakers from the walls. In many cases you can't move them far enough from the wall in order to weaken the bass support they get from the walls sufficiently to solve a problem without ending up with them so far from the wall that their position is simply unworkable in the room.
David Aiken
What you say sounds correct. The room nodes obviously don't change, but as you said, you can use the speaker position to cancel nodes. Even if at the fundamental frequency, the speaker would have to be moved too far into the room to be practical, a smaller distance would probably cause cancellation of some overtones, and because the room is being energized differently, other wave interactions might turn out to be helpful. It's easy enough to try out. It sounds like the bass is generally too loud, so I think moving the speakers away from the walls, say about 12" is still a good idea. Since an equiiateral triangle is considered a good speaker-listener configuration, moving the chair towards the speaker along with moving the speakers out from the walls might do the trick. Moving the speakers forward would cut cown the boom, moving the chair would get it away from a cancellation zone.
Of course it would be a good idea to have bass traps and also wall absorbers placed in locations arrived at through trial and error because absorbing bass will prevent it from cancelling itself out, so any room node cancelation should be reduced.
I didn't get the feeling that the bass was too loud. What was said was "When sitting in the listening chair it significantly decreases but once I stand it is present and boomy seeming to fill the room. The bass is equally loud when I walk into the kitchen or side bedroom which open into the living room."
So the bass is low in level in the listening chair, louder and boomy when standing or in some adjacent rooms. Uneven bass response, and too low when seated which is probably the normal listening position.
As for moving the speakers 12" away from the wall, mine are a fraction less than 2 metres from the wall behind them and 1.3 metres from the side walls, measured to the centre of the front baffle. I don't think 12" is far away and I know it's way too close for the speakers I have.
David Aiken
"The bass is so far the problem. When sitting in the listening chair it significantly decreases but once I stand it is present and boomy seeming to fill the room."
The change in bass with height sounds to me like a floor to ceiling mode issue which you may be able to correct by altering your sitting height, either up or down. As you move along any room dimension (up/down, front/back, left/right) you will pass through zones where bass is stronger and zones where it is weaker. That's part of the way in which room modes behave. Since there is a difference between sitting and standing I'd say the issue is the up/down movement with you sitting with your ears in a weak bass zone and standing with your ears in a strong bass zone.
If you are also moving forward or back a bit when you stand, eg moving forward as you stand because the chair stays in the same location, then there may be a bit of movement to the front helping to move you into a stronger bass zone. You could simply try moving the chair forward a bit to see if that helps.
You will have some control over bass by moving the chair forward or back a little and/or changing your sitting height but there are limits to what you can do that way. You may be able to do enough in which case that's the simplest way to work with things.
If you can't do enough that way, then we're starting to talk bass traps and the unfortunate fact is that there really are no small bass traps. Bass traps need to be big to have an effect and you need several to really start to smooth a room's low frequency response. If possible it's recommended to go floor to ceiling with bass traps in all 4 corners. If space in the corner is an issue and mounting a 2' panel diagonally across the corner isn't possible, then you could try mounting a panel on each wall, meeting in the corner. That still leaves a bit of space in the corner that you would lose with the diagonal placement but it also requires twice as many panels.
If space does not permit bass traps then you could try one of the electronic room correction devices. They can produce some reasonable results, depending on the device you choose, but depending on the device you choose you may be limited to correcting things for only one listening position. The Audyssey system, available in some HT gear, allows you to correct over several listening positions and achieves reasonable results in my TV system but it also involves digitising your signal for the processing and you may not want to do that.
I've seen some comments on electronic devices that use an extra speaker which delivers a signal derived from the music but altered so that when it reaches your ear at the same time as the music signal from your normal speakers, it sums with the music from your speakers to produce a smooth response. I've seen mention of "electronic bass traps" designed to do this for a single room mode and systems designed to try and achieve the same result over a wider range but I can't remember names and haven't seen any in use. I do seem to remember Kal Rubinson commenting on an electronic bass trap device in Stereophile probably a couple of years ago now.
There are also people who swear by a parametric equaliser at bass frequencies and a Behringer bass equaliser is often mentioned favourably. I have no experience so I can't comment.
Sadly that's the options I can think of: making listening position adjustments to try and get a better bass balance, using bass traps, or electronic correction of some kind. I use bass traps in my listening room and I'm very happy with the results. I can say I definitely prefer the sound I get from my audio system with physical room treatments to the sound I get from my TV system which relies on electronic EQ but the audio system is considerably higher in quality than the TV system and the room the audio system is in is also a better room than the room the TV system is in so there are other factors at play there than just the difference between physical acoustic treatment and electronic correction.
David Aiken
Hello David,
Thank you for your detailed response. I agree with you and desire to use room treatments vs. electronic compensation. I've moved the the listening chair back and forth and side to side. Raising the chair is not an option though I do intend to raise the speakers some.
Bass traps seem to be the best option here. I've got some room to work and don't mind using larger pannels if needed. Do the triangular foam bass traps have much effect? Are there other effective options other than fiberglass? I only say this based on availability. I'm in the process of contacting companies in the states to see if they will ship out 703/705 via USPS.
Aaron
I doubt raising the speakers will do much but it's worth a try.
I've got no personal experience with foam traps/panels. Initially I made some DIY traps and panels from polyester and polyester/wool insulation batting but I eventually replaced them with RealTraps which are fibreglass. A friend has some foam corner wedges and tiles in his room and they certainly have helped but I'm not certain that foam is as effective as the fibreglass in the RealTraps which I certainly found more effective than my DIY efforts. The foam tiles are intended to be glued to the walls and that means that they will be less effective than an equivalent product placed out from the wall a bit so there's an air space behind them. Actually mounting any absorber directly on the wall without an air space behind it reduces effectiveness but it does save on space. If you have to go that way, the best you can do is to go for the thickest panel you can since thickness improves efficiency also.
A bit over a year ago I experimented a little with some dense cotton insulation batts intended for use in soundproofing HT rooms. They seemed more effective to me than the normal rather fluffy polyester and polyester/wool batts I had used in my earlier DIY efforts. The polyester and polyester/wool batts were lower in density and needed to be compressed in order to achieve good results at bass frequencies. The dense cotton batts were at least equal in density to my polyester batts after I had compressed them and delivered quite reasonable results but they were also about 3 times as expensive as the polyester and polyester/wool batts which I wasn't compressing to one third of their volume so they were a more expensive option than the polyester batts in some ways.
My preference so far is for the fibreglass but while I was happy to buy a finished fibreglass product, I wasn't prepared to build my own using fibreglass simply because of my concerns about fibre release during the building process. Fibreglass may not be a carcinogen but it can cause skin and breathing problems via contact and inhalation and does require safety precautions while working with it. Unless you can take those precautions I would be cautious about using it, especially if you have small children in the house since any fibres and dust released will end up on the floor where they can be trapped in carpets until released when they're disturbed. Children play close to the floor so any fibres/dust released by that play will be in their breathing zone and more likely to be inhaled, and skin contact can result in rashes. Many will say I'm being over cautious but I used to work in the health and safety area and I do have concerns about exposing others to risks when I'm doing something I want to do.
David Aiken
How much have you moved your position? Move until the bass sounds good to you. If you can't move enough then move the speakers even if you think they can't remain in those positions, (you might change your mind if the sound is good), after all the sound is the most important thing, right? LOL!!! Moving stuff around should be exhausted before traps and room treatments are tried. Then when you do the room treatments you will know if they are worthwhile because then you will have the 'position change sound' to refer to. My opinion.
I have found that in my system I can lean forward in my chair, moving my head about 2 feet or so and it makes a difference in the bass. I would try radical changes in position just to push the limits. It is an education for your ears that you will need when experimenting with treatments.
Have Fun!!!! Bill
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