@roboco, Usually, one can do a good bit with two subs. How much depends upon the room and to an extent on the mains and how low they go. In my room, I tried using two REL subs and couldn't get to where I wanted to be. However, I did not elevate either sub off the floor. Had I known to do so at that time, I almost certainly would have had better results.
AS for REW, there is a learning curve, but there is a users group forum and one can usually depend upon excellent guidance on set up and use. I was advised to utilize REW many years before I decided to do so. What a mistake. REW used properly makes everything 10 times easier. |
@ronboco, I've bought products from GIK and RealTraps. They both make excellent products. They both offer free advice on room treatment. Just be aware that they are in business to sell products, not to educate potential customers on room acoustics and relevant psychoacoustic principles. My advice to you is to spend a few months learning about room acoustics before you buy anything. I didn't do so, and wasted a bit of time and money. I wasn't going to get my room right based on advice from either one of these companies. Better, yes. Right, no.
Understand that 90% of getting a room right is getting the 20Hz-300Hz range right. Once you do that, finishing the room is rather trivial.
I'm convinced that the best, and arguably the most cost effective way to get the 20-100 Hz range right is not by using room treatments but by using multiple subs. Look on the forum for discussions regarding the Audiokinesis Swarm system.
The best, and certainly the most effective way to get the 100- 300 Hz region right is through optimal placement of speakers and main listening position. This is not trivial, but it is free, and you will never treat a room at any cost enough to overcome suboptimal placement of speakers and listening position. You can find guidance on how to do this online. However I found that a not so well known technique, which is to locate the main speakers 20% of the room width from the side walls, 20% of the room length away from the front wall, and finally positioning the listening position 20% of the room depth distance away from the rear wall works best. I found this to be optimal in my room via a laborious process using REW measurement. My experimentally optimized positioning ended up within inches of the predicted optimal positions calculated based on the 20% rule.
After doing these things, you will find adding commercial absorption and diffusion will readily address the remaining issues, e.g., slap echo, comb filtering, first reflection points, balanced direct vs reflected sound, and what ever low frequency ringing may remain.
Read and understand the information on the RealTraps and GIK websites. If you are technically inclined, install and use REW measurement to provide guidance. There is a learning curve, but most people are quite capable of catching on to how to use it profitably. Optimizing a room without measuring is like trying to find a diamond ring that is lost in a dark room. Adding REW measurement is like turning on the lights. It will still take some work to get the room right, but it becomes possible for most of us to pull it off. Good luck!
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ronboco, the room is our 2 story family room open on two sides. Not ideal. My speakers are Kanta 3 with the Kanta center channel and Kanta 1 for surrounds. What is the advantage to elevating the subs more than the feet on them already do ? Below about 300 Hz, aberrations from flat frequency response at the listening position are determined largely by the dimensions of the room. These long wave frequencies will in some cases be reinforced, and in other cases partially canceled, by reflections off of the walls, floor, and ceiling, at a given listening position. Reinforcement of certain frequencies happens when a reflection off of a surface meets the primary signal or another reflection in phase with that signal. If a reflected signal meets a primary signal out of phase, there will be a partial cancelation of that signal. Frequencies where these reinforcements and partial cancelations occur are called room modes. Some room modes are determined by room length, others by room width, and others by room heights. Still others occur (generally at less problematic levels) when in phase or out of phase signals result from reflections off of surfaces in two or three dimensions. Adding subwoofers in positions other than the position of your mains changes the location of the primary signal and also the reflected signals. By careful placement of the subs, you can significantly mitigate these reinforcements and partial cancellations. Most of us have ceilings around 7-10 ft high. Our low ceilings will result in significant deviations from flat frequency response below 100 Hz. Using a sub to mitigate those deviations requires locating the sub at a different position than the main--different in all three dimensions of the room. This is why some speaker designers who use multiple woofers mount those woofers at different heights in the speaker cabinets. If you have an irregularly shaped room, one that deviates from a symmetrical rectangle, it becomes increasingly difficult to predict room response based on the available models. It also becomes more difficult to predict optimal speaker and listening position replacement. Measurement with a sophisticated tool like REW greatly simplifies the process. You still want to use your ears as the final arbiter in making placement decisions, but trying to do all this by ear alone is just an overwhelming task. Hope this makes sense. |
I will also add an encouragement to read and absorb the excellent book by Earl Geddes. I had already spent a good bit of time and effort attempting to self educate on room acoustics and psychoacoustic principles before finding the Geddes work. As I recall, the book resulted in several "Aha" moments. It is good enough that I have reread much of it several times. For those of us who are not in the business and have no formal training in room acoustics, we are trying to achieve enough understanding of the relevant principles to successfully reduce those principles to practice in a single application--our own listening room. Most of us have jobs and families and have limited free time. It can be hard to justify spending that precious free time self educating on acoustics rather than listening to music. There is a reason why I remained clueless on room acoustics until I retired and had an abundance of free time. There is also a reason why people like Jim Smith can make a living out of helping folks set up their rooms optimally. There is a reason why a lot of serious audiophiles will just turn the decision making process over to GIK or RealTraps. The maxim, "knowledge is power" applies here. In my case, I can tell you that the efforts I have put into understanding small room acoustics has made me a better listener. It has transformed that frustrating "something is not quite right here, and I don't know exactly what it is wrong much less how to rectify it, so I will spend $5000 on a new preamp and hope that fixes it" feeling to "this deviates from a live performance with respect to XYZ, and I should change ABC to rectify that change." Five years ago I had a room full of really good equipment that sounded like crapola. Now that same equipment sounds as good or very nearly as good as set ups I've heard that cost as much as 4x the cost of my system. 5 years ago almarg offered the following comment on my systems page. Speaking of the back wall, though, meaning the wall behind the listening position, a point which might eventually prove to be significant is that reflections from that wall will tend to produce a dip in frequency response at frequencies (in Hertz) in the vicinity of about 281.5 divided by the number of feet between that wall and the listener's ears. So if that distance is around 3 feet, as appears to be the case, reflections from that wall will cause a suckout, to some degree, in the vicinity of 94 Hz or so.
The 281.5 figure, btw, corresponds to 1/4 of the speed of sound in typical indoor environments, in feet/second. Rear wall reflections at a frequency of about 281.5 divided by the distance to that wall in feet will arrive at the listener's ears exactly out of phase with the direct sound arrival. The resulting suckout can be quite pronounced IME. In two paragraphs, Al completely changed the trajectory of my audiophile experience by applying his knowledge to my particular application. His guidance wasn't opinion or personal preference, it was science based fact. Happy listening! |
Ronboco, I don't think your room is hopeless at all, but it is a different sort of puzzle than most of us have. Your room is so atypical that most of us will be hard put to offer any certain guidance about how to proceed with traditional room treatments in the absence of measurement. I would view your high ceilings as an asset with respect to room modes. Having two large openings in addition to having the high ceilings may make it a challenge to properly pressurize the room. But your room dimensions should give a relatively low Schroeder Frequency, which is that frequency below which room modes predominate, This is very good. It could mean that you will require much less bass trapping than most of us, or said in a different way, you may receive relatively modest benefit from an investment in bass traps and other treatments. REW will help you discern what your room is really doing. In addition to REW, if you are able to connect your computer to your audio system, you can play pure test tones (do a google search) while walking around the room with an SPL meter and find the locations where bass frequencies are being reinforced by in phase reflections and partially cancelled by out of phase reflections. You will be able to discern which of your room surfaces are responsible for particular room modes by noticing if the SPL levels vary while raising or lowering the meter, moving it side to side, and to an extent by moving the meter forward and backwards in the room (mindful the SPL will drop or increase as the meter moves further away from or closer to the meter). This technique could be used along with the crawl technique mentioned earlier to optimize placement of your subs.
I am about 99.9% sure that you would benefit far more by putting 3K into a distributed bass array than putting 3K into bass traps. If I were you, I would move in that direction. But if I were you I'd ask Duke LeJeune the question directly.
Since you already have two REL subs, you should be able to offset some of the cost of a DBA like the Swarm by selling them. If I were to offer advice in the absence of measurement data, that would be my advice.
With your high ceilings, you are not going to be dealing with issues like floor to ceiling slap echo and the room openings will also partially mitigate the side wall to side wall slap echo type problems. You may find yourself in an enviable position where you don't need much traditional room treatment. Time will tell.
Most of us don't want a bunch of bass traps etc in our living rooms if we can help it.
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Ronboco,
My professional background was in chemical process research and development. I learned that it was utterly futile to begin experimental work until I had a reliable analytical technique that would inform me of the result of the experiment. With respect to audio, we all use our ears, and our ears should always remain the final arbiter. The problem with listening is that we all suffer from fatigue, at which point we are not listening critically. We also tend to focus on a single variable rather than making a broad based assessment when trying to optimize by ear. On the other hand, I can work on my room for hours at a time using REW to assess the impact of a given change on overall frequency response, ringing, the balance of direct to reflected sound, early reflection mitigation, etc. I can go back a month later and look at the data and draw the same conclusions, or even discern something I missed the first time. So yes, measure first, attempt to fix a given problem optimizing existing gear second, and spend money third. However, be aware that there is a waiting period once you place an order for a Swarm, so if you are sure you are going to go that way, the sooner you order the better.
To be clear, I would make sure I had the two RELs you have optimally placed before I do anything. If that gets you where you want to be, it costs you nothing. Problem solved at no cost.
Most of the time and in most rooms, it takes 4 subs to get the low frequencies where you would like. I suspect you will find that your room is not be an exception to that general rule. I think you would have a more cost effective and possibly better solution going with the Audiokinesis Swarm or the similar Debra than buying two more REL subs. Those things ain't cheap. If you get an AK Swarm, you won't need the existing RELs, so you might as well sell them and use the proceeds on offsetting the cost of the Swarm.
The Swarm system will go to a lower frequency than almost all of the REL subs will. I have nothing against REL subs, and use one in my living room system. But the distributed array approach is just so much better fundamentally that it is the way to go if you are looking to achieve the best results.
Again, before I spent any money, I'd send Duke my room dimensions and see what he thinks. He's seen the Swarm installed in a lot of different rooms, I'm sure. I have zero actual experience with a room like yours. |
Ronboco, no need for embarrassment! We are all learners trying to help each other enjoy the music. Eric's comments above with respect to REW are correct. REW can be used to develop equalization files, but I are not advocating that use. I'm advocating its use as a sophisticated measurement tool that allows you to understand what your speakers are doing in your room. It allows you to make highly informed choices about the tradeoffs that result from positioning decisions, absorption and diffusion decisions, and other system changes including placement of subwoofers, phasing of those subwoofers, etc.
I have nothing against digital room correction. I use a Lyngdorf 2170 in my living room, where I don't want a bunch of subs and I don't want to install conventional absorption and diffusion panels. I do not, and probably will not, use DRC in my dedicated listening room.
If you plan on using a receiver that offers DRC, then there is no harm in trying it and seeing what it does. The key word there is "see." Seeing requires measuring. Measuring requires REW. As I said, every decision you make involves tradeoffs. |
