From what I know and doing this for over 10 years, meaning adjusting my studio and working at many others. I would give you a suggestion to sit inside your triangle and not outside, If I start explaining the logistics behind it, I'm afraid I would get lost myself but a very knowledgeable person (Carl Tats) during one of the conferences in Nashville showed me some diagrams which I don't have handy. Look him up and his diagram and I believe it will answer all your questions. Good lucj

Monitors like people, have to suffer through all kinds of different living conditions. A good monitor in one room will sound like crap in a similar room. A lot of this is based upon the room and the placement of the speaker and your placement within the room. Sometimes it's hard to find a sweet spot if there is a sweet spot to be found at all. Some rooms are so awful sounding, there is no sweet spot. There is just the crap pile.

Your current monitors are passive monitors being powered from an outboard amplifier. Sometimes a simple inversion of polarity for both speakers can make an astounding difference. You can't do that with a powered monitor. Not even from inverting the phase because that's not polarity, that's phase and not necessarily between left and right channels. The two are often thought of as being the same thing. They're not the same thing. One is a voltage in version the other is a power inversion. Even though you have connected red to red and black to black does not mean it is connected correctly. That scheme goes against DC theory. You know what would happen to your flashlight if you put your batteries in that way, it would not work because that is DC. But this is AC with its own DC polarity. Invert that and your speakers may come alive. Do it to both not just one because that would throw them out of phase together. And you don't want that.

In rooms that have these types of problems where one cannot necessarily put forth structural modifications, one has to find a workaround. In this small control room, you might need your back against the wall? When you do that, you have virtually eliminated this reflective surface behind you that is canceling out much of your low frequency energy. And then the speakers sound like crap no matter where you stick them. And it doesn't matter what speakers you have. You may have to simply move, you? This is what we must do in a non-perfect environment. It won't necessarily be like all of the pretty pictures you see of the perfectly acoustically designed control rooms because you are in an apartment not a studio.

It's obvious that being in an apartment, you're not going to want to use larger speakers unless you want to get convicted. So you are basically tied to near field monitors because you're not in a studio, you're in an apartment. You don't get to turn your monitor speakers up until you're a big kid with your own apartment a.k.a. a house. So it's really a simple matter to align yourself in the room and position your speakers for proper monitoring. It won't be like the pictures nor the articles.

Those Adam's are very nice monitors. Albeit a bit pricey. Perfect to get you evicted and they still won't solve your problem.

So where is your diffusion? Where's your bass traps? Heavy theater curtains? Guess you'll need some more tweeters? Because that ain't going to do it either. Then ya wonder why your speakers don't have any high end. Though they might help on one or two walls? Certainly not all around.

So there is no ideal what your situation. There is only compromise. But that's not horrible. It merely keeps you on your toes.

Want some better acoustics? Put up some floor to ceiling bookshelves. Go down to your local library's, schools, universities and find out what books they have they are throwing out. Stock your bookshelves full with different sized books. No same sized books like Encyclopaedia Britannica's lined up evenly. You need them all to be different heights and depths so it doesn't look all neat and orderly. That will give you lots of mass and diffusion and is virtually free. And everybody will think you are so brilliant when they see all those books on your shelves. And that's called baffling them with BS. Because if you do this right, you will be that smart.

I will tell you that I've had similar problems with monitoring when I first built my Crowmobile.com truck. Stuffed some bass traps in and diffusers and it was still blah until I moved me. I use both near and Midfield monitors with the Midfield's being in the near field also. There is no far field monitoring in this control room. Not possible based on design concept. And of course space. So my control room is only 8 x 10 x 7 and not quite eight more like 7.5 wide, 10 deep and seven hi. In the other room is seven of nine I mean 6 x 8 in the combo/auxiliary control room and a rather crowded 8 x 8 in the HVAC/power supply storage and entranceway room. Which can actually accommodate a small drum set when all other crap is removed from the room. Pizza is a bad choice for lunch because then everybody starts passing gas. Great when you like those hot smelly takes.

I like to eat a lot of raw garlic cloves just to impress the people around me.
Mx. Remy Ann David

Regarding the positioning of monitors, first find the distance that sounds good, and then move them apart until you get a good even pan, without a hole in the middle. Then muck about with the angle or "toe-in", you might like them parallel with each other, you might like them strongly angled in. It depends on the room-monitor combination.

If the room sucks, you just want to sit as close as you can to the monitors.

The living room + curtain arrangement will probably help, the thicker and heavier you can get your curtain, the better it'll sound.

You might want to even out the symmetry of the room by putting an absorber panel or something with that effect to match the open doorway on the other side. These days you can get inkjet printed canvasses, and hide a chunk of owens-corning 703 behind it, so it'd look like a painting.

RemyRAD, post: 394867 wrote: You know what would happen to your flashlight if you put your batteries in that way, it would not work because that is DC.

Umm... a bit off topic, but I must point it out. If a torch is a switch and a bulb you should indeed find that a bulb cares not which way the current flows. You can also power a bulb off AC, or whatever. PWM if you want. An LED torch, now that wouldn't work with the polarity flipped, because it's a diode.

Speakers can indeed be run with the polarity flipped, and should sound similar (so long as you do both sides).

Most of the psychoacoustics tests that have been done suggest that people find it very hard to tell the difference, I certainly don't find it easy. However, the dynamics of the speaker assembly *do* change with polarity, speakers are rarely symmetrical dipoles, so it's worth a try. Rather than rewiring your system, you can try it using a simple polarity flipping plugin, and see what happens.

___

Certainly making the back wall less like a flat sound-mirror will help things to sound good. Sheet music, books, 12" records, wall-hangings, old speaker boxes, old drum machines, collections of animal skulls... fiberglass absorber panels, diffusers of various designs, they all have the same class of beneficial effect – cutting down the incidence of specular reflections (but in various different ways, and with various different provisos and levels of predictability). [[url=http://[/URL]="http://en.wikipedia…"]Specular reflection - Wikipedia, the free encyclopedia[/]="http://en.wikipedia…"]Specular reflection - Wikipedia, the free encyclopedia[/], which cause all sorts of undesirable strong interference patterns. Irregular shapes and / or porous materials.

redbort, post: 394716 wrote: putting speakers against a wall creates a bass boost. :confused:

Yes, it's quite simple if you think about it the right way.

When you have a reflection, within a certain distance (related to the wavelength of the wave in question) the reflected wave will be constructively interfere with the incident wave. If you place a microphone right at a boundary, there is no distance, and no time delay between the incident wave and reflected wave, that's how a pressure-zone, PZM or boundary microphone works. You can use a normal omni mic as a pressure-zone mic by sticking it against a wall, or on the floor. At a perfectly reflective boundary, you will get a doubling in volume. 6dBs of boost at a boundary (in theory if it's perfectly reflective).

At a boundary, the incident and reflected wave are the same at that point, and it is that pressure zone which is actually inducing the hard boundary to re-emit the wave.

So, if you place the entire speaker inside the wall, it'll get louder across all the frequencies. This is called soffit mounting.

How big that pressure zone is which will create the reflection, that'll depend upon the frequency. The best place to absorb sound energy related to reflections is in these pressure zones.

Low bass frequencies can often get so big that you'll get a pressure zone that's bigger than the room, and reflections of reflections of reflections come into play. This is an effect called cabin gain.

If you have a speaker placed a distance away from a boundary, there may be a slight delay between the incident wave and the reflected wave, but the chances are that if the wavelength is long, and the distance is relatively short, there won't be a big phase difference, maybe a few degrees, so you will still get mostly constructive interference, therefore quite a bit of boost in the level. This is complicated by the issue that most speakers have anything but an even dispersion of sound across all frequencies.

The underlying issue is a non-compliant flat surface. Reflections.

The BBC's been doing this for awhile, and helped establish some decent rules of thumb as well as define standards recognized and accepted the world over. Wes LaChot kinda' refined the process a bit and today, this is getting to be a pretty well established guideline to start you monitor position search/placement.

The process can done however you want, however, doing things in a respectably scientific manner will yield far better results than taking things on in a half-assed, stab in the dark manner.

Locate your "ideal" listening position by marking the floor at 38% of the distance from the "front wall" and centered from left to right. 38% is a point that mathematically yields the least number of harmonic issues.

Locate and mark the monitor positions, by creating an EQUILATERAL triangle whose angle to each speaker is 30 degrees from a center line of the room.

Your listening position typically ends up being just inside that triangle, with the speakers pointing just behind your ears.

Use REW (Room EQ Wizard) to test your room/monitor response curves.

Your room is really going to be difficult to get balanced, as your environment is close to the worst possible environment you could have... a cube.

You will definitely benefit from broadband trapping in the wall::wall corners, and from ceiling::wall corners, using something like the Studiotips Super Chunk corner traps.

Additionally, I would expect you to also need to treat the first reflection points and to implement some SBIR panels behind the monitors.

I would NOT recommend soffit mounting. It's almost impossible to get right in a well designed, purpose built room, much less a room as difficult to deal with as a cube.

If you really want to go about this the right way, and get really good, professional assistance... I'd encourage you to head down to the Studio Build forum, read Rod's sticky, and then post a thread outlining your situation.

Also, check out a couple of books... Rod Gervais' "Build It Like The Pros", Alton Everest's "Master Handbook of Acoustics", Philip Newell's "Recording Studio Design". (Although you probably won't benefit as much from Newell's book unless you're actually building a studio - it's still a GREAT resource.)

MadMax, post: 397294 wrote: Locate your "ideal" listening position by marking the floor at 38% of the distance from the "front wall" and centered from left to right. 38% is a point that mathematically yields the least number of harmonic issues

38% of what distance? From one wall to t'other? From the curtain to the back wall? Or from... oh.

Put a corner trap in front of... wait... is that a doorway? Looks to me like the "room" of "cube" shape actually only has one corner, is stuck onto another enclosure, and has quite a lot of holes in it (two open doorways).

Erm...

Is the topic how to position nearfields? The answer to which is a suggestion that the guy install a lot of square meters of acoustic panels?

Certainly there are a more than a few good books on acoustics, which anybody who deals with sound will find contain useful information.

bishopdante, post: 397253 wrote: Yes, it's quite simple if you think about it the right way.

I guess it's simple to explain if you don't know what you're talking about.......... everything is simple then.

When you have a reflection, within a certain distance (related to the wavelength of the wave in question) the reflected wave will be constructively interfere with the incident wave. If you place a microphone right at a boundary, there is no distance, and no time delay between the incident wave and reflected wave, that's how a pressure-zone, PZM or boundary microphone works. You can use a normal omni mic as a pressure-zone mic by sticking it against a wall, or on the floor. At a perfectly reflective boundary, you will get a doubling in volume. 6dBs of boost at a boundary (in theory if it's perfectly reflective).

If you have a speaker placed a distance away from a boundary, there may be a slight delay between the incident wave and the reflected wave, but the chances are that if the wavelength is long, and the distance is relatively short, there won't be a big phase difference, maybe a few degrees, so you will still get mostly constructive interference, therefore quite a bit of boost in the level. This is complicated by the issue that most speakers have anything but an even dispersion of sound across all frequencies.

You only get a boost from a signal if the reflected signal is in sync with the original signal........

When it comes to reflections from near surfaces the issue is destructive in nature - not constructive. With low frequencies you are never going to have a case where you have a fully developed waveform when striking a nearby surface - in these cases the problem is generally 1/4 wavelength in nature - which will cause a dip at the listening position.

To the OP - if you're having low frequency issues with near boundaries coupled with the original signal from the speaker the solution is one of 2 possibilities... the first is to move the speaker further from the offending surface, this if you have a large enough room - the 2nd is to move the speaker closer to the offending surface.

The underlying issue is a non-compliant flat surface. Reflections.

Actually the underlying issue here is a person posting advice who doesn't really understand the fundamental principles involved in acoustics.

Rod

Rod Gervais, post: 397313 wrote: I guess it's simple to explain if you don't know what you're talking about.......... everything is simple then.

I was simply outlining the phenomenon of bass boosts due to proximity effect, which the OP had been told was a phenomenon (it is) and was unsure as to what causes it. Do you have a problem with that explanation? A few degrees of phase shift is mostly constructive, closer to 180º is mostly destructive. What's the deal here? A negigible phase shift of a few degrees doesn't cancel. It doesn't. You should be more rational.

But sure, I'd consider it a valid addition that at a given emitter to receiver with multiple paths and boundaries, you won't just get boosts due to interference, you'll also get cancellations, and this will depend upon wavelength. The subject I was tackling was, however, 'what causes elevated levels of bass frequencies if you put speakers next to walls'.

Why do you feel the need to disagree with me, when you know what I'm writing is basically correct? Basic, not a completely exhaustive run-down of every possible room dynamic, I'm not writing a book here, and not that you can achieve a completely exhaustive analysis without truly brutal levels of computer simulation, but it's hardly incorrect. I'm not interested in a politicised viewpoint. Why the chip on the shoulder?

What Mad Max is advocating here is a different topic. He's suggesting that he convert his room into a treated control room, rather than move his monitors about. I think that's an implausible suggestion, especially considering the floor plan.

RemyRAD, post: 394867 wrote: So there is no ideal what your situation. There is only compromise. But that's not horrible. It merely keeps you on your toes.

Pretty much what I was looking at.

bishopdante, post: 397330 wrote: I was simply outlining the phenomenon of bass boosts due to proximity effect, which the OP had been told was a phenomenon (it is) and was unsure as to what causes it. Do you have a problem with that explanation? A few degrees of phase shift is mostly constructive, closer to 180º is mostly destructive. What's the deal here? A negigible phase shift of a few degrees doesn't cancel. It doesn't. You should be more rational.

Sure i have a problem with that - Proximity effect (which is a microphone issue) has nothing whatsoever to do with the relationship of a speaker to a border.

The OP was speaking of creating a boost in low frequency transmission as speakers are mover closer to a wall - and this is clearly not the case - there is not a boost in bass - there is a decrease in LF destructive forces due to near boundaries - which is a different thing altogether. Putting speakers against a wall has the effect of providing a more realistic representation of the speaker as a whole. The closer to the wall the higher in frequency any interference will be. High frequency dips are easily solved through the use of localized room treatments placed behind the speakers.

Not what you presented at all.....

But sure, I'd consider it a valid addition that at a given emitter to receiver with multiple paths and boundaries, you won't just get boosts due to interference, you'll also get cancellations, and this will depend upon wavelength. The subject I was tackling was, however, 'what causes elevated levels of bass frequencies if you put speakers next to walls'.

well that happens to be my issue with your post - this is not what actually happens. This is (in small rooms) a solution to a problem - it is not a cause of the problem.

Why do you feel the need to disagree with me, when you know what I'm writing is basically correct? Basic, not a completely exhaustive run-down of every possible room dynamic, I'm not writing a book here, and not that you can achieve a completely exhaustive analysis without truly brutal levels of computer simulation, but it's hardly incorrect. I'm not interested in a politicised viewpoint. Why the chip on the shoulder?

Basically correct is also basically wrong - some truths in a post are not the same as an accurate representation of what's going to help the OP.

Throwing in 1/2 truths - along with some bull that has nothing to do with the subject matter (such as proximity effect on microphones) is not helping the OP get his room straightened out.

What Mad Max is advocating here is a different topic. He's suggesting that he convert his room into a treated control room, rather than move his monitors about.

Yeah - I know - Max is a bad guy for suggesting a methodical approach - you much prefer the "muck around" approach.

LOL - what is my "politicized viewpoint"? I have no chip on my shoulder - just a great desire that the people coming here seeking help actually get accurate information.

I have none of that to offer in most regards at a site like this - I am not an expert in recording engineering - or mastering - or even the gear that goes into the rooms I design...... thus I don't make posts trying to guide people in those things - if they ask questions I point them in the direction of someone who might actually have a real answer for them - however when they ask about something I actually know something about - i tend to see to it they get real answers to those question - not 1/2 truths - not answers lacking detail - but something that might really lead them to having a room they can work in - or bring them to the realization that it is not possible to accomplish what they think they really want - whichever is the truth.

Rod

Proximity effects and boundary effects are indeed very closely related. Proximity being an interaction with
a reflective boundary or multiple sources/paths, resulting in shelving below a given cutoff frequency! A speaker is a transducer, as well as a microphone, and they have various non-omnidirectional dispersions, but become (typically – the exception being dipoles ie figure of 8 speakers) more and more omnidirectional at lower frequencies, and if you reflect that omnidirectional output very close to the center of that circle with a periodic wave, you will double its volume, the longer the wave, the more central the reflection. It's similar in effect to cabin gain, sub-modal. That is the sense in which I'm using the term proximity effect. In the case of a transducer where the treble is directional and the bass is omnidirectional.

bishopdante, post: 397342 wrote: It has everything to do with the matter. Mics and speakers are transducers, and the principal applies both ways!

Sorry - no it does not - the closer a mic gets to a sound source the greater the effect of that source on the microphone - here the speaker is the source - it cannot possibly get any closer to the source than it already is..

I will say this again - this time I will say it slower, perhaps then your mind will have a chance to grasp it....

Let's say a speaker is sitting 2.21' from a wall - that's a 1/4 wavelength of 110Hz and will cause a dip at that frequency. not a peak - a dip - now - if I push that speaker so it is only 10" away from that same wall - the dip will raise in frequency to (roughly) 281 Hz - a much higher frequency - and much easier for me to handle with local treatment.

It is exactly the opposite of what happens with a microphone....

Perhaps you should study the phenomena known as SBIR as relates to near surfaces.

Seriously - you really should stick with discussing things you're expert in - acoustics as relates to rooms is not your strong point.

Rod

That's comb filtering, not proximity (or boundary). Combing occurs where there's a significant phase-difference. I'm sure you'd agree that at 1mm distance between two sources, it doesn't matter whether I use 20Hz or 1Hz, we will have almost completely constructive phase.

The comb filter is what acoustic-labyrinth cardioid mics employ in order to produce a pattern, *harnessing* the cancellation with an array of interferences to produce (hopefully) even cancellation across as many frequencies as possible, but in truth it's a bit spikey.

When you reach the soffit-mount, a distance of nothing, with no distance from incident to reflected (or various sorts of horn etc) then you'll eliminate the various issues of both combing and proximity and you get reinforcement (subject to complicated arguments about speaker diaphragms).

bishopdante, post: 397345 wrote: That's comb filtering, not proximity. Combing occurs where there's a significant phase-difference. I'm sure you'd agree that at 1mm distance between two sources, it doesn't matter whether I use 20Hz or 1Hz, we will have almost completely constructive phase.

I am quite sure I would not agree with that -

When you reach the soffit-mount, a distance of nothing, with no distance from incident to reflected (or various sorts of horn etc) then you'll eliminate the various issues of both combing and proximity and you get a doubling of all frequencies.

What the hell do soffit mounted speakers (which you have raised on a few occasions here) have to do with the post the OP made? Or do you simply like to confuse the issues?

We are not discussing soffit mounted speakers (which Max rightfully pointed out one should not even consider unless one really knows what they hell they are doing) - the OP is not considering this - this has nadda to do with how a non soffit mounted speaker will react within a room - it's simply some more bull you throw into the midst of the conversation that makes it more difficult to follow your line of reasoning.

Why not discuss the acoustical properties of speakers inside of automobiles while you're at it....... that would really cover all of the bases....

To the OP - we have a really good forum here at RO specifically for the purpose of discussions like this where we address what does and does not happen in rooms, and how to get the most out of your room when all is said and done - it's the [[url=http://[/URL]="http://recording.or…"]Studio Construction & Acoustics Forum[/]="http://recording.or…"]Studio Construction & Acoustics Forum[/] feel free to join us there if you want some real answers to your questions.

Rod

Rod Gervais, post: 397346 wrote: I am quite sure I would not agree with that

So I can get destructive interference?

An emitter near the boundary at a low frequency becomes omnidirectional, working in half space it is subject to the boundary effect. You can get the boundary effect at a distance if the wavelength is long. Cabin gain is where *all* the boundaries reinforce, all the reflections are (increasingly) in phase, delay has a negligible time...

Rod Gervais, post: 397346 wrote: We are not discussing soffit mounted speakers

Soffit mounted speakers being an example of avoiding interference with the boundary they are mounted in. Zero distance from the boundary.

Also a prime example of the employment of boundary effect and cabin gain to produce a hell of a lot more bass. If you take a set of Quested soffit mounts, and you put them on stands outdoors, you will have *no* bass at all.

Anyway, this is getting off topic, I'm off to do something productive. I've reached my diffraction limit. Sorry... distraction limit.

bishopdante, post: 397350 wrote: So I can get destructive interference?

What the hell do you think a dip or null is?

Also a prime example of the employment of boundary effect and cabin gain to produce a hell of a lot more bass.

And you will also have - inside of that very same room - a whole slew of areas where there will be dips with a hell of a lot less bass....... I still haven't figured out if your talking just to hear sound come out - or if you're actually trying to learn anything here....

One thing is for sure - there is nothing at all constructive that comes out of having this discussion with you.......

Rod

Rod Gervais, post: 397353 wrote: What the hell do you think a dip or null is?

*sigh* but there's a lower limit on the effect of the comb filter! Below that threshold as the wavelength considerably exceeds the difference in path length, the interference is *only* constructive, because the phase difference becomes increasingly negligible, producing *only* reinforcement, ie boosted levels of bass, not a notchy response.

As the wavelength gets longer than the size of the room, the more boundaries that come into play, and the greater the boost levels. Have you not read about or experienced this?

Every live sound engineer knows that in some venues, your mixing desk is right up against a back concrete wall, or worse still a corner, or even worse some sort of container shape. The problem with being near a boundary is that you experience a huge lump in the bass response. You have to walk out & check the real level that everybody else hears. Or, if you're clever, you stick your head right up against that wall, and soffit mount / PZM yourself – boundary effect rather than proximity effect.

At this point yes, I am beating my head against a wall.

I love these passionate debates. It's technical accuracy versus personal perception. Bottom line, if you can deliver good product, whether one spends money on acoustic engineered plans or plain dumb luck, none of this matters. Not everything in life is a mathematical equation. Even though it is. Some of this has to be based on gut belief. And if you can deliver? And obviously, both of you guys can deliver and do deliver.

I mean I love my well-educated comrades in audio. I love it when they do everything right and it sounds all wrong. So that's when they don't call the experts and instead, call me. Then I do everything wrong to make it right. So there's a wrong way to go about doing everything right and the right way to go about doing everything wrong.

You guys, along with myself and others here, are top level professionals. Professionals whose personal professional experiences makes them so much better than the average schmuck. I mean didn't Einstein have a problem with Max Planck? One of those guys? Who is right? Does it really matter? They both figured out how to blow up the world. So they just know how to blow it up differently from each other. Either way, end results will all likely be the same? As it should be with any competent professional.

So you're both right.
Mother Audio Bitch

A.k.a. you know who.

Yeah - huge sigh here as well........

Sorry - play stepped sine waves in 30 second increments - walk around the room while listening - and what you will find is a whole series of huge peaks and dips. With drastic changes between the 2 just inches from one another. That is the effect of constructive/destructive interference.

I do not consider 30dB dips to be "insignificant" - and I've found those in untreated rooms in the best of positions (have also found them in so called "treated rooms" that were designed by recording and mastering engineers who simply don't have a clue as well.)

Again, you simply haven't a clue....... duh

You're an engineer making believe to be an acoustic engineer - I am an acoustic engineer who doesn't pretend to be anything I'm not... Lucky for my clients I actually understand enough about this to be able to design rooms for them on paper that translate into stellar rooms when built exactly as designed - and don't have to "muck around" to make things work.

Rod

Wow, congrats, that's one doozy of an argument you guys have going there.

To the OP: Check out this site: [[url=http://[/URL]="http://www.atsacous…"]Acoustic Panels FAQs[/]="http://www.atsacous…"]Acoustic Panels FAQs[/]

I've bought panels from them and the product is awesome and affordable (no I don't work for them). It's an amazing difference when you've put some treatment up in your mixing room and IMO it's the only place to start when you're asking questions like yours. This article is a great article to read.

Start by treating your room, it has inherent problems that have to be resolved before anything else you do will make a difference. More than likely when you're done treating your room, you'll know exactly what to do next (if you need to do anything else).

Rod Gervais, post: 397366 wrote: You're an engineer making believe to be an acoustic engineer - I am an acoustic engineer who doesn't pretend to be anything I'm not... Lucky for my clients I actually understand enough about this to be able to design rooms for them on paper that translate into stellar rooms when built exactly as designed - and don't have to "muck around" to make things work.

Leave it with the ad hominem stuff, the truth should be the same for everybody! You seem to be concerned with profile rather than subject matter, which is something of a dangerous logical fallacy. The idea that a sound engineer putting out microphones in a live room or setting up line arrays won't know plenty about acoustics shouldn't be your assumption. In actual fact, it seems that assuming and declaring that other people don't know enough / are automatically wrong is a bit of a theme.

I'd certainly agree that the comb filter is an acoustic issue caused by reflective surfaces... just like diffuse reverb is, or audible slapback delays, and that one could have issues with walls absorbing certain frequencies and not others, or whatever else may be going on in a room. We could get into psychoacoustics and how the ear uses a variety of different cues to localise and/or perceive sounds, and what frequency thresholds these are viable cues at. To the ear comb filters are not nearly such a problem as when you use a microphone or measurement device. A room can sound fine in person, but to a microphone suddenly it's notchy as hell. Lots of people find this seeming discrepancy between their senses and a measurement device surprising. This is partly the imperfect nature of cardioid microphones interacting with notchiness caused by multiple reflections, but it's also due to the psychoacoustic digestion of comb filters as being recognised a meta-phenomenon of a sound source, the ear is able to digest and distinguish the information and compensate for it. That may cause the listener to hear the position of the speaker, rather than the position of the sound within the mix, eliminating early reflections will help the localisation effects which occur at higher frequencies, but it doesn't influence their perception of frequency response nearly as much. Just the same as a non-white colour in a light source doesn't influence a person's perception of colour (unless the source illumination is really aberrant), whereas a camera will require serious white-balancing. The behaviour of measurement instruments and human perception should not be assumed to be equivalent.

But that debate will not be relevant to the issue of... "why do speaker boxes produce more bass when placed in close proximity to walls", which is a commonly observed effect that any speaker designer worth their salt will be able to tell you about in less than half a paragraph.

Discussing comb filters, room modes, slapback, high frequency ring, localisation, diffuse reverberation... it is not tackling the question of "why do speakers produce more bass when they are placed very close to walls", which is an effect caused by the omnidirectional output of a speaker box at low frequencies – where the box size is substantially below the diffraction limit – producing phase-coherent reflections at negligible distances from the boundary. The same principal applies to a coherant array or a horn. You don't have multiple interfering waves with drastically differing paths, you have *one* conglomerate wave, albeit with a modified dispersion pattern. In the case of the 1mm distance of a transducer from a boundary emitting test tones of 20Hz and 1Hz, there won't be any lobes, nothing. To all intents and purposes it can be considered a pure boundary effect, a single omni source in half-space. If you decrease the distance from reflective boundary to source, you'll push up the comb filter – and also the boundary proximity effect, until you've pushed the comb filter right out into the ultrasonic frequencies and when you reach the ultimate extent of zero distance – boundary microphone or soffit mount – you are putting the sound transducer inside the boundary, and there is no path difference.

In the case of a normal residential room, I'd expect that one could get some nearfields or floor standers to sound pretty reliable without having to install the type of equipment that MadMax is talking about. I have no specific acoustic treatment in my living room! It's a living room! One can get things pretty good by moving stuff about. I have several hat stands in corners with lots of coats, a bunch of book cases, open-faced storage with clothes, and some strategically placed soft furnishings (chairs, sofas, cushions, curtains etc). It doesn't sound like a mastering-grade control room, but it sounds absolutely fine.

Nothing intrinsically wrong with putting up panels, though.

On the subject of improving the treble and localisation, doing stuff to the back wall and the early-reflection points might be advisable. That isn't the subject of moving monitors around, though.

My point about bass and close proximity to walls isn't a totally exaustive run-down of all of the possible reflection effects that you can get in a room, across all frequencies. No. It's one specific class of effect.

___

Note from the link you provided yorkville.com/products.asp?cat=35&type=71&id=118 that you have switches which will EQ the speakers to be better suited to different boundary conditions, 1/4 space, 1/2 space and full space, and a + or - 2dB EQ, so you can set the speakers to perform according to their proximity-to-boundary conditions. However, a 2dB EQ does assume that a wall isn't highly reflective to bass, domestic walls aren't necessarily equally reflective to all frequencies. I usually find that setting those things flat is best for near-field use.

Environmental Processor w/ Four Dip Switches
HF Reflection Optimization +/-2dB boost/cut 10-20KHz
LF Efficiency Factor +/- 2dB boost/cut 20-80Hz
Full Space, 1/2 Space, 1/4 Space

Hey, guys, I just bought a dozen of those Genelec AcoustiTapes to send out for Christmas! Guess who's getting the very first one?:wink:

Me?

:)

Try again!

"There's nothing like the adrenalin rush you get when you see an SM58 slicing through the air at 108mph straight for your head..." Pete Townsend on being onstage with Roger Daltrey