nearfield theory - revisited

[not Cereal]

i've had a pair of monitor ones for a few years now, grown to love 'em like some folks like ns10's. i actually use the monitor ones over the hr824's almost all the time and i have gotten used to how they are "supposed" to sound when trying to homogenize a tune into what other cd's are sounding like. AND one thing i have always noticed was that they had a clear bass sound, but at a low level. real easy to get used to the bass. but today i noticed something [i]really weird[/i] .... i turned up a playlist through the nearfields so i could hear it outside the room. i noticed that when i walked back up to adjust it later i got this HUGE amount of bass about 15 feet away from the speakers! i dont get it. THAT SOUNDED COOL, almost like BIG farfields but it would take time getting used to. i dont get it. the speakers are about 4' from the walls, 4' from each other, and 3' or 4' from me. ive never noticed that before... :confused:

[Jeebus]

[quote]Originally posted by TheCoasterBergerTown: [QB]when i walked back up to adjust it later i got this HUGE amount of bass about 15 feet away from the speakers! i dont get it.QB][/quote]The wavelength increases as pitch decreases, therefore bass & subbass have very long wavelengths. This means that such sounds are not always audible, until you get far enough away from the sound source. In all likelyhood it is possible that you have discovered a standing wave in your room. This is also part of the reason the "bass player is playing too loud". I hope The Jesus was of some help to you, The Jesus

[Dwarf]

[quote]Originally posted by The Jesus: [b]The wavelength increases as pitch decreases, therefore bass & subbass have very long wavelengths.[/b][/quote]So far you're right on. [quote][b]This means that such sounds are not always audible, until you get far enough away from the sound source.[/b][/quote]Nope, 100% wrong. If this were true you wouldn't hear any real bass until you were 50-100 feet from the source. Your walkman would only give you 10KHz and above. [quote][b] This is also part of the reason the "bass player is playing too loud".[/b][/quote]In my experience, it's usually because the bass is playing too loud. Guitarists are worse. -- Rob

[Jeebus]

[quote]Originally posted by Dwarf: [b] [quote][b]This means that such sounds are not always audible, until you get far enough away from the sound source.[/b][/quote]Nope, 100% wrong. If this were true you wouldn't hear any real bass until you were 50-100 feet from the source. Your walkman would only give you 10KHz and above. Rob[/b][/quote]This is not wrong it is right. Perhaps my wording was poor. I shouldn't have said "audible", but "MORE audible" as you get further.

[Dwarf]

[quote]Originally posted by The Jesus: [b]This is not wrong it is right. Perhaps my wording was poor. I shouldn't have said "audible", but "MORE audible" as you get further.[/b][/quote]So, the bass gets louder the further away you are? I think I'll leave this discussion now before it gets any sillier. -- Rob

[Jeebus]

[quote]Originally posted by Dwarf: [b]I think I'll leave this discussion now before it gets any sillier. [/b][/quote]I think that would be wise, and beneficial to us all.

[henrysb3]

I'd say it has something to do with your room. Maybe with the speaker placement and room dimensions, you have created a kind of Klipshorn, although Klipsh speakers were intended for corner installation. I have a pair of full range 8" JBL's that appear to have different EQ as I move about my basement. Some time ago, there was in interesting discussion here about the placement of subs and how they could actually phase-cancel some frequencies if improperly positioned. Bass also tends to travel thru objects, while highs stop. This is why I guess you can hear thumper cars thump while being spared some of the vocals.

[Dogfur]

Congratulations on the discovery of standing waves between you and your speakers. My current office sucks large in this area also. Construct bass traps and treat parallel walls to start down the road to low frequency redemption... I may be full of shit here, I'm no acoustician.

[Kendrix]

The standing wave is exactly the reason you want to stay near to the nearfields. Theory confirmed!

[Hippie]

It strikes me as odd when they say the 'sweet spot' is the triangulation area between the monitors. I swear I can do a better mix standing under the door threshold that exits my studio. For sure, the sweet spot is a good place to start, but I think you need to move out of that zone to get more understanding of the mix.

[Kendrix]

[quote]Originally posted by Hippie: [b]It strikes me as odd when they say the 'sweet spot' is the triangulation area between the monitors. I swear I can do a better mix standing under the door threshold that exits my studio. For sure, the sweet spot is a good place to start, but I think you need to move out of that zone to get more understanding of the mix.[/b][/quote]Hippie, The problemn with your suggetion is that the sound outside of the sweet spot is highly dependant on the room geometry and reflection characteristics. In rare instances this Might work great but - more likely, it will really throw you off.

[BlueSky]

[quote]Originally posted by Kendrix: [b]The standing wave is exactly the reason you want to stay near to the nearfields. Theory confirmed![/b][/quote]Actually this statement only holds true at Higher Frequencies - Discrete HF reflections are a dominant factor in small rooms with low reverberation times (lets say a 3K cubic feet studio). They are most often audible as comb filters (uneven HF response) and give a distant and “smeary” character to the sound. Sound reflections can occur from side wall, rear walls, furniture, video monitors, mixing consoles, or any other large surface within the path of the speakers’ radiation. Below 100Hz, rooms smaller than 12,000 cubic feet become dominated by room modes. Room modes, also known as standing waves, occur in all rooms at frequencies where the wavelength of sound is an integer fraction (i.e. 1/1, 1/2,1/3,1/4, etc.) of the distance between two walls, or the distance between the ceiling and floor (this is a slightly over simplified explanation). This means that invariably, some frequencies are reinforced and some frequencies are canceled, resulting in peaks and dips in the frequency response at the listening position. These peaks and dips are affected by the relative position of the speakers and listener to the boundaries in the room. Hope that helps...

[Kendrix]

[quote]Originally posted by BlueSky: [b] [quote]Originally posted by Kendrix: [b]The standing wave is exactly the reason you want to stay near to the nearfields. Theory confirmed![/b][/quote]Actually this statement only holds true at Higher Frequencies - Discrete HF reflections are a dominant factor in small rooms with low reverberation times (lets say a 3K cubic feet studio). They are most often audible as comb filters (uneven HF response) and give a distant and “smeary” character to the sound. Sound reflections can occur from side wall, rear walls, furniture, video monitors, mixing consoles, or any other large surface within the path of the speakers' radiation. Below 100Hz, rooms smaller than 12,000 cubic feet become dominated by room modes. Room modes, also known as standing waves, occur in all rooms at frequencies where the wavelength of sound is an integer fraction (i.e. 1/1, 1/2,1/3,1/4, etc.) of the distance between two walls, or the distance between the ceiling and floor (this is a slightly over simplified explanation). This means that invariably, some frequencies are reinforced and some frequencies are canceled, resulting in peaks and dips in the frequency response at the listening position. These peaks and dips are affected by the relative position of the speakers and listener to the boundaries in the room. Hope that helps...[/b][/quote]

[Kendrix]

[quote]Originally posted by BlueSky: [b] [quote]Originally posted by Kendrix: [b]The standing wave is exactly the reason you want to stay near to the nearfields. Theory confirmed![/b][/quote]Actually this statement only holds true at Higher Frequencies - Discrete HF reflections are a dominant factor in small rooms with low reverberation times (lets say a 3K cubic feet studio). They are most often audible as comb filters (uneven HF response) and give a distant and “smeary” character to the sound. Sound reflections can occur from side wall, rear walls, furniture, video monitors, mixing consoles, or any other large surface within the path of the speakers' radiation. Below 100Hz, rooms smaller than 12,000 cubic feet become dominated by room modes. Room modes, also known as standing waves, occur in all rooms at frequencies where the wavelength of sound is an integer fraction (i.e. 1/1, 1/2,1/3,1/4, etc.) of the distance between two walls, or the distance between the ceiling and floor (this is a slightly over simplified explanation). This means that invariably, some frequencies are reinforced and some frequencies are canceled, resulting in peaks and dips in the frequency response at the listening position. These peaks and dips are affected by the relative position of the speakers and listener to the boundaries in the room. Hope that helps...[/b][/quote]oops ignore prior (blank) post - musta hit a wrong button. I accept your point - to a degree. Its true that, at low frequencies, room modes dominate and the sound is not directional. However, isnt it also true that, if you are just a couple of feet from the monitors ( whose position defines one of the boundaries of the sound waves) you are very unlikely to be sitting in a peak or trough of a low freq standing wave? Given the wavelength involved isnt this true? You'd only be a small fraction of a wavelength from the source and this should minimize the magnituide of any interference. Have I got that wrong??

[Ethan Winer]

Folks, Here's the real truth: All rooms have standing waves that cause peaks and dips in the low frequency response unless bass traps are installed. The same thing happens at higher frequencies too, but: 1) High frequency standing waves are less of a problem because the wavelengths are short so that if you turn your head half an inch the range of frequencies affected changes. So with normal movement you don't notice them nearly as much. 2) You can solve high frequency standing wave problems with diffusers, though to fix low frequencies requires a diffuser that is eight or more feet deep. Yes, room modes can help to predict where the peaks and dips will be worst, but the response anamolies are always present. It doesn't matter if you use near field speakers or large speakers. Unless the room is properly treated, every location in the room will have a different bass response. A big dip around 80-160 Hz. is common at the mix position, right in front of the speakers. A big boost in the lower range is also very common in the back of the room. This is caused entirely by standing waves. There is no such thing as "low frequencies are more audible when you get farther away" due to any reason except the effects of standing waves within a room. For a more complete explanation of these issues - and maybe a little sales pitch :) - go to my RealTraps web site: [url=http://www.realtraps.com]www.realtraps.com[/url] --Ethan

[Kendrix]

Ethan and Blue sky, Thanks for the responses. Blue, Id love to read the first article you posted. However, for some reason word opens it up and show gibberish - oh well. Im still confused about one point. Doesnt the speaker define a null point in the wave- its a boundary condition. Thats why the position of the speaker vs the wall is important in defining the wave interference. So why is it you state that its only the room geometry that matters?

[EWF]

Originally posted by The Jesus: [quote]The wavelength increases as pitch decreases, therefore bass & subbass have very long wavelengths. This means that such sounds are not always audible, until you get far enough away from the sound source.[/quote]This is incorrect. Dwarf is 100% right. Sound waves do not need time or room to develop as so many people (especially so-called car audio enthusiasts) believe. The misconception results from the graphical way in which waveforms are usually represented. They are almost always drawn up as transverse waves where the displacement of the wave is up-and-down. They are only illustrated this way to make it easier for us to see what the properties of the wave are. Sound waves however are not transverse waves - they are air pressure waves which are longitudinal in nature - the oscillation is back and forth and not up-and-down. "Wavelength", when it comes to sound, is merely the amount of time it takes for the next peak in air pressure to arrive. That's why you can hear deep bass with headphones. It would also be useful to understand that "peaks" and "troughs" in sound waves are not the "hills and valleys" that are often depicted in books. Once again, they are drawn up this way for illustrative purposes. A "peak" is actually an air pressure peak, and a "trough" is where there is a lack of air pressure. If you understand it this way, you can see how you're not sitting at a "peak", "valley", or "quarter wave" per se. You're actually sitting in a place of varying air pressure, so a standing wave is where the air pressure peaks and dips are not moving. As you walk around a room, you'll hear increasing and decreasing bass. This corresponds with how much air pressure at that frequency is present at a given place in the room.

[Wow]

bump

[not Cereal]

wow. lot of info here. see this is what these forums are for, not for wanking like billbo bowel finster or whowhatever. i moved my speakers last night, see new thread. i'm thinking of hooking up my old-old-old farfields. they suck and i keep blowing the tweeters out which is why they are not hooked up.

[BlueSky]

[quote]Originally posted by Kendrix: [b]Ethan and Blue sky, Thanks for the responses. Blue, Id love to read the first article you posted. However, for some reason word opens it up and show gibberish - oh well. Im still confused about one point. Doesnt the speaker define a null point in the wave- its a boundary condition. Thats why the position of the speaker vs the wall is important in defining the wave interference. So why is it you state that its only the room geometry that matters?[/b][/quote]First, the document you are trying to download is a .pdf Adobe acrobat document. [url=http://www.adobe.com]www.adobe.com[/url] has a free reader so you can open this document. With regard to speaker position. Picture the air molecules in a room acting like a fluid such as water. So if you imagine a rectangular container filled with water and then dropping a rock into X area, depending on where it drops will determine where ripples in the water will meet and form peaks, or where they will cancel out and form a null. These peaks and nulls are determined by the relationship of the walls of the container to the rocks impact point into the water. Certain shapes, such as a square box will have lots of dramatic peaks and dips, while changing some of the ratios helps reduce some of the affects. It is important to note, that angling the walls or tilting them doesn't eliminate these problems, it just makes the affects very difficult to predict. ...