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Old 27th September 2008, 06:53 PM   #1
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Default Setting up the Nathan 10

So now that we've built the satellites (http://www.gedlee.com/Summa.htm) and subs (http://www.mehlau.net/audio/sub_peerless_sls-10/) that form the basis of a modern subwoofer/satellite concept the question is how to place them?

But first I would like to summarize the "why" and "how" of such a concept. If you need references to literature please let me know. A very good start is to read "Loudspeakers and Rooms for Sound Reproduction - A scientific Review" from Floyd E. Toole (JAES, Vol. 54, No. 6).

Reflections
The sound field in a small room like a domestic living room is not as diffuse as e.g. in a concert hall. It consists of several highly directional strong early reflections and a dimished late reflected sound field. These reflections have effects on localization of phantom sources, coloration, spaciousness and intelligibility. There's much literature on how reflections affect acoustic perception in a concert hall but there're virtually no studies on small room acoustics. So think twice before taking the various assumptions flying around as proven facts.
In most domestic rooms reflections are too loud - you hear your room and not the recording. This can be addressed with porous absorption at walls (at least 4" mineral wool mounted with a 4" air gap from wall) or with directional speakers. Furthermore these reflections arrive too early at the listeners position. Diffraction at enclosures or reflections from nearby furniture or walls arriving within 1 ms after the direct sound distract the perception of phantom images.
Furthermore the off-axis frequency response of a speaker can lead to coloration of sound perception if it's not flat.

Room modes
Every room has a unique pattern of modes. A mode results from two or more standing waves interfering with each other. Below about 100 Hz this leads to a "booming" or "one-note-bass" sound. Modes can be addressed with passive absorption which can become pretty expensive; or it's just not applicable at all because it consumes a lot of space that's normally needed by other persons living in your household. But there's also active absorption. A second modal field is actively generated and is overlaying the rooms modal field. This will not fix the bass in the whole room but it can fix the bass over a range of listening positions.

Resulting concept
As absorption is not a real alternative in a living room I've chosen to use directional speakers. When looking at the available concepts the best trade-off is to use a two way speaker with a horn and a large woofer. Only a horn can provide low distortion and constant directivity at the same time. The woofer has to be big to become as directional as possible. The Nathan's 10" woofer isn't the optimum – a 15" woofer like in the JBL 4430 is preferable.
The whole system is completed by 3 subwoofers that deliver the active absorption and low frequencies. The subwoofer signal is generated using a Behringer DCX2496. Every sub signal can be freely configured (gain, delay, HP, LP and EQ).

This is what my living room and the speaker setup looks like:

Click the image to open in full size.

This setup has one big flaw: I'm sitting directly in front of the back wall which disrupts localization heavily. Hopefully a porous absorber will help.

Earl, feel free to add comments and additional information describing the process on how to integrate the subs.

Best, Markus
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Old 27th September 2008, 07:38 PM   #2
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Room size is 591 x 363 x 304 cm (width x length x height)
The pass-through to the kitchen:

Click the image to open in full size.
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Old 27th September 2008, 11:04 PM   #3
gedlee is offline gedlee  United States
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Markus

Excellent start.

There isn't much that I can say about the setup, I can see that you options are quite limited. Sitting against the back wall is a very seriuos issue, but I don't see that you have many options. I might try using the legth of the room for the listening dimension, but with the furniture that you have shown this would be difficult. At some point you might want to try the longer dimension and see if it makes a big enough difference to make it considered as an option. Seems like you could move things arround temporarily just to give it a try.

The main thing that you have to do now is to balance the subs with the room and the mains. I'll describe how I do this.

The LF sound field in a small room has tro be considered as a steady state situation - there is no direct field in the time sense as the signals have arrived from multiple directions even before a few cycles of the LF signal have occured. The ear is simply going to react to this by considering this a steady state situation. Now in the steady state we have to deal with the random problem of sound measurements to get at the mean value of this steady state sound field. This is best done, or has to be done, by spatial averaging.

So first setup the mains and the nearest sub. Set your spectrum analyzer to a very low bandwidth but not less than 200 Hz. and fairly long averaging time. This will yield a very long average of the sound signal. Take your mic and move it through large spatial positions near but arround the prefered listening position. Be carefull as small bumps of the cable can generate large eroneous signals into the mic. The sweeping has to be smooth. When the analyzer has completed its run you will have a plot of the frequency and spatial averaged LF sound field. Try adjusting the sub - never adjust the mains - to see if you can get a better response by changing the gain, the low pass point, the phase and or delay if you have it. The bass should be sagging slightly at this point since you will be adding in two more subs.

Now add in the next closest sub and repeat the entire procedure again. You should be able to improve upon what you had before. If not try turning off the first sub and setting the second one optimal and then add in the first sub. If you still can't get a better response with two subs than with one then you will need to move one of them. You need to get an improvement from the second sub or something is wrong.

Now repeat this process with the third sub. The third sub, when you are close to it should barely be audible. It it is loud, then once again, something is wrong. It should only be filling in holes at this point and not adding any actual level. The level after two subs should be about flat or possibly a slight rise - based on preference. I find a few dB rise at the low end is desirable for best effect.

With the three subs things should be quite smooth when spatially averaged. You can now use any EQ that you have to make a final flattening of the response, but these bands should never be more than a few dB. When you are done, if things go as they usually do for me, your should have a spatial average of about +- 2-3 dB. This can take several hours so don't be impatient. But once you have it you will never change it. Make sure and write down all the settings!!

Two people helps - one to sweep the mic and another to run the analyzer. Sweep the mike vertically as well as horizontally, but in a wide ellipse. Its not necessary to repeat the same pattern, its only necessary to NOT leave the mic in a stationary position. You can try wider sweeps or narrower ones, but the bigger sweep will likely be better.

Hope this helps. Good luck.
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Old 27th September 2008, 11:47 PM   #4
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Love your room, Markus.

Good luck with the layout.

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Old 28th September 2008, 12:20 AM   #5
CLS is offline CLS  Taiwan
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I have had a big bad midrage hump near 500Hz with that kind of coffee table in between speakers and couch.

However, for practical reasons, almost very one has this in living room.
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Old 28th September 2008, 01:45 AM   #6
col is offline col  Australia
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Pile the 3 subs on top of each other, ratchet strap them together tight and stick them in the kitchen pass-through. Play loud
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Old 28th September 2008, 09:19 AM   #7
terry j is offline terry j  Australia
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hi markus

dunno if you have the latitude or authority from those that must be obeyed to play around with the room layout speakerwise, but I have very recently given the principle outlined in the link and found it to be of great benefit to my setup

http://www.decware.com/paper14.htm

there were associated issues with it, namely a loss of bass extension (I presume because both the speakers and chair are now 'in free space') which I'm now in the process of fixing by (strangely enough) adding distributed subs, exactly as you have outlined here. In fact I started a thread on it, didn't realise we were kinda asking the same stuff!

Which segues nicely into Earles response before. Earle, do you mind if I copy your response into my thread?? It is relevant and the kind of data I was after amongst other stuff. I'd like to ask a few questions and may do it there if you're fine on copying your post to the thread, else I'll ask here, no big deal.

How to ACCURATELY integrat subs with mains (and a little challenge heh heh)

I know I have mentioned this (the topic in my thread) before and I remember you kinda disputing my premise a bit. I have since starting the thread done a bit more fiddling, and what I have found is that I am coming around to your point of view.

I need to repeat that fiddling but this time without a few beers under my belt, (just to confirm) so will do that in the next few days and admit my mistake in the thread heh heh. anyway, your post was exactly what I was after so would like to put it there if you agree.
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Old 28th September 2008, 09:34 AM   #8
infinia is offline infinia  United States
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Hey Markus,
If you haven't met your neighbors yet, I'd invite them over for drinks, and what not. Otherwise you could be introduced by them pounding on your common walls/floors. Then you’d have to change the names of the Nathan's famous to the "Mini Evictors"
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Old 28th September 2008, 12:25 PM   #9
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Quote:
Originally posted by terry j http://www.decware.com/paper14.htm
As far as I understand Steve Deckert tries to "group" the reflections of one speaker on walls near that speaker. But when I look at this picture that might be true for the left speaker but where would be the reflections of the right speaker?

Click the image to open in full size.

Best, Markus
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Old 28th September 2008, 01:05 PM   #10
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Default Take some measurements while you're at it?

Hopefully you are not a total subjectivist and are willing to take some measurements during your set up and evaluation phase.
If you don't have anything already, I suggest you try Room Equalizer Wizard (REW).

http://www.hometheatershack.com/roomeq/

It's a powerful feeware program for checking out your room's response. Hometheatershack's website is a strong proponent of this program. There's tons of posts there about using it.

http://www.hometheatershack.com/forums/rew-forum/



Just trying to help....
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