Setting up the Nathan 10

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#61
Sure it makes sense, its perfectly reasonable - its a "best fit" model. It also shows that the two boxes are identical despite the details of the impedance curves.

Many people don't realize that the least accurate points in an impedance measurement are at the peaks. As Markus says, the speaker is picking up the room noise and generating it back into the signal channels. This contaminates the measurement, which assumes no outside signals. The speaker is the best microphone right at resonance so the error here is the greatest. The peak location and level are totally unreliable data points. The best fit to the curve is the best measurement that you can get from a given set of data, but it should actually exclude the points near the peak.

I personally use cross-correlation techniques which exclude a great deal of this extraneous noise since it uncorrelated.
 
#62
markus76 said:
Sometimes there's noise louder 60 dbspl when a helicopter is flying along the Hudson activating modes between towers in front of our apartment:

Best, Markus
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Turn the Nathan to Hudson and yell through your measurement mic: ''Hey Donald Trump, land your tin can and let us be here! You are violating noise regulations and I gotcha in the Fuzz. Gonna litigate next time!''😀
 
#67
Guys - PLEASE don't think in terms of "crossover"! The subs need to overlap the mains NOT crossover to them. This is critically important to understand. Its the multiple source INTERACTION that smooths the response. If your "cross them over" then they can't interact.
 
#68
Sure, but you need to have a point to start from. Crossing them over like displayed in the last diagram already yields to a pretty good in-room response. Furthermore I'm surrounded by a drywall construction which helps tremendously in suppressing heavy modal behavior. In comparison the very rigid walls in a typical German construction are a major PITA.
I'm still investigating in equipment that provides an easy and fast way to do the calibration as described in post #3.

Best, Markus
 
#69
gedlee said:
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.
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Very interesting idea, and quite oposite what most people try to do when optimizing the bass. I will sure try it in my next installation.

When you write "closest sub", do you mean closest to the seating position or closest to the main speakers?

Do you have any recommended "starting positions" of the three subs where one should make the first optimization tries?

I assume that you run the mains fullrange, with only natural second order roll off of the closed boxes?
 
#70
Correct on mains roll off. I recommend one sub in a corner, one as far from the corner one as possible - usually a side wall - and then the third usually behind the mains. Often a two subs end up behind the mains with one in the farthest corner, which is exactly what Marcus did and what I have in my theater. The locations turn out to not be so critical when there are three.

I start with the sub closest to the mains.

Markus - what are you having trouble with- the space averaging? This can be a pain but most software will do it. Most software has a spectral averaging feature where you can average two or more spectrums together - Spectra Lab has that. Then you just move the mic to several points - say six - and average the curves. This works too, but its just not as fast.
 
#71
FuzzMeasure even has an automated averaging function. You just define how often the swept sine is played back. I guess holding the mic by hand and moving it in between the measurements should work fine.
But doing it with a live FFT analysis would speed up things tremendously...
 
#72
I think the differences come from the measurement distances.
......
But I measure at 2 meters or more
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That must be the case. Last night I did some gated measurements on my speakers. At 0.8 metre the response was different from the one at 1.2 metre which was nearly identical to the one at 1.8 metre. I think from now on I will do gated measurements at 1.5 metre, although the result is slightly noisier comparing to 0.8 metre.

I was very surprised at how effective the 50mm thick sound damping panels are. They are only used to damp the first, early reflections from the side walls and the ceiling. The panels on the side wall are made of fibreglass while the panels on the ceiling are made of foam. Both the side walls and the ceiling themselves are made of plasterboards. During measurement I also stacked 6 cusions on the floor between the mic and the drivers to damp the floor reflection. I could not observe any reflections until 18ms in the inpulse, which must come from the rear wall.
 
#73
Personally I think 3 subs located around the room is over the top. I don't dispute Gedlee, if done properly it will yield a smoother response, but I'm talking about LIVING with them 24/7.

A 7 channel surround system + 3 subs = 10 SPEAKERS!!!!! Each sub needs floor-space, and 2 cables (power and interconnect) running to it. The Nathans are not small satellites, they're big &%$#ers. I think Markus has done well to choose white to minimise their visual impact.

Is it just me, or does anybody else think that in a typical living room in a house or apartment like Markus's, what's being suggested is pushing the limits of domestic acceptability and is overly-complex?
IMO, even if it's just a 2 channel system, it's too much.

I would compromise, get 2 subs, and use them as stands for the mains. With some tinkering you'll get a nice response.
 
#78
If you just have closed boxes, just use a 2nd order LP, no need to make them bandpass. There is an advantage to an acoustic LP, but not to a higher order electrical one. The idea is a lot of overlap of the sources at LF. Each one operating in a different bandwidth or off of a different channel minimizes this overlap.
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I have been trying to grasp what Dr. GedLee said on multiple subs with great interests. I think the main points are:

1. The mains only go down to about 100Hz, 2nd order roff-off.
2. The subs cover from 100Hz down with a 2nd order LP.
3. All subs are mono. The stereo signals are summed to feed the subs.
4. First sub is placed near the mains.
5. Second sub can be placed at a front corner.
6. Third sub can be placed in the middle of a side wall.

However, from memory some articles advocate stereo subs instead of mono-subs.

We did a test of CD sources some years back and found that virtually none of them had stereo LF signals. So just sum the L + R and use that signal for the subs.
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What about classical music?


Regards,
Bill
 
#79
Practicality is something that we all have to live with. To me its impractical to buy $6000 subs, but apparently people do it. You have to do what is practical for you - two subs, three subs, JBL recommends four. Practicality and value are cornerstoners of my design philosophy, but make no mistake about we are talking about premier sound quality here, not boom boxs or Bose cubes. Of course, you need to do what is practical for you, but if you want to know the "best" way to do it, one that will yield a premier result then take my word for it, three is not outrageous, Nathans are not that big, and this IS the best sound that you can get for the money.

Yes, the classical music that we tested was mono below 100 Hz. Why wouldn't it be? Unless the recording mics are on opposite sides of the room they would naturally be mono.

As to the "delays" from multiple subs, you have to think in different terms when talking about LF in small rooms. It takes more time for the sound field to build in a small room that the time delays from the subs. And it takes our ears much longer to even react to sound at LF. Your ears cannot detect only one cycle of a sound waveform, its simply not possible. It takes time to be cogniscent of a LF signal. Thats why I support, as others do, LF reverb - just to extend the time frame of the LF signal so that the hearing system has time to respond to it.
 
#80
The amount of compromise you're willing or forced to accept is obviously going to be highly individual. If size is the big factor for your situation you can always go bose 😀

If you're going to build your own subs anyways you should be able to hide them very well. Why not make the shape narrow and tall for a lamp or plant stand? Or go truly mad scientist and build one into a coffee table or even the dead space in a couch and shake your bottom.

Markus, I downloaded fuzzmeasure but I don't see how to do a lot of these things. Can you point me to some decent documentation? Their website doesn't seem to have any.
 
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