[JohnR]

Oh yeah (quick edit here) the track is from Pete Belasco and is called Deeper. It's the second track on the album.

Thanks

I was thinking of just using eg Audacity on the file but this is good too.

[Rclark]

You really have to know AJ to get some of his posts.  He and I were bitter enemies for years until we met each other and came to understand each other.  Now I consider him a great guy and a worthy opponent/advocate in a discussion of differing points of view.  He will pull someone's chain for sport with more than a little understanding of the topic at hand.  Me?  I've been known to pull the pin on the controversy grenade and roll it into the middle of a room myself.

What is going on here is that there are some people that just don't want to admit that they don't know all there is about situational dependence in discussions.  Probably on both sides.  What we are trying to do is get to the bottom of a controversy that does not need to exist.

Agendas are what they are: we ALL have them.  That in itself is not a bad thing.  It is when we are unable er, .... unwilling to admit this that these things get out of hand.

Dave

I think it's pretty obvious to see what was tongue in cheek and what was a serious question.

[sfdoddsy]

Here is 35Hz and 40Hz. They are starting to drop off and level out now. Again this is typical for my room. The 25Hz or so peak for my room can be seen. Not a bad place for room gain.    Even allowing for that you can easily see levels over 100db below 30Hz even at 20Hz.

35Hz hit 100db.



And 35Hz and 40Hz levels could have been higher if I would have turned them up more. I had plenty of X-max left but didn't want to overdrive the amp, and at those higher frequencies I can't judge output levels by watching the woofer move.

That reading at 20Hz of 105db was about the limit in my room. And please keep in mind that this will vary a lot from room to room. These would not hit levels like this in a huge room.

And I am sure there will be some red herring in there somewhere that someone will come up with to say this isn't valid because of blah, blah, blah... oh well.

In the interests of science (and since I have been one of the main doubters) I'm going to run a similar set of measurements on my OB woofers tonight. They have (according their T/S specs) slightly larger Sd, the same Xmax, and similar Qts. My H-frame is 330 wide and 350 deep. My room is much larger than Danny's at 10m x 10m opening into another similar sized space.

The mic will be 4m away.

[rythmik]

You're the one who claimed a dry sound, not him.

Sorry guys. I know this is off topic and several members asked me not to continue. But just one last shot. 

Everyone has a view of how to make good/perfect sound.  AJ may think gradient is the solution to good sound. You may think it does not matter if it does not show on graph.  How about me?  I think coheerent system that performs exactly same (even with distortion as long as the distortion is low order) at any moment of time is the most important thing. Even in a system with distortion, as long as it makes consistent and coherent distortion, it is better than otherwise.

Now, in the "thermal compression" graph that I show, most readers mistook that as pure thermal compression. But it is not. I remind what a linear time-invarint system should really be. If you look at that thermal compression graph, that is when the input is a steady continous sine waveform. You can replace that with a waveform that is still sine but with variable amplitidue in each cycle. What is the output?  It is an system at time A has gain of 1.00, and yet at another time with 0.97, and yet another time with gain of 1.05.  Now you can replace the input with real music.  What characteristic is this system?   We can only say it is a system with memory effect, that its present state depends on how much heat has been burnt in the driver (in the case of Mills vs cement resistors). I don't want that. You can have that.  Note had the variation been random, that would be fine.  This relates to another view that I have which is very different from you or others. That is the difference between noise vs distortion.   The difference is very subtle, but it is mainly "the correlation to the signal". If you heard the effect of digital dithering, it is a demonstration that by randomizing a so-called quantization distortion, it actually makes the sound more intelligible.   Correlation is based on statistics. The fact that is statistical, it means we cannot look just one input pattern, or one impulse response, or even ten of anything. Now you ask me what a "incoherent" sound will sound like to me, I can give you  all kinds of adjectives, including "dry" depends on the type of incoherence and you cannot fault me and that is how an incoherent sound trick me to think.

[EDIT] just to give some perspective. Dave mentioned temperature coefficients (TC) of cement resistors can have up to 600ppm/per C. That is 0.06%/per C.  Typical distortion of power amplifier these days is 0.02%. 


OK, I rest.

[HAL]

One thing that is missing is adding the real room gain into the modeling so that the basic model being used for the design can be coupled with the real world room.   The best model that I have see and used for this is CARA.  It allows the user to model the room, room materials, acoustic materials and speaker system to give good placement options for speaker systems in the room.  Problem is that it does not support OB speakers.

I have in the past contacted them and had new capabilities added.  This would allow folks to try models of speakers in the model room and get ideas.  It also allows for Auralization of the room/speaker combination to hear what the models are showing.

I have tried it with models for mini-monitors and LS6 speakers with very interesting results.  I set my mini-monitors up using the suggested placement and had excellent results.  I did it for LS6's in my room as the model would not handle the number of drivers in the LS9's.  I asked about adding more drivers for line array modeling in my room and waiting on the response.   

This would give a more complete model of the entire room/speaker system.

[THROWBACK]

Here I go again, jumping in when I don't know what I'm talking about. Seems to me the graphs--revealing as they are--are all based on steady-state sine waves. I know Danny's servos will go very low at high amplitudes with sine waves. I'm still hung up on the "jump factor." Is it possible to measure the effects of transients? If that has been discussed, I missed it.

[Danny Richie]

Hey good morning guys. Still going at it huh?

I will be headed out later today to a soccer tournament in Dallas that will keep me tied up all weekend. So you may not see my participation too readily.

Brian and Danny, I would love it if you would stop avoiding questions like the ones poised by AJ of Soundfield Audio.

He wasn't talking to me.

[jtwrace]

BTW-what computer do you use for your tests?  Apple or Mac?

He wasn't talking to me.

I was though.   

[HAL]

Jason,
If you are talking about Danny's CLIO plots, the CLIO system and software run on a PC.  I have one here as well.

[jtwrace]

If you are talking about Danny's CLIO plots, the CLIO system and software run on a PC.  I have one here as well.

I am using a prototype DAC from db Audio Labs. I have been in the beta testing group for its development for the past year. Big strides have been made. No wait, "huge" strides have been made...   

I did A/B compare an earlier version of it to the Light Harmonic DaVinci DAC. That is another really good DAC. I think at the time it was $12k or something. The latest version is now $20k. So a bit pricey, but at the top of the performance chain.

[Danny Richie]

Jason, I thought you were kidding when you said Apple or Mac. Isn't that the same company?

HAL is correct. My testing system runs on a PC. My listening system uses a very highly modded Mac Mini.

[jtwrace]

My listening system uses a very highly modded Mac Mini.

Interesting.  I ask as at RMAF I asked if you could play some tracks from my USB stick and you said that you didn't know how to do that as your not a Mac guy.  That really shocked me and others that I've spoken to.  Oh well.

[dBe]

You said:  "What's an "808 drop"?

18 to 26 Hz is half an octave. When you have output dropping at 18dB/octave and excursion rising at 12dB/octave, half an octave could be considered significant "

I guess that you missed my first post, John.  Here is an explanation of and 808 drop -

"If anyone is familiar with the old analog synth Roland 808 drop, the fundamental is 18Hz.  At RMAF we had people's pant legs flapping and glasses in the bathroom rattling around on the granite countertop.  The music piece in question is Pete Belasco's "DEEPER".  A low frequency tour de force.  Anyone that was there can attest to the feeling of air shuddering in the room at 18 hertz as well as the limit of audibility sound associated with it."

The purpose of that efferct was tohave the 36Hz tone in the program material and the 18Hz fundamental modulate the track associated with it to give a pulsating effect.

Yes, the 8Hz spread is ~ half an octave.  You can, however see the SPL on Danny's graph at 20 Hz.  That limit has been the bone of contention, not 18 Hz.  Don't forget to add room gain to your equation.  In a small room it is signicant even with open baffles.  Certainly not enough to make up the difference, but it will basically make up for a significant portion of the the excursion differential.  Gotta put in all of the numbers.

I said in response to Rclark: "The big controversy was if an open baffle could produce these kinds of SPL's... in particular the GR Research servo controlled ones.  This WHOLE issue is not about "other drivers".  It is about the GR Research LF modules."

You said: "Dave, no I don't think so. It was just a question of how OB drivers behave"

I would have to say that the discussion was about Open Baffle Drivers for Maggies.  I would also say the for the last 18 pages the issue (as denoted by the word "controversy") has been about GR research and Rythmik and the GR servo-controlled powered LF modules.  Could be my imagination, I guess 

Dave

[Danny Richie]

Interesting.  I ask as at RMAF I asked if you could play some tracks from my USB stick and you said that you didn't know how to do that as your not a Mac guy.  That really shocked me and others that I've spoken to.  Oh well.

I am not a Mac guy. A I am a PC guy. If I had 15 minutes to figure out how to get your memory stick files to play. I might figure it out. If Eric would have been handy I would have given it to him. He is a Mac guy and would have done in seconds. Don't be too shocked. Most of the audio community (especially the older group of guys) still does not understand computer based audio at all. I'd love to have time to get better at learning about the Mac but I spend all my time running a business and have little time to learn a new operating system. I'll get there though, eventually.

[Davey]

The output impedance of the amp is lower than that. What I meant was the extra headroom on the amplifier has when it has only 13.5ohm load vs an ideal standard 4ohm loads.

What is it then?

I performed a simple calculation on the numbers you quoted.  How could it not be 1.6 ohms?

Are you not attempting to make the amplifier as close to a voltage source as possible with this servo configuration?

Cheers,

Dave.

[rythmik]

What is it then?

I performed a simple calculation on the numbers you quoted.  How could it not be 1.6 ohms?

Are you not attempting to make the amplifier as close to a voltage source as possible with this servo configuration?

Cheers,

Dave.

I used a combination of current feedback and sensing feedback. It is not conventional stand alone amplifier that you can measure output impedance.  If your 1.6ohms is used to model the headroom dependency on loading, then you can be onto something that I am not aware of and it can be  quite useful.

[rythmik]

Unibox gives:

It seems fairly comparable, although the excursion is higher (but 18mm at 20 Hz). One discrepancy is that I used 90W to get that excursion, whereas your screenshot seems to show 400W. I used Sd=479.2 as per your Klippel test.

You have your power adjusted for nominal Z which is 16ohms that you must have entered. I am lazy and I set in all of my simulation as 400W@4ohm. I did this because I don't intend to include load dependent output power.  But in real world, the output will be 260W@8ohms (or something like that depending on wall voltage, eg, 115V vs 120V)  and I-don't-know what output @13ohms.  If we plot amplifier output against load, not only the it depends on resistive value, it also depends on reactive value. But that is entirely different subject.

[Davey]

I used a combination of current feedback and sensing feedback. It is not conventional stand alone amplifier that you can measure output impedance.  If your 1.6ohms is used to model the headroom dependency on loading, then you can be onto something that I am not aware of and it can be  quite useful.

Well, if the voltage measurements you quoted are correct then the output impedance IS 1.6 ohms.  At least at those frequencies under steady-state conditions.
This indicates a damping factor specification of only 2.5 for a four ohm driver and only 10 for a 16 ohm driver.  (Or DF of 1.8 if a "traditional" damping factor calculation is used.)

You quote a Damping factor of "160 @ 4 ohms" on your website.
"(Note: damping factor is speaker wires dominated. Without speaker wires, the native damping factor is >800)."
That implies a very low output impedance.  So, that specification does not agree with your quoted voltage readings in the previous posting.

Cheers,

Dave.

[rythmik]

Well, if the voltage measurements you quoted are correct then the output impedance IS 1.6 ohms.  At least at those frequencies under steady-state conditions.
This indicates a damping factor specification of only 2.5 for a four ohm driver and only 10 for a 16 ohm driver.  (Or DF of 1.8 if a "traditional" damping factor calculation is used.)

You quote a Damping factor of "160 @ 4 ohms" on your website.
"(Note: damping factor is speaker wires dominated. Without speaker wires, the native damping factor is >800)."
That implies a very low output impedance.  So, that specification does not agree with your quoted voltage readings in the previous posting.

Cheers,

Dave.

Now I know what you meant. With the supply voltage of 80v, the output should be capable of 56VRMS. But with 4ohms, the load power will drag down the supply so that the output starts clipping when it exceed 40VRMS.  If we replace that 4ohms with 8ohms, the output wont start clipping until say 46VRMS. Those are the numbers that define the max output. If you keep the input voltage the same, as long as the amp is not into clipping, it will supply constant voltage regardless the load. This is for nonservo configuration. In servo, it will supply more power to keep sensing signal (or cone velocity) at the same level. There is no definition for such behavior.

[AJinFLA]

AJ may think gradient is the solution to good sound.

No Brian, I think gradient LF systems are a method for good sound.
I think your LF servo system is a method for good sound. Neither are the method/solution for good sound. There is a difference.
Having spent 10+ years listening to wide varieties of each (instead of say, resistors) in wide varieties of rooms, has lead me to such conclusions. YMMV.

You may think it does not matter if it does not show on graph.

You can't quote me saying that. My actual position was made clear. If the "sound" is in the soundwave reaching the cochlea, it is measurable. If the "sound" is reaching the brain by alternate methods, the onus is still yours to show evidence of such.

How about me?  I think coheerent system that performs exactly same (even with distortion as long as the distortion is low order) at any moment of time is the most important thing. Even in a system with distortion, as long as it makes consistent and coherent distortion, it is better than otherwise.

If I had a dollar for every audiophile "theory" posited as cause>effect.....

Now you ask me what a "incoherent" sound will sound like to me, I can give you  all kinds of adjectives, including "dry" depends on the type of incoherence and you cannot fault me and that is how an incoherent sound trick me to think.

[EDIT] just to give everyone some perspective. Dave mentioned temperature coefficients (TC) of cement resistors can have up to 600ppm/per C. That is 0.06%/per C.  Typical distortion of power amplifier these days is 0.02%. 

So if I have this straight, the Mills is more "coherent" than the sandcast when used in your sensing coil?
Or is it simply passing less "distortion" (of unspecified variety)? Hmmm. Last I checked, it is often the case that the lower "distortion" DUT is the more "sterile" or "dry".
IIRC, wasn't there a test of opamps to find differences in "sound", where it was found that the preferred ones...had higher distortion (much like some tube amps with even order THD, etc.)?
What shall we call this, the "Inverse law of Dryness"?
 

cheers,

AJ