Electrostatic Vs Everything Else

I think Arnaud was working on ear pads and showing that it should be expected that different ear pads would exhibit different notch behavior. However, the point was not that there was such a notch-pad dependency. The point was that one is likely not going to get a nice smooth frequency independent "planar" wavefront in a headphone. Stat or no stat.

Interpreting the IR directly from a set of measurements that apply compensation to the frequency is probably not ideal. I could say the exact same think about square waves.

That said, some of our measurements here are not compensated. So the impulse response and the square waves are in agreement with the frequency response. I might be able to check the impulse response of my measurements...

AFAIK compensation is bandlimited and can't do much to make things "faster". In fact, the compensated square waves by Arnaud IMO are not settling "faster". The difference is that the system went from overdamped to underdamped after compensation.

 

Yes. after compensation things become fairly underdamped.

I do have somewhat decent 009 measurements along with a lot of other measurements. Maybe even an HD800 and a bunch of HD600 like stuffs. If I can get access to the raw impulse response I could plot them. These would be from uncompensated measurements.

As far as bandwidth, note that the mic will also roll off at some point. Most audio equipment is supposed to do pretty good in the audio frequency range, but not so hot in certain ultrasonic ranges. Which IMO really doesn't matter. I think when folks are talking about "speed" in a subjective context they are more than likely referring to a particular sound signature. Not how fast the diaphragm stops which start to turn into an ultrasonics discussion.

 

Measurement grade mics should be relatively flat (relative to what headphones do) in the audio range. I know there is all these talk about having to compensate your mic or else everything you do is shit. However, I don't think things are that far of in general from bass to upper mids.

Compensating the mic will have a similar impact on the measurements as compensating for ear simulator. Though much smaller. Again, unless the mic is broken or something, usually the headphone may exhibit more variation than the mic itself. From what I've seen at least.

Mics are bandlimited though. Very expensive ones probably less so, but still band limited.

 

LOL! I think the majority of measurement mics are omni-directional electret condenser mics. Which I think are also called electrostatic microphones. I think this is an area where electorstatic audio stuff has become main stream, and sort of cheap.

Bias voltage I think is more like 48V though. Not 600 something hairy volts.

 

Maybe I was reading the square waves wrong.

I was these were before compensation:

http://www.changstar.com/index.php/topic,496.msg8491.html#msg8491

And these were after compensation:

http://www.changstar.com/index.php/topic,496.msg8527.html#msg8527

But not sure now.

 

I think I better understand what's going on. The problem is that the compensation had to be inverted before it could be applied.

The correction is a subtraction. But in dB. So it's a division. One would have to invert the correction to make it a multiplication. Then one would take the IFFT of the inverted correction and convolve it directly with the square wave to get the compensated results.

Anyhow, here are the impulse responses, from top to bottom for the SR009, HD600, and HD800:



The impulse responses do not need compensation to reflect on the frequency response previously reported, since the frequency response reported was not compensated. I could smooth out the curves (equivalent to valid interpolation), but I'm kind of tired right now. Long day.

To obtain square waves one could just convolve an ideal square wave with the above IR.

 

So which Gilmore amp are you talking about? From which builder? Prices vary for different reasons... We need a little more of a specific example to respond.

 

There's no unobtainium in the new amps as far as I know, so the cost is a combination of the actual parts cost, some cost for the labor, and a little mark up for profit. The amount of profit that can be added is driven by the market, but you certainly can't ask these guys to build for "cost".

Most the builders I'm aware of building good Gimore designs are not making a killing, and most dump the "profit" into prototyping whatever the next latest and greatest is. Go ahead and grab the BOM and total up the parts cost; the information is openly available. Then you can decide if the difference of what they are charging is worth their time, experience, and getting a realible amp delivered.

Having built several KGSShv's while living in Europe I can second Birgir's comments on taxes, figure 20-40% higher for parts cost vs. the USA. Many would say these are simple amps, but hard cost can clear $2000 easily depending on the parts selected, shipping cost of seperate components, choice of chassis and attenuator. That's not incuding any labor cost.

I support the guys who do quality builds to get paid a little for doing good work. I don't like seeing some flippers selling off builds they baught for more than they paid just because the market will support it... but hey, it's a free market, right?

The beauty is that the designs are readily available for free along with great internet support. If you want to build it as cheap as it can be done, the best way is to grab a iron and DIY! It's very rewarding.