hificompass

Mikeg

He does a nice job with measurements. It shows in both English and Russian so make certain to hit the En button.

https://hificompass.com/en

Gowa

We have a 'Links' page with that listed along with others. https://rhythmaudiodesign.com/pages/speaker-building-links

jholtz

I hate to be the naysayer but has anyone noticed that his measurements don't agree with others?

Over at HT Guide some time ago I questioned his measurements on the Accuton C158 Curt and I used and of course it was measured extensively. He and some other followers from across the pond claimed that Omni mike wasn't capable of doing accurate measurements. They were dissing Curt's measurement methods which is when I decided they weren't relevant. YMMV....

Jim

Gowa

WOW! I didn't see that. I rarely go to that forum. Did the owner of Compass diss Curt?

jholtz

He and Curt had an exchange about measurement methods which basically ended in an agree to disagree. It's in Compasses thread over there with all of his other posts.

He may be great, I just trust measurements from Curt, Jeff B., John K. and more than a few folks on this board that follow established methods that we've all been relying on, for many years in my case.

I'm not trying to beat Compass up, just stating that he's swimming up stream if he won't acknowledge others.

I'm curious if the guys who do a lot of measuring have seen any differences with his measurements and theirs with drivers they are familiar with.

Jim

DanP

I have noticed that his measurements typically show higher distortion than other sources and maybe more questionable, is that his distorion measurements of various drivers seem more similar to each other than I would expect.

Not sure what to make of this site quite yet.

Dan

jr@mac

When I tried using smaller amps for measurements, I discovered distortion measurements became very iffy. Fifteen watts does not offer enough overhead for good distortion sweeps. Further, the mics most of us use (Umik, Omnimic, EMM, etc) are not capable of high enough SPL to do really high volume measurements in the nearfield in order to reduce room influence. 

This is why comparative measurements are important, so we can kind of dig out the actual performance. 

rjj45

I like a lot of things that he has done - testing at various voltages and distances for instance. We all used to surf to Zaph until he went fallow. As far as I'm concerned, the more testing, the better.  As good as Vance is, for instance, I wish he would incorporate some of SL's testing into his reports.

NavyGuy

Distortion measurements are essentially not directly comparable between different people's measurements due to the variances in equipment, room, skill, background noise, measuring distance, SPL, etc. So many people take this for granted and instead will look at two drivers and just say, "Hey, look at how low this distortion is" without realizing that the 90 dB measurement is at 1 inch so the driver isn't being tested in the same way as a 90dB at 1 meter. 

In my opinion, comparing to distortion measurements between different setups is only useful for seeing general bad behavior in a driver versus good behavior. Really what helps is having one person measuring consistently in the same manner. That will provide at least a relative comparison between drivers, even if the actual level is off.

dcibel

Agreed, NavyGuy. Far too often do I see distortion plots posted with absolutely no context of the measurement conditions, so the data is mostly meaningless. The same can be said of some frequency response plots as well.

HIFICompass provides some very good data, however you still have to take some consideration of the sensitivity of a driver when comparing. 2.83V on one driver might need 5V on another for a comparison of similar SPL.

Additionally, not all measurement systems do the exact same thing. Omnimic for example does it's sweep rather quickly, only a few seconds, so the noise floor is always high and you need a rather high SPL to get the harmonics above the noise floor, and then in some high end drivers you can run into SPL limitations of the mic by the time you can discern the distortion profile from the noise floor. If I recall, Hificompass is using a mic capable of some very high SPL.

SoundEasy on the other hand takes very long for a HD plot, 10+ minutes depending on the ferquency range chosen, every frequency is analyzed for several seconds to get the noise floor as low as possible. I may be misquoting, but I think in the SE manual it talks about taking an average of 6 MLS measurements can drop the noise floor by up to 12dB compared to a single measurement. The problem with SE long HD test is that you have to keep everything as quiet as possible for a long time, the furnace kicking in can mess up the result for example.

dcibel

As an example of noise floor issues, background noise when measuring with omnimic is generally around 30dB range. So a driver with a very low 0.1% harmonic will be 60dB down from the fundamental, meaning you have to run the test above 90dB to be able to see that harmonic rise above the noise floor. I think Zaph's method of running his tests at 94-96dB at 1/2 meter is a good choice for seeing the harmonic profile. Hificompass taking plots at various amplitudes gives a good idea of the driver limitations in addition to the profile.

jholtz

Thanks for the feedback. A lot of good information.

Here is what Curt posted at HT Guide in his discussion with Compass for reference;

"As far as my HD measurement conditions are concerned. I generally do not perform nearfield tests, nor test them on an IEC baffle. I instead test them individually at 1 meter on their intended baffle. This may not provide the same results as another measurement method, but I find that for myself they still provide useful information. I use 2.8v as this will result in something around 90 dB with most drivers. Since 90 dB is generally about the level I find comfortable for listening to most music, it is of some value to me to measure the distortion at that level. I also measure at 8 volts as that level will start to stress many drivers and make some of their flaws more obvious. I measure system HD plots the same way and at the same distance and levels.

I would suggest caution in basing a driver choice on just a few tests. With my engineering background, I used to pour over the various plots for different drivers thinking I could find the best driver based on measurements alone. -Many years later I realize how simplistic this viewpoint was, and now consider them just one tool in my arsenal. Remember your ears are the most sensitive measurement equipment you own, and should be part of your measurement regimen in order to find the optimum components for a specific design.

C"

Back to Compasses measurements, I can't figure our how far down distortion is from the fundamental on his graphs. I find Zaph's Curt's, Craig's and many others easy to understand. Their measurements are also less ragged. Through out the years I've also found the drivers sound as they measure in the final speaker using Curt's approach, which for me is the most important part.

So, can anyone tell me how to read Compasses distortion graphs?

Thanks!

Jim

dcibel

jholtz said:

Back to Compasses measurements, I can't figure our how far down distortion is from the fundamental on his graphs. I find Zaph's Curt's, Craig's and many others easy to understand. Their measurements are also less ragged. Through out the years I've also found the drivers sound as they measure in the final speaker using Curt's approach, which for me is the most important part.

So, can anyone tell me how to read Compasses distortion graphs?

Thanks!

Jim

Hificompass measurements are normalized to the fundamental, so they are telling you exactly what you need to know, how far down the harmonics are from the fundamental. Most other HD plots include the fundamental because it's needed for interpretation of the Harmonics.

jholtz

Thanks dcibel! That help.

Jim

dcibel

Those wacky Beliesma tweeters that are tested at Hificompass are now sold at Solen

e6zion

I knew they were expensive, but the cheaper aluminum Bliesma's are $700 a pair!