Sweeps in Fuzzmeasure

[nixoblivion]

Ive been doing quite a few measurements in Fuzzmeasure latley (Interesting observation with Cornertraping!

I noticed something quite odd.
I used to always do measurements 20Hz-20kHz. But latley i realized i dont need to know what going on above 300Hz, at least not right now. So i changed the sweep to 20Hz-300Hz.

When i do the measurement, i can clearly hear that the sweep is stopping at 300Hz, everything fine.
But the measurements still show something completly different!
The measurements really dont matter right now! thats something completly different, im just surprised at what Fuzzmeasure is doing (10-23000Hz)! Im on Fuzzmeasure 2
Is this normal? am i doing something wrong?

[tonio]

Hey nix, its works for me on v3, although the capture ended @ 200hz.

play with the end silence i.e. longer.

T

[nixoblivion]

I can hear the sweep stopping under 1kHz. How can Fuzzmeasure measure up to 20kHz... its not even comming out of the speakers??

[AnthonyRochester]

that's a pretty bad frequency response for a sound card...

[DanDan]

Odd. I would recommend doing the full sweep, then use the zoom to selectively view.
DD

[nixoblivion]

Originally Posted by SAC

Without knowing more, you may be 'measuring' the sound card.

We tried to talk of this and the topic of resolution a week or so ago. But as I did not use the term "window" or "windowing" and tried to present the idea in terms of the time and frequency of the stimulus signal... as we had already established that few here adequately understand the term in the myriad way 'it' is used... a few took great issue while never addressing the basic topic.

So perhaps now they will return and address the topic in depth. And I am sure you will appreciate a description in terms of FFT sample size and time. As that is a topic everyone here is most intimate(sic!)!

Sorry for the wry humor, but you have brought up a good point regarding measurements and understanding some of what goes on 'under the cover'. I tried to breach the subject, but will now allow others to address it in a manner they will find more pleasing.

Also, you may want to post this on the support sites for FM and.or the other popular measurement tools such as REW, as this is a phenomena common to all - where you truncate the test stimulus frequency, but you still get a response above the truncation, and what 'it is doing'

Ive read your post a few times and i just dont really get what you are saying.
It seems that this is a typical occurance with all measuring programs?

but tonio says, he has not experienced this with the newer version of FM...

@DanDan, i did a test today, everything stayed the same. i only changed from 20-300 to 20-20000. The result in the graph was practicaly identical, a few db changes once in a while, but not very much. its very strange!

[DanDan]

FM3 seems to be a very big step up from 2. Well worth it IMHO.
DD

[tonio]

Nix,
What are you using for an interface?

T

[nixoblivion]

Originally Posted by tonio

Nix,
What are you using for an interface?

T

I have an Mbox 2. but i really doubt it has anything to do with that!
But SAC seems to have said, that this is common with all measureing software. Did i get that wrong?

[DanDan]

nix, nothing wrong, same behaviour here. Software developers sometimes provide facilities, often by request, without the full implications being taken on board. I think they kinda rely on common sense.
In this case you would simply ignore the data above 300Hz.
Or do the full sweep and examine below 300Hz by zoom afterwards.
FM 2 seems to have provided a curtailed sweep option. This might prevent damaging HF in Subs or whatever. Unfortunately the whole system is not curtailed pro rata. I have informed Chris about this although from the comments above he appears to have fixed it already in FM3.
The upgrade is really really well worth the few bucks in any case.
FM2 was great, particularly as it was the only viable Mac option.
FM3 has included considerable sophistication, possible class leading, without getting cluttered with too many options. I hope Chris sticks to this pattern.
DD

[tonio]

Just wondering what you are using nix. I am not familiar withe Mbox2 so doubt I can offer any help.
What i will add is that my MOTU 1224 & Lavry DA10 makes it difficult to use OSX's audio midi utlility causing FM to crash via the auto device correction loop.
Agreed with DD, FM 3 has ETC, and well worth the upgrade.

T