Suggestion for Forum Discussion Group - Audio Measurement

[ruffrecords]

I vote for it.

Cheers

Ian

 

[JohnRoberts]

I like the idea... I always measure in some way what I'm building but I wish I have a reference from somewhere else to compare with...

The other section I would like to have around is about acoustics, but I don't know if there is enogh intrest in this forum about it, I've seen a couple of topics but not so well organized.

I go with 'art of noise'!

JS

Acoustics is a rather broad category, and already involved in transducer (loudspeaker and microphone) design, but one sub-genre, "room acoustics" is often under discussed.

Room acoustics can dominate the playback sound we realize even with ruler-flat speakers and electronics.

Everything matters and we often submerge our attention on swapping out capacitors and ICs, when perhaps we should be putting  some egg-crate up on our walls.

[veer] One philosophical question, why does every studio monitor system differ so dramatically from typical listening playback systems? (probably because consumer playback varies too much to come up with some useful standard target) [/veer]

JR

 

[chrispbass]

Good idea alexc. I'd personally welcome some 'hand holding/walk through' guides on how to approach some of the typical measurements needed to gauge the performance of equipment if anyone can provide them?

 

[JohnRoberts]

Good idea alexc. I'd personally welcome some 'hand holding/walk through' guides on how to approach some of the typical measurements needed to gauge the performance of equipment if anyone can provide them?

I co-authored a book on audio measurement, that we printed and provided free with purchases of the LOFTECH TS-1 audio test set i designed back in the '80s. I don't have electronic files of the original text and images, but there were lots of them printed.

Some of the discussion is archaic (like adjusting tape recorder bias osc), but lots of rudimentary discussion perhaps useful as a starting point.

AFAIK there is no commercial interest to prevent grabbing scans of useful sections.

http://books.google.com/books/about/Audio_Measurements.html?id=000WHAAACAAJ

JR

PS extra credit for finding my mistakes..  8)

 

[emrr]

The Audio Precision website has a ton of resources in the downloads section.  You may have to create an account to download anything.

http://www.ap.com/download/whitepapers

 

[kilmister]

Great idea. +1

 

[joaquins]

I like the idea... I always measure in some way what I'm building but I wish I have a reference from somewhere else to compare with...

The other section I would like to have around is about acoustics, but I don't know if there is enogh intrest in this forum about it, I've seen a couple of topics but not so well organized.

I go with 'art of noise'!

JS

Acoustics is a rather broad category, and already involved in transducer (loudspeaker and microphone) design, but one sub-genre, "room acoustics" is often under discussed.

Room acoustics can dominate the playback sound we realize even with ruler-flat speakers and electronics.

Everything matters and we often submerge our attention on swapping out capacitors and ICs, when perhaps we should be putting  some egg-crate up on our walls.

[veer] One philosophical question, why does every studio monitor system differ so dramatically from typical listening playback systems? (probably because consumer playback varies too much to come up with some useful standard target) [/veer]

JR

EDIT: something fail with the first post. Take 2.

I should said room acoustics... Now I'm in order to make a couple of traps and diffusers for my room and the couple of topics aroun for this are missing around.

IMHO It doesn't make much sense have a flat response down to 0.2Hz in the rig and have a 15/20dB notch at 100Hz in the room and a 120Hz 10dB peak because this will take us to make a wrong desicion when mixin... I think we should pay more atention to our rooms.

JS

 

[poctop]

+1

 

[sahib]

The Audio Precision website has a ton of resources in the downloads section.  You may have to create an account to download anything.

http://www.ap.com/download/whitepapers

I have a copy of the Audio Measurements Handbook. Good reference.

 

[alexc]

Thanks JR for posting the Loftech papers - very interesting read.

I'd like to register at the Audio Precision site - although it would be several more lifetimes before I could hope to be a buyer!

Already the game is lifted up some  ;D

(don't mind my silly optimism - I've just had a great day in the music room with all the diy working and sounding great!)

 

[flaheu]

+1 with this.

By the way I'm noodling with TrueRTA software (free version for 1/3 octave with no sound card compensation).
It's pretty handy and the full version is not expensive.

Anybody ever tried it ?

What's your opinion ?

 

[alexc]

True RTA is very good. It has a few quirks but probably the best one out there for the diy-er.

Apart from the usual features, my favourite is the ability to calibrate  to absolute voltages.

It is provided for use in it's CRO functionality and has the benefit that resulting dBu measurements reported have some meaning across different measurement systems. Unlike systems which simply report 'dB below FS' measurements.

Again there are some quirks in operation - most notably in handling of balanced/unbalanced signal conventions.
I'm no expert but my measurements indicate some unexpected results in this area. It would be an interesting exercise to define a method for the calibration.

Other things of interest are that it reports a strongly rising noise floor characteristic as frequency increases.
I've tested on different systems and always found the same thing. There's no detail I've come across regarding windowing and such so I don't know much about it.

And some of the measurements seem to depend on the display settings selected.

But generally I think it's the best one out there for diy purposes!

 

[shot]

Smaart 6 (and I guess ver. 7 also) has a great analyzer!
Very easy to get frequency and phase curves for test gear.
http://www.rationalacoustics.com/

 

[Gold]

I'm for it. I can add a copy of the original RCA/NBC spec for the VU meter to start off. I find getting good measurements to be difficult in a lot of cases.

 

[thermionic]

Seeing the umpteenth 'oscilloscope recommendation' thread makes me think Alex's original post has a very good point. As things are, if someone wants say, a new scope, it could be posted in either of the 3 main forums. It would make sense to have a measurement / test gear forum, where everything could be neatly in one place; you name it - standalone FFTs, programmable loads, oscillators and all kinds of stuff.

Good idea!

Justin

 

[deuce42]

It's a great idea Alex.  Look forward to reading the new subforum if it happens

 

[alexc]

Thanks for the support for the suggestion.

I'm very much hoping Ethan will give it the go ahead.

To .. make the world a safer place .. for our diy.

There's so much measurment technique for us to learn, practice and understand!


Even for those without the full pro kit  ;D

 

[Ethan]

In the interest of fairness, is anyone against this idea?

 

[[silent:arts]]

no. I would welcome this.

 

[spase]

i'm a supporter on this idea.