Cabinet testing: RTAs etc.

[Rafael]

Maybe it's just me and I'm no good at searching the forum, but I'm not finding info about testing cabinets for frequency response etc and was wondering a few things such as:

1] recommended micing practice? I have a "flat" mic for testing, but wonder what is the best way to place mic for frequency response testing? Like, three feet away on center of cabinet? What's best?

2] are there any decent free-ware rta software that don't require a degree in computer science/linux lingo to understand how to opperate? I recall trying to set one of the freeware ones up a while back and the user interface was so complex I never could figure out how to simply get some white noise out and get a response curve...

3] I keep seeing stuff like "impedance sweep" and am wondering how one can do this easily with just a computer? I suppose if I have a function generator and a bunch of other test equipment it would be easy, but I don't....

I remember BillF saying a while back that equipment to get T/S numbers for drivers was complex, but it would seem to me that with a decent mic that getting a freq repsonse graph, and using that to tune a cabinet, would be pretty easy in these days of modern computing.

[greenboy]

Well, to get any results worth using you do have to know some stuff. That's unavoidable. But some of the easier-to-use ways to get both T-S parameters* and measurements come from Smith & Larson Audio, link to their site found in the fEarful wiki:

http://www.talkbass.com/wiki/index.php/Fearful#links

If nothing else reading around will give you an idea what's what.

Parts Express sells a product that was OEM'd by Smith & Larson but it's not as accurate or as comprehensive, and probably not as well documented.


* if I recall arightly the only T-S parameter that is not immediately forthcoming with such units is xmax, which is understandable given what xmax is.

[billfitzmaurice]

Originally Posted by Rafael

I remember BillF saying a while back that equipment to get T/S numbers for drivers was complex, but it would seem to me that with a decent mic that getting a freq repsonse graph, and using that to tune a cabinet, would be pretty easy in these days of modern computing.

Measuring the cab is done for final fine tuning of the design. But you can't design the cab in the first place without T/S specs, and measuring them yourself is a complicated process unless you have one of these:
http://www.parts-express.com/pe/show...number=390-804

The WT3 also will measure the impedance of the completed cab, which is more important than SPL testing as far as duct tuning goes.

[Rafael]

Unfortunately it looks like me mentioning BillFs reply about T/S parameters derailed the discussion: I _have_ the T/S parameters, and have crunched the numbers through WinISD but what I'm asking is about testing the completed cabinet: Any recomendations for RTA software I can run on my computer [win based] or any other test software for fine tuning the ports etc?

[billfitzmaurice]

I use HolmImpulse.

[Rafael]

Good grief....is the learning curve steep or am I just dense? I can't figure that out at all....wah! I did d/l something from Hughs/Ketner that does RTA, but Holm looks cooler, but the .pdf info file tells me squat....anywhere to look for a wiki on that product? Thanks!

[billfitzmaurice]

HolmImpulse doesn't come with instructions. Google 'holmimpulse' for use instructions that are posted on a few DIY forums.