I'd like to use my pocket PC in order to tune my stereo setup. The software I'm looking at is relatively cheap and is called pocketRTA and it seems interesting and I've already got a pocketpc so it's only the cost of the software. Follow this link if you're interested in knowing more http://www.4pockets.com/software_info.php?...RTA&pro=&pid=44 . I know it has nothing on commercial setups but lets face it not too many people can justify buying a commercial RTA device.

Can anyone give me a basic rundown on how to use RTA in general to tune the audio in a car. A tutorial would be great but I'd be interested in some basic guidelines if not.

Thanks!

Basically all you do is run a sweep from 20khz to 20hz on your system, taking spl reading at intervals, and then try and tune your system (using an eq generally) so that you get the flattest response curve possible.

Sorry for being a bit new at this. Have to start somewhere. When you mean flatest response curve what exactly are you referring too exactly. Is it matching db levels across all frequencies to be the same (or close to it)?

Yes...
lets say you get a reading of 60db at 100hz, and 70db at 200hz.
Generally what people will do is lower 200hz so that it too is 60db, hence "flat" response between 100hz and 200hz.

Thanks. Seems easy enough!

from my research, a totally "FLAT" response across the spectrum doesnt neccesarily always sound the best to personal taste. sure, it might win you SQ comps, but i think a "flat" response doesn't take into account that we DO NOT PERCIEVE ALL FREQUENCIES EQUALLY.

Especially at low volumes. We're more sensitive to locational treble frequencies than sub-bass, for example.

Something to keep in mind.

Yes something definitely to keep in mind. I have a feeling the flat response isn't going to suit my personal taste but it'll give me a good baseline to make tweaks from so at least I know I'm not missing out on any frequencies that I might not be aware of.

Wade through this and get your answer
http://www.carsound.com/UBB/ultimatebb.php...ic;f=1;t=023462

as for my 2 cents, you can aim for a flat RTA reading, or you can tune the system and then check where the flaws are in the tuning.. your analysis reading shuold "flow" (for a lack of a better word and shuold be graduated with no more than 3db between each frequency band.

And its not a sweep fury - its Pink Noise..

Tuning via an RTA is helpful to see where the gaps are within the frequencies. Watch out as using a tonal equaliser can shift out the phase of the frequency you wish to adjust.

Using a RTA can be useful, but some people get it right with a RTA, and then adjust it according to there taste. Having a Flat reading doesn't mean you will win comps, or even place well.

Some stereos might have a great RTA reading, but can sound boring to listen to (someone said that to me once).

In fact a flat response normally doesn't sound good at all. What you want to do is ensure you dont have any peaks or troughs. Make sure adjoining frequency's are les than 3db up or down on the sourounding ones.

I found that midbass and sub bass up about 3 - 4db gently rolling off to a flatter top end from 600htz up sounded nice and performed well in comps.

Use warbles over tones, to stop phase issues...

to tune using an RTA, use pink noise.
in regards to tuning flat, be careful doing that.
for starters, the reflections in the vehicle can artificially give high/low readings at the mic for certain frequencies.
you may also find that the left side has a peak at a particular frequency, while the right side could have a gap. it would appear to be spot on when you meter it, but your stereo image will be out!

i tune to be reasonably flat (within 3bd), and fade to check that left and right are pretty close.
then i find the biggest adjustments in my EQ, and trim them down a tad,
remember if you add 6db at a particular frequency, you're actually asking the amplifier to put out 4X as much power.
so if you add +6db @ 125Hz,
where you are using 50WRMS for your 80Hz frequencies, the amp will be trying to push 200WRMS into the 125Hz range.
if you have a 100WRMS amp you may think it's within it's working range, but infact, it's not!
this can severly limit system dynamics, which is often why flat cars sound average.

oh and i forgot to add.
mic location is very important. i try to locate it as close to where my ears will be.
make sure there are no reflective surfaces within 50CM of the mic (you may have to lay the seats back to achieve this) a mic stand will greatly improve the consistency of your results.
i hold it with my hand, but i'm careful to be as steady as possible.

Did I miss that? Wouldn't that be a positive for 'flat' tuned cars?
So there aren't these peaks/troughs that limit system dynamics?

Peace

Tim

yes and no...

peaks and troughs don't necessarily limit system dynamics, although they will obviously upset the balance across the frequency spectrum

yes you want the smoothest response possible, but if it requires a small number of frequencies to be boosted alot (or a large number to have alot of cut on them)
then it will mean your overall average power output will drop.

you'll have 3-4 small frequency ranges which are straining your amplifier (pushing 100WRMS), and the rest of the spectrum will only be getting 25WRMS, average power output is now down to 25WRMS, before the amp is reachin it's limits.

large gaps are usually due to:
-crossover inadequacies
-reversed phase on tweeter or midbass (creates hole at crossover point due to cancellation)
-installation/interior problems, like reflection, poor location or angle of installation.

it's best to solve these problems by targetting the cause first.
adding boost/cut in these cases is only a bandaid fix!

Sorry forgot to clarify that, always use pink noise and i too check left and right as there can be some noticable differences.

Thx for this...
Interesting read as you can probably tell i've never done it before as I don't have an RTA handy.
The way i figure i'd do it though (with pink noise I see now ) is get it flat, and then adjust (within +/-3db) to make it sound "good" to me.

Either way, tune it how you want it to sound, not necessarily to be flat.

this pocket RTA... do you use a separate hand held SPL mic to plot the results or do you plug in a mic to the pc? Forgive my ignorance to these things.

It uses the pocket PC inbuilt mic (i'm not expecting miracles ). As long as the mic is consistent in picking up frequencies then it'll be fine but who know about the HP2200's inbuilt mic?

I think pocket RTA also comes with the PC based equivalent app as well which goes through your sound card and uses whatever mic you have. How good and accurate this is I have no idea but at $30 I might risk it when the time comes.

if the pc/pda has a mic/line in, better to get an external 'measuring mic' (can be as cheap as $80 - Behringer ECM8000) and a proper pre-amp (about $75 - Behringer MIC800), with the output feeding into the PDA/laptop.
This way, you get a much more accurate measurement

i certainly wouldn't trust a built in microphone!
not much point using the RTA software with that.