Proper level setting..

[Ractis]

Just curious to find out, did any bro here have your level/gain settings done using proper test signals and an oscilloscope? If so, may I know which installer you went to or if you DIY?

 

thanks!

[Bobcatsysop]

Hi Eric,

Most installers can do RTA at your special request but I have not heard about oscilloscope, sorry..

[Headshok]

o scope the best, can literally see the signal clipping.. hahahaha..

 

easiest and effective way= multimeter.. heheh..

 

who wanna sponsor me fluke multi meter.. hahahaha

[User12343]

you can use oscilloscope/digital multimeter provided ur amp manual indicates so. eg, JL slash series amps, they tell you to disconnect the speaker outputs, connect the amp outputs to the scope/DMM, play back a 0dB test signal (with no EQ/loudness/MX and no DSP), start with the gain control all the way to min. the manual tells u to observe the target AC voltage readings while slowly turning up the gain to an optimal value.

 

if ur amp does not show this info, you cannot accurately determine the optimal gain. then only u can use guestimate to determine.

 

reduce ur gain all the way to min. crank your HU volume to 75~80% of max volume*, turn up the amp gain slowly until u hear distortion, then lower back a bit. this approximate setting shd not be too far from the optimal level to match the HU rca output and the amp inputs.

 

*note that your HU volume at this level should not be clipping/distorting (to do this requires u to use a scope to probe into the RCA preouts, else it'll be impossible to get any optimal results outta it.

Edited June 3, 2007 by User12343

[Ractis]

thanks for the responses so far...

 

hmm I have a DMM, is it enough to set the gains properly myself?

I think I dont mind going to an installer to do setup and RTA, but I'm just afraid later they only go by ear or use agaration only, thats why I wanted to find out which installer really have proper tools to do level setting and RTA

 

Actually.. do you guys perform RTA yourself using a laptop, software and SPL meter? (I have a rackshack SPL meter actually)

[User12343]

No, even if u have a DMM, you wont be able to figure out. your amp max output voltage unknown, so the question is, how high is high and how low is low???

 

Please note that RTA is NOT an accurate measure to determine optimal gain. what it simply does is to determine the EQ levels. the RTA tells u that a certain frequency is too much boosted/attenuated and tells u to re-adjust, it DOES NOT tell u the gain on the amp.

[Boring]

Even if you have oscilloscope, if you do your gain matching using a signal recorded at 0db, then i guess you'll not be actually getting the "max" out of your amp. Most music track are recorded well below 0db.

[Ractis]

Hi, bro headshok said the easiest way is to use a multimeter.. I was wondering how too, maybe he can elaborate more ;)

 

As for the test tracks for amp gains.. i have various tracks recorded at 0db and -10db which should help.. I think it is usual to use -10db to set gains. I suppose reputable installers should be using similar stuff to setup the car's sound system, but so far I've been to about 3-4 but they never setup the amp gains for me this way. Only use their ears or even just leave at default 'middle' setting.

 

and lastly the RTA, I understand its for EQ. I actually downloaded a software called room wizard which can be used with an SPL meter, but havent gone down to doing it yet. If any bro has done your own DIY RTA using laptop and SPL meter.. maybe can share your experience?

[Yanuk]

i only have 1 time experience with laptop RTA but not for car setup. for laptop RTA, you need to "calibrate" (correct word is actually 'profile') the internal sound card that processes the mic in and match it to the mic's given characteristics. Given the unlimited differences in hardware config, most will opt to use an external USB-based profiling sound card to capture the sound. However, it all boils down to your tolerance level to inaccuracies. I felt that since I was going to do an RTA, I might as well do a proper one. Else I might as well go by ear right?

 

 

Ultimately, the system was not adopted because carrying a laptop on site was troublesome and battery life was very limited. The traditional handheld RTA was more than sufficient and used instead.

 

Using an oscilloscope to set the optimal setting for each amp will only give you the max output without clipping. If you have more than 1 amp, it is not very useful. You can only find out the max useful gain of the amp.. If you were to tune each amp using the max output without clipping, you may not (99% of time you won't) get good harmonious sounds.

 

 

Imagine 3 runners running at their top speed, all performing at their max levels, but none of them running together in pace.

 

You will may need to tune down some of the more powerful amps to match the weaker amp (

Not to mention when you connect different speakers to the same amp, the volume produced may not be the same)and RTA as the last step is unavoidable because the RTA will read and give you the readings for the output from the speakers. Which is what you will be hearing.

Edited June 4, 2007 by Yanuk

[Boring]

I'm going to try Room EQ wizard tonight. There's a few things you need to do before you actually start measuring. The soundcard and SPL meter needs to be calibrated before you actually start taking measurements. I planned to try it on sat but after calibration I gave up.

 

Tonight i'll try and see what the result is like. Oh yes, you can use the software for TA as well.

Edited June 4, 2007 by Boring

[Hyun]

eh boring u calibrate liao ah? wasted leh.. i have been wanting to calibrate the radioshack SPL meter, could've done it together, much faster ... u finish liao isit? if not i meet u with the meter.

[Hyun]

wah yanuk crouching tiger hidden dragon, now hiding where? RTA your vifa and come join us on wednesday lah :)

[User12343]

my 2-cents' advice for RTA is, dun take the values too seriously. i once heard a so-called RTA-tuned setup by one of the well-known installers, and the result is totally disappointing.

 

RTA are just simple machines that have no feeling. they are just programmed to detect for the 1/3-octave 1/6-octave frequencies, where those "in-between" frequencies are not factored into consideration. they dun really guarantee the end-result in terms of tonality, spectral balance, etc...

 

try as they might to closely mimic the human auditory response, more often than not, the result is way off....

 

try your best to use RTA to tune, the differences will be very revealing.....

[Boring]

Yes you're right in some ways. But generally installers only do RTA with all drivers together. What should be done is do RTA with left and right drivers seperately, after that do another round with all drivers.

[Yanuk]

hehe.. no lah where got dragon and tiger.. Didn't RTA my setup.. too troublesome and don't feel safe borrowing such expensive equipment home and erm.. basically lazy lah...

 

my setup cmi one.. only slightly better than stock

 

ok will drop by this wed late for a kopi

[Yanuk]

yah i understand that.. usually the RTA is just to get the standing freq of the enclosed space and EQ it such that I get as close to flat freq response.. from then there will be a basis to EQ for better SQ.

[Ractis]

Useful reading.. just pasting here for future reference

 

http://www.resnet.trinity.edu/areynol1/gain.htm