[flash]

in my best "don adams impression": the old "carpenter's squeaky door" syndrome



as many of you know, i was a touring audio engineer - one would think that automatically i would have the ultimate stereo system in everything - well, that's only half true



i did in fact finally go and get some great components, replaced the factory speakers, added multiple amplifiers, got a great deck, and designed a cool subwoofer enclosure, and did a heck of an install - however, i never spent the time to tune it - until today - i was actually a bit embarrassed when ether joe sat in my car and gave it a listen - that was the first time i had actually heard it anywhere near higher levels - it really pointed out to me that there was still work to be done - i just wasn't sure where it was



then the other day i had to disconnect the battery for some other work on the car - that meant i had to retune everything - this is a deck with time alignment, a real time analyzer, and the whole shooting match - it should be able to tune everything perfectly - so, i ran the tests and fiddled for a while, but still wasn't terribly happy



then i started thinking about what was going on, presumed nothing, and started from scratch



a key critical component in tuning a system is matching impedance of speakers to the output amplifiers - i did that just fine - i installed great speakers - i tested them with a known source - no issues there



ok - now let's check out the power - all high end amps, not getting hot, so what gives?



another, and often skipped step, is matching the output voltage of the deck to the input voltage of those amplifiers - more often than not, people just crank the amps up to full, and let 'er rip - i did the same thing with my initial install - at low levels and even turned up a bit, it was fine - however, as soon as you started really cranking it, it turned to poop - i also noticed that in the low mids it was mushy, and in the highs it was very brittle



after backing them down to the correct matching voltage, it was nothing short of absolutely amazing at how much cleaner the sound got, and how much life was added to it - i am pretty darned happy now - i still figure i have some road tuning to do, to compensate for road and wind noise, but i am pretty darned close



i think it's time for a long drive now

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[SILVY968]

the devil is in the details.

Brian

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[flash]

agreed - just glad i finally spent some time dialing it in - i never seem to get around to my own stuff

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[SILVY968]

glad it worked out.

Brian

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[Cloud9...68]

My head always spins when I read these audio posts (which is a nice way of saying, "Geek alert!" <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" /> ). I was driving around with my right rear speaker blown without even realizing it for probably several months, until my daughter, who was maybe 9 at the time and customarily rode back there, pointed it out to me. Can you say, "Tin ear?"



One thing that does bug me, though, especially in my coupe, is the road noise-induced drone the thing makes (I know, this has been discussed to death). Flash, with your knowledge of all things audio, how much of a stretch beyond the systems you've designed would it be to whip up an active sound cancellation system? These things are starting to make their way into new cars, and it seems like it would be the only way to drown out the din in our cars without adding many pounds of sound deadening material.



While the concept of active sound cancellation is very simple in principle, and doesn't require a lot of expensive hardware, I fully realize the devil is in the details, big time. Also, since you don't own a coupe, and you're buried in myriad other projects, I understand that something like this would be WAY down on you priority list. But is the idea of adding active sound cancellation to a finished car (as opposed to designing it in from scratch) completely far-fetched? Is there anyone you could think of (maybe contacts from when you were in the audio business) who might be able to take something like this on? Just wondering...

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[flash]

the drone varies from car to car - i've been in some that have none, and others that made me nuts



the software in the deck i have takes care of quite a bit of the harmonics of the body panels, but is tuned sitting still, so doesn't take into account road noise - deadening material, and well designed speaker installation resolves that



as for active noise cancellation systems, i am not a big fan of those - they "mask" certain frequencies that are a good part of the music - generally it's low mids - canceling those out ends up making the music sound mushy and thin - bose has played around with this, and i think they went way out of their way to mess up the audio - it's very difficult in a car, as the distances for each listener vary, and even left to right canceling on one ear can actually increase the problem on the other - this is because of how it is done - the inverse phase harmonic that needs to be generated varies from place to place in the car - very complicated stuff



the good news is that you don't have to use a lot of heavy material and blanket the whole car to cancel the drone - all you have to do is break up the resonant wave - determining where it is can be trying though - once you do though, a "dam" of sorts is all that is necessary to kill the drone

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[Lim Yong]

Hi all,

My previous 92 has dampening material in the back sides of the car, my current

93 does not...weird thing, on my previous 944, I hammered a small gap between the hatch and

body and it maded a difference (quieter) on the road. maybe something to do with air pressure??

PS. Don't recommend anyone do this.



I also found that when I try to attenuate one type of noise, other noises becomes more prominent.

example, rear road rumble vs front/engine etc.



Overall, I think sound deadeners do help and as Flash said, break up the resonance is best.



Maybe everyone can post what they've done and what type od noisse were attenuated.

thanks

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[Anchorman]

I find that when my passenger seat is unoccupied, most extraneous noise is gone. <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

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[gryphon]

[quote name='Anchorman' post='56390' date='Jul 16 2008, 10:41 AM']I find that when my passenger seat is unoccupied, most extraneous noise is gone. <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />[/quote]



See my previous post about trading in the wife for a 968.



Tom

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