Just to take this one step further. I am the VP for a company that has a lab that specializes in doing acoustic and vibration measurements mostly for Aerospace and Automotive customers. In said lab, we have over $5M worth of NVH measurement equipment. If I asked for any of it to be shipped to my house overnight I can have it here. I am proficient in operating all of it. I would still never use it any of it for setting up my car stereo. A simple analyzer for measuring time of flight for delay sure, but the rest I see no benefit in using.

If I were to compete, it'd be a different story though. Being able to determine the modal response and tune the car to help your SPL score has merit. Regrettably that takes $250k worth of gear to do+ and days of measurements. Of course in our lab I can do it in a couple hours.

show off

In general I REFUSE to use any of my background as justification for any discussion. My words can speak for themselves, but in this case since it is specifically about testing I thought a glimpse of what my normal world is like might shed some light on things.

my installers at work use their experience in competition as a reason why pretty much everything i have said in this thread and am over thinking is worth while digging into. The competition world is the same as the install world of normal radios as far as i am instructed with the exception of less volume.  I do see now how they differ from one another, i only wish i had someone in the shop with a background more like yours so as to not leave me second guessing everything all the time.

 

I do intend to fully grasp the loud speaker cook book but given as im only a few months into car audio its a challenging read to put into practice conceptually. once i get into more car audio builds and start playing with various types of speakers im sure it will become more apparent to me.

 

the reason i had asked about the audio control clipping lights is that in their guides audiocontrol states that you wont clip any signals if you use their products and my installers also tell me that those lights are all you need to ensure you are not clipping.

I think you mean their lack of experience.

lol, yea thats what i mean. i juts want to learn the right thing once, not have to keep going back and fourth and fact checking everything. i suppose there is something to be said about doing research to better understand what you are being told but when work cant even get something as simple as how an electron moves through copper in a DC power circuit it sort of throws that out the window.

In general I REFUSE to use any of my background as justification for any discussion. My words can speak for themselves, but in this case since it is specifically about testing I thought a glimpse of what my normal world is like might shed some light on things.

 

great point. I'm jealous of the toys. 

is there any truth in that having a head unit that you can turn off its internal amplification can provide cleaner sound through its RCA's than a head unit with its internal amp remaining active?

Has anyone used an EQ to help a cross over? for example say we have a tweeter rated for 3.5-22Khz. we set a high pass cross over at 4.5Khz to give room for a 16db slope to roll off before we get near that 3.5Khz frequency range.  now say you turn the stereo up and get distortion on the tweeter during bass hits so you go into the EQ and drop the 20-120hz range by -6db and the tweeter no longer distorts.    my understanding was that a cross over should have taken ALL bass out of said signal before it its the tweeter. what would cause this type of situation to occur and would it be beneficial to have an EQ setup to -12db all frequency ranges outside of a speakers operating range in addition to a cross over?

 

 

edit: a second question for M5 (or anyone who can answer it) I was told that some artists are going back to vinal records as they produce more accurate sound than digital. now i know an MP3 cuts off lots of frequencies we cant hear and such but the way it was explained to me is that an MP3, WAV, AC3, any digital audio is not capable of producing multi stage harmonics that one would get with an analog music source such as a record or at a live concert the dynamics of the sound waves from the instrument projecting off various surfaces in the hall.    is there truth to this?

Edited February 20, 201411 yr by ncc74656

They are compressed, ie, data is crunched and finagled to be smaller. If you saw the difference in file size of lossless versus mp3 there's no question that a lot is lost.

i understand the MP3 to WAV but the point of the discussion i had was that no digital signal can accurately reproduce 2nd and 3rd harmonics. is that true?

is there any truth in that having a head unit that you can turn off its internal amplification can provide cleaner sound through its RCA's than a head unit with its internal amp remaining active?

You have them, listen to one in your shop and tell us.

i understand the MP3 to WAV but the point of the discussion i had was that no digital signal can accurately reproduce 2nd and 3rd harmonics. is that true?

No. There is no difference in signal response. Frequency response sure. They crop things significantly depending on the compression but this doesn't intrinsically mean it is lopping off harmonics.

ie, if you have a 25Hz note, harmonics of 50Hz, 75Hz, 100Hz, etc... It'll take a rather high order of harmonics if the compression lops things off at 10kHz. Of course the first harmonic of 5kHz is 10kHz so there the effect is different.

And please, stop believing in garbage and use your damn ears. I don't understand why this is so hard.

Google blind A/B testing. Then setup a jury test for yourself where you DO NOT KNOW anything about when what will be played. Let your ears decide.

I guarantee one thing here, when you do the test right you will be shocked at how much compression can occur before you notice. And please do cheat. Use some expensive headphones for the test.

my dog killed my set of headphones but my computer speakers are a yamaha 7.2 unit with some focused field model 600's and old school fisher 4 ways.  ill have to use that for now, the headphones i had were Technics RPDJ1200 and i thought they sounded great.

 

im not sure i have any head-units in my shop that we can turn off the amps on, maybe the DEH-80prs? (id have to look).  i was told that the internal amps will cause distortion and noise in high quality audio installs so decks with no built in amp should be sold OR decks that you can turn off the internal amp.

Land of educated people and culture and no car stereo shops, lol

Could have sworn you were talking about MD for a second.

You can on the 880 so I'd guess you can on the 80.

You don't NEED headphones it will just exaggerate the differences IF you can hear any.

when i finish reading bcae1.com i will play around with the a/b testing.  on the topic of bcae1 - can having 2 or more batteries each with their own separate ground to the body/frame/block cause a grounding loop? should the batteries have a common ground amongst them selves that THEN goes to body/block/frame or does it not matter?

Why would you do that?

why would i do which? have separate grounds or have a combination of grounds? ill start here: grounding loops are caused when a device has more than one path to ground and a difference in potential occurs between both grounds. every electrical component should have only 1 connection to ground to avoid this. the question comes in with the batteries, from factory each battery had its own ground to body/frame/block and i replaced these to their factory locations. if 2 batteries each have there own ground point can a grounding loop occur between them?

 

i was instructed that if possible all grounds should go to the same bolt to eliminate the ground loop noise issue. 

Edited February 20, 201411 yr by ncc74656

i am on the basics of car audio site and these is a link that plays a tone to show -1db drop on volume level. here is the link: http://bcae1.com/images/wavs/onedb.wav

 

I can not hear ANY change in volume level in this audio file, does anyone else?

i am on the basics of car audio site and these is a link that plays a tone to show -1db drop on volume level. here is the link: http://bcae1.com/images/wavs/onedb.wav

 

I can not hear ANY change in volume level in this audio file, does anyone else?

Which is one of the points we make here pretty regularly. A 1db difference is essentially inaudible, hell a 3db change would be hard to hear. So people picking pieces of equipment fretting about these small imperceptible changes is asinine. But it happens, all the time. Worry about the big stuff, don't sweat the small stuff you can't hear. People in this hobby worry too much about things they can't hear.

is there any truth in that having a head unit that you can turn off its internal amplification can provide cleaner sound through its RCA's than a head unit with its internal amp remaining active?

No. There would be no audible change. However, I do like it so that I don't have to worry about accidentally shorting out the unconnected yet still live speaker wires.

Has anyone used an EQ to help a cross over?

Have people done it before? Yes.

for example say we have a tweeter rated for 3.5-22Khz. we set a high pass cross over at 4.5Khz to give room for a 16db slope to roll off before we get near that 3.5Khz frequency range.  now say you turn the stereo up and get distortion on the tweeter during bass hits so you go into the EQ and drop the 20-120hz range by -6db and the tweeter no longer distorts.    my understanding was that a cross over should have taken ALL bass out of said signal before it its the tweeter. what would cause this type of situation to occur

Then your crossover is broke. If you had an 18db/oct crossover set at 4.5K, then electrically at 120hz it would be down 102db. Absolutely no chance adjusting the EQ at 120hz would affect the tweeter no matter how wide the Q of EQ as long as everything was working properly

would it be beneficial to have an EQ setup to -12db all frequency ranges outside of a speakers operating range in addition to a cross over

That would change the effective slope of the filter. So you could likewise and more easily just use a steeper slope on the crossover.

thats what i was thinking with the cross overs. i had a passive in line alpine filter that did next to nothing, if i had the volume at even 1/2 the tweeter had distortion if i was passing full to the mids. once i set it to a 500hz cross over it helped but when i was playing it loud i had to -5db the 100hz point to remove the distortion.  when i added KX3 it made a WORLD of difference as i bi amped at the same time but even having it bi amped with a KX3 i find that i can play it louder with out distortion if i have the 100-250hz down by -6db.  it just didnt make sense as to why i would need to do that and this KX3 is brand new from kicker as of 5 months ago.   its for this reason i am hessitant to buy a single EQ such as the KQ30 as im worried i wont have enough control. 

I just bought the 80 prs and yes you can turn off the internal amp. The only noticeable difference has been heat. Without the amp on it doesn't get so hot so fast. That's about it. Might I just add the the more you have to mess with, the more you have to mess up. Eq, slope, t/a and so on. It's incredible how much little changes affect everything.

To control the level of the signal, we use a potentiometer. A potentiometer (also know as a 'pot') is a resistor with a movable tap.

I understand what M5 meant now by "pot" EQ. is there anything bad about an eq that has dials on it? are the digital or slide ones better in some way?