jay427

Hi Everyone,
I am planning on tuning my system this weekend. JL Audio has suggested that I use a 50Hz and 2kHz test tone(s) for my tuning. I can't seem to find these downloadable anywhere. Can anybody point me in the right direction to create a CD to tune my system? Thanks!!

bullyx2

http://www.realmofexcursion.com/

click on downloads

jay427

Thanks bully!!! That's exactly what I need. Now I need to figure out if I should be using the 0db or -3db versions. Back to JL. Here's what they told me earlier for system setup as an FYI for you all:

Play the CD (speakers can be unhooked) at 3/4 volume (I'm assuming this is around 30 on the dial) and check the output voltages with everything flat.

Sub: 50Hz (not sure if I should us 0dB or -3dB signal)
output voltage should read a maximum of 38.7 V

Main: 2000Hz (not sure if I should us 0dB or -3dB signal)
output voltage should read a maximum of 17.3 V

This is what I'm planning on doing. Currently, I can detect slight distortion around volume=16 but no real tuning has been done on my part due to the horrendously cold weather that we're having up here in Massachusetts.

bullyx2

I did the 0db ones with the head unit and 30 and bass/treble flat. Make sure (especially on the sub) that you are looking for the voltage that applies to your subs impedence.

jay427

cool....thanks....I guess these specs are for 4 Ohm interior speakers and a 3 Ohm sub. I have 2 6 Ohm subs from 8 years ago showing a 3 Ohm load.

lensam69

Like Bully said, you have to use the 0db test tones with zero equalization and no sound enhancements.

I always recommend this article to people setting their gains, It's very informative, and the more you know, the better off you are:

What are gains and how to set them

Do the math twice when setting your gains.
It explains how to calculate your optimum voltage.

madmanmax3000

So when it says to test them using a voltmeter at the speaker outputs, does it just mean between two of the speaker terminals (+ and -) or should that voltage be the overall between the two sets of terminals.

For instance, 70W at 4ohm should be 16.7V at outputs, so would that be 8.35V at the left speaker output and 8.35V at the right speaker output, or would it be 16.7V for both?

Would it be a good idea to measure the impedance of the speakers directly? I know that they are stated to be 4ohm, but it is possible that they would be a little higher or lower? I've never come across a precisely 4ohm load before

Also, didn't know you were from MA Jay, you should definitely stop by a meet once it's nice out again, maybe my system will be done by then

jay427

I plan on measuring the impedance of the speakers before going through this excercise; especially the sub as I'm 90% sure that it will read 3 Ohms, but I could be wrong. It's about 8 years old and I don't quite remember how it's wired up. I also believe that this is per channel, so your front right should read 16.7 as should all other speakers. Basically, the voltage you want to measure is coming out of each output from the amp and measured between the + and - terminals for each output.

lensam69

Correct,

Unless you're planning on bridging the amp, then you measure (+) from one set and (-) from the other.

PhiSigBrotha

just used this method to adjust the gain on my alpine amp that runs my jl10w3v. damn what a difference. ive always kinda tuned by ear because i never new of a cheap technical way to do it. its louder and cleaner with a little more gain than i had it before and my head unit has bass at 0 and no bass boost used on the amp.


luther

lensam69

Good to hear Glad to help.

madmanmax3000

I tried to tune my amp using this method earlier with no luck. I had the amp on with a 2kHz test tone and couldnt read any volts between the speaker output terminals. Its a $35 multimeter I borrowed from a friend so that could very well be the problem. However i was able to read between the power and ground successfully.

I tried measuring both AC and DC, nothing over a volt came up, any ideas? Definitely a bad meter?

lensam69

Well, if the speakers are producing sound, then you're definitely doing something wrong...

Measurements should be done in AC Voltage. Some multimeters require you to plug the prong wires in different inputs, depending on what you'll meassure.

Also check to see that your range was set correctly (Make sure you're measuring in the 100's range, not 10's or 1's).

You can try it with any outlet in your house. Fiddle around with the AC Voltage settings until you get a 120V reading. (ONLY THE AC SETTINGS!!!! don't try to measure resistance on your outlet or you'll owe your friend 35 bucks). Once you find the correct setting head back out to the car.

madmanmax3000

You were right, wrong port on the meter. So I set the gains to the voltage they were supposed to be (16.7V) and it was incredibly loud! Even at "10" it was pretty deafening.

So I just turned the gains down to almost nothing and then it sounded proper again. This is not a particularly powerful amp (70Wx4 + 240x1). Is this normal? To get the voltage I needed the gains had to be turned up almost all the way. What do you recommend?

K25LOL

Also, if you have a laptop and line-in try SoundArb: http://slatecreekengineering.com/SoundArb.htm

mercman

A couple of pointers,

Never try to set the max voltage with a test tone with the speakers connected! This is very bad for your speakers and your hearing.

Next, Use a 0dB test tone that is in the range of the amp you are setting. Don’t try to set your sub with a 1khz tone.

Make sure your AC volt meter can read and is accurate at the frequency you are trying to measure. Not all DVMs can read a 1khz signal.

jeff

madmanmax3000

Is there any disadvantage to having the gains set lower than the maximum voltage other than lower volume?

It can't distort from being lower than needed, right?

Everything sounds loud and clean right now just setting by ear, and is way below the maximum voltage. I have each output at around 7V instead of the 16.7V I calculated as a max. Any reason to change it?

lensam69

Good call. I re-read what I posted, and it sounded like I was suggesting testing with the speakers connected.

What I was trying to say was that if the speakers produced sound when connected, then the amp was obviously working.

lensam69

Other than underusing the amp a bit, you shouldn't have any problems.
It sounded very loud because... well... 70W into efficient mid-high speakers will be loud . Multiply it by four speakers, and you've got yourself a pretty decent pounding.

If you're happy with what you have right now, I see no reason to change it. You should however leave a little bit of headroom so you don't find yourself turning the volume on the head unit all the way up.

madmanmax3000

Yeah, at this point I doubt I would ever need to turn it up above 30. At some point I may pick up an EQ and do some IASCA SQ competitions, but until then I'm perfectly happy underusing my amp a bit. Gotta preserve my hearing!

BTW my remote gain control is coming in today, hopefully I'll get it in and let you know how it is

jay427

Good Morning Everyone,
Well, I tuned the system over the weekend and may have run into a slight problem. See, I've had feelings that my subs might be bad due to age and 6-7 years of a lower-than-preferable amp hooked up to them. When I tested their impedance, it was bouncing, which I can't explain. What's strange though, is that they are 2 6Ohm subs wired to show a 3Ohm load, but the impedance that I was reading was anywhere between 4.8Ohms and 6.2 Ohms. Does anybody have any ideas about what this might be? I'm thinking that one of my drivers is toast, but without taking the box apart, that may be as far as I can get. Taking the box apart is the next step that I'm planning, but figured that I would post here to see if anybody has any ideas...thanks!

lensam69

Is you measured the impedance while it was playing, then it's ok to get those readings.

Impedance changes with the frequency that's being played.

DC resistance is what you measure when the sub is not connected to anything.

Is there anything wrong with the sound itself?

jay427

The impedance was measured before any other testing as to capture it for the equations. This was done to the sub enclosure with it disconnected. There was no source at all, and that's why it is so puzzling to me. Impedance, with no source, *should* be constant, and even more, it should be around 3 Ohms, not 4-6. It's very strange, and I believe that in order to figure this out, I'll need to take the box apart and test each individual driver.

lensam69

Don't rule out the possibility of a bad multimeter... Good Luck!


Edit:

Look on the bright side, At least the impedance is higher than expected, so you won't be burning up any amps...

mercman

Jay, you can’t measure impedance with a millimeter. All you can read is the DC resistance of the voice coil. Since the coil is suspended in a magnetic field and will move with the speaker cone you will see a changing resistance reading when measuring a voice coil of a large speaker. This is because sound waves cause the cone to move the voice coil in the field and that generates a small current. The current changes the ohm meter reading because the ohm meter is using small DC current to measure resistance. It is easier to see with an old analog VTVM (vacuum tube volt meter, I’m dating myself) but you can talk into the speaker and watch the meter move to your voice.

Impedance is made up of Resistance, Capacitive reactance and Inductive reactance. Without getting in to rocket science the reactance portions are dependent on frequency and phase angle. A speaker’s impedance would also include the loading on the cone and the resistance and impedance of any crossover components. Not a simple thing to calculate and not readable with a DC ohm meter.

You can compare the DC resistance of two like speakers a look for any gross anomalies but that’s about it.

jeff

jay427

Thanks Jeff,
I understand that the impedance measurement may be a bit off using my multimeter, but shouldn't it be lower than the range I specified? I have two 6 Ohm drivers that are supposed to be wired to produce a 3 Ohm load, but I was reading between ~5-6 Ohms. That's the part that scares me a bit...what do you think? When I measured each channel inside the car, I was a few tenths of an Ohm off from 4 Ohms, which was expected, but the subs are way off...

lensam69

I can see how that would do it. I guess a sensitive meter that uses a *very* small current for this measurement would be even more affected by it, but it feels like too big of a jump.

I'm pulling out my meter tomorrow and hooking it up to a sub, to see what jumps i get.

Jay, the only way to be 100% certain, is by opening the box, and checking each sub separately.

smazzurco

i have seen ppl/articles mention both a 1khz and 2khz test tone for speaker amps. I have an alpine pdx 4.100 hooked up to focal 169 vslim and mb quarts RCE269s.

Do you guys recomend i test with a 1k or 2k signal? or does it not even really matter? i was just gonna try both i guess...