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multimeter help?
Tuesday, February 01, 2005 5:21 PM
alright, so i finally got around to buying a multimeter so i could set my gains correctly. but as it turns out, i've never actually used a multimeter. i'm a bit lost. i found out where i'm supposed to check the ohms, but which one do i use? it says 2000k, 200k, 20k, 2000, 200. i'm assuming 200? i tried checking my speakers ohm's, with 2000k, 200k, and 20k, i get nothing. with 2000 i get 6, and with 200 i get 6.6 on one speaker and 6.3 on the other(this one has been repaired). if i hook em up parallel, itr gives me 3(2000), or 3.5(200). i'm assuming i should just keep using 200? and why am i getting such high ohm ratings? my speakers are dual 2 ohms, wired in series i should be getting around 4 from one speaker and 2 from both of them parallel. am i doing something wrong?

also, how do i measure volts with this thing? i'm going to download the program and make a test cd with different frequencies so i can use it to set all my speakers, but foremore, which one should i use when i stet he gains...




Re: multimeter help?
Tuesday, February 01, 2005 5:35 PM
the difference between 200 and 2000 is how high resistance it can measure. on 2000 your getting 6 ohms because the meter can only read 4 or so digits at a time (where 2000 would be the top for that setting) when you switch to 200 it gives you more detail cause it can drop a digit past the decimal for yoru 6.6

if you turn it to say 20k, and get 6.6 that means your getting 6.6k ohms
to test voltage from yoru amps outputs put it on AC 200 for yoru low frequencies. its hard for amultimeter to read a changing voltage jumping from 1 to 50 ish at such a rate. at higher frequiencies you may switch to DC 200 or so ( don't know this for sure just play with it you wont mess yoru multimeter up at such low voltages)

as far as why your readings aren't matched. speaker manufacturers can't give you an exact number and several factors can change what resistance you have, such as condition/age, and temperture. also you'll notice if you touch your speaker and/or blow on it it'll change your resistance.



Re: multimeter help?
Tuesday, February 01, 2005 5:36 PM
You can't measure impedance with a multimeter because it's varies with frequency. You're measuring the resistance which is only one part of the impedance equation.

Impedance = Resistance + Inductive Reactance + Capacitive Reactance.

It gets even more complicated because inductive reactance is 90 degrees out of phase with resistance (lagging) and capacitive reactance is 90 degrees (leading).

Also, are you measuring at the speakers or at the amp? If you're measuring at the amp, the wiring is included in the measurement.

If you want to measure battery voltage, put the meter on DC (maybe a solid and dashed line). If you want to measure voltage at the speaker you need to measure AC voltage (symbol might be a sinewave).

Just to let you know. Auto-ranging multimeters are cheap and you don't have to mess with the settings when measuring resistance.
Re: multimeter help?
Tuesday, February 01, 2005 6:47 PM
????

now i'm really confused. all i wanna do is set my gains correctly instead of doing guess work... my old method was turning it up until i heard distort

i saw this post

"Set head unit volume to 3/4 of maximum. Turn off all eqs/presets in the head unit.

DISCONNECT SPEAKERS

P = Power in watts
I = Current in amperes
R = Resistance in ohms (effectively the nominal impedance)
V = Potential in volts (Voltage)

Knowns:
Resistance (nominal impedance of your speakers)
Power (desired wattage)

Unknowns:
Voltage (we'll measure this)
Current

Formulas:
P = I*V (formula for power)
V = I*R (Ohm's law)

So after a little substitution to get Voltage in terms of simply power and resistance we get

V = square_root(P*R)

So, for example, say you have a 4 ohm load presented to a 150 watt amp.

V = square_root(150*4) = 24.5 volts

This means you should increase the gain until you read 24.5 volts AC on the speaker outputs of your amplifier.

As a source, use a sine wave recorded at 0db at a frequency within the range you intend to amplify. You can generate tones in cool edit or use a program such as NCH tone generator. (credit for NCH to imtfox, IIRC and to Wysi Wyg)"



it says i can do it with a cheap multimeter... i thought it would be as simple as measuring my resistance, calculating how many volts i need, recording a cd for int frequency i want to amplify(30-60hrtz in my case.. or should i record something else?), and the turning the gain up until it reads 44.3 volts or whatever i need it to be.

and yes, i was checking at the amp terminals. whats this about the wire? should i take the speaker out of the box?



Re: multimeter help?
Tuesday, February 01, 2005 7:21 PM
the voltage you need to measure for setting your gains is on the speaker output of the amp...in AC volts.


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Re: multimeter help?
Wednesday, February 02, 2005 9:12 AM
AC 200 or AC 700? i'm assuming AC 200

anything else? what frequencies should i record for the sub amp? speakers amp? and why am i getting such high ohm ratings..?



Re: multimeter help?
Wednesday, February 02, 2005 9:22 AM
SomeGuy wrote:AC 200 or AC 700? i'm assuming AC 200

anything else? what frequencies should i record for the sub amp? speakers amp? and why am i getting such high ohm ratings..?

200....the voltage is prolly gonna be less then 50 im sure. and for your sub amp, i'd use maybe 100hz 0db test tone? for the amp driving your highs use 1khz 0db test tone. (make sure it's 0db, and not -3 or something like that)


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Re: multimeter help?
Wednesday, February 02, 2005 12:11 PM
alright, thanks.

any explanation for my ohms thing? why are they reading 3.5 togather? do i need to take the speakers out of the box and test them at the terminals?



Re: multimeter help?
Wednesday, February 02, 2005 12:21 PM
yea, that's probably because of the speaker wires and what not.


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Re: multimeter help?
Wednesday, February 02, 2005 5:24 PM
proabably because i had the speaker wires hooked up to the amp(even though it was off) too. stupid me. thanks man.



Re: multimeter help?
Wednesday, February 02, 2005 5:36 PM
i downloaded NCH tone generator and i'm lost...




Re: multimeter help?
Wednesday, February 02, 2005 6:17 PM
SomeGuy wrote:i downloaded NCH tone generator and i'm lost...

beh, just go out and pick up a bass cd with the test tones on it. save yourself the time and trouble of making your own.

i use bass mekanik's "POWER TOOLS" it's a double disc with every tone you could imagine, lol.




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Re: multimeter help?
Wednesday, February 02, 2005 6:18 PM
NCH owns. makes an excellent tool for finding resonant frequencies . lol

just load up 1 sine frequency and set it at 1k, set the duration to however long. and hit it

14.82 @ 97 mph
Re: multimeter help?
Wednesday, February 02, 2005 6:34 PM
i'm cheap, so i aint buying anything. lol.

left and right to 1000 and amplitude to 0db, correct? and thats my mids/highs amp test track. for my lows/woofer amp, record another track at 100 and amplitude at 0db again, right? those are the only 2 tracks i'll ever need..?



Re: multimeter help?
Wednesday, February 02, 2005 6:40 PM
my bad, but where do i set howl ong i want the track to be. and what do i save it as? wav?



Re: multimeter help?
Thursday, February 03, 2005 10:11 AM
One poster mentioned that the impedance of your speakers is a sum of the resistance, Capacitive Reactance and Inductive Reactance of your speakers. He is dead on with this one. As far as using the tones to set your amplifier gains, with the known Impedance of your speaker, this impedance should include the resistance of your wires, since they are part of the load that the amplifier will see. Any Crossovers should be included as well.

Since there is so much that goes into what you say you want to do, and even the best fluke multimeter will only tell you the direct voltage component, and the resitance value of a circuit, the best that you can hope for is to establish a base line setting value.

The best instrument most consumers can have, is their own hearing.

I start with picking my most dynamic CDs and the cream of the crop tracks on those. I turn the gains down all the way on the amplifiers, disconnect the rear and subwoofer inputs. Next I set the headunit to 3 levels below the maximum volume setting (my HU reads out in whole numbers from 0 to 35) and play the track that will excercise the mids ans highs the best. If I hear distortion, I turn the headunit down unitl it goes away. Now I will turn up the gains slowly to make the mids and highs just start to distort, then back off until it quits. I will then pause or mute the system and put in something that will excersice the subwoofer, while still working the mids and tweets and reconnect the subwoofer. Let the music play and turn the sub up to fill in the bass to my taste. Then Pause it again, connect the rear channels, and turn this up for my desired level of rear fill.
Finally I will check all of my musical setup tracks and adjust my system for the best overall performance. Sometimes I will go back and recheck a few tracks just to make sure I didn't destroy something with a recent adjustment. Once I am satisfied, I know that unless someone has done a home recording with too much emphasis, or turndown on something, my system can play anything for Bach's organ Music, to Opera, to Metallica, to Garth Brooks, to Dianna Krall.

My method is not a precise as what you want to do, but it will give me every bit as subjectively pleasing listen experience as your method given the tools you have, perhaps better.

There is a trick on reading the impeadance of a speaker set if it has a decent crossover. The R-component that you read for the set as it goes through the crossover, will never include the tweeter, since the low blocking component is a capacitor, and the component that disipates what you want blocked from the tweeter is a resistor. If you have a cheap crossover, there will only be a capacitor blocking the lows to the tweeter.
Re: multimeter help?
Thursday, February 03, 2005 11:42 AM
hmm...

well i'm not that good with the hearing trick. especially since some songs might be lower or higher than others. even measuing at the speaker terminals i'll get mixed numbers instead of the actual resistance?(havent tried yet..)



Re: multimeter help?
Thursday, February 03, 2005 12:09 PM
the speakers impendance is just an average...it's not going to stay the same because it varies while you play music.


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Re: multimeter help?
Thursday, February 03, 2005 12:41 PM
Do not use the DCR of the speaker to set the gains. If you do you will not be making use of your amp's full potential. Use the Nominal Impedance given by the speaker manufacturer. this is a rough average of the variable resistance that will be present to the amp.

Make sure you are using an RMS multimeter. Some display an average and some display peak.

DO NOT use NCH as its tones 12db down from where they are supposed to be. Proof:
http://www.sounddomain.com/memberpage/522583/7
The test was performed by me so I can 100% gaurantee it to be true
If you need tones I have them.

Set your head unit to the maximum volume you will ever listen to it.

Turn off all processing. (Crossovers, Equilizers)

Hook the multimeter up to the amp with the speaker disconnected and turn the gain up until you get the desired AC Voltage.

Do not turn the head unit up passed the current volume setting. Do not use any bass boost. Be careful with equilizer settings.

Also this test is ONLY if you are sure your amp makes rated power.



"all your bass are belong to us"
Re: multimeter help?
Thursday, February 03, 2005 12:43 PM
wysiwyg is absolutely correct.

As to songs that are higher/lower than others; are you talking about the volume level, or the frequencies. If it is volume level, to protect your system, use the loudest ones you've got.

The listening trick is aided by the sheer volume when you set your amplifiers. If your system starts to sound like @#$% you've turned the gain up to much, back off until it sounds good again.

When I set my system gains, I rarely turn it that high again intentionally, infact I typically listen backed off another 12 steps below where I set my system up at. The only reason I would put my system up that high after setting it, is if I changed some part of the system.

If you aren't confident in your own system, get a friend whose system you like and have him help you set it. For the first step tell him you want the most volume without distortion. When you adjust your subs tell him what kind of bass you want, and make sure it sounds decent to you while avoiding distortion. Finally work together to bring in your rear fill.

The thing with rear fill is, where do You, want the the sound to seem like it comes from? Does it come in from the front, or does it come in from the back? Does the sound surround you, or does it come from only one direction? I personally, have the sound in front, with enough fill in back to give the sound a bit more depth.
Re: multimeter help?
Thursday, February 03, 2005 2:18 PM
derf wrote:
If you need tones I have them.

Do not turn the head unit up passed the current volume setting. Do not use any bass boost. Be careful with equilizer settings.


1. SomeGuy4186@gmail.com if its not too much trouble. 100hz tone, and 1khz tone and i think thats all i'd need. thanks.

2. my RF amp has a bass knob. turn it up all the way before i set the gains.. so that its included in my max volume?




Re: multimeter help?
Thursday, February 03, 2005 2:29 PM
at the website, it says they're 2.2 ohms. use that? one of my voice coils was replaced not too long ago so i dont know if its the exact same thing, but i guess it'd be enough..



Re: multimeter help?
Thursday, February 03, 2005 3:06 PM
Link me to what sub you are using and I will help you.

How many subs do you have and how are they wired?


Do yourself a favor and do not use the bass boost. Using the bass boost when your gains are properly set with do 1 of two things.

1) you set the gains without the BB and then use it. It will clip the signal as you turn it up more and more and send too much power to the sub around the boost frequency (around 45hz)

2) you set the gains with the BB on and its exactly as loud as it would be if you didnt use it and you lose output as the boost slope drops around the boosted frequency.


I will send the tones when I get off work. If anyone else needs tones put your email up with what tone you need and I will email them to you.



"all your bass are belong to us"
Re: multimeter help?
Thursday, February 03, 2005 3:30 PM
yea, don't use the bass boost. everything needs to be off or in the default/flat setting.


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Re: multimeter help?
Thursday, February 03, 2005 5:26 PM
the thing with the bass boost is, in the morning i use the knob to remove most of the bass. when i'm driving in the morning i cant hear the words over the bass and i dont really wanna drive at 8 am with the music blasting either, so i turn the bass knob down to about 25%. in the afternoon, i like my music loud. so i turn it back up.. is it reallly that bad, cause i sorta like being able to control my bass on the fly. if i set my gains with the bass knob all the way, then i cant clip it cause i'll never be able to pass it, right? if its really that bad for my system though, i guess i could find a way to live with it.

i'm using these subs

http://www.audiopipe.com/TXX_specs.asp

the TXX-BC wires in series-parallel. my end result is 2 ohms, and i have that connected to a rockford 1000a2 in bridged mode

before anyone says anything, dont go off on my for using the amp bridged at 2 ohms. if i fry it its my own fault. i know alot of people that have done it with the same amp and they're amps have been like that for some time with no problems. i dont have the manual, and rf removed the specs from their site, but all the amps they have now can be bridged to 2 ohms and i'm assuming this one can too....

RF underates they're amps, so i'm not sure what the max rms is yet. it says 550x2@2ohms on the back, but i've read people with birthsheets that say 720 and 730. so i really cant tell you.

thanks for the help, i appriciate it



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