Testing Volts/Ohms

[LongThrow]

Put a DMM on my subs to make sure the ohms are wired correctly. Each sub tests about 3.6 being they are 4 ohm SVC. I test them wired to 2 ohm, And I'm getting 1.0-1.4 everytime I test. Is that okay?

When playing music, the ohms change, dramatically, constantly while music is playing. Is this normal? I assume it's likely not.

And if I follow ohms law correcty, with a 500w amp ran at 2 ohms, 500 x 2 = 1000. Square root of 1000 is 31.62. I set my gains to 31.62 on the meter, but it is INCREDIBLY clipping. I currently have it set by ear, and the maximum output on the gain I can get out of it without audible distortion/clipping shows 16 volts on my meter, forcing my gain on my amp to be at about 10% almost all the way down, on a 2.5v headunit volume set 28/35. Half the volts it "should" get.

What do?

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[Kangaroux 5,000+ posts]

Put a DMM on my subs to make sure the ohms are wired correctly. Each sub tests about 3.6 being they are 4 ohm SVC. I test them wired to 2 ohm, And I'm getting 1.0-1.4 everytime I test. Is that okay?
When playing music, the ohms change, dramatically, constantly while music is playing. Is this normal? I assume it's likely not.

And if I follow ohms law correcty, with a 500w amp ran at 2 ohms, 500 x 2 = 1000. Square root of 1000 is 31.62. I set my gains to 31.62 on the meter, but it is INCREDIBLY clipping. I currently have it set at what the meter shows as 16 volts, forcing my gain on my amp to be at about 10-15% Half the volts it "should" get.

What do?

The varying ohm load is known as impedance. Speakers are actually AC circuits. As the frequency changes, the resistance of this circuit changes as well (the circuit being the voice coil, which is what you test with your dmm). It's completely normal.

It's ok if a 4 ohm sub is reading a few tenths off but it should not be showing 1 ohm.

How do you know the amp is clipping?

 

[The_Quiet_One 10+ year member]

The ohms law you are using is for DC current. When you are dealing with AC current (speaker output) you have a phase angle which throws a wrench in your calculations.

It is normal for impedance to change while playing music. You have a lot of interesting electromagnetic concepts at play.

I would either set your gains with a high impedance piezo tweeter or see if someone close by has a o-scope/ SMD DD around you to help you out.

Added: What type of dmm are you using? Are you taking into account the resistance of the leads?

 

[The_Quiet_One 10+ year member]

All bass boosts and what not turned off? Also just to double check since it wasn't explicitly stated these readings are done while you're playing a sine wave?

 

[LongThrow]

The ohms law you are using is for DC current. When you are dealing with AC current (speaker output) you have a phase angle which throws a wrench in your calculations.
It is normal for impedance to change while playing music. You have a lot of interesting electromagnetic concepts at play.

I would either set your gains with a high impedance piezo tweeter or see if someone close by has a o-scope/ SMD DD around you to help you out.

Added: What type of dmm are you using? Are you taking into account the resistance of the leads?

No one has a detector or a o-scope, ******* are expensive

DMM I use. http://www.walmart.com/ip/14644665wmlspartner=wlpa&selectedSellerId=0&adid=22222222227008923747&wl0=&wl1=g&wl2=c&wl3=40839128552&wl4=&wl5=pla&wl6=55136637169&veh=sem

I'll read up on the gain setting method with the Piezo tweeter. So I should test the voice coil of the sub, not the leads where the sub wires to the terminals of the box?

 

[LongThrow]

All bass boosts and what not turned off? Also just to double check since it wasn't explicitly stated these readings are done while you're playing a sine wave?

Yes, Bass boost set to off, head units EQ flat, etc. Sub level on head unit is +15 (max) to get full voltage from RCAs (Correct?)

Sine wave at 40hz, and then tried with a 320kbps bitrate CD, playing normal low-bass music. Sine Wave seems to clip much sooner than my cd, playing normal music.

 

[LongThrow]

It's ok if a 4 ohm sub is reading a few tenths off but it should not be showing 1 ohm.

How do you know the amp is clipping?

The subs, indvudually, read 3.6. When wired to a 2 ohm load, they test 1.0-1.4

I know the amp is clipping, because the subs excursion becomes ridiculous and it's obviously clipping just by looking at the sub flex, and by listening to it.

 

[The_Quiet_One 10+ year member]

By leads I meant for leads for the DMM. When you turn them on just touch the leads to one another without touching anything else. They likely will read a couple tenths of a ohm that you need to substract from your readings. It will help determine if there is something funky going on. Link didn't work for me, but unless it's a pretty expensive DMM (as much as a cheap handheld o-scope) it's likely going to have some error.

 

[LongThrow]

By leads I meant for leads for the DMM. When you turn them on just touch the leads to one another without touching anything else. They likely will read a couple tenths of a ohm that you need to substract from your readings. It will help determine if there is something funky going on. Link didn't work for me, but unless it's a pretty expensive DMM (as much as a cheap handheld o-scope) it's likely going to have some error.

Yeah its a $10.00 walmart meter. Equus 3300 meter. I'll try touching the leads together tomorrow when the neighborhood isn't sleeping.

 

[wew lad 5,000+ posts]

unless you have an oscope set your gains by ear on your loudest song

the V=IR method is right to an extent but is better used to verify that your ears are correct by testing the voltage you get and seeing that its in the right range

 

---------- Post added at 12:08 AM ---------- Previous post was at 12:07 AM ----------

 

Yeah its a $10.00 walmart meter. Equus 3300 meter. I'll try touching the leads together tomorrow when the neighborhood isn't sleeping.

those meters are junk, mine would never read accurately. id get 18 ohms or 3 ohms or 8 ohms. it reads voltage pretty accurate but thats it

the oscopes many of us use are available for ~70$ btw

 

[The_Quiet_One 10+ year member]

Yes, Bass boost set to off, head units EQ flat, etc. Sub level on head unit is +15 (max) to get full voltage from RCAs (Correct?)
Sine wave at 40hz, and then tried with a 320kbps bitrate CD, playing normal low-bass music. Sine Wave seems to clip much sooner than my cd, playing normal music.

Maybe someone with experience using kenwoods can chime in. I've had Head units which you had to max out sub level to get full power from RCA and other who just used sub level as a bass boost. I don't know about your particular model. There is also a chance your HU's sub rca is clipping at that volume if you're using an earometer to detect distortion and it becomes apparent once you start rolling up the gain *shrug*.

 

[Kangaroux 5,000+ posts]

Awesome multi meter http://www.amazon.com/Etekcity-Auto-off-Multimeter-Voltmeter-Non-contact/dp/B00NW62L88/ref=sr_1_5?ie=UTF8&qid=1439611872&sr=8-5&keywords=etekcity+dmm

 

[LongThrow]

Maybe someone with experience using kenwoods can chime in. I've had Head units which you had to max out sub level to get full power from RCA and other who just used sub level as a bass boost. I don't know about your particular model. There is also a chance your HU is clipping at that volume if you're using an earometer to detect distortion and it becomes apparent once you start rolling up the gain *shrug*.

Hmmm.. I tried different volume levels, 26//35 which is 75%, some (I guess i shouldnt say most) head units should go up to 90% before clipping. So I set it to 28. And still have a bit of distortion with my gain set low.

What forumula should I use my AC voltage, testing my amp using 40hz tone, since there was a 'wrench throw into my calculations' lol ;p

 

[wew lad 5,000+ posts]

Maybe someone with experience using kenwoods can chime in. I've had Head units which you had to max out sub level to get full power from RCA and other who just used sub level as a bass boost. I don't know about your particular model. There is also a chance your HU's sub rca is clipping at that volume if you're using an earometer to detect distortion and it becomes apparent once you start rolling up the gain *shrug*.

im pretty sure any eq that uses 0 as neutral - i.e. it goes negative, should be set with the subw at 0. most headunit subw settings use 0 to a positive integer and they should be set with it maxed out. i.e. my jvc hu goes from 0 to 8, i set my gains with 8

 

[LongThrow]

Awesome multi meter Etekcity UT61A Manual / Auto Ranging Auto-off Digital Multimeter ( DMM ) Multi Tester Voltmeter Ammeter Ohmmeter with Non-contact Voltage Detector - AC / DC Voltage & Current, Resistance, Continuity, Diodes Tester, Relative Measurement - - Amazon.com

There's some cheap handheld o-scopes on the classifieds cheaper than that, I'd rather have a used portable o-scope at that price, but thanks!