Sub is reading 2-ohm on DMM but it's suppose to be 4-ohm

[302yota 10+ year member]

ok..my bad everyone...but i thought that whenever a (let's say) 4ohm load is bridged across a 2channel stereo amp...the resistance is cut in half, therefore the amp see's it as a 2ohm load...i must have been lied to...but if i'm incorrect please let me know

 

[gunz4me 10+ year member]

Well I got some news.... I finally decided to just take the sub out and figure out what model it actually is. Remember, I bought this setup on eBay for $150. It was for a JL Audio 300/2 and a 12W0-4. However, I noticed that the sub didn't have a round cone, but it was flat. So I didn't really believe that it was a W0.
Anyway, when I took the sub out the first thing I noticed was that there were 2 VC's! I flipped over the sub and I just happened to receive a JL Audio 12W3V2-2. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

It turns out, the reason I was only getting a 2-ohm load was because they only had one VC wired up. ????

I checked both VC's and they both read about 2.3-2.5 ohm. I rewired the sub and now the final load is 4-ohm.

I will install it tomorrow and see how the 4-ohm load sounds bridged on the 300/2.

Now, I am thinking of put this amp on eBay and getting a 500/1 amp. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Wow, that is pretty good for $150 assuming everything works properly //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[gunz4me 10+ year member]

ok..my bad everyone...but i thought that whenever a (let's say) 4ohm load is bridged across a 2channel stereo amp...the resistance is cut in half, therefore the amp see's it as a 2ohm load...i must have been lied to...but if i'm incorrect please let me know

The only difference here is we are talking about a JL Audio amp that has a highly regulated power supply. In mono, it will give 300 watts between 3 and 8 ohms. In stereo, it will produce 150 watts per channel between 1.5 and 4 ohms.

Other than that, I think you are correct when looking at the final bridged mono load regarding most car audio amplifiers. If the final bridged load is 4 ohms, each channel when summed together to combine outputs sees it as 2 ohms per channel. This is generally due to the fact that when you connect a load across each of the amplifiers channels, each channel will see 1/2 the resistance due to the fact that the load is balanced across both of those channels. I know the explanation is redundant, but that is how I have always been taught. It also explains the reasoning that old school class A/B amplifiers were 2 ohm stereo stable and 4 ohm mono stable, except for a couple of my Orions

 

[302yota 10+ year member]

so in other words...what i have been saying is true?...btw on my cruch 1000wt amp it has a switch for the amp to be mono or stereo...what's the purpose in using this...if i have the amp brigded?

 

[gunz4me 10+ year member]

so in other words...what i have been saying is true?...btw on my cruch 1000wt amp it has a switch for the amp to be mono or stereo...what's the purpose in using this...if i have the amp brigded?

Yep, what you are saying is pretty much true, with some rare exceptions.

As for that switch on your amp, that is where life begins to get tricky! Some amps, when you flip that switch, it disables one of the channels on the input as well as doing something funky with the power supply. It can do a multitude of things from summing the inputs to putting the power supply in high power or high current mode or inflating *** Bomb Annie!

It could be worse though... To bridge my Linear Power 1752, you have to pull off the bottom cover, switch the power taps to 2 ohm, and flip a switch to convert the inputs from stereo to mono. I should post a guts shot to show you 1980s technology at its finest BRB, going to find the photos.....

 

[302yota 10+ year member]

wow....so should i leave the switch on mono or stereo?

 

[gunz4me 10+ year member]

If your amp is bridged, you should have that switch set to mono.

 

[DidUHearThat? 10+ year member]

This thread is full of fail.