Subs Out of Sync

[Loper23]

I just installed a new box for my friend. When I went to tune his amp for him, I noticed that his subs were moving out of sync, and one was moving a little bit faster than the other one. The subs are two Rockford P3's and the amp is a Rockford P1000-1bd. Both subs are dual-4 ohm wired down to 1 ohm. The box is a dual-chamber ported box tuned to 30hz. I've tried reversing the polarity of one of the speakers but that only put it further out of phase. They seem to be hitting alright, but I can't help but think that something's not right. Any suggestions?

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[garychoffmann 10+ year member]

Box layout? Ported/sealed? Custom/prefab? Coils read out correctly?

 

[Side Show 10+ year member]

check the load to the amp, if both subs are wired together they should move together. could even be one has more playtime and runs more freely than the other one. gotta vid?

 

[pickup1 5,000+ posts]

Are they out of phase?

 

[Loper23]

The box is a custom ported box with the subs facing the same direction and the ports in the middle separated by a divider. The area of each port is way too small (they are both the same, just not big enough), but I don't believe if that would make them hit different.

Subs are 4-ohm DVC wired down to 2-ohms each, one total. I haven't had a chance to check the impedance with my DMM but will next time I can.

I think that one of the subs is most likely damaged. He got the subs from a guy, who abused them pretty hard.

 

[Side Show 10+ year member]

well I'd say you just answer'd your own question..... check both coils on each sub seperatly with a dmm. worth checking the final load at the amp output first befor taking the subs out, something may have come loose inside the box and that could be your issue. goodluck

 

[gckless 5,000+ posts]

Ok, so unless you are hearing different tones on each one, one sub is not moving faster than the other. How exactly did you come to this conclusion?

 

[Loper23]

They look like one is moving faster than the other. I could see what looked like a speed difference because I was playing a 5hz sine wave. You can see that they are moving slightly out of sync on anything below about 40hz or so.

 

[Side Show 10+ year member]

vidz

 

[Jepalan]

Ohm out all four VCs separately (disconnect all from amp) - they should match pretty closely - if not, one is probably bad.

It was not clear from your description - do the subs share *any* airspace or are they in completely separate chambers?

 

[CrossoverOre 10+ year member]

theoretical possibility: one sub is newer than the other and the suspensions have different tensions. so one moves easier than the other.

But always test everything you can with a meter first to find out issues.

 

[Dimwit]

If the enclosure was custom made are you sure that both chambers ended up exactly the same? They could both be slightly different and that could cause the subs to react a little differently especially if one is older than the other. At least I would think

 

[gckless 5,000+ posts]

If they are going different speeds they will be playing different tones, period. Hz equals cycles per second. Unless they sound different, they aren't moving different speeds, it's just your eyes or the camera you watched them on playing tricks. Framerate is the common cause for cameras.

theoretical possibility: one sub is newer than the other and the suspensions have different tensions. so one moves easier than the other.
But always test everything you can with a meter first to find out issues.

Softer suspension and playing different tones are much different.

 

[CrossoverOre 10+ year member]

If they are going different speeds they will be playing different tones, period. Hz equals cycles per second. Unless they sound different, they aren't moving different speeds, it's just your eyes or the camera you watched them on playing tricks. Framerate is the common cause for cameras.


Softer suspension and playing different tones are much different.

true but I would be hard pressed to believe that some can visually determine that subs are playing different hz especially when they are connected to the same amp.

 

[gckless 5,000+ posts]

true but I would be hard pressed to believe that some can visually determine that subs are playing different hz especially when they are connected to the same amp.

Lol, that's what I've been saying.