Odd subwoofer "breathing" when sound stops should I be worried?

[gamehawk55 10+ year member]

Hey guys,

Had a quick question about an odd movement I've noticed my new subs do. My old JL 10W7 would do the same thing and just wondering if I should be worried or if it's normal.

OK so heres the deal. Today I got my SMD DD-1 and re-tuned my system with the 40hz @-5db tone. After tuning everything seemed fine. Next I wanted to use some test tones to see if I could find the aprox. tuning of my box (was designed by DC Creations and built by a friend). When using the -5db test tones, 30hz all the way to 40hz (10 seconds each). I noticed that when each track ended the subs would obviously stop but would notice an odd "breathing" effect. By that I mean I could see it slowly move out or in like 1-2mm. It's a very subtle movement but noticeable.

Now my question is this small amount of movement normal when a sub has suddenly stopped playing? Or when a sub stops should it come to an absolute hard stop dead center?

Is the "breathing" effect indicative of clipping? One shop guy saw my W7 do the same thing and said it might have been a small amount of DC getting to the subs?

By the way the subs I'm running now are 2 SA-8v2 D2's @2ohms on a Audison LrX 5.1k.

Just need to know if I should be worried or if it's normal cuz I don't have anything else to compare it to. If need be I can try and get a video of the subs doing the said movement tomorrow.

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[sbarber82 10+ year member]

My sa8v2s don't do this at all. You are picking up signal from something and it is getting to your sub.

 

[gamehawk55 10+ year member]

My sa8v2s don't do this at all. You are picking up signal from something and it is getting to your sub.

Well that doesn't make me feel much better lol. What do you think it could be? The Sub RCA's are nowhere near the power/ground wire. Power is ran up the center and RCA's are all in the passenger side kick panels. And actually I just remembered that the test tones I was playing were -3db but were played at volume 15 and I tuned my system to -5db with a max listening volume of 17. So even though I was using -3db tones after tuning it shouldn't have been causing clipping since the volume was lower.

 

[alexn09 10+ year member]

Sounds a lot like air pressure being released. When they are moving at power they have much more potential to create an imbalance of air pressure and then when they stop playing the suspension slowly equalizes pressures again.

Just a theory.

 

---------- Post added at 11:10 PM ---------- Previous post was at 11:09 PM ----------

 

Well I guess the obvious next question is ported or sealed? Because only a sealed chamber could have that affect.

 

[gamehawk55 10+ year member]

Sounds a lot like air pressure being released. When they are moving at power they have much more potential to create an imbalance of air pressure and then when they stop playing the suspension slowly equalizes pressures again.
Just a theory.

That's exactly what it looks like. But it's a ported box with a 2.5" wide port. Should it even be possible for that to happen? I've heard of people with sealed boxes pushing on the sub cone and having it slowly push back out. That's what this looks like when it suddenly stops. But only 1-2mm of movement. Very subtle.

 

[gamehawk55 10+ year member]

That's exactly what it looks like. But it's a ported box with a 2.5" wide port. Should it even be possible for that to happen? I've heard of people with sealed boxes pushing on the sub cone and having it slowly push back out. That's what this looks like when it suddenly stops. But only 1-2mm of movement. Very subtle.

Except for the fact that the subs were probably only moving at about half excursion during the test tones. Just judging by how far I've seen other peoples including mine move before.

 

[jdawg 5,000+ posts]

Sounds like either a ground loop or you need to turn on your ssf, theyre picking up 'garbage' in the recording maybe. Does it do or between tracks on a music disc? Mp3 player? Stock deck or aftermarket? Are your highs amped? Noise in those? Where is it grounded? Try moving your ground. It deff isn't normal. What amp? Cheap or bad rcas?

 

[Slo_Ride 5,000+ posts]

i say bad recording

 

[gamehawk55 10+ year member]

Sounds like either a ground loop or you need to turn on your ssf, theyre picking up 'garbage' in the recording maybe. Does it do or between tracks on a music disc? Mp3 player? Stock deck or aftermarket? Are your highs amped? Noise in those? Where is it grounded? Try moving your ground. It deff isn't normal. What amp? Cheap or bad rcas?

SSF is on 30hz. Not sure how to test for a ground loop?. If it makes any difference all my grounds on a DMM are 0.4ohms or less with the exception of one being 0.6ohms on the longest ground wire of my BIG 3. Resistance of amp ground to chassis is 0.0ohms. I will also notice this happen sometimes with a quick hard bass hit that has no resonance behind it.

I use my Ipod exclusively for music. Deck is a Kenwood DDX419 (see sig). Highs are not amped since I do not have aftermarket speakers yet (see sig)

Was playing the -3db tones off of USB stick. Tones were created online using a tone generator to make the -3db tones.

Tones used for tuning were on the SMD CD that came with the DD1.

Also I don't think the RCA's for the sub are cheapo ones. I bought them at a Local shop here and they are double or triple shielded type. THICK cord. I would say 6-8Gauge in size.

 

---------- Post added at 09:46 PM ---------- Previous post was at 09:45 PM ----------

 

i say bad recording

Bad recording of an online generated uncompressed sine wave? I somehow doubt that lol

 

[jdawg 5,000+ posts]

Does it do it on all tracks? I would say you could have bad rcas or you have a bad ipod cable, you are picking up noise somewhere, it could even be at the deck, time to narrow things down

 

[jdawg 5,000+ posts]

Nvm on the ipod cable, just seen you were using usb. It deff is something, if there is no music input they shouldn't move period

 

[gamehawk55 10+ year member]

Nvm on the ipod cable, just seen you were using usb. It deff is something, if there is no music input they shouldn't move period

It's not doing the "breathing" thing the whole time that there's no sound. Just right at the moment the sound of the test tone ends and the subs stop moving. Minus that half second of subtle "breathing" action. The subs do stop completely after that half second. Then the next test tone would start playing for 10s then the moment it cuts out, does the "breathing" for half a second. It's like the sub has stopped just off center and is slowly aligning itself back to center.

BTW these subs aren't even a month old.

 

[jdawg 5,000+ posts]

If its just that track and not after other tracks that are different songs or other albums I would say its that recording then

 

[MutantDreams 10+ year member]

The track might just end on the compression cycle. Then it would re align because of the spider to 0 xmax.

 

[Better-Action 10+ year member]

Sounds like something in the recording.