Stupid Question?

[Anonymous 10+ year member]

I was just wanting to know, regarding ported boxes, will the sub closer to the port move more? Reason I ask is because when I had 2 15's I had the port in the middle and tuned the amps to within 1 AC volt of each other on every frequency and never had problems with one sub moving more. But now I have 2 18's and had to side port the box and it seems like the sub right on the port moves more than the one on the other side of the box, away from the port. I have triple checked my amps and they are within a volt of each other on every frequency, the biggest difference is around the tuning frequency, one amp reads 52.3 and the other reads 51.8-51.9, all the rest of the frequencies are right on. So I figure it has to be because the one sub is right on the port because they are getting the same power and same ohm load. Anyone know anything about this?

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[Anonymous 10+ year member]

any input would be nice. Thanks

 

[SSS 18734 5,000+ posts]

I've actually heard of this happening with some people's boxes. Depending on the location and size of the port, one driver can see more compression than the other. Although this could also be a product of your amp gains not being set equally. Can you chain the amps together via a slave/master switch?

 

[Immacomputer 10+ year member]

You have unequal loading on the subs. One sub is doing more work than the other around tuning because they're not loaded equally. Sounds like new box design time.

 

[Anonymous 10+ year member]

What do you mean by equally loaded? And the box is 46.5" W x 22.75" H. The port is 21.25" H x 8.5" W and is located on the drivers side. I could not fit the port in between the 2 subs and my battery tray was blocking the passenger side. So that is the only place I could put a port of that size.

 

[Anonymous 10+ year member]

I can strap the amps but they would be seeing .25 ohm a piece. And the amps are tuned as good as they are going to get. Worst case scenario one woofer is seeing 100 more watts and that is not even the one moving more.

 

[Anonymous 10+ year member]

This is a pic of my install. Other than one appearing to move more I have no complaints they are loud as hell

 

[Anonymous 10+ year member]

The sub right over the port is the one that moves more. I was thinking about building another box anyway, but only if I had too.

 

[SSS 18734 5,000+ posts]

A 21.25" x 8.5" port? That is enormous. What are you running and what are the rest of the dimensions of the box and port?

 

[Immacomputer 10+ year member]

What do you mean by equally loaded? And the box is 46.5" W x 22.75" H. The port is 21.25" H x 8.5" W and is located on the drivers side. I could not fit the port in between the 2 subs and my battery tray was blocking the passenger side. So that is the only place I could put a port of that size.

What I mean is that there is not equal pressure distribution in your enclosure. The two different subs are seeing different pressures behind them. This will most likely occur around tuning due to the intense pressure around those frequencies.

 

[IDSkoT 5,000+ posts]

I could not fit the port in between the 2 subs and my battery tray was blocking the passenger side. So that is the only place I could put a port of that size.

Re-locate the battery tray...?

 

[Acevolkov 10+ year member]

You might be able to replace that slot port with a aero port and maybe cut down on some port area. Play around with the design some, and maybe move the batteries if needed.

 

[Anonymous 10+ year member]

I was thinking about moving the batteries or even stacking them so I could use a slot port in between the subs. I do not really want to take any port area away because right now i have the perfect port area for a 40hz tuning. Internal Dimensions of Box are 21.25" H x 45" W x 25" D. Port is 21.25" H x 8.5" W. I do not want to make the enclosure any deeper unless I can use aeroports that will be equivalent to the port area I have now. I want to keep 12-14" from port to hatch. I guess I will have to move the batts around or work on some new box designs. My main question was that is it normal or to be expected for one to be working harder or is this a freak thing happening with my subs?

 

[Anonymous 10+ year member]

What I mean is that there is not equal pressure distribution in your enclosure. The two different subs are seeing different pressures behind them. This will most likely occur around tuning due to the intense pressure around those frequencies.

Does this seem to be the problem in my case, looking at the install?

 

[Immacomputer 10+ year member]

Does this seem to be the problem in my case, looking at the install?

If both coils read the same and if you put both subs on one amp (even if they're underpowered) and they still have this behavior, especially around tuning, then yes, I would say it would be the problem.