Isobaric loading question

[Gazdatronik]

I would like to experiment with isobaric loading an old subwoofer that I happen to have a second identical driver for.

I know it's as easy as bolting the speaker fronts together, but will I have to also double the port length? I think I would have to, but there isn't a very clear answer in the various manuals I have read.

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[robgmn]

I would like to experiment with isobaric loading an old subwoofer that I happen to have a second identical driver for.

I know it's as easy as bolting the speaker fronts together, but will I have to also double the port length? I think I would have to, but there isn't a very clear answer in the various manuals I have read.

​

It's not quite as easy as that.
You have to reduce box volume by 50%; you have to make a spacer ring to separate the drivers and keep the surrounds from destroying each other; you'll have to recalculate your port for the change.
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL Port lenth 1.htm

 

[Gazdatronik]

So isobaric requires halving the box size to appropriately tune to a pair of given woofers.

It's not quite as easy as that.
You have to reduce box volume by 50%; you have to make a spacer ring to separate the drivers and keep the surrounds from destroying each other; you'll have to recalculate your port for the change.
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL Port lenth 1.htm

Shucks, I was hoping to grab an extra octave on the bottom end by doing this.

 

[robgmn]

So isobaric requires halving the box size to appropriately tune to a pair of given woofers.



Shucks, I was hoping to grab an extra octave on the bottom end by doing this.

Yeah, the benefit is usually smaller enclosure and better control / lower distortion (nature's method of Velodyne's feedback control. You can also see better power handling.

 

[Gazdatronik]

Yeah, the benefit is usually smaller enclosure and better control / lower distortion (nature's method of Velodyne's feedback control. You can also see better power handling.

But am i correct then in saying then that the frequency response would not change?

 

[robgmn]

But am i correct then in saying then that the frequency response would not change?

All things being equal, no.
You might be able to get away with using EQ to bump up the lower octaves a little, since the power handling might be slightly increased...

 

[Gazdatronik]

All things being equal, no.
You might be able to get away with using EQ to bump up the lower octaves a little, since the power handling might be slightly increased...

Damn. Well, thanks for the help, and saving me some wasted time, and from butchering up my sub.

Ah well. I guess my infinite baffle subwoofer project will be the way to go