Anyone tried Isobaric (Clamshell method SPKR Mounting)

[Mega Heavy Bass 0]

Sorry it`s a JBL sub - But I do not have any MAG 12" Yet...

Anyway this will give you a good idea of what an ISO set up does.

The following text is taken from my Forum:

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O.K. Get ready because you are about to see one of the worse looking installs ever.

I`ve not bothered doing anything special because my boot space is regularly taken up with power tools / tools / bags of sand etc.

So there you go. No point in having a nice looking install that will get messed up within a few weeks.

Anyway what I did today whilst at work was...

...add another 12" JBL GT4 sub mounted onto the face of the other one that was already there.

This is known as Isobaric (clam shell method).

Here are the results.

Normal:

Peak= 135.3dB @ 46Hz

40Hz= 133.9dB

33Hz= 130.7dB

25Hz= 129.5dB

20Hz= 131.2dB

10Hz= 123.6dB

((((Ground Pounders)))) = 115.1dB

Total ((((Propper Droppers)))) Score = 129.2dB

Isobaric:

Peak= 134.8dB @ 33Hz

40Hz= 133.3dB

33Hz= 134.8dB

25Hz= 133.8dB

20Hz= 134.0dB

10Hz= 126.7dB

((((Ground Pounders)))) = 113.0dB

Total ((((Propper Droppers)))) Score = 130.4dB

;DI`m very impressed. ;D

So there`s actually a drop in Peak loudness. But overall the lower frequencies are much, much louder than before and over a flatter range too.

Notice how the peak frequency in Hz, has dropped so much. 46Hz down to 33Hz

It sounds mental now. So much louder by ear than it sounded before ;D

NOW JUST IMAGINE WHAT AN ISOBARIC WALL WOULD BE LIKE???

...And I`ve plenty of room to do it in my Escort ;D

[Mega Heavy Bass 0]

This method has worked very well in my Vectra.

I did not reduce the size of the box at all.

The box is 2.5 Cu.ft

4" Aeroport

Tuning to 27Hz

I guess it works well because of the following.

Having two drivers working parallel with each other in this way provides more control since you have two motor structures which have more control over the speakers movement. (It sounds better - transient response is very good)

Also having Two Cones & Two motor structures lowers the Fs of the subs - Naturally they drop lower but still keeping a very respectable loudness.

Now I`m thinking...

...In the same box I had a Mag12" (Not mine) - And that was hitting 140.5dB @ 46Hz

So with ISO mounting it should be around 138dB @ 33Hz - 137dB+ @ 20Hz - Now that`s quite LOUD for a very small boxed system & 1100wrms

[Adrian_D 520]

the way i understand it is that the vas of the iso group is half the vas of a single sub and that improves the low-end

[Tommythecat 0]

It doesn't change the Fs at all.

Read: http://www.soundsolutionsaudio.com/forum/i...?showtopic=9837

The small loss of efficiency/maximum output at high frequencies could be due to the woofers seeing a large box.

Edited July 8, 2007 by Tommythecat

[ramos 2]

Way back when ( late 70's through the early 90's ) , iso mounting was almost a necessity in small vehicles wanting multiple subs. Used to be quite popular actually . But not so much anymore with modern day low vas subs. If your going to run modern day high xmax subs in a push pull configuration . Better cut yourself a spacer to put between the subs. Cones don't like to hit anything while they are moving, especially another cone