Anyhow I think I have alluded to what I'm planning else where around here but I thought I'd just put it out there.
I'm planning on using 2 x12" Exodus Shiva drivers in one smaller sealed box about 100litres+ approx.
Both these drivers will have their magnets facing each other,yes one cone facing forward the other back,sharing the same cabinet volume.
I've been told by some that this way I can get away with using smaller enclosures because somehow the drivers are tricked into acting like the box is bigger than it is, while others are telling me that I must simply double the box volume because I'm using two drivers.
I know this is what B+W with their small round subby and some others do.
But where does the truth lie?
Also will having a rearward facing driver have any detrimental effects??
Anyhow ontop of these boxes will sit my MTM's..
Sigh!
I'm planning on using 2 x12" Exodus Shiva drivers in one smaller sealed box about 100litres+ approx.
Both these drivers will have their magnets facing each other,yes one cone facing forward the other back,sharing the same cabinet volume.
I've been told by some that this way I can get away with using smaller enclosures because somehow the drivers are tricked into acting like the box is bigger than it is, while others are telling me that I must simply double the box volume because I'm using two drivers.
I know this is what B+W with their small round subby and some others do.
But where does the truth lie?
Also will having a rearward facing driver have any detrimental effects??
Anyhow ontop of these boxes will sit my MTM's..
Sigh!
Isobarik or Isobaric loading it's called. There are different ways of doing it and yes you can use two drivers in a box meant for one or even half that. ie: a box that's 1/2 the size of the normal box for one driver.
Here's another way of aligning the drivers, same result.
http://en.wikipedia.org/wiki/Isobaric_speakers
and the way you suggested, I think
http://www.members.shaw.ca/pferlow/isobarik_boxes.htm
Here's another way of aligning the drivers, same result.
http://en.wikipedia.org/wiki/Isobaric_speakers
and the way you suggested, I think
http://www.members.shaw.ca/pferlow/isobarik_boxes.htm
Isobaric loading is, or was, a method that reduced distortion when playing, although at the cost of two drivers. The Exodus Shiva-X drivers utilize XBL2 motors and already have somewhat reduced distortion. I'll offer some advice: Don't use isobaric loading, but instead build two subwoofers. Two woofers will produce the same SPL output as an isobaric with half the excursion. Lower excursion usually translates into reduced distortion levels. As an added bonus you can position two subs to curtail the nulls or eigenmodes that you will always have in any room.
In the old days, when Cal was young, they didn't have the really good subwoofer drivers like the original Shiva and later the Shiva-X and so isobaric loading was conceived as a method to have elevated levels of bass with somewhat reduced distortion. With the quality of the modern drivers (and Shiva-X is very good quality indeed!) isobaric loading is no longer needed. However, if reduced size is the main factor, then by all means go for it.
Best Regards,
TerryO
In the old days, when Cal was young, they didn't have the really good subwoofer drivers like the original Shiva and later the Shiva-X and so isobaric loading was conceived as a method to have elevated levels of bass with somewhat reduced distortion. With the quality of the modern drivers (and Shiva-X is very good quality indeed!) isobaric loading is no longer needed. However, if reduced size is the main factor, then by all means go for it.
Best Regards,
TerryO
Hi Joz, I think I know what you are talking about.
I have been told that when drivers are mounted front to back, sharing the same volume the box can be somewhat smaller than the normal.The one test box I built the shared volume was 90litres for a reasonable F3; using a calculator for a Qts of 0.8 with one woofer gave 30 litres, drivers do need to be in parallel tho.
Sound is omni-directional at these low frequencies
There is a thread, search for "Tardis" subwoofer
I have been told that when drivers are mounted front to back, sharing the same volume the box can be somewhat smaller than the normal.The one test box I built the shared volume was 90litres for a reasonable F3; using a calculator for a Qts of 0.8 with one woofer gave 30 litres, drivers do need to be in parallel tho.
Sound is omni-directional at these low frequencies
There is a thread, search for "Tardis" subwoofer
If you put 2 drivers in 1 box, you need to double the volume. (ie double the Vas, double the volume).
0ounting the drivers push-push and tightly coupling them will give you active vibration cancelation and you can get away with less actual box (you still need to make sure it is stiff enuff not to ballon (avoid MDF))
2 subs are usually better then 1, but i fell the advantages of push-push are significant So to me, 2 subs means 4 drivers (just got 4 Trio8 and 2 SDX10, that makes 3 subs -- this could get interesting)
0ounting the drivers push-push and tightly coupling them will give you active vibration cancelation and you can get away with less actual box (you still need to make sure it is stiff enuff not to ballon (avoid MDF))
2 subs are usually better then 1, but i fell the advantages of push-push are significant So to me, 2 subs means 4 drivers (just got 4 Trio8 and 2 SDX10, that makes 3 subs -- this could get interesting)
planet10 said:
Or not and use a LRT to electronically EQ it to the single driver's alignment which of course has its own set of trade-offs: http://sound.westhost.com/linkwitz-transform.htm
Not many 'free lunches' in audio design.
GM
Back again.
Anyhow with some further correspondance with my helper it has come about that I was a bit confused
So anyhow it seems that I will be going magnet to magnet in a push pull scenario.
Yes that makes sense even to me.I honestly thought it was push push...
Now back to investigating the best drivers for the job..
Again my apologies for any unnecesary confusion.
The 12" ShivaX's are in the running but it may be something else again.
Anyhow with some further correspondance with my helper it has come about that I was a bit confused
So anyhow it seems that I will be going magnet to magnet in a push pull scenario.
Yes that makes sense even to me.I honestly thought it was push push...
Now back to investigating the best drivers for the job..
Again my apologies for any unnecesary confusion.
The 12" ShivaX's are in the running but it may be something else again.
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