going through alot of different designs in my mind, i have 6 subs ready to go in..recently i was thinking about doing 3 iso pairs.
whats the downfalls of iso?
which do you think woud be louder 6 normal subs, or 3 iso pairs?
both would be in the optimum enclosures...im trying to figure out if the extra motor force from the iso's would be beneficial in any way other than a smaller enclosure.
thanx
whats the downfalls of iso?
which do you think woud be louder 6 normal subs, or 3 iso pairs?
both would be in the optimum enclosures...im trying to figure out if the extra motor force from the iso's would be beneficial in any way other than a smaller enclosure.
thanx
Isobaric is good for small drivers. It lowers the Fs.
For example: you have an 8" sub with Fs of 50Hz, for an iso setup
with 2 of the same 8" drivers, multiply the Fs by .707... so your new
Fs is 35.35 for the same enclosure volume.
Or, you could reduce the enclosure volume when using the iso setup.
I'm not an expert and never built any speaker cabs that were iso, but
I read something about them on wikipedia.
For example: you have an 8" sub with Fs of 50Hz, for an iso setup
with 2 of the same 8" drivers, multiply the Fs by .707... so your new
Fs is 35.35 for the same enclosure volume.
Or, you could reduce the enclosure volume when using the iso setup.
I'm not an expert and never built any speaker cabs that were iso, but
I read something about them on wikipedia.
/sreten.isobaric is 6dB quieter than a single driver for the same power input, ofcourse, the isobaric has two speakers working as one, so you can give it twice the power, meaning its only 3dB quieter.
having said that, SIX woofers in a "normal" box will need four times the box volume that an isobaric enclosure with three pairs would need...
and three pairs of speakers in an isobaric setup would be 9dB less efficient than the same six woofers in a normal box, and would still only handle the same power.
having said that, SIX woofers in a "normal" box will need four times the box volume that an isobaric enclosure with three pairs would need...
and three pairs of speakers in an isobaric setup would be 9dB less efficient than the same six woofers in a normal box, and would still only handle the same power.
TWOJZ said:
You can get the same FR using something like a linkwitz transform, but you need more power and you use up excursion much more quickly so the EQed speaker is going to be much more strained... better i think to solve the problem acoustically than electronically.
dave
PS: one thing that doesn't get mentioned is that with isobarik you have 2 cones for any reflections to get back thru the cone, so an isobarilk can sound less boxy.
planet10 said:
it was, but the point is still valid...
lets assume we want a good solid response down to 30Hz, from a 12inch sub...
now, the sub I'm looking at, in 50 litres, tuned to 30Hz, will be -2.6dB at 30Hz....
half the enclosure volume to 25 litres, still tuned to 30Hz, and now you have -7.7dB at 30Hz
this is what I found in some pocket book which came with blaupunkt subwoofer:
"Increasing in popularity in recent years is the compound woofer design, more commonly known as the "Isobaric" design. Isobaric actualy means "constant pressure" which is the case having two woofers moving an encapsulated pocket of air between them in the same direction. This arrangement acts like a single speaker which effectively reduces the required box volumes for a subwoofer system by 50% which is substantial if you are space limited. Unfortunately, the trade off for space is the 3 dB loss in efficiency but this is usually recovered with the increased amplifier power. Care must be taken to avoid air leaks between the two woofers and final speaker wiring and impedance loads must be carefully watched. "
one more thing, you do have only -3dB loss, but remember, you reach the same lower fr response with half the box volume with the same excursion, even you have the same cone area, you have twice the magnet power, so its the speakers with twice the motor
aaah, one more final thing, when you have two woofers acting as one, lets say each 8 ohm, you will most likely wire them in paralel to obtain 4 ohms, which giver you higher loudness as one single 8 ohm speaker (I know I am not comparing to 4 ohm now), but by reducing the impedance you are back to the same efficiency...
I have done some isobaric subwoofers in the past, especialy the one "monolith" which was made out of single concrete monoblock, with two isobaric pairs, that was one of the best subwoofers I ever made
unfortunately I had to leave it behing....
"Increasing in popularity in recent years is the compound woofer design, more commonly known as the "Isobaric" design. Isobaric actualy means "constant pressure" which is the case having two woofers moving an encapsulated pocket of air between them in the same direction. This arrangement acts like a single speaker which effectively reduces the required box volumes for a subwoofer system by 50% which is substantial if you are space limited. Unfortunately, the trade off for space is the 3 dB loss in efficiency but this is usually recovered with the increased amplifier power. Care must be taken to avoid air leaks between the two woofers and final speaker wiring and impedance loads must be carefully watched. "
one more thing, you do have only -3dB loss, but remember, you reach the same lower fr response with half the box volume with the same excursion, even you have the same cone area, you have twice the magnet power, so its the speakers with twice the motor
aaah, one more final thing, when you have two woofers acting as one, lets say each 8 ohm, you will most likely wire them in paralel to obtain 4 ohms, which giver you higher loudness as one single 8 ohm speaker (I know I am not comparing to 4 ohm now), but by reducing the impedance you are back to the same efficiency...
I have done some isobaric subwoofers in the past, especialy the one "monolith" which was made out of single concrete monoblock, with two isobaric pairs, that was one of the best subwoofers I ever made
unfortunately I had to leave it behing....
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