Isobaric Cab Designs - Downfalls?

[tbassist4]

Hey everyone,
The whole notion of an Iso-barik 15" speaker cabinet has been on my mind lately. I know little about how isobaric configurations sound compared to regular configurations, but I was still wondering why they're rarely used.

I understand that they're less efficient, thus requiring more power, and that they cost more since you need to buy two drivers, but with a 50% reduction in cab size for the ideal dimensions (meaning you can now have a "perfect" 15" cab), doesn't that potentially make up for the downsides?

[will33]

Originally Posted by tbassist4

Hey everyone,
but with a 50% reduction in cab size for the ideal dimensions (meaning you can now have a "perfect" 15" cab), doesn't that potentially make up for the downsides?

Nope, wood is cheaper than speakers. Also, due to the design you'll need at least a 2-way crossover and another speaker to play the mids (tone), that adds more parts and another speaker into the equation. So, isobaric is a good way to get high output, but not across the entire frequency band you need even for a bass guitar, ie: not tweeters. Count up the doubled driver cost and the other stuff involved, it's much cheaper to stuff some "regular" speakers in a box and sell it, especially since people keep buying them that way.

[billfitzmaurice]

Originally Posted by tbassist4

with a 50% reduction in cab size for the ideal dimensions (meaning you can now have a "perfect" 15" cab), doesn't that potentially make up for the downsides?

It did in the heyday of isobarics 30 years ago, when getting high output to low frequencies could require a 20 cubic foot cab, so getting the same output from a 10 cubic foot cab might make the doubled driver cost a worthwhile trade off. Since there's an abundance of drivers today capable of doing in 2 cubic feet what once took 20 cubic feet the concept has lost a bit of its appeal.

[Eublet]

Originally Posted by billfitzmaurice

It did in the heyday of isobarics 30 years ago, when getting high output to low frequencies could require a 20 cubic foot cab, so getting the same output from a 10 cubic foot cab might make the doubled driver cost a worthwhile trade off. Since there's an abundance of drivers today capable of doing in 2 cubic feet what once took 20 cubic feet the concept has lost a bit of its appeal.

But wouldn't the same concept still apply, meaning that they can still cram two more drivers into a similarly sized box and get more output than with a single driver?

[will33]

More output in the lows, but they already have enough. Not more output across the entire bandwidth.

[walterw]

my impression of trying out the isobaric orange cab with the two 10s (one of them "hidden") bears out what the theory suggests: you get the low end of two 10s but only the overall volume output of one.

[GCool]

If it's not a sealed cab or an old horn cab it's not for bass!

[KJung]

Originally Posted by walterw

my impression of trying out the isobaric orange cab with the two 10s (one of them "hidden") bears out what the theory suggests: you get the low end of two 10s but only the overall volume output of one.

I'm surely no expert at this, but 'more low end' does mean more volume (for those low frequencies). I guess it just depends where you want the extra db's. It does seem like a relatively outdated design, given that there are some pretty amazing neo drivers available that can produce a lot of low end in a relatively small box with a single driver, but who knows.

[GCool]

Originally Posted by walterw

my impression of trying out the isobaric orange cab with the two 10s (one of them "hidden") bears out what the theory suggests: you get the low end of two 10s but only the overall volume output of one.

When I went to summer NAMM in 08 I ran in the Orange guys. Now I have never played Orange at that time. So I plugged in all the new stuff. The 1st one I tried is the sp210, I have to say it sucked just to put it nice. Then switched the speaker cable and played the sp212 and once again it sucked. But when I plugged in the sp410 that thing came alive. Ever sense then I was hooked. I did a bun of A-B test with my sp410 cab vs. an aggy db410 I had at the time. For me the sp410 was the way to go from rick full sound to the spl that the cab cranked and it was small perfect for some one who giggs a lot and had to carry there own gear!
I know this is not new technology here but there is nothing new about a sealed cabs ether...

Now I will say this don't take it from me because I will hear about the endorsed crap blaa blaa.. Try one for your self.

[AlexanderB]

Basically you put two motors (electromagnetical drives) to a cone with the same area and twice the mass of the original one. That renders a speaker system with equal maximum (if excursion limited) output and bass extension, but in half the box volume. It needs twice the power to get as loud as its conventional counterpart. If woofers are facing each other, you will also reduce distortion a lot. (Which is not always something you want to do for musical intruments.)

The advantages are best used for true LF applications, such as touring concert sub woofers, hifi and home cinema subs where WAF only allows for small enclosures.

With todays high-xmax woofers, cheap amps and processors, one can still use rather compact cabinets and EQ them to go deep in the bass.

[PDGood]

Originally Posted by billfitzmaurice

It did in the heyday of isobarics 30 years ago, when getting high output to low frequencies could require a 20 cubic foot cab, so getting the same output from a 10 cubic foot cab might make the doubled driver cost a worthwhile trade off. Since there's an abundance of drivers today capable of doing in 2 cubic feet what once took 20 cubic feet the concept has lost a bit of its appeal.

I don't mean to hijack this thread, but this seems like the perfect time to ask this question: Just what exactly has made this advance in technology possible? I've been shocked at how much better cabinets sound now than they did when I last bought one years ago. What's been the biggest improvement - better speaker design? Better cabinet design? Other?

KJung or anyone, what is a good 10" neo that produces bottom end well?

Sorry for the brief interruption.

[AlexanderB]

The paradigm shift was not in the speakers - technology has been there since Cerwin Vega launched the 18" Stroker woofer for PA. It has a 9 mm X max (which was basically unheard of by then) and was desigend for and used with the movie "Earthquake" in 1975. Cerwin Vega even achieved an Academy Award ("Oscar") for developing the "Sensurround" audio system.

The change has been in amplifiers, where amps now can be said to be five times as powerful, better sounding, half the wight or less for the same price, compared to scenario 10 or 15 years ago.

Now the average bass player can easily get his hands on 1000W+ amps for very decent prices. That allows speaker designer to trade speaker sensitivity for bass extension.

[billfitzmaurice]

Originally Posted by Eublet

they can still cram two more drivers into a similarly sized box and get more output than with a single driver?

They're not. Two drivers in an isobaric alignment deliver the same output as one driver in a standard alignment. All that differs is the size of the box.

I don't mean to hijack this thread, but this seems like the perfect time to ask this question: Just what exactly has made this advance in technology possible?

T/S specs. Prior to them all drivers and cabs were empirically designed, i.e., 'seat of the pants'.

[rpsands]

Originally Posted by AlexanderB

The paradigm shift was not in the speakers - technology has been there since Cerwin Vega launched the 18" Stroker woofer for PA. It has a 9 mm X max (which was basically unheard of by then) and was desigend for and used with the movie "Earthquake" in 1975. Cerwin Vega even achieved an Academy Award ("Oscar") for developing the "Sensurround" audio system.

The change has been in amplifiers, where amps now can be said to be five times as powerful, better sounding, half the wight or less for the same price, compared to scenario 10 or 15 years ago.

Now the average bass player can easily get his hands on 1000W+ amps for very decent prices. That allows speaker designer to trade speaker sensitivity for bass extension.

I am pretty sure there is more to it than that; getting a woofer with a low vas, huge Xmax, and high enough Q to go down that low in a small box is not something they were doing 20 years ago (AFAIK).

I believe there's also been some significant changes in what TS specs are reasonably achievable based on neo magnet strength but couldn't speak to any specifics; just parrotin stuff I've heard bill and agedhorse say

[AlexanderB]

Interesting points, rpsands.
But there has been strong motors for decades too, although mostly for horn speaker transducers with low Q and moderate X max.

High Q is not necessarily all that good. Especially when it nowadays is so easy to use a low Q transducer in an EBS (extended bass shelf) box. That type of box is "lean" in the bass but goes deep. A bit of EQ will restore the reduced level in the lowest octave and yield a box that is compact, goes low but at the expense of sensitivity.

One inherent problem with this type of powerful motor woofers is the high inductance from the massive voice coil, which degrades midrange performance.

[billfitzmaurice]

Originally Posted by AlexanderB

One inherent problem with this type of powerful motor woofers is the high inductance from the massive voice coil, which degrades midrange performance.

Today's motors are no more powerful than that of the JBL D130, circa 1949. What makes today's drivers able to work in far smaller enclosures is all the other specs, which, aside from Fs, were unknown in 1949. Or 1969 for that matter. And since drivers tend to stay in the manufacturer's inventory for about ten years it was 1980 before drivers designed with T/S specs considered became common, 1990 before they dominated the market, and 2005 before the widespread use of neo magnets allowed transducer engineers to create drivers that they'd previously only dreamed of.

[AlexanderB]

The inductance of the D 130 is 0,8 mH according to the jblpro home page.
The not very new JBL 2242 has an inductance of 1,2 mH. Ciare's most powerful woofers are about 1,5 mH. That will affect mid/hf response.

[billfitzmaurice]

Originally Posted by AlexanderB

The inductance of the D 130 is 0,8 mH according to the jblpro home page.
The not very new JBL 2242 has an inductance of 1,2 mH. Ciare's most powerful woofers are about 1,5 mH. That will affect mid/hf response.

The D130 was a full range driver, intended to be used for hi-fi, perhaps with a tweeter. Perhaps, because in 1949 there was no FM radio, and 78s were the main source of recorded sound, so 5kHz was acceptable bandwidth. Le was minimized to allow it to go that high. Today's sub woofers typically have Le values 1.5 mH and higher because they're only run to perhaps 100 Hz.