I've been drooling over the speakers from Eggleston Works lately and noticed that they use a lot of isobaric loading in their designs. I've been reading up on isobaric loading and since I haven't seen it on many other high end designs I'm wondering what advantages it would provide in this application?
"The Ivy Signature is impressive to behold. On the baffle, there are eight (8) drive units visible, but there is more. Behind each of the 6” midrange drivers is two more drivers mounted in isobaric configuration. Similarly, behind each of the 12” woofers is another 12” driver. The result of this unusual use of isobaric loading is a speaker that reproduces music in an effortless and completely truthful manner that has an almost spooky realism." The Ivy Signature - EgglestonWorks – Quality Loudspeakers
I've been looking into the science behind isobaric loading and I don't know how it relates to their claims of "effortless and completely truthful" sound. Their cabinets already appear quite large, but maybe they are using it to further lower the frequency response (effectively doubling the volume for each radiating sub). Does the reduction of backpressure on the radiating driver have much of an effect on distortion?
The mids make even less sense, they are triple loading each mid isobarically? I've never heard of any triple isobarically loaded designs before. According to other sources (EgglestonWorks Ivy Signature - Krispy Audio) the mids are mouted front to back (3-each) into 4 individually tuned transmission lines. Does this mean that each transmission line is tuned to different frequencies, or just that there are 4 separate t-lines? I could see how that might work to flatten out the response curve, but haven't seen differently tuned ports on anything else.
Or are they just doing all this so they can jack the price up, gotta get that price up to $100,000 a pair somehow?
"The Ivy Signature is impressive to behold. On the baffle, there are eight (8) drive units visible, but there is more. Behind each of the 6” midrange drivers is two more drivers mounted in isobaric configuration. Similarly, behind each of the 12” woofers is another 12” driver. The result of this unusual use of isobaric loading is a speaker that reproduces music in an effortless and completely truthful manner that has an almost spooky realism." The Ivy Signature - EgglestonWorks – Quality Loudspeakers
I've been looking into the science behind isobaric loading and I don't know how it relates to their claims of "effortless and completely truthful" sound. Their cabinets already appear quite large, but maybe they are using it to further lower the frequency response (effectively doubling the volume for each radiating sub). Does the reduction of backpressure on the radiating driver have much of an effect on distortion?
The mids make even less sense, they are triple loading each mid isobarically? I've never heard of any triple isobarically loaded designs before. According to other sources (EgglestonWorks Ivy Signature - Krispy Audio) the mids are mouted front to back (3-each) into 4 individually tuned transmission lines. Does this mean that each transmission line is tuned to different frequencies, or just that there are 4 separate t-lines? I could see how that might work to flatten out the response curve, but haven't seen differently tuned ports on anything else.
Or are they just doing all this so they can jack the price up, gotta get that price up to $100,000 a pair somehow?
When used back to back with the motor and suspension working the other way, some harmonic distortion is reduced. The drivers are also not pushing against the cabinet as much, they mostly push against each other.
Some builders used to say the rear drivers give a barrier to sound coming back through the cones.
Some builders used to say the rear drivers give a barrier to sound coming back through the cones.
Apparently the mids are mounted front to back, and I would suspect based on the cabinet size that the subs are as well. I'm thinking it probably has more to do with the direct radiating driver acting like it's in free air, while still maintaining a ported cabinet to augment the low end. The triple loaded mids still seems a bit excessive though, but I guess that's the goal of a $100,000/pr set of speakers.
I added up the likely drivers on partsexpress and came out to ~$9k, so the cost seems fairly reasonable for a commercial product after you add in the cost of crossovers and the cabinets.
I added up the likely drivers on partsexpress and came out to ~$9k, so the cost seems fairly reasonable for a commercial product after you add in the cost of crossovers and the cabinets.
I like using cheap drivers in isobaric setups. Cheap drivers tend to have low power handling and high VAS. Going isobaric reduces the VAS by half, and doubles the power handling.
I know a lot of people complain that this is a waste; when you go isobaric your efficiency drops by 3dB. But the thing that they miss is that efficiency is (fairly) irrelevant at low frequency, where displacement and power handling mostly dictate how much output you can generate.
I'd have a hard time getting excited about isobaric for more expensive drivers though; you reach a point where the reduction in enclosure size is outweighed by the sheer volume of the driver.
I know a lot of people complain that this is a waste; when you go isobaric your efficiency drops by 3dB. But the thing that they miss is that efficiency is (fairly) irrelevant at low frequency, where displacement and power handling mostly dictate how much output you can generate.
I'd have a hard time getting excited about isobaric for more expensive drivers though; you reach a point where the reduction in enclosure size is outweighed by the sheer volume of the driver.
I guess I can see how using isobaric loading would let them double the motor force of the subs to help achieve that -4dB@14hz output, and people buying these are not worried about efficiency since they can afford the extra drivers and giant amps.
Does isobaric loading affect port length? They must be tuning quite low to achieve that 14hz output, and those boxes don't look very big for 12s (especially considering the extra space taken up by the iso loading), I imagine the port must be pretty long, maybe it coils around inside.
I'm pretty sure they are using Morel Supreme series drivers, which are pretty nice to begin with, but I guess if you've got the money why not?
Generally not the case in an isobarik where they need to be acoustically in phase. It is possible to create a push-push isobarik but the contortions you have to go thru no doubt bring other issues.
In general, isobarik mids are not a good idea as you get ripple in the response related to the depth of the isobarik coupling cavity.
In the bass the primary benefit of isobarik is ~halving the required volume for the same response.
To paraphrase Sreten: with all the woofers available today, just choose a woofer that better satisfies your volume requirements.
I do have the suspicion that isobarik can provide a benefit of isolating the radiating driver from the inside of the box which may reduce colourations.
dave
I have successfully used isobaric for midbass (in clam configuration) not only to reduce required volume to half, but to simplify the crossover, as the backside of the midbass has natural roll off and significantly lowered breakup.
And long time ago I built many isobaric subs to make them smaller...but that was long time ago, now i am more into open baffle.
And long time ago I built many isobaric subs to make them smaller...but that was long time ago, now i am more into open baffle.
Box tuning (Fb) is a Helmholtz resonance determined by the enclosed volume size, port area and depth, the type of driver(s) used has no effect on Fb.
I'm not even clear what Isobaric loading is all about.
Something to do with one woofer mounted behind another in a closed box.
It's probably a better way to do things than the classic parallel MTM.
I never like that one. It has an out-of-phase rocking motion that gets the woofers moving in different directions. Push one woofer in, the other moves out. Phase and lobing nightmare. 😕
Think about it. Parallel MTM doesn't give the amplifier any damping control over an out-of-phase motion in a shared enclosure.
Whereas series MTM has the same current driving both woofers. So they move in the same direction. 😎
Now isobaric is clearly good theoretically. The parallel-wired woofers work together in forward motion.
Something to do with one woofer mounted behind another in a closed box.
It's probably a better way to do things than the classic parallel MTM.
I never like that one. It has an out-of-phase rocking motion that gets the woofers moving in different directions. Push one woofer in, the other moves out. Phase and lobing nightmare. 😕
Think about it. Parallel MTM doesn't give the amplifier any damping control over an out-of-phase motion in a shared enclosure.
Whereas series MTM has the same current driving both woofers. So they move in the same direction. 😎
Now isobaric is clearly good theoretically. The parallel-wired woofers work together in forward motion.
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Then passive radiator systems can't work.
Btw pro sound mtms usually divide the enclosure to protect one mid bass when the other fails. What mtms? Line arrays are stacked mtms.
I found clamshell with the front driver driven at a lower level than the inner driver really surprisingly clean if some damping fluff is along for the ride. And you get a good dispersion match at xo.
Btw pro sound mtms usually divide the enclosure to protect one mid bass when the other fails. What mtms? Line arrays are stacked mtms.
I found clamshell with the front driver driven at a lower level than the inner driver really surprisingly clean if some damping fluff is along for the ride. And you get a good dispersion match at xo.
Wire two bass drivers in parallel and they move in different directions? If that were the case there would be no net air displacement in the enclosure and the myriad of vented MTM cabinets (or anything else with parallel wired drivers) would not actually have any output.
Isobaric variations can be quite good. It isn't technically isobaric (at least, not in terms of the type Linn popularised with their Isobarik), but it can bring some advantages in distortion terms, and it does mean you can reduce cabinet size if you are obliged to use a particular woofer for xyz reason which would otherwise require an unacceptably large Vb.
Isobaric variations can be quite good. It isn't technically isobaric (at least, not in terms of the type Linn popularised with their Isobarik), but it can bring some advantages in distortion terms, and it does mean you can reduce cabinet size if you are obliged to use a particular woofer for xyz reason which would otherwise require an unacceptably large Vb.
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The rocking motion is the possible no-signal condition in an MTM parallel wired in common enclosure.
You could put one hand over one woofer. To stop it moving. It goes high impedance at the Fs.
The other woofer now has twice the box volume to move in, so impedance at Fs goes lower. And it now moves twice as much with signal. Possibly the bass frequency response goes deeper too.
It's like the differential on a car's back axle. One wheel spins on slush, the other can be stationary on the road.
In isobaric cabinet within cabinet, the parallel wired woofers work better with each other, because mechanical polarity is opposite. Series wired would probably be bad in isobaric.
You could put one hand over one woofer. To stop it moving. It goes high impedance at the Fs.
The other woofer now has twice the box volume to move in, so impedance at Fs goes lower. And it now moves twice as much with signal. Possibly the bass frequency response goes deeper too.
It's like the differential on a car's back axle. One wheel spins on slush, the other can be stationary on the road.
In isobaric cabinet within cabinet, the parallel wired woofers work better with each other, because mechanical polarity is opposite. Series wired would probably be bad in isobaric.
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The Kaboominator Big bass in your place. Article By Jeff Poth
A little bit down, "What is isobaric".
The biggest advantage of isobaric in my opinion is that for a given box size, you can mount two clamshells on opposing panels, compared to one single instance of the same driver, giving 4x power handling, 2x displacement, and reduced distortion and box coloration. Build quality of the driver matters, as does good matching, but you wind up with a better sounding solution using inexpensive (But decent quality) drivers than a single "super-sub".
A little bit down, "What is isobaric".
The biggest advantage of isobaric in my opinion is that for a given box size, you can mount two clamshells on opposing panels, compared to one single instance of the same driver, giving 4x power handling, 2x displacement, and reduced distortion and box coloration. Build quality of the driver matters, as does good matching, but you wind up with a better sounding solution using inexpensive (But decent quality) drivers than a single "super-sub".
Scroll down for small bookshelf with isobaric 6" woofers to keep it small
http://www.diyaudio.com/forums/multi-way/282141-6fe200-st200.html
http://www.diyaudio.com/forums/multi-way/282141-6fe200-st200.html
you can see quite a few isobaric arrangements here...
http://www.diyaudio.com/forums/multi-way/263598-goldmund-speakers.html
http://www.diyaudio.com/forums/multi-way/263598-goldmund-speakers.html
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