Hi All, has anyone come across a system that can handle bass down to about 40Hz without damage to the ribbon or audible distortion ? If so, i would like to find out a bit more on this.
110db SPL at 40Hz for a monopole speaker requires 1,500 cm^3 of volume displacement.
A large planar magnetic speaker like the Apogee or Magnepan bass panel are currently used to reach 40Hz with reasonable SPLs. A 6' x 2' panel is 11,150 cm^2. These are dipoles and require even more volume displacement for deep bass, about 2,400cm^3 dipole displacement at 40Hz 110db would be a good estimate.
110db SPL at 80Hz for a monopole speaker requires 375 cm^3 of volume displacement. My bass ribbons are steeply crossed at 80hz since this is close to the limit of human voice.
A large planar magnetic speaker like the Apogee or Magnepan bass panel are currently used to reach 40Hz with reasonable SPLs. A 6' x 2' panel is 11,150 cm^2. These are dipoles and require even more volume displacement for deep bass, about 2,400cm^3 dipole displacement at 40Hz 110db would be a good estimate.
110db SPL at 80Hz for a monopole speaker requires 375 cm^3 of volume displacement. My bass ribbons are steeply crossed at 80hz since this is close to the limit of human voice.
Among others, Apogee?
Making "pure" metal ribbons go down that low is a big problem.
Doing it with ribbon (metal) conductors on a substrate, not as much of a problem... unless you get huge ur not going to get super high SPLs compared to modern high power, high Xmax cone drivers...
_-_-bear
Making "pure" metal ribbons go down that low is a big problem.
Doing it with ribbon (metal) conductors on a substrate, not as much of a problem... unless you get huge ur not going to get super high SPLs compared to modern high power, high Xmax cone drivers...
_-_-bear
Planar Woofer
I made a planar woofer about 15 years ago. It worked awesome. It did not punch like a paper cone woofer because it was limited in excursion length, but it played very low. I used a frequency generator to sweep from 1-500 hz and it played audible bass all the way down until you could just feel it. I would like to do another one and supplement it with a 10" sub.
I have been talking about building some more ribbons for a couple years, when I get off my butt & do it I will post some pics for everyone. It's cool having a planar forum out here
Im trying to get my hands on a pair of apogee divas to hear what they sould like.
John
I made a planar woofer about 15 years ago. It worked awesome. It did not punch like a paper cone woofer because it was limited in excursion length, but it played very low. I used a frequency generator to sweep from 1-500 hz and it played audible bass all the way down until you could just feel it. I would like to do another one and supplement it with a 10" sub.
I have been talking about building some more ribbons for a couple years, when I get off my butt & do it I will post some pics for everyone. It's cool having a planar forum out here
Im trying to get my hands on a pair of apogee divas to hear what they sould like.
John
Re: Planar Woofer
I have been into planar speakers for about since the early 90's.
I own a Apogee full range and my brother owns an Apogee Diva. I also own a Carver Amazing Loud Speaker Platinum ribbon/ hybrid.
My experience with dipoles are they have the most natural sounding bass of anything I have listened to including horn loaded low frequency bass horns.
The apogee were very quick, not quite as fast as my Khorn, but the panel sounded boxless with no anoying wood colored tones of a box that all boxes create. Even Wilson audio with their very dampened boxes just sounded like it sucke the musicality out of the frequencies.
Over all, I find panel bass sounds the most realistic just like a real Kettle drum in a symphony, because the woofers do not move a lot like this drum, but instead depend on surface area, which sounds the most realistic to me.
The Carver 12 inch aluminum woofers moved a lot of air. It seemed like they could move plus or minus 1 inch on their excursion. The problem with that was the Carver seemed very slow in comparison to the Apogee panel.
My brother built a 18" 4 per side panel subwoofer and found it was very fast. The trick is to use woofers that do not move a lot of air or in otherwords cheap woofers for a panel sub.
An alternative than a ribbon panel would be to use some aluminum 15", 12" or even 10" woofers. I think the aluminum woofers that would be nice for this project would be the http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-368
I like this cheap 10" woofer, because it is very flat up to 500 or so Hz. It also seems to go down relatively low compared to the other 12 or 15 inch woofers of this Dayton reference series. I like their pole piece how it reduces distortion. I would down the road when I get enough funds to try maybe 4 to 8 10 inch woofers a side for a panel sub to mate with my midrange and tweeter compression horns.
I have found with the dipole panel, it has been difficult to do wide bandwidth, so I believe with this 10 inch reference woofer it would do both relatively well compared to other woofers out there. It is black anadized aluminum, which looks nice.
Bill
jreitz said:
I have been into planar speakers for about since the early 90's.
I own a Apogee full range and my brother owns an Apogee Diva. I also own a Carver Amazing Loud Speaker Platinum ribbon/ hybrid.
My experience with dipoles are they have the most natural sounding bass of anything I have listened to including horn loaded low frequency bass horns.
The apogee were very quick, not quite as fast as my Khorn, but the panel sounded boxless with no anoying wood colored tones of a box that all boxes create. Even Wilson audio with their very dampened boxes just sounded like it sucke the musicality out of the frequencies.
Over all, I find panel bass sounds the most realistic just like a real Kettle drum in a symphony, because the woofers do not move a lot like this drum, but instead depend on surface area, which sounds the most realistic to me.
The Carver 12 inch aluminum woofers moved a lot of air. It seemed like they could move plus or minus 1 inch on their excursion. The problem with that was the Carver seemed very slow in comparison to the Apogee panel.
My brother built a 18" 4 per side panel subwoofer and found it was very fast. The trick is to use woofers that do not move a lot of air or in otherwords cheap woofers for a panel sub.
An alternative than a ribbon panel would be to use some aluminum 15", 12" or even 10" woofers. I think the aluminum woofers that would be nice for this project would be the http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-368
I like this cheap 10" woofer, because it is very flat up to 500 or so Hz. It also seems to go down relatively low compared to the other 12 or 15 inch woofers of this Dayton reference series. I like their pole piece how it reduces distortion. I would down the road when I get enough funds to try maybe 4 to 8 10 inch woofers a side for a panel sub to mate with my midrange and tweeter compression horns.
I have found with the dipole panel, it has been difficult to do wide bandwidth, so I believe with this 10 inch reference woofer it would do both relatively well compared to other woofers out there. It is black anadized aluminum, which looks nice.
Bill
10" woofer
I just wanted to correct the above woofer goes up to very flat 800 to 900 Hz and not 500 or so Hz.
Regards, Bill
I forgot how high it went, but just looked at the pdf again of the specs.
I just wanted to correct the above woofer goes up to very flat 800 to 900 Hz and not 500 or so Hz.
Regards, Bill
I forgot how high it went, but just looked at the pdf again of the specs.
I would have an 18" air filter for airplains. If someone likes to build giant ribbons from the folded paper he would just have to pay for the shipping.
jreitz,
The Full Range Apogee midrange ribbon is 84" long and 2" wide ~ 1,060 cm^2, built with ceramic magnets. It is constructed from 15 micron aluminum and crossed with a 6db slope at 320 Hz and 10,000 Hz. A steep 96db slope would allow this ribbon to reach 80hz with about the same excursion limits as the original 6db @320Hz. A 8" midrange is about 200cm^2 area.
I use N42 NdFeB magnets in a DIY midrange ribbon of slightly larger dimensions crossed 48db slopes at 80 and 3,000 Hz. I believe only a 3-way speaker with a very wide bandwidth midrange can acheive the best reproduction.
The Full Range Apogee midrange ribbon is 84" long and 2" wide ~ 1,060 cm^2, built with ceramic magnets. It is constructed from 15 micron aluminum and crossed with a 6db slope at 320 Hz and 10,000 Hz. A steep 96db slope would allow this ribbon to reach 80hz with about the same excursion limits as the original 6db @320Hz. A 8" midrange is about 200cm^2 area.
I use N42 NdFeB magnets in a DIY midrange ribbon of slightly larger dimensions crossed 48db slopes at 80 and 3,000 Hz. I believe only a 3-way speaker with a very wide bandwidth midrange can acheive the best reproduction.
A narrow dipole would need an 18dB/oct displacement increase below it's dipole foldback frequency. Then, you'd need to know what the ribbon's resonance was since its displacement is constant below that frequency. It isn't likely that the ribbon has a resonance at or below 80Hz since even a 6dB/oct xover would likely be incapable of protecting it from excessive LF excursions. But let's say it did have a ribbon resonance at or below 80Hz. Let's say the dipole rollback frequency is 320Hz. This means the ribbon would require a 6dB/oct boost below 320Hz just to maintain flat response (to compensate for the foldback) so that the present 1st order xover is actually achieving a 2nd order acoustic crossover.
Again, quite likely, it's an even higher slope rolloff because the resonance is probably also up around 300Hz...maybe a bit lower. Operating a true ribbon near its resonance is not a good idea since it has such high electrical and mechanical Q which would cause very severe fatigue and, likely, failure.
Also, a true ribbon would suffer from air leakage around the ribbon itself which would dramatically reduce LF output and tend to rock the ribbon so as to equalize the differential pressure. If the airleakage is prevented, it's no longer a true ribbon and of course, the resonance frequency would tend to rise dramatically.
"Ribbonish" asymmetric drive planar drivers are better suited for lowish frequencies where maintaining a low dipole foldback frequency is essential for high SPLs. A symmetric drive can be used too but still, they are far higher in distortion than a true ribbon whose stiffness is not a source of distortion, nor is its magnetic structure.
I'd suggest using a dipole with as large and high Xmax low resonance dynamic drivers as possible, if you want to do much below 150Hz. Just my opinion.
Again, quite likely, it's an even higher slope rolloff because the resonance is probably also up around 300Hz...maybe a bit lower. Operating a true ribbon near its resonance is not a good idea since it has such high electrical and mechanical Q which would cause very severe fatigue and, likely, failure.
Also, a true ribbon would suffer from air leakage around the ribbon itself which would dramatically reduce LF output and tend to rock the ribbon so as to equalize the differential pressure. If the airleakage is prevented, it's no longer a true ribbon and of course, the resonance frequency would tend to rise dramatically.
"Ribbonish" asymmetric drive planar drivers are better suited for lowish frequencies where maintaining a low dipole foldback frequency is essential for high SPLs. A symmetric drive can be used too but still, they are far higher in distortion than a true ribbon whose stiffness is not a source of distortion, nor is its magnetic structure.
I'd suggest using a dipole with as large and high Xmax low resonance dynamic drivers as possible, if you want to do much below 150Hz. Just my opinion.
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