Hey people! I've had an idea on my mind for years and now suddenly I have lots of time and little to know money so I was thinking of taking a crack at making compression drivers for true low end frequencies. (I have no Idea how low I can get)
Ideally im imagining a structure of epoxycrete with a very large, massively dangerous neodynium ring magnet, and a steel ring to create an appropriate magnetic field.
If this doesn't work, I was also considering trying what, funnily enough, might be much safer; a massive field coil with a substantial variac.
I thinking something like 5-6" driver ports
as far as I can tell, the impedance matching will be difficult, possibly requiring a very large horn, but I haven't done the math.
Also finding a material with a super low elastic modulus that I can also form into a dome readily, but still be light and stiff enough to handle the forces inherent in something this silly. I might need to dig up some of my old materials engineering texts to see what I can find. Possibly a novel constrained layer damped dome utilizing both organic and synthetic materials to achieve something without rediculous slew or oscillations in the audible band.
Am I crazy? good crazy? bad crazy? a fool? a mad scientist?
I've been milling this over in me head for around ten years and im ready to make it happen.
PLEASE share your ideas and opinioms! cheers!
(also forgive any typing errors, my keyboard is on its last legs)
Ideally im imagining a structure of epoxycrete with a very large, massively dangerous neodynium ring magnet, and a steel ring to create an appropriate magnetic field.
If this doesn't work, I was also considering trying what, funnily enough, might be much safer; a massive field coil with a substantial variac.
I thinking something like 5-6" driver ports
as far as I can tell, the impedance matching will be difficult, possibly requiring a very large horn, but I haven't done the math.
Also finding a material with a super low elastic modulus that I can also form into a dome readily, but still be light and stiff enough to handle the forces inherent in something this silly. I might need to dig up some of my old materials engineering texts to see what I can find. Possibly a novel constrained layer damped dome utilizing both organic and synthetic materials to achieve something without rediculous slew or oscillations in the audible band.
Am I crazy? good crazy? bad crazy? a fool? a mad scientist?
I've been milling this over in me head for around ten years and im ready to make it happen.
PLEASE share your ideas and opinioms! cheers!
(also forgive any typing errors, my keyboard is on its last legs)
Would be cool if you can....
Here's this thread if you haven't seen it already.
DIY bass compression drivers
Here's this thread if you haven't seen it already.
DIY bass compression drivers
You may want to do the math on the horn before you delve too deeply into the driver design.
Very low frequencies can lead to very large horns if you are trying to maximize output and are using older guidelines. Typically a pile of woofers in regular enclosures and their amplifiers are a lot easier than dealing with a horn for very low frequencies, which I think is why you so rarely see horns covering that range.
Big horn from a few years ago
Horn Subwoofer Takes Up Crazy Man's Entire Basement
And a more "reasonably" sized one from Nelson Pass - that doesn't get into the subwoofer range
PassDiy
Very low frequencies can lead to very large horns if you are trying to maximize output and are using older guidelines. Typically a pile of woofers in regular enclosures and their amplifiers are a lot easier than dealing with a horn for very low frequencies, which I think is why you so rarely see horns covering that range.
Big horn from a few years ago
Horn Subwoofer Takes Up Crazy Man's Entire Basement
And a more "reasonably" sized one from Nelson Pass - that doesn't get into the subwoofer range
PassDiy
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I'm driven to try to make something that can perform TRUE bass frequencies. OF course im not going to get something like a flat 20-120hz, but if I could get even some of the band covered and supplement with a more conventional design, there may be merit to the project.
The more I think about it, a field coil is probably a much better Idea than huge neodymium death trap magnets; if even just for testing, it would allow me to test different frequency bands at specific flux levels.
I've also been thinking that this might be condusive to a unique "concentric multiple voice coil design". Using several rings of voice coils in concentric field coil magnetic sources would allow me to experiment with the way that the driver itself flexes and deforms at different extrusions. It may be that using several rings of different powered field coils would help push a much larger sound producing membrane in a uniform manner.
The other thing; the impedance matching. It's probably going to be another huge hurdle. I may have to experiment with something closer to a periodic suspension/horn hybrid design in order to get the amount of air pumping that true "chest punching" bass benefits from.
I think the first thing to do is to start considering voice coil and dome materials, and figure on whether or not this is even worth looking into. 3d printing smaller models to test the multple concentric ring idea may have merit. Also I'll probably need to build a forming jig to convert my mini lathe into a voice coil winder, eventually one capable of flat ribbon (thats way down the road though)
Also figuring on how large and heavy the base itself will need to be. The whole thing doesnt need to be steel, I see no reason why a large part of the back that makes up the weight couldnt be made with a well thought out epoxy concrete with constrained layer damping or a similar effect using aggregates. Only the front inch or so will likely need to even be made of steel, I can't think that the magnetic fields would need much more to get a good flux geometry.
I'll check out the link! cheers!
The more I think about it, a field coil is probably a much better Idea than huge neodymium death trap magnets; if even just for testing, it would allow me to test different frequency bands at specific flux levels.
I've also been thinking that this might be condusive to a unique "concentric multiple voice coil design". Using several rings of voice coils in concentric field coil magnetic sources would allow me to experiment with the way that the driver itself flexes and deforms at different extrusions. It may be that using several rings of different powered field coils would help push a much larger sound producing membrane in a uniform manner.
The other thing; the impedance matching. It's probably going to be another huge hurdle. I may have to experiment with something closer to a periodic suspension/horn hybrid design in order to get the amount of air pumping that true "chest punching" bass benefits from.
I think the first thing to do is to start considering voice coil and dome materials, and figure on whether or not this is even worth looking into. 3d printing smaller models to test the multple concentric ring idea may have merit. Also I'll probably need to build a forming jig to convert my mini lathe into a voice coil winder, eventually one capable of flat ribbon (thats way down the road though)
Also figuring on how large and heavy the base itself will need to be. The whole thing doesnt need to be steel, I see no reason why a large part of the back that makes up the weight couldnt be made with a well thought out epoxy concrete with constrained layer damping or a similar effect using aggregates. Only the front inch or so will likely need to even be made of steel, I can't think that the magnetic fields would need much more to get a good flux geometry.
I'll check out the link! cheers!
sadly that thread seems to have died about 10 years ago. It seems like one of the major hurdles is the limit of materials for engineering a suitable diaphragm.
And like you mentioned, impedance matching with a horn that isnt 10x the size of an old Western Electric. I think a hybrid cabinet may be able to address some of these issues.
I've heard rumours of true massive bass compression drivers out in the wild for years; I dont think its just a myth. I think there may be actual merit to the project.
And it would be totally bad ***.
And like you mentioned, impedance matching with a horn that isnt 10x the size of an old Western Electric. I think a hybrid cabinet may be able to address some of these issues.
I've heard rumours of true massive bass compression drivers out in the wild for years; I dont think its just a myth. I think there may be actual merit to the project.
And it would be totally bad ***.
The Mforce by Powersoft has a dome!
I mean, it's an application of their mobile magnet loudspeaker...
I mean, it's an application of their mobile magnet loudspeaker...
ill take a peak! cheers!
I'm also currently trying to find, even hints, of how EV made their amazing beryllium diaphragms.
I might actually have to end up looking into polymer chemistry and forms if I can't find a standalone workable material with a low enough elastic modulus. I know that sounds out there, but its really more feasible than it might sound. Making basic plastics aren't even that hard. you just need a fume hood and some labware. Fortunately I'm a glassworker with around 15 years experience in coe33 glass and getting a lathe soon for lab stuff. We'll see.
I think its something that might take years to figure on, but time is all I've got these days.
I'm also currently trying to find, even hints, of how EV made their amazing beryllium diaphragms.
I might actually have to end up looking into polymer chemistry and forms if I can't find a standalone workable material with a low enough elastic modulus. I know that sounds out there, but its really more feasible than it might sound. Making basic plastics aren't even that hard. you just need a fume hood and some labware. Fortunately I'm a glassworker with around 15 years experience in coe33 glass and getting a lathe soon for lab stuff. We'll see.
I think its something that might take years to figure on, but time is all I've got these days.
In case you haven't tripped over it, working with beryllium has toxicity issues that most people are unlikely to be able to handle appropriately at home.
The bigger problem with subs (assuming you mean to work that low) is usually broad nulls and peaks in the room. The usually (and imo best) solution to that is multiple subs placed in different areas of the room -- there are still nulls and peaks but they are more numerous and dense and the sonic effect is a smoother low frequency response that works in more places in the room. That would be multiple smaller woofers, rather than one big one (or a big bass horn, which any domestic room would have room for 1, usually less). Multiple drivers will get you the cone area (comparable to horn mouth area) for SPL without eating up the room space and without being peaky and dippy in a way that makes it kind of useless.
yeh I'm well aware of the whole comb filtering/additive/destructive interference. I normally set up using the Cardas formula if I'm using normal speakers. My old Khorns, well, sat in corners (god I miss those)
I'm just totally enthralled by the sharp edge of the horn sound. I a/b'ed my custom khorns (all new drivers and crossvers) against a 6 figure wilson/conrad johnson system, and I felt I had maybe 80-90% of the sound. As far as the reflections go, a ton can be done with bass traps and a few well placed panels for standing waves.
As far as Berylium is concerned, yeah, I know its very toxic. I've worked with some nasty metals quite a bit in my glass business (used for colorants), and have a longtime hobby working with applied sciency kind of stuff.
Anyways I was mostly just rambling trying to think about how it WAS done.
I think 3d printing is without a doubt a great way to measure deflection, but obviously beyond data, it wont be useful other than as a prototyping material.
One of my glass kilns might actually be useful as a curing oven for ceramics. I've been mulling over it, and, given the amount of sheer power I can achieve either with big Neodymiums or electromagnets (field coils), I might be okay with sacrificing weight for rigidity.
I've seen some interesting videos online about treating glass to make "gorilla glass '. The idea is that you can fill the microscopic surface cracks, giving it much greater strength. so either a very thin glass layer, or possibly a similar ceramic one, with a constrained boundary layer of polymer, and a "gorrilla " treatment on the outside, you should conceivably be able to cut the severe ringing that tends to muck up higher frequencies in glass. (ideally id be nowhere up that high anyhow)
Its such a different design concept. I'm not entirely sure if there is any software online to try to model a predicted response or impedance. I think it will have to be a system of prototyping.
I'm chewing at the bit to finally get out and get my COVID shot. I got severe pneumonia a year or so ago, and still ahve lung issues for that, so I've hidden inside pretty much for a year straight. yay!
I'm disabled due to a back injury (35 yrs old) so I dont have a ton of money, but there is a makers space in town, and I literally have nothing at all to do all day.
Please, more opinions! I think this might be a really cool start to something!
I'm just totally enthralled by the sharp edge of the horn sound. I a/b'ed my custom khorns (all new drivers and crossvers) against a 6 figure wilson/conrad johnson system, and I felt I had maybe 80-90% of the sound. As far as the reflections go, a ton can be done with bass traps and a few well placed panels for standing waves.
As far as Berylium is concerned, yeah, I know its very toxic. I've worked with some nasty metals quite a bit in my glass business (used for colorants), and have a longtime hobby working with applied sciency kind of stuff.
Anyways I was mostly just rambling trying to think about how it WAS done.
I think 3d printing is without a doubt a great way to measure deflection, but obviously beyond data, it wont be useful other than as a prototyping material.
One of my glass kilns might actually be useful as a curing oven for ceramics. I've been mulling over it, and, given the amount of sheer power I can achieve either with big Neodymiums or electromagnets (field coils), I might be okay with sacrificing weight for rigidity.
I've seen some interesting videos online about treating glass to make "gorilla glass '. The idea is that you can fill the microscopic surface cracks, giving it much greater strength. so either a very thin glass layer, or possibly a similar ceramic one, with a constrained boundary layer of polymer, and a "gorrilla " treatment on the outside, you should conceivably be able to cut the severe ringing that tends to muck up higher frequencies in glass. (ideally id be nowhere up that high anyhow)
Its such a different design concept. I'm not entirely sure if there is any software online to try to model a predicted response or impedance. I think it will have to be a system of prototyping.
I'm chewing at the bit to finally get out and get my COVID shot. I got severe pneumonia a year or so ago, and still ahve lung issues for that, so I've hidden inside pretty much for a year straight. yay!
I'm disabled due to a back injury (35 yrs old) so I dont have a ton of money, but there is a makers space in town, and I literally have nothing at all to do all day.
Please, more opinions! I think this might be a really cool start to something!
Does anyone here have experience building multiple voice coil drivers? I'm wondering if there can be issues with the coils frequencies matchupand damping.
I think expecting anything close to 20hz is a fantasy, but if I can get anywhere below the famous 120hz shitty woffer boom. and even under 100, I'd be a happy, happy man.
If you're willing to deal with that kind of restriction, have you looked into Bill Fitzmaurice's designs?
There are a lot of them on his website - some of which have very good sensitivity in the range you are describing. Tuba 18, the DR's, and David, in particular, look feasible in a typical larger listening room. Some of the others may interest you as well.
There are a lot of them on his website - some of which have very good sensitivity in the range you are describing. Tuba 18, the DR's, and David, in particular, look feasible in a typical larger listening room. Some of the others may interest you as well.
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great! once again, I'll look into it.
I'm pretty much keen on something like a traditional jbl/altec style , only 4x the size, and with the power handling capable of moving a very, VERY large diaphragm, hence the multiple concentric voice coils and very large field coils/ large dangerous neodymium ring magnets.
EDIT; so, I had a look at the fitzmaurice stuff, and, honestly? not really. I've owned several large bass loaded bins of similar nature, with traditionaly woofers loading them.
Imagine a driver about half the size of a 5 gallon bucket, that might weigh 100 lbs, and have a 5-6" mount. I could actually see the kleinhhorn working with some slight mods. MAke the box for the full range driver slightly larger, and make a brace/stand to hold up the absolutely rediculous compression driver.
If it fails completely, thats okay! but I have a bit of experience in speaker building, and 25 years of mixed trades/applied science hobbies, and I really think I can take a good crack at it.
Also though, if I use massive ring magnets, that TERRIFIES me. those things are dangerous as all hell, and I'm not sure how I can safely mount them with tiny gaps between, and also mount it onto a steel flux guide.
I'm pretty much keen on something like a traditional jbl/altec style , only 4x the size, and with the power handling capable of moving a very, VERY large diaphragm, hence the multiple concentric voice coils and very large field coils/ large dangerous neodymium ring magnets.
EDIT; so, I had a look at the fitzmaurice stuff, and, honestly? not really. I've owned several large bass loaded bins of similar nature, with traditionaly woofers loading them.
Imagine a driver about half the size of a 5 gallon bucket, that might weigh 100 lbs, and have a 5-6" mount. I could actually see the kleinhhorn working with some slight mods. MAke the box for the full range driver slightly larger, and make a brace/stand to hold up the absolutely rediculous compression driver.
If it fails completely, thats okay! but I have a bit of experience in speaker building, and 25 years of mixed trades/applied science hobbies, and I really think I can take a good crack at it.
Also though, if I use massive ring magnets, that TERRIFIES me. those things are dangerous as all hell, and I'm not sure how I can safely mount them with tiny gaps between, and also mount it onto a steel flux guide.
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most bass horn use the compression driver principle, when the throat area is smaller than the diaphragm area. it's a technique to exchange peak efficiency for bandwidth. i don't see the need to convert the HF driver features into an LF one.
There's a reason most drivers aren't magnetized until later in assembly.
I'm not trying to rain on your parade, but you seem to be coming at this problem from about 9 different directions. Several of which seem at odds with each other, so excuse my confusion over what your goals are.
If you want a large driver with extreme power handling, why are you bothering with a horn? If you just want examples of high excursion/high power subs, there are plenty: Sundown Audio NS-15, Digital Design Z4, MTX Jackhammer 22, Skar ZVX-15v2, Peerless STW-350F-188PR01-04, etc. And how many can handle extreme excursion and power while maintaining some semblance of sound quality?
I'm not trying to rain on your parade, but you seem to be coming at this problem from about 9 different directions. Several of which seem at odds with each other, so excuse my confusion over what your goals are.
If you want a large driver with extreme power handling, why are you bothering with a horn? If you just want examples of high excursion/high power subs, there are plenty: Sundown Audio NS-15, Digital Design Z4, MTX Jackhammer 22, Skar ZVX-15v2, Peerless STW-350F-188PR01-04, etc. And how many can handle extreme excursion and power while maintaining some semblance of sound quality?
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Could you not just upsize a cone compression driver such as the JBL CMCD-81H? Attach a massive horn and Bob's yer uncle, no?🙂
Come to think of it, I just happen to have a brand new pair of 2269s.🙂
hmm
Come to think of it, I just happen to have a brand new pair of 2269s.🙂
hmm
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actually, the CMCD is a really neat example of the sort of thing I'm aiming for, and yes, just scaled up a few x in power handling and size. The issue I think I'll come into, though, is that the diaphragm wont be able to handle the oscillation uniformly after it reaches a certain size, whatever that may be, I'm not sure yet. Hence the multiple annular voice coil idea.
And as to the other question, I'm looking for low bass and extremely low excursion, not high power handling and high excursion; thats pretty much just a modern sub.
Like I said in the opening, I'm going to gather data as I go, as I'm not sure how well the design will work in driver sim software, but its just a funny idea ive had for ages and want to try out. I've been a huge horn fan since I started into this hobby, JBL,TAD,Altec,Vitavox,WE, etc, and I just want to see this design at least tried out.
And as to the other question, I'm looking for low bass and extremely low excursion, not high power handling and high excursion; thats pretty much just a modern sub.
Like I said in the opening, I'm going to gather data as I go, as I'm not sure how well the design will work in driver sim software, but its just a funny idea ive had for ages and want to try out. I've been a huge horn fan since I started into this hobby, JBL,TAD,Altec,Vitavox,WE, etc, and I just want to see this design at least tried out.