Swinging dipole
StabMe:
Did you make the frames metal for any particular reason? Prefer to work with metal? I ask because I find this technique very interesting. Over the years there have been some really intriguing efforts made by various individuals.
I wonder how much a metal frame such as yours might affect sound, compared to wood, or even just handing the drivers from the ceiling? Doubtful that would work for boxed subs, but a driver hanging naked shouldn't be a problem.
I've been reading the last few weeks about various opinions on using low QTS drivers in applications such as this, and the attendant results. Anyone care to comment? What I can gathered was that the low QTS would require more EQ and thus power, but I don't recall anyone commenting about designs where you are not trying to hit 120db, or anywhere close to that.
A final comment; years ago, someone had a design that clamped metal rings around the woofer magnet, and had cables with turnbuckles on them heading out in various directions in order to stabilize the driver. The cables were high strength, small diameter.
Keep on reporting your results. This is good stuff!
StabMe:
Did you make the frames metal for any particular reason? Prefer to work with metal? I ask because I find this technique very interesting. Over the years there have been some really intriguing efforts made by various individuals.
I wonder how much a metal frame such as yours might affect sound, compared to wood, or even just handing the drivers from the ceiling? Doubtful that would work for boxed subs, but a driver hanging naked shouldn't be a problem.
I've been reading the last few weeks about various opinions on using low QTS drivers in applications such as this, and the attendant results. Anyone care to comment? What I can gathered was that the low QTS would require more EQ and thus power, but I don't recall anyone commenting about designs where you are not trying to hit 120db, or anywhere close to that.
A final comment; years ago, someone had a design that clamped metal rings around the woofer magnet, and had cables with turnbuckles on them heading out in various directions in order to stabilize the driver. The cables were high strength, small diameter.
Keep on reporting your results. This is good stuff!
Hey, homebuilder!
I chose metal because i hate (nor have any talent) working with wood and i have a friend who soldiered those metal parts according to the plan i made in SketchUp. Metal is hollow, but filled with sand so it doesn't resonate.
Can't see any reason why driver hung from the ceiling won't work. IIRC, someone here tried this - try searching the forum. Doubtful about boxed subs (maybe this will minimize floor rattle?), but for nude dipoles - why not?
As for QTS of the driver - yeah, the general rule of thumb among the OB enthusiast has been using higher qts drivers, like Eminence 15 (it was Alpha model, iirc). But i tried simulating them in HornResp and comparing to each other. Simulations has shown that driver that i chose as a midbass, although not a classical 'OB' woofer', was capable of more SPL at lowest required frequency than that of the OB-suited woofer. So results may vary.
You will certainly need EQ if you decide to work with dipoles, that is for sure.
I chose metal because i hate (nor have any talent) working with wood and i have a friend who soldiered those metal parts according to the plan i made in SketchUp. Metal is hollow, but filled with sand so it doesn't resonate.
Can't see any reason why driver hung from the ceiling won't work. IIRC, someone here tried this - try searching the forum. Doubtful about boxed subs (maybe this will minimize floor rattle?), but for nude dipoles - why not?
As for QTS of the driver - yeah, the general rule of thumb among the OB enthusiast has been using higher qts drivers, like Eminence 15 (it was Alpha model, iirc). But i tried simulating them in HornResp and comparing to each other. Simulations has shown that driver that i chose as a midbass, although not a classical 'OB' woofer', was capable of more SPL at lowest required frequency than that of the OB-suited woofer. So results may vary.
You will certainly need EQ if you decide to work with dipoles, that is for sure.
Swinging dipole
StabMe:
Did you test a variety of mid-basses to arrive at a final choice? Or, did you have those on hand? Just curious. I have some very powerful, high efficiency, low QTS midbass sitting around that make me wonder how they would sound mounted in free air such as your design.
For purposes of experimenting, I have a couple of 7' tall black server racks with no side panels sitting in my basement that I got nearly free for the hauling. I've always thought it could be very handy to put amplifiers on shelves mounted in the rack down low, and then suspend drivers in the rack as needed. I'm sure you would get a bit of reflection off the 4 corner posts. But just for a trial? Lots of places to mount stuff, and they roll around on very heavy duty casters.
StabMe:
Did you test a variety of mid-basses to arrive at a final choice? Or, did you have those on hand? Just curious. I have some very powerful, high efficiency, low QTS midbass sitting around that make me wonder how they would sound mounted in free air such as your design.
For purposes of experimenting, I have a couple of 7' tall black server racks with no side panels sitting in my basement that I got nearly free for the hauling. I've always thought it could be very handy to put amplifiers on shelves mounted in the rack down low, and then suspend drivers in the rack as needed. I'm sure you would get a bit of reflection off the 4 corner posts. But just for a trial? Lots of places to mount stuff, and they roll around on very heavy duty casters.
I had BMS 12N820 (qts 0.17) on nude OB for a while, nothing wrong with that other than horrible vent noise
here´s graph how does it look like
Hi Stab,
yes, someone did hang his OB from the ceiling:
Ultimate Open Baffle Gallery
But with 55 free-swinging kilogramms, it is better to check the ceiling construction first...
which I did, therefore no expensive accidents this time...
All the best
Mattes
Um, i have simulated a few midbasses that i could get cheap here locally. When we talk about midbass, we mean a 15" 18Sound driver that works in 55-200Hz range. I simulated it in Hornresp. I knew i was going to use H-Baffle and H-Baffle can be modeled as compounded horn in HR. You can find more details in this thread.
A lower midrange in Beyma 12G40. I have some experience with Beymas (8G40) and i really like the sound. Besides, mige0 was speaking highly of this model in one of threads so i figured i had to try it.
Good idea for a start, i guess.
Mattes,
Really cool implementation. Congratulations!
Ok, some measurements:
Single point measurement, left and right channel:
Moving Mic Method measurement, 20 averages, an 8-figure near my head while sitting in LP:
Waterfall L:
Waterfall R:
ETC:
RT60:
I am now using low pass at 55Hz 2nd order for the sub and 4th order for midwoofer. A few peaks are tamed on the sub and it blends much much better now. But there is still a huge peak at about 55Hz and no matter how much cut i apply it doesn't go away, which is super strange. Maybe some interference, but still don't have a clue.
In terms of decay - my room is super echo'y mess, right?
I do have superchunks in the corners, but no other treatment. Room only have a sofa and a few chairs, no more furniture. Bought some rockwhool (40-50kg per m3), will be making absorbers for the front wall. Also thinking of making a DIY diffuser for the back wall as described here by bwaslo.
Single point measurement, left and right channel:
Moving Mic Method measurement, 20 averages, an 8-figure near my head while sitting in LP:
Waterfall L:
Waterfall R:
ETC:
RT60:
I am now using low pass at 55Hz 2nd order for the sub and 4th order for midwoofer. A few peaks are tamed on the sub and it blends much much better now. But there is still a huge peak at about 55Hz and no matter how much cut i apply it doesn't go away, which is super strange. Maybe some interference, but still don't have a clue.
In terms of decay - my room is super echo'y mess, right?
I do have superchunks in the corners, but no other treatment. Room only have a sofa and a few chairs, no more furniture. Bought some rockwhool (40-50kg per m3), will be making absorbers for the front wall. Also thinking of making a DIY diffuser for the back wall as described here by bwaslo.
Attachments
Yes, responses look very good, but the room has way to high RT. You should use wide area of damping on walls to kill flutter echoes. Bookshelves? Heavy carpet on floor? Traps wont help above 3-400Hz.
http://www.ica2016.org.ar/ica2016proceedings/ica2016/ICA2016-0463.pdf
3 Conclusions
The performance of the acoustic devices installed in the homestudio attenuated frequencies which were designed to act on. Diffractal diffusers were able to reach a wider frequency range than the expected (185Hz to 6880Hz range) – they acted from 122Hz to 7,5kHz. Porous absorbers worked well from 150Hz to 20kHz. Meanwhile, the operation of Helmholtz resonators has drawn attention in the analysis. It was expected that these devices functioned as common as absorbers, reducing the curve decay even if they were installed alone – without the other devices – in the room. However the graphics showed that the resonators don’t work like common absorbers. The operating principle of this device is to resonate on the peaks of resonant modes of the room to eliminate phase cancellations that promote valleys in the acoustic response of the room, leaving the homestudio with a more homogeneous and balanced sound distribution, mainly when they’re functioning in conjunction with diffractal diffusers and porous absorbers.
http://www.ica2016.org.ar/ica2016proceedings/ica2016/ICA2016-0463.pdf
3 Conclusions
The performance of the acoustic devices installed in the homestudio attenuated frequencies which were designed to act on. Diffractal diffusers were able to reach a wider frequency range than the expected (185Hz to 6880Hz range) – they acted from 122Hz to 7,5kHz. Porous absorbers worked well from 150Hz to 20kHz. Meanwhile, the operation of Helmholtz resonators has drawn attention in the analysis. It was expected that these devices functioned as common as absorbers, reducing the curve decay even if they were installed alone – without the other devices – in the room. However the graphics showed that the resonators don’t work like common absorbers. The operating principle of this device is to resonate on the peaks of resonant modes of the room to eliminate phase cancellations that promote valleys in the acoustic response of the room, leaving the homestudio with a more homogeneous and balanced sound distribution, mainly when they’re functioning in conjunction with diffractal diffusers and porous absorbers.
Swinging dipole
Manninen:
How did those midbass sound in your opinion? When you refer to vent noise, is the back of that driver the type with a pole vent? Mine are very low xmax, 12", 100db with one watt variety. Non vented.
StabMe: I read your other post. Very interesting stuff. I was glad you defined what you meant by midbass, because many individuals seem to have their own concept of that. The units I have work very well from about 160hz and up, although they can be EQed lower. They are meant to be sealed in "normal" use. I'm not sure how high mine will play, but I expect about 700-800.
Also, I like your comment on doing a sandwich type construction, after you figure out how you are going to suspend and support everything. A couple days ago, I was at a local salvage yard, and they had hundreds of very interesting off-cuts of aluminum, stainless, brass, etc. All for sale at very reasonable prices. (By the pound) Many of them were brand new, from some fabrication applications. I was enamored with several super heavy. 8' long aluminum posts that looked very nice for a project like yours.
Around here, lots of companies have laser jet, water cutters, etc. Do you have access to any of that type of fabrication? If so, I think it would be fairly reasonable to have someone CNC out some pieces for you to make up a sandwich of metal and wood.
I had lunch with my best friend yesterday, and told him about my thoughts to build a couple of speakers for my hobby room. He reminded me that he and his partner own a super nice shop that makes custom cabinets. Full of CNC routers, edge banders, etc. And, a professional spray booth. Wow...could not believe I hadn't thought of it! But even with that, everything cost money and time. His workers are not "free", so it would still cost a lot to do anything, because he and I don't have a clue how to program a CNC.
I want to follow your progress, because it is very interesting. Keep up the good work.
Manninen:
How did those midbass sound in your opinion? When you refer to vent noise, is the back of that driver the type with a pole vent? Mine are very low xmax, 12", 100db with one watt variety. Non vented.
StabMe: I read your other post. Very interesting stuff. I was glad you defined what you meant by midbass, because many individuals seem to have their own concept of that. The units I have work very well from about 160hz and up, although they can be EQed lower. They are meant to be sealed in "normal" use. I'm not sure how high mine will play, but I expect about 700-800.
Also, I like your comment on doing a sandwich type construction, after you figure out how you are going to suspend and support everything. A couple days ago, I was at a local salvage yard, and they had hundreds of very interesting off-cuts of aluminum, stainless, brass, etc. All for sale at very reasonable prices. (By the pound) Many of them were brand new, from some fabrication applications. I was enamored with several super heavy. 8' long aluminum posts that looked very nice for a project like yours.
Around here, lots of companies have laser jet, water cutters, etc. Do you have access to any of that type of fabrication? If so, I think it would be fairly reasonable to have someone CNC out some pieces for you to make up a sandwich of metal and wood.
I had lunch with my best friend yesterday, and told him about my thoughts to build a couple of speakers for my hobby room. He reminded me that he and his partner own a super nice shop that makes custom cabinets. Full of CNC routers, edge banders, etc. And, a professional spray booth. Wow...could not believe I hadn't thought of it! But even with that, everything cost money and time. His workers are not "free", so it would still cost a lot to do anything, because he and I don't have a clue how to program a CNC.
I want to follow your progress, because it is very interesting. Keep up the good work.
It depends so much of driver, and on ob how much it need eq. i had one non vented 9" on ob, it had type of spitting sound when air was coming out thru spider. When theres a dust cap there is air movement going on.
and of course i think high power 4" coils with vent is the worst you can go with ob like my BMS driver is.
and best i guess is acoustic elegances with their open construction, small diameter voice coils and no dust cap
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