This may be a dumb question, but right now I have 2 drivers mounted clamshell in a vented box. Sounds great but for cosmetics I'd like to make feet and put one driver underneath. The port is 4"x16", so I'm wondering if firing the bottom driver right up at the port will interfere with the air flow? thanks in advance.
No that won't work as you lose the compound effect of the drivers. The original design seems fine to me, the port being close to the drivers is not an issue.
Richie, I'm not sure I follow you on this. Can you explain how he would lose the "compound effect" by mounting the driver in the same way as his first design with the same wiring config?
Mark
Mark
Simple:
- look at how much cone area facing the outside world there is in case 1 vs case 2.
- look at how physically close the coupling is between the cones in case 1 vs case 2
- look at how much cone area facing the outside world there is in case 1 vs case 2.
- look at how physically close the coupling is between the cones in case 1 vs case 2
I had always referred to what that site calls isobarik as compound (although I was aware that isobarik was another name for it), which is not the same as push-pull.
Could be getting rusty on terminology lol. Loudspeaker Design Cookbook is my bible so I'll check in there.
Basically the original poster will be losing out on the box size halving aspect if he goes with design 2.
Could be getting rusty on terminology lol. Loudspeaker Design Cookbook is my bible so I'll check in there.
Basically the original poster will be losing out on the box size halving aspect if he goes with design 2.
Yea, I hear ya. I'm often faced with the same issue(s) 😉
Most definately, by moving the driver as such the OP would have to rebuild his enclosure to compensate for the doubling Vas.
Getto, how about placing the feet on the side the drivers are mounted and standing it upright? One can do wonders with a bit of grill cloth.
If it sounds good to you now, there's no point in changing it...
Mark
Most definately, by moving the driver as such the OP would have to rebuild his enclosure to compensate for the doubling Vas.
Getto, how about placing the feet on the side the drivers are mounted and standing it upright? One can do wonders with a bit of grill cloth.
If it sounds good to you now, there's no point in changing it...
Mark
Simple rule, if the two drivers are coupled by a small cavity, separate from the main box volume, then you have an isobarik. The second design doesn't fit this category at all.
The first design called isobaric will give you the small box and sensitivity of one driver (@ one watt!) as well as cancel 3rd harmonic distortion, some say 2nd but we'll leave it at 3rd for now.
The second design I believe is normally refered to as just push-pull will require twice the enclosure volume of the first and will produce 3dB more output than the first due to double the cone area that interacts with the air. It also has the benefit of canceling distortion as stated above, this is due to the nonlinearities of the surround, spider and flux assymetry, while one driver is going out of its basket the other will be going into its basket so any deviation in "out vs. in" forces/resistances are effectively canceled.
One potential problem I see with the second is that one driver will be floor loaded and the other wont be. Assuming the driver is compatible with horizontal mounting you will still have to deal with the issue of the two loading types. I might sound awesome, or it might have complex interaction issues dont know.
The second design I believe is normally refered to as just push-pull will require twice the enclosure volume of the first and will produce 3dB more output than the first due to double the cone area that interacts with the air. It also has the benefit of canceling distortion as stated above, this is due to the nonlinearities of the surround, spider and flux assymetry, while one driver is going out of its basket the other will be going into its basket so any deviation in "out vs. in" forces/resistances are effectively canceled.
One potential problem I see with the second is that one driver will be floor loaded and the other wont be. Assuming the driver is compatible with horizontal mounting you will still have to deal with the issue of the two loading types. I might sound awesome, or it might have complex interaction issues dont know.
Thanks for the input, everyone!
So do I have an isobarik config now, vs. a push-pull? I've always been a bit confused about where this setup falls. I imagine I still get the harmonic distortion cancellation, but I've lost 6db of efficiency?
Can I take 6 (or 3 for each driver) db off the spec in WinISD to get a more accurate model, especially for cone excursion? I think this amp has a 16Hz rumble filter but I'm not sure. 21Hz would be a bit better, so I'm trying to keep the gain low. However, if it's less efficient, I should be able to turn the gain up safely, right?
hooha, thanks for the great suggestion -- unfortunately the sub is designed for a very specific space. Luckily wifey doesn't mind the way it looks!
edit: nunayafb, just missed your post. Thanks for clarifying. I think I'm finally getting this!
do I still get the nonlinearity cancellation with the first (now final) design?
To all: this is my first sub, it sounds pretty awesome. Goes much lower than most I've heard in stores. I'm impressed with the extension from a pair of 8" drivers.
So do I have an isobarik config now, vs. a push-pull? I've always been a bit confused about where this setup falls. I imagine I still get the harmonic distortion cancellation, but I've lost 6db of efficiency?
Can I take 6 (or 3 for each driver) db off the spec in WinISD to get a more accurate model, especially for cone excursion? I think this amp has a 16Hz rumble filter but I'm not sure. 21Hz would be a bit better, so I'm trying to keep the gain low. However, if it's less efficient, I should be able to turn the gain up safely, right?
hooha, thanks for the great suggestion -- unfortunately the sub is designed for a very specific space. Luckily wifey doesn't mind the way it looks!
edit: nunayafb, just missed your post. Thanks for clarifying. I think I'm finally getting this!
do I still get the nonlinearity cancellation with the first (now final) design?
To all: this is my first sub, it sounds pretty awesome. Goes much lower than most I've heard in stores. I'm impressed with the extension from a pair of 8" drivers.
This is what would happen to a Butterworth isobaric design (blue) if the drivers were split as you describe (red). Thick lines are the frequency response and thin lines describe the maximum output level.
For this particular system, the sensitivity for high frequencies increase by 6 dB, the lower -3 dB frequency moves from 35 to 70 Hz, the maximum level increases by 6 dB except when the port limits the maximum level below ~50 Hz.
I wouldn't do it, unless I needed the extra SPL between 70 and 100 Hz. It is of course possible that your system would behave differently, depending on how well the original design is made, but chances are that you will end up with something similar to what I have described.
An externally hosted image should be here but it was not working when we last tested it.
For this particular system, the sensitivity for high frequencies increase by 6 dB, the lower -3 dB frequency moves from 35 to 70 Hz, the maximum level increases by 6 dB except when the port limits the maximum level below ~50 Hz.
I wouldn't do it, unless I needed the extra SPL between 70 and 100 Hz. It is of course possible that your system would behave differently, depending on how well the original design is made, but chances are that you will end up with something similar to what I have described.
Thanks to all for the help -- I was always unclear about isobaric vs. clamshell vs. push-pull. This makes perfect sense. I'm sticking with the original layout, the amp has more than enough power to match my mains, and I imagine the vent counteracts some of the iso SPL losses.
p.s., I did what I think is a neat thing -- to make an airtight seal with the front baffle and still be able to get at the drivers (since the inner driver is mounted to the inside of the box), I made a gasket out of strips of plastic foam and bolted it up, like the back of the plate amp. Now if I really need to I can pull the screws out and take the front baffle off 😎
p.s., I did what I think is a neat thing -- to make an airtight seal with the front baffle and still be able to get at the drivers (since the inner driver is mounted to the inside of the box), I made a gasket out of strips of plastic foam and bolted it up, like the back of the plate amp. Now if I really need to I can pull the screws out and take the front baffle off 😎
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