For those of us trying to get the most displacement per dollar regardless of driver size there should be a pretty easy formula right?
I've taken linear Xmax (one way) and multiplied it by the Sd of the driver to come up with a comparative number for displacement. I know that the units are different but as long as you are always using the same units for each driver it shouldn't really matter(should it?). It's just a comparison after all.
Once you have a figure for displacement you simply find the cost of the driver and divide it by your displacement.
Maybe I'm way out to lunch but it seems like you can get more displacement per dollar using some smaller woofers in an array than you can with one large driver.
Is this a calculation worth keeping in mind? I would have no problem using an array behind a theater screen or tucked into a corner if it got me the results for less money.
Lets all assume an optimum sealed enclosure just to keep it simple😀
I've taken linear Xmax (one way) and multiplied it by the Sd of the driver to come up with a comparative number for displacement. I know that the units are different but as long as you are always using the same units for each driver it shouldn't really matter(should it?). It's just a comparison after all.
Once you have a figure for displacement you simply find the cost of the driver and divide it by your displacement.
Maybe I'm way out to lunch but it seems like you can get more displacement per dollar using some smaller woofers in an array than you can with one large driver.
Is this a calculation worth keeping in mind? I would have no problem using an array behind a theater screen or tucked into a corner if it got me the results for less money.
Lets all assume an optimum sealed enclosure just to keep it simple😀
I do this often, but you, also need to factor in the cost of materials to build the cabinet(s) to be fair.
Example, one 21" woofer vs. 3-18" woofers. The 18" woofers come out cheaper and you get a hair more vd per US dollar, but when you factor in the size of the cabinets needed and the cost of the materials. The 21" woofer was the obvious choice for me. Turned out to be close to 100/USD cheaper and pack space was 2.5 times smaller.
Example, one 21" woofer vs. 3-18" woofers. The 18" woofers come out cheaper and you get a hair more vd per US dollar, but when you factor in the size of the cabinets needed and the cost of the materials. The 21" woofer was the obvious choice for me. Turned out to be close to 100/USD cheaper and pack space was 2.5 times smaller.
With bikes and cars, you want HP/weight. So my motorcycle (BMW R1100S) is equivalent to a Corvette if you could shoe-horn into the Corvette an 800 HP engine, I once figured*.
I think you'd really want to have Bl cooked into the index. After all, you can buy real cheap large drivers with small magnets.
B.
*lots of other reasons why bikers use their HP for better performance even more.
I think you'd really want to have Bl cooked into the index. After all, you can buy real cheap large drivers with small magnets.
B.
*lots of other reasons why bikers use their HP for better performance even more.
So we take Bl and divide it by the volume of displacement figure(VD) that we got from Xmax multiplied by Sd. Then we have how much motor strength we have available to push the air.
Right now I'm comparing the Peerless SDS-160f25pr01-08 6 1/2" woofer with the Dayton UM15-22 15" subwoofer. the cost per VD is very similar between them, but the Bl per VD is wayyy higher with the peerless. Which leads me to believe that making a sub with equal VD with the Peerless vs. the Dayton, the peerless should trounce it. Either that or I'm insane or simply mistaken lol.
Not really, BL alone doesn't tell you much.
If you want to know the strength of the motor you have to calculate the Electromagnetic damping (Rme), which you can calculate with: (BL*BL)/Re.
Problem however, it is an idealized parameter that doesn't include losses (mainly Eddy current losses). To include those losses you need to calculate Rme' with: (BL*BL)/Zmin.
If you want to know the strength of the motor you have to calculate the Electromagnetic damping (Rme), which you can calculate with: (BL*BL)/Re.
Problem however, it is an idealized parameter that doesn't include losses (mainly Eddy current losses). To include those losses you need to calculate Rme' with: (BL*BL)/Zmin.
Infinite Baffle builders seem to focus on this, cos displacement is the main attribute for IB builds. You might find a chart somewhere of exactly what you're talking about.
I'd also factor:
1) local availability / shipping costs
2) cabinet layout
Local availability would tilt me personally to using 18" or smaller.
Also using drivers in opposed pairs (or quads, or whatever) seems like a good idea, to cancel vibration / allow for lighter cabinets, like the build in post 3559 (not a sub, but the idea / layout is still relevant):
The Boominator - another stab at the ultimate party machine
Thanks for replying first off. Learning new tricks is great 😀
The Peerless specs have that calculation listed as "motor efficiency factor". Using that number it looks like the peerless still has a good edge on the Dayton UM15. I get that you would need around 18 6.5 inch drivers to equal the displacement of the UM15 and it would cost a bit more to build, but the small footprint of an array is appealing to me since I do a lot of hidden speaker installs. I would also have to assume that it would move the air a lot easier given the combined Sd of the array would be more than 3 times that of the UM15.
https://www.parts-express.com/pedocs/specs/264-1146-parts-express-specifications.pdf
https://www.parts-express.com/pedocs/specs/295-514--dayton-audio-um15-22-specifications.pdf
It has been fun doing a comparison, but it would be cool if I knew that I was doing it correctly. If anyone wants to take a stab at it then by all means. The prices per unit on Parts Express are $17.10 for the Peerless and $224.90 for the Dayton.
https://www.parts-express.com/pedocs/specs/295-514--dayton-audio-um15-22-specifications.pdf
It has been fun doing a comparison, but it would be cool if I knew that I was doing it correctly. If anyone wants to take a stab at it then by all means. The prices per unit on Parts Express are $17.10 for the Peerless and $224.90 for the Dayton.
Notes
Single Parameter, Bass System Design is a dog that will not hunt well for you here.
Initial (Up Front) vs. Life-Cycle Costs usually remain an unaddressed issue in the design effort as well.
To evaluate driver large scale signal performance, you may want to consider the following:
1) You need to be concerned about the precise definitions of Xmax that various driver manufacturers are using. They are not all the same. A strict geometrically defined limit (were further excursion requires a portion of the voice coil to leave the magnetic gap) may lead to more accurate driver comparisons in regards to their 'real' volume displacement capabilities.
2) If the coil is under-hung (vs. over-hung), driver cost and efficiency will be much higher.
3) Typical optimization of system bass performance requires deployment of multiple bass units. In P.A. venues, array spread should be comparable to the wavelength of the lowest frequency to be reproduced. For domestic settings a three unit deployment is the point of diminishing performance returns.
4) For P.A. Systems, reliability is a primary concern, as the cost of a single system failure is unacceptable. Here heat dissipation capabilities will most likely be the limiting factor, not volume displacement
Regards,
WHG
Single Parameter, Bass System Design is a dog that will not hunt well for you here.
Initial (Up Front) vs. Life-Cycle Costs usually remain an unaddressed issue in the design effort as well.
To evaluate driver large scale signal performance, you may want to consider the following:
1) You need to be concerned about the precise definitions of Xmax that various driver manufacturers are using. They are not all the same. A strict geometrically defined limit (were further excursion requires a portion of the voice coil to leave the magnetic gap) may lead to more accurate driver comparisons in regards to their 'real' volume displacement capabilities.
2) If the coil is under-hung (vs. over-hung), driver cost and efficiency will be much higher.
3) Typical optimization of system bass performance requires deployment of multiple bass units. In P.A. venues, array spread should be comparable to the wavelength of the lowest frequency to be reproduced. For domestic settings a three unit deployment is the point of diminishing performance returns.
4) For P.A. Systems, reliability is a primary concern, as the cost of a single system failure is unacceptable. Here heat dissipation capabilities will most likely be the limiting factor, not volume displacement
Regards,
WHG
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