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Multi-Way Conventional loudspeakers with crossovers

2 way TL using SB23NBACS45 and SB29RDCN
2 way TL using SB23NBACS45 and SB29RDCN
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Old 27th August 2018, 07:59 AM   #11
eg92b16a is offline eg92b16a  Australia
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Quote:
Originally Posted by pkitt View Post
I substituted your T/S measurements into my model without any other changes, resulting in the predicted anechoic system bass response (red line) attached below. The only real change is a slightly lower output SPL (0.6 dB lower) but the same f3 for the same input power I used. A shorter line with a larger taper ratio does wonders for smoothing out the ripples in the response above 200 Hz or so and allows a lighter stuffing density. Your stuffing density works out to be a bit less than 1.6 lb/ft3 and unnecessarily makes f3 higher (a stuffing density over 1 lb/ft3 usually means the basic TL design can be improved).
Paul
Thanks for the info Paul. I'll have another go at the TL software tonight using a larger taper ratio.
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Old 27th August 2018, 08:33 AM   #12
eg92b16a is offline eg92b16a  Australia
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OK, now I'm struggling with the imperial to metric conversions of pounds/ft3 to kg/m3.
A fill rate of 0.75 pounds / ft3 = 340g/27L. To get to kg/m3 is a factor of 37, which would mean 12kg/m3.
1lb/ft3 = 16kg/m3. That's a lot of fill.

So in reality, my TL design with 2.5kg/m3 is the equivalent of 0.15lb/ft3, which I just checked with an online calculator.
Cheers.
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Old 27th August 2018, 08:55 AM   #13
eg92b16a is offline eg92b16a  Australia
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Here is the updated TL.
Fill is equivalent to 0.3lb / ft3.
Attached Images
File Type: gif SB TL5.gif (134.5 KB, 281 views)
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Old 27th August 2018, 10:01 AM   #14
jtgofish is offline jtgofish
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Originally Posted by eg92b16a View Post
OK, now I'm struggling with the imperial to metric conversions of pounds/ft3 to kg/m3.
A fill rate of 0.75 pounds / ft3 = 340g/27L. To get to kg/m3 is a factor of 37, which would mean 12kg/m3.
1lb/ft3 = 16kg/m3. That's a lot of fill.

So in reality, my TL design with 2.5kg/m3 is the equivalent of 0.15lb/ft3, which I just checked with an online calculator.
Cheers.

Try thinking like a Neanderthal to deal with those non-metric measurements.Tony Abbott might be able to help you with that.
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Old 27th August 2018, 10:24 AM   #15
eg92b16a is offline eg92b16a  Australia
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Old 27th August 2018, 02:43 PM   #16
pkitt is offline pkitt  United States
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Yep, you are correct; I made a decimal point location error in converting cubic meters to cubic feet. That said, a stuffing density of 0.15 lb/ft3 is hardly a "heavy stuffing density" as you first described it and is woefully inadequate, explaining why your modeled responses with the LA software have such big dips in them above 200 Hz or so. Using a larger taper ratio will have very positive effects on smoothing the response, but even at 10:1, you'll end up with a very "bumpy" response unless you also use a stuffing density significantly larger than 2.5 kg/m3. Sorry about my mathematical mistake.
Paul

Quote:
Originally Posted by eg92b16a View Post
OK, now I'm struggling with the imperial to metric conversions of pounds/ft3 to kg/m3.
A fill rate of 0.75 pounds / ft3 = 340g/27L. To get to kg/m3 is a factor of 37, which would mean 12kg/m3.
1lb/ft3 = 16kg/m3. That's a lot of fill.

So in reality, my TL design with 2.5kg/m3 is the equivalent of 0.15lb/ft3, which I just checked with an online calculator.
Cheers.
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Old 27th August 2018, 07:15 PM   #17
pkitt is offline pkitt  United States
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Help this poor "Neanderthal" out a bit because I'm not entirely familiar with the LA software. Is the line length 140 or 190 cm and if 190, does the 140 cm indicate how far down the line the stuffing is located? The woofer's center is located 30 cm from the beginning of the line? Based on the listed starting and ending areas shown, it looks like the line has a nominal taper ratio of 2.5:1? I ask because I want to model your line with Martin King's software that I know is completely correct. One of the major problems with the LA software was its algorithm for stuffing density, and AFAIK it was never completely corrected. With such a low taper ratio and low stuffing density, assuming only the first 2/3 or less of the line is stuffed, the smoothness of your modeled response is questionable. I'm not criticizing your work, please understand, only hoping you don't end up with something rather different from and inferior to what you think you were going to achieve.
Thanks,
Paul

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Originally Posted by eg92b16a View Post
Here is the updated TL.
Fill is equivalent to 0.3lb / ft3.

Last edited by pkitt; 27th August 2018 at 07:22 PM.
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Old 27th August 2018, 08:29 PM   #18
eg92b16a is offline eg92b16a  Australia
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Quote:
Originally Posted by pkitt View Post
Help this poor "Neanderthal" out a bit because I'm not entirely familiar with the LA software. Is the line length 140 or 190 cm and if 190, does the 140 cm indicate how far down the line the stuffing is located? The woofer's center is located 30 cm from the beginning of the line? Based on the listed starting and ending areas shown, it looks like the line has a nominal taper ratio of 2.5:1? I ask because I want to model your line with Martin King's software that I know is completely correct. One of the major problems with the LA software was its algorithm for stuffing density, and AFAIK it was never completely corrected. With such a low taper ratio and low stuffing density, assuming only the first 2/3 or less of the line is stuffed, the smoothness of your modeled response is questionable. I'm not criticizing your work, please understand, only hoping you don't end up with something rather different from and inferior to what you think you were going to achieve.
Thanks,
Paul
Thanks Paul.

The line overall length is 1.9m. Sd1=800cm2 and Sd2=100cm2. The driver is located 30cm from the closed end. The filling is in the first 1.4m of the line at a density of 5kg/m3. Now that I know this level of fill is considered “light”, I’ll have another go with a density of 8kg/m3 to see the effect.
Cheers
Jason

Last edited by eg92b16a; 27th August 2018 at 08:33 PM.
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Old 27th August 2018, 09:21 PM   #19
ernperkins is offline ernperkins  United States
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At first glance it appears both versions do a lot more to protect the tweeter down low. It would be informative to see how close these match to actual LR4/6/8 curves. Does VirtuixCAD have that capability? I'm used to Passive Crossover Designer (PCD) where you can pick a crossover type & slope as a target and design the crossover so the driver response matches that target.

Other than that it's down to measurements (on-axis, distortion, off axis, etc.) and listening to the drivers.


Quote:
Originally Posted by eg92b16a View Post
Ok All,

I have had a look at Zaphs pages on the crossover designs with SB29RDCN and have come up with a couple of solutions that I would like everyone to have a look at. First one is 1400Hz crossover 18db/octave and second one is 1250Hz crossover 24db/octave. 2nd pic is my current running version. Tweeter with reversed polarity. Very large suckout at crossover point when tweeter is normal polarity.


I'll put the above parameters into TL software and see if I can get a better response.
Cheers.
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Old 27th August 2018, 10:27 PM   #20
LineSource is offline LineSource  United States
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The Re=6.5ohm Wavecor TW030WA12 is a 30mm dome tweeter in a modest depth waveguide which both extends the low frequency range and provides controlled directivity. Looks like another option for your 2-way design.

TW030WA11 and TW030WA12 are tweeters designed for the most demanding applications, where low resonance frequency, high sensitivity and power handling, controlled dispersion, and a very wide frequency range are required.
FEATURES
• Featuring waveguide face plate for controlled dispersion, offering optimized off-axis and power response
• 30 mm voice coil design with high power handling, and low resonance frequency
• Copper clad center pole yielding very low voice coil inductance for reduced distortion and increased high frequency output
• Internal volumes for low resonance frequency and distortion
• Precision-coated textile diaphragm for improved consistency and high-frequency extension
• Optimized dome shape for ultra high frequency cutoff
• Vented voice coil former for reduced distortion and compression
• Copper-clad aluminium voice coil wire offering lower moving mass for improved efficiency and transient response
• Build-in cavities under dome/edge to equalize pressure for lower distortion and lower resonance frequency
• Flexible lead wires for higher power handling and larger excursion
• Gold plated terminals to prevent oxidation and ensure long-term reliable connection
• Delivered with foam gasket attached for hassle-free mounting and secure cabinet sealing
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