I may want to use the widely-recommended TB W3-871S wide-range drivers in a future multimedia speaker project. The problem is that its T/S parameters are somewhat odd. If I use a sealed box with the normal Q of 0.707, the "optimum" volume is a large 16.7 L (0.59 cubic ft.) I'm leaning towards the acoustic suspension box as opposed to the bass reflex, but if either can be made small enough (<3 L or 0.10 cubic feet) and be optimum, I can accept it. I realize that there are DIY projects on the web using the W3-871, but which one is "optimum"?
If it can be made to fit in a 8.5"x5"x6" (hwd) box and be near optimum, that'd be great!
BTW would it be wise to power the 30-watt-max TBs with 40-watt-per-channel (RMS) amplifiers just for sheer headroom?
Thanks for any advice.
If it can be made to fit in a 8.5"x5"x6" (hwd) box and be near optimum, that'd be great!
BTW would it be wise to power the 30-watt-max TBs with 40-watt-per-channel (RMS) amplifiers just for sheer headroom?
Thanks for any advice.
The single driver Elf 1.0 from CSS uses a vented box that's 6.5"x7.5"x6.25" external. Also, check this design.
John R's TBand
John R's TBand
I want to focus on a sealed box just for the sake of simplicity. With a system Q of 0.707, the internal enclosure volume for the W3-81S is about 3.8 L (0.135 cubic feet), which is a little too big for me. I understand that the 871 doesn't have a very good Xmax, and too small a box can lead to it reaching the excursion limit.
Has anyone used the 871's in higher-Q (i.e. smaller) boxes? Is 0.8 acceptable?
BTW the enclosure sizes I gave earlier were based on incorrect specs given by Creative Sound Solutions (CSS) of Canada, not from TB. Someone should tell them...
Has anyone used the 871's in higher-Q (i.e. smaller) boxes? Is 0.8 acceptable?
BTW the enclosure sizes I gave earlier were based on incorrect specs given by Creative Sound Solutions (CSS) of Canada, not from TB. Someone should tell them...
hey, i just finished building a set of speakers based off of that link. i built the taller ones and they are farely close to your .707 (i think its around .72). i just started auditioning them about 20 min ago and very impressed so far. i understand there will be little to no bass from these, but mated with a small sub, they sound very nice (might run off of my creative/cambridge soundworks 4.1 pc system for the time being. gotta find out the stock speaker's ohms). here's a pic.
Attachments
>I may want to use the widely-recommended TB W3-871S wide-range drivers in a future multimedia speaker project. The problem is that its T/S parameters are somewhat odd. If I use a sealed box with the normal Q of 0.707, the "optimum" volume is a large 16.7 L (0.59 cubic ft.)
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Using measured specs and somewhat less simplified formulas I get 0.95ft^3.
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>I'm leaning towards the acoustic suspension box as opposed to the bass reflex, but if either can be made small enough (<3 L or 0.10 cubic feet) and be optimum, I can accept it. I realize that there are DIY projects on the web using the W3-871, but which one is "optimum"?
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'Optimum' depends on what the app. is, and in your case, the smallest I recommend is a 0.8Qtc with a 2nd order XO at 500hz or 4th at 250Hz to realize all of what little dynamic headroom the driver's capable of. 0.14ft^3 plus driver, then reduce actual Vb to 0.8x and stuff it with 1.0lb/ft^3.
Unfortunately, this doesn't meet your size criteria, so build it the size you want and accept whatever performance you get.
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>BTW would it be wise to power the 30-watt-max TBs with 40-watt-per-channel (RMS) amplifiers just for sheer headroom?
====
It's always better to have too much power (within reason) than not have it and clip the amp and either have it sound compressed and/or damage the driver.
GM
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Using measured specs and somewhat less simplified formulas I get 0.95ft^3.
====
>I'm leaning towards the acoustic suspension box as opposed to the bass reflex, but if either can be made small enough (<3 L or 0.10 cubic feet) and be optimum, I can accept it. I realize that there are DIY projects on the web using the W3-871, but which one is "optimum"?
====
'Optimum' depends on what the app. is, and in your case, the smallest I recommend is a 0.8Qtc with a 2nd order XO at 500hz or 4th at 250Hz to realize all of what little dynamic headroom the driver's capable of. 0.14ft^3 plus driver, then reduce actual Vb to 0.8x and stuff it with 1.0lb/ft^3.
Unfortunately, this doesn't meet your size criteria, so build it the size you want and accept whatever performance you get.
====
>BTW would it be wise to power the 30-watt-max TBs with 40-watt-per-channel (RMS) amplifiers just for sheer headroom?
====
It's always better to have too much power (within reason) than not have it and clip the amp and either have it sound compressed and/or damage the driver.
GM
When looking at John's TB site how would his designs change if I wanted to add 2 speakers per box, or more? Would the Filter values change? I would like to build a center channel with the W3-871's. Thanks
planet10 said:
The designs shown on John's Audio Projects Page seems to have been based off TB's specs, and according to John, sound great. Besides, using CSS's measured values gives enclosure volumes a bit too big for such a small driver. But then again, I don't think the T/S parameters will matter too much when it comes to 3" drivers that won't go very low.
Ok.
MR Wright and Koonce who contacted me when I was still involved with Nuera ordered all the drivers and tested them.
The posted LAUD graphs are their tested files.
Posted files on CSS site are from me as well.
They are direct from TB.
TB tests all specakers before shipping them then sends the data with the shipment and they test 8 units at random.
Then I averaged the 8 test results and that is were the numbers come from.
In the end the numbers mean a little but the responce is what you realy want to see.
And TB is getting very good responce's on posting proper data from OEM.
In all they are very close in responce but the specs may be out a little.
Still in all a lot better data closer than other manufactures that is for sure.
The cabinet CSS uses is for the highest power handling with the lowest FS out put possible.
Design was done by DR Griffin.
CSS ordered a few hundred fronts and backs off a local CNC and I assembled them all.
Same as the 1.5 designed by DR Griffin and fronts and backs were done on a CNC.
Bob wanted to get the most out of the 3" drivers using 3/4" MDF and the round over is a very good start but the scallop is best to get maximum air flow around all 3" drivers due to the frame taper as well as the hole size.
Just not enough air flow around them with out the round over on the inside or the scallop.
Good luck.
Al
www.rawacoustics.ca
MR Wright and Koonce who contacted me when I was still involved with Nuera ordered all the drivers and tested them.
The posted LAUD graphs are their tested files.
Posted files on CSS site are from me as well.
They are direct from TB.
TB tests all specakers before shipping them then sends the data with the shipment and they test 8 units at random.
Then I averaged the 8 test results and that is were the numbers come from.
In the end the numbers mean a little but the responce is what you realy want to see.
And TB is getting very good responce's on posting proper data from OEM.
In all they are very close in responce but the specs may be out a little.
Still in all a lot better data closer than other manufactures that is for sure.
The cabinet CSS uses is for the highest power handling with the lowest FS out put possible.
Design was done by DR Griffin.
CSS ordered a few hundred fronts and backs off a local CNC and I assembled them all.
Same as the 1.5 designed by DR Griffin and fronts and backs were done on a CNC.
Bob wanted to get the most out of the 3" drivers using 3/4" MDF and the round over is a very good start but the scallop is best to get maximum air flow around all 3" drivers due to the frame taper as well as the hole size.
Just not enough air flow around them with out the round over on the inside or the scallop.
Good luck.
Al
www.rawacoustics.ca
1/2" is fine.
I have built about 20 sets using 1/2 and works fine.
If you use it use a 1/2" round over bit as well.
Set the bearing almost 3/4 of the way down the hole.This will give a nice radius on the back side.
I always round over first ,then flush mount the 3" drivers.
I do this as then I know what materail I have and make the most round over I can with the material that is left after the driver is flush mount.
Mounting depth for the screw is not a big deal, as these are only 3" drivers
I have built about 20 sets using 1/2 and works fine.
If you use it use a 1/2" round over bit as well.
Set the bearing almost 3/4 of the way down the hole.This will give a nice radius on the back side.
I always round over first ,then flush mount the 3" drivers.
I do this as then I know what materail I have and make the most round over I can with the material that is left after the driver is flush mount.
Mounting depth for the screw is not a big deal, as these are only 3" drivers
coolkhoa said:
Hello,
Here's some measured parameters averaged from several broken in units:
Fs: 144.6759 Hertz
Qts: 0.8268
Qes: 0.9429
Qms: 6.7112
Vas: 0.2854 litres
Re: 6.7538 ohms
Rm: 54.8227 ohms
R1: 19.2421 ohms
Le: 0.5987 mH
Efficiency: 82 dB 1w/1m
BL: 6.24 Tesla meters
Cm: 202.610 microns/Newton
Mm: 5.9746 grams
Rm (mechanical): 0.809 mechanical ohms (Ns/m)
Cone area: 32 cm^2
The vas average is a delta compliance number, generally more accurate than delta mass. Yes, the Qts is really that high and the Vas is really that low.
RAW is right, don't look into these numbers too much. Just be aware that the minimum box size is about .1 cu ft. Going smaller than that makes the system start to "honk" in the midbass from too high a Qtc. Going larger smooths out the midbass at the expense of power handling. You just have to pick your tradeoff.
Killjoy99 said:
I don't recommend using this notch with 2 drivers per channel. 2 per channel really needs a 1.5 style BSC circuit, which is a totally different thing.
Regards,
John
SQ Kid said:
Nice looking boxes. I thought I might mention something something I added to the page last week. (after not touching the page for almost a year) I had forgotten to include the unique stuffing method for the tall box.
The box needs very heavy stuffing near the bottom, and moderate to heavy stuffing about halfway down, with average stuffing in the rest of the upper portion. What this does is smooth out the 1100hz wavelength node cuased by the vertical length of the enclosure. You might have done this already, but I never made it clear on the web page.
Regards,
John
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