Opinions Wanted on Dual 12" Subwoofer Project
I recently purchased a pair of Speakerlab woofers, the W1208R's. According to Speakerlab at the time, they where the best 12" woofers they built for acoustic suspension systems with great results in subwoofer configurations.
So, that takes me to my reason for this thread. I would love some feedback on what you think I should do with them. I was aiming towards a subwoofer ... maybe along the lines of the "closed-box" acoustic suspension.
Any ideas on a crossover? Firing direction? Any general comments?
I want to do an unpowered subwoofer. I may use it in a home theater environment down the road. I would have a separate amp power it. I have attached the SLab description and specs for review.
Pics are too big for uploading apparently. I will add all the tech information shortly. In the meantime, your feedback would be great!
Specs and write up from 1980 or so ...
fs: 18.3 Hz
Vas: 16.3 ft 3
Vas: 460 liters
Cms: 1.15 mm/N
Mms: 66.0 gm
Rms: 3.05 N-sec/M
Sd: .053 Sq.m
Re: 6.2 ohms
Bl: 9.8 T-m
REF SPL: 92.7 dB
Maximum Diameter: 12.00"
Overall Depth: 6.1"
Magnet Material Weight: 42 oz.
Magnet Material: ABF
Total Weight: 9.4 lbs.
Voice Coil Type: 2 Layer
Voice Coil Diameter: 2"
Voice Coil Overhang: 10.4 mm
Surround Type: Butyl
Baffle Opening Dimensions: 11.2"
No. of Mounting Holes: 8
Max. Rec. System Power: 200 watts
Rated Impedance: 8 ohms
Sealed Enclosure Volume: 1.7 - 3.5 cu. ft.
"Quite simply the best 12" woofer for acoustic suspension systems we know how to build. We have spared nothing in the design and construction of this woofer, and have yet to find any other woofer which can match its performance. The voice coil is the longest one we have seen, providing the W1208R with more peal-to-peak linear excursion than any other woofer of any size we know. The soft, free-moving spider and butyl rubber surround easily handle the task of displacing tremendous volumes of air, more than many 15" woofers. Like all of our woofers, the voice coil uses an all aluminum former and the highest temperature adhesives available, making the W1208R virtually "bullet proof". The cone uses our two layer Polylam construction with molded-in concentric ribs for rigidity and high internal damping. The W1208R may also be used in vented, passive radiator, transmission line and subwoofer configurations. Several customers have reported very enthusiastically on their results when using W1208R's in multiple woofer systems. In a sealed enclosure, use 1.7 to 3.5 cubic feet."
Are these "new old stock"... were they used, etc. My Titanic 1200 10 yr. old sub driver has some issues with the surround I had to address as it began failing a yr. or so ago. I'd expect a 20+ yr. old surround to be suspect, even if never used.
Specs look ok, nothing spectacular compared to present day relatively cheap subs.
Thanks for the reply. The surrounds are in great condition from what I can see. As well as the cone. They were taken out of Speakerlab 7's so are used. They where probably reconed at some point but did not ask when I purchased expecting they would need it. But to my surprise, they look great.
Well, they didn't lie WRT the various type box loadings available if its specs are ~accurate, so it boils down to how big a box can you 'afford' since a high Vas combined with a medium high Qts equates to as big as ~17 ft^3 cabs depending on the app and room loading, though I recommend making two to get some room positioning flexibility.
If they were re-coned with a generic kit, the specs could be way off, so best to get them measured to be sure.
(ii) The volume recommendations do not seem to give the complete picture so they are a bit misleading.
The fs-Vas-Qts combination leads to the following quick volume recommendations, assuming high internal box losses (i.e., volume fill, not just lining; if you have just lining, these volumes will go up by a factor of about 2):
Bessel alignment (best transients) -- 6-8.5 cuft
Butterworth alignment (flattest passband response, moderate transient response) -- 3-5 cuft
Chebyshev alignment (sharpest rolloff, poorest transients) -- 2-2.5 cuft
I will try and see if they where reconed and try and have them tested.
I was thinking of putting them in one cabinet. I don't want the cabinet to get ridiculously big as it would be a home theater subwoofer. But, seeing some of the sizes you guys came up with for Prelim's, I think maybe two cabinets are in order.
Two subs one cup
I've put two 12"s into one cabinet before, was building a home sub that is planned to be onsold as a car sub.
I fed one signal to two channels of a stereo amp which fed the speakers independently, as in unbridged, and didn't get the performance I expected.
I added a separating wall, creating two enclosures in the one cabinet, and things got better (unquantified however, there was more lower bass). I don't fully understand it but perhaps there was some sort condition in the amp that couples with the speakers reinforced nature to oscillate out of phase that let it happen much more than they now do with only one side of them acoustically connected.
I wish I'd made them two separate boxes, better dispersion and whatever.
Ok, a novice question ...
Is there a way to lower the Fs on the driver to around 10? It is a coated paper cone.
Not sure how this would be done ... adding more "mass" to the cone like ... don't laugh ... lead tape or something? :cannotbe:
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