Hello,
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.
Thanks!
Ed
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.
Thanks!
Ed
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
Qms: 2.49
Qes: .487
Qts: .408
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."
fs: 18.3 Hz
Vas: 16.3 ft 3
Vas: 460 liters
Cms: 1.15 mm/N
Qms: 2.49
Qes: .487
Qts: .408
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."
subwoofer project
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.
John L.
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.
John L.
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.
Thanks,
Ed
Thanks,
Ed
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.
GM
If they were re-coned with a generic kit, the specs could be way off, so best to get them measured to be sure.
GM
Sithlord2007 said:
(i) The so-called EBP (fs-Qes ratio) does suggest that sealed enclosures will be more suitable.
(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
-Ram
Thanks,
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.
Ed
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.
Ed
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.
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.
No, you got it right the first time. Understand though that it will raise Qts and lower efficiency, increasing box size. There's various ways to add the mass, from crudely epoxying fishing or wheel weights in the 'valley' of the diaphragm/dustcap or even bonding a flat disc with insulation in the cavity.
From Ron E:
For mass loading:
mass(m) = 21.9453*dia^4(cm)/(Fs^2*Vas(liters))
m' = m + mass added
mass ratio(mr) = m'/m
Fs' = Fs/mr^0.5
Qes' = Qes*mr
Qms' = Qms*mr
then: Qts' = Qes'*Qms'/(Qes'+Qms')
Vas is unchanged
n0 = 9.614*10^-10*Fs'^3*Vas(liters)/Qes'
SPL = 112.02+10*Log(n0)
Anyway, when you 'do the math' you'll see that lowering Fs to ~10 Hz isn't practical.
GM
From Ron E:
For mass loading:
mass(m) = 21.9453*dia^4(cm)/(Fs^2*Vas(liters))
m' = m + mass added
mass ratio(mr) = m'/m
Fs' = Fs/mr^0.5
Qes' = Qes*mr
Qms' = Qms*mr
then: Qts' = Qes'*Qms'/(Qes'+Qms')
Vas is unchanged
n0 = 9.614*10^-10*Fs'^3*Vas(liters)/Qes'
SPL = 112.02+10*Log(n0)
Anyway, when you 'do the math' you'll see that lowering Fs to ~10 Hz isn't practical.
GM
Thanks for the replys. I was asking because I was thinking of playing around with a Nestorovic woofer setup as he outlines in his patent. He says that the primary woofer would have a generally higher Fs than the "active" passive radiator which would generally have a lower Fs and a higher mass in its cone. I did some prelim calcs and my box dimensions come out to about 2.5 ft3. I was also going to use some loosely applied damping material in the cabinet as it suggest. Here is the link to the patent if anyone cares to skim over it. It mention the above in section 4, right column, lines 1-9. I know for a fact in all of his Speakerlab projects, his woofer magnets are the same size but the Fs is different.
Maybe I should use a 10" as the Primary and a 12" as the "active" passive????? But I don't have any 10's! UGH!!!
http://www.google.com/patents?hl=en...dh4-Q&sa=X&oi=book_result&resnum=10&ct=result
I was going to connect the finished subs to an active crossover set at 150Hz so this sub would run from that point down.
I suppose I will experiment without changing the cone mass first but I think without adding some mass to the cone the cone may vibrate too much like a true passive radiator to keep it controlled by the circuit in the Nestorovic system and cause unwanted results.
Let me know if you have any suggestions. I got to get that software too!
Thanks,
Ed
Maybe I should use a 10" as the Primary and a 12" as the "active" passive????? But I don't have any 10's! UGH!!!
http://www.google.com/patents?hl=en...dh4-Q&sa=X&oi=book_result&resnum=10&ct=result
I was going to connect the finished subs to an active crossover set at 150Hz so this sub would run from that point down.
I suppose I will experiment without changing the cone mass first but I think without adding some mass to the cone the cone may vibrate too much like a true passive radiator to keep it controlled by the circuit in the Nestorovic system and cause unwanted results.
Let me know if you have any suggestions. I got to get that software too!
Thanks,
Ed
FWIW, Tom Danley long ago worked out PR system design and posted some guidelines on the old basslist that have worked well, so probably would be good for your active PR:
Hi
Not all drivers can be used with a passive radiator but the greater the
moving mass the driver has and lower cutoff frequency is for the box
size, the more likely the passive design will be practical.
Take the area of the driven cone times its Xmax to get its displacement,
allow a factor of 1.5 or 2 times that and find a passive with
aproximatly that displacement (Move the suspension from peak to peak and
use like 75% of that displacement). Take the piston area of the passive
and plug it into your math as the port area. Take the port length times
the area to get volume and the density of air to find the port moving
mass. If the mass is less than can be realised in the real world then
use a larger diameter passive and try the port calculations again.
Best regards,
Tom
Hi
Not all drivers can be used with a passive radiator but the greater the
moving mass the driver has and lower cutoff frequency is for the box
size, the more likely the passive design will be practical.
Take the area of the driven cone times its Xmax to get its displacement,
allow a factor of 1.5 or 2 times that and find a passive with
aproximatly that displacement (Move the suspension from peak to peak and
use like 75% of that displacement). Take the piston area of the passive
and plug it into your math as the port area. Take the port length times
the area to get volume and the density of air to find the port moving
mass. If the mass is less than can be realised in the real world then
use a larger diameter passive and try the port calculations again.
Best regards,
Tom
Thanks for the advice.
I am going to download the software tonight.
Do you think I should be using two of the same woofers for this project or should I use a smaller woofer for the primary and one of these 12" woofers for the "Active" passive? By using the two different sizes, that may avoid having to do any weight changes, no?
I was originally calculating volume of the cabinet as a sealed enclosure, but it should be calculated as a passive with my selected woofer area as the port opening from what I understand now?
Thanks!
Ed
I am going to download the software tonight.
Do you think I should be using two of the same woofers for this project or should I use a smaller woofer for the primary and one of these 12" woofers for the "Active" passive? By using the two different sizes, that may avoid having to do any weight changes, no?
I was originally calculating volume of the cabinet as a sealed enclosure, but it should be calculated as a passive with my selected woofer area as the port opening from what I understand now?
Thanks!
Ed
You're welcome!
As TD noted, with a PR you want it to have quite a bit more displacement, so if the same size driver is used, then it needs 1.5 - 2x the linear excursion or for the same excursion you need 1.5 - 2x more cone area, etc.. I haven't picked apart the patent, but I don't see why it being active would change this as down low it's all about displacement.
WRT to mass, obviously you're going to need a lower Fs driver, so de facto it will be either more massive or more compliant or a combination of them and if you want to keep box size reasonable it will have to have a low Vas, ergo more massive.
Still, you're not going to find a driver with a low enough Fs AFAIK, so mass loading will still be required.
Right, pick a vented alignment and input whatever size driver Sd you want as the vent area and let it calc a length, then find its Vb and air mass and this is how much the diaphragm/VC/DC assembly (Mms) needs to be, so subtract its calculated (or published) Mms to find the amount of added weight required as a first approximation or probably 'close enough' amount.
GM
As TD noted, with a PR you want it to have quite a bit more displacement, so if the same size driver is used, then it needs 1.5 - 2x the linear excursion or for the same excursion you need 1.5 - 2x more cone area, etc.. I haven't picked apart the patent, but I don't see why it being active would change this as down low it's all about displacement.
WRT to mass, obviously you're going to need a lower Fs driver, so de facto it will be either more massive or more compliant or a combination of them and if you want to keep box size reasonable it will have to have a low Vas, ergo more massive.
Still, you're not going to find a driver with a low enough Fs AFAIK, so mass loading will still be required.
Right, pick a vented alignment and input whatever size driver Sd you want as the vent area and let it calc a length, then find its Vb and air mass and this is how much the diaphragm/VC/DC assembly (Mms) needs to be, so subtract its calculated (or published) Mms to find the amount of added weight required as a first approximation or probably 'close enough' amount.
GM
Yet another novice question ...
Xmax: I was looking it up on Wiki on how to calculate.
"In the simplest form, subtract the height of the voice coil winding from the height of the magnetic gap, take the absolute value and divide by 2"
I do not have that information in my specs on the woofer BUT I do have what they refer to as the Voice Coil Overhang given in mm's as 5.1
Would this be it with the measurments/math already done?
Thanks!
Ed
Xmax: I was looking it up on Wiki on how to calculate.
"In the simplest form, subtract the height of the voice coil winding from the height of the magnetic gap, take the absolute value and divide by 2"
I do not have that information in my specs on the woofer BUT I do have what they refer to as the Voice Coil Overhang given in mm's as 5.1
Would this be it with the measurments/math already done?
Thanks!
Ed
I was playing around with WinISP Pro and entered the driver specs for two woofers. One is a 10" and the other is a 12". The cabinet I chose is for a passive design. However, in the Nestorovic system, the 10" is the primary driver and the 12" is the "active" passive, hence it is connected to the amplifier with a magnet, etc., I entered all the parameters in the program and it came up with weird results. It said it could not really calc the box and even gave me a volume of .5 Cu Ft. WAY OFF!
Should I just run numbers by hand for a passive enclosure as if the 12 is a true passive and ignore the fact for now it is an "active" passive?
Should I calculate the cabinet volume as a sealed cabinet instead?
I am kinda new at this part of things, so with a 12" woofer, should the cabinet volume be based on that unit since it will see power allowing for enough volume for it as oppsed to the smaller 10"? Basically the 12" would govern the cabinet volume.
I hope that makes sense.
Thanks,
Ed
Should I just run numbers by hand for a passive enclosure as if the 12 is a true passive and ignore the fact for now it is an "active" passive?
Should I calculate the cabinet volume as a sealed cabinet instead?
I am kinda new at this part of things, so with a 12" woofer, should the cabinet volume be based on that unit since it will see power allowing for enough volume for it as oppsed to the smaller 10"? Basically the 12" would govern the cabinet volume.
I hope that makes sense.
Thanks,
Ed
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