Hi Folks,
I've been stalking the forums for a while and have decided it's time for a project!
I have two lab12 drivers knocking around and want to build something small, with 20-25Hz extension, SPL I'm actually not sure about, I don't think I need it that loud, but is 100dB loud enough for home theater?
My current setup is some super cheapo tops I knocked together quickly (Two P-Audio SN3-30N, with a Number One DT-254) just so I could use a spare TH12 tapped horn with the TV.
So I've read a few posts and come up with 4 different options! looks like compromises virtually everywhere, what I need is a little bit of experience to poke me in the right direction.
Option 1: 2 x 45L sealed, linkwitz transform to 25Hz
63.5l external volume, f3 at 32Hz~, High pass 4th order butterworth @ 25Hz.
I get issues with excursion in this sealed box if I want it to go low, as such the power is limited to about 25W and SPL sits at 99dB @ 32Hz, with two cabs that should be 102dB?
Option 2: 50L Vented Isobarik, tuned 27 Hz
118l external volume, f3 at 24Hz, High Pass 4th Order @ 18Hz.
101dB @ 24Hz with 250W, port speed maxing about 13M/s within safe cone excursion.
Option 3: 100L Vented, tuned 25Hz
159l external volume, it’s much bigger than I thought, the ports suggested by eminence have a crazy port speed, so I’m thinking a large square port to increase the area and bring it back down to something similar to the other designs. F3 at 25hz 109dB, it’s by far the loudest within safe cone movement.
Option 4: 85L Vented Isobaric, tuned 21Hz
Bit of a wildcard, at 168l external including area around the exposed driver, it’s a larger version of the 50l vented isobarik to get a lower response.
F3 19Hz, 101dB with 250w, 13m/s port speed, safe cone excursion.
First of all, does any of this look like I’ve just done something wrong?
Secondly, what would your preferred option be? I’m leaning toward the second option, 50l Isobarik.
Thanks!
Robyn
P.S. Don't know why the images are looking stretched in my preview!
Edit... I get it now!
I've been stalking the forums for a while and have decided it's time for a project!
I have two lab12 drivers knocking around and want to build something small, with 20-25Hz extension, SPL I'm actually not sure about, I don't think I need it that loud, but is 100dB loud enough for home theater?
My current setup is some super cheapo tops I knocked together quickly (Two P-Audio SN3-30N, with a Number One DT-254) just so I could use a spare TH12 tapped horn with the TV.
So I've read a few posts and come up with 4 different options! looks like compromises virtually everywhere, what I need is a little bit of experience to poke me in the right direction.
Option 1: 2 x 45L sealed, linkwitz transform to 25Hz
63.5l external volume, f3 at 32Hz~, High pass 4th order butterworth @ 25Hz.
I get issues with excursion in this sealed box if I want it to go low, as such the power is limited to about 25W and SPL sits at 99dB @ 32Hz, with two cabs that should be 102dB?
Option 2: 50L Vented Isobarik, tuned 27 Hz
118l external volume, f3 at 24Hz, High Pass 4th Order @ 18Hz.
101dB @ 24Hz with 250W, port speed maxing about 13M/s within safe cone excursion.
Option 3: 100L Vented, tuned 25Hz
159l external volume, it’s much bigger than I thought, the ports suggested by eminence have a crazy port speed, so I’m thinking a large square port to increase the area and bring it back down to something similar to the other designs. F3 at 25hz 109dB, it’s by far the loudest within safe cone movement.
Option 4: 85L Vented Isobaric, tuned 21Hz
Bit of a wildcard, at 168l external including area around the exposed driver, it’s a larger version of the 50l vented isobarik to get a lower response.
F3 19Hz, 101dB with 250w, 13m/s port speed, safe cone excursion.
First of all, does any of this look like I’ve just done something wrong?
Secondly, what would your preferred option be? I’m leaning toward the second option, 50l Isobarik.
Thanks!
Robyn
P.S. Don't know why the images are looking stretched in my preview!
Edit... I get it now!
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Okay, so first things first, WinISD calculates the Power Input part badly (IMO). It does not account for a large EQ boost at all (such as a Linkwitz Transform), so it's showing nominal power input where no EQ is being applied.
Click over to Amplifier Apparent Power (VA). That'll show you what the amplifier is actually putting out.
With regards to all of the ported designs, I'd probably transfer over to a slot port. It'll be much easier to build than messing with a load of PVC pipes.
IMO, for UK living rooms, a couple of long-throw 12"s in sealed boxes is plenty enough to dig down to 20Hz. Once you've accounted for room gain etc, I find them to be more than adequate. That will depend on your listening volume and program material, of course.
Chris
Click over to Amplifier Apparent Power (VA). That'll show you what the amplifier is actually putting out.
With regards to all of the ported designs, I'd probably transfer over to a slot port. It'll be much easier to build than messing with a load of PVC pipes.
IMO, for UK living rooms, a couple of long-throw 12"s in sealed boxes is plenty enough to dig down to 20Hz. Once you've accounted for room gain etc, I find them to be more than adequate. That will depend on your listening volume and program material, of course.
Chris
I just simmed a LAB12 with WinISD v0.7.0.950 & the Power/Xmax/FreqRes/AirVel/ etc ALL respond & show the effect of using a Linkwitz Transform 
You both need to update the program http://www.linearteam.org/download/winisd-07x.exe
You both need to update the program
http://www.linearteam.org/download/winisd-07x.exeHi Chris! I've not looked at the apparent power graph before, looks interesting! most power being used at frequencies I'm not actually interested in!
With regards to slot ports, If I was going full width they get a bit long unless the aspect ratio is very narrow, I thought it might get noisy at lower air speeds. Not to mention it begins being a little difficult to get a long port in such a small box. I am wondering now though, why would eminence suggest such a low cross sectional area for their 100L box? which theoretically produces very high air speeds, perhaps it's not such an issue...
Could you explain what you mean by a long throw 12"? More importantly, do the labs fit the bill? To be honest, knocking up the sealed cubes would be a doddle, quite tempting for simplicity, but not an interesting build
Zero D, I only just downloaded it this week! it is the Pro Alpha though... should I be using the non pro Beta?
With regards to slot ports, If I was going full width they get a bit long unless the aspect ratio is very narrow, I thought it might get noisy at lower air speeds. Not to mention it begins being a little difficult to get a long port in such a small box. I am wondering now though, why would eminence suggest such a low cross sectional area for their 100L box? which theoretically produces very high air speeds, perhaps it's not such an issue...
Could you explain what you mean by a long throw 12"? More importantly, do the labs fit the bill? To be honest, knocking up the sealed cubes would be a doddle, quite tempting for simplicity, but not an interesting build
Zero D, I only just downloaded it this week! it is the Pro Alpha though... should I be using the non pro Beta?
The more the merrier spread around will help deal with room modes https://mehlau.net/audio/multisub_geddes/
THX reference is 115 dB/listening position [Lp] and while not completely true in a typical size HT room, ideally need to add 6 dB for every doubling of distance between woofer, LP to ensure having plenty of dynamic headroom, so theoretically 121 dB/2 m, 127 dB/4m, etc., but at least add 3 dB/ea. unless in room measurements indicate less.
If all drivers are set to 'small', then start at ~122 dB IIRC.
Re what to build; between Chris's local experience and how many movies have significant output below 20 Hz, recommend ~0.6 Qtc sealed as a compromise between transient perfect [0.5] and an ideal room's 12 dB/octave gain curve [0.707] since few rooms can/will be sealed up, rigid enough to do it down low and at least [3] spread around the room at specific points to get both sufficient peak SPL at low distortion and also average out room modes to achieve a 'flat' enough in room response below the sub's XO's HF -24 dB point [160 Hz if a typical 80 Hz/4th order XO].
speaker layout considerations: INNOVATION | Harman
VLF in movies, etc.: The Low Frequency Content Thread (films, games, music, etc) - Bass Content - Data-Bass Forums
GM
I just simmed a LAB12 with WinISD v0.7.0.950 & the Power/Xmax/FreqRes/AirVel/ etc ALL respond & show the effect of using a Linkwitz Transform
You both need to update the program
Didn't realise I was using an out-dated version! (7.0.900)
The LAB12s definitely count as long-throw 12"s.
Regarding air velocities in ports, you've got to remember that the velocity will only reach that when you're using a sine wave at the given power input. Ask yourself if you'll really be putting that much power in, and if it's ever likely to be in the form of sine waves.
It could well be that a movie with plenty of explosions at full power will have enough content to give port noises. I once did a big ported box tuned down at 18Hz for a JBL GTO1214 (another long-throw 12"). Port was around 50mm by 200mm. It was absolutely fine even at fairly high listening levels, but movie demos at full power did result in wind noises.
To get around port issues, have a read up on passive radiator subwoofers. Te extra cones might add a little to the project costs, but will minimise cabinet size compared to the ported boxes, where a lot of the box ends up being port!
Chris
GM, I'm surprised by those numbers! Like I said I have two TH12 tapped horns, two THAM 15 tapped horns, and I'm not entirely sure I've ever pushed them to 125dB having a good ol' house party! with regards to transmission lines, they do look like a very interesting prospect but perhaps a bit more complex than I'm looking for right now!
Scott, those T-lines look like a very good way of keeping the footprint small, perhaps a bit too oddball for my lounge at the moment
This is nice to know! I might model up a few new enclosures (with this new version of WinISD) and flip a coin.
Actually I'll build 3... one isobarik tuned low, one sealed and one ported. load them all up and see which I prefer.
By way of measuring; I have a Behringer ECM8000 for EQ with a ultracurve 2496, what else do I need to get off the ground and make some plots for in room response?
Scott, those T-lines look like a very good way of keeping the footprint small, perhaps a bit too oddball for my lounge at the moment
This is nice to know! I might model up a few new enclosures (with this new version of WinISD) and flip a coin.
Actually I'll build 3... one isobarik tuned low, one sealed and one ported. load them all up and see which I prefer.
By way of measuring; I have a Behringer ECM8000 for EQ with a ultracurve 2496, what else do I need to get off the ground and make some plots for in room response?
I have been playing with the lab12 and winisd a few weeks ago:
Maybe a can do it all sub which you can adjust to the use and location placed?
A 100 liter netto vented box with 4 33.5cm (somewhat shorter in reality) x 7cm round reflex ports?
Bij closing ports you go from 33 to 30.5-25-17.6 Hz boxtuning; from a big 4,5db 40hz boost party sub to HT sub and can even be used fully closed. Portnoise might be an issue with 1 or 2 port open, but you are not going to run it that loud in these modes.
Maybe a can do it all sub which you can adjust to the use and location placed?
A 100 liter netto vented box with 4 33.5cm (somewhat shorter in reality) x 7cm round reflex ports?
Bij closing ports you go from 33 to 30.5-25-17.6 Hz boxtuning; from a big 4,5db 40hz boost party sub to HT sub and can even be used fully closed. Portnoise might be an issue with 1 or 2 port open, but you are not going to run it that loud in these modes.
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I started btw with the idea to design a light/ portable and versatile sub, thinking of a 120liter pe barrel (conga style) with a reinforced bottom and top and placing the speaker on top/bottom or in front. I would place 1 port above the driver for ventilating the warm air out. 2 below the driver and 1 on the back/bottom was my idea for the others.
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I'm currently looking to downsize my subs and have pretty much decided on using the lab12's in 125L boxes tuned to ~17Hz. They will have a 4th order high pass on them around 14Hz and use a 1" x 12" slot port.
I have 4 drivers and they will each be powered by a 300W amp channel.
Would be interested to see a transmission line sim of similar size.
hth,
Rob.
I have 4 drivers and they will each be powered by a 300W amp channel.
Would be interested to see a transmission line sim of similar size.
hth,
Rob.
Attachments
This sounds like a neat idea, how would you close off the ports? Big ol' corks? stuffed sock?
I think 100L Net is probably as big as I'd like to go, the impression I get is the Lab12 doesn't go low very well in smaller enclosures.
Might be a while before I build anything, not a lot of time or build resources at the moment.
Cheers all
Note those subwoofers were designed using obsolete methodology.
For reference purposes, see Classic TL Design -- Jon Risch
100L seems to be it's sweet spot.
Maybe there are pvc endcaps or even screw-on endcaps available otherwise a plug with cork or rubber (bicycle inner tire) will do.
Maybe the top part of drinking cup/mok (?- for kids to take something to drink with them to school) with a screw on lid, is an idea to use to glue to the pvc pipe. They are sold in all kinds of colours and shapes quite cheaply.
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