Ideally, I'd have a single dual-coil driver - the amplifier I have will operate bridged into 8ohm, or 4ohm/ch.
Unfortunately, it seems that (having poked around on eBay and a few other sites) only the SVC version is available to me.
I suspect ~300w into the SVC version will still be plenty enough, though, so I'm not complaining.
Cheers 18Hurts
Chris
Unfortunately, it seems that (having poked around on eBay and a few other sites) only the SVC version is available to me.
I suspect ~300w into the SVC version will still be plenty enough, though, so I'm not complaining.
Cheers 18Hurts
Chris
The driver arrived today, so I went out and bought one of those pre-fab 35L cabinets - the simulated response is reasonable, and a proper cabinet will be a while off yet.
So far, I'm rather impressed.
Build quality is good, and it goes pretty loud.
I'll pick up some T-nuts tomorrow, as its currently just sat on the foam sealing ring. Still flaps papers overhanging my desk though
I'll take some pictures later - its time to head to the pub.
Chris
So far, I'm rather impressed.
Build quality is good, and it goes pretty loud.
I'll pick up some T-nuts tomorrow, as its currently just sat on the foam sealing ring. Still flaps papers overhanging my desk though
I'll take some pictures later - its time to head to the pub.
Chris
Quick update..
My stereo (as usual) got used for a flat party last night.
Put one speaker plus the subwoofer outside my door, and it was loud and clear everywhere - the bass even made it across the corridor into the shared kitchen/lounge (something that my smaller speakers couldn't manage - it seems most of the low end goes down the corridor).
So, the next step: make it hit 20Hz!
For a ported design, the diameter (and length) of the port would have to be huge to keep air velocity below 20m/s: a pair of 10cm dia vents would be just over 1m long each to get a 20Hz tuning at ~100L cabinet volume.
I could try using these passive radiators, but WinISD reckons that, to keep PR excursion sane, I'd need 50 (yes, fifty) of them.
I think there's an error in the simulation - I'd guess a pair of those PRs would be sufficient, but I have no direct experience with PRs, so if someone could shed some light over here, that'd be useful.
I also tried getting something usable out of Hornresp. A 2:1 compression ratio TQWT (I think that's what this is) comes out quite well, though folding it will be a challenge. For a 240cm^2 cross sectional area, and a 30cm diameter driver, the depth must be 8cm.
The driver's mounting depth is 16.5cm, so I suspect something clever must be done to work around this, if the design is viable.
I have attached some screenshots from Hornresp - comments/criticism welcome.
Cheers
Chris
My stereo (as usual) got used for a flat party last night.
Put one speaker plus the subwoofer outside my door, and it was loud and clear everywhere - the bass even made it across the corridor into the shared kitchen/lounge (something that my smaller speakers couldn't manage - it seems most of the low end goes down the corridor).
So, the next step: make it hit 20Hz!
For a ported design, the diameter (and length) of the port would have to be huge to keep air velocity below 20m/s: a pair of 10cm dia vents would be just over 1m long each to get a 20Hz tuning at ~100L cabinet volume.
I could try using these passive radiators, but WinISD reckons that, to keep PR excursion sane, I'd need 50 (yes, fifty) of them.
I think there's an error in the simulation - I'd guess a pair of those PRs would be sufficient, but I have no direct experience with PRs, so if someone could shed some light over here, that'd be useful.
I also tried getting something usable out of Hornresp. A 2:1 compression ratio TQWT (I think that's what this is) comes out quite well, though folding it will be a challenge. For a 240cm^2 cross sectional area, and a 30cm diameter driver, the depth must be 8cm.
The driver's mounting depth is 16.5cm, so I suspect something clever must be done to work around this, if the design is viable.
I have attached some screenshots from Hornresp - comments/criticism welcome.
Cheers
Chris
Attachments
a 20hz tuned ported box will be smaller but less total output than a tapped horn.
And it is tough tuning that low in a small-ish box with decent port diameter without chuffing.
Then again, a 20hz tapped horn usually gets really nasty around 70hz, eventhough your pics look good.
PR's work very well in that application (small box tuned waaaaayyyyy low), but ideally the pr moves 3 times the air, so use tripple the cone area (passive radiator) for the same xmax of subwoofer, or use a 24mm xmax pr with an 8mm xmax subwoofer.
I've no clue on the tqwt
And it is tough tuning that low in a small-ish box with decent port diameter without chuffing.
Then again, a 20hz tapped horn usually gets really nasty around 70hz, eventhough your pics look good.
PR's work very well in that application (small box tuned waaaaayyyyy low), but ideally the pr moves 3 times the air, so use tripple the cone area (passive radiator) for the same xmax of subwoofer, or use a 24mm xmax pr with an 8mm xmax subwoofer.
I've no clue on the tqwt
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Sometimes better than more Xmax is more surface area. 2 isobaric sets of 12"s (4 total) fits in the box of 1 12", with quadruple the power handling and the displacement of an 18", as well as lower distortion (if you can keep the volume in the clamshell low).
You can even put them on opposite sides of the enclosure for force cancellation. I don't know of cheap 12"s on your side of the pond, I used Zalytron's 1201PL and am very happy. They were like $150 shipped for a case of 8.
You can even put them on opposite sides of the enclosure for force cancellation. I don't know of cheap 12"s on your side of the pond, I used Zalytron's 1201PL and am very happy. They were like $150 shipped for a case of 8.
Do what I did- Sofa Subwoofer!!!
http://www.diyaudio.com/forums/subwoofers/205299-sofa-subwoofer-3.html
It was quite cheap, around 140 including drivers, mdf, hardware, and upholstery materials
It can hit 120 dB in room (which is gooooood fun) down real low. 20Hz rattles everything in my room
Also the size doesn't matter because you can't even tell that it's there. People literally have no idea that it is a sub when they come into my room
http://www.diyaudio.com/forums/subwoofers/205299-sofa-subwoofer-3.html
It was quite cheap, around 140 including drivers, mdf, hardware, and upholstery materials
It can hit 120 dB in room (which is gooooood fun) down real low. 20Hz rattles everything in my room
Also the size doesn't matter because you can't even tell that it's there. People literally have no idea that it is a sub when they come into my room
4x12" in isobaric is not equal to an 18" in displacement in my book. The Isobaric loading will make movement easier for the drivers, and therefore make it seem like the box is bigger, but you will run out of xmax faster.
The sd of a 18" can be around 1190sqcm at ~8mm xmax, the sd of a 12" can be around 550sqcm at ~6mm xmax. You will probably loose some power handling and max spl over this. Nothing wrong with Isobaric, but there's always a tradeoff no matter what you go for.
That's apples to oranges if I ever saw such a thing.
SD of an 18" is nearly identical to that of 2 12"s. If the xmax is the same then they should have the same max output, but clearly if the 18" has more xmax then the comparison is no longer valid...
But really guys, who cares about surface area, it's all about volume displacement.
I would take a 12" w/ 10mm xmax over a 21" w/ 1mm or a 3" woofer w/ 6" of xmax.
Though as a side not a 3" woofer that could move 12" peak to peak would be damn cool
SD of an 18" is nearly identical to that of 2 12"s. If the xmax is the same then they should have the same max output, but clearly if the 18" has more xmax then the comparison is no longer valid...
But really guys, who cares about surface area, it's all about volume displacement.
I would take a 12" w/ 10mm xmax over a 21" w/ 1mm or a 3" woofer w/ 6" of xmax.
Though as a side not a 3" woofer that could move 12" peak to peak would be damn cool
Not sure if I made this clear earlier - I have the driver - its a JBL GTO1214, as recommended by 18Hurts. Xmax = 14.5mm.
Its currently sat in one of those generic 35L sealed cabinets (Q= ~0.8)
kctess5, I like the look of that!
Once I move out of student flats into a shared house, that's something I'll consider building.
Norman, I know the Kraken 112 can easily go lower and louder than the ported box, but I also know the Kraken is massive - I'm trying to balance size against performance - about 100L seems optimum, though it's still large.
I appreciate the advice about the PRs: it looks like the ones I have available aren't suitable, but I'll keep looking as I think that'll give me the best chance of getting what I'm looking for, though I haven't ruled ports out completely.
Cheers
Chris
An externally hosted image should be here but it was not working when we last tested it.
Its currently sat in one of those generic 35L sealed cabinets (Q= ~0.8)
kctess5, I like the look of that!
Once I move out of student flats into a shared house, that's something I'll consider building.
Norman, I know the Kraken 112 can easily go lower and louder than the ported box, but I also know the Kraken is massive - I'm trying to balance size against performance - about 100L seems optimum, though it's still large.
I appreciate the advice about the PRs: it looks like the ones I have available aren't suitable, but I'll keep looking as I think that'll give me the best chance of getting what I'm looking for, though I haven't ruled ports out completely.
Cheers
Chris
Telarc's recording of Tchaikovsky's 1812 Overture
To make the recording they actually fired off period correct cannons, of various sizes & charges. The cannons were digitally recorded & then edited into the the music, in the correct places. The largest of the cannons broke windows a mile away!!!
MLStrand56
The Telarc DDD CD of Tchaikovsky's 1812 Overture. It has subharmonics that go down to 4 Hz (that's Not a typo!)
To make the recording they actually fired off period correct cannons, of various sizes & charges. The cannons were digitally recorded & then edited into the the music, in the correct places. The largest of the cannons broke windows a mile away!!!
MLStrand56
That's apples to oranges if I ever saw such a thing.
SD of an 18" is nearly identical to that of 2 12"s. If the xmax is the same then they should have the same max output, but clearly if the 18" has more xmax then the comparison is no longer valid...
But really guys, who cares about surface area, it's all about volume displacement.
I would take a 12" w/ 10mm xmax over a 21" w/ 1mm or a 3" woofer w/ 6" of xmax.
Though as a side not a 3" woofer that could move 12" peak to peak would be damn cool
Volume displacement is all well and good but I subscribe to the "larger area moving less" school, remember that everything a sub does, it does worse the more it moves.
I totally agree, but that is more of a sound quality issue. As far as total output goes two speakers with the same VD will have the same max output (assuming sealed).
But as you say I try to maximize cone surface area so that they will have to move less, just to make sure there are no suspension noises or anything. I generally think that if you can see your drivers moving while at normal listening levels you don't have enough surface area. ... war volume is another issue however
Hi Chris661
I noticed, that you simulated one of bjorno's favorites in Post# 23, the tapped quarter wave pipe (TQWP). I've been messing around with this driver (JBL GTO1214TD) in Hornresp for a while, and have a simulation with drawing using this enclosure type w/ a long L12 (offset driver). I'll attach it for you information, you might find it interesting (you are correct, it's hard to fit the driver into that shallow a duct). Bjorno is the expert on these enclosures, he suggested doubling and tripling up on the driver baffle in another thread.
Also, for PR boxes I like Bagby's software Loudspeaker Design Software.
Three of your 12"PRs would work, but they would take quite a bit of additional cone weight.
For simplicity it's just hard to beat a simple BR.
Regards,
I noticed, that you simulated one of bjorno's favorites in Post# 23, the tapped quarter wave pipe (TQWP). I've been messing around with this driver (JBL GTO1214TD) in Hornresp for a while, and have a simulation with drawing using this enclosure type w/ a long L12 (offset driver). I'll attach it for you information, you might find it interesting (you are correct, it's hard to fit the driver into that shallow a duct). Bjorno is the expert on these enclosures, he suggested doubling and tripling up on the driver baffle in another thread.
Also, for PR boxes I like Bagby's software Loudspeaker Design Software.
Three of your 12"PRs would work, but they would take quite a bit of additional cone weight.
For simplicity it's just hard to beat a simple BR.
Regards,
Attachments
Now there's a clever thought - I would never have thought of that. Cheers!
There seems to be something odd happening with Hornresp - when I simulate your design in 0.5pi space, there's a large peak/dip combo at 60Hz, where there's only a tiny notch in 2pi space.
Nothing whacky on the impedance chart, and the displacement shows a tiny ripple at 60Hz.
Very strange.
The long offset does appeal, though - it'd reduce the height compared to the long L23 design I was considering: the only space for this is under my desk, and I'm not sure a 2.5m long cabinet would fit. No tape measure to hand, either.
Using myself as a ruler, I estimate about 5'8" length available.
The full-height option of your design would fit, but I'd probably build it with the top section removed to keep the build easy.
As you say, though, a ported box would be the simplest option, and will probably be the one I go for - PVC tubing is cheap.
Chris
PS - http://www.diyaudio.com/forums/subw...own-2x12-th-kraken-212-th-10.html#post2770682 - Kracken 112 for anyone that's interested.
I did not finish up my post because I had to run off at an emergency and just hit the post button before it was finished, I apologize for any inconveniance.
My final point was, 4 decent 12" will cost between 300 to 550 usd pending on quality and possible discounts. 4 drivers will also complicate the build nedlessly, two of these costs 250 usd and will give probably better response:
Dayton Audio DCS450-4 18" Classic Subwoofer 4 Ohm 295-475
Less work, more play.
Jeez, I keep having to run around all over here.
Sorry about the bump:
Isobaric:
"There is, of course, a penalty involved. Whenever you use isobaric loading, you are sacrificing 3dB of efficiency compared to a single driver in twice the air space. In practical terms, this is not usually a big deal since the powerhandling is doubled (two speakers instead of one), so the end result is about the same output as the single driver in the bigger box, assuming you double the amplifier power."
You get more power handling, granted, but you do not get more xmax. Also double power handling means very little, less money to waste on beer. A low power quality design can beat a high power poor design at the same cost.
Sorry about the bump:
Isobaric:
"There is, of course, a penalty involved. Whenever you use isobaric loading, you are sacrificing 3dB of efficiency compared to a single driver in twice the air space. In practical terms, this is not usually a big deal since the powerhandling is doubled (two speakers instead of one), so the end result is about the same output as the single driver in the bigger box, assuming you double the amplifier power."
You get more power handling, granted, but you do not get more xmax. Also double power handling means very little, less money to waste on beer. A low power quality design can beat a high power poor design at the same cost.
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