Linesource asked:
I'm looking for help in doing some measurements. Exactly how does one measure a dipole sub? Nearfield measurements don't give the picture, Farfield measures like mush, and gated is right out!
Right now I'm just going by ear. I built an active cross that provides a 2nd order crossover with variable gain, frequency, dipole correction and hi-pass filter. Current setting are for a 2nd order lowpass between 75 and 100 Hz. Configured for 8 Ohms, the Lambda 15s have a QTS of .9, so I can make do with a small amount of boost cutting in at about 75 Hz.
Critical listening does not indicate any bad resonances within the pass-band, so I'm hoping I lucked out with the design and can avoid a notch filter.
Until I can measure this thing correctly, I can't really judge the effect of the k-slot, but subjectively, the bass seems quicker and better integrated than the same drivers mounted on a rectangular baffle w/rear wings.
Nuuk asked:
Hehe. Yah, the drivers were purchased before I decided on dedicated sub. Kind of a waste of bandwidth, but they do sound GREAT.
I am only using one. I cringe thinking of building another. This thing is BIG. One provides more than enough SPL, and the ear cannot located the sub.
I actually have the material to build another. Anybody want one?
I'm looking for help in doing some measurements. Exactly how does one measure a dipole sub? Nearfield measurements don't give the picture, Farfield measures like mush, and gated is right out!
Right now I'm just going by ear. I built an active cross that provides a 2nd order crossover with variable gain, frequency, dipole correction and hi-pass filter. Current setting are for a 2nd order lowpass between 75 and 100 Hz. Configured for 8 Ohms, the Lambda 15s have a QTS of .9, so I can make do with a small amount of boost cutting in at about 75 Hz.
Critical listening does not indicate any bad resonances within the pass-band, so I'm hoping I lucked out with the design and can avoid a notch filter.
Until I can measure this thing correctly, I can't really judge the effect of the k-slot, but subjectively, the bass seems quicker and better integrated than the same drivers mounted on a rectangular baffle w/rear wings.
Nuuk asked:
Hehe. Yah, the drivers were purchased before I decided on dedicated sub. Kind of a waste of bandwidth, but they do sound GREAT.
I am only using one. I cringe thinking of building another. This thing is BIG. One provides more than enough SPL, and the ear cannot located the sub.
I actually have the material to build another. Anybody want one?
Erik, I've been thinking about dipole bass as well recently.
How do you calculate the dimensions for such a subwoofer, especially for the slot-loading 'wings'.
Speaking of which, how do you BUILD the wings?
Also, with the two drivers out of phase, doesn't that tower rock at all? I'm interested in building one of those with Tumult drivers (requires lots of EQ because of low Qt, BUT has incredible displacement and very low distortion) The motors are extremely heavy (50 pounds) and the moving mass is about 4 times that of the Lamda dipoles.
How do you calculate the dimensions for such a subwoofer, especially for the slot-loading 'wings'.
Speaking of which, how do you BUILD the wings?
Also, with the two drivers out of phase, doesn't that tower rock at all? I'm interested in building one of those with Tumult drivers (requires lots of EQ because of low Qt, BUT has incredible displacement and very low distortion) The motors are extremely heavy (50 pounds) and the moving mass is about 4 times that of the Lamda dipoles.
Gridstop -
All dimentions were derived from the drivers. I purchased plywood 1/2 cylinders just big enough to contain the drivers, which was a 20.5 inch diameter pipe of 5/8th plywood.
The construction was complicated. I have a gallery on AudioCircle that has a pictoral walkthrough of the construction.
http://www.audiocircle.com/circles/...ame=gallery&file=index&include=view_album.php
The baffle hardly moves until the woofers are cranking through an inch of travel. The wings vibrate slightly with increased air motion. I'm probably going to dampen them eventually. That's why I'm unlikely to veneer more than the top most portion of the inside wings.
DJNUBZ -
Take a look at the speaker that lauched a dozen clones...
Scroll down halfway.
http://www.dietiker-humbel.ch/micromag.htm
All dimentions were derived from the drivers. I purchased plywood 1/2 cylinders just big enough to contain the drivers, which was a 20.5 inch diameter pipe of 5/8th plywood.
The construction was complicated. I have a gallery on AudioCircle that has a pictoral walkthrough of the construction.
http://www.audiocircle.com/circles/...ame=gallery&file=index&include=view_album.php
The baffle hardly moves until the woofers are cranking through an inch of travel. The wings vibrate slightly with increased air motion. I'm probably going to dampen them eventually. That's why I'm unlikely to veneer more than the top most portion of the inside wings.
DJNUBZ -
Take a look at the speaker that lauched a dozen clones...
Scroll down halfway.
http://www.dietiker-humbel.ch/micromag.htm
Hmm, I wonder how available (and expensive) those cylinders will be in my area. (Western Wisconsin)
The curve you traced on the wings... is that a particular ratio or anything? Or is it one of those things where, there probably IS an ideal, but even just winging it will get you close enough you'll notice a benefit?
I tend to paint, not veneer, so that simplifies things a bit for me
Couldn't you build two simicircles to support the wings between the two drivers? (Mostly hollowed out of course)
The curve you traced on the wings... is that a particular ratio or anything? Or is it one of those things where, there probably IS an ideal, but even just winging it will get you close enough you'll notice a benefit?
I tend to paint, not veneer, so that simplifies things a bit for me
Couldn't you build two simicircles to support the wings between the two drivers? (Mostly hollowed out of course)
GRIDSTOP -
West coast distributer for the 1/2 cylinders in Anderson International Trading (www.aitwood.com). They stock a 20.25 diameter by 102 inch piece that can be cut in two and shipped UPS. This is the equivalent of the two pieces I picked up on the east coast.
As a subwoofer, the eliptical opening is far to small to have any sound reinforcement effect, so the curvature is not critical. Mine was sized by using the maximum length and leaving a one inch gap between the panels.
For me, the dampened baffle and the rigid coupling to the base is enough to contain the motion of the drivers. If your moving mass will be much greater, you should consider a more elaborate bracing system.
You mean like this?
West coast distributer for the 1/2 cylinders in Anderson International Trading (www.aitwood.com). They stock a 20.25 diameter by 102 inch piece that can be cut in two and shipped UPS. This is the equivalent of the two pieces I picked up on the east coast.
As a subwoofer, the eliptical opening is far to small to have any sound reinforcement effect, so the curvature is not critical. Mine was sized by using the maximum length and leaving a one inch gap between the panels.
For me, the dampened baffle and the rigid coupling to the base is enough to contain the motion of the drivers. If your moving mass will be much greater, you should consider a more elaborate bracing system.
You mean like this?
Attachments
Ahh yep, that is what I was thinking of.
Anderson International also sells fibreboard cylinders. I wonder if they are closer to MDF or to particle board. If they were more dense like MDF perhaps with some bracing (like you pictured) they would work. Save a lot of money as well.
I'll call them up sometime this week. Also need to call Dan at Adire and ask him about dipole Tumults. I'll let you guys know if anything comes of this
EDIT: Ahh ,my mistake. I see what you mean, you bought a single 102" long half cylinder (180 degrees) and had them cut it in half so you had two 51" long halves delivered. Only $135 as well, not bad at all.
Anderson International also sells fibreboard cylinders. I wonder if they are closer to MDF or to particle board. If they were more dense like MDF perhaps with some bracing (like you pictured) they would work. Save a lot of money as well.
I'll call them up sometime this week. Also need to call Dan at Adire and ask him about dipole Tumults. I'll let you guys know if anything comes of this
EDIT: Ahh ,my mistake. I see what you mean, you bought a single 102" long half cylinder (180 degrees) and had them cut it in half so you had two 51" long halves delivered. Only $135 as well, not bad at all.
Gridstop,
Tape Ease in Wisconsin has the 1/2 cylinders. It's a good place to buy veneer as well.
http://www.tapeease.com/2rounds.htm
Tape Ease in Wisconsin has the 1/2 cylinders. It's a good place to buy veneer as well.
http://www.tapeease.com/2rounds.htm
I am making progress with my Goodmans 201's in open baffles since disconnecting the piezo tweeters which for some reason I have yet to discover, reduced the transparency. (I am wondering if the phase of the speaker was reversed during it's rebuild)
Anyway, I have what is best described as 'one-note' bass with the bass virtually doing it's own thing. Any suggestions as to what could be causing this?
Anyway, I have what is best described as 'one-note' bass with the bass virtually doing it's own thing. Any suggestions as to what could be causing this?
Nuuk said:I am making progress with my Goodmans 201's in open baffles since disconnecting the piezo tweeters which for some reason I have yet to discover, reduced the transparency. (I am wondering if the phase of the speaker was reversed during it's rebuild)
Anyway, I have what is best described as 'one-note' bass with the bass virtually doing it's own thing. Any suggestions as to what could be causing this?
What are the dimentions of your baffles?
expriment with the positioning of the baffles and listening position, I had to re-organise my lounge room to get my baffles sounding right.
It's also possible that the material the baffle is made of is resonating at a given frequency and radiating more bass than the driver it's self (hence the "one note" bass) In that case the baffle will need to be damped or stiffened (braced) or both.
I had far less resonance based problems with my baffles after I went sick with bracing on them.
Thanks Volenti,
The baffles are four feet tall by two feet wide (about 1.2 metres by 0.6 metres) and have 12 inch (300mm) wings.
They are only temporary to see how the drivers perform and probably could do with a lot of bracing which I will now add.
I have moved the baffles forward of the rear wall a little more and it has improved things slightly. Obviously lots more experimenting to do!
The baffles are four feet tall by two feet wide (about 1.2 metres by 0.6 metres) and have 12 inch (300mm) wings.
They are only temporary to see how the drivers perform and probably could do with a lot of bracing which I will now add.
I have moved the baffles forward of the rear wall a little more and it has improved things slightly. Obviously lots more experimenting to do!
No, I won't give up on anything if it makes some sort of music! What I hear so far, makes me think that there is a decent speaker in this project for the want of a bit more work.
Besides that, spending £120 to have the 201's rebuilt makes them rather indisposable!
Is WMTWM - woofer-mid-treble-woofer-mid?
Very nice and even possible WAF for such big speakers!
I have now rebuilt my temporary baffles with a lump of marble attached to each baffle and with the driver positions lowered by 9 inches. The results are just what I wanted and the sound has convinced me to try some glass baffles if the price is not too high.
I have now rebuilt my temporary baffles with a lump of marble attached to each baffle and with the driver positions lowered by 9 inches. The results are just what I wanted and the sound has convinced me to try some glass baffles if the price is not too high.
One more question on my OB experiment.
I am currently using piezo tweeters with the Goodmans 201s to give a bit more top end. I bought these on the recommendation of KYW but I was wondering if there was a better sounding alternative that I should consider.
The tweeters come in at about 10Khz.
I am currently using piezo tweeters with the Goodmans 201s to give a bit more top end. I bought these on the recommendation of KYW but I was wondering if there was a better sounding alternative that I should consider.
The tweeters come in at about 10Khz.
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