Cutting holes
For jig saw hole cutting there is a technique that works for me. I call it the Zen cutting technique.
You most become one with the line. You are not the circle - you are the line.
Worrying about the cut and the circle always gives me a bad cut. So I just relax and flow with the line. Easy. Results are quite good. No thinking or worrying.
For jig saw hole cutting there is a technique that works for me. I call it the Zen cutting technique.
You most become one with the line. You are not the circle - you are the line.
Worrying about the cut and the circle always gives me a bad cut. So I just relax and flow with the line. Easy. Results are quite good. No thinking or worrying.
Zen cutting? Hmm, I looked for that at Home Depot but they said they were out of the blades right now.
I did pick up 2 - 2' x 4' pieces of 3/4" oak ply. Nice, heavy wood with a manly feel.... It was tempting to go with pine, but only $3 cheaper per piece. Is 3/4" too thick or just right for resonance? Also, I can't fit 4' x 4' pieces in the "listening room", so I'm hoping the 2' x 4' oriented vertically will work okay.
I did pick up 2 - 2' x 4' pieces of 3/4" oak ply. Nice, heavy wood with a manly feel.... It was tempting to go with pine, but only $3 cheaper per piece. Is 3/4" too thick or just right for resonance? Also, I can't fit 4' x 4' pieces in the "listening room", so I'm hoping the 2' x 4' oriented vertically will work okay.
Hey Bob, The oak should be fine, looks better than pine I think.
3/4 should be fine. I don't think the baffle can be too thick, unless the hole becomes a tube. Idealy, the baffle should not radiate any sound, the stiffer and heavier the better. At 2x4, you may want to place a brace just below the speaker. I get a bit of radiation of 600mm x 45mm baffles on my corner enclosures which I need to address
A vibrating baffle not only adds distortion, but reduces efficiency, as the baffle is vibrating out of phase with the cone.
At 2x4, plus the sides,you will have a decent OB.
A tip: A "shelf" at the top of you baffle will enhace the lows. It increases the shortest distance from front to rear, which determines the bass roll off point. It may also prevent something falling on the cone.
Cheers,
Geoff
3/4 should be fine. I don't think the baffle can be too thick, unless the hole becomes a tube. Idealy, the baffle should not radiate any sound, the stiffer and heavier the better. At 2x4, you may want to place a brace just below the speaker. I get a bit of radiation of 600mm x 45mm baffles on my corner enclosures which I need to address
A vibrating baffle not only adds distortion, but reduces efficiency, as the baffle is vibrating out of phase with the cone.
At 2x4, plus the sides,you will have a decent OB.
A tip: A "shelf" at the top of you baffle will enhace the lows. It increases the shortest distance from front to rear, which determines the bass roll off point. It may also prevent something falling on the cone.
Cheers,
Geoff
Geoff H said:
Greets!
Thanks, the theory is correct since a perfect circle has an infinite number of identical standing waves that causes sharp peaks/nulls in the response while a random circle has so many different frequencies that they provide a much smoother response. In the case of a tapered cutout though, the difference is of course much less pronounced due to its intrinsically more rapid decay rate and why I noted 'in theory'.
Anyway, I haven't been able to follow the boards for awhile now and I didn't find your Wharfdales in a quick search, so not sure what 'better' you're referring to.
I did find your Cohen book reference though. Wow! The prices folks are asking for their copy(s)! According to this inflation calculator, a NOS copy should only retail for ~$29.26, which is already pretty pricey IMO for a paperback: http://inflationdata.com/inflation/Inflation_Rate/InflationCalculator.asp#results
Until the driver's Qts gets above ~1, sheet metal is overall a superior cab material since it's much stiffer, which due to its high Fs can be damped with much less materials/effort. I use to have access to various size/construction electrical equipment boxes 'on the cheap' that made excellent speaker cabs with built-in hinged baffles
, though obviously their industrial 'look' made them only suitable for basic bachelor pad, garage, shop, or outdoor apps. Second best were the very pricey injection molded 'explosion proof' Nema 4X fiberglass composite construction cabs, though these needed either fiberglass repairing and/or a bolt-on baffle since they only got scrapped if the order changed enough that we couldn't adapt them to the revised specs.Ditto on impatience! More often than not, my attention span can rival a 2 yr old's, so if the 'client' wanted 'pretty', they either had to do it or at least put a lot of 'sweat equity' in them helping me. Maybe this is why I never had to deal with, or hear about, any WAF/SAF type issues since they typically were the ones making/doing the finishing decisions. Early on, I did do one nice octagon shaped, Ga. marble inlaid set of Mediterranean style end-tables for my mom though and now wish I had bothered to take pics since they are long gone...........
GM
I almost bought 6" wide boards for the wings, then realized they aren't wide enough to stabilize the baffle. Looks like 10" to 12" wide will work much better. Also, solid wood for the wings will atttach better than ply, thinking screws will split out the ply. A base "foot" and top "shelf" should round out the rear.
Here's that post:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1062175#post1062175
There are a few to go through. Did I write all those!
Funny thing about the whole size. The guy that modified those Wharfies had been experimenting with plywood horns on cone drivers.
Some of the best drivers, for horn loading, he found at that time were 3x5" and 5x7" Rolas from mantle radios.
Bob, go for the bigger wings. BIB.
Geoff.
Edit: Just checked that link. The pics are on the previous page.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1062175#post1062175
There are a few to go through. Did I write all those!
Funny thing about the whole size. The guy that modified those Wharfies had been experimenting with plywood horns on cone drivers.
Some of the best drivers, for horn loading, he found at that time were 3x5" and 5x7" Rolas from mantle radios.
Bob, go for the bigger wings. BIB.
Geoff.
Edit: Just checked that link. The pics are on the previous page.
an old console
check out the parts in this one
http://cgi.ebay.com/ws/eBayISAPI.dl...ndexURL=0&photoDisplayType=2#ebayphotohosting
check out the parts in this one
http://cgi.ebay.com/ws/eBayISAPI.dl...ndexURL=0&photoDisplayType=2#ebayphotohosting
Attachments
Simon, Because the baffle still reaches the floor, and the distance is small compared to the f where you want the 3 db gain, you still have it.
The idea of placing the driver high is to allow the important "extended" midrange away from carpet or hard surfaces, except walls.
My definition of mid-range is from about 150 to 10K. See my posts in other threads over the last week or so.
Cheers,
Geoff.
PS. Start with this one. http://www.diyaudio.com/forums/showthread.php?postid=1079783#post1079783
It just about warrants its own subject.
The idea of placing the driver high is to allow the important "extended" midrange away from carpet or hard surfaces, except walls.
My definition of mid-range is from about 150 to 10K. See my posts in other threads over the last week or so.
Cheers,
Geoff.
PS. Start with this one. http://www.diyaudio.com/forums/showthread.php?postid=1079783#post1079783
It just about warrants its own subject.
My Console OBs
I wonder how Bob's doing with his project?
Just for fun, I picked up a set of Heppner console drivers said to be from an RCA console, tho they say Magnavox on them. Also supposed to be Alnico, but I don't know how to verify that.
Anyhow, they look nice and are in great shape. Two 12" woofers and two 1" horns. Very simple 3 element crossover - 1 cap, 1 inductor, 1 resistor. The 12s have a stamped frame and are pretty heavy. And oddly enough, they smell like..... makeup. Max Factor makeup. Weird.
So I''ll put them on a baffle to have a listen and post photos. Will try a line level filter to compensate for the OB rolloff. Should be fun.
I wonder how Bob's doing with his project?
Just for fun, I picked up a set of Heppner console drivers said to be from an RCA console, tho they say Magnavox on them. Also supposed to be Alnico, but I don't know how to verify that.
Anyhow, they look nice and are in great shape. Two 12" woofers and two 1" horns. Very simple 3 element crossover - 1 cap, 1 inductor, 1 resistor. The 12s have a stamped frame and are pretty heavy. And oddly enough, they smell like..... makeup. Max Factor makeup. Weird.
So I''ll put them on a baffle to have a listen and post photos. Will try a line level filter to compensate for the OB rolloff. Should be fun.
Yeah, I hope Bob's OK. I just sent him an email.
The new speakers sound good. Just can't find stuff like that here.
The Ausie Magnavox's had pot style alnicos, sometimes refered to as W, due to the cross section. Pretty easy to identify ceramic. Black. Usually Alnico were painted, or cad coated.
The W or pot was, I think, the best of the lot, less junctions of metal in the magnetic circuit, but tricky to machine.
BTW, never dissmantle an alnico magnet assy, unless you have access to a magnetiser.
Geoff
The new speakers sound good. Just can't find stuff like that here.
The Ausie Magnavox's had pot style alnicos, sometimes refered to as W, due to the cross section. Pretty easy to identify ceramic. Black. Usually Alnico were painted, or cad coated.
The W or pot was, I think, the best of the lot, less junctions of metal in the magnetic circuit, but tricky to machine.
BTW, never dissmantle an alnico magnet assy, unless you have access to a magnetiser.
Geoff
Bobs OK. Just got a reply. No sawn off fingers, only bruises.
his reply;
"Good Morning (well it is here anyway!) Geoff,
Thanks for checking on me. My wicked ways with buying tubes via PayPal finally caught up with me when the wife got the credit card statement. Ouch! I was in the midst of getting the wings for the OB, but have to cool off for awhile to maintain the peace. I'll be back to it soon and post my findings. Take care and have a safe and happy Holiday Season.
Bob"
Me thinks he had better do some good Christmas shopping.
Geoff.
his reply;
"Good Morning (well it is here anyway!) Geoff,
Thanks for checking on me. My wicked ways with buying tubes via PayPal finally caught up with me when the wife got the credit card statement. Ouch! I was in the midst of getting the wings for the OB, but have to cool off for awhile to maintain the peace. I'll be back to it soon and post my findings. Take care and have a safe and happy Holiday Season.
Bob"
Me thinks he had better do some good Christmas shopping.
Geoff.
Hi Andrew, I think the idea has merit.
My thoughts:
The sensitivities should be similar.
They should be wired in parallel, with perhaps a high freq rolloff on the larger driver.
The larger driver placed in the centre of the baffle, and the baffle
tuned to the res F of the larger driver. That's a big baffle.
The smaller driver, with a higher res F positioned to counteract the lumpy response from the larger driver.
Rather than having a single tuning point, the baffle is heading towards aperiodic without absorbing the rear wave.
Which drivers are you considering?
Geoff
My thoughts:
The sensitivities should be similar.
They should be wired in parallel, with perhaps a high freq rolloff on the larger driver.
The larger driver placed in the centre of the baffle, and the baffle
tuned to the res F of the larger driver. That's a big baffle.
The smaller driver, with a higher res F positioned to counteract the lumpy response from the larger driver.
Rather than having a single tuning point, the baffle is heading towards aperiodic without absorbing the rear wave.
Which drivers are you considering?
Geoff
A difficult mix. The Tannoy wants a 1129/28x2 ~ 20ft wide baffle. It probably wont need assistance from the Celestion.
Is the Tannoy a dual concentric? It may be better in 5 or 6 cubs of BR.
The Celestion is probably a good unit for OB. How high does it go?
Putting the 2 together. How about OB the Celestion, and horn load the Tannoy. Something like the 150 hz A7. with a sealed chamber on the back to push the res up.
This may have to branch to a new thread.
Geoff.
Is the Tannoy a dual concentric? It may be better in 5 or 6 cubs of BR.
The Celestion is probably a good unit for OB. How high does it go?
Putting the 2 together. How about OB the Celestion, and horn load the Tannoy. Something like the 150 hz A7. with a sealed chamber on the back to push the res up.
This may have to branch to a new thread.
Geoff.
I didn't get my Heppners on a baffle yet, but did run some music thru them. Sure are loud! Must be very sensitive drivers. Can't tell yet how they sound, execpt bright.
Turns out the crossover is only on the horn tweeter - 2nd order. The 12" runs fullrange.
I love fullrange drivers, they taste so much better.
Turns out the crossover is only on the horn tweeter - 2nd order. The 12" runs fullrange.
I love fullrange drivers, they taste so much better.
Hi,
the drivers are bass units, both types are optimised to augment the full range drivers and only for music reproduction.
Both come in their own cabinets, 15inch in the 205L Leopard (4off) and 18inchers (1pair) in the 300L B950.
But, they don't go deep and I wonder if an experiment with open baffle might give more extension.
No T/S yet.
the drivers are bass units, both types are optimised to augment the full range drivers and only for music reproduction.
Both come in their own cabinets, 15inch in the 205L Leopard (4off) and 18inchers (1pair) in the 300L B950.
But, they don't go deep and I wonder if an experiment with open baffle might give more extension.
No T/S yet.
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