Yet they have fiberglass in the upper chamber. D'où ma confusion.
Altec does like to use the L-pad as a variable resistor, n'est-ce pas?
Yes,
A nice knob on the L-pad and big metal can to hold the parts. It looks nice from the outside of the enclosure, but is rather crude but so was any JBL of the time. At least it didn't use the horrid JBL window blind horn loading technique, that was a joke to say the least. I saw something like that I think on this thread with the Harbeth or something like it I think.
A nice knob on the L-pad and big metal can to hold the parts. It looks nice from the outside of the enclosure, but is rather crude but so was any JBL of the time. At least it didn't use the horrid JBL window blind horn loading technique, that was a joke to say the least. I saw something like that I think on this thread with the Harbeth or something like it I think.
My experience.
I have 15" pro woofer with fs of 37Hz.
Very low qts 0.2 and very strong motor.Two main things in adding mass.
Added 100 gr. of bitumen pads,very easy to work with BTW
Results was as expected qts raised from 0.2 to 0.4 , Fs lowered from 37 to 28Hz.
Box modeled as expected too.Now it's playing 30hz with authority.So i'm very happy.
I have 15" pro woofer with fs of 37Hz.
Very low qts 0.2 and very strong motor.Two main things in adding mass.
Added 100 gr. of bitumen pads,very easy to work with BTW
Results was as expected qts raised from 0.2 to 0.4 , Fs lowered from 37 to 28Hz.
Box modeled as expected too.Now it's playing 30hz with authority.So i'm very happy.
Last edited:
Back to the topic and picking up on cyclecamper's helpful post:
in days of yore, people would try to use caulk (like the oily stuff used to hold window glass since time immemorial) and, later great new stuff called "duct seal" in a donut around the dust cap. Has most of the physical and acoustical properties you'd want for a weight, but:
as a fan of ESL and true horns, the essential problem is Rice-Kellogg drivers which try to shake heavy cardboard masses at the thin air. Dumb, eh? Unless you transform the mass using a true horn (not mis-named TH) or go to SaranWrap ESL drivers.
In other words, adding mass just adds to the acoustic mismatch of the R-K design unless you are doing it as a trade-off to gain cone stiffness, larger diameter voice coil, lower free-air resonance in connection with spider and surround parameters, etc.
The AR-1 of the 1950's (one of which I am looking at now) had a thick, absolutely solid stiff cone and weighed a lot, but had a free-air resonance of 12 Hz. In it's 1+ cubic-foot box, resonance moved up to around 37 Hz (a very good place for St-Saens Organ Symphony, no kidding) and even today sounds great.
So in sense, by adding weight you are re-designing your own driver (and that's fine) and it may serve your purposes. But in the larger sense, it is going backwards.
Ben
in days of yore, people would try to use caulk (like the oily stuff used to hold window glass since time immemorial) and, later great new stuff called "duct seal" in a donut around the dust cap. Has most of the physical and acoustical properties you'd want for a weight, but:
as a fan of ESL and true horns, the essential problem is Rice-Kellogg drivers which try to shake heavy cardboard masses at the thin air. Dumb, eh? Unless you transform the mass using a true horn (not mis-named TH) or go to SaranWrap ESL drivers.
In other words, adding mass just adds to the acoustic mismatch of the R-K design unless you are doing it as a trade-off to gain cone stiffness, larger diameter voice coil, lower free-air resonance in connection with spider and surround parameters, etc.
The AR-1 of the 1950's (one of which I am looking at now) had a thick, absolutely solid stiff cone and weighed a lot, but had a free-air resonance of 12 Hz. In it's 1+ cubic-foot box, resonance moved up to around 37 Hz (a very good place for St-Saens Organ Symphony, no kidding) and even today sounds great.
So in sense, by adding weight you are re-designing your own driver (and that's fine) and it may serve your purposes. But in the larger sense, it is going backwards.
Ben
Last edited:
That is a re-design - a new driver. That "new" driver gives you certain nicer parameters like the lowered resonance (actually, that might be the only improved parameter, please correct me).
But it is also the same as throwing away half your magnet (just what do you think it means when a nice sanitary-sounding parameter like "loudness/watt" is lowered?) and doing grave harm to your transient response, cutting down the top end, distorting your mechanicals, and other consequences which aren't always strikingly visible when you glance at your new speaker parameters table.
We pay manufacturers a lot of money to make drivers with light cones and super flexible (but strong) supports that result in responsive yet low-resonance drivers. Anybody can make a "musical instrument" woofer with a heavy cone and coarse suspension.
If reproducing thunderstorms is your main purpose and mounting the driver horizontally, doubling the cone weight might be a good move.
Ben
Last edited:
I agree,it's not the best move and better to buy already suitable driver than adding mass...
But in my case,i dont feel i need to buy another woofer.
15" 4" voice coil,stiff cone and suspension,BL 30 Tm,98db sensitivity,10kg weight,low qts.
And yes, i use it as a subwoofer,i wont do it for midbass speaker.
No quibbling from me with your goals and your good grasp of issues. Nice driver. I'm cryin'.
Couldn't you approximate your purposes with a two-band parametric equalizer or other shaping, corner placement, or as others have mentioned for golfnut?
Funny, another day of the week I'd be screaming for more experimentation like you did.
Good luck to golfnut (but try to make sure your "interventions" are reversible).
Ben
Couldn't you approximate your purposes with a two-band parametric equalizer or other shaping, corner placement, or as others have mentioned for golfnut?
Funny, another day of the week I'd be screaming for more experimentation like you did.
Good luck to golfnut (but try to make sure your "interventions" are reversible).
Ben
Last edited:
What is your problem?
My 15" is clear midbass speaker with no low end,i remade it for subwoofer duty.And parameters i'm talking about only because to show it's not slow driver who can not hold another 100gr
Subwoofer cones does not need to be as light as possible.100-200gr is normal
And yes,bitumen pads are easy reversible,but it's suggestion for those who thinks about this mod
My 15" is clear midbass speaker with no low end,i remade it for subwoofer duty.And parameters i'm talking about only because to show it's not slow driver who can not hold another 100gr
Subwoofer cones does not need to be as light as possible.100-200gr is normal
And yes,bitumen pads are easy reversible,but it's suggestion for those who thinks about this mod
Did you take my comment as some kind of sarcastic insult when I posted "...your good grasp of issues"?
Or when I wrote I might be boosting for more experimentation like you did another day of the week?
Just plain polite straight Canadian compliments. I repeat, "compliments."
Ben
for every web poster who doesn't know how to write there's also a web reader who doesn't know how to read
Last edited:
Thank you. Apologies are rare on the anonymous web. Brave and good. More compliments.
Yup, "what's your problem" sounds OK but is idiomatic for hostility.
On the other hand, Canadian polite-speak gets me into trouble all the time on the web (esp. from Americans) when people can't read plain nice remarks at face value and think they are sarcastic and mean the opposite.
Ben
Last edited:
well, maybe thats a compliment in Canada 😛
sounds more like you broke your favourite hockey stick this weekend....😀
well, if you have a light coned woofer with low Fs, and moderate Qts, then you are a lucky guy and this may not be your game at all
but if its because you don't like the topic, no need to hold it back, just say it straight...no problem with that
If he broke his stick then it musta been a whopper. You see at this time of year we use our stick for fishin' poles, not grinding the opponents face into the boards. That starts again in September.
if you've been watching the stock market the last 10 days as a fellow retiree, you would be in a very very good mood, like I am again today. No hockey violence for me.
Topic is a good one, and where I've experimented. But I felt two faces of OP question seemed to get short attention: (1) some of the downsides of weight and (2) the adherence to driver parameters numbers as the sole data to be considered (or at least not thinking through what those changed numbers imply - like motor force). I felt some comment was needed.
In light of the driver construction and your needs for a low sound band, it can work and be worthwhile. But like a lot of things, it takes a lot more than heavy anti-sway bar to make your minivan a sportscar, but it helps.
Ben
Last edited:
sorry, but I don't quite know what 'low sound band' means ....you mean bass, or bad sound, or... 😕
fair enough
thanks for posting your result
Tinitus -
Nobody could say it better than daudio25: he took a very good woofer and successfully made a driver suitable for low woofing, but as he points out, it was less suitable for upper woofing.
Just a guess here, but if a person is using a good woofer it likely has a precise VC gap. So adding weight and mounting vertically might be iffy. Them's the risks. That's what I meant by "driver construction."
Ben
Nobody could say it better than daudio25: he took a very good woofer and successfully made a driver suitable for low woofing, but as he points out, it was less suitable for upper woofing.
Just a guess here, but if a person is using a good woofer it likely has a precise VC gap. So adding weight and mounting vertically might be iffy. Them's the risks. That's what I meant by "driver construction."
Ben
- Status
- Not open for further replies.