Does MJKs MathCAD sheets take into account room gain or positioning in the room, things like that? The graph you have shown for the response of that 10 ft^3 box, if I put it near the back wall and possibly a corner, I would then get a big hump in frequency response around the 40Hz area, right?
I have been fooling around in Thorsten Loeschs Xlbox work sheet which shows the boxes with their position from the back wall and side wall. With the 10 ft^3 box tuned to 40Hz, it has a big bump in bass compared to the box Thorsten has built for the Afterburner project which is much more flat looking in room. If I lower the tunning frequency to 30Hz, it reduces the peak close to flat, but then that is tuned pretty far below the 12lta's Fs.
I have been fooling around in Thorsten Loeschs Xlbox work sheet which shows the boxes with their position from the back wall and side wall. With the 10 ft^3 box tuned to 40Hz, it has a big bump in bass compared to the box Thorsten has built for the Afterburner project which is much more flat looking in room. If I lower the tunning frequency to 30Hz, it reduces the peak close to flat, but then that is tuned pretty far below the 12lta's Fs.
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davidallancole said:
What I posted are simple half space plots and MJK's fee WSs only plot up against a wall for now. I'd have to reload LspCad to do more elaborate sims, which I don't plan to do anytime soon.
Anyway, yes, there would be a peak with more peaks/dips higher up, but tuning it lower with a smaller vent normally works well enough at a decent listening distance which TL's SS doesn't appear to account for. For sure the peak wouldn't be that high except up close in a corner, though a ~30 Hz Fb (5" dia. x 0.75" L vent) seems about right to flatten the 10 ft^3 12LTA.
GM
Very very my kind of speakers.I want to ask if you will have future options ....for future speakers what do you have in mind?
Also considering you have "some big" experience with Altec's maybe you could help me to figure out if that Altec was rewinding or that kind of glue is present on most of the dustcap drivers.
This is Altec 414-16B:
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Probabily because the T/S parameters is different these days...
and the purpose is to take your money....all of the money.
That's why I ask about modding the spider on PA driver to have low fs.
In old days the spider look like this and the suspension was made from leather sought on the paper cone.On the back was a mighty fieldcoil and the sound was brilliant.
Feastreax have something on these designs on the bench but,from my point of view,they don't reach the impact of these Altecs.
Check this spider...
and the purpose is to take your money....all of the money.That's why I ask about modding the spider on PA driver to have low fs.
In old days the spider look like this and the suspension was made from leather sought on the paper cone.On the back was a mighty fieldcoil and the sound was brilliant.
Feastreax have something on these designs on the bench but,from my point of view,they don't reach the impact of these Altecs.
Check this spider...
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GM said:
GM,
If it is the spider responsible for most of the cone suspension stiffness, and not the surround, How would it be to carefully remove radial segments from the spider with an approxoknife to reduce Fs and possibly increase efficiency?
I have a pair of Selenium 10 inch 10PW3`s that are super stiff that would be of more use to me if the Fs was lower without losing efficiency.
felixx said:
?? WRT to woofer choice, I'm good for life.
If I understand your question, Altec's quality assurance (QA) slipped quite a bit over time beginning in the '60s due to being bought out/financially gutted, so just because it has a little glue showing on the DC vent screen doesn't mean it's not original or was re-coned with a factory kit.
GM
Godzilla said:
Higher Vas with wider BW and more attention to diaphragm design/damping of break-up modes. Note that they are still available new and there's other brands/models that some consider even better, but they are all quite expensive, though if you look at pricing WRT inflation you'll see they are no more expensive today than 50 yrs ago.
GM
rcavictim said:
I've heard of folks doing this, but never felt the need beyond experimenting to see how hard it was (I ruined a few radio/TV drivers before giving up, so caveat emptor), but understand that while this lowers Fs, raises Vas, efficiency drops since Qes stays the same........
GM
"............How would it be to carefully remove radial segments from the spider with an approxoknife to reduce Fs and possibly increase efficiency.............."
NO ! The spider has other functions like preventing the VC from exiting the magnetic gap when driven hard and if not that , just preventing decapitation. While cutting the spider will decrease Fs I doubt you will get much increase in midband efficiency.
AND your coil will now be able to 'rock about' more easily and have ocassional meetings with the pole piece and magnet structure and while the coil will be having fun I am sure you wouldn't !
I have done this with the surround on paper suspensions and regretted it . On a spider I think you are inviting disaster and reducing the performance of the driver.
If you are doing this as an experiment , go ahead and let us know the progress towards the death of the driver. It might be interesting !
NO ! The spider has other functions like preventing the VC from exiting the magnetic gap when driven hard and if not that , just preventing decapitation. While cutting the spider will decrease Fs I doubt you will get much increase in midband efficiency.
AND your coil will now be able to 'rock about' more easily and have ocassional meetings with the pole piece and magnet structure and while the coil will be having fun I am sure you wouldn't !
I have done this with the surround on paper suspensions and regretted it . On a spider I think you are inviting disaster and reducing the performance of the driver.
If you are doing this as an experiment , go ahead and let us know the progress towards the death of the driver. It might be interesting !
"............How would it be to carefully remove radial segments from the spider with an approxoknife to reduce Fs and possibly increase efficiency.............."
Been there, done that 20 years ago. I usually built closed boxes and in these, there were no problems regarding durability, at least not bass drivers. If my fuzzy memory is right, the bass was louder. But don't hang me for that, young and foolish as I was, it could have been less control of the driver!
Been there, done that 20 years ago. I usually built closed boxes and in these, there were no problems regarding durability, at least not bass drivers. If my fuzzy memory is right, the bass was louder. But don't hang me for that, young and foolish as I was, it could have been less control of the driver!
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The real problem was, that after one year, the gravity took over and rubbing of the coil was a fact. These on the pictures, have a triangular shape of the cut outs, like a nuclear radiation sign. The importance was to have the cut outs at 5 and 7 o'clock + the last at 12 o'clock. That prevented the sagging of the cone.
As of today, I would not mess with this tveak.
Peter
As of today, I would not mess with this tveak.
Peter
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