" Post #39
rlrohlfs,
I have no current plans to pursue a Mark Audio Alpair 10 with a ribbon design. ...
Jim"
Thanks for the reply. I may give these ago after I try them FR first. From the posts here, I have the impression that, with a little effort, they can be dropped into the same 48" MLTL I used for the Jordan's.
One other question - Have you ever considered or created a FR dipole MLTL? I've been thinking about building a variant of the 48" MLTL in a dipole configuration.
-
Rick
rlrohlfs,
I have no current plans to pursue a Mark Audio Alpair 10 with a ribbon design. ...
Jim"
Thanks for the reply. I may give these ago after I try them FR first. From the posts here, I have the impression that, with a little effort, they can be dropped into the same 48" MLTL I used for the Jordan's.
One other question - Have you ever considered or created a FR dipole MLTL? I've been thinking about building a variant of the 48" MLTL in a dipole configuration.
-
Rick
rlrohlfs said:
The A10 is closer to the factory specs than the latest batches of JX92S, As the 48" MLTL was designed with factory data i expect the A10 will work better than a current JX92s.
dave
Sorry all - I thought I had this thread set for auto notification.
I was thinking dipole, where the 2 drivers are out of phase. But Bipole may work better. As you can probably tell I haven't thought this through yet.
I'm thinking of building 2 of the GM 48" MLTL enclosures then placing them inside a wrapper enclosurer. A box within a box. The 2 inside boxes would be situated back to back so that the drivers are on opposite sides with one rear firing and the other forward firing.
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Rick
I was thinking dipole, where the 2 drivers are out of phase. But Bipole may work better. As you can probably tell I haven't thought this through yet.
I'm thinking of building 2 of the GM 48" MLTL enclosures then placing them inside a wrapper enclosurer. A box within a box. The 2 inside boxes would be situated back to back so that the drivers are on opposite sides with one rear firing and the other forward firing.
-
Rick
Question to the professionals here
Hi to all,
some days ago I finished the MLTL with the Alpait 10 donated from Jim. I must say I am more than pleased with the performance - but there is one minor thing I hope I can find some help here: I am using the speaker with a tube amp and when listening I realised that the higher frequenzies are bit louder than the rest - so being a clueless constructor with no technical background I added the baffle step compensation suggested by Jim (note: I have to place the speakers a bit away from the backwall as they are standing under a droop - I also have the reflex channel on front - hope that is no big mistake).
The sound got a little more balanced but not totally satisfiying. So I read a bit around and I finally got attrackted to the fact that the impedance in the hights is rising quite a lot and this might cause the issue with a tube amp. So I added a small correction network of 15 uF Cap and 8,2 Ohm resister parallel to the speaker termina, this time without the baffle step compensation. Now I think I am getting somewhere and it sounds much more balanced over the whole frequency rang.
However I am sure you can do better - so my question here is, if anyone had alreday calculated a real perfect impedance correction circuit for the Alapir 10 / MLTL ?
Any suggestions or help is highly appreciated !
Thanks & best regards
Peter
Hi to all,
some days ago I finished the MLTL with the Alpait 10 donated from Jim. I must say I am more than pleased with the performance - but there is one minor thing I hope I can find some help here: I am using the speaker with a tube amp and when listening I realised that the higher frequenzies are bit louder than the rest - so being a clueless constructor with no technical background I added the baffle step compensation suggested by Jim (note: I have to place the speakers a bit away from the backwall as they are standing under a droop - I also have the reflex channel on front - hope that is no big mistake).
The sound got a little more balanced but not totally satisfiying. So I read a bit around and I finally got attrackted to the fact that the impedance in the hights is rising quite a lot and this might cause the issue with a tube amp. So I added a small correction network of 15 uF Cap and 8,2 Ohm resister parallel to the speaker termina, this time without the baffle step compensation. Now I think I am getting somewhere and it sounds much more balanced over the whole frequency rang.
However I am sure you can do better - so my question here is, if anyone had alreday calculated a real perfect impedance correction circuit for the Alapir 10 / MLTL ?
Any suggestions or help is highly appreciated !
Thanks & best regards
Peter
Greets!
Without an accurate, high resolution impedance plot, the best I can do is using the average specs of a couple of measured drivers, so for 5.4 ohms Re, 0.072 mH Le:
zobel = 6.75 ohms/1.58 uF
GM
Without an accurate, high resolution impedance plot, the best I can do is using the average specs of a couple of measured drivers, so for 5.4 ohms Re, 0.072 mH Le:
zobel = 6.75 ohms/1.58 uF
GM
to tubes@home (Peter)
Did your speakers (cones) undergo a burning-in process before you did the listening tests ? or where they brand new?
I'm just asking because your listening impressions correspond quite exactly to my own general experience with new loudspeaker components (stiffness of the suspension etc.).
Chris.
Did your speakers (cones) undergo a burning-in process before you did the listening tests ? or where they brand new?
I'm just asking because your listening impressions correspond quite exactly to my own general experience with new loudspeaker components (stiffness of the suspension etc.).
Chris.
@GM - thanks ! A "bit" different to the values I got - actually I also found your calculation but on another german distributer page there was a calculation sceme where I got approx. to my values I tested. I have to get the parts for your calculation to give it a try !
@dave - that would be great - I am sure the real graph in the box looks a bit different than the specs from the driver alone - curiously waiting for your input ! big thanks !
@chris - well, the drivers don't hav hundrets of hours so maybe that could also be a point - but it is noticable that with the zobel I added the sound got more balanced so I don't think that it is only a question of the burn in - I will see in a whil ! Thanks for the hint !
Big thanks to all ! I am almost sure that the Alpair 10 has some big potential that is still hidden !
Peter
@dave - that would be great - I am sure the real graph in the box looks a bit different than the specs from the driver alone - curiously waiting for your input ! big thanks !
@chris - well, the drivers don't hav hundrets of hours so maybe that could also be a point - but it is noticable that with the zobel I added the sound got more balanced so I don't think that it is only a question of the burn in - I will see in a whil ! Thanks for the hint !
Big thanks to all ! I am almost sure that the Alpair 10 has some big potential that is still hidden !
Peter
Well, hidden by a poor match to the amplifier at any rate, rather than inherently buried for other reasons. 😉
tubes@home said:
You're welcome!
Hmm, none of the few formulas I have come even remotely close to your values. The formulas I used are ~ the standard ones most used AFAIK where Re, Le is known, though I was going to use one that reactance annuls Re if a high enough resolution impedance plot was available. If anyone has the measuring capability though, better to measure Re and find the frequency (F) where it doubles, then:
R ohms = Re*1.25
C uF = 10^6/(2*pi*Re*F)
GM
Hmm, Re has been measured as 5.4 ohms, so how come the impedance has already fallen to ~3 ohms at 10 Hz? Is this the right plot?
GM
GM
OK, thanks, then it looks like Re doubles around 6 kHz, so using the above formulas:
R ohms = 6.75
C uF = 4.912
FWIW, assuming the HF roll off is an artifact also, then at 0.1028, Le calculates a little higher than published which changes my previous zobel's capacitor from 1.58 to 2.256.
Never having used any formulas other than the ones I listed, I don't know if there's any audible difference between them, so choosing a capacitor value anywhere between 1.58-4.912 uF may be close enough.
GM
R ohms = 6.75
C uF = 4.912
FWIW, assuming the HF roll off is an artifact also, then at 0.1028, Le calculates a little higher than published which changes my previous zobel's capacitor from 1.58 to 2.256.
Never having used any formulas other than the ones I listed, I don't know if there's any audible difference between them, so choosing a capacitor value anywhere between 1.58-4.912 uF may be close enough.
GM
As a practical matter, I measure the impedance curve of the speaker and then model the zobel. I choose values that will give a suitably flat impedance curve.
With single driver speakers, the zobel will have definitely affect the frequency response at the high end. With drivers that roll off early at the top -- e/FE167E/FE207E -- a zobel is not a good idea, whereas with the FE166E/FE206E/any Lowther, a zobel will help quell the rising response. In other words, a zobel is just another part of the contour filter.
Unfortunately,I don't have any A10's, so I'm really no help. Oh, well....
Bob
With single driver speakers, the zobel will have definitely affect the frequency response at the high end. With drivers that roll off early at the top -- e/FE167E/FE207E -- a zobel is not a good idea, whereas with the FE166E/FE206E/any Lowther, a zobel will help quell the rising response. In other words, a zobel is just another part of the contour filter.
Unfortunately,I don't have any A10's, so I'm really no help. Oh, well....
Bob
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