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Old 27th September 2013, 12:08 AM   #11
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Re: ' Both drivers are 8 ohm " - no they're not, read my sig. Without measurements, it's all guesswork...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 27th September 2013, 12:23 AM   #12
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Originally Posted by BlueWizard View Post
I never was a fan of Cone Tweeters.

If you can find a drop-in replacement in a dome tweeter, I think it would be an improvement.

How are the surrounds holding up on the Tweeter? Any signs of wear, tear, or deterioration?

Can we get a date on these, any idea when they were manufactured?

Can you tell what kind (electrolytic, non-polar electrolytic, Film) capacitors? If any kind of electrolytic and if they were manufactured a few decades ago, then likely they have deteriorated. A Poly or Mylar or Metal Film Capacitor would be a big step up and last for many more decades. Quality capacitors need not cost a fortune, but I recommend only using the non-polar electrolytic if you are on a starvation budget. Otherwise, the various film capacitors are you best choice.

Just a few more thoughts.

Steve/bluewizard
Speaker manufactured in 1976. Tweeters look like there is some wear, surrounds are good but paper cone a bit distorted.
Solen makes caps inexpensive caps. What you say? Any recommendation of other brands of metalized film caps?
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Old 27th September 2013, 01:07 AM   #13
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Originally Posted by PeteMcK View Post
Re: ' Both drivers are 8 ohm " - no they're not, read my sig. Without measurements, it's all guesswork...
PeteMcK,
There's no way I have the ability to do this. I'm just trying to make a little improvement to the tweeters of my 1976 Altec Lansings. Not really trying to redesign them. I am concerned that the stock 2uf cap is to low for the stock tweeter. While I'm at it maybe switching the original cone tweeter for a dome or Phenolic tweeter, w/ the correct cap for a 3khz 1st order xover.
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Old 27th September 2013, 01:43 AM   #14
Dissi is offline Dissi  Switzerland
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Quote:
Originally Posted by mjatabor View Post
Would you consider 5.5uf-6.5uf cap to cross over it?
I think that's too high and 3.3 uF should be right, but you have to try. Another possibility to consider: The distortions could be caused by bad contacts (oxidation) in the L-pad.

Is this the speaker we are talking about? SEVENTIES STEREO: Altec/Lansing Model One
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Old 27th September 2013, 11:50 AM   #15
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by mjatabor View Post
The 2" paper cone tweeter w/ metal dust cover uses a simple 1st order xover w/ a single cap and variable L-pad.
The L-pad presents an opportunity to test for issues with the tweeter at resonance. As you attenuate it, the impedance peak will have less interaction with the capacitor.

What you basically do is disconnect the woofer, turn the L-pad to full (0dB), and listen for the problem in the tweeter. Now turn the L-pad down and the amplifier up until it's at the same level as before and see if the problem is less obvious.

If this proves true, you can use a filter to remove the peak altogether.
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Old 27th September 2013, 12:41 PM   #16
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Originally Posted by Dissi View Post
I think that's too high and 3.3 uF should be right, but you have to try. Another possibility to consider: The distortions could be caused by bad contacts (oxidation) in the L-pad.

Is this the speaker we are talking about? SEVENTIES STEREO: Altec/Lansing Model One
Yes this is it.
I did deoxit the variable L-pad and speaker binding posts. I think what I'm hearing is the ever present peakiness of the paper cone tweeter.
Maybe cap replacement should be my first step before I throw out the baby w/ the bath water. Should I replace w/ a 2uf or 3.3uf? Would you use Solen or another inexpensive brand?

Quote:
Originally Posted by AllenB View Post
The L-pad presents an opportunity to test for issues with the tweeter at resonance. As you attenuate it, the impedance peak will have less interaction with the capacitor.

What you basically do is disconnect the woofer, turn the L-pad to full (0dB), and listen for the problem in the tweeter. Now turn the L-pad down and the amplifier up until it's at the same level as before and see if the problem is less obvious.

If this proves true, you can use a filter to remove the peak altogether.
I did deoxit the variable L-pad and speaker binding posts.
As I adjust the L-pad it gets bright and clearer and as I lower it gets muffled, but there is the present resonant peak and raspyness. I was thinking of replacing the cap, So maybe this should be my first step.
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Old 27th September 2013, 12:57 PM   #17
AllenB is offline AllenB  Australia
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Originally Posted by mjatabor View Post
As I adjust the L-pad it gets bright and clearer and as I lower it gets muffled, but there is the present resonant peak and raspyness.
Did you disconnect the woofer for this test? If you didn't then is it possible this is a woofer issue.

Quote:
I was thinking of replacing the cap, So maybe this should be my first step.
The quality of the cap may make a small difference. It sounds as if this isn't a small issue? It is sometimes possible to get surprisingly good sound out of a tweeter connected through even a cheap electrolytic capacitor.

Regardless it would probably be best to apply a filter to tame the resonance impedance peak before using a larger value of capacitor.

The better option (I'm assuming) would be to make the tweeter second order and cross the woofer.

Last edited by AllenB; 27th September 2013 at 01:00 PM.
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Old 27th September 2013, 01:50 PM   #18
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Quote:
Originally Posted by mjatabor View Post
.... while the original tweeters work they sound distorted and harsh to me
It's very likely that the harshness comes from a peak in the tweeter.

I suggest you look at this polydome Vifa D19TD-05 tweeter. It's only $16.88 at PE. It is an excellent candidate for 1st order. You may not even need a LCR.
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Old 27th September 2013, 01:58 PM   #19
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Originally Posted by Michael Chua View Post
It's very likely that the harshness comes from a peak in the tweeter.

I suggest you look at this polydome Vifa D19TD-05 tweeter. It's only $16.88 at PE. It is an excellent candidate for 1st order. You may not even need a LCR.
Thanks for the confirmation as I just put that one at the top of my list. What cap value is usually used with this tweeter in a 1st order crossover?
What do you mean by LCR? I only know of it as Left/Center/Right speakers and the Altecs in this system is a vintage analogue system.
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Old 27th September 2013, 02:07 PM   #20
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Originally Posted by AllenB View Post
Did you disconnect the woofer for this test? If you didn't then is it possible this is a woofer issue.

The quality of the cap may make a small difference. It sounds as if this isn't a small issue? It is sometimes possible to get surprisingly good sound out of a tweeter connected through even a cheap electrolytic capacitor.

Regardless it would probably be best to apply a filter to tame the resonance impedance peak before using a larger value of capacitor.

The better option (I'm assuming) would be to make the tweeter second order and cross the woofer.
I did not disconnect the woofer but with my ear at the woofer it is clear and smooth, with my ear at the tweeter there is the peakiness. The more I listen there is added sibilance and edge with vocals so I think that the peak is the problem I'm hearing. Other than that the speakers sound very nice and involving so I don't think I want to mess w/ the woofer.
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