Dynaco A25 - Dead Tweeter
- Thread starter Zack Sainz
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- a25 dynaco tweeter issue
Zack Sainz
Active Member
RTally
Speaker addict
I would use 5.1 uF caps instead of the 4.7 uF to replace the original 5 uF cap. It is best to use a cap with a value as close as possible to the original. A 4.7 uF cap is 6% off the original cap value, whereas the 5.1 is only 2% off.
Parts Express has both Dayton and Solen 5.1 uF caps.
kydog
Super Member
They actually come with the grill covers not shown.
stickman
Super Member
I concur with using a slightly larger cap value than one that is lower than the original to make sure you get adequate lower frequency extension from the tweeter is recommended IF you are using an original replacement tweeter. Fortunately those new SEAS replacement tweeters are designed to have a low cross-over point and should handle the 5.1 uf caps with absolutely no issues.
WaynerN
Addicted Member
The higher the capacitance, the lower the cross-over point. An example is a first order Butterworth @ 2000 takes about a 10uf cap, @ 1500 it takes 13.25uf cap. The 5uf cap makes the cross-over point @ 4000. Too low of a cross-over point may get into the tweeter's resonance frequency zone and that is a bad thing. It can certainly make the tweeter buzz when it tries to produce those too low frequencies and it can actually damage the tweeter.
Any speaker's cross-over point is not a brick wall. So a first order XO at say 2000 down an octave is 1000 cycles at a 6db decrease. At the second octave its at 500hz its at only 12db. That is really, really low. That is why most modern XOs use at least a 2nd order scheme. Everything doubles then so @1000 cycles it would be 12db down, at 500 it would be 24db down.
Any speaker's cross-over point is not a brick wall. So a first order XO at say 2000 down an octave is 1000 cycles at a 6db decrease. At the second octave its at 500hz its at only 12db. That is really, really low. That is why most modern XOs use at least a 2nd order scheme. Everything doubles then so @1000 cycles it would be 12db down, at 500 it would be 24db down.
Last edited:
Zack Sainz
Active Member
Blue Shadow
Waiting for Vintage Gear from this century
Looking forward to the report of sound quality differences with the tweeter swap.
Zack Sainz
Active Member
I’ve done the swap, and read that speaker burn in is not a thing. (Shots fired, I know)
Before testing the A25s I had my KLH 6s up to my Marantz Model 22, which have sounded great and tried out Fleetwood Mac’s “The Chain.”
***TEST 1***
Song: Fleetwood Mac’s “The Chain”
a/b-ing the original tweeter vs the new, making sure that that the nobs on the back were in the same position, my friend and I found that the new tweeter is a touch louder, more detailed and brighter. We dialed nobs back and forth then played with the treble and bass and found a fun spot.
We finished the tweeter replacement on the other speaker and let some music through these guys.
***Test 2***
Song: Fleetwood Mac’s “The Chain”
Since we had the 6s at hand, we took it a step further, in the next room I hooked up my 6s to my Scott 299B and compared them to the A25s on the Marantz 22.
The 6s sounded better to us with this set up.
***Test 3***
Song: Fleetwood Mac’s “The Chain”
Next step, my friend had to leave, but I swapped the 6s back on to to the Marantz, and then A25s on to the Scott.
The A25s are brighter, but the tubes helped smooth it out a ton! I also reduced a little treble and these are really singing.
After putting the A25s on the tubes it’s a toss up, definitely with my configuration the A25s are better with tubes than they are with SS. With this config both sound amazing for different reasons. I think the main thing that I’m noticing is detail. My 6s are a little slow and very smooth no work done to them except for sealing the cloth surrounds. The A25s are very quick and push a more accurate reproduction.
The 6s work on both SS and tubes, like so easily, it’s very impressive, 6s aren’t very picky.
Bottom of the line. I am thrilled. My girlfriend on on the other hand, not so thrilled, as I have a set of KLH 5s that I’m working on. 3 sets of speakers isn’t crazy, right?!
Before testing the A25s I had my KLH 6s up to my Marantz Model 22, which have sounded great and tried out Fleetwood Mac’s “The Chain.”
***TEST 1***
Song: Fleetwood Mac’s “The Chain”
a/b-ing the original tweeter vs the new, making sure that that the nobs on the back were in the same position, my friend and I found that the new tweeter is a touch louder, more detailed and brighter. We dialed nobs back and forth then played with the treble and bass and found a fun spot.
We finished the tweeter replacement on the other speaker and let some music through these guys.
***Test 2***
Song: Fleetwood Mac’s “The Chain”
Since we had the 6s at hand, we took it a step further, in the next room I hooked up my 6s to my Scott 299B and compared them to the A25s on the Marantz 22.
The 6s sounded better to us with this set up.
***Test 3***
Song: Fleetwood Mac’s “The Chain”
Next step, my friend had to leave, but I swapped the 6s back on to to the Marantz, and then A25s on to the Scott.
The A25s are brighter, but the tubes helped smooth it out a ton! I also reduced a little treble and these are really singing.
After putting the A25s on the tubes it’s a toss up, definitely with my configuration the A25s are better with tubes than they are with SS. With this config both sound amazing for different reasons. I think the main thing that I’m noticing is detail. My 6s are a little slow and very smooth no work done to them except for sealing the cloth surrounds. The A25s are very quick and push a more accurate reproduction.
The 6s work on both SS and tubes, like so easily, it’s very impressive, 6s aren’t very picky.
Bottom of the line. I am thrilled. My girlfriend on on the other hand, not so thrilled, as I have a set of KLH 5s that I’m working on. 3 sets of speakers isn’t crazy, right?!
RTally
Speaker addict
I have both KLH Model Sixes and Dynaco A25 (actually, two pair of each). If you have not recapped the Six it is no wonder the A25 are brighter. My Model 6s are hands down better than my A25s. The upper registers are the weak point on my A25s and stellar on my Model 6s.
Recap your 6s and then retest.
Zack Sainz
Active Member
I have both KLH Model Sixes and Dynaco A25 (actually, two pair of each). If you have not recapped the Six it is no wonder the A25 are brighter. My Model 6s are hands down better than my A25s. The upper registers are the weak point on my A25s and stellar on my Model 6s.
Recap your 6s and then retest.
I really need to recap everything, all the soldering and caps and such was intimidating, but after doing the A25s I feel much more confident.
Once I recap the squad I’ll retest.
What amp/receiver are you using?
RTally
Speaker addict
I am using a Denon POA-5200 dual mono amp (120 wpc). I've also used a NAD7240PE and a Luxman LV-113 that did very well driving the speakers. I've used various vintage and newer receivers and AVRs (Pioneer, JVC, and several different Yamahas) but they all disappoint.