Yet another Scandyna/Dynaco A25 question! - diyAudio
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Old 5th February 2010, 01:39 PM   #1
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Default Yet another Scandyna/Dynaco A25 question!

Just after some informed opinions, and this looks like the go-to place!
I am yet another dude considering replacing the tweeter units in the above mentioned speakers. Not that there's much wrong with them. They were the best £30 i've spent in years, but i'm game to try the odd tweak! Anyway, i've got some SEAS Excell units, the same ones as used in the WD25T. Anyone tried these in the Dynaco cabs? If so,did you need to do much modification to the crossover, and would you say it was successful or not?
Any and all opinions welcome.
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Old 5th February 2010, 07:24 PM   #2
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Different tweeter = different crossover.

Could maybe design a new crossover around this datasheet for the A25 woofer:
http://www.madisound.com/catalog/PDF/25F-EW.pdf
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Old 5th February 2010, 07:47 PM   #3
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Before swapping the tweeter, there are a couple things you can do that greatly improve the top end performance.

1/ the cross-over parts suck. Replace the cap. Then figure out where on the level switch the system sounds best, then toss the switch and replace the string of resistors with a better quality one of the same value as the string that is active with the switch at the preferred position.

2/ remove the metal grill over the tweeter. Careful, the bolts that hold it on also hold the tweeter together, Remove the tweeter from the box, and do the surgery with the tweeter face up on a solid surface.

dave
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Old 5th February 2010, 08:00 PM   #4
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PS: This might be helpful

Click the image to open in full size.

from here.

dave
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Old 6th February 2010, 10:57 PM   #5
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Default progress

Thanks very much for all your responses. Much appreciated. Just thought you might like to see where i'm up to in all of this.
Got these off ebay, described as Scandynas. there was no tweeter level control on the back, or any type of connection cup or block. Just a wire fed through from the inside of the cabinet.
Replaced the original L-pad components and Jensen electrolytic cap with good quality modern equivalents from Maplin. The original cap value was a puzzler; 8uF, instead of the 5 quoted as the standard everywhere. Still, didn't question it. Just replaced them, took the grilles off the tweeters, and had a listen.
First impressions were, a nice, weighty sound with good coherence and carries a tune like few others i've heard. Stereo image has depth and width but is a little unfocussed, and there is a slight peakiness in the lower treble due, i suspected, to the larger value cap.
Took out the 8uF, to be replaced by a 5.7uF.
Sound more balanced now, but lacking in extreme top end. Still very lively and tuneful though.
At this point i thought, f**k it, try the Excells! They have the same faceplate and magnet dimensions as the originals. The tweeter cutouts only need a tiny bit of work to accomodate the slightly wider spacing of the tweeter terminals, but if it sounds crap, it's all retrofittable.
It sounded anything but crap! Stereo image snapped sharply into focus. Loads more air and expression in the extreme treble. Acoustic guitar in particular sounded beautifully warm and delicate. If there's a negative, there might be slightly less energy in the lower treble/upper mid, though that could be down to the Excell unit lacking the hardness of the original. I've only had about an hour's worth of listening to them set up this way, and i would really like a good 10-20 hours before i form a definite opinion, but I have to say that i really wasn't expecting to get such an impressive sound without adjusting some crossover values first.
Anyway as it's me, and i'm incapable of leaving well alone, I will be fiddling with the crossover. Well, you've got to live a little, haven't ya?!! If you're interested, I'll let you know how I get on.
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Old 6th February 2010, 11:32 PM   #6
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Hi walriley, all,
You are working with an "antique". NPI
You have a vintage woofer (please make sure w/reference number, if you have one. DcibeL also references one, you should confirm) and a new tweeter (you didn't mentioned which one, please refer to the right reference you have on the SEAS Excel). That old tweeter was not supposed to have a very large extension for the HF, and it was a big 1"1/2. Now, what you are doing not very much people have achieved before. I will be close by.

About the xover: you say, all about your xover is/was a cap on the tweeter?

Last edited by Inductor; 6th February 2010 at 11:41 PM.
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Old 6th February 2010, 11:35 PM   #7
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SEAS makes a tweeter like in the old times now.
Look up the Exotic line.
It has alnico magnet and a DR.Müller membrane.
Unfortunately it is very expensive.
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Old 6th February 2010, 11:37 PM   #8
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here it is :
http://www.seas.no/images/stories/ex...exotic-t35.pdf
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Old 6th February 2010, 11:46 PM   #9
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Unfortunately, there is nothing about the Seas Exotic line that I can see to justify the price. They are for people with more dollars than sense.

There is still available, a "modern" A25 woofer, the Seas A26RE4. It's $132 at Madisound, however, not entirely a drop-in replacement but as close as one could hope for.

Walriley, does your tweeter just have the cap, or a resisor as well? Glad to hear you are enjoying the simple driver swap.
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Old 6th February 2010, 11:52 PM   #10
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Quote:
Originally Posted by Joachim Gerhard View Post
SEAS makes a tweeter like in the old times now.
Look up the Exotic line.
It has alnico magnet and a DR.Müller membrane.
Unfortunately it is very expensive.
That tweeter is not going to work with same setup. I'm not saying is not good, just it will need a second order xover to tame the HF. Remember (I think) we are working with a woofer with no xover components(?!).
It all depends where walriley wanna go. If he is buying it, I mean another one (he has an Excel as he said). I will leave for now. Bye.

Last edited by Inductor; 6th February 2010 at 11:56 PM.
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