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A-50 enclosure dimensions and XO schematic - newbie to classicspeakerpages


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#21 dynaco_dan

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Posted 14 September 2007 - 03:40 AM

Hi again;

My memory is of a piece of felt-like material covering a slot or hole in an A-35 or A-50 partition board.

I have no memory of what was on the other side of that felt material, if anything.

I had written the cabinet measurements and included the slot or hole size as well.

When I come across those old notes I will post my writings.

Without more technical information, a Scan driver can be treated the same as a Seas driver.

The only difference is when physically replacing a Scan woofer with a Seas, knotches must be cut where the screw horns protrude.

A minor but necessary job.

I cannot comment on the tweeters physical mounting differences, if there is any.

Whether the Scan drivers sound noticeably different from the Seas is yet to be written up here.
VERN

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#22 dynaco_dan

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Posted 14 September 2007 - 02:01 AM

>Observations:
>
>* All the screws for mounting the several speakers were not
>tight. I could turn them about 1/4 turn more. I don't know
>if this is significant. After 30 years and cabinet resonances
>it did not surprise me.

You need to perform an exorcism to break in your new caps.

If you place a woofer basket on your head and dance to Blood, Sweat and Tears, Spinning Wheel, on a moonlit night, you will find the caps sound way better in a day or two.

Ask our good member Frank about this. LOL LOL

Ok lousy humour.

The Dynaco drivers were sealed into the enclosures with a pretty sticky bluey-green goop.

The fact that you could turn the screws 1/4 turn more may be from the wood drying out or compression of the goop.

Be cautious tightening the screws seeing as how they are only into the soft wood and can strip real easy.

You may give thought to glueing a few wooden matches to the edge of each screw hole for added grip.

Lee Valley, a local big boys toy store, sells woodworking accessories.

They have a tapered wood bit which matches a pencils profile, you can taper the holes and use a pencil sharpener to end shape a dowel to fill in a hole entirely if glued flush.

With the goop being not available, soft putty sealant is in order and I see you used it, great.

Assuming you bought a full package of 3M Strip Caulk, I imagine you have enough left for many future projects. LOL

Eight screws is great.

You may even give thought to using T-Nuts instead of wood screws, the same as AR speakers.

The woofers are lightweight and do put out a good sound, considering.

Dynaco's claim was that 2 - 10" woofers put out more bass than a larger woofer with a better transient response.

>
>* Only four screws are used for each woofer. I will use eight
>when I finish the job. I will also temporarily remove the
>other woofer and use 3M Strip-Calk for sealing it shut.
>
>* I was surprised about the woofer. Really a 'lightweight'.
>I was expecting more magnet structure. Marked 15 ohms.

These were the only Dynaco 10" 15 ohm woofer drivers, made by both Scan first and then Seas.

They were made in Denmark.

>
>* The woofer is marked SEAS and 'Made in Scandinavia'. Does
>that mean it is made in Norway? Probably.
>
>* The capacitors are new in appearance. I saw no sign of
>leakage of the elecrolyte in the electrolytic capacitor. I
>have yet to check for current leakage.
>
>* The compartment wall inside is definitely slanted at roughly
>the same angle as the speakers are 'tipped'.
>
>* There is a cloth cover over the inter-compartment slot. I
>did not want to remove it.

Good idea, you never know what might come crawling out. LOL

If you were to remove the tweeter, you will be able to see what was done on that side of the cutout and if they stuffed that section of the enclosure.

A clear closeup of the crossover, before, would be really great, please.

This will clear up a little void for information.

>
>* The speaker system works fine but it did before. Perhaps
>the capacitors were still quite OK.
>
>* I will recap the other speaker system this weekend.
>
>John Jensen
>
>>
>>I'm going to follow up this posting with more observations
>and
>>comments.
>>
>>John Jensen
>>
>

Dynaco recommended a 1 1/2 amp fast blow fuse for speaker protection.

Perhaps a 1 1/4 amp may be used in line with their age.

My main servicing experience was with the Dynaco A-25's, many 100's.

Primarily Seas, not too many Scans.

In that system the woofer was by far the weakest link, the tweeter, the exact same one used in all their classic speakers, was a really rugged unit.

They outlasted the woofers at least 100 - 1, at least in my experience.

Remember that all speaker damage is cumulative, you can almost burn the voice coil's each time you overload them, not a pleasant sight.

Keep your eyes out for a spare pair of these woofers, they are rarer than hen's teeth, they also will not lose their value in the future.

I was fortunate last year to buy a pair off ebay and it was a local seller and free pickup, a nice man too.

If you are looking at a Dynaco woofer of any impedance, if the mention of a buzz comes up, leave it alone, it is screwed, permanently.
VERN

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#23 dynaco_dan

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Posted 13 September 2007 - 05:22 PM

Hi John;

Thanks for your write-up.

If possible please take a before photo, or two, of the crossover board and after mod.
VERN

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#24 jwjensen356

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Posted 13 September 2007 - 03:43 PM

Observations:

* All the screws for mounting the several speakers were not tight. I could turn them about 1/4 turn more. I don't know if this is significant. After 30 years and cabinet resonances it did not surprise me.

* Only four screws are used for each woofer. I will use eight when I finish the job. I will also temporarily remove the other woofer and use 3M Strip-Calk for sealing it shut.

* I was surprised about the woofer. Really a 'lightweight'. I was expecting more magnet structure. Marked 15 ohms.

* The woofer is marked SEAS and 'Made in Scandinavia'. Does that mean it is made in Norway? Probably.

* The capacitors are new in appearance. I saw no sign of leakage of the elecrolyte in the electrolytic capacitor. I have yet to check for current leakage.

* The compartment wall inside is definitely slanted at roughly the same angle as the speakers are 'tipped'.

* There is a cloth cover over the inter-compartment slot. I did not want to remove it.

* The speaker system works fine but it did before. Perhaps the capacitors were still quite OK.

* I will recap the other speaker system this weekend.

John Jensen

>
>I'm going to follow up this posting with more observations and
>comments.
>
>John Jensen
>
That's not an issue, that's a problem.

#25 jwjensen356

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Posted 13 September 2007 - 03:24 PM

Vern, I can now add some first-hand knowledge. Seeing the photos you posted and having reviewed the cross-over schematic posted elsewhere, I bit the bullet and decided to recap my speakers. Mine are of unknown history but they certainly must be at least 30 years+ old.

After reviewing what others have written about capacitors, I went the ClarityCaps route. They are more expensive than Solens but affordable. I went with the SA series.

After removing one speaker (the one nearest the edge) I could look inside. I cut the woofer leads and got it out of the way. I had to remove several pieces of sound absorbing material (luckily just tucked into place, not glued, which made replacement easy). There were the boards just as they appear in the pictures. I snipped the connecting wires and removed the capacitors.

The 24F capacitor is marked "Jensen Capacitors, Electrolytic Cross-Over Capacitor, 24F, 50 WVDC, 25 WVAC, EAR-1-0518E24PR, Made in Denmark" The 5F capacitor is marked as 50 WV and NP (non-polarized). I don't recognize the manufacturer but it looks typically Japanese of the period.

The ClarityCaps are massive in comparison (far voltage overrated compared to the 50V working voltage rating of the originals) but I was able to fit them in. Soldering was not easy. I was not about to poke around in there with a hot soldering iron so I used my old soldering gun. It also has two penlite bulbs so that helped illumination. I made sure they were securely mounted using silicone goop adhesive. I soldered the woofer to the leads and put it back in place using 3M Strip-Calk.

After dinner I fired up the amplifiers and listened to music. Fine. Sounded great.

I'm going to follow up this posting with more observations and comments.

John Jensen

>Hi again;
>
>I went back and the other parted speaker drivers are now
>listed.
>
>A much better view of it's crossover.
>
>It appears that there is a large cap, coil, large resistor,
>and a small cap, maybe, as well, on the other circuit board.
>
>This is a much more complex crossover than the A-25 and A-35.
>
>I believe that the A-10 will have a similar, if not identical
>crossover, composing of the right board contents only, that
>is.
That's not an issue, that's a problem.

#26 Guest_monkamonk2001_*

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Posted 09 May 2009 - 01:12 AM

I recently acquired the four woofers and two tweeters as used in the A-50 in two "really" home-made sealed boxes of about 40 litres (1.4 cuft) for A$10 /pr at my local salvo store.
Their XO was a first-order on the tweeter with series C and series/parallel Rs actually labelled "SEAS". The arrangement sounded OK, but I suspect the original design of the A-50 might be better. The pair of boxes lacked the "punch" that some people have used to describe the bass and low mids of the original A-50.

I have found the **outside** dimensions of the original boxes (28"x21.5"x10"). Three things I can't seem to find exactly are the dimensions/design of front baffle layout, the internal aperiodic vent or a XO schematic. I did find the A-50 XO on Planet 10 site, but also found a reference elsewhere that this could be slightly wrong. Someone suggested that 10R resistor should be in parallel with tweeter to form an Lpad. see attached .gif (Thanks to Dave Dlugos of Planet 10-hope it's alright to post this pic)

I also need to know thickness of original cabinets (3/4 chipboard??) or enclosure volume as i plan to make thicker walls and perhaps some bracing front-to-rear and side-to-side.
Also thought of making them as towers to avoid separate stands. Can anyone supply box plans and definitive XO schematic? Is there any advantage to making boxes bigger than original design? Or has anyone used these SEAS drivers in any other configuration eg d'appolito with tweeter between two mid-basses? Any suggestions for improvements on the original design would be appreciated. Please don't shoot me for posting such heresies in the Classic Dyanaco forum ;-)

regards

Ozziozzi;)

I don't suppose it has occurred to any owner of the A50 to just pull a woofer and measure the aperiodic vent between the two chambers? There are quite a few people that would be interested and very appreciative to know what those dimensions are. Thanx.....

#27 dynaco_dan

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Posted 06 April 2012 - 12:05 AM

Hi there

I took both of my rescued A-50's outside to clean up last week.

I took some photos and will post them and complete my write-up soon.

1. removed 99% of the black paint from the side panels.

2. I measured drivers, front and other outside measurements.

3. I took photos of before and after.

4. first cabinet has 99% mint walnut veneer.

5. second cabinet is like from another planet, terrible shape, paint hides lots of sins.

6. about one hour each so far.



20120410 added


Funny thing is that after all I've read about the A-50's being floorstanding speakers because of their size and weight, my cabinets have the recesses and wall mounting brackets attached.

I tried to post a few photos and was unsuccessful.
VERN

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