Jump to content


Photo
- - - - -

A25 Crossover Confusion


  • Please log in to reply
13 replies to this topic

#1 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 17 March 2011 - 03:51 PM

I have a pair of non-matched Dynaco A25s...one is, I believe, newer than the other. Same drivers (SEAS TV-EW woofers, SEAS 1.5 inch tweets) in both, and same five position crossover adjustment switch in the crossover.

I was planning to recap them, so did some reading and then opened one up. Consistent with info here and with other sources, the single cap in crossover was 5.0uf. So, I ordered a pair of caps.

They arrived, and I opened up the second speaker, cut out the cap and lo and behold it's an 8uF. More reading, and I find that the A25XL used an 8uF cap...but these speakers have the A25 drivers.

Upon further investigation, I find a 5uF cap glued to the back of the tweeter and wired in series with the first one. What the heck? I also found that the inductors in the variable fequency control have different values than those specified in the "official" A25 schematic.

Can anybody shed any light on what I've got here, and how I should proceed with recapping? By the way, the older of these speakers is the one with the odd two cap arrangement. The newer one has the single 5uF (and lighter gauge wiring, and a plastic screen for the baffle rather than metal....guess they were trying to reduce production costs as competition got tougher).

Sure would appreciate any insight or suggestions Thanks.

#2 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 17 March 2011 - 08:17 PM

I have a pair of non-matched Dynaco A25s...one is, I believe, newer than the other. Same drivers (SEAS TV-EW woofers, SEAS 1.5 inch tweets) in both, and same five position crossover adjustment switch in the crossover.

I was planning to recap them, so did some reading and then opened one up. Consistent with info here and with other sources, the single cap in crossover was 5.0uf. So, I ordered a pair of caps.

They arrived, and I opened up the second speaker, cut out the cap and lo and behold it's an 8uF. More reading, and I find that the A25XL used an 8uF cap...but these speakers have the A25 drivers.

Upon further investigation, I find a 5uF cap glued to the back of the tweeter and wired in series with the first one. What the heck? I also found that the inductors in the variable fequency control have different values than those specified in the "official" A25 schematic.

Can anybody shed any light on what I've got here, and how I should proceed with recapping? By the way, the older of these speakers is the one with the odd two cap arrangement. The newer one has the single 5uF (and lighter gauge wiring, and a plastic screen for the baffle rather than metal....guess they were trying to reduce production costs as competition got tougher).

Sure would appreciate any insight or suggestions Thanks.



Hi there

If you mean resistors, rather than inductors, then they should be 2.2 ohms each and a single resistor of 10 ohms.

Please take a few closeup photos of the drivers magnet labels so that we can determine their specific model and age.

Also if possible, a few of the crossovers inside and closeup.

Each of the outside switch and their label area as well.

As well the cap glued to the magnet, as this is not normal, so far historically at least.

I have never seen or heard of a metal vent screen, only plastic, there may be something to learn here.

A photo of each screen please, as well.

With these I have seen at least two different stapled mounting methods.

With all these photos we will be better able to help you and also learn more about the Dynaco classic speakers.
VERN

dynaco_dan2@yahoo.ca

#3 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 17 March 2011 - 10:52 PM

I'll take some pics later this afternoon/evening. And yes, I meant resistors...brain spasm. They are a mix of 2.2 and 4.7 ohms (of the four that I can read) in the speaker with the two caps.

I had a previous pair of A25s, but they were consistent with the "standard" model (TV-EW woofers, 1.5" SEAS tweeters, 5 position switch, 2.2 ohm resistors plus a single 10, wire mesh vent screen, reddish stain/paint on the front and rear).

Of my current two speakers, the one that has the "standard crossover" is the one with the thinner wiring and plastic mesh vent cover. It also has a slightly different front plate from the others...it's black, and the inset for the tweeter is a bit deeper.

Pics to follow. Thanks very much for your interest.

SF

#4 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 18 March 2011 - 02:16 AM

I've uploaded quite a few, very detailed pics to a Photobucket site, as follows:

http://s1105.photobu...57/kcbluesman1/

Photos of the speaker with the standard crossover version all have a prefix of "SCV". The one with the unusual crossover have a prefix of "Alien"

To summarize:

SCV Speaker
  • Black front panel
  • Black speaker screws
  • Plastic mesh vent cover
  • Lighter gauge wiring
  • Deeper tweeter inset
  • 2nd layer of backwall insulation is in two lengthwise panels
  • Crossover has standard resistors (5 x 2.2 ohm plus 10 ohm) and one 5uF Jensen cap

Alien Speaker
  • Reddish front panel (like other A25s I've seen)
  • Silver screws
  • Wire mesh vent cover
  • Heavier gauge wiring
  • Shallower tweeter inset
  • 2nd layer of backwall insulation is in one piece
  • Crossover has higher value resistors, 8uF cap at the switch and 2nd 5uF cap in series, glued to back of tweeter. Caps are both Jensen.


#5 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 18 March 2011 - 03:11 AM

[quote name='kcbluesman' timestamp='1300414616' post='87002']
I've uploaded quite a few, very detailed pics to a Photobucket site, as follows:

Hi again

You have uploaded a lot of photos but you did not upload them here, for us to help you.
VERN

dynaco_dan2@yahoo.ca

#6 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 18 March 2011 - 03:57 AM

Well, I thought using a photo server would be easier, but I'll attach them here as well.

BothDynacos2_1_1.JPG SCVFront_1_1.JPG SCVTweet1_1_1.JPG SCVTweet2_1_1.JPG SCVPlaticVentCover_1_1.JPG SCVCrossover1_1_1.JPG SCVCrossover2_1_1.JPG SCVBackPanel_1_1.JPG SCVWoofer_1_1.JPG SCVRear_1_1.JPG AlienFront_1_1.JPG AlienTweet_1_1.JPG AlienVent_1_1.JPG AlienWoofer_1_1.JPG AlienCrossover1_1_1.JPG AlienCrossover2_1_1.JPG Alien2ndCap@Tweet_1_1.JPG Alien2ndCap@Tweet2_1_1.JPG AlienBackPanel_1_1.JPG AlienRear_1_1.JPG

#7 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 18 March 2011 - 11:57 PM

Well, I thought using a photo server would be easier, but I'll attach them here as well.


Hi again

Thank you for posting those great HD photos here.

I deleted them from this reply to keep duplicating large files which are overloading the system.

From my point of view I see a tweeter manufactured the 47th week of 1968 and the other the 18th week of 1972.

Officially the Dynaco A-25 was first announced in 1969, exact date unknown.

The date of the older tweeter could be well within a reasonable early time period of an A-25 manufacture.

My guess is that the older, non-A-25 unit, has the tweeter mounted cap, the odd value resistors and the metal mesh.

The metal screen will be the very first I have seen on a Dynaco speaker, the plastic one is the usual one.

The weight of the cabinet must be horrendous with all those screen staples. LOL

The age of the oldest unit pre-dates the Dynaco A-25 and it may be a B&O, Seas or Scan product speaker system, not a Dynaco A-25.

It also is not the 4 ohm version that Dynaco's rep, Ed Laurent, requested be made for them in an 8 ohm version only.

The fact that the newer unit has the tweeter on the right side of cabinet center is normal, but, left of cabinet center tweeters photos have been posted as well.

A photo of those woofer magnets and their labels would be greatly appreciated, please.

If you do upload them here we can tell you some more.
VERN

dynaco_dan2@yahoo.ca

#8 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 19 March 2011 - 12:27 AM

Thanks for the info.

You asked for pics of the woofers magnets...that's what I already posted. You will note the TV-EW on the label, along with the production date. "Dynaco" is stamped on the bottom of the woofer.

The cabinet design is identical to the A25, the drivers are identical to those used in the A25, the drivers carry the Dynaco name, and the grill cloth (which is indentical to that of the other one) has a Dynaco badge. While I certainly defer to your expertise, I think I would conclude that it IS a Dynaco speaker identical in all pertinent respects to an A25, but with a non-A25 crossover (and, as a result, with a much higher crossover point). This could have been some sort of pre-production or prototype version.

By the way, an acquaintance of mine here in town has two pairs of A25s....both with metal mesh vent covers.

I plan to re-build the crossover of this non-A25 Dynaco speaker to the A25 design, so as to give me a matched pair (from a sound standpoint). However, in a way I hate to destroy this historical aberration. Do you think that there may be a collector/Dynaco buff who would want this speaker and would be willing to swap a "standard" A25 for it?

Thanks again for your help.

Steve

#9 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 19 March 2011 - 04:13 AM

Thanks for the info.

You asked for pics of the woofers magnets...that's what I already posted. You will note the TV-EW on the label, along with the production date. "Dynaco" is stamped on the bottom of the woofer.

The cabinet design is identical to the A25, the drivers are identical to those used in the A25, the drivers carry the Dynaco name, and the grill cloth (which is indentical to that of the other one) has a Dynaco badge. While I certainly defer to your expertise, I think I would conclude that it IS a Dynaco speaker identical in all pertinent respects to an A25, but with a non-A25 crossover (and, as a result, with a much higher crossover point). This could have been some sort of pre-production or prototype version.

By the way, an acquaintance of mine here in town has two pairs of A25s....both with metal mesh vent covers.

I plan to re-build the crossover of this non-A25 Dynaco speaker to the A25 design, so as to give me a matched pair (from a sound standpoint). However, in a way I hate to destroy this historical aberration. Do you think that there may be a collector/Dynaco buff who would want this speaker and would be willing to swap a "standard" A25 for it?

Thanks again for your help.

Steve


Hi again

I was in too much of a hurry to go out for dinner and did not look at that detail, sorry about that.

The magnet labels date and 8 ohms and I didn't check the model number or notice the dark woofer basket.

The time period is still valid though, just the woofers dates now, rather than the tweeters.

Unless you can photo the tweeters as well?

You have peeked my interest more so now.

What country do you live in?

I am assuming not in the the USA, perhaps Europe, Denmark?

I don't see the name Dynaco on the woofer paper labels, just Seas.

Pre-production or prototype could be a possible answer, less likely with your friend having some as well.

The fact that your friend has the same metal screen raises some interest again.

Looking at the unit with the reddish front, it looks like the later USA assembled cabinets.

I would suggest not changing any resistor or cap values until we know more.

This speaker was designed with a different crossover network construction, we just need to find out some more information first.

The name Dynaco was sometimes stamped onto the magnets backplate, woofers and tweeters.

The reddish cabinets grille cloth frame was glued to the cabinet differently and the tweeters screwed with different screws and with

more of them, than the standard norm as well.

When I serviced 150 - 200, Dynaco A-25's, in less than 2 years, part time, at our local Dynaco warantee depot, replacing woofers.

I saw only the very occassional Scan woofer, which was automatically replaced with a Seas 10" woofer.

The cabinet required a small chisel notch to allow for their horns.

Seas, with horns, were the only replacement woofers we ever received direct from Dynaco.

Sadly, I do not see the Dynaco serial number stickers, that would make this a whole lot easier.

I see also that you likely removed the red cabinets grill cloth prior to unscrewing the Dynaco badge.

If you cannot salvage that badge, they are listed on ebuy, all the time, about $15.00 a pair.

I just did a quicky check of my spare woofers, 1 pair horned Seas 25 TV - EW and 1 pair of round Seas 25 TV - EW.

Both have the same magnets as you show in your photos, and are typical in the Seas tweeters as well.

We will all learn more soon.
VERN

dynaco_dan2@yahoo.ca

#10 kcbluesman

kcbluesman

    Advanced Member

  • Members
  • PipPipPip
  • 36 posts
  • Gender:Male
  • Location:Kansas City
  • Interests:Music, flyfishing, hiking, camping, reading, golf.

Posted 19 March 2011 - 05:03 AM

I live in Kansas City.

The Dynaco name is stamped on the bottom of the woofer magnet in the mystery speaker.

As I said, I do have mixed feelings about modifying this speaker, but my goal is to have a pair of A25s. The only way I can do that is by replacing the existing crossover with an A25 crossover.

That's my plan, unless somebody who wants this unusual unit pops up in the next week or so and wants to trade it for a standard A25. I haven't ordered the parts yet, so probably won't have them until late next week.

Take care.

#11 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 19 March 2011 - 06:03 AM

I live in Kansas City.

The Dynaco name is stamped on the bottom of the woofer magnet in the mystery speaker.

As I said, I do have mixed feelings about modifying this speaker, but my goal is to have a pair of A25s. The only way I can do that is by replacing the existing crossover with an A25 crossover.

That's my plan, unless somebody who wants this unusual unit pops up in the next week or so and wants to trade it for a standard A25. I haven't ordered the parts yet, so probably won't have them until late next week.

Take care.


Hi again

I would suggest leaving any mods until more members can see this topic and add their experiences to this topic.

Obviously this crossover network was designed for this particular speaker, different from the norm or not.


This now Monday.

I have just scanned an English Magazines 2 page review of the A-25 from 1969.

There is no date or magazine name, just the reviewers name, Clement Brown.

It is your speaker, multiple staples around the mesh, my guess is that the mesh is also metal.

All 8 tweeter screws are shiny and also shiny woofer screws.

The usual screws are dark and usually only 4 screws are used for the tweeter.

The woofer has the horns, which would confirm it is a Seas woofer at least.

No mention of the crossover components, even though the woofer was removed for a photo shoot.

From all appearances the tweeter is a Seas as well.

The reviewer did not mention if the mesh was metal or plastic.

These were seen at a 1969 hifi show, just prior to this review, and the A-25 were just being introduced there then, as a brand new product.

When you first came here, I remembered that the A-35 has the 8 uf cap and A-25 has a 5 uf cap.


Monday evening now.

My uploading priviledges have been restored, thank you.

Here is the review I was referring to.

Ratty looking paper, but great reading.

Attached Files


VERN

dynaco_dan2@yahoo.ca

#12 DesignInc

DesignInc

    Member

  • Members
  • PipPip
  • 11 posts
  • Gender:Male
  • Location:Central Coast, California

Posted 31 March 2011 - 06:36 PM

"I have just scanned an English Magazines 2 page review of the A-25 from 1969.
There is no date or magazine name, just the reviewers name, Clement Brown."

Thanks so much Vern

The review is a great addition to my info collection. I guess I lucked out getting a pair of A-25 all original for $5 thankfully someone had stained the top of one and the grills were stained as well but that's probably why I got them!

I'm planning to recap with AuriCap's 5.0uf ($23ea at Parts Express) but before I pull the woofers I want to use the most authentic sealer when I put them back in what do you suggest? The black gooey stuff seems to have worked so well for 40 years!

Dynaco_A25_grillfrt_572.jpg
Dynaco_A25_off_572.jpg
Allison Ones - Allison Fours - Dynaco A25 - AR-2ax - Paradigm -

#13 dynaco_dan

dynaco_dan

    dynaco_dan

  • Members
  • PipPipPip
  • 2,873 posts
  • Gender:Male

Posted 01 April 2011 - 02:03 AM

"I have just scanned an English Magazines 2 page review of the A-25 from 1969.
There is no date or magazine name, just the reviewers name, Clement Brown."

Thanks so much Vern

The review is a great addition to my info collection. I guess I lucked out getting a pair of A-25 all original for $5 thankfully someone had stained the top of one and the grills were stained as well but that's probably why I got them!

I'm planning to recap with AuriCap's 5.0uf ($23ea at Parts Express) but before I pull the woofers I want to use the most authentic sealer when I put them back in what do you suggest? The black gooey stuff seems to have worked so well for 40 years!



Hi again

Working at the local Dynaco warantee depot here I just reused the excessive and fresh pretty bluey/green gunk.


Correction to that statement: We also used strips of 3m auto body putty when there was more sealant needed.


How have you made out thus far, with information and your crossover?
VERN

dynaco_dan2@yahoo.ca

#14 Horswispr

Horswispr

    Advanced Member

  • Members
  • PipPipPip
  • 220 posts

Posted 06 May 2011 - 06:17 AM

Hello, Gentlemen. I just put together a pair of Dynacos, one a "red front" and one a "black front," like the pair in question here. However, mine are normal in all other respects. Interestingly, the wires inside the (later?) red-front did appear to be thicker than those in the black-front Dynaco. Also, the capacitor in the red-front was a 4.7, the lowest I've encountered in a Dynaco A-25. The other was a 5.0 or 5.1; I forget which. I replaced both with Dayton 5.1s and they sound fine. My first thought was that the "mystery" speaker discussed here had been tampered with by someone trying to achieve a ceratin sound, but that was only because I've never heard of a Dynaco A-25 with anything other than a single capacitor. Based on the pictures, I can't see any reason to believe that both aren't Danish-made A-25s; most Denmark A-25s have Made in Denmark stamped on the back near the terminals. I admit, though, that I don't think I've ancountered wire mesh over the vent, and I must have refinished 50 pairs of Dynaco A-25s. Could that have been done "after-market" as well?

If any new info comes in, pleast post. My curiosity has been piqued. By the way, is it "known" that the red front Dynacos are "later"? Or is that conjecture? These were two singles I scored over a two year period. The red-front has a paper tag which reads 059016 on the back. The black-front has no tag (and I'm not up to opening it up to look at the tweeter; I had to replace the woofer), but it looks like a pair I had that was bought in 1972 or so.

-----

Working at the local Dynaco warantee depot here I just reused the excessive and fresh pretty bluey/green gunk.


Correction to that statement: We also used strips of 3m auto body putty when there was more sealant needed.


How have you made out thus far, with information and your crossover?
[/quote]
--Horse




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users