Dynaco A25 -Hard to Believe

I was underwhelmed by the A25.  I had a first series pair- ScanDyna labeled, with a port ON TOP rather than the usual bottom location.

I thought bass was fine, but treble was very recessed.    Looking at the curves for the new version, and reading reviews from back in the day that also included FR curves gives some insight into the design.   Henry Kloss once said that lack of extreme FR extension can be managed if both extremes roll off smoothly and both rolloffs are balanced.   The A25 had great deep bass, but started to rolloff below 100hz.   Treble would extend to about 15khz, but only on axis, and would fall off noticeably off axis at 10khz.   In typical listening rooms, with typical early SS equipment this was a great match.   And efficiency was slighlty better than the AR4 meaning it could play louder and cleaner with a modestly powered receiver.    

I have owned my own pair of Dynaco A-25s since 1971. I bought them when I was at university, from another guy living on my floor in the dormitory. He needed quick cash and I had desperately coveted his stereo system. It consisted of those Dyna A-25s, an Acoustic Research integrated amplifier, a Dynaco FM3 stereo FM tuner and a Thorens TD-160 turntable. Lastly, I added a Sony TC-366D open reel tape deck my dad gave me as a Christmas gift. At the time, this was close to as inexpensive and good a stereo system as someone like me, with high-end tastes and low-end money could get.

My components changed over the decades, but I've never been able to bring myself to sell the A-25s. They just sounded musical in intangible ways that many much more expensive speakers didn't.

About 10 years ago, I noticed they were just not performing as I remembered them from when they were new. I wasn't sure if it was me going deaf, or simply my audio tastes "evolving," or whether their performance really was deteriorating. By then, I was living in Madison, WI. In Middleton, a Madison suburb, is a great resource, Madisound Speaker Components. Primarily, they sell loudspeaker components to manufacturers, auto stereo installers and DIYers. They also offer loudspeaker kits and design assistance for speaker enclosures and crossovers. Madisound told me that the speakers at the very least needed new capacitors. They also offered a replacement dome tweeter by SEAS that SEAS, the A-25s' manufacturers, offered as a drop-in upgrade/replacement for the original. SEAS claimed the new tweeter offered better high-range extension and dispersion.

I bit. I bought new capacitors that Madisound assured me were much better quality than the originals were when new. I also bought the drop-in replacement SEAS tweeters.

The basic sonic signature of the A-25s was unaltered. But the high frequencies were more extended. There was noticeably more detailed high end. More importantly, the speakers just disappeared! I listen primarily to jazz and classical music. The instruments were spread in front of, in the background, evenly across the soundstage. These 40-year-old speakers that originally sold for $160 per pair in 1971 - about $1,000 in 2020 dollars, actually showed really good stereo imaging qualities.

So these are now my primary speakers again. Another outstanding quality of the A-25 was their very natural reproduction of voices, especially male voices. Solo voices, choral recordings sound more real and natural through these speakers than through most speakers I could buy today for less than $1,000 per pair. Strings and piano are also very realistic through these speakers.

Bass is tight and detailed, if not especially extended. Many bookshelf speakers that are otherwise of good quality disguise their lack of deep bass with a broad rising characteristic over the 60Hz - 120Hz octave and rather loose bass transient response - especially among bass-reflex ported designs. I remember that test reports from high-fi publications at the time praised the A-25 and its unique quasi-transmission line aperiodic enclosure design for its ability to reproduce recognizable bass range square waves, attesting to their excellent bass transient response. In other words, the bass that is present is accurate, not flabby and over-emphasized.

I don't miss having a subwoofer on music listening. Orchestral basses are reproduced well, as are pipe organs. 32-foot organ pedals and orchestral bass drums come up out of the floor as they should. But I DO miss a subwoofer on movie sound tracks. Yes, I use these as my speakers for home theater too. Their imaging is good enough that dialogue through the virtual center is properly placed and understandable, so I feel no need for a center channel. But booms, explosions and other sound effects do lack that impact that a subwoofer would provide.

The bottom line is that I HAVE heard better speakers. But none more musical, at least not for any price I can afford to spend.

SEAS A26 kit owner here. Purchased the kit in Canada from Solen with the big SEAS T35 tweeter. The cap used in their kit is a Solen Metalized Poly cap and it’s in series with a 10 ohm resistor.

Sounds good to me.

A friend of mine built a birch ply cabinet and it was stained.  The cabinet is 'solid'.

The plan was to clone an A35 cabinet with the kit. It did not work out well. But the end result is awesome and I’ll explain why.

We built a 35 litre cabinet instead of the recommended A26 cabinet: the 35 litre cabinet is a bit bigger. You can google A35 cabinet and you’ll find old dynaco drawings.

As the bass was not very good, I decided that this initiative was not a good path to follow.

I removed the internal vent and installed it on the rear cabinet panel. I then punched more holes in the internal mid-section brace, essentially creating an open cabinet of 35 litres with a mid-ship brace. Buttoned everything up.

So how do they sound after the mods? Very good. As a matter of fact, while the bass is not as deep as my Dynaudio Special 40s that I had on hand to compare, they were an enjoyable speaker to listen to for hours on end. 

I use an RME ADI-2 DAC and I did some EQ’ing to tune the speaker to my preferences: I benchmarked a harbeth 30.1 for comparison purposes. I added a bass boost of 2.5 db at 120 hz with a Q of 1.5; and a mid-range boost of 2.5 db at 1600 Hz with a Q of 1.3 (if memory serves me well). The mid-range boost was critical to match up with the Harbeth and provide a magical mid-range.

And that is that: a 35 litre cab with a round aperiodic port at the back and a bit of EQ and it’s magic.

The speaker is powered by a Benchmark AHB2. It’s just one of those speaker that you listen to and think, yeah, this is all I need to be happy.

 

Nice to see this as I have a history with A-25s.  I didn't own them during the '70s when they sold in large numbers, but a local record store had two pair mounted at angles where the walls met the ceiling at either end of the room.  I was always fascinated by the musical pleasures in hearing those whenever I visited that store.

Sometime in the '80s I was between systems when I found a clean pair for a good price.  After listening a bit I decided a couple of simple mods might be fun.  So I glued in a wood brace inside each sidewall just above the woofer, then removed the metal screen that covered the tweeter.  I was pleased with the results and kept them as my main speakers for several months, until a friend pestered me until I sold them to him.

With those memories I came across a 1-owner pair at a garage sale when record shopping.  Even had the original shipping cartons!  So I bought those, "just in case".  That was a few years ago, now I'm thinking of resurrecting them to set up with a large flat screen for movies and concert videos.  Reading this post, which I don't remember seeing, encourages me to try that.