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Dynaco A-25

Aperiodic Loudspeaker System (1971-72)

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Dynaco A-25


The Dynaco A-25 aperiodic loudspeaker is a compact, high performance two way speaker system.

A 10 inch extended excursion woofer is matched to a specially designed soft dome tweeter with a dual section high pass filter at 1500Hz, in a cabinet design which achieves a uniquely non-resonant bass response.

The aperiodic, or non-resonant characteristic of the A-25 provides an unusally uniform impedance characteristic throughtout the bass range of less than 2 in 1.

This design utilises an acoustic impedance system which provides variable volume action rather than the totally enclosed cabinet of the acoustic suspension principle or the tuned port of the bass reflex.


Type: 2 way, 2 driver loudspeaker system

Frequency Response: 30Hz to 15kHz

Power Handling: 35W

Recommended Amplifier: 60W (maximum)

Crossover Frequency: 1500Hz

Impedance: 8Ω

Bass: 1 x 10" extended excursion

Tweeter: 1 x soft dome

Finish: oiled walnut, rosewood, teak


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Reviewed May 26th, 2019 by robinhood1940

So easy to listen to for hours on end.

Reviewed Sep 25th, 2017 by M.Tours

Fantastic loudspeaker. I like the aperiodic system in which a loudspeaker is not open or closed, but in between. Air inside the loudspeaker makes fibres in the slit move, thus eating up most -out of fase- waves. The woofer makes greater excursions without loss of control. This gives it a freedom of boxiness, while retaining firm bass. Most Dynaco A25's have Alnico magnets (Aluminium for strenghth and Nickel and Cobalt for magnetism), very nice motor for the system. The dometweeter is more usefull for parties (big size) it lacks some top-end. I replaced it for Morel MDT-20's. Same mid, but higher top-end. These seem not available anymore. But SEAS or Scanspeak might have other options.

Reviewed Aug 26th, 2017 by AudioGMan

I bought a pair to hear what all the hoopla was about and I have to admit they sound pretty good for what they are. Good imaging and excellent transient response in the proper setting. Easy to drive due to the aperiodic design that helps flatten the impedance curve. Vocals are well defined and the minimalist design approach is a testament to the use of carefully selected drivers. The cabinets are small enough to actually be used on a bookshelf. Unusual for a 10 woofer speaker. As with most speakers of this era this style grill has always been ugly in my opinion but those can be redone. I always listen without the grills and like AR and Advent they won't win a beauty contest with the grills off. I dislike the tweeter pot design and think replacing that with a continuously variable pot would be better and more reliable. The capacitor looks like a big waxy paper style so a better modern one would probably improve the tweeter's sound. These speakers are best suited for a small to medium room as they can't handle a whole lot of power. If you want a speaker that can play loud for an extended amount of time look elsewhere or you'll be smelling overheated voicecoils. Use a powered subwoofer if you want low bass so that the Dynacos can shine. All in all I think they are great speakers but not so much that they justify what they sell for. But like with other vintage speakers people are paying ridiculous prices for them.



tom rogers's picture

re: A-25

I have a pair of the A-25's sitting in near-field on this desktop. They sound incredible. Any complaints about the HF of the tweeter are nullified in near-field. I'm a bit of a basshead, and I love how full and lush is the bass from this relatively small enclosure.

I do have to be careful with them, however, as I have a 200+watt/ch. Adcom GFA-555 powering them. I will say though that they easily fill this small room with plenty of great sound. I usually have a pair of Klipsch RP-160m's for this near-field setup, but I do prefer the sound quality of the Dynacos. For my tastes, I think the going price for a pair is just right. For a bit more you can upgrade the tweeters if you want, or even find a schematic for a crossover upgrade. Neither option is cheap, though you can make do with a Parts Express tweeter that matches the impedance and other driver specs close enough to work and costs quite a bit less than a Scanspeak version.

This website is not affiliated with or sponsored by Dynaco. To purchase A-25 spares or accessories, please contact the company via their website or visit an authorised retailer.