Dynaco A-25 "upgrade"?

[Tavi]

Ok so thanks to a lot of suggestions and digging through the forum I acquired a pair of Dynaco A-25VW's for my newly rebuilt ST-70 to drive. I'm so impressed at what these 35+ year old speakers can do! Taking a step back from a complicated Denon 5.1 system to an old and very simple 2.0 system has been a real eye opener! Ok so now that I have a respectable point of reference, the next question is: What is a modern large bookshelf speaker that is at least as good sounding as the A-25's? Most of the modern bookshelf speakers I see use a 6.5" woofer at the most. I can't imagine that they would go as low as the 10" woofer in the A-25. I guess they assume that everyone is using a subwoofer nowadays. So...is there any modern equivalent to the venerable A-25 that is as good as or better then an A-25 in a 2.0 setup? The Klipsch RB-81 seems as close as I can find but it has only an 8" woofer. Has anyone bent the rules of physics in the past 30 years and come out with a design that can go as low as a 10" woofer with a 6.5" woofer? I'm not dying to run out and spend money, I'm just a born again music listener, so if you think what I have is "good enough" say so! Oh, I'm aware of the Madisound reproduction product. It's too expensive and impossible to find used. I'm also aware of the Klipsch Forte series. Too big for the moment but a future possibility. Thanks for reading.

 

[Swerd]

I remember the A-25s. They were very popular in the 60s and 70s.

Their problem is that they are a 2-way speaker with a 10" woofer and a small (1½"?) dome tweeter. The woofer can't go high enough, with enough off-axis sound, to mesh well with the tweeter. It's a smooth sounding woofer, and has no ugly sounding problems at the high end of its range. But it still results in a mid range sound where there is a "hole in the middle". Many listeners (like myself at one time) were used to that sound and didn't realize what was missing. That is the main reason why no one sells 2-way speakers like that now.

Don't underestimate modern 6½" woofers. Woofers that size in the 70s couldn't produce enough bass, especially when compared to larger woofers, but today's designs are better. And they sound significantly better at their upper range, where they crossover to the tweeter. Also, tweeter manufacturers abandoned for the most part 1½" to 2" dome tweeters a long time ago. Modern tweeters (1" domes and other types like ribbons) are much better all around performers than those early domes.

As a suggestion, consider the Philharmonitor http://philharmonicaudio.com/. It's a 2-way with a 6½" woofer that can go as low as 42 Hz, and a ribbon tweeter, where the frequency response is smooth and nearly flat, especially across the mid range, http://philharmonicaudio.com/philharmonitor.html

 

[Dennis Murphy]

Ok so thanks to a lot of suggestions and digging through the forum I acquired a pair of Dynaco A-25VW's for my newly rebuilt ST-70 to drive. I'm so impressed at what these 35+ year old speakers can do! Taking a step back from a complicated Denon 5.1 system to an old and very simple 2.0 system has been a real eye opener! Ok so now that I have a respectable point of reference, the next question is: What is a modern large bookshelf speaker that is at least as good sounding as the A-25's? Most of the modern bookshelf speakers I see use a 6.5" woofer at the most. I can't imagine that they would go as low as the 10" woofer in the A-25. I guess they assume that everyone is using a subwoofer nowadays. So...is there any modern equivalent to the venerable A-25 that is as good as or better then an A-25 in a 2.0 setup? The Klipsch RB-81 seems as close as I can find but it has only an 8" woofer. Has anyone bent the rules of physics in the past 30 years and come out with a design that can go as low as a 10" woofer with a 6.5" woofer? I'm not dying to run out and spend money, I'm just a born again music listener, so if you think what I have is "good enough" say so! Oh, I'm aware of the Madisound reproduction product. It's too expensive and impossible to find used. I'm also aware of the Klipsch Forte series. Too big for the moment but a future possibility. Thanks for reading.

I owned a pair of 25's for many years, and liked them almost as much as my KLH 5's. There was no crossover on the woofer--it just ran on its own until it rolled off naturally. That generally doesn't work, but it did with this woofer, and it generally mated well with the large tweeter. I can't say as I heard a hole in the middle. In fact, it sounded almost identical to my KLH's, which had two dedicated acoustic suspension midrange drivers. The 25's main limitation was air at the very top. The Seas tweeter went low, but not real high. So there's probably not much going on above 15 kHz. A well designed 6.5" driver in a properly optimized bass reflex enclosure will go lower than the 25's, which ran sealed, although it was technically aperiodic, with a small opening to damp the woofer's impedance peak. That never really worked, and it performed like a sealed driver in a cabinet that was awfully small for a 10" driver. But at least it wasn't boomy. Overall, I would take the A25 over the vintage AR 3a's or 2ax's any day. Much smoother response where it mattered. I would just enjoy them.

 

[Swerd]

I owned a pair of 25's for many years, and liked them almost as much as my KLH 5's. There was no crossover on the woofer--it just ran on its own until it rolled off naturally. That generally doesn't work, but it did with this woofer, and it generally mated well with the large tweeter. I can't say as I heard a hole in the middle. In fact, it sounded almost identical to my KLH's, which had two dedicated acoustic suspension midrange drivers. The 25's main limitation was air at the very top. The Seas tweeter went low, but not real high. So there's probably not much going on above 15 kHz. A well designed 6.5" driver in a properly optimized bass reflex enclosure will go lower than the 25's, which ran sealed, although it was technically aperiodic, with a small opening to damp the woofer's impedance peak. That never really worked, and it performed like a sealed driver in a cabinet that was awfully small for a 10" driver. But at least it wasn't boomy. Overall, I would take the A25 over the vintage AR 3a's or 2ax's any day. Much smoother response where it mattered. I would just enjoy them.

Interesting. That's better than I remembered, but I never owned them. They were much better sounding than the KLH 17, another 2-way with a larger woofer.

Perhaps the A-25s and the tube amp may be alright together. Neither the speaker nor the amp can deliver at the very high frequencies, and that may not matter to the owner.

Tavi: Be aware that the above poster, Dennis Murphy, is the owner of Philharmonic Audio .

 

[Bill Gobby]

Ok so thanks to a lot of suggestions and digging through the forum I acquired a pair of Dynaco A-25VW's for my newly rebuilt ST-70 to drive. I'm so impressed at what these 35+ year old speakers can do! Taking a step back from a complicated Denon 5.1 system to an old and very simple 2.0 system has been a real eye opener! Ok so now that I have a respectable point of reference, the next question is: What is a modern large bookshelf speaker that is at least as good sounding as the A-25's? Most of the modern bookshelf speakers I see use a 6.5" woofer at the most. I can't imagine that they would go as low as the 10" woofer in the A-25. I guess they assume that everyone is using a subwoofer nowadays. So...is there any modern equivalent to the venerable A-25 that is as good as or better then an A-25 in a 2.0 setup? The Klipsch RB-81 seems as close as I can find but it has only an 8" woofer. Has anyone bent the rules of physics in the past 30 years and come out with a design that can go as low as a 10" woofer with a 6.5" woofer? I'm not dying to run out and spend money, I'm just a born again music listener, so if you think what I have is "good enough" say so! Oh, I'm aware of the Madisound reproduction product. It's too expensive and impossible to find used. I'm also aware of the Klipsch Forte series. Too big for the moment but a future possibility. Thanks for reading.

You could check out the Tannoy line, they still have large woofer.
Ottguit

 

[Bill Gobby]

I owned a pair of 25's for many years, and liked them almost as much as my KLH 5's. There was no crossover on the woofer--it just ran on its own until it rolled off naturally. That generally doesn't work, but it did with this woofer, and it generally mated well with the large tweeter. I can't say as I heard a hole in the middle. In fact, it sounded almost identical to my KLH's, which had two dedicated acoustic suspension midrange drivers. The 25's main limitation was air at the very top. The Seas tweeter went low, but not real high. So there's probably not much going on above 15 kHz. A well designed 6.5" driver in a properly optimized bass reflex enclosure will go lower than the 25's, which ran sealed, although it was technically aperiodic, with a small opening to damp the woofer's impedance peak. That never really worked, and it performed like a sealed driver in a cabinet that was awfully small for a 10" driver. But at least it wasn't boomy. Overall, I would take the A25 over the vintage AR 3a's or 2ax's any day. Much smoother response where it mattered. I would just enjoy them.

No Crossover, wow.
What does that 5 way switch on the back do to the tweeter?
Ottguit

 

[Dennis Murphy]

No Crossover, wow.
What does that 5 way switch on the back do to the tweeter?
Ottguit

HI. The tweeter did have a high pass filter on it. Otherwise it would burn up. But most of the components were resistors controlled by the back switch. The switch would make contact with different value resistors when it changed position, and lower the tweeter output. I forget how many positions there were. They probably sound best with the switch in the highest position.

 

[Dennis Murphy]

Interesting. That's better than I remembered, but I never owned them. They were much better sounding than the KLH 17, another 2-way with a larger woofer.

Perhaps the A-25s and the tube amp may be alright together. Neither the speaker nor the amp can deliver at the very high frequencies, and that may not matter to the owner.

Tavi: Be aware that the above poster, Dennis Murphy, is the owner of Philharmonic Audio .

Right--the 17 was a disaster. The woofer had a huge peak at 1900 Hz and no crossover to suppress it. The original was super popular because it was cheap, the competition was worse, and it had a lot of bass for the money. The A25 was basically the 17 done right.

 

[macddmac]

Seas designed a kit named the A-26 based on the A25:
https://www.madisoundspeakerstore.com/2-way-speaker-kits/seas-a26-10-2-way-kit-pair-based-on-the-classic-a25/
Cheers, Mac

 

[slipperybidness]

As a suggestion, consider the Philharmonitor http://philharmonicaudio.com/. It's a 2-way with a 6½" woofer that can go as low as 42 Hz, and a ribbon tweeter, where the frequency response is smooth and nearly flat, especially across the mid range, http://philharmonicaudio.com/philharmonitor.html

I do love my pair of Philharmonitors....but, I would not recommend them for a Dynaco ST-70.

The Phils sound better on my Parasound 1206. In my experience, my ST-70 just doesn't have the power to drive the Phils to their full potential. It may also be the unforgiving nature of the Phils. And, keep in mind that my ST-70 is new with the updated boards and circuits, and not a rebuilt vintage model.

If the listener will be in a small room, near field, and use a sub, then the Phils may be OK on the ST-70. Otherwise, my experience says to look elsewhere.

Personally, the DT350 seem to mesh the best with my ST-70 (I have tried the Phils, P363, and SM350. I will hook my ST70 to my Triton 2 eventually).

Edit: I should mention, I did an update on my ST-70 to have the option of 4 ohm or 8 ohm output taps. I did notice some overall improvements when I went to the 4 ohm taps for the Phils. But, still didn't perform like SS amps. I suppose that if you never had SS amp for a direct comparison on the Phils, then you might never know the difference.

Bob Latino recommended that if you only go with 1 set of taps, then do the 8 ohm taps. However, my experience with the speakers available to me, says that the 4 ohm taps are a better option. YMMV.

 

[Swerd]

I do love my pair of Philharmonitors....but, I would not recommend them for a Dynaco ST-70.

The Phils sound better on my Parasound 1206. In my experience, my ST-70 just doesn't have the power to drive the Phils to their full potential. It may also be the unforgiving nature of the Phils. And, keep in mind that my ST-70 is new with the updated boards and circuits, and not a rebuilt vintage model.

Good point. You've actually had the experience of listening to these speakers driven by both the ST-70 and other SS amps.

 

[slipperybidness]

Good point. You've actually had the experience of listening to these speakers driven by both the ST-70 and other SS amps.

Yup. And, I will recommend the Philharmonitors for most people and most situations, assuming SS amps.

For the ST-70, I originally expected that the Phils would be at home with that amp. But, my experiments led me to believe otherwise.

I ended up running the ST-70 on my synth/drum machine, feeding the P363. Worked out great for that purpose.

 

[Tavi]

'Personally, the DT350 seem to mesh the best with my ST-70 (I have tried the Phils, P363, and SM350. I will hook my ST70 to my Triton 2 eventually)."

Is DT350 Definitive Technology 350?

 

[slipperybidness]

'Personally, the DT350 seem to mesh the best with my ST-70 (I have tried the Phils, P363, and SM350. I will hook my ST70 to my Triton 2 eventually)."

Is DT350 Definitive Technology 350?

Yup.

I got mine for $200 on Newegg. Normal price is $300, and personally I would not pay that much.
http://www.newegg.com/Product/Product.aspx?Item=9SIA0AJ1C67958&cm_re=definitive_technology_350-_-82-325-059-_-Product

I would have to guess that the SM450 would actually be better, but I would not pay $500 for those. I have seen them as low as $300 a pair on Newegg
http://www.newegg.com/Product/Product.aspx?Item=9SIA0AJ1YV3780&cm_re=definitive_technology_450-_-82-325-060-_-Product

 

[ski2xblack]

...the 25's, which ran sealed, although it was technically aperiodic, with a small opening to damp the woofer's impedance peak. That never really worked, and it performed like a sealed driver in a cabinet that was awfully small for a 10" driver. But at least it wasn't boomy. Overall, I would take the A25 over the vintage AR 3a's or 2ax's any day. Much smoother response where it mattered. I would just enjoy them.

So it actually did work, kinda, sorta. ( I've been messing w/ aperiodic boxes for testing and diy dabbling and found them kind of surprising in their trade off of extension and sensitivity, and lack of boom, easy to tune and play with.)