Scandyna Rebuild Underway.
Posted: Fri Apr 21, 2017 4:57 pm
I've bitten the bullet and acquired the wood and started on the baffle cutouts.
I've been mulling the project over for at least a year or so and the result of my Doc Modded Omar standmounters has convinced me to go ahead. Prior to these, I'd run a pair of stand mount Scandyna A30 speakers for a couple of years
Essentially I've taken the drivers, a 10 inch SEAS bass/mid and dome tweeter from the Scandyna A30 cabinets and they will go into a sealed 33 litre (net) two chamber floorstander with the two sections split about 55/45 and the top larger section venting via an aperiodic port into the smaller lower section. At higher frequencies, the drivers 'see' just the top section. At the lowest frequencies the top chamber vents into the lower one, so the driver sees the larger box. The impedance of the main driver is lowered around the fundamental resonance point, presenting a kinder load to the amp. This is all supposed to give a tight well controlled bass with no boom in a floor standing speaker that can be positioned close to the rear wall. The principle was employed in the Dynaco A35, although this was a wide, larger than average stand mounter. The A35 was supposed to offer a better controlled bass than the best selling A25 (>600,000 units sold).
The 91db efficiency bass driver will run full range, with a natural falloff above 2khz or so. No doping is needed as it does this all on its own - as is the case with all Dynaco & Scandynas from the same era (1969-76). The tweeter (also 91db) will feed in from about 2khz with a single protection capacitor somewhere between 8.2uF and 12uF (to be determined by ear) with no resistor needed.
Both chambers to be steel lined as per Doc Mod recipe. All tuning to be done by ear. The original Dynacos and Scandynas were all tuned by ear including how much fibreglass to put in the aperiodic port (they settled on 12 grams) and the value of the tweeter protection cap.
This project should bring together thinking from nearly 50 years ago combined with current Don Mod thinking, reflecting experiment and empirical evidence from listening.
When done, I'll do a write-up with pictures over on Audio-Talk to help gain a wider audience. Progress is likely to be slowish, thanks to a recurrent chest infection and dodgy back.
I've been mulling the project over for at least a year or so and the result of my Doc Modded Omar standmounters has convinced me to go ahead. Prior to these, I'd run a pair of stand mount Scandyna A30 speakers for a couple of years
Essentially I've taken the drivers, a 10 inch SEAS bass/mid and dome tweeter from the Scandyna A30 cabinets and they will go into a sealed 33 litre (net) two chamber floorstander with the two sections split about 55/45 and the top larger section venting via an aperiodic port into the smaller lower section. At higher frequencies, the drivers 'see' just the top section. At the lowest frequencies the top chamber vents into the lower one, so the driver sees the larger box. The impedance of the main driver is lowered around the fundamental resonance point, presenting a kinder load to the amp. This is all supposed to give a tight well controlled bass with no boom in a floor standing speaker that can be positioned close to the rear wall. The principle was employed in the Dynaco A35, although this was a wide, larger than average stand mounter. The A35 was supposed to offer a better controlled bass than the best selling A25 (>600,000 units sold).
The 91db efficiency bass driver will run full range, with a natural falloff above 2khz or so. No doping is needed as it does this all on its own - as is the case with all Dynaco & Scandynas from the same era (1969-76). The tweeter (also 91db) will feed in from about 2khz with a single protection capacitor somewhere between 8.2uF and 12uF (to be determined by ear) with no resistor needed.
Both chambers to be steel lined as per Doc Mod recipe. All tuning to be done by ear. The original Dynacos and Scandynas were all tuned by ear including how much fibreglass to put in the aperiodic port (they settled on 12 grams) and the value of the tweeter protection cap.
This project should bring together thinking from nearly 50 years ago combined with current Don Mod thinking, reflecting experiment and empirical evidence from listening.
When done, I'll do a write-up with pictures over on Audio-Talk to help gain a wider audience. Progress is likely to be slowish, thanks to a recurrent chest infection and dodgy back.