Scandyna Rebuild Underway.

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Simon Hickie
Posts: 506
Joined: Mon Feb 27, 2017 1:47 pm
Location: East Staffordshire
Great Britain

Scandyna Rebuild Underway.

Unread post by Simon Hickie » 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.
“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.” George Bernard Shaw.

shanewhite
Posts: 24
Joined: Wed Apr 12, 2017 10:27 pm
Ireland

Re: Scandyna Rebuild Underway.

Unread post by shanewhite » Fri Apr 21, 2017 5:09 pm

Sounds like it'll be very similar to Peter Comeau's WD25T, although he used a laminate of chipboard and MDF rather than steel plate.

http://www.hi-fiworld.co.uk/loudspeaker ... -step.html
Heybrook TT2 (original steel chassis version)
Mission 774
Denon DL103
Vintage Partridge/BBC SUTs
EMO Systems E235 phono preamp
Squeezebox 3
WAD KEL84
A&R Arcam Alpha CD
Mission 782
Projects:
Vestax/Heybrook hybrid turntable
Bitsa unipivot with Acutex M320 III STR cartridge.
Re-housed WAD Phono 2 with Nick Gorham design shunt PSU.

Simon Hickie
Posts: 506
Joined: Mon Feb 27, 2017 1:47 pm
Location: East Staffordshire
Great Britain

Re: Scandyna Rebuild Underway.

Unread post by Simon Hickie » Fri Apr 21, 2017 6:55 pm

Yes indeed Shane. That was also part of the planning process. PC's project used the slightly larger drivers with an earlier roll-off and a crossover. However, I wanted to effectively go crossoverless and stuffingless. I'm still undecided whether to go for heavy fabric (Dynaco A35) or fibreglass for the aperiodic loading.
“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.” George Bernard Shaw.

shanewhite
Posts: 24
Joined: Wed Apr 12, 2017 10:27 pm
Ireland

Re: Scandyna Rebuild Underway.

Unread post by shanewhite » Fri Apr 21, 2017 11:55 pm

IIRC, Peter spent a long time looking for a specific type of reticulate foam for the WD speakers and had to buy huge quantity to get what he wanted. I wonder if he's got any left?
Heybrook TT2 (original steel chassis version)
Mission 774
Denon DL103
Vintage Partridge/BBC SUTs
EMO Systems E235 phono preamp
Squeezebox 3
WAD KEL84
A&R Arcam Alpha CD
Mission 782
Projects:
Vestax/Heybrook hybrid turntable
Bitsa unipivot with Acutex M320 III STR cartridge.
Re-housed WAD Phono 2 with Nick Gorham design shunt PSU.

Simon Hickie
Posts: 506
Joined: Mon Feb 27, 2017 1:47 pm
Location: East Staffordshire
Great Britain

Re: Scandyna Rebuild Underway.

Unread post by Simon Hickie » Sat Apr 22, 2017 9:58 am

Interesting Shane & thanks. I have some fibreglass salvaged from the old cabinets. I'll carefully weigh 12 grams worth and see what happens. I can't decide whether to steel line the bottom section: the original A35 didn't have any stuffing in this bit, so I might just go with bracing in the first instance. I'm making the back panel a removable two part job to ease with fettling. An unfortunate side effect is that it might end up looking a bit Harbeth like.....
“The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.” George Bernard Shaw.

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