S45-2 project x 2

[Tanel]

So it started with getting a Beomaster 1900. Never owned B&O product before, just liked the look of it 🙂 Anyhow, then quite randomly came across a good looking pair of s45-2, picked them up the next day. No scratch on it, beautiful. Sounded kinda ok, tiny bit muffled I’d say.

Wires

Original wires it came with one of them was cut/fixed. That one sounded notably quieter. So I changed it to a new wire (mm²). Now that one sounded better and louder, notable difference again. Made new wires, with aftermarket connectors that felt flimsy to say the best.

Recapping

Opened it up everything looked in order. Changed electrolytic caps to new Jantzen Cross Caps. Opened up the sound quite a bit. Cross Caps are a fair bit larger but wasn’t too hard to fit them in there.

Changing the terminals

As I wasn’t happy with the connectors and using thicker wires I ended up changing to SpeakOn terminals. Old terminals come off just by pushing them inwards. Added a little epoxy to the inside groove as the MDF around there was little crumbly. Added epoxy the the back of the SpeakOn terminals as two pole sockets have two empty blade holes. So it was nicely air tight now. SpeakOn fits in there just perfectly with no cab modifications needed. Some hot glue around it on the inside and done.

Project 2

Now somehow I ended up picking up another amp, 1900-2. Faulty, with hum, missing one channel etc. But sounds good after full recap. So I needed one more set of speakers. Ended up winning an auction in Ebay for a good price. Another pristine looking pair, perfect, not a scratch on it. But the day comes it arrives to my door, oh my!
Fellow had packed two speakers loosely into a thin cardboard box with no padding at all. Aluminium corners had rubbed the cloth all broken on both, back corners dented of banging around. Coils broken loose inside. That wasn’t a good day. Fairly enough seller refunded it fully and let me keep the speakers.

So I thought why not mess around with them a bit more, try few things.

Rebuilding the inside

As some of the wires and resistors inside looked burned and melted I thought I change it all.

• Clued back the loose coils
• Put in the same Cross Caps as for the first pair
• Changed all the wires to Silver Plated OFC Copper PTFE Sheath 1.5mm²
• Changed all the resistors to Mundorf MR10 non-inductive metal film 10W

Was a tight fit on the board but worked out fine. Added SpeakOn connectors.

Playing around with bitumen damping

Now I had red from somewhere that damping the cabinet could help tightening up the sound a bit. Gave it a go. Put 2.7mm mat on all 4 walls of the speaker. Sides, top and bottom. Closed it all up, sounded good. Now comparing to the other pair, it sounded brighter and tighter but listening on quieter volumes the dynamic range of the bass wasn’t so good. Being a long time bass player it was easy to note the sustain of el and double bass was cut short.

Went in there again, pulled off the damping from top and bottom but keeping the sidewalls. Now it sounded real nice, and that’s how I’m keeping it.

Comparing 1 to 2

Now the second pair sounds more clear and open bit tighter on bass too. First pair has somewhat muddier midrange to it – this old radio feeling if that relates. I surely prefer the sound of the second pair myself.

Will add couple of pics of the rebuild.

Anyhow it’s been real fun working on this kind of stuff. Was about 16yrs old last time holding the soldering iron. Been 30 years!

Cheers!

Attachments:

You must be logged in to view attached files.

[Author]

Posts