What material is the flange? What about metallic dust/shavings/shards being attracted to the magnet?

As I said 3 posts before - tape up the entire speaker before starting to grind.

yachadm:

As I said 3 posts before - tape up the entire speaker before starting to grind.

...my bad!

Anyhow, I was just thinking about all the options. I'm sure working the box is in fact less risky than digging into the speaker flange and making a lot of metal dust.

I may be able to find a pair of good original woofers if needed. Let me know.

Martin

Yes, Martin. Yes. If you can find them I will take them.

I will check in the dungeons and get back to you tomorrow.

Martin

Whoa! I know what I wrote earlier was probably a boring read, but an M8A woofer is totally NOT suited for an S45! It's aluminum cone will ring like a bell and the shallow transfer function of the S45 crossover will never filter that out. The mids will certainly be horribly colored if you use that driver.

Also, the driver's Fs is not the sole determining factor of bass extension. It's determined by several driver and enclosure parameters, which is why I brought out that only a quality modeling program (like Unibox, which is great, and free), could be used to predict the low end response of a different driver in the S45 enclosure. Unless you want to sit and do the math and derivations, but why take forever doing that when Unibox is a free download? Let the computer do it!

If you're dead set on trying a modern driver, then download Unibox, learn how to use it and how changing Theile/Small parameters affect a driver, plug in the T/S parameters for the driver under scrutiny, make sure the OEM S45 crossover network will work with the modern driver's electrical parameters, see if you can live with what comes up, and pay attention to how smooth the provided response graphs are for that driver (response still won't look like exactly like that, because different enclosures cause different diffraction artifacts that affect the response, but the smoother it is to start with, the better. Baffle diffractions usually even out quite a bit in the power response as well).

It sounds like you're more a novice at loudspeaker design, so if I were you, I would just re-cone my drivers, or buy some from Martin first, if he has them. I've built quite a number of speakers, and while there's alot of guys out there who know vast multitudes (!!!) more than I do, I know enough to make decently educated design decisions. You'll waste alot of money if you just pick a driver that looks good and stick it in. Even when choosing a modern driver, you should abide by certain criteria if you hope to make a good choice.

There's alot involved in making a good choice, and while I don't necessarily completely agree with Martin that B&O already did everything to their fullest potential with a given product (not trying to argue Martin, just my opinion!), they've done their homework alot more than you or I or likely anyone else on this forum has.

I believe the gentleman who designed Unibox actually works for B&O now (Kristian Ougaard), coincidentally enough.

Anyway, I just want you to make an educated decision.

Jon

I don't disagree with you, Jon.
I believe B&O did the best they could with what was available, the
knowledge they had and what could be custom produced at the time.
B&O COULD produce better speakers back then - and they did, but they were
larger and had more drivers and often a more complex filtering.

You can probably buy better drivers today and probably build better
speakers or filters from scratch but it's not given that it will sound as
good within the already designed cabinet and I must admit to still
admiring the sound from the S45/S45-2 speakers, especially with respect
to their size.
They were build 35 years ago and they will still put many modern speakers
in the attic.

I have two original woofers. Tested and ready to mount.
A capacitor kit is also available.

Martin

Well, I'm glad we got you up into the attic, Martin.

I'm glad you got down out of there - I know that browsing the treasures up there can be very time-consuming.

Seriously though, the original woofers are the best replacement - I haven't heard better.

Dillen:

I don't disagree with you, Jon.
I believe B&O did the best they could with what was available, the
knowledge they had and what could be custom produced at the time.
B&O COULD produce better speakers back then - and they did, but they were
larger and had more drivers and often a more complex filtering.

You can probably buy better drivers today and probably build better
speakers or filters from scratch but it's not given that it will sound as
good within the already designed cabinet and I must admit to still
admiring the sound from the S45/S45-2 speakers, especially with respect
to their size.
They were build 35 years ago and they will still put many modern speakers
in the attic.

I have two original woofers. Tested and ready to mount.
A capacitor kit is also available.

Martin

The woofers from Martin are without doubt your best option. My pair of  s45-2s contain a capacitor kit and one replacement woofer supplied by Martin. They  are 30 years old and still sound superb.

Simon

Thanks to everyone here, I have learned some things about the factors that go into designing a good pair of speakers. No doubt sticking to the original woofers designed for these boxes is the best option.

Martin, the capacitors in my boxes have already been replaced, just waiting for your woofers. Let me know how you want to proceed, how I can pay you. Shipping will be to Belgium.

petegutierrez@live.com

You have an email.

Martin

Edit: No, you haven't. I got it back with a note telling that the mailbox is unavailable.
You have a PM instead, check your inbox.

Martin