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jeffrey88 7th May 2012 06:48 PM

IMF TLS 50 II driver replacements

I acquired a fantastic pair of IMF TLS 50 II's recently and unfortunately some of the drivers have been replaced. They still have the original Audax 12X8 D25 tweeters and Kef B200 woofers, but the one midrange and the supertweeters are different. I'm looking for some input on what I can do about the midrange drivers because I am quite happy with the supertweeters. Unfortunately though the midrange was replaced with something that sort of was just slapped in and this needs to be remedied. It looks like the other midrange is still original.

If someone might be able to tell me what midrange the original driver is that would help.

Here are some pictures:

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Honestly, I'm not sure which one is the original and which one is the replacement!

Thank you for any and all help.

planet10 7th May 2012 08:27 PM


Your pictures are linked to inside your gmail accout so we can't see them. If you could attach them to the forum (Go Advanced, Manage Attachments button)

The mids on there are Peerless K4040 (? not sure if the numbr without looking it up) in the cans, your pic will remind me of the superTweeter (Coles 4001?)

I've always wanted to get another set of TLS50s or 80s and do a rather "radical" upgrade. Replace the mid, tweeter & super-tweeter with a nice 3" full-range. On TLS80s, you could use the existing 4" cardboard cyclinder as an enclosure, on the TLS50 you'd need to fit one.

One would need to explore the possibilities wrt sensitivity and XO details, but the FF85wk would be at the top of the list.

One would need to redo the XO, either active or passive. The XO point between the B200 & the FR best choosen in relation to the box width / baffle step frequency (suggests 250-300 Hz).


jeffrey88 7th May 2012 08:41 PM

Hey Dave,

Thanks for your response. I've updated the pictures so you can see them properly now.

As far as the XO's go they have already been upgraded as this was done when the supertweets were changed out. Unless of course there is more than one crossover in here!

planet10 7th May 2012 08:43 PM

1 Attachment(s)
snatched from elsewhere


planet10 7th May 2012 08:49 PM

Both mids are replacement drivers (one looks to be a mid-bass out of an RS Minimus 7). Can you check to see if they are loaded into a cardboard tube?

The supertweeters are a variation on the theme of the Audax small inexpensive tweeter. Some of the Audax ones were quite good....

You can still buy new Coles 4001


jeffrey88 7th May 2012 08:55 PM

I'm not currently at home with the speakers but I can certainly do that.

Thank you for your help Dave I really appreciate it!

jeffrey88 7th May 2012 08:58 PM

With regards to the supertweeters, I'm not so sure if I do want to replace those. I don't know a whole lot about replacing components in speakers, although I am experienced with Car Audio.

Anyhow, what I'm worried about is the crossover. I'm no electrical guy and unfortunately I think modifying the crossover is a bit out to lunch for me for now, unless I must absolutely do it for the mid-ranges and then in that case would be a worthwhile venture for the tweets possibly.

What's your thought on that? I do like the supertweets in there right now so I'm not sure if it would be worth it to change them out.

KASUMI 7th May 2012 09:11 PM

email Jerry at Falcon Acoustics he knows everything there is to know about IMF helped me with some TLS80's
Falcon Acoustics | The Leading DIY Speaker Parts and Kit Supplier since 1972

jeffrey88 7th May 2012 09:12 PM

Thank you so much for that Kasumi. That is very helpful.

planet10 7th May 2012 09:36 PM

1 Attachment(s)
A significant part of Jerry's business is keeping a lot of these vintage projects viable.

Here is the original TLS50 XO


PS: i find the top on the aforementioned FF85 better than any of the little "audax" i have tried (many)

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