IMF brand of speakers

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#2
IMF stands for Irving M. (Bud) Fried, a long-time advocate of transmission-line speakers. I believe that all of his speakers except for the smallest, bookshelf types, were of transmission -ine construction.

If you ever had the opportunity to sit through a demo with Bud, you'd know that he believes that his speakers are the very best in the world.😉 - Pat
 
#4
I ran a pair of TLS50s for a couple of years.
The bass was truly impressive - tighter than most reviewers would have you believe, and extended right down to 'feel' frequencies. Acoustic bass was particularly startling in its realism.
However, the imaging seemed almost non-existant (four drivers), and the midrange was distinctly woolly. Changing the crossover caps for decent polys helped a bit.
These days, I'd happily have another pair, but mod them into 3-way units with decent MF drivers.
 
#5
iv got a pair of TLS80's these are totaly amazing they dont sound as good as the new roksan fr5 speakers. the tls80's just sound so real, i dont find the midrange too badly coloured and the top end is fairly good - more natural sounding rather than the best sounding.

iv got a pair of ALS40s which are also very good but the bass responce is poorer and the top could do with a little more definition but still a very good pair of speakers.

TLS80's £400 - £600 dependant on colour / age / stlye and condition

ALS40's cost me £65 with roten mid range drivers

later versions of the prof monitor are the best, i saw a pair in rosewood go for £1000
 
#7
Hello, my first post here... I have just got hold of some Super Compact MK1's. They are in good condition but unfortunatly have a couple of problems..

1] The original Elac 4/200 mids have been replaced with something else [look like generic cheap ones]

2] Despite the IMF reputation, there appears to little or no bass at all, I have detected a small amount of movement in the bass cones [KEF B200 1014?] but as I say, little or no actual bass.

I would be grateful if anyone here can point me in the direction of some replacement midrange drivers [Elac 4/200 would be good, though they are impossible to find] and also the cause of the bass suckout - is it possible the B200's have blown? or could it be more to with the crossover?

Any help very much appreciated!

aquapiranha
SP_A0027.jpg
 
#8
IMF speakers

I had a pair of those, I still have the woofer ( reconed ) given what i have learned and what information is avaliable, it sounds like the problem i had.
My little sister turned the amp ALL THE WAY UP, and fried the mid, also damaged the cross-over.
Are you willing to pull the apart and check everything?
My initial reaction was to repair but now I would not bother, i'd build a new set using the same basic size box and some good new drivers.
Have you tried any of the 4inch square frames in the Madisound range?
 
#9
Thanks

Hi, and thanks for the reply. Since the previous owner replaced the mids I was inclined to get some better ones, but the original elacs are almost impossible to find now. I did think that maybe there was some damage to the crossover given the lack of bass - not normally a trait of IMF. I have no problem opening up the box to check everything and may have a look at the weekend. Steve
 
#10
From memory the original crossover is glued to the foam that covers the top of the shelf/brace and uses thin gauge laminate inductors. i was of the opinion that there was room for improvement. BUT I am no-way an expert.
I do like the sound of the B-200 in a sealed box, but why not try a really good mid driver ( Vifa P13-00-08 while they are still avaliable ) use the front panel as a template and build a new box to accoodate a slightly different driver placement
 
#16
newbie123 said:
Has anyone on the forum,used these speakers? Throw some light on these speakers ... How are they different than today's speakers?
Click to expand...

I've been using a pair of IMF TLS50 MkII 4-way speakers since about 1977. When I first purchased them, I auditioned them against the Spendor BC1 loudspeakers of the day. Although the BC1's sounded excellent, particularly when reproducing vocals, I opted for the TLS50. The bass response of the TLS50 went much deeper, –3dB at around 33 Hz, versus 45 Hz or so for the BC1, and this was very noticeable.

I've enjoyed that extra bass extension a lot, with all my records and CDs, and now DVDs and Blu-Ray discs. I now consider that for true high-fidelity sound reproduction a –3 dB point of 20 Hz for the low frequencies is required. Nowadays, a two-way midsize bookshelf speaker partnered with a powered and carefully equalised subwoofer driver can probably offer a similar sound quality while not being quite as "large" as the 80 litre or so enclosures of each TLS50, while getting closer to the goal of a –3dB point 20 Hz.

I've recently noticed that the foam surround on one of the 4" midrange units has torn. It's not a happy thought to think that my speakers are now damaged in this way. The foam surround will need replacing, and hopefully the sound quality will improve a bit.

I've been auditioning a few speakers of late, but I usually come away thinking that I'd be downgrading from my TLS50s, at least within my budget. The closest I've come to a good overall sound is from the small 2-way PMC TB2i loudspeakers. These produced some reasonable bass response, while still having a smooth, listenable sound quality that revealed a lot of the content in a recording. As it happens, PMC claims that some of their models use transmission line low-frequency alignments, like the IMF's of old. However, I'm not sure whether what they achieve in their TB2i is a true transmission line, as there doesn't seem to be the same degree of line damping material present. It seems that the TB2i's may have something more akin to a heavily damped port in a vented-box design.

Still, to my ears (and likes/dislikes) at least, the TB2i's are a nice sounding speaker that I could live with, if they were partnered with a suitable subwoofer. They'd certainly be more efficient (have a higher sensitivity) than do the TLS50's, which are very inefficient (that's the price one has to pay for more bass out of only a moderately large enclosure, without any special frequency-response shaping).

If anyone has a pair of the IMF TLS80 speakers, then I think that they're very fortunate. The extra bass response on tap compared to the TLS50 would make them a formidable speaker and hard for many new loudspeaker systems to beat.

On the TLS50's, it would be interesting to block off the port on the transmission line, turning the speaker into a sealed enclosure system. To this modified system it would then be possible to add a subwoofer, relieving the the 8-inch woofer in the TLS50 from some largish cone excursions when it now tries to reproduce frequencies below 30 Hz.
 
#19
The Jordan's IMO, are way overpriced.

Depending on budget, I'd put Fostex FF85, FE103, FE108eS, Mark Audio CHR70, Alpair6P/6M, Alpair7, CSS EL70 on my short list. There is also a ScanSpeak 3" that gets good reviews (but is priced similar to Alpair7), and for looow budget Fountek FR88ex. Quite a few others playing in that niche, but it is hard for one person to evaluate them all.

dave
 
#20
Hi Dave,

Thanks for those driver details. It seems that there are quite a few full-range drivers out there. I'm now much better informed than I was earlier today. 🙂

The Jordan's seem to have a very smooth frequency response, at least from what I've seen published by the manufacturer.

Not having heard any of these, it's difficult to make a choice. It's a bit of a pity that the Jordan's are so expensive, as it could be an expensive experiment to try them out.
 
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