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Thread: IMF TLS Transmission Line Loudspeakers

  1. #1
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 18,103
    I'm Martin.

    Default IMF TLS Transmission Line Loudspeakers

    I've been living with these speakers for a few days now and have put a fair few hours on them already. That has not been difficult since they have that rare quality of being very easy on the ear without sounding dull or rolled-off in any way.

    Here is a picture (which I pinched from Geoff's sale thread as it is better than anything I could take):



    For those unfamiliar with the transmission line, the idea is to take the rear wave from the driver and run it down an infinitely long line until it dissipates. For practical purposes an infinite line is impossible so the idea here is to attenuate higher frequencies from the rear wave progressively and output what is left, in phase, from the vents at the bottom of the front baffle, thus augmenting the bass response.

    Here is a link to a more detailed description of the speaker:

    http://www.imf-electronics.com/Home/.../studios/tls50

    You may also want to check out the IMF Transmission Line Babe Contest here: http://www.imf-electronics.com/Home/...e-babe-contest

    I could blab on about the sound of these speakers - and I will - but this quote from the user manual pretty much sums them up:

    The IMF 'TLS' are advanced versions of the transmission line reproducer which was developed some years ago to aid in laboratory research. They incorporate the latest and most refined drive systems enclosed in new and radically re-designed transmission lines. These speakers are for use with the best equipment. A 'TLS' is a sophisticated speaker; its virtues will not be apparent to the novitiate who will want something more obvious. lt will be most appreciated by the cognoscenti.

    The sound is polite and sophisticated but still draws you in. I did notice on some material that I thought some low level detail was a bit smothered - I suppose this is a price you pay for low efficiency, but it is not a serious enough issue to be a deal-breaker, and my reaction to this will be heightened having been using very high efficiency speakers for the last year and a half. Without the transmission line loading you would have a pair of very sophisticated 4 way bridge monitors. But all that cabinet under the driver array is there for a reason so let's move on to the transmission line bass.

    The first thing you notice is that it is not at all big or overblown. Matching speakers to a room, especially big speakers, is a fundamental basic in the quest to get a good sound. No amount of cable or box swapping will cure a bad speaker/room match. I can imagine these speakers close to a wall in a small room just sounding way too 'heavy' and 'leaden' - fortunately I am able to place them well out into space (about 8' from the rear wall) so no issues there. In fact I would say it is pretty much ideal for them.

    Play some rock music and you get a pleasing bit of weight to the bass, even with a dry recording, whilst thin recordings are fleshed out just a little. This isn't stunt bass from a port or an artificially accentuated mid-bass, though, it is just a low end 'presence' that does not really appear to come from the speakers themselves. There is just no effort to it. I am reminded of the big JBLs I heard recently at the Cranage Hall show. Don't get me wrong these are not as good as that but they have that same effortless quality in the bass that only a big speaker tuned to go properly low can do. Plus I am not getting any room boom problems like they had at Cranage

    Indeed nothing I could play set them off in the bass like that. Stick on a bouncy rock/pop record like The Pretenders 'Don't get me wrong' and the bass line romps along, no lag or unevenness at all. Put on something with serious LF content such as Black Grape's 'It's Great When Your Straight' and be amazed - at the end of this album there is a sub sonic bass pulse, a bit like the heartbeat on DSOTM. The only speakers I have owned that could have a stab at reproducing this was the Celestion A2, which made it a bit of a drone rather than a pulse. But these IMFs absolutely nail it - it energises the room. Very impressive indeed.

    However it was on this same album that I caught the speaker's Achilles heel. At the end of one track there is a deep synth bass line with a bass guitar above it playing a repeated, descending riff which is quite vital to the rhythmic cohesiveness of the track. This was buried in the synth bass line when it should be audible above it. Indeed knowing this track well I was listening for it subconsciously and then noticed that my mind was filling it in as it was barely audible. Only on the fade did it emerge.

    So not perfect, then but hey! what speaker is? Comments and contributions welcome, especially from other IMF/TDL owners or former owners, I would be interested in your experiences.
    Last edited by Macca; 27-09-2015 at 11:00.
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / NVA A30 Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  2. #2
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 29,346
    I'm Geoff.

    Default

    Have you played around with cables at all Martin. Including interconnects. What suited the Akais may not be the same for the IMFs. I find cable choices are definitely influential on the overall balance and this is very noticeable with a change of speakers.
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  3. #3
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 18,103
    I'm Martin.

    Default

    I try to avoid playing with cables if I can help it. The interconnects are NVA and I have found from extensive (and I mean extensive) trials that it is best to use the NVA interconnects with the NVA passive pre.

    Speaker cable is a different matter. I'm using Chord Odyssey 2 at the moment, what might be a better option?
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / NVA A30 Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  4. #4
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 29,346
    I'm Geoff.

    Default

    Quote Originally Posted by Macca View Post
    I try to avoid playing with cables if I can help it. The interconnects are NVA and I have found from extensive (and I mean extensive) trials that it is best to use the NVA interconnects with the NVA passive pre.

    Speaker cable is a different matter. I'm using Chord Odyssey 2 at the moment, what might be a better option?
    I take your point regarding the NVA cable with NVA amplification. But source to pre is always worth trying options with. My preference here being pure copper avoiding silver plated stuff, which can add a 'sheen' or even a coarseness. Not always the case though.

    As for speaker cables, there's no limit to the varying balances they offer in their effect on the sound. They do vary a lot. Try and borrow some for comparisons. I can't comment on the Chord, as I've not tried that (even though I've used an awful lot of different cables).

    I've got a spare 2.5m pair of QED Genesis Sliver Spiral knocking about that you can have if you want something to experiment with. They have odd plugs on one end that makes no difference to the sound that I can hear. They're very lucid cables. I've got about ten pairs of different speaker cables and won't be using these in the current setup. I got them from Rob (puffin).
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  5. #5
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 18,103
    I'm Martin.

    Default

    Thanks for the offer but I would need 4 metres a side, ideally a bit more.

    In any case I am pretty satisfied with the sound as it is. Next change will be to try the new Firebottle amp once Alan has knocked it up.
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / NVA A30 Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  6. #6
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 3,755
    I'm Alan.

    Default

    ...'knocked it up'... you cheeky beggar

    Love and commitment go into my builds I'll have you know

    Firebottle - for the no bottleneck approach.

    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  7. #7
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 29,346
    I'm Geoff.

    Default

    Yes indeed. That should have been 'banged together'!
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  8. #8
    Join Date: Mar 2014

    Location: KY - Scotland

    Posts: 2,487
    I'm Mike.

    Default

    Bit of thread resurrection here, but would they be any good in a room approx 14.5ft x 13.5ft, suspended wooden floors with heavy wood laminate and a rug up top.

    Speakers would be firing down the length of the room with rear wall behind being brick and thermal block inner.

    I know my wife will absolutely hate them but it's a reasonably cheap experiment IF they are ok in the room of course.

    😀

  9. #9
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 18,103
    I'm Martin.

    Default

    I think that might be a bit too small a space, Mike. The bass energy has to be heard to be believed. You'd be okay until you played something that set off a low bass node then you'd realise it was a mistake. My room is big, more than twice yours, and open plan to upstairs but they can still energise the whole space in a serious way. I suppose if you keep the levels down you might get away with it. I like it blasting out.
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / NVA A30 Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  10. #10
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 37,667
    I'm Grant.

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    Inclined to agree with Martin. These things can go seriously deep, and sound awful in wrong area
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
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