Macca
27-09-2015, 10:27
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):
http://i903.photobucket.com/albums/ac233/Macca_photos_2009/TLS50_2.jpg (http://s903.photobucket.com/user/Macca_photos_2009/media/TLS50_2.jpg.html)
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/imf/speaker-range/studios/tls50
You may also want to check out the IMF Transmission Line Babe Contest here: http://www.imf-electronics.com/Home/imf-transmission-line-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.
Here is a picture (which I pinched from Geoff's sale thread as it is better than anything I could take):
http://i903.photobucket.com/albums/ac233/Macca_photos_2009/TLS50_2.jpg (http://s903.photobucket.com/user/Macca_photos_2009/media/TLS50_2.jpg.html)
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/imf/speaker-range/studios/tls50
You may also want to check out the IMF Transmission Line Babe Contest here: http://www.imf-electronics.com/Home/imf-transmission-line-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.