Hi-Fi History: The IMF Reference Standard Professional Monitor

Hi-Fi History: The IMF Reference Standard Professional Monitor | The Transmission Line Speaker

Рет қаралды 38,503

Жыл бұрын

In this episode of Hi-Fi History, Tom Martin talks about the IMF Reference Standard Professional Monitor, its history, and why transmission line speakers, if they're so effective, are no longer in vogue.
The seminal 1965 work that I mention and which appears to have triggered John Wright and IMF to pursue transmission line speakers was written by Arthur R. Bailey in Wireless World magazine:
diyaudioprojects.com/Technical...
Bailey for this paper, and subsequently in 1972, did some nice reasoning and empirical measurements to help guide the design of TL speakers. Very importantly, he realized that the wool fiber in the line could slow the rear wave and hence allow shorter lines - a significant element in practical designs.
When I mention in the video that the mathematics of TL designs was not fully characterized, I have this in mind:
en.wikipedia.org/wiki/Thiele/...
Many people contributed to the “full” models of ported and closed-box speakers, but the work culminated in a series of papers in the early 1970s by Richard H. Small extending the work of A.N. Thiele. These parameters have henceforth been called the Thiel-Small parameters.
My main point, as you may intuit, is that it is one thing to have some mathematics applied to a speaker concept and quite another to have a full parameterization of a design concept. Bradbury, for example, attempted the former in the late 1970’s for transmission line loading and he described the results as “unsatisfactory”.
As far as I can tell, a Thiel-Small type characterization of the transmission line speaker was not published until the 1999 work of George L. Augsperger of JBL. Around this time, others were involved in this “project” including Locanthi, Dickason, and King. A very nice summary is here:
transmissionlinespeakers.com/...
This kind of mathematical work is challenging, and I intuit that the IMF and related products were so good that they spurred slow but continued work in this area.
About Tom Martin:
Tom is a long-time audiophile. He began his reviewing career after acquiring the The Absolute Sound magazine in 1997 and then hi-fi+ magazine in 2002. He has worked closely with Harry Pearson and Robert Harley at TAS and with Roy Gregory and Alan Sircom at hi-fi+. Since Tom and his teams expanded the TAS and Plus platforms in the digital domain, he has served as Chief Content Officer.
For more product information visit:
www.theabsolutesound.com/arti...
What Is The Absolute Sound?
The Absolute Sound magazine has been a leading publication in high-end audio since 1972. Since the early 2000s, The Absolute Sound has expanded to include web, newsletter, digital magazine, social media, KZfaq and Substack platforms. The Absolute Sound platforms have a global audience of over 500,000 audiophiles.
For more show reports, expert reviews, features, and commentary subscribe to our newsletter at: www.theabsolutesound.com/news...
Follow us on Facebook: / theabsolutesound
#hifi #audiophile #theabsolutesound

Пікірлер: 182

@MrDishdonkey Жыл бұрын

I had a pair of IMF ALS40 speakers in the 90's. I was given them by a widow when I did some work for her. They were amazing. The bass was just biblical but in a controlled deep way. It was like waves coming over you. When I left home I left them at my mums for future renovation. Mu brother in law gave them away. I've never forgiven him.

@peteleoni9665

Imf speakers are great. But if you dont want to go to sleep between his words and sentences play this at 1.5 speed.

@lewgoogle5530 Жыл бұрын

I purchased a pair of IMF Studio speakers from Lyric Hi-Fi in Manhattan, in 1971. I was and remain an avid fan of TL woofers. Shortly thereafter, I built a pair of speakers to mimic the IMF Monitor, which was my heart's desire but which I could not afford. The dimensions of my speaker were nearly exactly the same as those of the Monitor. (All the details are supplied in an article published in the 50s or 60s in a journal called "Wireless World". Author is Bailey. I do also recognize that Arthur Radford was an early developer. As in the Monitor, I used KEF B139 woofers and the same KEF midrange driver as used in the Monitor (B10, I think). For tweeters, I used four RTR ESL panels per side, the same panels used by Infinity in the Servo-Statik One. The results were great and crushed all local competition. However, I later became an ESL fan, and I sold my home made Monitors in favor of KLH Model 9 ESLs; I used two pair, full range. Twenty years (and several more ESLs) or more later, I re-acquired my home built KEF-based speakers, and I cut away the part of the cabinet that housed the midrange and tweeters. I now use the TL bass cabinets to supply bass below 80Hz for my Beveridge 2SW speakers (another vintage stroke of genius). The lower you place the low pass filter, the less stuffing you need in the TL cabinet. The Brits originally used "long hair wool" and the current recommendation is a synthetic fiber called "polyfil". Easy to find. There are on line guidelines for how much fiber you need (in terms of weight) and where it needs to go (in terms of where in the transmission line), depending upon the desired bandwidth. Since I am rolling off at 80Hz with a steep slope, very little filler is needed. The TL woofer blends wonderfully with the Beveridge speakers, and incidentally the KEF B139 is one of the great woofers of all time in terms of its capacity to deliver detail in the bass frequencies.

@stack3r Жыл бұрын

Nothing. New designs are now around thanks to community research using srivers with strong motors TL is now the gold standard and manufacturers are being left behind by home DIY pa builders.

@user-pp6jd6qj4x

The designer of the transmission line speaker was Arthur Bailey, and it is in the public domain. Whom ever John Wright was, you owe him nothing. It was publicized in Wireless World in the late or mid sixties.

@glenncurry3041 Жыл бұрын

Did you know that Marantz sponsored that record? As a Marantz rep I had a box of them to give to my retailers for demo. It is a gate fold with a gold label seal with Marantz name on it and a letter inside from Marantz to their dealers. I still have my copy.

@socksumi Жыл бұрын

Arthur Radford should be getting the credit for the transmission line as he worked with Bailey but was more the tech genius behind the TL design. He was also the first to bring the TL design into a commercial product. Radford had said many times he was disappointed people didn't recognize his contribution to the loudspeaker art (especially the TL design) as much as his amps and electronics. He said he was more proud of his speaker designs than his amplifiers.

@keithmoriyama5421

I have a pair of dual transmission line Castle Winchester speakers-- $4,200 USD (1990) absolute immaculate condition. Found them across the street by a little old lady who wanted to get rid of them. I didn't know what they were, just that they were gorgeous. Bought them for $400. probably $20k in today's money. Sometimes you just get lucky... now I almost always buy used and look for "the deal"

@beautifulgirl219 Жыл бұрын

Had a pair of IMFs in the first "aspirational" stereo system I owned in the late 1970s. Put on "The Jungle Line" from Hissing of Summer Lawns, there is a four beats of low base part that repeats, it was one of the things that system did that showed what it could do, though I much more enjoyed listening to "Harry's House"; those speakers sang. Funny thing about those speakers, they were also beautiful listening to Voodoo Chile, or anything from Electric Ladyland, for that matter. Or "Please Be With Me" from Duane Allman an Anthology. The most beautiful sound I could find back then. Crown DC300A amp (200W/ch), Radford ZD22 Preamp was pristine clean. Shure V15 Type 3 cartridge. Great times! :)

@charlesnr Жыл бұрын

I remember the small IMF speaker. Unique signature of them was the use of the KEF B139 speaker. Looking online, the speaker has been revived by Falcon in the UK. So popular to be revived so many years later , since KEF had quit manufacturing. Worthy of a history for this woofer model.

@FOH3663

Their black and white exploded/cutaway ads are a thing of legend!

@lefterisefremidis1121 Жыл бұрын

Very nice review! I have a pair of RSPM Mk IV Improved with the Elac Woofer, kef mid and celestion s tweeter and supertweeter that my late father bought in 1981.

@remcogons9101 Жыл бұрын

In the Netherlands there was a man called Hans Baan, who made transmissionline speakers based on the IMF tls 50 and 80. The brand was called HB and the models were named HB1 and HB10. I owned a pair of HB1's. They were produced from around 1977 to 1980. Great speakers and I regret selling my HB1's in 1988.

@neilw4569 Жыл бұрын

My parents bought IMF super compacts in about 1980 always loved them. I eventually found a pair of TLS80 mk1 a number of years ago.they had played classical music all their life.I like a lot of electronic music bass heavy,which these do amazingly well!

@jdh3828 Жыл бұрын

It's still very very good today - I have a refreshed (crossover and NOS drivers) pair of RSPM Mk IV and they are phenomenal!

@garth56 Жыл бұрын

I had a pair of TDL's and not only was the bass jaw dropping but so was the imaging which was stunning!!!

@airtow6766

That's funny that you choose Focal as an example of picking off the shelf driver, because Focal made a woofer that was marketed and recommended as appropriate for transmission lines. It was an 8" clear polypropylene woofer with a stamped basket and large motor from probably the early to mid 1980's. I built a very large TL based on an article in Speaker Builder magazine. I think the woofers model number was 8P501.

@marksulloway5669 Жыл бұрын

A nice walk down memory lane. I still have my well worn Missing Linc album.

@johnarango7500 Жыл бұрын

A footnote: After Fried broke up with the English group, he continued to sell the drivers and crossover for a transmission line. The line was in its own cabinet (the first subwoofer?) with a separate line for each channel. It was relatively easy to build (using Fried's plans) because the line had only one turn. The mids and tweeters were in small "bookshelf" cabinets. The crossover was an enormous and very heavy steel box. Fried recommended placing the sub in the mid of the space for speakers with the smaller boxes on stands on either side or hung from the wall. I had this setup for several years. My only complaint was that it produced too much bass.

@Ultrafrozen Жыл бұрын

My uncle built "labyrinth" speakers back in the late 70's when I was a kid. I still remember his impressive reel to reel deck, probably where I got the audio system bug.