Build Replica IMF Transmission Line Speakers???

diyAudio Member
Joined 2007
Which IMF's??
I have some plans on disk courtesy of another member but do you have the KEF drivers ??
I have to assume you mean the big Tranmission line monitors.
I was contemplating similar plans but gave them up, sold the B-139s on Ebay.
If you want the pagesI'll see if I can drag them up from the basement of the HD
regards
Ted
 
frugal-phile™
Joined 2001
Paid Member
There are actually 2 versions of the Rogers Pro9 TL... the 1st a 4-way published in HiFi Answers (which i have a pdf of) and an "improved" 3-way done for Falcon Electronics.

Neither is reallybig enuff to get the most out of the driver.

dave
 

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frugal-phile™
Joined 2001
Paid Member
Here is my reply to the IMF list....

Ian,

>Has anyone here attempted to build a pair of Replica IMFs?
>>I would like to build the boxes & use currently available drivers.
>>Does anyone have Plans?

Here is your starting point... the Classic TL Revisted. <http://www.t-linespeakers.org/projects/vProjects.html>

It is very much aimed directly at the Radford/IMF mold. Uses the Seas 25F-EW* if you aren't just bunging the World Design 2-way Kit into it (i wouldn't)

<http://wduk.worldomain.net/acatalog/wd25ahfw1a.html>
<http://wduk.worldomain.net/forum/showthread.php?p=37643#post37643>

*(looks like the have gone & discontinued that one now... my guess at replacement is the CA25RE5 <http://www.seas.no/images/stories/vintage/pdfdataheet/h0250_ca25re4.pdf>, but there are 3 candidates, i'm checking with Scott to see which one best fits)

Personally I'd treat the woofer, and then -- depending on budget -- use a modified Fostex FE127e or FX120 (or if you have a BIG budget, F120A) as mid or mid-tweeter, and maybe a tweeter on top of that. And i'd biamp to reduce the XO complexity.

You can of course use whatever you want on the top, but given that tweeters these days are much better than the ones available in the day, a 2-way on top (as opposed to the 3-way used in most IMFs) would be the way to go. The easy way to do it would be to go looking for an already well sorted mini-monitor project, and put that on the top -- with the woofer underneath you'd want to pick one that by itself is bass deficient, but superb in the mid/top.

XOs i'd push down to 200-250 (nominal baffle step on these is going to be ~250 Hz) and use a mid that gets the HF XO up to at least 5k. Done right this should outperform any IMF currently still alive, but retain those things the IMF does so well.

If 1 10 isn't sufficient bottom (it was for IMF, but not some of the Radfords), you can double the cross-section of the line, and mount 2 woofers (i'd make the cabinet a bit wider to push the XO frequency down and mount the woofers on the side push-push).

dave
 
Bass unit on this one is the Seas A26RE4:http://seas.worldomain.net/pdf/H1411.pdf . As Dave mentions, I probably wouldn't try going 2 way with them -I'd either use a 3 way, if you can find a suitable midrange unit that actually does cover the midband (200Hz - 5KHz at least), or cross to a wide-range driver like one of the Fostex units. Oddly enough, I was discussing this with a chap who's built a pair & my suggestion at the time was an FF85K, crossed at 500Hz. Dave's 127 / FX120 / F120a with a lower XO point as they have better power-handling than the 3in FF85K would also be a good plan IMO. :)
 
Transmission Line

I am in the final stages of construction of a replica hi-fi answers transmission line circa early 70s.I have made a couple of variations to the original design.Instead of the KEF t27 tweeter i am using the celestion HF1300 but still use the B139,B127 and Coles STC4001G super tweeter.For a crossover i am using cambridge R50.Speaker box consists of 35MM MDF and long haired wool fibres, total weight per box about 60Kg.Also the front was divided into two sections comprising base/mid range and tweeter/super tweeter the reason for this was that if i decide to change any speaker i will not have to make a complete front again and have to go through all the cutting out and rebating process again.
 
transmission line

Hi Don
You may be correct in what you say but i am trying to emulate the original design as close as possible at the moment and then improve on it.It is my intention to replace the 8ohm hf1300 with 2 x 16ohm hf1300s in parallel.I have listened to this setup in the ditton 25s and they are superb for upper mid range speakers, i wll then turn my attention to the b110 for a further improvement.

Tony
 
frugal-phile™
Joined 2001
Paid Member
Re: transmission line

tonysherwin said:
It is my intention to replace the 8ohm hf1300 with 2 x 16ohm hf1300s in parallel.

Bad idea. The spacing of 2 is way too far apart at those frequencies to avoid combing. In the Ditton this causes a muddled HF (the HF1300s don't get anywhere near the midrange)

You'd be streets ahead to just replace the tweeters with a single modern tweeter -- even a modest modern tweeter can handily outperforn the tweeters of the day.

dave
 
is there still a plan for the RSPM or SACM cabinets floating around? i've looked and can't really find anything useful. i've got the spare drivers to do a 3-way speaker like this, and i was thinking of modeling it after the SACM form factor. i'd appreciate any help i can get here, thanks!
 
IMF question

This is an old thread but i am interested in building some thing more substantial than my Kef duettes. I have some scandyna a-25's and no partner so a very large transmision line like the one in planet-10's post sound like the go.
I have some questions: Am i to understand that i build the cabinets, use my seas woofer and a suitable mid range driver ( i have some fostex fe-103's??) and then mount an external tweeter, build cross over and bob's your uncle.
I am pretty savvy with electronics but a complete innocent with acoustics so any thoughts or suggestions would be very much appreciated
Michael
 
I have been searching for a good TL cabinet design for a 3-way active speaker system for a while and the Pro9 looks like a good candidate.

I have a pair of Mark Audio CHR70's and a pair of Fostex FE126En's laying around. I was thinking I might use either of them (preferably the MA's) for the mids.

My vision is to use the miniDIGI/DSP/AMP combo in 2.1 mode, but that means I am going to need some really efficient woofers since the miniAMP only delivers 20 watts.

Any thoughts on this concept? Any suggestions on bass drivers for the 3-way Pro9 cabinets?