jerrybloomfield
Member
Me too, but you'll know from your own experience what people as for sometimes...
IMF Professional Monitor IV
- Thread starter skyebridge
- Start date
skyebridge
Registered User
well, personal taste is what moves the world. but IMHO there are two things to take from what you are offering:
1. what you should be aiming to do with these fantastic speakers is preserve their capabilities - so, yes, replace, improve where there is scope - but the emphasis should be on preservation. for instance, are the cabinets well maintained? are the drive unit mountings stable and secure?
2. good speakers will only thrive with good amplifiers (and other quality sources). 'good' does not mean 'big' or 'powerful'. i am a consistent advocate of the marriage between naim pre/power amps and ruark loudspeakers (which i regard as generally far superior to those made by naim). as i recall, what big IMF speakers cried out for was not 'power' (though they need enough) but 'control' - the kind of fast flexibility naim power amps exhibit.
i am an admirer - not without some qualifications - of chord amps. i have also owned AMC, NAD, rotel, yamaha, crown, lexicon and carver amps as well as naim.
i've yet to find anything better than a bunch of naim nap-135's.
i would love to be able to put 6 x nap-135's onto a pair of IMF prof monitor-IV's
anybody done this?
has anybody out there ever done this?
1. what you should be aiming to do with these fantastic speakers is preserve their capabilities - so, yes, replace, improve where there is scope - but the emphasis should be on preservation. for instance, are the cabinets well maintained? are the drive unit mountings stable and secure?
2. good speakers will only thrive with good amplifiers (and other quality sources). 'good' does not mean 'big' or 'powerful'. i am a consistent advocate of the marriage between naim pre/power amps and ruark loudspeakers (which i regard as generally far superior to those made by naim). as i recall, what big IMF speakers cried out for was not 'power' (though they need enough) but 'control' - the kind of fast flexibility naim power amps exhibit.
i am an admirer - not without some qualifications - of chord amps. i have also owned AMC, NAD, rotel, yamaha, crown, lexicon and carver amps as well as naim.
i've yet to find anything better than a bunch of naim nap-135's.
i would love to be able to put 6 x nap-135's onto a pair of IMF prof monitor-IV's
anybody done this?
has anybody out there ever done this?
DSJR
Between us and them
I don't know of any active IMF's personally... The boxes are far too big for most homes today and as yet, IMF's don't have the cachet of equivalent Tannoys sadly, despite being a lot less "characterful."
Look, if you want to follow this route and you have some serious money burning holes in your pockets, buy some PMC MB1's used. if you can find some, they'll be around £3,000 I should think. They'll take over in single wired form where your IMF's leave off, will go louder with less distortion, can be tri-wired and there's a proper active path ahead of you too, should you wish to go that way (and they sound great with "just" a baby Bryston power amp too).
Look, if you want to follow this route and you have some serious money burning holes in your pockets, buy some PMC MB1's used. if you can find some, they'll be around £3,000 I should think. They'll take over in single wired form where your IMF's leave off, will go louder with less distortion, can be tri-wired and there's a proper active path ahead of you too, should you wish to go that way (and they sound great with "just" a baby Bryston power amp too).
Paulthefirst
Member
All responses re my possible IMF upgrade/revamp appreciated. For the record, I am not interested in secondhand value, only in possible improvement (& long term sustainability, given their age and decreasing availability of replacement drivers). Cabinets are sound.
Now, I rather imagined that the best of modern drivers have the potential to be better than designs of 40 years ago - that was a driving force towards thoughts of replacement. Is that not correct?
Maybe what I could do is buy the drivers, make a new baffle and fit to one of the IMFs, triamping with active XO so that I can tweak a bit to balance it. Compare one modified with one not. If not an improvement, then replace original, and design new TL cabinets around the bass driver (much bigger project), and aim afterwards to keep whichever of the two sounds best new or IMFs (=back to square one if latter!!). I suppose somewhere along the way I could try triamping the IMFs, with the supertweeter just passively connected through a capacitor (as it currently is across the HF1300), more for interest than anything as it doesn't solve the original 'problem'.
Any thoughts, though, on the best bass driver to try as a replacement for the B130 (e.g. Scanspeak 26W8861? ATC SB75-234LC? Volt 250-8?) What would you do if your B139s all died and no replacements were available?
Now, I rather imagined that the best of modern drivers have the potential to be better than designs of 40 years ago - that was a driving force towards thoughts of replacement. Is that not correct?
Maybe what I could do is buy the drivers, make a new baffle and fit to one of the IMFs, triamping with active XO so that I can tweak a bit to balance it. Compare one modified with one not. If not an improvement, then replace original, and design new TL cabinets around the bass driver (much bigger project), and aim afterwards to keep whichever of the two sounds best new or IMFs (=back to square one if latter!!). I suppose somewhere along the way I could try triamping the IMFs, with the supertweeter just passively connected through a capacitor (as it currently is across the HF1300), more for interest than anything as it doesn't solve the original 'problem'.
Any thoughts, though, on the best bass driver to try as a replacement for the B130 (e.g. Scanspeak 26W8861? ATC SB75-234LC? Volt 250-8?) What would you do if your B139s all died and no replacements were available?
jerrybloomfield
Member
Welcome to the world of Transmission Line Physics! I say that because the first thing to work out if you are thinking of going down the replacement unit road is to ensure that the IMF transmission line physical parameters match those of an optimum quarter wave line for the actual drive unit you have decided to use. If they don't ( and they probabaly won't) , quite seriously - don't do it, you'll mess up perfectly good cabinets. You cannot just stick a different unit into a TL and expect it to work properly, each cabinet is specific to the selected drive unit, and I think you run a large risk that what you're thinking to do probably won't work.
The IMF line that you've got is optimised for the B139 externally in terms of size and tapered internally in terms of being a 1/4 wave line, and unless you match up to the line characteristics including damping required very carefully and you're lucky with your choice of bass driver, you're probably wasting your time and money because you won't get the results you may be expecting. You could do much worse than start off on Dave Dlugos's excellent site which is:
http://www.t-linespeakers.org/
It will give you a good starting point and has really helpful links into the theoretical design papers that are around. Having selected your theoretical replacement unit and computer modelled it, you've then got the task of working out optimial response and the damping in the line that's needed. A word of warning - the computer models are great but are only a good indicator of what to expect, a successful TL speaker relies on post-build multiple choice experimentation aka "tweaking" as much as anything else to be successful. It's both fun and frustrating!
You've also got the difficult job of balancing the characteristics produced by the TL loading and what in your case your proposed active crossovers are going to do to alter that beneficially, if you decided to go down the active route.
This is why I don't advocate replacing drive units in IMF's except with original, IMHO and experience you end up messing up a perfectly good speaker. I also have never seen an active IMF probably for much the same reason. As you can tell, I agree with skyebridge on this!
My advice is that as far as getting replacement B139's is concerned, do what all us IMF owners do. Just buy some good units from a reputable source, and put them into store in a box in case they are needed. There were large numbers of B139's made, so the supply is still fairly good.
Then as a principle, if you want to start down the design route, I'd start from new. You've got a blank canvas to work from which is a huge advantage, and some of the modern designs I've heard are really really good. There are some great cabinet designs around to pick from.
The IMF line that you've got is optimised for the B139 externally in terms of size and tapered internally in terms of being a 1/4 wave line, and unless you match up to the line characteristics including damping required very carefully and you're lucky with your choice of bass driver, you're probably wasting your time and money because you won't get the results you may be expecting. You could do much worse than start off on Dave Dlugos's excellent site which is:
http://www.t-linespeakers.org/
It will give you a good starting point and has really helpful links into the theoretical design papers that are around. Having selected your theoretical replacement unit and computer modelled it, you've then got the task of working out optimial response and the damping in the line that's needed. A word of warning - the computer models are great but are only a good indicator of what to expect, a successful TL speaker relies on post-build multiple choice experimentation aka "tweaking" as much as anything else to be successful. It's both fun and frustrating!
You've also got the difficult job of balancing the characteristics produced by the TL loading and what in your case your proposed active crossovers are going to do to alter that beneficially, if you decided to go down the active route.
This is why I don't advocate replacing drive units in IMF's except with original, IMHO and experience you end up messing up a perfectly good speaker. I also have never seen an active IMF probably for much the same reason. As you can tell, I agree with skyebridge on this!
My advice is that as far as getting replacement B139's is concerned, do what all us IMF owners do. Just buy some good units from a reputable source, and put them into store in a box in case they are needed. There were large numbers of B139's made, so the supply is still fairly good.
Then as a principle, if you want to start down the design route, I'd start from new. You've got a blank canvas to work from which is a huge advantage, and some of the modern designs I've heard are really really good. There are some great cabinet designs around to pick from.
PigletsDad
My intelligence test came back negative.
If you want to play with tuning transmission line designs, a great resource is Martin King's site at http://www.quarter-wave.com/
He has developed modelling and design tools, which are available for download, at low prices. There is also a mass of detailed documentation; if you seriously intend to fiddle with a TL line, read the stuff on his site.
He has developed modelling and design tools, which are available for download, at low prices. There is also a mass of detailed documentation; if you seriously intend to fiddle with a TL line, read the stuff on his site.
Paulthefirst
Member
With thanks to all for their comments. I've given this much thought, and on the basis of advice from everyone who has contributed, and some modelling using Martin King's software, I'm not for now going to tamper with the IMFs, but instead try to duplicate the performance in a different shape enclosure, intending it to be more flexible in placement, and hopefully also more 'spouse friendly'.
I've decided on these drivers: Peerless XXLS830843 bass, ATC SM75-150 and Scanspeak D3004-66000.
The Peerless models almost identically to the B139 in the IMF profile, subject to appropriate damping. My challenge is to make another TL enclosere that will be the equal of the IMF. The Scanspeak I like because of its better off-axis response than the ring versions (and cheaper!), increasing the size of the 'sweet spot'.
The mid & tweeter I'll put in a separate enclosure on top, which could avoid the need for 'toeing in' of the main enclosures. Also allows some styling variations.
The setup will be tri-amped - through ebay I've picked up an Alesis ra150 and an Alesis ra300, to complement my existing Musical Fidelity P170, and invested in a new Behringer DCX2496. Once its all set up I can consider whether to go for mods to the DCX to improve it, or go for an analogue active XO having found the appropriate parameters.
Also through ebay while looking for the DCX I've picked up a Behringer DEQ2496, so I can play with room EQ. Part of me thinks this is a good idea, spurred on by the realisation (through Martin King's software) of just how much the room modifies the sound, while part the purist in me - fed by years of 'HiFi' hype' is concerned about the adverse effect of all that electronic compensation. I'll find out which suits me best - and can always sell the DEQ on ebay again if it doesn't help! I just long for the system to sound like my IMFs did when played out of doors!!
I'll let you know how it goes, probably a few months though befor I get it done.
If all that doesn't work I'll try using the new drivers in the IMF enclosure - which I can do non-destructively, replacing the original baffle and drivers if I wish.
I've decided on these drivers: Peerless XXLS830843 bass, ATC SM75-150 and Scanspeak D3004-66000.
The Peerless models almost identically to the B139 in the IMF profile, subject to appropriate damping. My challenge is to make another TL enclosere that will be the equal of the IMF. The Scanspeak I like because of its better off-axis response than the ring versions (and cheaper!), increasing the size of the 'sweet spot'.
The mid & tweeter I'll put in a separate enclosure on top, which could avoid the need for 'toeing in' of the main enclosures. Also allows some styling variations.
The setup will be tri-amped - through ebay I've picked up an Alesis ra150 and an Alesis ra300, to complement my existing Musical Fidelity P170, and invested in a new Behringer DCX2496. Once its all set up I can consider whether to go for mods to the DCX to improve it, or go for an analogue active XO having found the appropriate parameters.
Also through ebay while looking for the DCX I've picked up a Behringer DEQ2496, so I can play with room EQ. Part of me thinks this is a good idea, spurred on by the realisation (through Martin King's software) of just how much the room modifies the sound, while part the purist in me - fed by years of 'HiFi' hype' is concerned about the adverse effect of all that electronic compensation. I'll find out which suits me best - and can always sell the DEQ on ebay again if it doesn't help! I just long for the system to sound like my IMFs did when played out of doors!!
I'll let you know how it goes, probably a few months though befor I get it done.
If all that doesn't work I'll try using the new drivers in the IMF enclosure - which I can do non-destructively, replacing the original baffle and drivers if I wish.
DSJR
Between us and them
On the IMF site, there's a pic of a model I never saw in the flesh, with mid and top in a separate enclosure but hidden, I think, behind a large grille frame a la KEF 105 or early B&W800.
Good luck with your new build. Bare in mind that IMF on earlier models tended to under-damp the bass a little and then mask the subsquent cancellations at 100 - 200Hz by pulling the mid down in level (OK for CD but horrid with springy belt drive turntables of my acquaintance
). PMC seem to do the same on their smaller "domestic" models too - a matter of design choice I reckon.
Good luck with your new build. Bare in mind that IMF on earlier models tended to under-damp the bass a little and then mask the subsquent cancellations at 100 - 200Hz by pulling the mid down in level (OK for CD but horrid with springy belt drive turntables of my acquaintance
). PMC seem to do the same on their smaller "domestic" models too - a matter of design choice I reckon.jerrybloomfield
Member
It sounds like you're talking about the legendary IMF SACM, they're the Holy Grail for IMF enthusiasts. A fabulous speaker, I just sold my pair because they didn't work well in my room shape, but the soundtage and quality especially of the midrange was still something else. Got a pair of unmolested RSPM 1V's instead. There were only 3000 pairs of SACM's ever made, probably not more than 50 pairs left world-wide now.
The SACM midrange is in a wedge-shaped enclosure and sits on top of the bass enclosure, the tweeter and supertweeter sit on a metal mount above the midrange. I did a full renovation on mine, pictures etc. are on the IMF forum if anyone's interested.
The SACM midrange is in a wedge-shaped enclosure and sits on top of the bass enclosure, the tweeter and supertweeter sit on a metal mount above the midrange. I did a full renovation on mine, pictures etc. are on the IMF forum if anyone's interested.
Hi all,
First of all, thanks to Jerry, who told me about this forum, don't pay any attention to my grammatical errors, as English is not my native language.
I want to read and learn as much about IMF as i can.
For some 25 years ago, when i was just 23 i bought a brand new pair of IMF Professional monitors, sometimes named Mk4, with the 128/20 woofer.
I still own this pair and they are and play just like they where new.
Some 6 years ago, when i got my first PC starting to look for some IMF info,
resulting in buying a pair of CM3.
From this moment on life did went in higher IMF gear for me.
Just starting buying, selling to friends and family, who all wanted IMF's, just liking their soundstages, clear imaging en open sound.
For years i wanted to lay my hands on a pair of SACM's and finally i succeeded in buying a mint pair which have been standing back to the wall with no women, childeren of pets in the house from new.
They are the early version with SN#0201.
My set up now consists of a pair of SACM as main speakers, the Profs are my rear channel, and a TDL center in case i want to play a DVD in dolby.
No subwoofer needed, with those 4 big TL's in the house.
I also have stored 2 pairs of HPCM's, a pair of ALS40 Mk2a with the BR drivers, 2 pairs of Compacts and 3 pairs of Super Compacts Mk2.
Also when people started buying those plastic dolby sets, i started to buy all
the spares i could lay my hands on.
This was my introduction in this forum, hope te learn a lot about IMF and technical details about them.
Kind regards,
Johan Nanninga
Netherlands
First of all, thanks to Jerry, who told me about this forum, don't pay any attention to my grammatical errors, as English is not my native language.
I want to read and learn as much about IMF as i can.
For some 25 years ago, when i was just 23 i bought a brand new pair of IMF Professional monitors, sometimes named Mk4, with the 128/20 woofer.
I still own this pair and they are and play just like they where new.
Some 6 years ago, when i got my first PC starting to look for some IMF info,
resulting in buying a pair of CM3.
From this moment on life did went in higher IMF gear for me.
Just starting buying, selling to friends and family, who all wanted IMF's, just liking their soundstages, clear imaging en open sound.
For years i wanted to lay my hands on a pair of SACM's and finally i succeeded in buying a mint pair which have been standing back to the wall with no women, childeren of pets in the house from new.
They are the early version with SN#0201.
My set up now consists of a pair of SACM as main speakers, the Profs are my rear channel, and a TDL center in case i want to play a DVD in dolby.
No subwoofer needed, with those 4 big TL's in the house.
I also have stored 2 pairs of HPCM's, a pair of ALS40 Mk2a with the BR drivers, 2 pairs of Compacts and 3 pairs of Super Compacts Mk2.
Also when people started buying those plastic dolby sets, i started to buy all
the spares i could lay my hands on.
This was my introduction in this forum, hope te learn a lot about IMF and technical details about them.
Kind regards,
Johan Nanninga
Netherlands
DSJR
Between us and them
You must be single sir......
Glad you enjoy your IMF's. A shame that these days, speakers that size would be regarded as extremely anti-social. I bet many companies would love to make speakers this size, as it would be far more profitable for them I reckon than trying to shift hundreds of little squeak-boxes for a few hundred quid a pair...
Glad you enjoy your IMF's. A shame that these days, speakers that size would be regarded as extremely anti-social. I bet many companies would love to make speakers this size, as it would be far more profitable for them I reckon than trying to shift hundreds of little squeak-boxes for a few hundred quid a pair...
Hi,
In fact i'm not single, married and 3 lovely daugthers.
Just my relationship with IMF is from an earlier date than the relationship with my wife, so she had to adjust !!
Now i'll try the ultimate, trying to put those 2 pairs of HPCM's as effect channel in as well.
I must say d didn't read a lot about the Super Compact, which i believe is still a very good speaker.
Even know recording studios are still using those speakers as they do with the ASL40.
I wonder if Rolls Royce still uses IMF's ?
Best regards,
Johan
In fact i'm not single, married and 3 lovely daugthers.
Just my relationship with IMF is from an earlier date than the relationship with my wife, so she had to adjust !!
Now i'll try the ultimate, trying to put those 2 pairs of HPCM's as effect channel in as well.
I must say d didn't read a lot about the Super Compact, which i believe is still a very good speaker.
Even know recording studios are still using those speakers as they do with the ASL40.
I wonder if Rolls Royce still uses IMF's ?
Best regards,
Johan
DSJR
Between us and them
When I met my wife it was me that had to adjust
The Super Compact was designed to match the phase response of the bigger models, which is very important in surround/quadrophonic setups. The sound balance was similar to the earlier biggies too - slightly recessed in the mid and rather dull and bass thumpy with an LP12 source (two characteristics added together).
Today, the Super Compacts look positively large..........
The Super Compact was designed to match the phase response of the bigger models, which is very important in surround/quadrophonic setups. The sound balance was similar to the earlier biggies too - slightly recessed in the mid and rather dull and bass thumpy with an LP12 source (two characteristics added together).
Today, the Super Compacts look positively large..........
On Wed I went to pick up a TT for a friend from an ebay seller just down the road from me in Suffolk.
We got talking and he showed me his system....and there were a pair of IMF RSPM Mk. IV with the correct stands driven by CJ Premeier 12's!!!
Lovely!
Now my wife thinks my Maggie MG12's are too big...I thought I might show her these and give her a choice!!!
Regards
Gerry
We got talking and he showed me his system....and there were a pair of IMF RSPM Mk. IV with the correct stands driven by CJ Premeier 12's!!!
Lovely!
Now my wife thinks my Maggie MG12's are too big...I thought I might show her these and give her a choice!!!
Regards
Gerry
DSJR
Between us and them
PLEASE can you find any old reviews of IMF, Spendor, B&W etc (DM70's, DM1, DM3), KEF Concerto.. and save them in a free hosting service like Phobucket, which is the one I use for posting. You can store the pics in various sizes and simply copy the IMG link into a thread on here.
I'm sure Tony L would be fascinated enough to file these scans and if by chance you had the 1968 approx HiFi Sound turntable group test with the 401, TD124, Sony TTS3000 and Lenco G99 in it I'll love you forever
I only took HiFi Sound from the mid sixties onwards (yes, this sad soul was eight years old at the time - the bug bit deep!) and I learned so much from it. Strange that the memories of these tests stay with me, but somehow, these reviewers were able to tie test results to listening tests fairly easily, something many today find almost impossible.
I'm sure Tony L would be fascinated enough to file these scans and if by chance you had the 1968 approx HiFi Sound turntable group test with the 401, TD124, Sony TTS3000 and Lenco G99 in it I'll love you forever
I only took HiFi Sound from the mid sixties onwards (yes, this sad soul was eight years old at the time - the bug bit deep!) and I learned so much from it. Strange that the memories of these tests stay with me, but somehow, these reviewers were able to tie test results to listening tests fairly easily, something many today find almost impossible.
skyebridge
Registered User
my wife complains that the ruark solstice speakers i use are 'far too big and stick up like p-----s'. as she is an installation artist i am always on the defensive here; though i have observed that so many contemporary artists spoil their installations by having appallingly bad sound and vision. so i am thinking that i, too, should find and reproduce some life-size photographs of professional monitor iv's.
Hi DSJR. My public profile is now viewable. My magazines start from 1971 and run to mainly 1976. Then they are random after that as I had a mortgage and house which took me away from the HiFi hobby until I discovered all this vintage HiFi on eBay 6 months ago. Since then I have purchased vintage systems for my Study(s), Lounge(s), Hobby Workshop(s) etc.PLEASE can you find any old reviews of IMF, Spendor, B&W etc (DM70's, DM1, DM3), KEF Concerto.. and save them in a free hosting service like Phobucket, which is the one I use for posting. You can store the pics in various sizes and simply copy the IMG link into a thread on here.
I'm sure Tony L would be fascinated enough to file these scans and if by chance you had the 1968 approx HiFi Sound turntable group test with the 401, TD124, Sony TTS3000 and Lenco G99 in it I'll love you forever
I only took HiFi Sound from the mid sixties onwards (yes, this sad soul was eight years old at the time - the bug bit deep!) and I learned so much from it. Strange that the memories of these tests stay with me, but somehow, these reviewers were able to tie test results to listening tests fairly easily, something many today find almost impossible.
I started going through all the mags in July 08 just for trip down memory lane. I am fairly sure I can find some reviews on IMFs, the B&Ws . I am almost certain I have reviews on the DM70s and Concerto. I dont have any of these mags from the 60s. But I still own a Thorens TD124 Mk II, with SME Improved, Shure V15 IV, which I bought new and still use.
I have a continuous set of Radio Television & Hobbies/Electronics Australia magazines from June 1946 to February 1965 (~240 of them) in perfect condition that I am prepared to sell. These were my Dads which he bought as part of his AM Valve Radio hobby. Not sure there are many folks around who would lust after these now. But if any one has any suggestions, I would be interested to received these.
I will try this photobucket thing. If I get into trouble, my son can help me out.
I have an understanding family who laugh at my silly interest, but they see I am happy so they let me go, because resistance is useless.
Realist
pfm Member
Hello dere ! Just blagged meself a pair of scuffed IMF super-compact 2's for a xmas present to me . Got them home and saw that one of the mid drivers was, wait for it...........missing!
Should maybe explain that it was a second hand shop and I couldn't get them out of there quick enough when I saw the price sticker, 25euros the pair! Thangewverymuch.
For my next trick I shall proceed to locate and purchase said driver/s for as little as possible, or if anyone out there knows of some orphaned mids looking for a good home I'm yer man
Should maybe explain that it was a second hand shop and I couldn't get them out of there quick enough when I saw the price sticker, 25euros the pair! Thangewverymuch.
For my next trick I shall proceed to locate and purchase said driver/s for as little as possible, or if anyone out there knows of some orphaned mids looking for a good home I'm yer man