Hello from Leuchars

[walpurgis]

Needs close to 100watt amp to make these move (seem to like current) and damping factor as high as you can

IMFs are even worse. Not so much in power needs which I suspect are pretty similar, but they are even more loosely damped to my ears and certainly don't sound right with an amp that doesn't have a good grip. I suspect the main speaker differences are likely due to the more tightly tapered acoustic line and smaller exit port on the R50s.

[mr1macuk]

By looks of design IMF use rear wave... R50's do not

To my ears IMF's have impressive (but not accurate ) bass and sound 70's... Very LP12... Fun, flat soundstage that's not that accurate but boogie along a funky bassline beautifully, sound warm etc...

R50's image crazy good, they are very flat from 20hz to over 30khz and especially with falcon crossovers sound timeless... Even applause doesn't sound shut in or fixed to box which is rare in a box speaker. If I had to describe them its like an LS3/5a with real deep bass and maybe just a smidge smoother top end. Very different beast to an IMG (and due to IMF's impressive 70's sound they cost a bomb bit r50's can be found as cheap as £50 on gumtree)

[mr1macuk]

Phono stage added. Trigon Vanguard for under £100 if I like it I'll upgrade with volcano PSU. It's MM/MC and has adjustment for gain, resistance, capacitance and switchable subsonic filter. All in all a great wee stage for budget price

[archiesdad]

Howdy and welcome John from nearby Dunfermline, enjoy the forum.

[mr1macuk]

Lived there for a good few years myself... And judging by your s2000 sig you might have seen my bright red Nissan 200sx (s13) about Dunfermline 8-10yr ago

[walpurgis]

By looks of design IMF use rear wave... R50's do not

Yes they do. Both the big IMFs and the Cambridge R40 and R50 are back loaded transmission line designs.

Here's a diagram for yours:

[mr1macuk]

Yes think Imf reuses rear wave and r50 damps it out before exit of the wave... I know for defo r50 damps it out as in the dot plans it gives a minimum height but also says you can make it taller if you like giving a longer Line.

The design of IMF channel and using the bumpy pyramidy foam stuff on the walls of the transmission line made me think it was reusing the 1/4 wave though could be wrong on IMF if they are not using rear wave then, agreed, under damped

[walpurgis]

Both makes use a 1/4 wavelength tapered line which produces a port pulse which is partly in phase with lower frequency output from the front of the bass driver. Compared to IMFs, the line of the Cambridge is more constricted and the port is quite small in relation to the B139 diaphragm area. Presumably this is more resistive, making for a better damped bass.

[mr1macuk]

The r50 throws rear wave away as length of line is minimum 1/4 or anywhere longer if it re-used rear wave line length would have to be fixed so fit design plans would not state can be longer but no smaller (it's the min length required to fully damp rear wave away).

Any r50 with audible output from line in usually means stuffing is needing re-done.

[mr1macuk]

Iirc the imf has no wool or stuffing just the acoustic shaped foam on the surfaces to damp it a little r50's wool damps line completely. Re-stuff an r50 and you'll almost nothing out of end of line