I have some R700s and the carpet roll tube for the mids is bothering me. These tubes for mids never sound good to me, with voice particularly. There is barely half an inch of space anywhere around the driver. Upon inspection, I found double the wadding in one, than the other. Kef have no idea what weight is right. However, I doubt my ear will ever be happy with this compromised design. I'm starting to think about the R100 as it's full range. I imagine it's the same drivers, with different suspension. In a proper box, that won't suffer the small cavity problem. I guess I need someone that bought the R100 as surrounds, with bigger R-series mains, to sum them up. I do have spare bass units from these R700s and some spare mid/tops to start a fresh build. I tend to sit at my computer using them, so some R100s might just work for me, with a sub.
I don't know anywhere better to get a subjective review of these, or cardboard tube use in general. Perhaps Mine are just badly wadded. I had to take some out of one, to screw the driver in. It was that compressed at the back. While nothing exists in the air gap, around the basket.
I don't know anywhere better to get a subjective review of these, or cardboard tube use in general. Perhaps Mine are just badly wadded. I had to take some out of one, to screw the driver in. It was that compressed at the back. While nothing exists in the air gap, around the basket.
Last edited:
My 2 ct? Don't. Sell them and buy something else, a kit or proven DIY design. You can't equal the result of these KEF's without quite some knowledge and gear. The carpet roll tubes are there for a reason, but do you have any idea what that reason is? Do you get the importance of the right stuffing? Presumptions bring you nothing, only some biased opinion and a result you might like, but that is most likely worse in objective terms.
I wouldn't randomly hack into an R700 either. I rather enjoy mine. I have no idea what this carpet roll tube is either.
I'd stick with the controlled directivity designs. There are some non-KEF options around if KEF doesn't suit your fancy.
FWIW: I listened to some R300 before buying the R700. The 300 was pretty capable but I found a set of R700 on close-out so I figured I'd get those instead. If I was going for one of KEF's smaller speakers, I'd probably go for the LS-50.
Tom
I'd stick with the controlled directivity designs. There are some non-KEF options around if KEF doesn't suit your fancy.
FWIW: I listened to some R300 before buying the R700. The 300 was pretty capable but I found a set of R700 on close-out so I figured I'd get those instead. If I was going for one of KEF's smaller speakers, I'd probably go for the LS-50.
Tom
OK. Cardboard tubes don’t sound by themselves. The amount of stuffing in a midrange enclosure might not be critical at all. A small midrange enclosure has benefits to a bigger one. Enlarging the mid encosure screws your crossover setup. If you please.
Hi,
If i remember correctly friendly1uk bought a second hand pair of R700 with one loudspeaker sounding nice and the other not so.
From the description given in first post it seems one of the loudspeaker have been 'tweaked' probably by a previous owner ( not the same amount of wadding).
Sealed mid dedicated enclosure like this one should be stuffed to the max. At least this is my experience with 'high end' design from 80's/90's and from many discussion here with people like Earl Geddes and other experienced users.
I once asked to more experienced designer than i am (Scottmoose) if there is a limit of amount of absorber than can be put in an enclosure like that.
The answer had been there is a limit ( a point where the diaphragm start to be 'loaded' too much) but in practice i doubt it could be achievable.
Anyway the point is to kill/absorb the backwave/ internal reflections and such can only be with a lot of absorbing material effective in the reproduced range of the driver.
Which lead to enclosure size: too large an enclosure and you start to shift the internal resonance ( standing wave) lower in freq. Which might be an issue relative too absorber capability.
I understand the OP concerns relative to the enclosure size and shape but once stuffed with the right material it works surprisingly well. It's been my experience with my 'big' three way ( Technics SB-M2) with the mid driver located into a small subenclosure overstuffed with material ( close to what is availlable as Metisse product in France).
Tryed with and without and in my opinion there's no contest in results.
Compromised design i don't think so. A compromise in the design choice of course but what isn't in loudspeaker design?
Maybe the OP like more 'livelyness' brought by unstuffed enclosure own reflections? It's a matter of taste, i don't.
I'm with Mordikai about Kef's Meta drivers: i've been experimenting with LS50 Meta uniQ for a year and there is definitely something about the highs i find appealing. Not the definitive answer for coax imho ( could Kef do a 12"high efficiency+compression driver with the associated high dynamic behavior keeping the good from this range and it could be to me!) but way better than many other smallish coaxial drivers.
If i remember correctly friendly1uk bought a second hand pair of R700 with one loudspeaker sounding nice and the other not so.
From the description given in first post it seems one of the loudspeaker have been 'tweaked' probably by a previous owner ( not the same amount of wadding).
Sealed mid dedicated enclosure like this one should be stuffed to the max. At least this is my experience with 'high end' design from 80's/90's and from many discussion here with people like Earl Geddes and other experienced users.
I once asked to more experienced designer than i am (Scottmoose) if there is a limit of amount of absorber than can be put in an enclosure like that.
The answer had been there is a limit ( a point where the diaphragm start to be 'loaded' too much) but in practice i doubt it could be achievable.
Anyway the point is to kill/absorb the backwave/ internal reflections and such can only be with a lot of absorbing material effective in the reproduced range of the driver.
Which lead to enclosure size: too large an enclosure and you start to shift the internal resonance ( standing wave) lower in freq. Which might be an issue relative too absorber capability.
I understand the OP concerns relative to the enclosure size and shape but once stuffed with the right material it works surprisingly well. It's been my experience with my 'big' three way ( Technics SB-M2) with the mid driver located into a small subenclosure overstuffed with material ( close to what is availlable as Metisse product in France).
Tryed with and without and in my opinion there's no contest in results.
Compromised design i don't think so. A compromise in the design choice of course but what isn't in loudspeaker design?
Maybe the OP like more 'livelyness' brought by unstuffed enclosure own reflections? It's a matter of taste, i don't.
I'm with Mordikai about Kef's Meta drivers: i've been experimenting with LS50 Meta uniQ for a year and there is definitely something about the highs i find appealing. Not the definitive answer for coax imho ( could Kef do a 12"high efficiency+compression driver with the associated high dynamic behavior keeping the good from this range and it could be to me!) but way better than many other smallish coaxial drivers.
Last edited:
Basically what I tried to say and I didn’t know about the malfunctioning speaker.
Good memory, and understanding of the problem. The tube is so close to the cone, that reflections are a problem. Noise from the back of the cone should be lost, not allowed to come back and mix/cancel and such. The application is floored. The R100 (or R50) Take my uni-q driver, and put it in a proper box. No tube. I feel this must sound better, but I'm unlikely to find any in a shop around me. It's not the actual same uni-q in them, as it has suspension that allows it to play bass.
On a personal note, I like the dark sound of the kefs. I sat with 5 uni-q drivers to pick the darkest sounding pair. Hence I have 3 on the shelf doing nothing. Along with a couple of cones that are marked. I never figured out why the boxes sound different (except it is the boxes) and they're not available from Kef.
I could do a better job with the wadding I know, but feel not having speakers of this type, is probably the better option. I don't mean to hack up the kefs, as some have thought. They don't offer me anything, if the R100 looses the rear wave better. It must do, right?
Edit: The wadding in one of the tubes is different to that in the main enclosure. The other tube has the same wadding as the enclosure. Which is slightly less dense, but they used two pieces. Cut and rolled the same way. But just shoved to the back in each. I shared it out, but it's in the wrong place. It's unusual history. Though this is just a side note really.
I wonder when we will be buying Meta material in sheet form. That would be great. Not possible yet, but layers of open cell foam, of different pore sizes might help.
Last edited:
Well, i disagree the application is floored: someone probably messed with your loudspeakers so all bets are off about what Kef initially did.
I repeat, my experience is the principle of sealed+stuffed to the max is in practice totally ok if done as it should.
Ok. May i ask a question?
You say you feel this must sound better, but have you tried to verify your hypothesis?
It's a bit of work but should help define if the shape and side of enclosure are culprit to what bother you: build some test box maybe 2,
one with the actual volume seen by the driver in the R700, another one with 10 liters internal volume ( approx what R100 have).
Put one of your spare driver as a guinea pig in them, and play with the volume of absorber material used in each one.
Then send a filtered pink noise to the mid driver ( 500hz high pass, 2,9khz lowpass it will mimic what the mid driver experience in the R700) and listen to results, resonance will be obvious and effectiveness of absorber to damp them too. Better have 'good' headphone as reference to compare to.
You could run an impedance measurement too as any issue will reflect on the curve as 'wiggles' on graph. With the right amount of stuffing the 'wiggles' will disapear.
Repeat with larger box and draw your own conclusion.
No need for fancy material for the box or absorber to be used, it's just to verify your hypothesis the issue is box shape/volume and absorbent related.
We could explain what will happen right now, but you'll be biased. Better do the experiment first and then discuss results afterward in my view. But if you really want to know what to expect other members or I can do but you will be biased...
About drivers yes they are differents between 2 ways and 3 ways. As you said the one you have is a pure mid/tweeter, the others are midbass/tweeter.
It imply a number of things which will alter results and design choices.
In my view this kind of coax ( Tannoy style, the mid(/bass) membrane is used as part of the waveguide) should not play bass, hence 3 way design should be prefered because of intermodulation distortion issues. Other points in driver design can be optimised too, including suspension design limiting unavoidable diffraction with a pure mid, which seems not possible with a driver which have to have higher displacement ( play bass).
Iow, your driver need a ( sub) woofer, hence 3 way design. If you want something for nearfield then it'll have to be Waw/ Fast principle oriented ( Planet10 kind of design).
Others and I could give you some of the reason why they sound different but you'll be biased before experiments...
How lucky to have guinea pig drivers!
About dark sounding: eq are great tools to shape your overall outcome. I don't imply this is the reason some sound darker than others but it offer a way to mimic the behaviour of your prefered one. If you have a computer as source, there is tons of vst plug ins to experiment with such things in a free way...
It's your start hypothesis it would be better, only experiment will tell.
There is many absorber type that are effective in the freq range the mid play: glasswool, rockwool, Metisse kind i already talked about, AngelHairs ( pretty effective and have advantages but pricey), melamine foam ( 'basotect' or ...magic eraser sponge), a mix of all,...... the point is to try to find the one which work in your case. Impedance plot will tell you the truth ( our ears only can't).
It won't happen: metamaterial is a bank of tuned helmotz resonators so it's application dependant. If you have a 3d printer and time to spare you could print your own but Kef's one nope.
If you are ok with open cell foam, then basotect ( or magic eraser sponge) is the way to go imho. Xrk971 use them to good results for some time now, i tried the sponge it works... basotect is easier if you need to shape them ( sheets are bigger than the standard sponge size)).
Making them their own box was on my mind, but if I like that, it leaves me building new speakers from scratch. It's not really what I hope for. I was hoping someone here had experience of the R100's, and might address any differences in these off the shelf designs. I might then just be building a bass speaker to finish what the R100's start. If the R100 seemed good.
I'm actually watching them on eBay a lot. Thinking about the financial cost of buying some to demo, if I were to then sell them again. It might be better for me than building something. I do have some hand tools, but no proper work space. I also have a miniDSP HD, which is very helpful. Forum member @mkane77g gave me that, literally for free. A gesture that I will never forget. I also have the different crossover points of the R300/500/700 Which seem to just get higher (respectively) to deal with power handling requirements. Non were more favourable to my ear.
I have had them in massive boxes, and they are certainly not made for that. I can see the rabbit hole of incremental trial and error. I have my transmission line build knocking on 20 years I imagine.
The R100 is well reviewed online, and it's sound surely fits in the R-range. It's possible I have a two box solution in my future, where an R100 sits upon another box containing a driver, that gives me an R300 like build. Just using two boxes. Then, that bottom box can also take a sub. Dreaming further ahead, said sub could be in the back. As room EQ is better at taming what you have, than giving you what you don't have.
It doesn't look like we have an R100 owner passing though, so I will probably buy some used ones. It will be informative, and they might even end up staying.
I will circle back around to the R700 mid enclosures at some point. I really need to find why they sound different as empty boxes. Until then, I have little reason to be adding wadding properly. I do suspect one uni-q driver was removed, and refitted with the cables and wadding all at the back, so the act of tightening the screws was a bit like a press. As I removed one, it was pushing itself out, and as I refitted it 'as was' I basically chickened out. I thought the tube would fall off, or the screws eat the MDF if I tried to flush up the driver. It was obvious the cables and wadding couldn't live back there. I have not found a tube to be loose, but don't want to force the issue either. Both physically measure about the same. I need to stick a mic to them, and place a full range speaker on top of the Kef cab to resonate it. It doesn't sound like it could be anything else, though tapping on the box tells a different story. The cabinet is divided internally, as each bass has it's own enclosure. This dividing board meets the baffle between the uni-q and the lower driver. Tapping here yields different results. About as different as the speakers sound. Though the sound seems internal. Had these of been my build, I would of got slap-happy with the glue by now, but I have an undue reverence for these Kefs. Some might say they are the best thing I own. A 50th birthday present to myself.
They have been with me a little while now, so I may stop messing about, and pull them right to pieces soon. I bet I could move a mic around like a stethoscope to find a loose bit, but so far, I have not progressed past phone apps with simple spectrum analysis. I can't graph out impedance curves, or look at pulse responces. I could test at a spot frequency as I understand the principle, but it's like launching the space shuttle with a valve based PC around here
I'm actually watching them on eBay a lot. Thinking about the financial cost of buying some to demo, if I were to then sell them again. It might be better for me than building something. I do have some hand tools, but no proper work space. I also have a miniDSP HD, which is very helpful. Forum member @mkane77g gave me that, literally for free. A gesture that I will never forget. I also have the different crossover points of the R300/500/700 Which seem to just get higher (respectively) to deal with power handling requirements. Non were more favourable to my ear.
I have had them in massive boxes, and they are certainly not made for that. I can see the rabbit hole of incremental trial and error. I have my transmission line build knocking on 20 years I imagine.
The R100 is well reviewed online, and it's sound surely fits in the R-range. It's possible I have a two box solution in my future, where an R100 sits upon another box containing a driver, that gives me an R300 like build. Just using two boxes. Then, that bottom box can also take a sub. Dreaming further ahead, said sub could be in the back. As room EQ is better at taming what you have, than giving you what you don't have.
It doesn't look like we have an R100 owner passing though, so I will probably buy some used ones. It will be informative, and they might even end up staying.
I will circle back around to the R700 mid enclosures at some point. I really need to find why they sound different as empty boxes. Until then, I have little reason to be adding wadding properly. I do suspect one uni-q driver was removed, and refitted with the cables and wadding all at the back, so the act of tightening the screws was a bit like a press. As I removed one, it was pushing itself out, and as I refitted it 'as was' I basically chickened out. I thought the tube would fall off, or the screws eat the MDF if I tried to flush up the driver. It was obvious the cables and wadding couldn't live back there. I have not found a tube to be loose, but don't want to force the issue either. Both physically measure about the same. I need to stick a mic to them, and place a full range speaker on top of the Kef cab to resonate it. It doesn't sound like it could be anything else, though tapping on the box tells a different story. The cabinet is divided internally, as each bass has it's own enclosure. This dividing board meets the baffle between the uni-q and the lower driver. Tapping here yields different results. About as different as the speakers sound. Though the sound seems internal. Had these of been my build, I would of got slap-happy with the glue by now, but I have an undue reverence for these Kefs. Some might say they are the best thing I own. A 50th birthday present to myself.
They have been with me a little while now, so I may stop messing about, and pull them right to pieces soon. I bet I could move a mic around like a stethoscope to find a loose bit, but so far, I have not progressed past phone apps with simple spectrum analysis. I can't graph out impedance curves, or look at pulse responces. I could test at a spot frequency as I understand the principle, but it's like launching the space shuttle with a valve based PC around here
While stated it's for speakers, then say it's for amplifier housings more often. That's quite thought provoking.
Ultimately, it's a bit extravagant for me. £60 for 200g, but I don't even need 5g. The stuff in the Kef's is likely polyester, and doesn't even match. This seems to be in a different league. I have a range of wadding I can try though, and this was interesting to see. A technical step forward, I didn't expect.
I can't actually line the housing, then insert the driver.
The magnet is so tight through the hole, there are cutouts for the cables, which are still tight. Once in, the tube is very little wider. IIRC about 5mm clearance. Any angel hair added, would be more within the chassis than enclosure. If I were to wrap a typical polyester wadding around them, I would have real fun trying to shoehorn it though the baffle, without bunching. The only real option might be gluing wadding to the tube, so it can be compressed, then bounce back.
I don't imagine angel hair rubbing the cone would be without noise. Any more work there, is redesigning the driver.
Last edited:
Ok, i get your concern about damping damping material touching the cone but you can do something: use nylon stockings to cover the back of driver. It worked well in my case ( i asked politely to my darling if i could borrow some).
I would not speculate about damping material used: Kef prooved there is 'tricks' at play when they can: Mat is an example, the material they use to dampen capacitors in xover which is the same used in the box contruction of most of the range to implement Matrix CLD ( same idea Tannoy used in DMT range),... they know their stuff and are clever.
So even if the foam used seems 'regular' i don't see them not use something effective in the freq range.
But i may be wrong...
Anyway, who cares? I mean you already have taylored to your liking ( by choosing the dark driver) so why not push the work to an end?
I talk by experience as i entered in all this by customising my tool for work: the Technics i talked previously, gone from passive to tri amp with active filtering ( dsp). I've worked with them some 12 years and think i pushed them to the best i could do. Worthwile, instructive,....
Try what you have at hand and if you don't reach what please you then Angel Hair could be thought about... it works very nice and have advantage in that it can be compressed easily and then expand by it self. And it work as they claim from what i've seen. I wonder if it would'be an issue to have them rubbing on cone? I'm interested to try it at one time. Fit nice for a mid enclosure. Basotect works nice too.
https://www.panasorb.eu/lng/en/mous...m-light-grey-adhesive.html?type=N&language=en
Earl Geddes used some foam close to the one used as filter in aquarium to build a fully absorbing wall in his auditorium/studio/dedicated room at home ( it's leftovers from the foam plugs he used in the oblate spheroide waveguide of Summa and Abbey to tame HOM, iirc).
You got nothing to loose in trying things imho. Maybe you'll end up being in love with the R700 who knows? It's all i could wish you.
At worst you'll have gained knowledge and fun experimenting things (i hope so).
I would not speculate about damping material used: Kef prooved there is 'tricks' at play when they can: Mat is an example, the material they use to dampen capacitors in xover which is the same used in the box contruction of most of the range to implement Matrix CLD ( same idea Tannoy used in DMT range),... they know their stuff and are clever.
So even if the foam used seems 'regular' i don't see them not use something effective in the freq range.
But i may be wrong...
Anyway, who cares? I mean you already have taylored to your liking ( by choosing the dark driver) so why not push the work to an end?
I talk by experience as i entered in all this by customising my tool for work: the Technics i talked previously, gone from passive to tri amp with active filtering ( dsp). I've worked with them some 12 years and think i pushed them to the best i could do. Worthwile, instructive,....
Try what you have at hand and if you don't reach what please you then Angel Hair could be thought about... it works very nice and have advantage in that it can be compressed easily and then expand by it self. And it work as they claim from what i've seen. I wonder if it would'be an issue to have them rubbing on cone? I'm interested to try it at one time. Fit nice for a mid enclosure. Basotect works nice too.
https://www.panasorb.eu/lng/en/mous...m-light-grey-adhesive.html?type=N&language=en
Earl Geddes used some foam close to the one used as filter in aquarium to build a fully absorbing wall in his auditorium/studio/dedicated room at home ( it's leftovers from the foam plugs he used in the oblate spheroide waveguide of Summa and Abbey to tame HOM, iirc).
You got nothing to loose in trying things imho. Maybe you'll end up being in love with the R700 who knows? It's all i could wish you.
At worst you'll have gained knowledge and fun experimenting things (i hope so).
Last edited:
Comment > both on topic & off topic >
I can't believe so many can't relate to what "Carpet roll tube" is, and what it is often used for re. midrange drivers
After proper 'stuffing/damping' the resultant volume will determine the resonance & bandwidth of the mid.
OFF TOPIC >
I seem to notice how many British members seem to have a rather pompous, bossy and reactive response to things
I've seen "Carpet roll tube" used in few speakers, here's one great sounding example. The Sony SS-M9ED.
It performs well too! https://www.stereophile.com/floorloudspeakers/391/index.html
It performs well too! https://www.stereophile.com/floorloudspeakers/391/index.html
Attachments
Last edited:
Didn't you live just down the street last year?Comment > both on topic & off topic >
I can't believe so many can't relate to what "Carpet roll tube" is, and what it is often used for re. midrange drivers
After proper 'stuffing/damping' the resultant volume will determine the resonance & bandwidth of the mid.
OFF TOPIC >
I seem to notice how many British members seem to have a rather pompous, bossy and reactive response to things
Come on man, it's my thread. Yes it should be about me. That's not pompous, until at least the 3rd post.
I have been here (on diyaudio) 10 years, so yes I have turned it off and on again. To react that it's rude to answer questions with just questions, is in fact the polite response, in the UK. It shows distrust in any language. So with due diligence you read what you said again, looking for clues to peoples answers, such as sharpening my chain saw for a new midrange enclosure. Then decide who is actually on your wavelength. Where does their carpet come from. Is it just things dying on the floor, that make it softer. You have to wonder.
This is what job satisfaction looks like
It's actually not a bad material to use. It's not HDF or even MDF, but it's thick and sturdy, and very unlikely to ring at all. Standard length is 4 meters, and it holds many Kg over that distance. I have a pretty constant supply of the stuff in the UK, if ever someone needs a bit. It's generally about 80mm ID with ~8mm wall. Useful for bass ports to, though a little heavy. I have seen worse.