I’m about to replace the spacers between the upper and lower cabinet. Is there a correct orientation for the little bumps on the end of the spacer arms? I assume it works better either facing up or down, but as a starting point will at least have them consistent. The spacers that I have are anodised silver (the finish appears rougher) on the side with the raised point)
(252 through the tweeter port is coincidental but serendipitous)
Thanks @Richard.Dane . When I bought my SL2s the washers were basically flat, so it was impossible to tell which side had the nodules.
I put in new washers tonight. Then flipped them over to install them correctly. All this practice is making it a lot easier to assemble the speakers than the first time I did
I’m not sure if it’s confirmation bias, but the speakers are sounding nicer with the new washers in. Wish you were here was a lot more present, and I noticed the sound of Dave Gilmore settling into his stool as the sky moves on from the opening guitar
Richard I hope this is the correct solder.
Has multicore Crystal 505 and a lead warning.
Cost twice as much as the other stuff (which has already gone to a friends, call me the solder fairy) l have googled the heck out of it and this solder is what comes up. Cheers
Cheers, Will done. Think I have enough wire to cut the old solder off. I did email Naim last year and they did say I can use it, being 08 it did surprise me a bit. Knowing my grammar I probably didn’t relay about mixing it and they were just saying I can use it
Will take my speakers apart tomorrow. Is there a specified distance for the ‘gap’ between the boxes? Looking at mine in-situ I can see a clear air space but not sure what this should be, ie whether I will need to buy more bumpy washers.
The gap is critical and is defined precisely by the tiny bumps on the metal washers. It is the gap between the two metal interface plates that allows the interface to act like a sealed box. Change that and you change the way this works (or not).
Thanks. I guess the only way to be sure they have not flattened a bit is to get new ones then.
Tiny investment plus the £10 of foam to freshen them up.
Out of interest how does a gap allow them to act as sealed boxes? Intuitively that feels the wrong way round. Feel free to take a pass on that if the answer is highly technical!
As you say, reticulated foam is something like a network made from ‘the edges of bubbles when the bubbles have burst’.
Reticulated or Open Cell foam is usually used in speaker grilles, AFAIK, because it has little effect on SQ as the soundwaves pass through it.
Speaker cabinet damping is usually done using using Closed Cell foam, AFAIK.
[Speculation alert - That would make sense to me because I’d expect closed cell foam to more effectively absorb the energy of any soundwaves in the tweeter cabinet and to provide a more solid surface to dampen any vibrations in the cabinet walls.]
Anyway, that’s theory.
In the end, what’s most important is how the cabinets sound with any particular damping material.
Photos below of the foam from my tweeter cabinets.
This looks like closed cell foam to me - but then I’m no foam engineer.
Wild guess - perhaps the answer is that speaker grilles tend to be made from less dense open cell foams (around 30PPI) - but more dense open cell foams that are say 80 PPI (pores per inch) are fine to use as internal speaker cabinet damping materials?
@NeilS @roy.george
In case you have any insights about closed vs open cell foams please let us know.
Maybe the 80ppi rating is the significant aspect here, as you say, it is less reticulated, or denser, than the more open foams used in speaker grille foam?
Plus, speaker grilles aren’t entirely transparent to sound, nor are they typically 20 odd mm thick. As I understand damping materials used in speaker cabs are for two reasons, mass damping of walls (bitumen panels etc) and wadding to increase effective cabinet volume/attenuate reflections. I would have thought reticulated foam would play a similar role to wadding, you need sound to pass through, albeit with resistance.
Guessing though, would love to hear the rationale behind the spec!
(a close relative was a foam engineer, alas they are no longer with us, and I only absorbed a fraction of their knowledge! I do recall that you can vary density and degree of reticulation, the former just by using different densities of PU foam, the latter by leaving it in the solution that dissolves the walls for different times. Though it looks like the main spec is just the PPI rating)
FYI - there is also a vendor on a popular auction site who sells ‘NAIM SBL replacement foam set’ and has 100% positive feedback, who has offered to get a minimum order of 80PPI open cell foam.
Unwanted sounds are generally called colorations and these should be minimised to an acceptable level. There is no specific definition of coloration limits so… Different cabinet designs and shapes, have differing colorations, some leading to what is well known as ‘the box sound’. In this respect small cabinets can be worse. It’s actually more difficult to make a ‘good’, small, speaker than a larger one.
To prevent / reduce internal cabinet reflections from emerging out through the speaker cone, creating coloration, a thick wad of felt, say (20 - 25) mm, may be placed on the rear cabinet wall, behind the drivers. […] If you have vented rear pole assemblies don’t forget to cut a hole in the material to allow the vent to breathe. This should be augmented by foam damping on the other interior cabinet walls of say (10 - 16)mm. Small cabinet boxes may need to be slightly larger in volume to offset the lost volume due to the damping materials. There is no easy way to guess or measure the actual felt / foam volume, some experimentation and listening trials are required. The use of Bitumastic Damping in small cabinets is not often required, as small boxes are very stiff and hence flex much less than larger panels."
I think there may not be one perfect single way to damp the SL2 tweeter cabinet.
It may be that some foams with different qualities will suit a listener’s room and system and preferences better than others.
Imo your thinking to much into it. Its a tweeter not a woofer, an open box design that uses the rear wall reflexion. Has no foam on the top or the bottom only sides. The way I think (which is usually not that sharp), the foam is used just to help guide the wave form in a straighter line and not to dampen as such, possibly to give slightly more speed on the vertical than horizontal. If you think about the wave form/length the depth of the box may have a lot to do with it, how it narrows from front to back which I’m sure it has very much something to do with sound stage.
At the end of the day you have the correct information given to you by the people who designed it. With out any shadow of doubt Mr George and co have been there and done that with several different types of products which has resulted with what has been used and said. Mate these guys aren’t green horns.
Obviously I’m no rocket scientist in fact I’m just an under paid truck driver who works days and nights for the love of his wife and the love of Naim audio which delivers the music just right for me.
I 100% trust in Richard and Neil to knowingly give the correct information and not knowingly lead anybody down the garden path (and I’m not saying you do not believe them) Just It’s not time to confuse or reinvent the wheel “Trust in the Force Luke”.
In saying that, if you like it different spec foam and it works for you why not. After all it’s all part of the fun!
Done the foam change. My foam looked just as Jim’s ie very crumbly, and came out more or less in fragments. One speaker seemed better than the other not sure why.
I used the 12mm Wilson Audio foam (that thisckness includes the cardboard back). Not hard to trim a piece that fits well. This thickness fits behind the block you can see in Jim’s picture half way down the front ‘wall’. All looks quite snug.
Bearing in mind the original foam is not exactly cut to size around the central ‘arch’ the fixing block or indeed what look like large blobs of sealant inside the cabinet I am not sure a perfect fit is needed.
FWIW the inside of my box is painted black.
One pic below of the pieces before inserting. I did not peel off the backing and stick them in place, it seemed unnecessary. Second pic shows end result.
Oh, and I think they sound pretty much the same if I am honest!
