2ManyBoxes
pfm Member
There's another factor involved and that is that, if you have fitted carpets, you have to allow some room so that the rear spikes aren't resting on the track, that runs hard up against the base of a wall, that the carpet is then hooked to. I think it's only 2 to 3 cm, but if you're really tight for space it might come into play.
If you're running them passively then it is possible to move the crossovers out from behind the speakers by gently softening the A5 a bit and twisting them across. You'd have to stuff something between the crossover and the cabinet to hopefully isolate them a bit. And it does look more than a bit strange
If you're running them passively then it is possible to move the crossovers out from behind the speakers by gently softening the A5 a bit and twisting them across. You'd have to stuff something between the crossover and the cabinet to hopefully isolate them a bit. And it does look more than a bit strange
DoctorRad
pfm Member
2ManyBoxes
pfm Member
I owned a pair of SBLs 15 or more years ago and they were a nightmare. I tried everything I could to get them set up right and I was still scuppered by the room acoustics.
Over that time I've heard every berk under the sun saying that they're running SBLs when they've replaced all the drivers, or haven't bothered with the gasket or the seal, or they've rounded off the middle box spikes.
There is only one way of setting them up as the manufacturer intended and that is to get a copy of the official dealer instructions from me and following them to the letter. I can photograph them and email them to you if you PM me an email address. SBLs are not like any other speaker. Also it's not possible to do the typical male thing and disregard all instructions and make it up as you go along. You will fvck it up royally. However, my name is SBL Cassandra, this is the 32nd time I've offered someone a copy of the instructions and nobody has yet taken me up on it.
Attaching the tweeter box to the wall is an interesting idea that might actually work but there are obvious practical difficulties, you'd have to be pretty accurate and careful not to drop the tweeter box onto the middle box in the process.
What sandbags down the back might do I don't know but I do know that I don't understand a lot of the design thinking behind the SBLs at all. I don't think that that information has ever properly come to light and I doubt it ever will. The guy who designed them for Naim has probably signed a confidentiality agreement done by the same lawyers who do Porton Down's.
suzywong
Wot, no electrons?
OK, I’m game, do your dealer instructions differ or expand on the IBL/SBL User Manuals?.
And do you press lightly, as per the original UM, or firmly, as per the later edition?
2ManyBoxes
pfm Member
It says "apply firm pressure (enough to push the spikes through the aluminium) on top of 'B', ensuring it is stable and does not rock."
My dealer once demonstrated it to me. He's a pretty beefy bloke with big hands but he gave it a soft to medium thump with a closed fist.
There's lots of stuff in bold and even bold capitals warning of dire consequences loss of sale!!!!) if you don't do it right.
I've just taken some photos so if you PM me your email address I can pop them in the ether.
They expand on the user manual. That manual isn't intended as a full set of instructions, you're supposed to get your dealer to install them. The only thing they lack is how to cope with what can happen to a second-hand pair over the years, it was obviously written with new SBLs in mind.
My dealer once demonstrated it to me. He's a pretty beefy bloke with big hands but he gave it a soft to medium thump with a closed fist.
There's lots of stuff in bold and even bold capitals warning of dire consequences
loss of sale!!!!) if you don't do it right.I've just taken some photos so if you PM me your email address I can pop them in the ether.
They expand on the user manual. That manual isn't intended as a full set of instructions, you're supposed to get your dealer to install them. The only thing they lack is how to cope with what can happen to a second-hand pair over the years, it was obviously written with new SBLs in mind.
DoctorRad
pfm Member
Thanks for your swift response. What I'm unclear about is how, if the base cabinet and woofer cabinet are connected by spike they are also isolated using neoprene and silicone sealant? Is it the case that the spikes provide a sufficiently loose coupling that the two cabinets are do not 'interfere' with one another?
2ManyBoxes
pfm Member
I honestly don't know. I used to think that I sort of understood SBLs but after rereading those instructions I realise that I have no idea whatsoever. The spike / pad interface between the middle and lower box is a particular mystery.
The instruction seems to be that the spike should pierce the pad but only just touch the wood. So that means that the weight of the middle cabinet is taken by a combination of the lower cabinet wood and the pad itself, held in place by the staples into the wood.
Pick the bones out of that one
Does that isolate or couple them or a percentage of the two?
suzywong
Wot, no electrons?
It may be that the pads are intended stop the spikes from penetrating any further into the wood over a period of time.
LOL it’s a shame we weren’t having this discussion before I retired - the colleague I used to sit next to was not only a “clankie”, but had owned SBLs
LOL it’s a shame we weren’t having this discussion before I retired - the colleague I used to sit next to was not only a “clankie”, but had owned SBLs
2ManyBoxes
pfm Member
That's got to be one of the things they do, but they also must affect if the spikes isolate or transmit energy to the bottom box. The point of contact won't be a single sharp point any more but a torus, quite a lot bigger.
So the spikes sinking through the pads is supposed to prevent the middle box from rocking. They do say to check this after you put the box in place and apply the pressure. The pads also serve to stop the middle box from gradually vibrating a bigger looser fitting hole as they would just in MDF.
I remember something I read not in the manuals but elsewhere. The idea is to isolate the middle box from the lower one so that the driver vibrations don't end up exciting the big panels in the lower box, which would smear the bass. Also because of the gasket and seal, the middle and lower box act as one body of air, thus loading the driver with a bigger volume and deepening the bass.
So you get what you hear, tight low(ish) fast bass.
So the pad / spike arrangement does 3 things:
1) stops the middle box from rocking
2). stops the spikes from making a bigger hole for themselves
3). isolates the vibrations of the mid/bass driver from the lower box
Genius, but such a faff to set up.
2ManyBoxes
pfm Member
A question was asked about rooms and what SBLs like and don't like. I've only ever used them in 2 rooms so my experience is rather limited. One room was about 12' x 8' with 3 plasterboard walls and one solid outer wall. SBLs were positioned on either side of the window and radiator in the solid wall firing straight down the room. There was only about 1.5' between the speakers and the side walls because of the radiator.
Room 2 is about 17' x 12' with all four walls made from breeze block. Window and radiator is at the far narrow end but there is no room to put the speakers between the window and the side walls as the window is unusually deep. So speakers are sited on one side wall firing across, about 6' apart with about the same to the window at one end and the short wall at the other.
I've been plagued with a problem with sharp treble in both rooms. Unfortunately I tried to solve this with different equipment and didn't try room acoustics. As a result I've spent thousands but I've ended up with a kick-ass system once I finally tracked the problem down.
Both SBLs and to a lesser extent SL2s produce a narrow beam of off-axis treble, which is pretty harsh. You hear this as sibilance, female voices sounding screechy or higher frequency kerrangs from guitars nearly taking your head off. The critical thing is to make sure that that treble beam does not bounce off the side wall and hit your ears. The surface that it hits at the first reflection point on the side walls must either be damped or angled so that the beam misses your ears at the listening position.
I really only properly got going with room treatments in room 2. The window has a heavy curtain with a second insulation layer on a second rail behind it. That works very well, I didn't have a problem on that side. I also put acoustic foam on the other side wall and between the speakers but too high, above the tweeter - ear level. I messed about a lot with putting diffusers behind my head but with little real result.
The problem was caused by some record cabinets that I had on the right-hand side wall. These are stacked cubes with 2 cm thick walls made of nice varnished wood on all the faces. It just so happened that the tweeter, my ears and the top wall of the upper cabinet were all at exactly the same height. So, as the cabinet was quite wide, there was a spot on the face of the top edge of the cabinet where this treble beam was bouncing straight off the hard surface and into my right ear.
The record cabinet had its back to the wall. All I had to do was to rotate the cabinet through about 20 degrees so that the treble beam is now hitting the wall behind my head where there is a set of book shelves filled with different sizes of paperbacks and all sorts of different soft things in front of them. This completely absorbs the treble beam.
Problem solved.
I do wonder sometimes if I really needed to go active, buy 2 Avondale A260Zs and eventually land a pair of SL2s. However, I've done it now and my God it sounds good
For those who don't know what a reflection point is, it's easy to explain with a diagram but not so easy with words.
The tweeters in your speakers will be spraying treble straight at you as you sit in your usual chair but also in all directions in front of it, including towards the side walls. The important level is the line between your tweeters and your ears.
Now imagine a flat level triangle with the above line as the base and the opposite apex on the side wall. If your side walls are nice and smooth then there will be a point on the wall where the beam of treble will come in at an angle and bounce out again at the same angle. That is a reflection point. The problem is that the reflected beam goes straight into your ear with, for SBLs and SL2s, not good results.
It's called a first reflection point because it's the first one. Unless it's absorbed, the beam will carry on and bounce off a second reflection point on the wall behind you. And so on.
You know sometime I'm going to have to write a book
Room 2 is about 17' x 12' with all four walls made from breeze block. Window and radiator is at the far narrow end but there is no room to put the speakers between the window and the side walls as the window is unusually deep. So speakers are sited on one side wall firing across, about 6' apart with about the same to the window at one end and the short wall at the other.
I've been plagued with a problem with sharp treble in both rooms. Unfortunately I tried to solve this with different equipment and didn't try room acoustics. As a result I've spent thousands but I've ended up with a kick-ass system once I finally tracked the problem down.
Both SBLs and to a lesser extent SL2s produce a narrow beam of off-axis treble, which is pretty harsh. You hear this as sibilance, female voices sounding screechy or higher frequency kerrangs from guitars nearly taking your head off. The critical thing is to make sure that that treble beam does not bounce off the side wall and hit your ears. The surface that it hits at the first reflection point on the side walls must either be damped or angled so that the beam misses your ears at the listening position.
I really only properly got going with room treatments in room 2. The window has a heavy curtain with a second insulation layer on a second rail behind it. That works very well, I didn't have a problem on that side. I also put acoustic foam on the other side wall and between the speakers but too high, above the tweeter - ear level. I messed about a lot with putting diffusers behind my head but with little real result.
The problem was caused by some record cabinets that I had on the right-hand side wall. These are stacked cubes with 2 cm thick walls made of nice varnished wood on all the faces. It just so happened that the tweeter, my ears and the top wall of the upper cabinet were all at exactly the same height. So, as the cabinet was quite wide, there was a spot on the face of the top edge of the cabinet where this treble beam was bouncing straight off the hard surface and into my right ear.
The record cabinet had its back to the wall. All I had to do was to rotate the cabinet through about 20 degrees so that the treble beam is now hitting the wall behind my head where there is a set of book shelves filled with different sizes of paperbacks and all sorts of different soft things in front of them. This completely absorbs the treble beam.
Problem solved.
I do wonder sometimes if I really needed to go active, buy 2 Avondale A260Zs and eventually land a pair of SL2s. However, I've done it now and my God it sounds good
For those who don't know what a reflection point is, it's easy to explain with a diagram but not so easy with words.
The tweeters in your speakers will be spraying treble straight at you as you sit in your usual chair but also in all directions in front of it, including towards the side walls. The important level is the line between your tweeters and your ears.
Now imagine a flat level triangle with the above line as the base and the opposite apex on the side wall. If your side walls are nice and smooth then there will be a point on the wall where the beam of treble will come in at an angle and bounce out again at the same angle. That is a reflection point. The problem is that the reflected beam goes straight into your ear with, for SBLs and SL2s, not good results.
It's called a first reflection point because it's the first one. Unless it's absorbed, the beam will carry on and bounce off a second reflection point on the wall behind you. And so on.
You know sometime I'm going to have to write a book
DoctorRad
pfm Member
Pick the bones out of that one
Well, my thoughts exactly... but I've now realised that the back spikes are on the frame, and the front spikes appear to be 'isolated' from the base cabinet as can be seen in the photo below
What might be interesting to try is using compliant supports such as sorbothane pads of the correct thickness instead of the spikes. Would probably be different, but whether or not better would obviously be a subjective matter.
Can anyone comment on whether the silicone mastic is used simply to produce a seal, or if the fact that it has a degree of mechanical compliance ('squishiness') is significant? I would have thought that at audio frequencies it would actually be fairly rigid? If it's only there to produce a seal, using Sugru or similar in the right way would still produce a good seal, but allow repeated dismantling and reassembly without needing a fresh application. You'd assemble with cling film to initially stop the Sugru sticking to the surfaces, possibly roll it out to a consistent thickness with a pastry rolling pin, and then use a thin film of oil to produce an airtight seal.
