DBL refurbishment
Posted by: Willy on 06 June 2017
I sort of bought DBLs by accident. I had seen a pair sell on ebay for under £3k, in black, recent full driver replacement and described as mint. Unfortunately they were in south east, no boxes and thus required a van, a ferry crossing and a thousand mile drive to collect so I held fire. But the thought was there that liquidating my SL2s would have gone a long way towards funding those.
A few weeks later I popped into my local dealer, purely a social call as I was in the area at the time (arguably the best cobbler in NI is a few doors down). Mentioned the ebay DBLs and how I might have sprung had they been closer to home. He responded that he might know of a pair and he’d look into it. Several weeks later, after a holiday, I got a call that indeed there was a pair available locally. I expressed interest and inquired about auditioning/viewing them. After several calls it was clear that the seller had already purchased new speakers and the DBLs were boxed. I agreed a price, contingent on validating their condition.
There followed a period of frantic diy where I went above and beyond a request to paint the kitchen ceiling and instead build a whole new fitted kitchen, had a Rangemaster cooker and hood installed, and then announced that I might be getting some new speakers. I did use the word “bigger” though it is just possible I was breathing in at the time and it didn’t come across very distinctly.
One day a van arrived. Two men unloaded four large boxes and two enormous boxes into my home office/mancave. Fortunately looks can'y kill.
Waited for the dust to settle and unpacked. The condition of the speakers was far mint. Cosmetically I’d have described them as 7/10. Not such an issue as they are out of the way in my office but obviously has an effect on price. The bass driver surrounds were shot, one having a section of 3” missing. The pads on the bass boxes were perforated. The underside of the treble boxes were deeply gouged, 5+mm in depth. The spikes supporting the treble boxes were bent. The Velcro on the one bass box that had been bagged was reasonable, the other three had been packed without being bagged and thus the Velcro had been peeled back at the corners. Annoyingly the three bags were present in the bottom of one of the boxes. In packing the crossover had been resting on one of the gaskets and had produced a notch on both sides of it (over a few weeks these sprang back out). A section of the lower band on the tweeter support frame had been hacksawed out. Have been unable to determine why someone would do that, my theory being that it makes it possible to reach in and unplug the feed to the bass cabinet whilst it’s in situ.
On the plus side midrange and tweeters had been replaced approx. five years ago, though looks like they were done by someone wearing boxing gloves. Grilles were new USA sourced ones and looked the part.
I slept on it, did some calculations and made an offer based on what I reckoned it would cost me to restore them and what they would be worth in that restored state. After a few weeks of contemplation the seller agreed to my offer and the work began. I’ll focus here on the tweeter box restoration and update on the bass boxes as that’s still ongoing.
First off was the filling. As I said they were quite deeply gouged and I had to remove a lot of loose material to get back to a firm foundation. I initially used a box cutter to cut in and then finished off with a pointed grinding tool in a “dremel” (lidl equivalent) to smooth off the surface.
Filled the surface and sanded back to flat with a sanding block and 120 grit.
And filled.
Next up the spikes. As you can see from the photo they were bent. At least 6 of the 8 were visibly bent.
Approached Naim about replacements but they’re no longer stocked so I had some new ones made from M4 Stainless Steel. Got a dozen so as to have a few spares.
Glued nuts onto the spikes using a suitable adhesive.
Needed to get the correct height for the spikes so measured the height of the tweeter box and then set the starting position for the spikes to that distance down from the top of the cabinet. Needed a few tweaks to get them aligned and level but was relatively straightforward. Can clearly see the trapezium cutout in the tweeter support frame.
Not planning any major cosmetic work at his stage, just want to get them running but I did have a roll of double sided tape kicking around the office so I carefully cleaned under the loose corners of the Velcro and stuck them down. Actually made a significant improvement to the appearance.
Will follow up on the bass boxes later, currently waiting on new aluminium pads to complete that. Meanwhile current state...
Regards,
Willy.
Part 2. Bass Drivers.
As mentioned earlier the bass drivers were showing their age. Surrounds on both were “delicate” a large hole in one of them.
As can be seen Naim have modified the ATC drivers with a bit of waste pipe and a little grill at the back.
Ordered up shipping boxes from ATC and modified them with a circular cutout in the packing material to accommodate Naim’s modification to the driver. For good measure I set a piece of cardboard into the hole I cut in the packaging so that no loose polystyrene would get into the grill at the back of the drive unit.
ATC turned the drive units around in about a week. Really a very pleasant company to deal with. The drive units came back looking good as new, they even made up some bespoke Naim Audio labels for them!
The reconed drive units were not installed until after I’d refurbished their cabinets (will come back to that later). Torqued to the requisite 3.6Nm. Left for about a week and then retorqued (fractional movement on most of the bolts).
Finally a sliver of silicon around the periphery to seal them off.
So there we have two rebuilt bass boxes with reconed drivers.
Regards,
Willy.
Part 3. Gasket Kit.
First off was the preparation, filling and sanding to take the new aluminium pads.
Next up was positioning the pads. I’m sure this could be done just visually but I may have had too much time available when removing the old ones and I’d made a template of their locations.
For a half blind old codger such as myself peeling the backing paper off the pads was arguably the most difficult part of this whole operation but I got there eventually and positioned them using my template. I’d pre-cleaned the surface of dust but even so the adhesive on the pads is…….I now understand why they use staples as well.
I know a lot of folks have struggled with getting the staples in. In anticipation of this I’d conducted a set of experiments with the old pads and determined that this stapler was up to the task.
I got this one for free (along with a sizeable collection of pre-digital opera and classical boxed sets) but they’re available new for under #30. Anyway it did the trick though just to be sure I gave the staples a wee tap with a hammer.
Next up the gaskets. The old ones came off relatively easily. Then cleaned the surface with Isopropyl. Once again I made a template to assist with getting the gasket in the correct place. Stuck down the back edge first and then removed the remainder of the backing paper and stuck the whole thing down.
Did the spacer/slide-out/press bit and then applied the silicon, having first applied Fairy Liquid to both surfaces and letting it dry. Might have been a bit generous, more 6-7 than 5-6mm. Probably should have practised more. I’ll do better next time.
Installed bass boxes and removed spacers. Easier than I’d expected as they seemed to locate relatively easily into the indents.
Stuck the top boxes back, et voila.
Now the hard bit. Waiting 24hrs for the silicon to set. I'm off to the beach with the dog and I've got a beer in the fridge to follow that. That's the first 2 hours taken care of.
Willy.
I do like a good restoration thread - fantastic job there Willy 
At least the dog is enjoying the wait......
Willy.
ice kachang posted:lyndon posted:ICE KACHANG
you will need to remove the sealant between the bass driver cabinet and the lower cabinet
its pretty much straight forward mastic, most of it will peel off, the last bits that are left can be removed with a Stanley knife and or soapy water
obviously this will need re instating
lyndon
Thanks. They were originally built by Doug from Naim who I believe used 'fairly liquid' on the gasket. I was told that this meant that I should be able to remove the bass boxes without destroying the seal.
Finally got round to packing up my DBLs. Separating the Bass cabinet from the base was very simple. Gasket remained intact and mastic just peeled off.
The boxes don't half take up some space !
Dear Readers (or should that be Listeners?), Some months have passed I last posted on my “accidental” DBL purchase so I thought it time for an update.
I left off with the reconditioned speakers having about 15 hours playtime on them and being well pleased with what they were doing, and the potential I believed I could hear in them. Over the following months they continued to improve, indeed up to 5 months I could still detect week on week improvements. It was a fairly linear development excepting one very noticeable step about two weeks in where they opened up significantly over a very short time. Had a most enjoyable Thursday afternoon treating everyone within earshot to The Stranglers Rattus Norvegicus and other such guttural gems.
So where did they get to in absolute terms? Well despite being driven by the lowly 250 they were (past tense that, see where I’m going????) in almost every respect better than the active SL2s they replaced. Musically I’ve heard nothing like them, natural, effortless, thoroughly engaging, far and away the most musical speaker I’ve ever heard. Of course they do demand more than the poor 250 can deliver and this was I suspected responsible for a couple of anomalies.
Firstly the bass could get a bit muddled. Not in any way unmusical, not overblown, just that on upright bass playing you got the feeling that the amp was struggling to reign in the 15” ATCs, in particular otes didn't stop as quickly as they should.
Secondly the treble frequencies were delivered with an image size, soundstage, that seemed disproportionately small relatively to the rest of the sound. Not so bad when I was listening at my desk (left speaker pointing directly at my right ear). Within that image size constraint everything was detailed, realistic, glorious. I had considered this could be an issue with the tweeters, and they could be replaced at reasonable cost but being fundamental lazy (I’m very good at that) I decided to wait and see how much was down to underpowered amp and 24 year old crossover.
I’d have no difficulty living with these issues as overall everything was so much better than the active SL2s.
Ebay calling Canada…..
I had previously mentioned that one of the tweeter mounting plates was “cosmetically challenged” having at some point been treated to a recoat of fibre tip pen! Suspect this was to hide some scratches and likely some prior damage/straightening. Approached my dealer to talk to Naim to see if I could get a specification for the tweeter plates (dimensions, gauge, material) with a view to having some made. Fancied doing a pair in electric blue to match the back wall. Whilst nothing was happening with that I somehow spotted a single NBL tweeter assembly for sale on Ebay in Canada. From the pictures the plate looked mint so for £100 inc shipping I had a punt. Arrived and it’s perfect. I shall in due course, when the system is dismantled for room redecoration (apparently the blue is going to be changed to yellow) change it over.
And then there were three…
Again previously I’d sort of discounted the 135 route due to the dearth of them on the market at the moment so, with an eye still on 135 availability, I set about finding another 250. One came up sooner than expected. Terribly nice chap down in Devon had a Naim serviced olive up on Gumtree. Spoke to him and discussed him delivering it to Bristol with me paying for fuel. Next day he texted me a price cut for a quick sale and twas agreed. Transferred funds to my daughter in Bristol and the following weekend I had my third 250. Sat in her room for a couple of months, she was in Malaysia/Japan for a holiday, and eventually roped in her boyfriend to carry it to the Post Office where I’d prebooked Parcelforce.
He ain’t heavy, he’s my 250…….
Parcelforce took their time in picking it up and their first status message was “Collection attempted. Package overweight”. Mmmm. This suggested to me that they hadn’t picked it up and caused the outpouring of some expletive. Turns out they did pick it up and it was duly delivered without further issue. I had booked it in at 13Kg which I thought was sufficient, indeed in excess of the normal 12kg I’d use sending 250s (by Parcelforce) for servicing (I'd upped the weight to allow for cables not normally sent for the servicing). Attempted to weigh the package on our bathroom scales but they’re old and not very accurate. (One might argue that there's something to be said for a degree of ambiguity in bathroom scales). My best guess is that the “new” olive 250 (late 2000) is heavier than my “old” olive 250 (early 2000), maybe 1kg +/- 0.5kg. (Yes the scales are that knackered).
Anyway, I stuck the “new” 250 in to check it was working. It was. It was working rather better than my older one! The upper frequencies were presented "larger" than before, more in keeping with the scale of the rest of the frequency range from the speakers, much more detail in there and down through the midrange. Lower frequencies were no better, arguably even slightly less well controlled. Overall though it did a better (to my ears at least preferable) job of driving the DBLs than the slightly older 250. On opera especially, the sound was now totally beguiling, the detail of the individual voices, the scale of the performance, totally adsorbing, at last a viable substitute for the real thing.
Anyone aware of changes to the 250 (transformer) sometime in year 2000?
One Snaxo to rule them all……..
Asked my dealer to order me a Snaxo. Mentioned he knew someone with Briks who’d bought a 362 to replace his 36 and felt it wasn’t much of an improvement and might be willing to move it on. Could I be so lucky again? No. Couple of weeks of prevarication and he decided to stick with his 362. So a brand new Snaxo362 for DBLs was ordered and feedback from Naim was that it’d be built in December. Also mentioned I’d need some more NACA5….
Picked up the Snaxo on 22nd December. Logistical cockup on the speaker cable which wasn’t there yet. Took it home and decided to plug it in, warm it up, moving the Supercap that I’d been using temporarily on my Prefix.
Brief initial listen suggested that the Prefix wasn’t suffering that much through being only powered by the 52. More extensive listen identified that there is indeed a significant difference. Supercap powering the Prefix is, to my ears, significantly better than the 52. Don’t think it’s a lot more detail, more a case of the texture of the various elements of the music being more accurate, more realistic. In view of the price of a serviced olive Supercap I’m sorta tempted????Damn need another shelf.
Reeling in the New Year…..
Eventually the reel of NACA5 turned up along with the 4 speaker plugs. Borrowed the reel on the understanding I’d measure what I used and return the remainder. Dismantled the system, cleaned behind it (biohazard!), run in the cable off the reel to determine the length (2* 12m) and fired up my soldering iron.
What delightful stuff A5 is to work with! With assistance of Willy Jnr we removed the tweeter/mid boxes and the crossovers from the DBLs without moving them (very short right angle screwdriver). Laid all the cables in place, replaced the speaker upper boxes, built up the Fraim (52, Snaxo, 52PS, Supercap) and the “pseudofraim” (Lingo,250, 250,250). All cables neatly dressed though the snaxo/supercap Burndy is on bubble-wrap to keep off the floor. (Need to have a think going forward on rack. More Fraim (problem with old 250 outputs and rear post), or something else).
Fired it all up from cold and ……meh….
Ten minutes in started to detect what it was going to do. An hour in it was radically better. “smallness” of the upper frequency image was gone. Everything was at last perfectly in proportion. There was at this stage a “glare” over the sound, a compression if you like (elements of which still remain almost 2 weeks in but clearing by the day). However, through that I could hear that everything was better defined, more solid, almost as if you could reach out and touch it. Most importantly the various elements of any piece of music gelled better to convey the whole.
Sound improved slowly for 4 days before the first reversal. Monday morning (last week) and it sounded like the stylus was clogged with dust (cat, dog and lazy me it does occasionally happen). That stared to clear after about 24 hours. By the Friday it was kicking ass (I believe “Blimey” may be the appropriate term). Followed on Sunday by another reversal with subsequent incremental improvement. Back on an upward trend at the moment, better than ever and I expect (based on my previous experience of burn in) with several more cycles to go.
You’ll have likely figured from the foregoing that describing these differences is not my forte but here goes…It sounds real. It sounds natural. Individual elements within the music are more distinct without any loss in overall musical coherence, indeed it is just so damn coherent. No matter what I throw at them they simply get on with it, never any sign of stress, never any hint that they can’t do what is being asked of them. If you ever get the chance to hear a pair of active DBLs then go for it. Indeed, go out of your way to do so, they are a very special, very musical, very unloudspeakerish experience.
Willy.