JPW ML710

[Dr Bunsen Honeydew]

Personally I wouldn't have removed the dustcaps. The reason Joe did it was to inject ferrofluid in the voicecoil gap and as everyone who owns Royds knows that is the source of the only problem with muck getting into that gap. Also you make it harder to dope the inner edge of the cone as you don't have the groove between the dust cap and cone to act as a natural doping point. It is that edge that is the source of HF propagation hence the doping should be thickest there.

[istari_knight]

Yeah I thought long and hard about it [well 10 mins] AFAIK the presence of a dustcap increases output at the top of the drivers range so removing them will definitely be beneficial in this particular scenario... Less for the doping to do ! Applying the doping will definitely be more difficult without them but I like a challenge.

Not saying you're wrong on the Royd/ferrofluid but I've taken a quite a few apart and I'm yet to find one with any ferrofluid in the voice coil gap, its always doping compound that's leaked into it from being in direct sunlight or something... Royd bought in tweeters that contained ferrofluid and part of the modification process was to remove it, maybe he recycled it

[Dr Bunsen Honeydew]

I saw him doing it at the factory, using a hypo containing ferrofluid. So I presumed he always did it. I have a driver here from a Minstral and I am pretty sure that has ferrofluid. It is quite hard to detect. It is that ferrofluid that interacts with the doping, diluting it which allows it to dribble into the voice coil gap which makes the ferrofluid harden and go sticky.

[istari_knight]

Ferrofluid is horrible stuff isn't it ? Gets bloody everywhere like thermal compound ! Its completely dried up in many speakers from the late 80's to early 90's... I've had a couple with blown tweeters as the power handling is so greatly reduced not to mention the change in sound. You can buy it in tubes from the US to replace the old gunked up stuff, I did it on a pair of KEF 103/4... The sound was much improved afterwards but in hindsight I would have left it at removing the old & not bothered putting new in.

[Dr Bunsen Honeydew]

Perhaps I ought to explain where my knowledge comes from. I got talking to Joe in the early 90's due to a letter I wrote in Inside Hi-Fi a trade magazine. He felt the same way about the industry as I did. I also liked his speakers. Sometimes my distributors asked me to recommend speakers for them to sell to go with NVA and I always recommended Royd as he needed it and deserved it, as he didn't have large export penetration. I gave him distributors in China, Taiwan and Italy, which he was obviously grateful for. And when the Taiwan and the Italian distributors came to the UK to visit they came to me first and then I drove them up to the Royd factory. So had the production and design tour twice, plus some private time with Joe where he showed me things especially about drive unit testing and doping.

[Dr Bunsen Honeydew]

Regarding dustcaps I forgot to mention it but I thickly dope all over the dustcap.

[Alfi]

I took your advice Doc. Doped over the dustcaps on my AP2's twice

Alfi.

[AshM750.]

I took your advice Doc. Doped over the dustcaps on my AP2's twice

Alfi.

Do you layer it on then ? or is it just one heavy coat all over the driver ?

Thanks in advance

[Dr Bunsen Honeydew]

Depends, because I use a spray can I use layers. Stari has a can of similar gloop he can brush on.

[AshM750.]

Depends, because I use a spray can I use layers. Stari has a can of similar gloop he can brush on.

ok ile try get some brush on or spray ive seen the links. with the spray do you mask off the foam surround ? Does it work with KEVLAR drivers ?