JPW AP2

[Alfi]

I've recently purchased and early pair of these large stand mounters in order to restore and play with them. The 8" drivers needed re-foaming which I have succeeded in doing apparently successfully - they are playing away very nicely as I write this. I also took the opportunity to replace the BP electrolytic with an MKP film cap.

Question is : - is there anymore to do in order to eek more from them (if possible) in order to enjoy them more than I am now?
I'm using NVA LS3 cables presently.

Thanks

Alfi.

[Dr Bunsen Honeydew]

Take all the foam and wadding out and throw it away. Then for further improvement line the inside of the cabinet with 5mm steel plate

Finally we can talk about doping the bass drive unit so you can throw away the crossover components attached to it.

[Alfi]

Thanks Doc.

Has anyone else on the forum undertaken the mods you propose I wonder. If 5mm plate lining is going to improve these babies that will not be a problem for me, but I do wonder how best to affix it ? My AP2's only have BAF wading (no foam) but the panels have quite thick strips of bituminous compound applied to approx 50% of the panel area.

What would you advise I use to dope the paper cone ?

Once this is done, you advocate removing the inductor to the bass driver ?


Alfi

[Dr Bunsen Honeydew]

Step by step, take out BAF and listen.

[Daniel Quinn]

I have undertaken some of the mods and more with my jpw ap2. You can read it in the thread my hi Fi is a disaster towards the end.apologises .Currently on my phone so I can't do a link.

[Alfi]

OK Gents - thank you both, I will do and report back in time.

Alfi

[floydfan]

Hi Alfi

I have worked on three sets of speakers using the Doc's mods; steel lining, removing crossover to bass driver, rewiring and doping bass with Plasti dip. I tried the system out on a pair of Sony music centre speakers, as a trial, and was so impressed I then carried out the work on JPW ML510i speakers and on Goodmans Dimension 8 speakers.
The only tricky bit was using my ear to decide when I had doped the bass driver enough. There are a few threads on steel lining speakers in the DIY section where you can get more detail.
I thought the mods made a huge difference to the sound quality on the cheap/old speakers I have so much so that my KEF Iq5s are residing in their boxes.

[fatmarley]

After those mods it sounds like you'll end up with a large pair of Royds (That's a good thing)

[Dr Bunsen Honeydew]

Sort of. But Joe always used some sort of crossover on the bass driver, he used doping to simplify it and to match drivers. Now a'days the matching is less important because I can buy matched drivers for NVA, but I still put less importance on that than Joe did, for me I take it a stage further to eliminate the crossover. Also he only used plating in some of his speakers and always used some wadding. AFAIK I am the only loudspeaker designer advocating these speaker mods. I use them myself in my designs but obviously they are new speakers so they cost! but the principles are applicable to a lot speakers out there that are not voiced by their construction i.e. BBC designs, as I would never apply these mods to them, they would cock up even more something that is already musically cocked-up Simple USA or USA based designs (as the JPWs) really benefit, as do pre BBC bullshit designs from the old traditional British companies like pre 1975 Goodmans, Wharfdale and Celestion speakers.

[fatmarley]

I know he ran the Royd Minstrel midbass driver direct because I've had them apart but I don't know about the other Royd models. There is also a steel plate on the back panel and wadding at the top and bottom of the cabinets.

It's a very clever design IMO and could be made even better with a polyprop cap on the tweeter and some extra resistance to bring the tweeter level down a bit.