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Impulse H2 full restoration - photos!

Pac1

Designer/Manufacturer
I've been asked to completely restore a pair of neglected Impulse H2s. Some of you may have seen this particular pair in action at this year's hifiWigwam show at Scalford.

This job consists of a full strip down, replacement of tweeters and mid units, extensive cabinet repairs, reveneering and recovering, an all new external bespoke crossover based on the standard H2 design but modified for the new Seas tweeter and replacement mid unit (a Seas H453 rubber roll surround version of the original. RFC have secured remaining NOS stocks of this driver for the sole purpose of refurbishment of tired Impulse loudspeakers).

An extensive refurbishment but one which I know the owner is keen to progress in order to conserve the existing pair to a very high standard.

Photos:

Existing cabs in pretty poor shape:

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Mid unit shot (oddly it has lots of sand embedded into the doped cone altering the moving mass so these can no longer be considered a closely matched pair as well as failed surrounds):

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Work started in stripping cabs down and reveneering side panels (bookmatched Oak, mirror matched between speakers):

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More to follow as job progresses.

If you have an old pair of Impulse speakers that you'd like to restore or upgrade, please PM me and we can have a friendly chat about what's involved. They're one of my favourite horn loaded speakers, and I specialise in their restoration along with Tannoy loudspeakers.
 
Thanks chaps.

A little more work now completed.

Both cabs reveneered now. Veneer is bookmatched using two sheets per panel for each panel, but also mirrored between speakers (ie inside faces use matching veneer to each other as do outside faces). I tried matching as closely as possible using consecutive veneer sheets.

I have also completed the new custom infill plugs for the tweeters to plug the larger hole left by the TD120K tweeter cut outs and skimmed the surface to get a perfectly flat surface for the tweeter flange plate to bolt up against. Hole is around 85mm diameter so will now take most modern tweeters. (There will be front cloth trim plus felt surround to tweeter to go into this busy little location too!).

Lots of fiddly little jobs really in their own right. For me, the most tricky part is yet to come with the re-upholstering of the cabinets and covers.

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Please note, I have yet to oil the cabs. Veneer is sanded smooth to 320 grit, just awaiting oiling at this stage.

My stocks of the remaining Seas H543 mid drivers arrived today so it was a chance to compare one with one of the jiggered H143 drivers removed from one of the H2s:

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I've tried them for fit and they're a perfect fit into the back of the mid horns. Some crossover tweaks will be necessary as the impedance curve and acoustic response are very slightly different from the 143, but sensitivity is about the same and their operating frequency bandwidth is also similar so they should be an excellent replacement and not a foam surround in sight ;)
 
Mid horns now both fully refurbished: These were in particularly bad shape. All of the joints had started to fail; the rather crude way the internal horn mouth was formed had cracked at the joints too and the sand loading from within the rear of the horn had escaped from all the gaps, hence the sand found in the drivers! All joints required epoxy filling, rear tape joint sealing was re-done, internal horn surfaces were cleaned and re-sprayed in gloss black and the cloth sides re-covered. All ship shape now:

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Whats the plan of action for the wood at the front?

looking boss so far

The originals were cloth covered so these will have new cloth fronts. Again, not the easiest of jobs as the cloth needs to be stretched around all sides, and cut outs made for the drive units. Should have all the recovering done by the end of the weekend. Attention then turns to refitting drivers, wiring, constructing external crossover boxes in ply (then Oak veneer to match the main cabs), plus measurement of raw drivers followed by simulation and design of new crossovers to suit replacement mid and tweeter units.
 
Might we enquire how much this full service costs?

Please bear in mind that this example isn't really a service, it's more a total ground up refurbishment of cabs, including book-matching of veneers and re-veneering, new coverings, fittings and fixings plus replacement mid driver units, tweeters, bespoke tweeter insert plugs, new bespoke external crossovers and rewiring.

I am happy to quote individually for bespoke refurb work. Every job tends to be slightly different as you may appreciate, hence costs are rarely always the same. Please feel free to PM me for an estimate (that goes for anyone else interested).

A few examples:

Replacing tweeters on say the H6 or Lali with the same tweeter conversion as these with the cabinet mods needed plus bespoke external redesigned (and much improved!) LR2 crossovers in custom boxes with new wiring etc would typically be around £750. That transforms the H6/Lali.

Internal crossover improvements plus replacement tweeters and servicing, budget less than half that amount.

The H2 example above would be twice that amount which is very reasonable given the large number of man hours and costs involved.
 
Some more progress:

Mid horns now completely restored, epoxy strengthened seams and several coats of new acrylic gloss black paint.

New mid drivers fitted and wired up with some Black Rhodium "Twirl" cable replacing the anchor rope AN cable which had destroyed the terminals on the original drivers. For those worried about using BR twisted cables for speaker internals, don't be. Bogus past rumours about capacitance are nonsense. The extra thick silicone rubber jacket spaces conductors such that capacitance is nominally just 90pF/m plus the cable is super flexible and will not over strain delicate terminals. It's ideal.

After 12 long hours today, both side/top frames have been re-covered, fronts were recovered yesterday.

Picture at the bottom is a "dry-fit" to check fit of frames to veneered sides. Fit is perfect. Frames also required restoration due to crush damage and a few chunks taken out of them!

James wanted to do most of the finishing to understandably save cash on the final bill, but I couldn't see these go out without proper finishing, so I will be doing this at no extra cost to James (I know you weren't expecting that James so it's hopefully a bonus for you :cool:).

Enough rambling: A few photos:

Recovered fronts (note new grille fixings):

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New mid driver all wired up ready for installation:

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New mid horn retaining screws...note existing horizontal holes originally drilled in the wrong place!! I have applied some very elastic (damping) adhesive to underside of rail mounts too:

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Mid driver installed and viewed from the front, it's a perfect fit. Note repainted and restored horn internals:

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Viewed from the back after mounting:

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Veneered side panels have received 4 coats of finishing oil. This shot shoes the dry-fitted re-covered side frames:

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More to come in due course.
 
Please bear in mind that this example isn't really a service, it's more a total ground up refurbishment of cabs, including book-matching of veneers and re-veneering, new coverings, fittings and fixings plus replacement mid driver units, tweeters, bespoke tweeter insert plugs, new bespoke external crossovers and rewiring.

I am happy to quote individually for bespoke refurb work. Every job tends to be slightly different as you may appreciate, hence costs are rarely always the same. Please feel free to PM me for an estimate (that goes for anyone else interested).

A few examples:

Replacing tweeters on say the H6 or Lali with the same tweeter conversion as these with the cabinet mods needed plus bespoke external redesigned (and much improved!) LR2 crossovers in custom boxes with new wiring etc would typically be around £750. That transforms the H6/Lali.

Internal crossover improvements plus replacement tweeters and servicing, budget less than half that amount.

The H2 example above would be twice that amount which is very reasonable given the large number of man hours and costs involved.

I wasn't enquiring for me directly, just more interested in a general level. FWIW I think those prices are very reasonable. Will you have a go at most vintage speakers?

Stefan
 
I wasn't enquiring for me directly, just more interested in a general level. FWIW I think those prices are very reasonable. Will you have a go at most vintage speakers?

Stefan

Hi Stefan

yes; I'll tackle most speakers as the facilities and databases I have are quite extensive. I have full measurement and computer simulation kit too so have the facilities and know how to scratch design custom crossovers as a one off for most speakers. The only ones I don't tend to be involved with are electrostatics which are more specialised.

To date, speakers refurbished include vintage Tannoys, JBLs, Heybrook HB1/2/3's, B&W DM series; Impulse Lali/H6/H2; Roksan Darius; KEF REference series, Yamahas, Radfords, Missions and many more.

I also specialise in fixed inductor circuits for vintage Tannoy crossovers plus have bespoke designs available (price £240) for RFC designed DIY Tannoy cabinets and also undertake custom loudspeaker design and construction based on customer's preferences and listening rooms.
 
Great, got a couple of ideas i need to run past you in that case. I'll PM you in a couple of weeks time when I have got a bit further with the idea but we maybe able to help each other out.

Stefan
 
Great, got a couple of ideas i need to run past you in that case. I'll PM you in a couple of weeks time when I have got a bit further with the idea but we maybe able to help each other out.

Stefan

No problem Stefan. I'd be glad to help out if I can, so by all means drop me a Pm when you've settled what you'd like done.
 


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