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Impulse H2 full restoration - photos!

I have owned from new, a pair of H2s. Visually they appear as mint condition but the drivers have detiorated.

I have replaced the surrounds on the bass units, which went smoothly.

Next up is the mid range drivers. Looking at them the surrounds have some cracks. As far as I can establish the orginal driver (Seas 11F-M) and the later replacement recommendation (SEAS MCA1) are no longer available but I can get a pair of foam surrounds for the orginal driver for about £13. ( https://speakerrepairshop.nl/en/foa...ng-4-inch-for-seas-11f-m-unit/a-4907-10000028 )

So the first questions are around, the mid range drive units:

  • is there any suitable drop in replacment driver available these days.? make cost etc

  • would a recone give me a pretty close match to the orginal. if so any benefit in painting the surround with a light coating of diluted glue to approximate the dopping.
The second question is about removing the mid range drive units from the cabinets
I cannot see how the mid range drivers come out of the cabinet. I can see they are screwed to the outside back plate of the horn module and wired with Vecture CV30 solid core but I cant see how to remove the horn module.

My best guess is that it is held in place by some screws that are accessed by renoving the tweeter or bass unit and that after removing this it slides out forwards. It looks to be a tight fit though.

Any advice, hints, tips on mid range driver removal

Many thanks in anticipation

Ian
 
The horns in my pair just sat in the enclosure, I could lift them out.

Yours may be stuck in with Blu Tak or similar, try giving them a good wiggle.

If not, I’d try either removing the tweeters, or mine had a plate at the rear with the terminals on that could be unscrewed.
 
Will try removing the tweeters, nothing obvious holding the horn unit or the fabric covers in place. I am sure it's an easy removal when you know how.
Many thanks
 
Not on all H2s it does not.

There are many, my pair included, where the fabric wraps the whole, over the top.

In these generally the Mid horn is a sub-assembly that is fitted from the front, and once you remove the bass driver, check if there is fixing or two up from underneath you need to free, then withdraw the assembly forward.

Basically - given the perceived expense at the time most H2s appear to have been made to order, and while the design /xover/driver complement is standardised, the assembly was not, depending on finish requests - there are 2 or three basic variants, and handful of real 'customs' out there.

Since this starts on my pages on Impulse loudspeakers, I've some notes from other gathered over the years and happy to share.

BTW the speakerrepair.nl shop are excellent to deal with, and teh products I bought, first-rate. I bought some sets of bass driver surrounds from them, fixed another pfmer's pair of H2s - you can find that described in the links above - and those are still perfect 6-7yrs later. I have a couple of spare pairs of bass driver surrounds left over, really ought to do my own soon...
 
The covers on my speakers appear to be on a one piece frame that goes down both sides and over the top. No obvious indications on how it is fitted or removed. I used speakerrepairs' surrounds and Martin's most useful guidance notes to fix the bass units.

I will order some surrounds for the mids and have a look inside the cabinets see if I can see any fixings

thanks for the pointers Martin.
 
Tried to get the woofer out but its stuck solid, removing it when the surround was rotten was far easier. Thinking i could push it out from the rear via the tweeter hole, I took the tweeter out. Again not too east because it too is a tight fit. Can now see inside the cabinet. Looks to be Audionote cable to the tweeter.

No sign of anything that might be holding the hold assemby in place. The top of the cabinet below the horn assemby looks to be a solid with nothing going through it.

Peering into the rear of the cabinet through the holes behind the mid range driver, the horn assemby looks as if it locates into a vertical channel cut into the main cabinet on each side. No obvious way to get the horn assemby out.

Could it be that the whole of the fabric cover has to come off, the mid range is then unscrewed from the rear and lifted out of the top? sounds possible but that raises the question how do I remove the fabric cover assemby.

Closer look from the rear, the horn unit looks as if it should slide in/out along the cutout in the sides of the cabinet but pushing it from the rear with a pole, wigging from the front doesnt seem to move it. I dont wont to use too much force until I know the best sequence. so for example there are cloth covered inserts at the front of the horn on each side - do these need to be pulled out first - they are a very tight fit
 
Many thanks to Paul at Reference Fidelity Components for his advice and guidance (via his web site). The mid range unit drifted out with ease using a piece of soft wood as a spacer and a hammer. Glue is drying on the drivers as I write
 
All back together now, the most challenging part of the whole process was getting the old cable off the drive units, twisted and soldered a right pain. Then finding some thing the hold the surround in place whilst the glue set. In the end I settled on an old mini cd and a plastic fresh soup pot with some weights on top of each. Clothes pegs were too big.

Sound wise it's a little smoother, less agressive top end and a tad more detail.

My thoughts would be that all impulse speaker owners should check their drive units and any signs that the surrounds are on the way out on the bass and mids should replace the surrounds on both. It's a little fiddly and messy but not difficult.
 
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