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I had one of these small E.M.G Mk. 4 Grams up until recently & took the opportunity to draw out the internal horn in it's entirety. The plan is to re-create the horn in proper Papier-Mache using the same volume that the Mk.4 Horn has but with a slight alteration at the point where the beginning of the bend up towards the bell occurs in order to make a type with the same internal dimensions top to bottom but designed to retro-fit an H.M.V 156 (for example) where the benefit of an exponentially tapered tone arm is already present & in also situated conveniently in the rear corner allowing a connecting tube to link up with the beginning of the new Paper-mache horn, centrally placed in a 156 cabinet. This is neccessary as the base of the E.M.G tone arm with it's Quink tube has a diameter that is 8mm larger than the HMV 156 tonearm to connect to the beginning of the Horn itself, therefore in order to keep to the maths of the Exponential amplifier system the 8mm difference needs a mating exponential conduit to use with a copy of the E.M.G Paper horn to make up the difference.
The images show the raw 3D print , printed slightly smaller & built up from many small sections. After this was complete the Horn template was glued & then split into 2 main sections to make Horn production simplified. Most of a 3 litre can of car body filler was then used to correct the template by hand (which represents the internal Horn surface) it also gives a mirror smooth finish that the stranded 3D print does not allow. Here are some pics that show the roughly taped together 3D print that was built to test fit in a Cabinet before the lay-up of filler was started. hope this is of interest.

Finished Horn master ready to start papier-mache horn construction

But the hmv156 had an original exponential sound system, isn't it? It's from the 'Listen to the bass' era, the first exponential sound systems with narrow bore swan neck tonearm, within the 101-103-109-126-156-161-181-201 model series, later adding the transformed Lumiere models 461-511.

Inigo wrote: Sat Jul 26, 2025 8:07 am But the hmv156 had an original exponential sound system, isn't it? It's from the 'Listen to the bass' era, the first exponential sound systems with narrow bore swan neck tonearm, within the 101-103-109-126-156-161-181-201 model series, later adding the transformed Lumiere models 461-511.

Yes, it does, you're absolutely correct, and it is bigger and better than the EMG Mk 4 although still notably smaller than 511, 162, 192, 201 etc

Hi, that's correct , however, Percy Wilson stated that A Horn construction of tin & wood ...for example , adds unwanted frequency to any recordings played through it ,According to Wilson, Papier-mache adds nothing, like a modern speaker cloth it's acoustically transparent . That's the concept here, will see if it's correct when the paper horn is made & installed with before & after like-for-like videos of it playing the same record, with the same soundbox, & the same fibre needle.

Large HMV tin horns resonate in the mid bass region, I suppose it depends on the size of the panels

The Papier-Mache test horn is ready & now in a 1926 U-Phone cabinet, video to follow. this is the paper horn with a top mounted 3D printed P.L.A conduit that stretches the HMV Swan neck tonearm exit to horn end to the same inside Diameter as the EMG Quinke tube type. The point of the sewn leather sleeve that holds these 2 components together is to allow some flexibilty of fit when coaxing it into a Cabinet while retaining an air tight seal.
The tone of the paper horn is a monster improvement.

Here is the video of it playing with a No. 4 HMV soundbox with steel needle
https://www.youtube.com/watch?v=A5LQpFWboCo


photos of the horn in the cabinet

It sounds wonderfully!
Now I'd suggest to try on it an hmv no5a or b soundbox; no other change to the sound system except the 5a/b and a correct rubber connector to fit the soundbox on the narrow tonearm. The same hmv no4 connector serves, as it fits perfectly the backplate neck of the 5a/b, which was of same diameter.