Lowther Hegerman Reproducer

[Tsingtao_1903]

So, I stumbled across the Lowther Hegerman Reproducer while doing the deep dive on the Voigt Domestic Corner Horn. Only 30 - 40 units were ever made. So, it's the rarest of the rare. It's front loaded via the W horn at the top and back loaded with the bass chamber at the bottom. The speaker itself is huge. 4 ft wide, 2 ft deep and 4 ft tall.







I of course just had to look into it....

It turned out that Lowther actually did not build the cabinets themselves because of the difficulty in transporting such large cabinets. So, they only allow dealers with access to top notch woodworking shops and send them the build plans.

Armed with the knowledge that such build plans exist, I spent some time to do some internet sleuthing. Came across a posting that led me to another posting and then to an eBay ID.... Contacted the gentleman. He could not have been nicer. He generously sent me the cut sheets to which I am very thankful (Thanks so much @donroth). There was no drawing for the plaster of paris W horn. I suspect it came from Lowther, not the local dealers.




Yippee. Another project to add to the hopper!

 

[MrEd]

That is ambitious for sure.
The photos are beautiful.
How do you propose to figure out the w horn?

 

[Tsingtao_1903]

How do you propose to figure out the w horn?

Great question. As with the VDCH, start out with the best pictures gathered on the web. Import the pictures into SolidWorks and scale the pictures to a known dimension - say the width of the horn. The width of the horn can be calculated from the interior dimension of the top cabinet. The throat dimension can be estimated from the Lowther PM4 that was paired with this horn. The expansion is likely to be tractrix.... Anyway, it will take a bit of voodoo to get the W horn shape. But, I think it can be done. Also, I will likely make the horn from cut stacked plywood instead of plaster.

First approximation of the W horn using a scaled picture and other known dimensions.

 

[marantzfan]

I saw where someone had restored a set of these recently. I think it was on facebook.

Edit: Yes, a Facebook group. Can’t share a link since it’s a group but here is a screenshot.

 

[Tsingtao_1903]

Thanks for sharing the pictures. I've only just received the plans. Just a quick glance through, they do not look anywhere near as complicated as the VDCH. The back loaded section appears to be some kind of Voigt pipe. Still need to model up from the plans and do the math.

 

[marantzfan]

Thanks for sharing the pictures. I've only just received the plans. Just a quick glance through, they do not look anywhere near as complicated as the VDCH. The back loaded section appears to be some kind of Voigt pipe. Still need to model up from the plans and do the math.

You should join that group if you aren’t already in it. There are lots of pictures he posted throughout the restoration.

 

[ChrisAZ]

Very cool project. Those are some great looking speakers.

 

[old_borg]

Great question. As with the VDCH, start out with the best pictures gathered on the web. Import the pictures into SolidWorks and scale the pictures to a known dimension - say the width of the horn. The width of the horn can be calculated from the interior dimension of the top cabinet. The throat dimension can be estimated from the Lowther PM4 that was paired with this horn. The expansion is likely to be tractrix.... Anyway, it will take a bit of voodoo to get the W horn shape. But, I think it can be done. Also, I will likely make the horn from cut stacked plywood instead of plaster.

First approximation of the W horn using a scaled picture and other known dimensions.
View attachment 27483

Couldn't you also scale off the Lowther driver - or is that a dimension that isn't too easy to come across?

 

[Tsingtao_1903]

Couldn't you also scale off the Lowther driver

I have the dimensions for the Lowther driver. Yes, they will also be used as inputs for reconstructing the W horn.

 

[rogerfederer]

I have the dimensions for the Lowther driver. Yes, they will also be used as inputs for reconstructing the W horn.

you are a wizard; i always look forward to following your adventures! don't forget to finish the telefunken OBs; consider me in line to get a flat pack if you ever make any

 

[Tsingtao_1903]

You are number two in line for the OB's. Just taking a break from all that saw dust at the moment. Need to solve the mysteries of the Lowther Hegerman Reproducer just to get them out of my head (not much room in there).

 

[Tsingtao_1903]

Took a bit of work. But, I was able to model up the back loaded cabinet from the plans and see the construction of the various folds. So, sound waves travel down, back, split into two, diagonally down, over to the center, combine, toward the front, split, 180 going toward the back, 90 to the sides and back out to the front. There is also an expansion as things move along. Wow!!!

 

[donroth]

Incredible! Keep us posted. (Thanks for calling me a gentleman.)

 

[Thermionics]

 

[Tsingtao_1903]

Rough modeled the w horn. Will have to do some calculations later to check the expansion. I suspect a combination of Tractrix curves similar to the VDCH.


Finished out the top.

 

[Tsingtao_1903]

So, I spent quite a bit of time trying to model the W horn without any success. The external dimensions of the horn can be roughly estimated from various pictures found on the web. All my attempts at using various expansion models failed to fit the external dimensions of the horn and the opening for the Lowther PM4 driver.

Came across the picture below of the horn throat yesterday. The opening is rectangular - similar to the horn throat of the VDCH, Aha!


Cross section view of the latest model.


The external dimensions should be very close to the real horn. The internal expansion is correct. I am happy.

 

[pelanj]

These threads are so much fun to read, impressive!

 

[Drugolf]

Amazing, all that for that single 8" driver.
Anybody here ever hear these?

You going to build those cabinets Tsingtao?

 

[Tsingtao_1903]

I want to. Sadly, I do not have the space for such a beast once built.

 

[pelanj]

The width is 110 cm if I calculated correctly. That is even larger than the Danish 3 way Jealvox. Larger than my bass horns, too. True monsters