Grundig 5040W/3D loudspeaker.

[sabaman]

Hello,

The up-market Grundig 5040W/3D's 'main' loudspeaker appears to have an unusual design & mounting arrangement. It's also large for a domestic radio, about 35 cm across.
There is a cut-out in each 'corner' of the paper cone. There is also an approximate 5mm gap between the loudspeaker frame and the wooden baffle, the gap due to rubber grommets on each of the four securing screws.
I don't remember having seen this arrangement before.
Would anyone be kind enough to shed a little light on what's going on here?

Many thanks,

S.

[Rich Woods]

Suspended virtual baffle or something similar to make the cabinet sound larger?

[Herald1360]

Maybe it reduces "boominess" from enclosure resonance?

[m0cemdave]

It will certainly have some effect on the bass (or low-mid) performance of the speaker. I presume the radio cabinet is not sealed, but it will act like an extra port.

[vidjoman]

Have you taken it off the baffle ? It may have a damaged cone. In a 3028 with a similar speaker, it has thick foam around the edge between the speaker and baffle and is mounted like yours with rubber grommets and a metal insert to avoid crushing the grommets too much.

[Edward Huggins]

I think the surround looks fractured. Can we see it off the baffle?

[ms660]

The four cut outs can be seen in this link (scroll down to LOUDSPEAKERS and look through the photo's):

https://luxuryradios.com/en/grundig-5040w-3d-en/

Lawrence.

[vidjoman]

Yes, I see the cut out sections but it still has a foam edge to the speaker that seals it to the baffle

[Radio Wrangler]

It may be some attempt at damping cone breakup modes.

David

[Mr 1936]

Hi

Looking at the picture on the referenced site, I also notice that the edges of the 4 apertures in the cone are doped with some sort of material, and the centre of the cone has a little vertical cross brace. This all suggests to me that the Grundig engineers had the ability to analyse cone resonances and treat them.

My best guess (as others have suggested) is that the corner cutouts form a controlled port, which is most likely a way of reducing a resonanant peak in the bass region.

The OP's example seems to have lost its foam edge seal, not surprising given the limited life of that type of material. The rubber grommets on the support fixings are probably hardened by now as well.

[simpsons]

Any chance of a photo showing the front of the speaker?

European radio manufacturers Grundig, Saba, Telefunken, Philips and so on had a large market for high quality receivers and their engineers went to great lengths to excel in their chosen field.

It may well be that the open edge of the cone is open but to stop the cone edge from being torn when executing bass notes at high volume, there must be a mechanical suspension from the loudspeaker frame to the cone. Just how was this done?

The ingenuity used by Grundig to create "The Grundig Sound" has been the topic on many threads, let's hope an engineer can throw some light on the design concept the 5040 loudspeaker has.

Chris

[sabaman]

Hello all,

Please excuse my brief reply on this occasion, I'm a but pushed for time today.
I'm most grateful for everyone's interest & input. I've just had time to remove the baffle from the speaker and take a couple of extra photos - hope this helps. Thanks again - your responses are most interesting.

S.

[Herald1360]

So..... it looks like just some new foam is required to restore the speaker mounting to "as new". (And maybe grommets too if they've gone hard.)

[stevehertz]

I reckon that the designer's thinking was that the corners of that 'square' cone would form a stiff assembly and hence limit the amount of travel ie the amount of bass produced by the driver. Hence, cut away the corners and allow the cone to move more freely. That's my theory anyway.

[marceljack]

Originally Posted by stevehertz

I reckon that the designer's thinking was that the corners of that 'square' cone would form a stiff assembly and hence limit the amount of travel ie the amount of bass produced by the driver. Hence, cut away the corners and allow the cone to move more freely. That's my theory anyway.

I think you are right.

[roffe]

http://www.hifimuseum.de/ls-philosophien-1953.html

[marceljack]

Originally Posted by roffe

http://www.hifimuseum.de/ls-philosophien-1953.html

If I understand right this article the loudspeaker casing is not metallic but painted plastic ?
And the purpose of cutting the corners of the membrane would be to reduce the bass response by means of a partial acoustic short circuit ...

[stevehertz]

Out of interest I have the same huge Grundig 5080 set. I've owned it for around nine years and apart from a scrub up have not ventured into a full restoration knowing what a big job it's going to be having restored the smaller 3028 some years ago. They are quite rare, I've only ever seen the one I bought on eBay in all that time. Should sound really good fully restored with its twin EL84 output.

[roffe]

Yes,they are made of plastic(of some sort).Just look how many reinforcements there are on these loudspeakers as opposed to standard metal ones.
And easy to check with a magnet.
Scroll down to the bottom here:
http://www.hifimuseum.de/1953-hausmitteilungen-9.html

[vidjoman]

A magnet won't detect the cast metal as it's probably an aluminium alloy which is non magnetic - it won't be steel. Try tapping the chassis with a metal object - a screwdriver for instance, and listen to the sound. Metal will ring but most plastics will just give a dull sound.