Goodmans Magnum k Refurb and modification (part 1)

[Tim Catt]

This is my first diy speaker project and I have found a wealth of useful information on this forum and I'm looking forward to sharing this experience and the exchange of knowledge and banter that goes with it. My intentions are to compliment existing posts regarding the Goodmans Magnum k's and therfore I will not be giving a general overview or looking at specs. I will start by writing a brief list of jobs for my Magnum k's. To keep it simple I have split the jobs into 2 sections comprising of completed and proposed. They are as follows:

Completed

1, Steel plate damping has been applied to 1 speaker. This would have been applied to both at the same time, however my first school boy error was to order the plate in the wrong size so what would have gone in 2 speakeres went in one. Even though this was a wee set back it has had some positives I.e I have had over a week to reflect on the audiable differences between steel and convetional damping albiet accross one pair as apposed to a-b reference of 2 pairs and every time I pick up the lighter of the 2 I realise how solid its 30 kg counterpart is!

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2, Replacing the perished foam from the centre of the tweeters. This is neither here nore there but it had litteraly turned to dust. I also ripped one of the tweeters slightley which required glueing. Unfortunately my second school boy error was to use super glue and I later disovered a neat way to use pva and tissue. Still it has had no
impact on sound and is a great visual reminder for me not to rush!

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3, Sanding off the nasty old scratched varnish, filling some gaps and nicks and building some solid wood speaker stands.

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Proposed work

1, Fitting the second speaker with steel plates

2, Replace Capacitors. These have been ordered from Falcon Acoustics and should be with me by Monday. This is an experiment for me and an opportunity to practice soldering. I will give my opinions on this upgrade when it is complete and this will be included in part 2.

3, Removing pots/adjustable l-pads and replacing with 4mm binding post. I already have these and will be fitted at the same time as carrying out the above action.

4, Replacing some of the old wiring in the xover. Any advice regarding this will be very welcome. I will say though I'm on a very tight budget and thoroughly enjoy recycling.

5, Last but not least I will be treating the vaneer on the speakers and the speaker stands.

The above proposed tasks will be documented within the next few weeks in part 2 of this thread.

[Dr Bunsen Honeydew]

Good stuff! I look forward too it.

[Tim Catt]

Hey Doc, can steel damping considerabley reduce the overall volume of a speaker?

[Dr Bunsen Honeydew]

No, and steel plate is not damping. Damping is a mechanical filter, steel plate is about cabinet rigidity, so mass damping is not an expression I would use. Quite simply steel plate (and the more of it the better) stops the cabinet storing energy and talking.

Initially you will think less bass, but it is real bass that is left and not bloat and you will need to push the speaker further back to the wall.

[Tim Catt]

Makes sense. As per my thread above having one speaker with steel plates fitted has allowed me to really get a feel for real bass and bloat and it does definitely sound better however the speaker I have fitted steel in is noticeably quieter across all frequencies and ive refrenced across several recordings. No drivers have blown either. Is it possibly an issue with capacitors?

[jammy395]

Hey Doc, can steel damping considerabley reduce the overall volume of a speaker?

No, (Part Quote Doc)

Not considerably, But yes, (Jammy).

[Dr Bunsen Honeydew]

Makes sense. As per my thread above having one speaker with steel plates fitted has allowed me to really get a feel for real bass and bloat and it does definitely sound better however the speaker I have fitted steel in is noticeably quieter across all frequencies and ive refrenced across several recordings. No drivers have blown either. Is it possibly an issue with capacitors?

Well stick yer ear to each driver you can soon tell if they are working. Bloat and cabinet talk contributed much to the output, so now it will be more accurate and yes quieter. I doubt it is a crossover problem, better caps will just give better music.

[Dr Bunsen Honeydew]

Hey Doc, can steel damping considerabley reduce the overall volume of a speaker?

No, (Part Quote Doc)

Not considerably, But yes, (Jammy).

Not so Jammy, if all the wool and other crap has been removed it probably has more volume.

[Tim Catt]

Cheers for the input chaps! Ive removed all other damping material which was foam. Is it possible that the flat(er) frequency response of the steel mod speaker just seems less bright compared to its less rigid counterpart and therefore giving an illusion of less volume when panning left to right?

[Dr Bunsen Honeydew]

Should have caused the opposite, an increase in treble. Check the tweeter is working, they fail pretty often on this model.