Goodmans Magnum k Refurb and modification (part 1)

[Dr Bunsen Honeydew]

Attenuators.

Find the position you think gives best balance - measure across the pot to find resistance value - replace with 5 or 7 watt wirewound resistor to that value or nearest. Disconnect and remove the earth lead that went to the pot, as you will no longer need to dump voltage.

[Ronin]

Thanks for the advice/instructions doc.I will give it a go and report back.

[Tim Catt]

agree with doc,treble is brighter with stuffing removed from my Ks,would it have anything to do with the cabinet construction.I see mine are different,I think the pair that you've got are chipwood were mine are plywood ?

Interesting to know that someone else has these beauties and are willing to share their experiences I've been living with mine without the stuffing for a while now,I may take the plunge and steel line them next and also re-wire them( I'll share my finding when I do).For the crossover I've changed the wire to DNM.

What I would love to do is to completely remove the adjustable pots, I really feel they are detrimental to the sound quality.

The big plus for me is the speed and accuracy from these speakers ,bass is so good even with my suspended belt drive turntable ( Direct drive is even better) Violin s & Cellos sound so much more lifelike than my previous Mordaunt shorts .

All the best with your project

Nice one Ronin, I'm glad we share the same enthusiasm for this wonderful speaker that for the best part is outrageously underrated! And to have only paid £10 for mine! Very happy indeed..

I agree regarding violins and Cellos and I would go as far to say the same for any well recorded srting instrument and the Magnum k's especially after the steel plates were fitted. Also well recorded vocals are to die for. Bill Callahan's 'Dream River' is beautifully crafted and sounds like it was written for the K's. Bass is good as you say, but I feel they roll off very quickly at around 50hz so you loose that lovely sub 50hz warmth at low listening levels. I've rectified this by adding a Tannoy 12" active sub (I have a relatively big living room). After spending quite a bit of time delicately blending the sub woofer and the K's crossovers I have to say I've unlocked a whole new world of listening pleasure! I feel sometimes that snares and symbols lack a little life-like snap but you can't have everything and I always look forward to a bit of quality time with my beloved Magnum K's!

I digress, Shit attenuators are on my hit list and they will probably be gone this weekend. The mid range l-pad on my right speaker has a nasty crackle and can even cut in and out when fully open. They are glued on the inside of the speaker and every now and then when the volume is loud enough it can vibrate the attenuator into the range that has deteriorated. At first I thought I'd shafted the voice coil on the mid driver. Luckily this was not the case!

[Tim Catt]

Attenuators.

Find the position you think gives best balance - measure across the pot to find resistance value - replace with 5 or 7 watt wirewound resistor to that value or nearest. Disconnect and remove the earth lead that went to the pot, as you will no longer need to dump voltage.

also thanks from me regarding this Doc as I did wonder. Always better to go at a job with some clear instructions... Legend! :D

[jammy395]

Tim - Projects are a Nightmare, But I love this thread...Keep at it, You will reap reward's .......

[Tim Catt]

Cheers Jammy, I've really enjoyed this project as ive learnt so much about the basics but unfortunately Im a bit stuck with theremoval of the l-pads. I know that doc has explained this process but Im still baffled. On the l-p it says 15ohm. Im I right in thinking this would be the value of the lpad resistance when fully open if so would this be the value of the required resistor? And I really dont know which wires need to be bridged by the resistor when its fitted. Seem like they're are shit loads of wires going to one terminal of the l-pad which include the negative wire from the mid range, then the postive wire frim the mid goes to the middle terminal of the l-pad and then there is an inductor wired to a third terminal on the lpad. I will whole heartidly appreciate anyone who has the patients to help with this.

[Dr Bunsen Honeydew]

OK in that case it gets a little more complicated. Set the attenuator pot at the point where you like the music. Measure between the middle terminal and the left one and between the middle terminal and the right one. Get resistors (5 or 7w wirewound) of those two values and join them together in the same sequence as you measured, and connect them up the same as the pot - the wires on the left term to left end of resistor pair - wires that went to the middle term connect to the junction between the two resistors and wires from the right term to the right end of the resistor pair and you will have copied what the circuit was doing at that point on the rotation of the pot.

[Tim Catt]

Thanks Doc, There is no way I would have figured that out by myself and you've made it seem so simple! I just need a little more clarification on the measureing aspect i.e do I measure the value between the terminals while the l-pad is in situe and while it is recieving a current or do I set it to the required value and then remove it from xover and then measure it or none of the above?

[Dr Bunsen Honeydew]

Just measure ohms across the terminals with the wires disconnected.

[Tim Catt]

That's great. Thanks again! Just of curiosity aka blatant noseyness... where did your journey into audio engineering begin Doc?