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reQuest rebuild HELP, please

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ksrigg

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I have bought some old reQuest panels, bass drivers, and crossovers from a pair of reQuest spekers and plan on building my own MLreQuest variants from the various parts. My plans include replacing the woofers with some Lambda Acoustic 12" subs I have on hand and using a 250 watt plate amp (or larger), bypassing the ML crossover for the woffer section. I wnat to do a ported box about 3.5 cu. ft in size tuned to 25 hz. I need to resolder the panels as the connecting wires have come off the front and back. I have tried to resolder with no luck. I can't get the solder to stick. Anyone have any ideas, flux perhaps??? I am going to have to completely build cabinets and everything, and have a pair of SL3's to use as a guide, but any help or ideas would be greatly appreciated. Thanks very much..

Sutton Rigg
 

JonFo

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Sutton,

Ambitious approach, should be fun :)

I assume when you say you have the crossover that you also have the whole ESL step up assembly (printed circuit board + big Transformer) as well, correct?

Can you please post a link to the Lambda specs, I’d like to see how clean and how high it goes. You might find a better approach is to get a nice 10” driver for the new L/R speakers you’re building and use the Lambda for a pure sub (crossover <100hz).

Especially if using older request panels, getting some decent mid-bass will require a 10” driver that is clean up to 500Hz. I would look for one that goes clean to 800Hz and cross over at around 400 using a fourth-order LR active w/EQ. On the other side, cross over at 60 to 80hz.

Those old panels will also likely have some serious high-end roll-off above 2.1Khz. So compensate in the analog crossover or better, use an outboard active.

Soldering the leads to the stator and diaphragm is what you are having an issue with, correct?

The stator should be the easier of the two, but still tricky; as getting the solder spot hot enough (that big stator makes a nice heat-sink) will require a very hot soldering gun. Pencils need not apply.
What soldering rig are you using?

Soldering to the diaphragm is new to me, so I’ll pass on feedback for that.

Look forward to your progress reports on this effort.
 
K

ksrigg

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reQuest rebuild

Thanks for the reply.

I do have the complete crossover assembly including the ESL transformers. It is the large printed circuit board with all associated components, and actually is attacked to the entire back board with the speaker connections, AC plug bass trim pot and all.

The Lambda Acoustics driver is model number 12001 PFPHN-4AF and I haven't tried to google it to see if there are any old link out there or not, but it is a very clean driver, and I think will play up to around 200 hz with no problems. I have a spec sheet somewhere and can provide T/S parameters for you.

The panels are indeed a big heat sink, and I have been trying to use a propane soldering iron, so maybe I do need hotter, but I think the problem is that I'm melting the coating on the stator at the same time the solder is trying to stick...

Anyway, I have contacted ML and perhaps they can offer some help as well. If you want to contact me by email perhaps we could discuss without burning this pages bandwidth, or perhaps other are interested as well..

I am not sure how old the panels are, so I am not sure about the high end rolloff, but understand from the person that sold them (a ML dealer) that they perform remarkably well, and he could not tell a big difference in the reQuests after replacing the panels..but we'll see.

Thanks for your help. I am fairly sure I am going to port the enclosure for the Lambdas and power them with a 250 watt plate amp, crossing as high as the plate amp will let me. I understand the ML is crossed to the panel at 200 - 250 hz but again I have not determined that number for myself...

Thanks again for any help...

Sutton
 

twich54

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ksrigg said:
Thanks for the reply.

The panels are indeed a big heat sink, and I have been trying to use a propane soldering iron, so maybe I do need hotter, but I think the problem is that I'm melting the coating on the stator at the same time the solder is trying to stick...

Sutton

Sutton, Good day, FWIW one of my other crazy hobbies is railroading and I operate live staem engines running around my back yard, I have had success soldering on them using a micro torch from "Blazer", it puts out a very contolled flame @ 2500 plus degrees. Bought mine from a company called Micro-Mark ( catalog Hobby Co.)
 
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