Hi all, Steve from Northants checking in! 🙂
Right then here goes....
On the farm where I work I found in a dusty corner a pair of Marantz LD300's. After blowing them off they turned out to be in a pretty bad way, cabs were coming apart and the foam around all 4 drivers were shot to bits. Anyway I took them home and rigged them up to my Marantz PM6004 to see what was what. Only one of the speakers worked (all 4 speakers in 1 unit working, no sound at all from other)
I have now stripped both cabs fully and as I work in a paintshop I'm doing a complete overhall on them (well almost)
I have glued and filled the cabs and they are soon going to be painted gloss white.
I intend to use the orig tweeters and mids but swap out all 4 drivers for Peerless SLS's and fit R50 crossovers from Wilmslow audio.
Now before I go and order all the parts could you please give me some idea that this process will all work fine and dandy?!
The speakers will be used for music only (vinyl mostly)
Many thanks
Steve.🙂
Right then here goes....
On the farm where I work I found in a dusty corner a pair of Marantz LD300's. After blowing them off they turned out to be in a pretty bad way, cabs were coming apart and the foam around all 4 drivers were shot to bits. Anyway I took them home and rigged them up to my Marantz PM6004 to see what was what. Only one of the speakers worked (all 4 speakers in 1 unit working, no sound at all from other)
I have now stripped both cabs fully and as I work in a paintshop I'm doing a complete overhall on them (well almost)
I have glued and filled the cabs and they are soon going to be painted gloss white.
I intend to use the orig tweeters and mids but swap out all 4 drivers for Peerless SLS's and fit R50 crossovers from Wilmslow audio.
Now before I go and order all the parts could you please give me some idea that this process will all work fine and dandy?!
The speakers will be used for music only (vinyl mostly)
Many thanks
Steve.🙂
That crossover is for a 4-way KEF modification, or something, not a 3-way franken-marantz. Are the spiders on the woofers wrecked? If not, just make sure all drivers in the non-working cab still work and if they do, refoam, restore the xovers, and be done.
Too late I'm afraid as the crossover in one of the speakers was beyond repair so it's now long gone. The marantz speakers I have are 4 way. I'd really like to upgrade the woofers as the orig ones are also rusty aswell as ruined.
First, you need to determine whether the box volume & tuning are suitable for the replacement drivers (use unibox or Winisd). 2nd you need an appropriate crossover - easiest here is to replicate the original for mids & tweeters, & go 1st order on the SLS woofers if they're paper or poly cone. You will need to tweak the levels of the mids & tweeters to match the woofers.
No they are not 4 ways, as the two woofers are wired in parallel ( I guess ) so feed from the same ( lowpassed ) signal. They should be 16 Ω units as I see from the tag on the back that the total speaker impedance is 8 Ω
MARANTZ LD 300 - Nomos
It's a shame that the original crossover got lost - and also that 3 woofers don't work.
Ahhh I see, well thanks guys. Tbh I had a feeling it wasn't going to be that straight forward. Now I need to figure out what path to take......
Ok right. Could I upgrade the tweeter and mid aswell and then get a crossover to suit all the speakers in the unit? The volume is approx 100 litres. 900mm x 30 x 34mm
I'm in no rush as I still have to refurb the other cab yet.
Thanks for the info 🙂
I'm in no rush as I still have to refurb the other cab yet.
Thanks for the info 🙂
I can't help with the specifics of replacement drivers. However, I can say that the Cambridge Audio R50 crossover is unlikely to be the right answer. The R50 uses the no longer manufactured 8 Ohm B139, B110 & T27 drivers from Kef and the 16 Ohm Coles 4001G.
If you do go anywhere with this (challenging) project, have a look at the MiniDSP active crossover which sounds "interesting".
If you do go anywhere with this (challenging) project, have a look at the MiniDSP active crossover which sounds "interesting".
The cabinet itself doesn't count anything: it's just there for holding the drivers vertically & on axys, and to contain woofer's back wave.
Before following Pete's advice I would check first the two mids& tw's with a tester to see if there's electrical continuity; usually the woofers get blowed when the foam is gone 'cos they remain firm and when applyed power the coil melts ( no movement= no way to "drain" heat ).
So it would be good to use just one woofer, a 6-7".
Before following Pete's advice I would check first the two mids& tw's with a tester to see if there's electrical continuity; usually the woofers get blowed when the foam is gone 'cos they remain firm and when applyed power the coil melts ( no movement= no way to "drain" heat ).
So it would be good to use just one woofer, a 6-7".
I don't understand if you have at least one working crossover or not. If you have, your best chance is to build a replica of the old crossover using new caps and resistors - coils don't deteriorate. If you are unsure of the components value, buy a cheap LCR meter and measure - I have one from ebay for 10-15€ and is one of the most useful tools I have.
For the woofers I'd opt for refoaming them, so you'll be sure that the drivers are (1) appropriate for the speaker internal volume, (2) appropriate for the overall SPL, (3) appropriate for the crossover.
What most people don't understand is that replacing driver A with driver B means a new and different speaker, and thus a complete redesign of the crossover. Using old and undocumented drivers and without measuring equipment means that this task is quite impossible.
Ralf
Making crossovers etc is way ou of my depth!!!
It's only really the cabinets I want to use so can I buy a tweeter mid and 2 woofers for each speaker with crossovers to match?? Surly it can't be that complicated, can it???
It's only really the cabinets I want to use so can I buy a tweeter mid and 2 woofers for each speaker with crossovers to match?? Surly it can't be that complicated, can it???
I urge you to read this: https://sites.google.com/site/undefinition/diy-mfaq and the other FAQ of that site: https://sites.google.com/site/undefinition/
If you don't understand what is written, then it would be better to stop spending money on the broken marantz speakers, because you are literally throwing money away for a bad outcome. Buy an used working speakers instead.
BTW, you still don't say if you have at least one working crossover for the speakers. It isn't really complicated to solder components.
Ralf
If you don't understand what is written, then it would be better to stop spending money on the broken marantz speakers, because you are literally throwing money away for a bad outcome. Buy an used working speakers instead.
BTW, you still don't say if you have at least one working crossover for the speakers. It isn't really complicated to solder components.
Ralf
Thanks Ralph 🙂
Yes I'm beginning to think that throwing them on the fire might be the best option!!
And yes I do still have one (working) crossover, though it would be impossible to take it out of the speaker it's in, if that matters...
Yes I'm beginning to think that throwing them on the fire might be the best option!!
And yes I do still have one (working) crossover, though it would be impossible to take it out of the speaker it's in, if that matters...
Someone has put the crossover inside the box, so it must come out. Without seeing your box, I'm thinking of some possibilities: through the woofer hole, through the terminal hole, by means of a removable baffle or rear.
Restoring an old speaker can be fun and rewarding, if you have spare time and some basic tools.
Ralf
Restoring an old speaker can be fun and rewarding, if you have spare time and some basic tools.
Ralf
The crossover has been all glued onto a board and then that board has been glued (and I mean proper glued onto the inside rear of the speaker.
Is there absolutely no way I can order components and a matching crossover??
Is there absolutely no way I can order components and a matching crossover??
Bad sign ! I lost my message while writing !Measure inductance with an LCR meter, and also diameter. For caps, the value is written.
You say that the "cabs were coming apart". You plan to replace all four low frequency drivers at a price of some £60 each. You plan to rebuild from scratch one of the crossovers apparently without a clear understanding of the original crossover. I suspect that you aren't entirely sure of the condition of the tweeters and mid-range drivers.
Are you sure that this is a really good idea?
Are you sure that this is a really good idea?
Difficulties are just problems you haven't yet overcome! 😀
I'd take a chance on 4 cheapish drivers like this, if they fit the cutouts:
80W 8in Shielded Bass Mid Range Speaker | Maplin
I want you to reassess those Marantz crossovers and the mid and treble drivers. A good photo would tell me a lot. And some measuring and value reading. This is doable.
BTW, not a good thing to drive a speaker with no basses fitted. Awful load for the amp from the unterminated bass filter usually. Unless it's just a bafflestep coil with no capacitor.
I'd take a chance on 4 cheapish drivers like this, if they fit the cutouts:
80W 8in Shielded Bass Mid Range Speaker | Maplin
I want you to reassess those Marantz crossovers and the mid and treble drivers. A good photo would tell me a lot. And some measuring and value reading. This is doable.
BTW, not a good thing to drive a speaker with no basses fitted. Awful load for the amp from the unterminated bass filter usually. Unless it's just a bafflestep coil with no capacitor.
Attachments
I thought that problems had gone out of fashion and we now only have "issues" 😉
Is the meter in the first picture a LCR Meter and why are you using it to measure an inverted ashtray?
On a slightly more serious front, how effective / reliable / usable are (cheapish) LCR meters?
Is the meter in the first picture a LCR Meter and why are you using it to measure an inverted ashtray?
On a slightly more serious front, how effective / reliable / usable are (cheapish) LCR meters?
This engineer is too old fashioned for political correctness. I still solve problems. 🙄
But in modern speak, I was addressing an inductance issue related to nearby ground plane issues. The coil is 1mH, and the nearby metal ashtray makes some of it go missing. The tweeter picks up the LCR multimeter's 2kHz test tone as well.
A useful meter that cost me £70 at Maplin. Very accurate.
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