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Restoring old goodmans - one tweeter not working

Discussion in 'd.i.y.' started by Musiciseverything, Jan 9, 2021.

  1. Musiciseverything

    Musiciseverything pfm Member

    Hello and happy new year!

    I’ve got myself some Goodmans Magnum K2 and am looking for some advice in getting them sounding top please.

    I’ve recapped crossovers before, replaced electors for polys where applicable, but I get the impression that these speakers have polys in there anyway? Does anyone here know these speakers well enough to comment?

    Also one tweeter isn’t sounding but I tested it and it seems operational. Could someone please advise how to trouble shoot with a multimeter?

    After hearing a restored pair of these, I’m really keen to get these working with my A&are A60. I think their efficiency will be a really good match.

    thanks in advance!
     
  2. Mike P

    Mike P pfm Member

    Looking at photos of a K2 crossover being sold on ebay the capacitors are electrolytic. It'll be plainly obvious as soon as you see them anyway, so take a look.

    If you change electrolytics for film caps you'll change the voicing of the speakers. I suggest you start by replacing all electrolytics (bipolar Alcaps are ideal) and then get used to the speakers for some time before considering any modifications. You could easily make them less to your liking by swapping the capacitors for films. You can buy Alcaps in a wide rangr of values from Falcon Acoustics and Crinklewood Electronics.

    If you've tested the tweeter and it works then it could be a loose connection/wiring fault somewhere or a failed electrolytic.
     
  3. Musiciseverything

    Musiciseverything pfm Member

    Thanks for taking the time to give me some pointers Mike. I had a look and took a photo and was going to post it, but looks like you found one online. I though that since the caps were bigger than the elcaps I’ve seen, that they were films, but google confirms that they are electros right enough.

    And these are so simple that if all the wires look to be connected okay, then surely it must be a faulty cap, so no need for getting the multimeter onto the right enough!

    And yes, great idea regarding the alcaps. I used them to recap, as close to like for like as possible, a pair of big high end Celef studio monitors. I was really concerned about esr. I ran them like that for a while, and one by one, introduced film caps starting with the smallest. Thought I’d run into issues when replacing the larger values with films, but they sound great. Only trouble was getting them to fit on the pcb! It didn’t end up looking too clever!

    You’re right though, I should get to know what the speakers were like as new. Film cap experiments on these can wait until I’m earning again! I’m a musician so it’s looking like another year of cancelled gigs.

    Anyhow, the caps in the goodmans have a really high voltage rating at 150v. Do you think it’s necessary to replace them with lines with quite such a high rating? I was hoping the alcap “high power” ones would do at 100v. What do you think?

    thanks again, Dave
     
  4. Nero

    Nero Wiped Clean

    I'm not overfamiliar with the K2 but I think the tweeters are a version of the DT3 or even DT4. I have a selection of NOS, so if you can post a photo of the back (and front) of the tweeter, I can see if they are any good to you.
    You should be able to measure continuity of the tweeter coil with a multimeter, but you'll have to disconnect from the crossover first
     
    Musiciseverything likes this.
  5. Musiciseverything

    Musiciseverything pfm Member

    Thanks Nero! That’s really handy to know they’re there. I’m currently working on recapping the one with the blown tweeter, to see if it was a blown electrolytic that was causing the failure. I previously sent an audio signal direct to the terminals on the tweeter in question, and it seemed to be responding like a working unit should, so fingers crossed this recap does it! If not I’ll be looking to acquire one of those that you’ve got. Dt3 sounds about right I think. Shall send a photo later.

    Jings, it’s much harder working on a non pcb crossover!I need at least one other hand to hold the wires in place when I’m soldering them onto the capacitor legs! Having to do them one at a time, but often when heating to do the next one, the solder melts and wire I just did detaches! Argh! Any advice he would be great I’m obviously missing a trick. Some kind of small crocodile clips would be really handy.



    It’s really nicely put together and designed with that bar holding the caps and inductors in place neatly like that. They are large caps given that they’re 150v and the ones I’m putting in are only 50v so tiny, so it’s not going to end up as pretty as original. Shame. I’ll see how good I can get it.
     
  6. Musiciseverything

    Musiciseverything pfm Member

    Hi Nero, so actually, it does appear to be the case that one tweeter is kaput. I removed it from the cabinet and with the bass control rolled right down, and the volume low, I connected the speaker cable form the amp to the terminals, and it made no sound.

    it is indeed one of the DT units. It’s got a blue sticker on the back. I’ll see if I can post a couple of photos.
     
  7. Musiciseverything

    Musiciseverything pfm Member

  8. Musiciseverything

    Musiciseverything pfm Member

    TOTAL DISASTER! !

    I recapped the other speaker and had running, and it sounded much better, until some distortion crept in, and before I could figure out what was happening, a pop, and silence. Now there’s no sound form the amp.

    could be any number of things, so I’ll not ask yous to speculate. I triple checked the job I’d done and nothing looked like it was shorting.

    Total bummer. Ive got a new amp arriving this week too, and I was really hoping to have these sounding stellar for its arrival, but I won’t want to have these anywhere near it. Will need to get all the gear checked by a pro. Oh well, was worth a go.
     
  9. Nero

    Nero Wiped Clean

    Yes, they look like DT3. I have a couple of DT4 you can have (same flange etc) but no idea if they would be the same sensitivity. If you get past your other hurdles, I'm happy to send them over to try out?
     
  10. Musiciseverything

    Musiciseverything pfm Member

    Hi. Thanks that’d be great! I’d be really grateful for that. I don’t know which DT mine are. Maybe I should start a new thread to see if anyone can tell me before o get you to go to the trouble of posting them over.
     
  11. Musiciseverything

    Musiciseverything pfm Member

    Hi, I think from what I can gather, that all the dt iterations are very similar, maybe slightly tweaked and improved from 1 to 4, so I’d be interested in sticking them in and giving them a whirl and would be very grateful and appreciative for you taking the time to send them. What would you like in exchange change for them?

    Dave
     
  12. Nero

    Nero Wiped Clean

    I'm not looking to make money, so PM me and I'll put them in the post. I dunno, maybe a donation to RNLI?
     
    Musiciseverything likes this.
  13. Musiciseverything

    Musiciseverything pfm Member

    That’s really good of you, thanks! And a great idea to donate some money to RNLI. My uncle volunteered for them in Arbroath. I got to go out on the big boat when I was a kid. Was very choppy and harsh on that North Sea! I’ll pm you my address.
     
  14. Musiciseverything

    Musiciseverything pfm Member

    Hi there. I’ve had a busy week of recording for online broadcasts, but tonight I finally got round to getting those tweeters in. Thanks again John. They looked like they had slightly smaller magnets than the ones that they replace. The sound of the speakers now that they are recapped and have replacement tweeters is that I feel there is some energy missing in the upper mids/lower treble, and that they perhaps could be a bit more airy. It’s strange because this is particularly noticeable after I’ve been listening to the hmv speakers I picked up for a tenner. These were made by Goodmans, and are basically a fairly flimsy cheap cabinet, with their drivers in. A ten inch and for the tweeter, it’s actually what looks to be exactly the same driver as what the magnums use for the mids. In the hmvs, this actually works really well as a tweeter, surprisingly extended and detailed, only caveat being that there is a definite sweet spot, and the imaging and high frequency impact diminishes dramatically off of it. I would have thought a speaker using these would have them crossed over really high so that the tweeter is only really handling the super extended sparkly stuff.
    On my magnums, the same drivers, are butting out hardly as much detail and texture. I’m wondering if it’s maybe because I used what caps I had lying around and that I used 4.7s to replace the 5s that were in there. Looking at a few forums before I went ahead and put them in, I got the Ida that there wouldn’t be that much audible difference between a 4.7 and a 5, but is this perhaps the issue? Would it possibly be that’s what’s perhaps making the level of the mid and tweeter lower ? Capacitors don’t affect the level of a drivers output though do they? They just affect the crossover frequency?

    sorry, I clearly don’t know much about electronics! I was considering starting a new thread asking the question of what audible difference from 4.7 to a 5 would potentially be, but I thought I’d just put it to you guys first. Any light that could be shed on this and any suggestions would greatly appreciated!
     

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