Goodman's Magnum K series MEGA collection... Mod advice

[lysergic-skies]

I've had a lot of time over the last few days to play with this and I have come to the conclusion that I shouldn't be messing with the driver arrangement. It was an interesting play around.. but the K2 mid suits the other 2 drivers better than the K alnico. I'm no Goodman's engineer (the K alnico mid is still highly impressive though and definitely carries the weaker K tweeter through)

So I've got this now:

K2 alterations 3.jpg (22.19 KiB) Viewed 3559 times

It follows the original Goodman's XO with the mid and tweet being out of phase.

I haven't connected in series yet, because I wasn't sure what way round to connect them? + > Bass > Mid > - ? Will that be a problem if the mid is out of phase? Just to clarify, why is the treble from the woofer an issue? Are we talking damage to mid or the way the thing sounds? Because I don't think it sounds bad at all how it is.. If it's a sound preference thing I might try both for a bit. If it's a burnt mid thing, I'll change it immediately.

The 22uF is a Clarity Cap. The 4.7uF is the red AE cheapo. The mid has had a liberal coating of Plastidip and that's it. I'll wait for it to settle and keep listening. I sprayed the paper until it was quite wet and did both at the same time so they match.

I had to repair the cones first on these. The PVC ring was rippling and had moved and the centres were pushed in. I tried popping the centres out but they kept springing back in. They'd obviously been like that for a while. I wet the centre with water and gently made a tiny pin hole with a safety pin and used that to lift it back out - seal with PVA (tiny piece of Rizla if needed - decoupage!) afterwards. PVC rippling can be fixed by using hot air to soften the adhesive and manipulate the PVC ring back into place. And finally: PVA on the cone to glue back to the PVC.
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PVC issue (google images):

k2 mid - pvc.jpg (33.07 KiB) Viewed 3559 times

Sorry I should have taken a pic of mine. See the ring has crept up by several millimetres at the bottom. Keep the hot air moving you only need 10-15 seconds once the gun is up to temp (if that!) and you can push gently and slowly the ring back into place. I also had to manipulate it in other rippled areas even though it didn't look like it had slipped. The PVC probably just stretched with time.

After fix and plastidip (actually mine):

doped-repaired-k2-mid.png (403.35 KiB) Viewed 3559 times

Got a bit of orange peel on my plastidip at the top on the PVC which looks ugly but I quite like the way they look. I really should have taken a pic of them before, they were a shipwreck!

So what's the verdict? The series/parallel issue aside:

I bet you a tenner you don't agree with riat

I owe you a tenner.

Yes, that’s all I’d do. They’re decent speakers and that’s all they should need.

They are - but when altered like this they are better IMO. However, I am going to give the pristine pair to my Dad.

[lysergic-skies]

Introducing the Old El Paso spray guard. Handy for applying extra coats without removing drivers. Free in a recycle bin near you.

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Also, if anyone else is interested in doing this with K2s, securing the caps was really easy because of the brace that’s already present:

07DC2139-7C67-441C-BF32-2E2406E7C18F.jpg (245.22 KiB) Viewed 3535 times

Not the prettiest in there anymore because of all the gap filling wood glue I’ve smeared everywhere but it’s air tight

[lysergic-skies]

Without the majority of the XO network, I fancy the bass has improved. I didn’t expect this as the bass was wide open before, but it’s definitely better.

Quick question to those in the know - only on certain tracks with very piercing highs, I’m getting a slight amount of distortion from the mids. However, I am happy with their overall performance.

I was reading Doc’s explanation of where highs and lows are produced by the cone. Am I correct in thinking that I should mask off the centre of the cone and apply a light layer around the outside, or do I just give it another full coat? Or is this a symptom of running in parallel?

[Daniel Quinn]

Most damping goes around the dust cap , how much and we're is a personal learnt choice .

I had a cap on my Audax midrange for a year , removed it and was surprised by the difference .

Having said that , I've got a dome midrange for my definitive pair and that needs a cap to protect it

[lysergic-skies]

I’m not sure how I’d go about removing the dust cap on this pair now they’re liberally coated in Plastidip but could try that for the next pair.

With that said - I’ve just listened to a track that gives me a slight amount of distortion and applied very light pressure with my finger to the cap and this sorts it out.

Am I right in thinking that another coat of Plastidip is what is needed here?

Edit: just connected in series: Positive > Bass > Mid > Negative and it made no difference to the distortion. I’m gonna Plastidip it.

[RIAT]

Quick question to those in the know - only on certain tracks with very piercing highs, I’m getting a slight amount of distortion from the mids. However, I am happy with their overall performance.

I was reading Doc’s explanation of where highs and lows are produced by the cone. Am I correct in thinking that I should mask off the centre of the cone and apply a light layer around the outside, or do I just give it another full coat? Or is this a symptom of running in parallel?

I'm guessing its because you've removed so much of the crossover. You're probably hearing distortion

[lysergic-skies]

Quick question to those in the know - only on certain tracks with very piercing highs, I’m getting a slight amount of distortion from the mids. However, I am happy with their overall performance.

I was reading Doc’s explanation of where highs and lows are produced by the cone. Am I correct in thinking that I should mask off the centre of the cone and apply a light layer around the outside, or do I just give it another full coat? Or is this a symptom of running in parallel?

I'm guessing its because you've removed so much of the crossover. You're probably hearing distortion

Whilst I’m sure you’d love it to be that it wasn’t. It was that one mid had noticeably less Plastidip that had pooled around the cap. I touched it up and the problem has gone.

[lysergic-skies]

I’ll keep documenting what I am doing so it might benefit someone else, or an interesting read. I’ve learned a lot doing this so here we go.

One thing that became apparent very quickly is that this Plastidip changes A LOT with curing time. I had read in one of the threads that Doc said it needed time, but it’s an odd experience. The best way I can describe is that things just smooth out and “natrualise” even by the hour. You first apply it, have a listen because you’re impatient after the minimum amount of time and you notice to change in sound, but it’s not right. Then as time goes on it becomes better.

I went gun ho with the shipwreck mids pictured above and I perhaps shouldn’t have done. This is why:

1. Spraying this stuff on a small driver creates an uneven appearance (at least in my experience - it doesn’t spray uniformly)

2. Control is not so much there whilst spraying

3. I sprayed it on the PVC as others have done and I shouldn’t have - for no other reason than it doesn’t look as nice.

They’ve been given 2 spray coats which has liberally wetted/coated the driver. The jury is still out on that one as I very much doubt the the Plastidip has completely cured, it’s quite thick. It’s not favouring some vocals right now but today is better than yesterday so I anticipate it will improve. Distortion on high female vocals and piercing highs is gone.

With the mediocre pair of K2s, I’ve spent some time tidying them up and made some mods as well. One thing that irks me about K2s is that the bass is rear secured. It’s a crappy idea because I nearly couldn’t get one of the nuts off, and there’s no way to get your hand right in and down to the bottom through the mid hole to hold the back. I’ve seen mods where they were front secured so that’s what I’ve done. I’ve also painted the metal around the mid because we’re going all black so not to repeat my cosmetic mistakes on these mids, I’ve applied the Plastidip with a tiny paintbrush I raided from my kids art box. It was much easier to create a lovely even coat this way, apply it thinly and avoid the PVC surround. This I prefer for the mid. Perhaps the bass will be different. I have no doubt maybe not enough has been applied, but so far they sound good. I have also applied Plastidip to the bass dust cap. Again, the jury is out on this one. It definitely changed the sound to start, killing some of the higher frequencies from the bass but it does appear to be settling/returning. If it doesn’t I’ll chalk it down to experience and I’ve got the shipwreck ones to swap over.

Bottom line: right now I have a pair of arguably better sounding K’s (factory spec) and these K2s in place for comparison. They sound VERY similar. If this is what the Doc mod does to the K2s, I can’t wait to start on a pair of Ks.

Pic of K2s:



The glare on the PVC and paint really makes it look awful in the photo. It’s really not that bad at all!

Edit: nice selection of black hex screws on order!

[lysergic-skies]

Does anyone have experience with Plastidip and tweeters?

On one of the shipwreck tweeters I have managed to ease out the dome which was pushed in. It’s in bad shape cosmetically:

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The coating that’s mostly come off appears to be non-breathable. I am wondering if anyone has ever touched up a tweeter dome with Plastidip?

Problem I have is the tweeter works. I don’t want to destroy it just for looks but a lovely black finish is making me wonder….

It would be a very tentative with a tiny paintbrush job… Will it dope the tweeter in the same way or just kill all the sparkle?

[CycleCoach]

Plastidip should work fine on your tweeters. In fact "tweeter doping" works well to smooth out a spiky treble frequency response on some tweets.
As with Bison Kit on woofers, add a layer or two and then listen. You can probably add more than you think, but just remember - you can't take it away once you've added it!