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Multi-Way Conventional loudspeakers with crossovers

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Restoring / Modifying Goodmans Magnum K2s Advice Needed
Restoring / Modifying Goodmans Magnum K2s Advice Needed
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Old 12th September 2021, 11:11 AM   #221
david83 is offline david83  United Kingdom
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Join Date: Oct 2020
Just got these:

4F83F7E2-DC20-440C-ACC6-1D0A47820410.jpeg

They are KEF Q35ís. My luck must be in, Iíve never seen KEF in my area on freecycle either!

When I got them home I noticed one speaker sounded like it was blown. A very scratchy sort of sound on the thump of any bass. Oh well, canít win em all.

My thoughts on these are: I donít like the design of the driver, most peculiar. Itís not full range, itís a tweeter sat in the centre of a mid bass. :-/ the posts on the back of the crossover are separated for high and low frequencies.

Here is the driver:

6DCFDB09-75ED-4E19-9877-2C6C4236D0FA.jpeg

One possibility would be grabbing a cheap full range driver on AliExpress and swapping out, just using the cabinet. Pressing the cone with my hand produces the same noise! What? The cone is plastic, is it cracked? Personally, I think it sucks. But free is free and landfill we donít like, so letís disassemble:

F7144CAD-83BC-4A71-8063-2582E518334A.jpeg

So it looks like there are rough edges on that tweeter!!

939BD402-8624-4383-8EA6-DE18C2BC6CA4.jpeg

Could it be as simple as the edges scraping the cone as it flexes?

Letís tidy up the solder, push the contacts in as much as possible and tape with Kapton. After this some silicone spray to facilitate smooth movement:

9882BA73-67E9-4FD5-B93B-CCD9766CE34B.jpeg

Also here is the crossover:

70E4D87B-3B8A-4DF6-8138-4E928E1B48C3.jpeg

Theyíre about 20 years old, so Iíll put the mundorfs I just got got the Goodmans in there. The bass value is 10uF and the tweeter value is 8uF. I have a 10uF, and will use 2 x 4.7uFs in parallel for the tweeter.

While I was in there I replaced the foam gaskets:

88568AE4-6824-4B85-AFF5-43438A81DD29.jpeg

Verdict? Scratchy noise is gone! Not sure if the recap has made a difference. The recapped speaker sounds the same as the one that hasnít been, so will probably put the old ones back. Not bad though.

One thing I will say (and Iím going to come across as a real bass junkie here) is that the bass SUCKS. I assumed the entire cabinet would be open to increase the bass, but itís blocked off 3/4 of the way down. I wonder if opening that up would help. Not sure how Iíd get a power tool in there though.

I like deep rich sound. Iím like that Monty Python sketch, I like woody not tinny: Monty Python's best sketch ever : British Broadcasting Corporation : Free Download, Borrow, and Streaming : Internet Archive

My daughter is already eyeing them up.
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Old 12th September 2021, 01:14 PM   #222
Galu is offline Galu  Scotland
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Good work on bringing these speakers "up to scratch"!

Any attempt at changing the internal volume will upset the tuning of the port and the bass response will change unpredictably.

The KEF Q35 is a compact floorstander which cost £349 when introduced in 1997.

It is the concentric arrangement of bass cone and tweeter that contributes to the quality of imaging for which the Q35s are valued.
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Old 12th September 2021, 01:19 PM   #223
david83 is offline david83  United Kingdom
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I’ve removed the large blob of black sticky blutack type stuff that seals around the hole where the wire feeds from the top section to the bottom section of the cabinet and that seems to have done quite a bit for the bass should I put it back?

I’m always dead chuffed when I can fix something like this.

Edit: whoops, just seen your above post. I really must stop getting distracted then continuing a post from a while back. :-P I’ll pop it back in then. I suppose if it’s not me listening to them it’s not really a problem.

Last edited by david83; 12th September 2021 at 01:45 PM.
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Old 12th September 2021, 01:53 PM   #224
system7 is offline system7  United Kingdom
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HaHa, you must have found the reason somebody dumped the KEF Q35 speakers!

Interestingly simple crossover on a polycone bass. I don't know if these were Mundorf NP capacitors you fitted, but I think it's likely you had a broken solder joint there. The vibration often cracks them

I forgot to properly solder the 8.2R/4.7uF shunt on these:

Click the image to open in full size.

Click the image to open in full size.

Sounded hideous at high volume, all cracked and distorted! Thought my amp had gone wonky.

As for the sticky blutac, well who knows? You seem to hear different bass every day....
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Old 12th September 2021, 02:21 PM   #225
david83 is offline david83  United Kingdom
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Quote:
Originally Posted by system7 View Post
HaHa, you must have found the reason somebody dumped the KEF Q35 speakers!
I think so, I’m certainly not complaining. they listed them as working which I think was a bit naughty, not because we should complain about free but because there are plenty of people who happily collect broken (myself included) but it was 30 mins each way and if you were expecting them to work and had driven all that way then had no idea about fixing this sort of thing you might be quite disappointed.

Quote:
Originally Posted by system7 View Post
Interestingly simple crossover on a polycone bass. I don't know if these were Mundorf NP capacitors you fitted, but I think it's likely you had a broken solder joint there. The vibration often cracks them
Possibly, but they sound great now. Very clear and detailed. I have a habit of overdoing solder on things so I doubt it’ll happen again. They are shadowed by the Goodmans though. thinking about it, there was a piece of hot glue rattling around in there that had come loose from one of the ferrites, and there is a slight defect on one corner. My guess is maybe it was dropped or knocked. The lady said “they’re in the way” I like “in the way”.

Quote:
Originally Posted by system7 View Post
As for the sticky blutac, well who knows? You seem to hear different bass every day....
Now now.. all that matters is that they sound good now the caps have run in, the speakers were rearranged, the resistors were reduced and they sound awesome. Did I mention the caps have run in? :-P

Last edited by david83; 12th September 2021 at 02:27 PM.
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Old 12th September 2021, 03:49 PM   #226
Galu is offline Galu  Scotland
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Quote:
Originally Posted by david83 View Post
Did I mention the caps have run in? :-P
There's an argument that electrolytic crossover capacitors may benefit from a run in period. This may be necessary to reinforce the aluminium oxide insulating layer or dielectric which forms on one of the capacitor plates during manufacture.

The oxide layer is formed during manufacture by applying a voltage across an electrolyte paste situated between the capacitor plates - hence the name 'electrolytic'.

Since film capacitors have a layer of plastic as the dielectric there is no electrolyte involved and, technically, there should be no advantage in a run in period.

Last edited by Galu; 12th September 2021 at 04:08 PM. Reason: Detail changes to text.
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Old 14th September 2021, 11:17 PM   #227
david83 is offline david83  United Kingdom
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Sorry for the delay. Another busy start to another busy week.

That may be true, but they definitely sound different. Both the mid clarity and the bass depth have increased. Scratching my head and looking for an explanation for this, perhaps:

- the foam around the bass - although it was already improving before I added that!
- the mids being run in? I’ve seen reviews on full range drivers saying they need some time. Does the rubber surround soften and improve?
- the reduction of mid resistor - this definitely helped with balance, the KEFs clued me in on that. I was listening to them and that prompted the reduction.
- the position in the room

For whatever reason, they sound phenomenal now. Full, rich, detailed and clear. I was listening to some Chill-Hop on them earlier (yeah….. 1. That’s a thing 2. I have wide music tastes :-P) and the warmth and depth was lovely.

On a negative note, I lost the eBay auction :-( back to the search for hardwood. I’ve even considered coffee tables I can hack up! We’ll get there….
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Old 14th September 2021, 11:24 PM   #228
Galu is offline Galu  Scotland
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Chill-Hop?

I had to look that up! https://www.forbes.com/sites/william...ng-gen-z-mild/

I wish I belonged to Gen-Z!
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Old 15th September 2021, 07:39 AM   #229
david83 is offline david83  United Kingdom
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Yeah Iím Gen Y and I didnít even know I liked it. Iím not really a fan of hip hop so I didnít think I would, but curiosity got the better of me when it popped up as a suggestion:

C4515744-D592-417C-B0AB-4EC5A6F3037F.jpeg

The first thing I thought was: Wow this is actually really good background easy listening.

Jazz-Hop eh? SearchesÖ.
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Old 15th September 2021, 11:46 PM   #230
david83 is offline david83  United Kingdom
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@Galu any idea what these are? B&W?

A5BD8E29-D4EA-47FA-B071-0D13F78753D0.jpeg
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