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KG4 Modification Project


M.Att
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On 3/19/2022 at 11:03 AM, absolve2525 said:

Thanks for the post! I have two pairs of KG4, and I found one pair had fluid while the other did not. I'll have to put some in. I never critically compared the two to notice the difference. 

 

Aside from the impedance difference I can't say what the difference is from a sound perspective.  If you have any anecdotal evidence to the difference please post it, I'm curious too.

 

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21 minutes ago, M.Att said:

 

Aside from the impedance difference I can't say what the difference is from a sound perspective.  If you have any anecdotal evidence to the difference please post it, I'm curious too.

 

 

If anything, you've extended the life of that speaker sounding good for another 30-years+. 🙂

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Hi Matt,

I wonder if I've missed something here but I am wondering what's your objective(s) here?

 

When I saw that 500mh inductor on the lower woofer I figured I might model that and show what that kind of value is going to have on your system.

 

So what I've done here is use Xsim and the measurements for my KG 5.5's to show what I mean. So obviously this isn't exactly what your KG4 will be doing. To model your KG4 accurately we'd need your frequency response measurements. But seeing as we don't it is still useful as an exercise to underscore that changing the crossover without measurements is, well, lets say problematic.

 

Here is your modded crossover as I've translated it into Xsim....

 

 1398485707_KG4ModCircuit.jpg.b39197fa5c3349f7a4ab673435fa1044.jpg

 

Here's the modelled impedance curve (using KG 5.5 data)....

 

2050199028_KG4ModImp.jpg.3d9db0eee5d089d6a8709cb7c5c98ae4.jpg

 

 

Here's the modelled frequency response - black = system; yellow = tweeter; blue = upper woofer; green = lower woofer...

 

1378768603_KG4ModFreq.jpg.a758d965cee84dc7e2a9bb31c279aadc.jpg

 

So, that lower woofer is playing 40 db down. When I first modelled this I had the vertical scale set to 5db and thought I'd made a mistake because the lower woofer curve was missing! 40db down means it may as well not be connected. You won't hear anything from it! Plus that's a very expensive inductor if you can buy one? Not that you would want to.

 

For comparisson sake here's the original KG4 crossover using my KG 5.5 data - purely acedemic naturally but thought I'd show it for completeness....

 

5944552_KG4Circuit.jpg.db7bccae53b1ffd288041d152c861ff2.jpg

 

1582430573_KG4Imp.jpg.966ec9fff561b4c3d610767d8d5eccd4.jpg

 

 

 

587987892_KG4Freq.jpg.7acad246854a39e647d95ef35ae475a4.jpg

 

 

So back to my question, what's your objective here? Checking the impedance for its minimum is great for ensuring you're amp is going to be safe, but the impedance is just a small part of the picture. Without frequency response measurements I'm at a loss as to how you'll be able to arrive at a remotely workable crossover?

 

I apologise if I am coming across as negative. That's not my intention. 

 

Cheers.  🍻

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3 minutes ago, Maz4bz said:

Hi Matt,

I wonder if I've missed something here but I am wondering what's your objective(s) here?

 

When I saw that 500mh inductor on the lower woofer I figured I might model that and show what that kind of value is going to have on your system.

 

<snip for brevity>

 

I apologise if I am coming across as negative. That's not my intention. 

 

Cheers.  🍻

 

Hi Maz,

 

  That's a 0.2mH on the lower woofer, spec was for 3.0 mH but I didn't have one in my spare parts bin.   I need to look above to make certain i didn't have a typo in my post, if I did, sorry, I'll attribute that to insufficient coffee.  

 

I can whole heartily confirm that the lower woofer is not down 40db.  I can't say what the db's are, but these are far more efficient than any other speakers I have.

 

I didn't catch a negative tone, mostly vexation, which a 500mH value would definitely cause. :)   I appreciate the post though, I've not gotten around to downloading and trying REW yet. 

 

 

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All good Matt, I would still be interested in your objectives here.  Mine are to get the smoothest on and off axis response possible with highest efficiency - without too much cost in crossover parts.

 

Updated now with 0.2mh on the .5 woofer....

 

 

KG4 Mod Circuit V2.jpg

KG4 Mod Freq V2.jpg

KG4 Mod Imp V2.jpg

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1 minute ago, Maz4bz said:

Probably I'd be aiming for around 10mh....

 

KG4 Mod Freq V3.jpg

 

 

10mH looks to be ideal, I can swap them out fairly easily, I just went with what I had handy.

 

Question, how are you modeling the K80's response?

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It looks ideal in theory - I'm modelling using my KG 5.5 measurements. We need YOUR KG4 measurements for this to work.

 

Without your measurements this is all just guess work.  🧐

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2 minutes ago, Maz4bz said:

It looks ideal in theory - I'm modelling using my KG 5.5 measurements. We need YOUR KG4 measurements for this to work.

 

Without your measurements this is all just guess work.  🧐

 

:) I should have figured, thanks.  Yes, that's on my to-do list, I found my mic over the weekend and need to get cracking with the software on my Linux laptop.

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15 hours ago, M.Att said:

 

Aside from the impedance difference I can't say what the difference is from a sound perspective.  If you have any anecdotal evidence to the difference please post it, I'm curious too.

 

I didn't notice much difference at the time. I had two pairs playing side by side in stereo. Each channel had one speaker with the fluid, one without. They sounded awesome in that setup! I tried stacking, but liked side by side better in a larger room. 

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Hi Everyone,

 

  My brother left with the KG4s yesterday evening and I never got a chance to measure them.  All I can say is that they exceeded his expectations from when he dropped off the old empty cabinets a month ago.  The difference in crossovers transformed the speakers from a horn shouting at you with some muddled bass to a full, rich, detailed system.

 

  For those of you that have listened to enough of these, what would you say is the difference in sound from a refurbished KG4 or KG5.5 and the Heresys?

 

 

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  • 4 weeks later...
On 3/16/2022 at 3:08 AM, Maz4bz said:

The mic will take out the guess work and if you haul a cabinet outside you can easily take ground plane measurements to accurately verify your results.

 

You could even use an Audyssey mic plugged into your PC with REW and get an accurate result - I've tried this and it works great.

 

 

...

 

 

Maz, thanks for the REW suggestion!  I pulled out a spare PC and my Audyssey mic and connected them to a small Aiyima A07 amp.  Unfortunately the KG4 are in their new home but I tested with my Tekton Lore Monitors and DIY Classix-IIs.  In case anyone is interested, their FR graphs almost overlapped across the spectrum (in my dining room) from ~35Hz to 20KHz. 

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