AR-4X tweeter and crossover upgrade?

[harley7991]

Hi,

I'm looking to upgrade the tweeter and crossover on my 4X speakers.  The pots are heavily damage as well.  I'm hoping some of you have some recommendations on the following:

• Using the HiVi Q1R tweeter as done in the AR-2AX
  • How should the crossover be updated?
  • What pots should I use?

 

Thanks,

Harley

[swayzeeee]

Hi Harley 7991,

I had those or very similar tweeters in my pair of AR-4x's and decided to restore them to original, as documented here: 

 It took quite a while to find original tweeters on the big auction site and they were more expensive than the ones you linked to. For a while I had one speaker original and one with a modern replacement tweeter and there was no question... the original sounded better. The replacement worked and it fit in the cabinet... but I could really hear the difference.

[JKent]

Welcome Harley

The Hi-Vi tweeters you linked are great replacements for those in the AR-3a but won't work well in the 4x. The tweeter crossover in the 4x is at 2,000 Hz IIRC. The Hi-Vi's frequency response is 2,500 - 20,000.

Your best bet is to use original AR-4x tweeters. Some people (myself included) have reported some success using phenolic ring tweeters like these https://www.parts-express.com/grs-prt-8-phenolic-ring-tweeter-replacement-for-ar-4x-cts-marantz-and-more-8-ohm--270-252  Photo below shows 4x with PRT. This is NOT an "upgrade", it's a "make do" if your original tweeters are shot. IF YOUR ORIGINAL TWEETERS ARE NOT DAMAGED DO NOT REPLACE THEM.

Replace the wax 20uF capacitor with a 20uF film cap (leave the original in place and just cut the wires). If you use the PRT tweets, maybe try a smaller value cap as Roy suggested in the linked thread above.

Replace the pots with L-pads. The linked thread shows how to wire them.

Your 4x's with ORIGINAL drivers, new capacitors and new L-pads will sound great.

-Kent

 

[harley7991]

Hi Guys,

Thanks a lot for replying.  Swayzeeee - it seems you had the PRT cone tweeters and not the HiVi domes, a very different tweeter in my mind.

JKent - the HiVi response is spec'd strange on the PE site, one spot says 1.5khz to 20khz, the other says 2.5khz to 20khz.  The Fs is 1khz, and the spec sheet seems corroborate the wider frequency response.  It's tempting...

BUT, I'll try just rebuilding the crossover and attenuator first.  I see an 8 ohm l-pad with a 25 ohm resistor is used to simulate the 16 ohm pot...why not use a 16 ohm l-pad?  I guess that changes the crossover point? 

Also, there seem to be soooo many variations on the crossover.  I think I'm leaning towards the 1.2mH with the 20uF cap, but I read in another post that a 10uF cap helped clean up the peak between 1k and 2k? Or was it a 0.25mH inductor in parallel with the 20uF cap, yet speaker dave seemed to try up to a 3rd order network...it's all blending together ?

297-417-hivi-q1r-spec-sheet.pdf

[ra.ra]

On 3/17/2019 at 1:47 PM, harley7991 said:

I'm looking to upgrade the tweeter and crossover on my 4X speakers.

Hi Harley, and welcome to the forum. First question: why are you looking to "upgrade"? Can you describe existing symptoms or future desired performance characteristics?

1 hour ago, harley7991 said:

Also, there seem to be soooo many variations on the crossover.

Am not quite sure where this info is coming from, or how many variations you have documented. The 4x is a simple speaker, yet there were a few variables throughout its run. Using the typical and original woofer and tweeter, I believe there were two x-o versions, and the coil was the only variable - - I can't seem to recall what necessitated this revision... maybe stuffing quantity? A third crossover version was found in speakers using remaining AR-4 woofers. And then there was speaker dave's "improved" version - - - that was an interesting thread that resulted in a more complex crossover, but it has since received little attention in these pages. 

I  don't think I've ever seen this HiVi tweeter applied to a 4x project, and I was surprised to see that it was a near fit to the original cabinet prep cut-out. Nonetheless, the existing T-nuts do not align with the HiVi flange screw holes, so some modification would be required. And with "heavily damaged" pots, I wish you the best, but it's all "hopes and prayers" that they might be revived.