Superwhamodyne tweeter replacement

[Psimon]

I need advice on replacing the tweeters on my superwhamodyne towers. I didn't build the speakers myself so I'm a bit of a novice.

I managed to get a couple of Selenium ST324 a few years ago but I'm can't find clear instructions on how to fit them. I gather they need a capacitor installing somewhere. I've already searched the forums and found the link below but the page has gone.

#http://www.bottlehead.com/smf/index.php/topic,3751.msg33906.html#msg33906

Could anyone help me out with with the information I need?

Thanks all,
Simon

 

[Paul Joppa]

Man, that goes WAY back! Below are some notes, not enough but it's all I have.

I have no Whamodyne information. If I remember correctly (no guarantee!) the Whamo was followed by the Straight 8, and then the Climax in 2007. The ST-324 was first used in the Climax, and it was successfully adapted to a few Straight 8s using the version 3.0 woofer crossover (from 2004?) and the Climax tweeter crossover. The Climax design is still online on the Bottlehead--More--Community page:

https://bottlehead.com/wp-content/uploads/2013/11/climax.pdf

The Climax document sketches some physical modifications to the tweeter as well as the crossover. But I have no memory or documentation on how or whether it would work with a Whamodyne midwoofer array.

 

[Psimon]

HI, I found this thread  https://bottlehead.com/smf/index.php?topic=3953.msg36020#msg36020 on the forum. I think the OP is the guy who built my speakers. It suggests that the same crossover configuration would work on the Whamodynes.

I've attached a pdf of the Whamodyne manual with circuit diagrams.

Just looking at the Climax crossover configuration, would I just need to replace the components in the tweeter crossover? Would I need the the version 3.0 woofer crossover set up?

Thanks for your help! Btw, these speakers have served me well for years with a Foreplay and old SEX monoblocks and I'd like to keep the system running.

 

[Paul Joppa]

OK, I've given this a little further thought.

The ST324 as described in the Climax article is pretty much limited to the 3.15kHz high-pass function. This is not too far from the 5kHz stock crossover. Not having measurements of the midwoofer array suggests that an experimental approach would be the most practical. Here is my suggested approach:

1) Start with installing the ST324, retaining the woofer crossover inductor (0.36mH) and replacing the original 1.5uF capacitor with a 0.62uF value. Listen to the system with a focus on whether the treble is too loud or too quiet.

2) If the treble is too loud, try a smaller cap; if too quiet try a larger one. Repeat until it seems balanced.

3) Then try reversing the phase of the tweeter. Choose the phasing that sounds fullest  in the low treble/high midrange, i.e. around the crossover point. You may want to re-visit the cap value for best balance if you changed the phasing.

4) At this point, it may be good enough. There are two possible ways it might be less satisfactory - the woofer array may still have enough output above the crossover frequency to muddy up the treble; and/or the small 11kHz resonance in the tweeter may bee too aggressive. Choose the most annoying issue first.

- To restrict the woofer treble, add a capacitor across the woofer array. Start with 3.3uF and increase the capacitance in small increments to find the best-sounding value. With each change, try both polarities of the tweeter, since the capacitor will alter the phase response.
'
-to kill the 11kHx resonance, install the Climax notch filter across the tweeter (that's the series 5.6 ohm/0.82uF/0.25mH network).

5) The tweeter tweaks described in the Climax document are optional, and can be done at any time - they won't have a large impact on the crossover design, though we found them to audibly improve the sound.

That should get you about as far as is practical.

 

[Psimon]

Thank you so much for taking the time to think that through for me. It'll likely take me a few weeks to get round to this project but I put so much effort into sourcing those selenium speakers (from Poland!) - it will happen.

Btw, I've attached a photo of the original Foreplay and SEX monoblocks, with the Whamodynes. Th amps have been sounding great for over 20 years and only ever needed new filter caps, a couple of resistors replaced, and fresh tubes.

Best regards
Simon

 

[Paul Birkeland]

Wow, that is some vintage BH gear right there!

 

[Doc B]

Wow, what a flashback! The dreamy soft glow and white finish on everything is kind of how my memories of the early days of Bottlehead appear in my head. Probably due to the morning after gin fog I usually had back then.

 

[Psimon]

The dreamy soft glow is down to my cheap phone and its lousy camera! Nothing to do with my own considerable gin intake