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Haze Caravelle (barn find!)

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vital spark View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2020 at 12:02pm
Originally posted by njw njw wrote:

 I'm not that familiar with those HH speakers but I wonder if the crossover point (low pass) on the woofers is too high and they're beaming at certain frequencies, do the speakers sound the same when hooked up to another amp? 

ive tried various before, but cant recall 100%. I've not tried the HH's through another amp, and should be able to set something up fairly easily. great suggestion :)

I'm not 100% convinced that the tone controls on the console are working as they should. I've replaced the pots, and basic electronics in the area seem ok, but thats about my limit of expertees. 

Al
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2020 at 2:48pm
Bought the speakers with an SM200, with no real interest in it, but ive given it a damned good clean up, going over with deoxit, and couple of transistors and new power caps to get the thing sounding clean and fully operational. 

Sound wise, it’s pretty much on par with the haze console. Higher volumes and it become a struggle to do anything with the upper mid range. 


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Post Options Post Options   Thanks (1) Thanks(1)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2020 at 5:18pm
For sure a lot of old PA speakers get very shouty in the upper mids when turned up, this was probably "deliberate" in a way (as in they never bothered to sort it out) as it could be quite useful to get your vocals over a loud pub band and room full of shouting punters. For music playback, less useful! That small bullet tweeter is probably crossed in at about 5kHz, so what you are hearing is mostly the rising response and breakup modes of the woofer cone.

You could add a parallel notch filter network before the crossover. A quick look at an online calculator says that if you wire a 20uF cap, 0.5mH inductor and 2.7ohm resistor in parallel, you will get a notch filter with -3dB points at 2000 and 5000Hz with a maximum attenuation between those frequencies of 6dB. https://www.diyaudioandvideo.com/Calculator/ParallelNotchFilter/

The cap and inductor form a frequency trap (infinite impedance at their resonant freq.) and the bypass resistor determines the amount of attenuation and Q. The larger the resistor value, the deeper and narrower the notch becomes. You could even add a switch in parallel with the filter to turn it on and off.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2020 at 11:38am
Thank you very much for this. What power rating should I be aiming for in relation to the components for selection.

I’ve also been looking at the existing crossover, and can’t make sense of the inductor wiring. I’m sure it’s correct as both speakers look the same, but can’t quite figure out the inductor wiring


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Post Options Post Options   Thanks (1) Thanks(1)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2020 at 1:49pm
You will need big, high-power components as this filter is directly inline with all the current going through the speaker. 400v non-polarised caps, 1mm or 1.6mm wire inductors, 50 watt resistor on a heatsink (or even two in parallel or series for 100 watt rating).

That inductor is indeed confusing as it has 4 leads. There could be some kind of transformer or autotransformer action going on. Autoformer connection for the tweeter would kind of make sense if there aren't any other pad resistors in the circuit. 
Some testing with a signal generator and scope would be necessary to find out, unless there are any explanatory markings on it I can't see.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2020 at 2:43pm

Looks like a tapped inductor (AKA Auto transformer)....

These old PA speakers often run the woofers full range and rely on the natural roll off of the driver....

The HF is then fed via an HP filter, often using a tapped inductor instead of an l-pad to match the HF level to the LF....  Vintage JBL, Altec, BBC and Tannoy etc. used to use this (tapped inductor) approach...somthing like this:


 



Edited by APW - 29 September 2020 at 3:01pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2020 at 4:39pm
Thanks Gents, that's made sense of the exisiting crossover :)

will go and see if I can find some components to make a notch filter :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2020 at 11:34am
hi, does anyone have a steer on good websites for these components? I've got all parts found on Ebay, but looking at £50.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2020 at 1:11pm
I’m not sure if this gives any insight, or if there’s any value in using a sound meter app, but here’s them cranking out at a reasonable volume Iron Maidens - Hallowed Be Thy Name . Bruce giving it some wellie on the vocals in the peak of the track. 

To be fair I’ve been running these quite a bit lately, and they are sounding much better. I guess recones/new speakers take a bit of bedding in? 




Edited by vital spark - 05 October 2020 at 1:15pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2020 at 2:12pm
Hmm well that graph looks like the tweeters are not working at all, unless there was just no HF going on at that point in the track. Can you post a graph with 1 watt (2.83v) of pink noise? That might be easier to interpret.

And, £50 for the components for a pair of high power notch filters is about right, I'm afraid! Proper crossovers are expensive, hence why you see all sorts of corners cut in cheap boxes (like the undersized electrolytic cap and EI core inductor in your picture!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vital spark Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2020 at 4:01pm
Will do. is 2.83 measure at the speaker terminals? Just set all the tone controls to zero (mid point on the dials)
 
that electrolytic cap used to be twice the size btw before I replaced it (like for like!)
 
gotcha on the quality. I've got a decent home cinema set up, and know these things come at a price!
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