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Hiraga Altec crossover question

84.28.50.86
Posted on July 2, 2016 at 15:47:06
horny
Audiophile

Posts: 745
Location: holland
Joined: October 17, 2003



Hello i build once this for a 8 ohm speaker
and for a 16 ohm that is what i use now
i build it and it works.

but can someone explain me how this filter works ?
is it a 12 db slope filter?
where is the 140 ohm for?
and the 10 ohm 20 w?
i untherstand that the 6,6 mH coil 24 ohm resistor and 0,82cap parallel is a notch filter
to get some more treble out of the horns
or taming some mids i don't now.

and when i would have some attenuation from the high horn what is the best way to do that in this crossover?

i think this is the right place to ask these questions
and someone can me some more insight in this
thanks already

 

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RE: Hiraga Altec crossover question , posted on July 3, 2016 at 11:59:47
bwaslo
Manufacturer

Posts: 245
Location: Portland, OR USA
Joined: September 10, 2006
 On the LF driver, it's a 12dB/octave slope lowpass. On the HF driver, it's a 12dB/octave highpass, with a broad notch at about 2kHz. Those are the ELECTRICAL responses, by the way, the drivers themselves will add a couple more 6dB/octave slopes as well, so the overall crossover order is probably around 4th or more.

"where is the 140 ohm for?" it just makes the load on the highpass look a little more resistive.

"and the 10 ohm 20 w?" Same, for the load on the notch (and the highpass). Also provides a little attenuation.

"i untherstand that the 6,6 mH coil 24 ohm resistor and 0,82cap parallel is a notch filter
to get some more treble out of the horns
or taming some mids i don't now."
No idea why, but it actually seems a pretty screwy way to go about it! 6.6mH inductors are expensive and not very well behaved. I'd think an RC combo could be configured to do the same thing cheaper and better (but I'm not the designer, so don't know his thought processes that led to this).
_

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RE: Hiraga Altec crossover question , posted on July 3, 2016 at 14:23:04
horny
Audiophile

Posts: 745
Location: holland
Joined: October 17, 2003
 Thank you very much bwaslo!
To give some attenuation to the high horn
around 2 or 3 dB what should be changed then on this crossover ?

 

RE: Hiraga Altec crossover question , posted on July 3, 2016 at 16:02:30
Sidewinder
Audiophile

Posts: 254
Joined: April 13, 2001

Hey Horny,
I'm also working on a Hiraga style crossover for my A5 Vott. Go to Jeff's place.
This may help.
Regards,
David

 

RE: Hiraga Altec crossover question , posted on July 3, 2016 at 22:15:23
horny
Audiophile

Posts: 745
Location: holland
Joined: October 17, 2003
 hello David
yes i build that already
but i want to now how its working
i think the 24 ohm resistor is not for attenuating the high horn
i think it is part of the notch filter.

 

RE: Hiraga Altec crossover question , posted on July 4, 2016 at 01:56:57
Sidewinder
Audiophile

Posts: 254
Joined: April 13, 2001
 Hi Horny,
So, you've built this crossover with the two 12 ohm resistor and 10 ohm pot and it didn't attenuate the hf output? Maybe you might higher value resistors.
Regards,
David

 

RE: Hiraga Altec crossover question , posted on July 4, 2016 at 06:44:29
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 The EQ in the crossover has two features. L3 + R4 is a broad "notch" to shelve the 3k peak and the 24 ohm + 0.82uF is a classic peaking circuit.

The peak happens because as the frequency rises, the cap comes into play and bypasses the 24 ohm resistor, which forms a voltage divider with the 10 ohm. As frequency increases it is "turning down" the 24 ohm like a volume control, so to speak.

At low frequencies it is like the cap is not there and you only have a 2 resistor voltage divider, At high frequencies the 24 ohm "dissappears" due to the cap shorting it out for AC. At 8kc, the 0.82uF cap offers 24 ohms impedance so half of the resistor is "disappeared."

If you slightly increase the 24 ohm to 28 or 30 ohms, you will have more attenuation at the lower frequencies where it is a pure 2 resistor voltage divider and the same output at the top end because R3 is "disappeared."

I did exactly this with my Hiraga crossover (on 288C and 1505) but it was many moons ago and I forget the details. I found the lower mids to be slightly too hot with the stock values, maybe in part because I was using an Onken/416 bass cab not a VOT box.


------------------------------

Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

RE: Hiraga Altec crossover question , posted on July 4, 2016 at 22:35:49
horny
Audiophile

Posts: 745
Location: holland
Joined: October 17, 2003
 Thank you very much for the explanation Joe Roberts
no i understand a little how the crossover works
i will try then the 28 and 30 ohm also.

 

RE: Hiraga Altec crossover question , posted on July 11, 2016 at 02:39:29
alexis777
Audiophile

Posts: 3
Joined: July 11, 2016
 Hi Joe,
I appreciate a lot your treads!
I have a special question, to a rare A5 assembly, called VitaVott.
I have all components (excellent A5 cabinets, french scool, H 1505 tar filled with brass troat, excellent vitavox s2 and ak15/40 drivers, and eventually also coral 104/T500 Fostex)
and need some help for the xover..
Can I start with a Hiraga x-over? I have quit all parts (8 ohms).. I am wondering if it works... the woofer is 8 ohm the driver is nominally a 15 ohm..
May you suggest me what to do? I'll star with a two way assembly.. and eventually add the stw later

A mad idea..?
Thank you very much..
Alex

 

RE: Hiraga Altec crossover question , posted on July 11, 2016 at 06:00:07
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 Hi alex,

Sounds like a great project but I know nothing about the Vitavox parts. Few Vitavox units found their way over here. I heard a few Vita systems sounding good in Korea, where some vintage guys love Vitavox.

The Hiraga Xxover was intended to make the A5 more or less a two way, possibly with a super tweeter added very high, 10kc + for air and sparkle.

If you are going to use an actual tweeter, you can start with a standard 12dB crossover and add the tweeter where the midrange horn runs out.

The HF peaking feature of the Hiraga can be adapted for other systems but you need to know the response of the midrange horn. The idea of a series resistor to lower output bypassed with a capacitor calculated for the frequency where the HF response of the horn starts to roll off was/is common in pro sound.

These days such EQ is probably more commonly included in analog or digital crossovers rather than passive xovers. Modern controlled directivity horns are engineered to get the desired pattern, then EQ is used to get smooth frequency response.

In short, the Hiraga approach might be useful with your Vitavox but could require some adjustment

------------------------------

Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

RE: Hiraga Altec crossover question , posted on July 11, 2016 at 08:24:12
alexis777
Audiophile

Posts: 3
Joined: July 11, 2016
 Thank you very much joe,
The VV component's I have are the same used in the thrilling Vox olympian, and I am very curious to hear if this unusual combo can work..
on the paper a interessing mixed bag, the openess and speedness of the s2 with the full bodied 1505 H, and the incredible toneful ak15/40 (similar to the westrex 2080) in the A5 horn.. for the ultrabass I'll add in the future a 18" sub.
But in first instance, I hope to achieve a perfect seamless 2 way speaker..:-)
Best wishes and thank you again :-)

 

RE: Hiraga Altec crossover question , posted on July 11, 2016 at 10:02:06
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 I have no doubt that you have the ingredients and inspiration for an excellent system. You will get there.

I suppose we Americans can't complain about not having Vitavox when we have most of the Altec, WE, etc. although it is getting dispersed across the planet in recent decades, finding homes where it is most appreciated.

------------------------------

Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

RE: Hiraga Altec crossover question , posted on July 12, 2016 at 05:27:45
alexis777
Audiophile

Posts: 3
Joined: July 11, 2016
 .. thanks for the encouragement, joe, the way to heaven is still very long ...
alex

 

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