raal 70 is it robust for low crossover 6db/oct ? - diyAudio
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Old 12th December 2012, 06:44 PM   #1
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Default raal 70 is it robust for low crossover 6db/oct ?

hi all
what is in your experience the lowest crossover point at 6 dB /oct for little raal 70 amorphous core?

cheers :-)

Last edited by inertial; 14th December 2012 at 11:14 AM.
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Old 12th December 2012, 07:19 PM   #2
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Ribbons are usually not suitable for use with 1st order (6dB/oct) crossovers.

Raal themselves recommend 2.8kHz 4th order (24dB/oct) for the 70-10.
To get the similar protection from a 6dB xover one octave below crossover point (1.4k) you'd have to cross at 22kHz, which seems a bit pointless.

It appears it is not possible to use a 6dB xover with the 70-20 since Raal says a single cap will produce a 24dB slope. Guess they fiddled with the transformer ribbons use to get the impedance up to a level amps can digest.

I use Founteks as supertweeters, they are crossed in at 15kHz 24dB/oct with some heavy protection an octave below (18dB hi pass). Fountek recommends the use of at least 18dB slope filters in any case.

Also ribbons distort quite a bit low down (see Zaphs measurements on his site). I wouldn't use them below 5kHz.
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Old 12th December 2012, 07:23 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

It clearly will depend on the target sensitivity and power handling
requirements of the target complete speaker design, i.e. the SPL
requirements and the driver distortion over its working range.

There is no simple 6dB/oct "lowest point".

rgds, sreten.
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Old 12th December 2012, 08:31 PM   #4
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ive used fountek neo3.5h 2nd order circa 2.8k, putting fs down ~15db. Sounded clean, didnt measure. A 3rd order at the same point worked better, as did 2nd at 5k instead.

However the neos are hornloaded, which helps matters.
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Last edited by mondogenerator; 12th December 2012 at 08:35 PM.
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Old 12th December 2012, 09:15 PM   #5
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As the other posters noted, this is a great way to blow the ribbon to pieces. Also, any lfe will create harmonic distortion due to the very limited excursion
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Old 13th December 2012, 02:02 AM   #6
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thanks , guys :-)

no ribbon for me IMHO :-( !!!!!


cheers
inertial


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Old 14th December 2012, 01:03 AM   #7
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Quote:
Originally Posted by inertial View Post
thanks , guys :-)

no ribbon for me IMHO :-( !!!!!


cheers
inertial


Phaseless paolo pontello
Well that would be your massive loss…

I own a set of RAAL 140-15D AM monopoles and a set of RAAL 140-15D AM dipoles, and IMHO they are the greatest thing since sliced bread. You just need to use something around a 4th order crossover, that’s not such a big ask.
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Old 14th December 2012, 01:20 AM   #8
JoshK is offline JoshK  Canada
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Or cross high...
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Old 14th December 2012, 01:25 AM   #9
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Chares Darwin summed that up in this bit...

"Raal themselves recommend 2.8kHz 4th order (24dB/oct) for the 70-10.
To get the similar protection from a 6dB xover one octave below crossover point (1.4k) you'd have to cross at 22kHz, which seems a bit pointless."

Besides they sound sweet crossed over around 3k, so why waste all that lower goodness for the sake of a few more components.

Or go digital... I'm currently running mine at 36dB L-R.
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Old 14th December 2012, 11:13 AM   #10
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OK, thanks very much!
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