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Old 27th July 2009, 12:52 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Using different HF units with coaxial drivers

I'm trying some B&C DE 250-8 and DE 500-8 HF units with my Hawthorne Audio Sterling coaxials.

I notice that while the standard HF unit supplied with the Sterlings (ASD1001?) is repelled by the woofer magnet, the B&C units are attracted. Does this have any affect on the operation of either the HF unit, or the woofers?
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Old 28th July 2009, 05:51 PM   #2
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Aren't thereany speaker experts on this forum?
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Old 28th July 2009, 08:08 PM   #3
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The two magnets attracting/repelling probably won't have much effect, but if you want to be sure, put some metal on one of the magnets (the part that faces the other magnet), so it works like shielding. Blutack in place (stops vibration) and give it a go.
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Old 28th July 2009, 09:22 PM   #4
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Thanks Chris. The DE 500-8's require an aluminium adaptor plate that is bolted to them, and is therefore between them and the woofer magnet.

I asked because I remember using the Ciare 250 with additional magnet and it was supposed to make a difference how the additional magnet was mounted on the Ciare.
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Old 29th July 2009, 12:58 AM   #5
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Default Re: Using different HF units with coaxial drivers

Quote:
I notice that while the standard HF unit supplied with the Sterlings (ASD1001?) is repelled by the woofer magnet, the B&C units are attracted. Does this have any affect on the operation of either the HF unit, or the woofers?

The repelling action forces a little more flux into the woofer VC gap so empiracally you get maybe up to 1 dB more sensitivity. Not sure about HF unit but expect similar effects.
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Old 29th July 2009, 08:08 AM   #6
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Thanks Infinia. I guess as ever, the proof of the pudding is in the eating!

I'll move on and and see if I can integrate the new HF units with the HA woofer.
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Old 29th July 2009, 01:07 PM   #7
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According to B&C, joining the HF unit to the woofer does affect the T&S parameters of both units and you therefore need to measure the units again when they are joined together!
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Old 29th July 2009, 04:14 PM   #8
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Quote:
Originally posted by Nuuk
According to B&C, joining the HF unit to the woofer does affect the T&S parameters of both units and you therefore need to measure the units again when they are joined together!
Of course you should measure, then you'll know, but I doubt it's going to be much. On the Scanspeak pages they sell second magnets of the same size for bucking purposes of older drivers that don't have them. The difference calcs out to be ~0.25dB as the second magnet is outside the magnetic circuit and will have little effect.

The attraction/repulsion is most likely due to the magnets being charged in opposite polarity from the factory for whatever reason.
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Old 29th July 2009, 09:05 PM   #9
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When I listen using the existing crossover, it isn't so much the frequency response that is amiss, it's the timing - it's way off!
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Old 30th July 2009, 06:11 AM   #10
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Quote:
Originally posted by Nuuk
When I listen using the existing crossover, it isn't so much the frequency response that is amiss, it's the timing - it's way off!
What do you mean? A physical offset time delay between them?
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