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mulane
Junior Contributor 10+
Joined: 29 Aug 2011
Posts: 16
Location: Australia
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 Posted: Mon Aug 29, 2011 2:22 pm Post subject: using the 104aB tweeter circuit with Atkinson SOTA crossover |
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Hello. I'm new here and it seems people here know a thing or two about upgrading KEF crossovers.
I built some ETI KEF transmission line speakers using B139/B110/T27As many years ago and use them to this day. The crossovers are almost identical to the P. Atkinson SOTA crossovers. I am currently rebuilding the (external) crossovers into some nice Japanese packing boxes and plan on upgrading the Elcaps to Jantzen crosscaps in the bass/mids and Z-Superiors on the tweeters.
Can anyone see a problem with using the Butterworth tweeter section of the 104aB with the Atkinson type crossover? I've had a look at the SPICE program but I'm afraid it's above my head.
I don't seem to have permission to attach pics but the ETI crossover uses a 6uF cap and 5 ohm R in series and a 0.4mH inductor and 12ohm R in parallel on the T27A. |
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ColinR
Über Contributor 1000+
Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire
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| Posted: Mon Aug 29, 2011 3:14 pm Post subject: |
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If the crossover points from the original article are given as 400Hz and 3.5kHz, you just have to remember to invert the phase of the T27 once the aB section has been retro fitted  .
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mulane
Junior Contributor 10+
Joined: 29 Aug 2011
Posts: 16
Location: Australia
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| Posted: Mon Aug 29, 2011 3:19 pm Post subject: |
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| Yes its 400 and 3.5K. Thanks for the info. Why is inverting the phase needed? |
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ColinR
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Location: Staffordshire
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| Posted: Mon Aug 29, 2011 3:23 pm Post subject: |
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| Quote: | | Why is inverting the phase needed |
aB sections are effectively 18dB/octave filters so to keep the T27 in phase you have to invert it's polarity.
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This post or any other information supplied to this website or any other by myself is not available for any form of commercial purpose i.e. to hi-fi magazines or as sales and marketing material for sleezeBay or Audiodogging pimps and the like. |
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mulane
Junior Contributor 10+
Joined: 29 Aug 2011
Posts: 16
Location: Australia
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| Posted: Mon Aug 29, 2011 3:25 pm Post subject: |
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| OK Thanks. Any other problems you see doing this? |
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ColinR
Über Contributor 1000+
Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire
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| Posted: Mon Aug 29, 2011 3:27 pm Post subject: |
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| Quote: | | Any other problems you see doing this? |
Space on the original PCB, so do the mod on a "daughter board".
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This post or any other information supplied to this website or any other by myself is not available for any form of commercial purpose i.e. to hi-fi magazines or as sales and marketing material for sleezeBay or Audiodogging pimps and the like. |
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mulane
Junior Contributor 10+
Joined: 29 Aug 2011
Posts: 16
Location: Australia
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| Posted: Mon Aug 29, 2011 3:31 pm Post subject: |
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| Thanks. There should be plenty of room on the new plywood boards I've made up. |
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