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Multi-Way Conventional loudspeakers with crossovers

KEF iQ70 Upgrade
KEF iQ70 Upgrade
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Old 3rd January 2020, 07:47 PM   #1
albertshi is offline albertshi  United States
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Default KEF iQ70 Upgrade

I bought a pair of KEF iQ70 in 2012 when they were on sale. They used KEF proudly new Uni-Q point source drive for High and mid-low plus a 6.5" bass driver. After enjoying them a few months, I realized some weaknesses of these speakers. they gave some level of details but were a bit dry. their bass was less appreciated. I would be not involved enough when I was listening classical symphony. However, what would you expect hundreds bulks speakers could do? They were still great value but I hoped they could gave me more. That was why this upgrade idea started!
It was planned and being held for years because I had been very busy and/or lazy. I had searched over internet for some simple references but I found nothing. I had to start a brand new project. I had spent months for analysis, learning, sourcing/purchasing and hand craft works. Fortunately It has been done recently. I like to share here for people who owns these speakers and like to upgrade them like me. I also like to hear from your expertise opinions in this great audiophile community.
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Old 3rd January 2020, 07:58 PM   #2
maty tinman is offline maty tinman  Spain
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[Polish] KEF iQ70 - Zespoły głośnikowe | Testy w Audio.com.pl

Click the image to open in full size.

Click the image to open in full size.

more pictures: [PDF] https://audio.com.pl/files/2/6/7/267-kef-iq.pdf


Do you have a picture of the crossover?
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Old 3rd January 2020, 11:05 PM   #3
albertshi is offline albertshi  United States
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Open the speaker:
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

Last edited by albertshi; 3rd January 2020 at 11:12 PM.
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Old 3rd January 2020, 11:08 PM   #4
albertshi is offline albertshi  United States
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The Uni-Q driver:
Click the image to open in full size.
Click the image to open in full size.

Last edited by albertshi; 3rd January 2020 at 11:13 PM.
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Old 3rd January 2020, 11:09 PM   #5
albertshi is offline albertshi  United States
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The woofer:

Click the image to open in full size.

Last edited by albertshi; 3rd January 2020 at 11:14 PM.
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Old 3rd January 2020, 11:10 PM   #6
albertshi is offline albertshi  United States
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The crossover mounted inside:
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Old 3rd January 2020, 11:40 PM   #7
albertshi is offline albertshi  United States
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Crossover circuit:
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Old 3rd January 2020, 11:45 PM   #8
albertshi is offline albertshi  United States
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All the value come from their labels and verified by precision measure.
The components used in this circuit: Aluminum bi-polar caps, core inductors, air core inductor for High frequency filter. That was expected from a mid-class speakers:
Click the image to open in full size.
Click the image to open in full size.
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Old 3rd January 2020, 11:50 PM   #9
albertshi is offline albertshi  United States
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That's it for today. I was very curious for the usage of series capacitor (1500uF) in Low pass filter. The good thing is to prevent any DC current from bad amplifier, the bad is to reduce the bass extension for low frequency audio signals. Could that be a reason that this speaker doesn't produce heavy bass?
Because the high value of the capacitance, KEF could not use high quality film cap but MDL brand aluminum bi-polar caps the low end "N" series. It will be terrible cost and size if I upgrade them all to Film caps.

Last edited by albertshi; 3rd January 2020 at 11:56 PM.
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Old 4th January 2020, 08:30 AM   #10
maty tinman is offline maty tinman  Spain
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Bennic resistors and M.D.L. (Jantzen) electrolytics as my KEF Q100. I suspect that both are very bad because after changing the resistor and adding a bypass cap the sound has improved dramatically in previously improved (by hard and soft) loudspeakers.

Looking for a new pair of 0.22uf coupling caps.

Resistors with very low inductance -> speaker crossover and in others places

Click the image to open in full size.

You have to decide if you rebuild, modify the filter or do like me (hard+soft), for now.

With soft:

* Minimum Phase vs Linear Phase | Page 7 | Audio Science Review (ASR) Forum

* Minimum Phase vs Linear Phase | Page 16 | Audio Science Review (ASR) Forum
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Last edited by maty tinman; 4th January 2020 at 08:38 AM.
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