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Old 9th September 2008, 04:32 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Class-T amp driving low impedance?

Will one of these class-T amps, configured with a pair of paralleled outputs be able to drive my open-baffle woofers, consisting of two 12 inch Max Pentivent drivers?

The drivers are marked as 8 ohm but when wired in parallel, they measure only 2.9 ohm.

Power supply of the amp is 25 volts DC.
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Old 9th September 2008, 06:13 PM   #2
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A bit more research shows that I am measuring the DCR as 2.9R. So does that mean the impedance is actually 4 ohms?

(perhaps I should ask in the Loudspeaker forum)
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Old 9th September 2008, 06:28 PM   #3
DcibeL is offline DcibeL  Canada
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Yes, two 8 ohm nominal speakers in parallel makes 4 ohm. DC resistance and "nominal impedance" are very different, which is why you see 2.9 Ohm with your multimeter.
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Old 9th September 2008, 06:31 PM   #4
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Thanks DcibeL, I'll give it a try then!
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Old 9th September 2008, 10:44 PM   #5
Eva is offline Eva  Spain
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You can use some speaker modelling software to simulate impedance plots of your system based on the T/S parameters of your drivers. In most cases, woofer impedance only gets close to DCR between 100Hz and 400Hz. There should be plenty of threads on that subject, use the search engine.
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Old 9th September 2008, 11:58 PM   #6
Pano is offline Pano  United States
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You should not have trouble with those T-Amps and a 4 ohm (nominal) load. Go for it!!
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Old 10th September 2008, 06:19 AM   #7
Nuuk is offline Nuuk  United Kingdom
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Quote:
In most cases, woofer impedance only gets close to DCR between 100Hz and 400Hz.
They crossover filter is set to 60 hz so that's good to know.

I'm surprised (but perhaps I shouldn't be) how well the 4x100 currently drives a pair of Hawthorne Augies.
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Old 18th September 2008, 10:40 PM   #8
ranger3 is offline ranger3  United States
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I had problems driving 2 full range 8 ohm drivers in parallel with both the KingRex T20U and my Mardis Signature Mod TA-10.1 V3.0 .

Both amps would drop out or cut off at higher volumes. I was using two Audio Nirvana speakers in parallel.

I now bi-amp them and don't have that problem.
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Old 19th September 2008, 01:46 AM   #9
dweekie is offline dweekie  United States
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2 paralled channels should be able to drive 2 ohms, and all 4 should drive 1 ohm loads according to the datasheet. 41hz even states each channel can drive 2ohms by itself. Somebody on the 41hz forum was able to measure 11 amps out of a single channel.
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Old 19th September 2008, 03:22 AM   #10
Pano is offline Pano  United States
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Quote:
Originally posted by ranger3
Both amps would drop out or cut off at higher volumes.
That's kinda surpising. From the Trends, not really - but the TA2020 chip in the KingRex is more robust. Some of the TA2024 (Trends) chips seem more sensitive to overload than others. But I've not had a TA2020 drop out in normal playing.

But hey, you fixed it!
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