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Switch from 16 Ohm to 8 Ohm on compression driver

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serioussound View Drop Down
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    Posted: 13 July 2019 at 8:52pm
I have JBL tops loaded with:

Dual 15" 2226h + 2" 2450J (16 Ohm)

These have no passive crossovers.

I need to chenge diafragm in those drivers and for some reason I have 8 Ohm diafragm laying around.

If I chenge out the existing 16 ohm to the 8 ohm I have what can I expect to change in the dbx 260?

Is there any rule of thumb about how much difference it would make to go for the 8 Ohm?

Is it possible to double check the resistance in the diafragm laying in the carton in any way to double check?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2019 at 9:20pm
You can certainly measure the DC resistance of each voice coil with any off the shelf multimeter - the spec sheet from JBL gives you the target values to look for.

In theory, an 8 ohm version of a given driver will draw twice a much current, and thus twice as much power from a given amp for a given input setting than the 16 ohm version, so you may need to turn down the HF output of your DR260 by approximately that amount.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2019 at 9:29pm
Is not 16 ohm target value for 16 ohm version and 8 ohm target value for 8 ohm?

Can I measure the diafraghm in the package no need for put it in the magnet?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2019 at 10:28am
You can measure the dc resistance with a multimeter while still in the package - no problem. The value will be a nominal 8 or 16 ohm - usually 5/6 or 12/13 ohms for each. The actual impedance of the driver that your amplifier then sees, depends on other things, including the frequency.

As noted above, if using an active xover, the 8 ohm driver will draw more current, so will sound a bit louder and will need some gain reduction on the xover.
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serioussound View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2019 at 10:37am
But in spec for jbl 2450 it says dc resistance 4,3 for 8 ohm version and 8,5 for 16 ohm model?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2019 at 12:53pm
compression drivers have high acoustic loading so the impedance is a lot higher than the DC resistance
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2019 at 12:26pm
Originally posted by serioussound serioussound wrote:

But in spec for jbl 2450 it says dc resistance 4,3 for 8 ohm version and 8,5 for 16 ohm model?


That is common with the majority of JBL components. The DC Resistance is usually close to half of the Nominal load. Those who build loudspeakers would know this however, the end user will not. Moving from a 16 ohm driver to an 8 ohm driver will likely bring forth a little more high frequency due to the inductance (Le). You are working with old drivers so you need to find more users who worked with old JBL components. You can try Lansing Heritage as there are a plethora of JBL users with information and documents not available on JBL's website. 

Best Regards,


Edited by Elliot Thompson - 16 July 2019 at 12:28pm
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