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Old 20th November 2008, 10:40 AM   #1
jaya000 is offline jaya000  India
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Default What impedance?

I wish to use one 8 ohm normal & 16 ohm full range.
I hv 16 ohms with me.
Now i will connect 8 ohm directly & 16 ohm through 47 ufd condensor so that it will hv high pass at 210 hz.

What impedance will be seen by amplifier?
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Old 20th November 2008, 10:56 AM   #2
AndrewT is offline AndrewT  Scotland
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at well below 210Hz, the amp sees [47uF+16ohms]//8ohms.
at well above 210Hz, the amp sees 8//16ohms.

But, why are you running the full range over a restricted frequency range and running the normal speaker as a full range?
Something odd here.
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Old 20th November 2008, 10:57 AM   #3
infinia is offline infinia  United States
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Default Re: What impedance?

Quote:
Originally posted by jaya000
I wish to use one 8 ohm normal & 16 ohm full range.
I hv 16 ohms with me.
Now i will connect 8 ohm directly & 16 ohm through 47 ufd condensor so that it will hv high pass at 210 hz.

What impedance will be seen by amplifier?


Hi Jaya
The short answer is slightly less than 8//16 after 210 Hz.
Long answer is obtained by looking at the complex driver impedances vs freq with series cap.
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Old 20th November 2008, 11:09 AM   #4
jaya000 is offline jaya000  India
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my friend hv got 16 ohm full range of say 80W.
He wants more bass.
Hence i thought of adding normal 8 ohm speaker so that he will get more bass. Further the power of the system will be increased.
To avoid load on full range added a condensor.
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Old 20th November 2008, 11:39 AM   #5
Did it Himself
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But you won't get more bass, well not from anything other than possibly the new speaker is much bigger and dominates the whole sound. You are cutting the bass from the existing speaker then adding another speaker that will provide more across most of the band, resulting in more midrange (2x mid + 1x bass, instead of 2x bass + 1x mid).

You need to add a low-pass filter to the bass speaker and possibly remove the high-pass filter from the fullrange speaker.
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Old 20th November 2008, 01:14 PM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by richie00boy
.... and possibly remove the high-pass filter from the fullrange speaker.
Hi,

Good idea unless you want it to act as a ABR at low frequencies.
You can prevent this by mounting them in separate volumes.

/sreten.
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Old 20th November 2008, 04:24 PM   #7
jaya000 is offline jaya000  India
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The 8 ohm speaker is supposed to give more bass + mid & 16 ohm full range is supposed to give mid + high.
I might change the capacitor to 33ufd.
i want to connect two sets of speakers as per above to 4 ohms load.
will it be ok?
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Old 20th November 2008, 05:30 PM   #8
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Well 8 ohm plus 16 ohm is 5.3 ohms so if the amp can handle 4 ohms loads it will be fine. However, I'm not sure you got the point about potentially not getting more bass.
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Old 20th November 2008, 09:08 PM   #9
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Helper woofer for low bass boost needs a seriously big inductor, 8-12mH, then the helper woofer is only getting the low notes.
Don't high pass the full ranger.
I do this all the time , quite a common arrangement
Richieboy is quite correct
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Old 21st November 2008, 01:04 AM   #10
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you could try series connection with a cap across the woofer...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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