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Old 2nd May 2012, 02:08 PM   #11
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Quote:
Originally Posted by pepsi View Post
Can I put the high pass filter before the passive 2-way crossover that I'm already using?

Will the bad interaction between the HPF and my 2-way crossover sound worse than the benefits I'll get from having a sub take care of the low end?
I don't know.
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Old 2nd May 2012, 11:11 PM   #12
AllenB is offline AllenB  Australia
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You're at a place where the changes you want will lead to other changes and there are several options you can go with. Most of these changes will be based more on what is convenient rather than any major audible advantage.

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I don't want to run the 2-way speakers full range because I want the sub to take some of the work away from what will become the mid-range woofers amd hopefully they will play the mid-range better.
There are other compromises you are looking at making here that are more significant than this, is it actually a problem? If so I suppose I might look at changing the box to increase power handling or I'd preferrably filter the lowest bass at the amp and get another amp for the subs.
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Old 2nd May 2012, 11:35 PM   #13
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Originally Posted by pepsi View Post
Can I put the high pass filter before the passive 2-way crossover that I'm already using?
Put a HPF before the amplifier.
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Old 3rd May 2012, 11:31 PM   #14
pepsi is offline pepsi  United Kingdom
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I don't have the money for another amp so I was just looking for some advice regarding a passive crossover network
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Old 3rd May 2012, 11:38 PM   #15
jim1961 is offline jim1961  United States
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What is the impedance of your full range speaker and your sub?

If, they are not both 8 ohms, you could harm your amp at higher volumes unless it can drive <4 ohm load, which most cant.

You might consider getting a separate amp to power the subs

Subwoofer Amplifiers, Plate Amplifiers, Home Audio/Video Subwoofer Amplifiers, Powered Subwoofer Amplifiers Perfect for Building Your Own Powered Subwoofer.

Dayton plate amps are pretty cheap. $50 for a 70W unit. Crossover built in. Easy no fuss solution.
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Old 4th May 2012, 12:56 AM   #16
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Originally Posted by jim1961 View Post
What is the impedance of your full range speaker and your sub?

If, they are not both 8 ohms, you could harm your amp at higher volumes unless it can drive <4 ohm load, which most cant.

You might consider getting a separate amp to power the subs

Subwoofer Amplifiers, Plate Amplifiers, Home Audio/Video Subwoofer Amplifiers, Powered Subwoofer Amplifiers Perfect for Building Your Own Powered Subwoofer.

Dayton plate amps are pretty cheap. $50 for a 70W unit. Crossover built in. Easy no fuss solution.
Jim, making sure it has a voltage selector for UK.
Electrical wiring in the United Kingdom - Wikipedia, the free encyclopedia
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Old 4th May 2012, 06:49 AM   #17
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by pepsi View Post
I don't have the money for another amp so I was just looking for some advice regarding a passive crossover network
Ok. Are you able to measure frequency response? Can you measure impedance? and/or What is the woofer and the box type and size? and where are you hoping to cross it?
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Old 4th May 2012, 12:48 PM   #18
pepsi is offline pepsi  United Kingdom
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Quote:
Originally Posted by jim1961 View Post
What is the impedance of your full range speaker and your sub?

If, they are not both 8 ohms, you could harm your amp at higher volumes unless it can drive <4 ohm load, which most cant.
The 2-way speakers have a dc resistance of 4.6ohm and the sub is 4ohm.

how about taking a series feed from each speaker output channel and summing them before sending it to a low-pass filter and then the sub? That way surely the impedience will be greater and will not draw too much current?
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Old 4th May 2012, 01:07 PM   #19
jim1961 is offline jim1961  United States
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Quote:
Originally Posted by pepsi View Post
The 2-way speakers have a dc resistance of 4.6ohm and the sub is 4ohm.

how about taking a series feed from each speaker output channel and summing them before sending it to a low-pass filter and then the sub? That way surely the impedience will be greater and will not draw too much current?
Most 8 ohm speakers have a DC resistance of 6-6.5 ohms, 4 ohm speakers half that. Sounds like your sub and 2 way are around 6 ohm speakers. In parallel, that would present a 3 ohm load to your amp.

Unless your amp is rated to drive 3 ohm loads, I would advise strongly against merely running them in parallel. ( i realize your not saying you were planning to do this, just saying)

I dont follow what you mean by "summing speaker outputs"

Last edited by jim1961; 4th May 2012 at 01:11 PM.
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Old 6th May 2012, 08:25 AM   #20
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One of the biggest problems with the passive crossover is that in using quality components, you will likely spend quite a bit of the way to buying a dedicated sub amp and thats if you get the crossover frequency right. You are proposing a 120hz point but it may not be optimum and the slope of it definitely wont be.

Using a dedicated plate amp such as those available from parts express allows you to have a steeper slope, adjustable/variable frequency, and adjust level matching by taste and program material. You eliminate the risk of messing up the interaction with the 2 way's passive crossover too.

The have units that are 150 bucks to 320 bucks with 1000watts Class AB. Just a good set of inductors will be 1/2 way to a 150 watt sub amp. Im sure European distributers have plate amps in the under 200 range you need. A first order passive crossover is likely to cross the 100 dollar mark if you guess right with frequency but way more if you dont.

Good luck with your project. Better bass improves everything.
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