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Old 23rd May 2007, 05:13 AM   #1
Adrianb is offline Adrianb  Canada
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Default Sharing a passive Xover

Sorry if this is in the wrong thread.

So I have a 4ohm tweeter and an 8ohm mid-range.
At 4 ohms the 2 caps I'm using give me the right frequency and conveniently enough at 8ohms the midrange is almost exactly where I'd want it.
So I figure why bother buying 2x the parts and muddling up simplicity?
My problem though is since they are in series the total impedance is something like 11.7 ohms (Iíll put the 6" driver in parallel so it lands about 4 in total, but anyway)
I'm not sure how this will change the way the caps react to the tweeter. If the first driver adds something to it then I would have something like 2 kHz in the midrange and then the tweeter's new found 11ohms would be something like... 700-800 Hz O_o. Since itís impossible for it to go lower than a certain point I don't see it as a problem but still, itís not something I can see in my head or on paper.

If anyone has any thoughts it would be appreciated.
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Old 23rd May 2007, 12:30 PM   #2
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Default Re: Sharing a passive Xover

Hi,
Could you draw a diagram? This is one of the most confusing posts I've ever come across
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Old 23rd May 2007, 03:04 PM   #3
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Hi Adrian,
I have moved this over to loudspeakers.
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Old 23rd May 2007, 04:40 PM   #4
sreten is offline sreten  United Kingdom
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Default Re: Sharing a passive Xover

Quote:
Originally posted by Adrianb

So I figure why bother buying 2x the parts and muddling up simplicity?
Hi,

I'd say its the simplicity that being muddled up.....

:0/sreten.
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Old 23rd May 2007, 05:34 PM   #5
Adrianb is offline Adrianb  Canada
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haha yah it wasn't easy to describe.

basicly..
two speakers are in parallel and there is a cap at the begining

----Capacitor---- 3" driver ------ tweeter
11.5uf 8ohm 4ohm

After the signal passes the first driver will it be permanently cut off at 2 khz or will the second driver have the added impedance. Normally the 4ohm tweeter will cut around 3 khz, well thats what the calculation says, but if its in series will it add the first driver's impedance on and not be calculated for 4ohms but for 10 ohms?

If the second driver does add up then I can use a spare 4.7uf cap to cut it off at about 3.3 khz and that will be that.
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Old 23rd May 2007, 05:44 PM   #6
Svante is offline Svante  Sweden
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Default Re: Re: Sharing a passive Xover

Quote:
Originally posted by Sonusthree
Hi,
Could you draw a diagram? This is one of the most confusing posts I've ever come across
Yes, I think a diagram is required...
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Old 23rd May 2007, 05:52 PM   #7
Adrianb is offline Adrianb  Canada
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due to popular demand
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Old 23rd May 2007, 06:52 PM   #8
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You still haven't said what your aim is.

Are you trying to cut the bass from both speakers and have them both produce the higher frequencies? I can't think why you would want to but that is what your diagram is showing.

Are you looking to produce a conventional 2 way speaker where the frequencies are split between each driver?

Are you trying to run the mid/bass 'full range' without a crossover ..... with the tweeter supporting your treble output. (The lower frequencies being blocked by the capacitor)?

Tell us more.

Here's a useful link if you are trying build a conventional crossover. It won't be the last word in accuracy but will be useful anyhow.
http://www.lalena.com/Audio/Calculator/XOver/
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Old 23rd May 2007, 07:37 PM   #9
Adrianb is offline Adrianb  Canada
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oh okay if its a question purpose.
I want to simply add a 3" driver to the high end and see if my tweeter or 5.5" midrange are missing things. Sometimes theres something missing in the upper middle and I think its because the tweeter is cut off a little too low for its own good.
If it yields no worthwhile results then i'll change the midrange caps since they're kinda cheapie temp use.

i'm tryn to cut bass out of both drivers while using the original caps setup for the tweeter.

if there is a cap between the tweeter and the midrange, do I calculate the Xover frequency for the tweeter alone or do I take the midrange into account.
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Old 23rd May 2007, 10:13 PM   #10
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I don't think that you understand the complexity of your idea. It's great that you are experimenting but you need to understand how a crossover works a little better before you mess with it like you are planning.
A basic understanding is a necessity to protect your amplifier and speakers!!

Yet again we are left with very little relevant information from you.

What speakers are they????

Is your setup currently a 3 way? (You mention 'cutting' bass but have not mentioned a bass driver.)
Are you just trying to add an extra speaker to a 2/3way setup? 4 way speakers are uncommon because of their crossover complexity and expense.

Quote:
Originally posted by Adrianb
I want to simply add a 3" driver to the high end and see if my tweeter or 5.5" midrange are missing things. Sometimes theres something missing in the upper middle and I think its because the tweeter is cut off a little too low for its own good.
Are you saying that you want to add a 3" driver 'between' the mid and treble? This is IMO an unnecessary can of worms. The added complexity of the necessarily redesigned crossover will only make things worse. It is not as simple as you think.

(Or .... are you saying that the tweeter does not reach up to 20Khz?)

If you feel that something is missing .......

Tell us more about your speakers and what you think may be missing. Your amp and source may be part of the problem too so list them as well.

Have you got access to any kind of equalizer? These are not exactly HiFi but are useful as a cheap way to find out how you would like the frequency response to be. Maybe a little treble boost would give you the extra detail you like? It's all a matter of personal taste.

It may be better to find a better mid and/or tweeter that could do a good job with the current crossover.

Try this link for crossover information. I'm sure that there are better sites out there but I can't find my bookmarks right now: http://www.lalena.com/Audio/FAQ/XOver/

Maybe someone can help you if we have the whole picture
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