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Old 10th May 2006, 10:16 AM   #1
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Default How to connect multiple drivers to Passive crossover

Hey

Im interested now in making a pair of hi quality floor standers, Im going to have them as a 3 way, using a passive crossover, bought from shop (for now),

and because im buying a prefabriacted desgin, all my drivers have to have the same sensivity (well thats what I want to avoid building extra parts to attenute certain drivers),

well anyway, I want to know how you connect multiple drivers to the one area of the XO, for eg,,,say i have tweeter that have a spl of 90 Db, and my mids have a 90 spl rating as well and there both at 8 ohms, but what happens say when I connect 2 bass drivers that are 8 ohms with a 87 spl...well for starters the new ovewrall spl of the bass unit will be 90 as well but what I want to know does normal wiring rules apply to connections to crossovers as well, because now the overall ohmage to the crossover will be either 16 or 4 ohms (depending if I wire in series or parralel) and I want 8 to keep the ohmage the same if thats is what I need to do

just to clarify what i mean, say for eg...that i have 3 drivers (tweeter, mid, bass) and they have same spl and ohmage which is 8....what load does this present to the amp driveing the crossover and say im just connecting the usual way, all in phase.


Gee I can babble

can someone bassicly tell the wiring rules to passive crossovers?

Thanks
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Old 10th May 2006, 11:42 AM   #2
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The wiring rules for passive crossovers are that you wire the speakers to a crossover designed for them, not any old thing you have lying around.

What exactly are you trying to do?
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Old 10th May 2006, 04:37 PM   #3
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As well as what Al said, when you double the drivers, as you have noted, you are changing the impedance. XO's are impedance dependant, meaning if you change the impedance, you also change the XO point. So if you are using an off the shelf XO, you need either 1 driver or 4 to maintain that XO point. This includes when you attenuate the drivers. You can't simply add a resistor to it and not change the XO point.

When you say you are intending to make a high quality floorstander that really means starting from the other end. What I do is pick out a midrange and work outward from there. Once you have your three drivers and box, then you can begin work on the XO. Trying to do it the other way around can get pretty frustrating.
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Old 11th May 2006, 08:02 AM   #4
sreten is offline sreten  United Kingdom
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Default Re: How to connect multiple drivers to Passive crossover

Quote:
Originally posted by Toast_Master

but what happens say when I connect 2 bass drivers that are 8 ohms with a 87 spl
...well for starters the new overall spl of the bass unit will be 90 as well but what want to know......
Hi,

The new overall SPL dB/2.83V will be 93. albeit a 4 ohm unit.

For a 3-way without attenuators midrange and treble should be equal sensitivity.
Due to Baffle step compensation the bass unit should be 4 to 6 dB higher.


/sreten.
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Old 11th May 2006, 10:59 AM   #5
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well for starters, I have made 1 successful subwoofer and another right now, is in the making....i know enough about subwoofer diy but not near as much for normal loudspeakers

ok, my design is going to involve (so far)

3 way speaker....

Tweeter: Response Dome Tweeter

http://www.jaycar.com.au/productView...Max=&SUBCATID=

Midrange: 5inch Polycone Midrange

http://www.jaycar.com.au/productView...Max=&SUBCATID=

Bass:

http://www.altronics.com.au/index.as...=item&id=C3070

3 - way crossover, premade:

http://www.altronics.com.au/index.as...=item&id=C4009



well all these drivers have a nominal 8 ohms, and a sensivity of 94 - 95 so to me these are not a bad match

but I didnt want a cabinet 30cm+ wide, so I thought Id put the woofer in the side at the bottem, but Id prefer to have 2+ smaller drivers and mount them on the front with rest of the drivers because I like that look more. and that is why i was asking about crossover connections...

what I wanted to know was: how do you decide what load your speakers put on your amp when crossed over

this project is still in the design stage

thanks
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Old 11th May 2006, 11:17 AM   #6
sreten is offline sreten  United Kingdom
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Default Re: How to connect multiple drivers to Passive crossover

Quote:
Originally posted by Toast_Master

Im interested now in making a pair of hi quality floor standers,
Hi,

it doesn't seem to me that your interested in high quality
as your not listening to what people are trying to tell you.

You cannot start with a prebuilt crossover.
Even if you could one with an insertion loss of -1.8dB@100Hz is terrible.

You should use a quality existing speaker design.

If your mids and tweeter are 8 ohm, bass 4 ohm, amplifier sees 4 ohm.

/sreten.
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Old 11th May 2006, 11:28 AM   #7
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I said premade..."for now"...im fine with making them, but i dont know the art of it....I need it simple cause i have no testing equipment at all
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Old 11th May 2006, 11:34 AM   #8
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why does it see 4 ohm?
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Old 11th May 2006, 11:40 AM   #9
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or how about for my 1st set of speakers? i should go with a 2 - way design
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Old 11th May 2006, 04:42 PM   #10
kevinkr is offline kevinkr  United States
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Since as you have admitted you have neither experience nor currently access to test equipment, for the money to be spent you would be much better off buying a kit. There are quite a few out there with plans for building your own cabinets, and if you can follow directions you are assured of success and a reasonably good sounding pair of speakers. If you don't feel up to building the cabinet there are complete kits where all you do is assemble the system and finish the cabinet. Take a look under the kit section of madisound as an example, I assume there is a comparable outfit on your side of the world..

Some of the worst speaker systems I have ever heard were fairly expensive concoctions by inexperienced newbies who didn't really know what they were doing. In most cases a complete kit would have been cheaper and would have sounded better.

Grabbing a random assortment of drivers, stuffing them in a box and using an x-over not specifically designed for them is a recipe for bad sound.

The system I am currently building is based on components I know something about, that are known to integrate properly together, and really don't blaze any new design trails. (except for me) I also have test equipment and will shortly have a good instrument mic and pre-amp to do room and nearfield response measurements. I will then be able to tweak my x-over design hopefully to compensate for any anomolies thus discovered.
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