multiple drivers effect on impedence

audiojerry · « **on:** 8 Jan 2003, 03:23 pm »

This question relates to multiple driver arrays like the Alpha LS.
When you wire multiple drivers in series, aren't you increasing the impedence by each drivers impedence, and likewise when wiring in parallel, aren't you dividing the impedence by the number of drivers?

So if you have two 8 ohm drivers wired in parallel, would the total impedence be 4 ohms, and wired in series, would it be 16 ohms?

If you have four 8 ohm drivers wired in parallel, woud the total
impedence be 2 ohms, and in series, would it be 32?

Isn't this a real problem? How do you solve it with something like the LS?

jonwb · « **Reply #1 on:** 8 Jan 2003, 04:14 pm »

Jerry,

You wouldn't believe the wiring diagram for the Alphas!

If Danny chimes in with his OK I'll put up a picture of it in this topic. Basically he has it wired with a combination of series and parallel connections. I can't explain it because I don't know what the impedance of the drivers are to begin with. Curious though...

Brian Bunge · « **Reply #2 on:** 9 Jan 2003, 03:51 am »

Jerry,

Assuming the driver is a nominal 8 ohm, it would be pretty easy to wire them in a series/parallel configuration to end up with a nominal 8 ohm load. There are 9 woofers, so you'd wire three of them in series for a 24 ohm load. Wire the rest of them in two more groups of three as well. So now you have three 24 ohm loads. If you wire the three of them in parallel, then you end up with an 8 ohm load.

The tweeters have a nominal 4 ohm load, so wire them in 2 groups of 4 for a 16 ohm load. Then wire the 2 groups in parallel for an 8 ohm load.

Simply mathematics!

jonwb · « **Reply #3 on:** 9 Jan 2003, 04:23 am »

Yea, what he said...

... so Brian since the woofers and tweeters are generally wired together (in parallel), and they each represent an 8 ohm load, would the speaker overall be at 4ohms?

audiojerry · « **Reply #4 on:** 9 Jan 2003, 01:51 pm »

Thanks Brian. Is there any downside to this type of wiring such of changes to response curve, loss of transparency, phase, etc?

Brian Bunge · « **Reply #5 on:** 10 Jan 2003, 04:45 am »

Guys,

I'm not a crossover designer so I really am not of much help in that respect. I'm sure Danny can help though!

Danny Richie · « **Reply #6 on:** 14 Jan 2003, 11:00 pm »

Brian hit the nail on the head with the wiring configuration.

Jonwb if you want to post a picture of the wiring diagram you may.

The Alpha LS would be a flat 8 ohms by the series parallel grouping of driver that it has, but the network shifts it around some.

The shunt inductor used in the tweeter network lowers the impedance on the tweeter end and the large inductor value used in the woofer network in its baffle step compensation type design introduces some resistive load because of the high resistance of the inductor, which raises the woofer impedance some at the woofer end.

An actual impedance measurement is posted on our web site.

jonwb · « **Reply #7 on:** 15 Jan 2003, 02:11 am »

Quote from: Danny

Jonwb if you want to post a picture of the wiring diagram you may.

...put that in your pipe and smoke it.

***well that's not working anymore, try clicking:
http://www.geocities.com/jonwb/alpha/alpha_ls_wiring.JPG

UNCLE - guess I have to find another place to put pictures...

HEY! TODAY ITS WORKING!

The cross-over is pretty straight forward actually. I'll be putting mine in external boxes.

Hey Danny & Gang, I have aquired enough wiring terminals (12 sets) to be able to bi-amp my Alphas at some point. Untill I aquire the amplifiers I'll need to pull this off, I'll need to use jumpers across the terminal sets. I don't really want to make up little mini jumper wires w/ spades, and I'm not using double binding post sets that have a built in jumper strap (those things look so flimsy). What I have in mind is a thick (2.5mm (0.1in)) strip of brass. I have access to basically all the brass a guy could ask for and I was wondering if this would make a good jumper.

Jon

beat · « **Reply #8 on:** 6 Feb 2003, 04:38 pm »

gold plated brass is what my studio monitors came with. I think that would work fine. I'd like to see that wiring diagram, I am trying to figure out how to wire my center channel speaks in a d'appolito (sp?)arrangement off of the simple cross over I'm using.

doug s. · « **Reply #9 on:** 6 Feb 2003, 06:50 pm »

hey beat, is that a roundcase bevel-drive 750 duc engine in yer foto? sweet... i have a 78 darmah, w/the 900 squarecase. some of the prettiest engines eveer made, imo...

doug s.