Wiring question

LizardBrain · 26th March 2006, 02:37 AM

Hello all:

I have a 4 ohm tweeter and midrange. I have 4 seven inch, 8 ohm woofers I would like to use in a cabinet with the mid and tweeter. I know that if I wire two of the woofers in parallel, they become 4 ohm as a pair. Here is my question: Regarding cabinet design, if I put the mid and tweeter in the middle of a cabinet and two woofers above them and two below them, and I parallel each pair of woofers, will all of the woofers work out to be 4 ohms?

Another question now that I think of it: If the mid and the tweeter have a spl around 89 and the woofers have an spl at 85, will mating 4 woofers with the mid and tweeter throw the sensitivities out of whack?

Thanks,

ocool_15 · 26th March 2006, 04:31 AM

yes if you use 2 parralel 8 ohm woofers per cabinet the overall impedence of your system is 4ohms.

since the mid and tweet are more efficient they will sound louder. The pair of woofers in each cabinet will see .5w per speaker and you will gain ~+3db from running both per cabinet. so I would expect you to need ~-1dB on both the mid and tweet as a starting point. If your going to filter passive(after the amp) look at buying/building Lpads for seperate volume controls.

lndm · 26th March 2006, 10:39 AM

Did you say you'd put all four woofers in parallel or pairs in series and the series pairs in parallel with each other?

Putting four in parallel gives an impedance of 2 ohms and a theoretical SPL increase of 12dB, giving 97dB/W/m.

With the series/parallel combo, the impedance would be 8 ohms and the theoretical SPL increase would be 6dB giving 91dB/W/m.

Due to line array effects, the SPLs may be a few dB lower than I have noted.

AndrewT · 26th March 2006, 11:20 AM

Hi,
you only need two 8ohm woofers to match each mid and treble combination.

The sensitivity of the 2 parallel woofers will be about the same as the mid and treble and you may find that they sound OK without correcting the upper speakers.

I would keep the woofers low in the cabinet. Keeping the mid and treble at ear level. What are you proposed crossover frequencies?

LizardBrain · 26th March 2006, 04:46 PM

My cross point just off the top of my head would be around 500 and 5000.

26th March 2006, 02:37 AM	#1
LizardBrain diyAudio Member Join Date: Mar 2006 Location: San Francisco	Wiring question Hello all: I have a 4 ohm tweeter and midrange. I have 4 seven inch, 8 ohm woofers I would like to use in a cabinet with the mid and tweeter. I know that if I wire two of the woofers in parallel, they become 4 ohm as a pair. Here is my question: Regarding cabinet design, if I put the mid and tweeter in the middle of a cabinet and two woofers above them and two below them, and I parallel each pair of woofers, will all of the woofers work out to be 4 ohms? Another question now that I think of it: If the mid and the tweeter have a spl around 89 and the woofers have an spl at 85, will mating 4 woofers with the mid and tweeter throw the sensitivities out of whack? Thanks,

26th March 2006, 11:20 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, you only need two 8ohm woofers to match each mid and treble combination. The sensitivity of the 2 parallel woofers will be about the same as the mid and treble and you may find that they sound OK without correcting the upper speakers. I would keep the woofers low in the cabinet. Keeping the mid and treble at ear level. What are you proposed crossover frequencies? __________________ regards Andrew T.

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26th March 2006, 04:31 AM	#2
ocool_15 diyAudio Member Join Date: Nov 2004 Location: sk	yes if you use 2 parralel 8 ohm woofers per cabinet the overall impedence of your system is 4ohms. since the mid and tweet are more efficient they will sound louder. The pair of woofers in each cabinet will see .5w per speaker and you will gain ~+3db from running both per cabinet. so I would expect you to need ~-1dB on both the mid and tweet as a starting point. If your going to filter passive(after the amp) look at buying/building Lpads for seperate volume controls.

26th March 2006, 10:39 AM	#3
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Did you say you'd put all four woofers in parallel or pairs in series and the series pairs in parallel with each other? Putting four in parallel gives an impedance of 2 ohms and a theoretical SPL increase of 12dB, giving 97dB/W/m. With the series/parallel combo, the impedance would be 8 ohms and the theoretical SPL increase would be 6dB giving 91dB/W/m. Due to line array effects, the SPLs may be a few dB lower than I have noted.

26th March 2006, 04:46 PM	#5
LizardBrain diyAudio Member Join Date: Mar 2006 Location: San Francisco	My cross point just off the top of my head would be around 500 and 5000.

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