Total Impedance of a 3 way speaker system

[SCP]

Hello Everybody,

I have a quick question related to impedance i already read lots of article on same topic but couldn't get the exact answer.
I am planning to build my custom tower speakers.
I got
One 60 W 8 Ohms Tweeter
One 60 W 8 Ohms Mid Range Speaker
One 60 W 8 Ohms 10 Inch Sub woofer.
I going to build my custom 3rd order butter worth crossover network.

My Question is
What would be my total impedance of my tower speaker?

I know the formula 1/(1/R1 +1/R2 +1/R3) = Total Impedance.
Which in my case is 2.66 Ohms which is way low for my A/V R which say 4 to 16 Ohms.

May be my knowledge is not good enough.
Need your help experts here to give me right direction for my project.


Thanks
SCP

 

[lovinthehd]

You'll need to also factor in your passive crossover components I believe but haven't got that far into diy myself. You might try a reference like this http://www.parts-express.com/loudspeaker-design-cookbook-7th-edition-book--500-035 or the forums at that site, or the diy subforums here or at avsforum.com or diyaudio.com....

 

[lsiberian]

Unless you are planning to push your amps to the brink it really isn't a major issue.

For your first build I suggest doing a simple 2-way pair. You only need 4 drivers, and 2 crossovers. Save the bigger project for after you get some experience building speakers. There are things that only experience building a speaker will teach you. You don't want to learn those lessons on an expensive speaker project.

 

[3db]

Hello Everybody,

I have a quick question related to impedance i already read lots of article on same topic but couldn't get the exact answer.
I am planning to build my custom tower speakers.
I got
One 60 W 8 Ohms Tweeter
One 60 W 8 Ohms Mid Range Speaker
One 60 W 8 Ohms 10 Inch Sub woofer.
I going to build my custom 3rd order butter worth crossover network.

My Question is
What would be my total impedance of my tower speaker?

I know the formula 1/(1/R1 +1/R2 +1/R3) = Total Impedance.
Which in my case is 2.66 Ohms which is way low for my A/V R which say 4 to 16 Ohms.

May be my knowledge is not good enough.
Need your help experts here to give me right direction for my project.


Thanks
SCP

The error in your calculation is that you are using DC resistance instead of what the actual impedance is at a particular frequency. Furthermore, you haven't factored in the effects of the crossover on impedacne.

 

[TLS Guy]

Hello Everybody,

I have a quick question related to impedance i already read lots of article on same topic but couldn't get the exact answer.
I am planning to build my custom tower speakers.
I got
One 60 W 8 Ohms Tweeter
One 60 W 8 Ohms Mid Range Speaker
One 60 W 8 Ohms 10 Inch Sub woofer.
I going to build my custom 3rd order butter worth crossover network.

My Question is
What would be my total impedance of my tower speaker?

I know the formula 1/(1/R1 +1/R2 +1/R3) = Total Impedance.
Which in my case is 2.66 Ohms which is way low for my A/V R which say 4 to 16 Ohms.

May be my knowledge is not good enough.
Need your help experts here to give me right direction for my project.


Thanks
SCP

You can't tell this as you will not know until you model the final crossover. Ohms law has zero to do with this issue as with the crossover circuit the drivers are not in parallel.

How did you randomly determine you need all 3rd order crossovers?

What you need to do is put the acoustic response of the drivers into the model. Then when you know the order of the roll off of the drivers you will know what order of crossover you need to design so you have all the combined acoustic and electrical slopes sum to fourth order. That is a good starting point.

The other order of business is getting the baffle step loss compensated for in crossover design, otherwise the speaker will sound very thin and lack body.
This part of the process usually drops the impedance of the crossover below the baffle step loss frequency.

I fear you have made a common mistake in taking on a three way for your first project. Three way crossovers are a fearsome undertaking to get right. In addition to all the issues I have mentioned you have to factor in the band pass gain of the mid driver.

Two or two and a half way projects are much gentler climb.

My last question is this: - How do you know that it is even possible to design a passive crossover for the drivers you selected? If you select at random the chance of an impossible project is high.

The first step is driver selection with a very keen eye as to whether the units can be blended into a harmonious whole or not. Having three different drivers raises the chances of a no go project enormously.