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Discussion Starter · #1 ·
I want to build a simple 2 way speaker to get started and use an assembled 2-way crossover. I pulled apart one of my old 8 ohm speakers and the tweeter was 16 ohm and the woofer was 8 ohm. Do you have to factor in the crossover to get the final impedance? Or am I just not understanding something. I have spent most of the day trying to find the answer on the internet.


Thanks

Moto
 

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Yes you do factor in the crossover, but at a simple level it does not matter. Generally the impedance of the speaker is given by its woofer, since it draws the most power.
 

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The best way to get into DIY it to start building a proven design. Choosing drivers and building a crossover is difficult and takes lots of design and testing time. You will not get good results using a prebuilt crossover. Do some searching and lots of reading, there are tons of proven design DIY 2 ways speakers out there to get yourself going. After building them and reading a ton, you can start to build your own speaker designs.
 

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A woofer's nominal impedance is quite different than it's impedance at crossover frequency. It isn't uncommon for an 8 ohm woofer to have a 16 ohm or higher impedance at 3,000 hz, this throws the xover frequency WAY off.. Generic crossover make no compensation for this, you need to know the impedance of the drivers at x-over frequency.


Building a proven design has taken all this into account, it's costs more but will sound the best. If you want to tinker with your own design, use inexpensive components. You should be able to beat Bose/HTIB speakers by tinkering with low cost components. Buy various caps/coils/resistors and try a few to see which sounds best. Don't bother with more than a 6db/oct design, DO look into zobel networks to even out impedance peaks in xovers.


Back in the 80's when I was in high school it was all tinkering, there was no internet, computer design, etc. it cost a lot of money for good test equipment and few could afford it. It was a lot of fun and the idea was to build something better than the elcheapo commercially made stuff w/o spending much money. Now that we have computers it's MUCH easier to make excellent speakers that work right the first time.
 

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I'd do a 12db/oct crossover for the tweeter because it'll give you less phase issues (you simply wire up the tweeter in reverse and that's it). For the woofer a 6dB/oct should be enough if you intend to cross it at its natural roll-off.
 

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The 16 ohm tweeter and 8 ohm driver are really of no consequence. The amplifier only cares about the final minimum impedance and impedance curve of the speaker as a whole.


The crossover components will effect this as well. If you were to only take into account the drivers the combined response would be around 12ohm for the two drivers you are speaking of. An easy load for almost any amplifier.


What you should be more concerned about is the comparable sensitivities of the drivers you are using. Also their impedance curves and radiating patterns are a factor.


It may be easier for you to use an active crossover. Just understand you will need 4 amplifier channels instead of 2. But you could use a receiver to power those extra channels. I would be willing to help you establish a starting point for the settings if you like. Then help you troubleshoot your results as well.


Are you planning to use the drivers from your old speaker that you mentioned?


mikal
 

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Discussion Starter · #9 ·
Mikal, I really appreciate your offer. But I am going to do some more research and see if I can find what I need for my plans:


Ultimately my goal is to build high sensitivity, dynamic speakers much like MKtheater is doing with his 3731 semi clone. The personal satisfaction is only a small part of the diy for me. Having high end speakers at a fraction of what they would cost to buy is what I am striving for. I will never be able to afford to buy them as I am semi retired and basically live on a fixed income.


My first project was to be surround speakers to keep up with my JTR Triple 8's. But I just don't have the background to do that kind of expirementing with crossovers.


Hopefully I can copy someones speakers (with their permission of course) or purchase plans such as Bill Fitz. sells. Or there may be other options I haven't thouight of that my research will turn up.


Thanks

Moto
 
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