Crossover help, my first speakers almost done

[jmanlp]

So i just finished up my cabinets and I am ready to mount my drivers and install the crossover. The drivers I have are...

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=279-140
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=296-165

I bought premade 3500 Hz Dayton crossovers shown here...

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-146

One thing I didn't notice is that in the manual is it mentions that the impedance for the tweeter is designed for an 8 ohm tweeter. And, as you can see, I have a 4 ohm tweeter. I am almost clueless about crossovers and have spent very little time researching them. I guess my question is what should I do? Will it hurt my tweeters if I hook everything up. There is a jumper wire on the crossover board to set it to either 4 or 8 ohm for the woofer, but it says this is for the woofer only, and my woofer is 8 ohm, so I am going to leave it alone. In the comments for the tweeter someone mentioned they used this crossover for the tweeter. I have no idea if they added additional parts. Can I add like a 4 ohm resistor or something to get it to 8 ohms? Any thoughts, suggestions, etc. would be a great help. I would just hook them up and see what happens, but I would hate to have to buy new tweeters, or even worse, a new crossover, or both. I would love to get to listen to my speakers tonight.

Oh, my cabinets are .43 CuFt and are tuned to 50Hz. Any constructive criticism about the rest of my build would be nice too. I really liked building these so far and hope to build something else soon with everything I learned. Thanks.

 

[Rickster71]

I'm sorry to be the bearer of bad news.
Unless the crossovers are made specifically for those drivers, in that cabinet, they won't work.
A one size fits all crossover solution, does not work.

 

[jmanlp]

Do you mean from an impedance matching standpoint, or a level matching, or both? Could you elaborate on your statement. Thanks for the help.

 

[Rickster71]

Do you mean from an impedance matching standpoint, or a level matching, or both? Could you elaborate on your statement. Thanks for the help.

Each driver has an optimal crossover point, and an optimal box size.
The chance that an off the shelf x-over will match those exact drivers, in that exact box, is slim to none.

 

[Rickster71]

Below are a few links to matched speaker kits.
The drivers, cabinets and crossover are made to work together.
http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=769&CFID=4556141&CFTOKEN=62663887

http://www.madisound.com/kits/index.php

 

[jliedeka]

The issue is that the desired crossover frequency and slope depends on the two drivers being crossed over. You could get lucky with a one size fits all crossover but that would only address part of the issue.

The better crossovers use an impedance leveling circuit called a Zobel which is usually an inductor with a capacitor and a resistor.

You will also likely need an L-pad which reduces power to the tweeter so it won't be louder than the woofer.

Additionally, good crossovers have baffle step correction which compensates for the fact that some frequencies in the midrange get reinforced by the fact that they are bouncing off the baffle.

A canned crossover won't provide any of the above. To design a speaker, you need to first find drivers that can work together. You need to know, at minimum, the Thiele-Small parameters of the woofer and the resonant frequency of the tweeter. Better still would be to measure the distortion characters of the drivers to you can compensate for them in the crossover.

You may want to search for DIY designs and see if anyone is using your drivers. Try Parts Express (and their Tech Talk forum), ZaphAudio, HTGuide.com, RJB Audio, Humble Homemade HiFi, etc.

Jim

 

[jmanlp]

Thanks for all the info. I primarily bought these drives because they were on sale and had good reviews, I have no idea if they will match. I did model them in winisd the best I could to get the box volume and tune the port. So I guess what you are saying is my pre-made crossover will crossover, but my tweeter may play much too loud, and my box may make some frequencies peak since I have not compensated for them with the crossover?

I know I am opening up a whole other can of worms here, but how would a person go about designing a crossover for these two drivers (besides the fact that nobody would likely bother, since they are cheap).

Since I already have the pre-made crossovers what do I risk by hooking them up? Could I damage my tweeter or the crossover board since the design impedance for the tweeter does not match my tweeter?

Sorry for all the questions, I'm just trying to figure out as much as I can between forums and articles/guides.

 

[TLS Guy]

Thanks for all the info. I primarily bought these drives because they were on sale and had good reviews, I have no idea if they will match. I did model them in winisd the best I could to get the box volume and tune the port. So I guess what you are saying is my pre-made crossover will crossover, but my tweeter may play much too loud, and my box may make some frequencies peak since I have not compensated for them with the crossover?

I know I am opening up a whole other can of worms here, but how would a person go about designing a crossover for these two drivers (besides the fact that nobody would likely bother, since they are cheap).

Since I already have the pre-made crossovers what do I risk by hooking them up? Could I damage my tweeter or the crossover board since the design impedance for the tweeter does not match my tweeter?

Sorry for all the questions, I'm just trying to figure out as much as I can between forums and articles/guides.

Your speaker is not almost done. The crossover is the heart of any speaker, and more than any other factor or item determines its sound.

You are lucky, I know that driver, having just used it, in a design for my father. This Audax Aerogel woofers are excellent. However they have a huge break up mode causing a 9db peak at 3.8 kHz. You can not cross it over at 3,500 Hz.

Now your tweeter, I can't get acoustic data for, so I could not design a crossover for that tweeter in any event. However its resonance at 1500Hz is too high to be used with your woofer. You need to return the tweeters and crossovers.

Now I used Scanspeak tweeters because they were laying around. Very superior performance resulted from these speakers. They were able to produce deep organ notes with some authority. The whole sound was very smooth and seamless.

I have modified the design for you to use the Vifa D27TG 05/06. These are $22 each from Parts Express. I have every reason to think the speaker will still perform well, in some respects better, as the phase response is better.

You can see all the details of this design at my web site here.

The crossover parts will run you, at a guess, around $100 for the pair.

If you finish your speakers, as you describe, I can guarantee poor performance. If you follow my instructions you will have a very superior set of speakers, assuming your box is properly built, braced and ported.

If you are not able to build the crossovers, I can build them for you.

 

[jmanlp]

Thanks for taking the time to post this, it is very very helpful, I'm so glad you had something that would work with this driver. I will look into building the crossovers and getting the tweeters. I haven't built a circuit board for many years, I think I understand your schematic though. Thanks again, I really appreciate it!