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Old 19th June 2014, 09:01 PM   #1
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Question 2-Way Crossover Help

Hi, I was hoping someone could please help me design a 2-way crossover for my first DIY speaker build?

I'm going to use a Peerless/Vifa 6.5" full range woofer: http://www.tymphany.com/files/NE180W-04%20Rev2_0.pdf

With this Tang Band 1" ceramic dome tweeter: http://www.tb-speaker.com/detail/1230_04/25-1719s.htm

These drivers are both nominal 4 ohm (which I will be powering from my 200W/channel at 4 ohms Emotiva UPA-200). Since the woofer has a sensitivity of 88.1 dB 1W/1m and the tweeter a sensitivity of 90 dB 1W/1m, I was thinking of using a Litwitz-Riley because it will give a -3dB dip in power response (which should give them near the same power requirements, meaning the same SPL if I'm correct).

Since the woofer's 60 degree off-axis response goes downhill after 2.1 kHz I was thinking of using that as my crossover point. The attached image is the circuit I came up with using a 2-way crossover calculator.

I'd appreciate any advice since I'm pretty clueless right now.
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Last edited by toddthemetalgod; 19th June 2014 at 09:20 PM.
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Old 20th June 2014, 12:31 AM   #2
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First, look at the impedance plots of your drivers, & re-calculate the crossover using the impedance values at the crossover frequency2nd, decide whether you need baffle step compensation, and calculate the inductor for that (baffle step freq is 115/ baffle width in metres) using a 1st order calculator
3rd add an L pad to the tweeter: L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin
calculated by the difference in driver sensitivity plus how much the BSC inductor will have caused the woofer to have dropped off at the crossover freq
That should get you in the ball park
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 20th June 2014, 03:01 AM   #3
Jsixis is offline Jsixis  United States
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Charts say 9uf on just the tweeter would be fine. Myself I would start with a 4.7uf and work my way to 10uf.
I prefer just a cap on the tweeter, the hundreds of speakers I have taken apart seem to go that way.
When you start adding inductors and resistors everything changes.
So keep it simple
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Old 20th June 2014, 03:58 AM   #4
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Re: "just a cap on the tweeter, the hundreds of speakers I have taken apart seem to go that way" - that's just because it's cheap, if you want quality you have to put in a bit more effort. 2nd order on the tweeter is better for power handling, particularly at a low crossover freq. If you've got a well behaved woofer, then first order works well with them, particularly if you're including BSC. The most critical thing in getting a speaker to sound balanced is the Tweeter L pad, too little padding sounds appealing, but is fatiguing in the long run...
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 20th June 2014, 08:17 AM   #5
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You need to be aware that what is important is the acoustic slope and not the electrical one. In other words, using an electrical slope of your choice often does not result in the same acoustic slope because of the combined effect of the crossover and the natural response of the driver. Adding to that other effects like baffle step and diffraction (both from the cabinet and baffle) makes the result of a theoretical crossover pretty useless. See here for an example: crossovers

In this same forum you'll find a sticky about designing crossover without measurement: Introduction to designing crossovers without measurement. While the first method described is of some value mainly in helping the novice understand some problems, IMHO it is overdone in the sense that simply forget the possibilities offered by a PC (for example I wouldn't add a Zobel). The method I strongly suggest is the one linked in post #20, and you can find it at the bottom of this page: software. In the same page you'll find the (free) software needed to perform the various steps of the method.

I would aim for a LR4 acoustic slope at around 2KHz, and ending probably with a 2nd order for the woofer and a 2nd/3th order for the tweeter plus L-pad. The primary coil for the woofer will be probably 1.5-2mH and that counts also for the baffle step compensation.

The drivers you chose deserves a better crossover than a (probably wrong) textbook one. And do not forget that you won't find a 9.48uF cap or a 0.61mH coil, so simulate with "standard" values.

Ralf
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Old 20th June 2014, 02:59 PM   #6
jReave is offline jReave  Canada
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^ +1

To add the 1 missing step from Charlie's page, you have to use SplTrace to create your FRD and ZMA files.
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Old 20th June 2014, 04:18 PM   #7
jReave is offline jReave  Canada
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I'm not familiar with that tweeter so looking into it the 1st thing I notice is that it's getting some harsh sounding comments if it's crossed too low - Tang Band 25-1719S 1" Ceramic Dome Tweeter. That's not what you want to hear if you are trying to cross to a 7" driver.

If you want to stay at the same price point, the SB26STAC would be a better choice.
If you are willing to pay a little more, the SB29RDC can play a little lower still.

But there are other tweeters by Dayton, Seas, ScanSpeak, Vifa and others that will fit the bill as well.
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