Crossover help 8 ohm tweeters & 4 ohm woofers

[juanito305]

Hey guys, I'm kinda new to the speaker building arena and could use a hand in making a suitable crossover for my little pet project. Sorry if this is in the wrong forum and please point me in the right direction if so.

I have 2 4 inch 4 ohm woofers (WFR0400215) with Frequency Response of 90 to 10,000 Hz

I also have 2 1/2 inch 8 ohm tweeters (Tang Band 13-1761S) with a Frequency Response of 4,000 to 20,000 Hz.

From what I have read along the forums I believe they should be crossed at 5000 Hz. Am I correct?

I was looking at an off the shelf crossover (5 kHz High Pass 8 Ohm Crossover) from parts express. I am curious to know if this would be suitable for this setup?

Also how would I kill off any frequecy below 100 hz for the woofer in said setup?

Again I apologize for the noobness(?) and greatly appreciate any help!

 

[picowallspeaker]

Hi,
something like this might ( or not, best bet..?! ) work better since it has a low pass and it features a double/ selectable tap for 4/8 Ω
Dayton Audio XO2W-3K 2-Way Speaker Crossover 3,000 Hz

But...since these are expensive parts and are a shot in the dark
Your choice is better !
You can start then to "roll your own", by simply adding a 1st order lowpass
(if the woofer asks )
And later mix the two and make a 1st order series crossover

 

[juanito305]

Yea I'm trying to keep this as low cost as possible. Having 0 experience building crossovers I figured I'd just give these a shot n then try adding a larger (in number) cap inline to filter some low end.

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[picowallspeaker]

Usually woofers aren't scared by low frequency !
Probably you are reading the frequency response, which tells you when, how it starts to lose amplitude ( or gain, as usually it's not a smooth falling response at the treble but producing extra for resonances of the cone -break.up ) and so 90 Hz is at -3dB.

If you mean to kill the low freq if you think that too many watts, say 10 W, would put that woofer in trouble, add some 100 uF cap ( 1 $ or maybe 2 ) to the list *
Or also two 100 uF in series
Caps for speakers are BP...bipolarized

*Also a coil for lowpass !
Only 0.1 mH could make a difference ( but 0.3 is better !!!)

 

[juanito305]

Awesome, I will give that a shot. If worse comes to worse I can reuse the parts in other projects. I appreciate your response!

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[picowallspeaker]

If you find Wolfteeth's ( he's a member on here, but they're in the...PE forum !! ) projects
he has used those tweeters IIRC
Maybe you can copy his efforts...ehm, crossover !



( not guaranteed 'cos a project is for specific drivers and their electrical and then acoustical properties ... )

 

[midrange]

In answer to your original question, no, if one of the drivers is 4 ohm you cannot use an off the shelf crossover designed for 2 8ohm drivers. The impedance of the driver has a direct influence on the crossover values, so the woofer part of the crossover frequency will be out by a factor of 2.

I suggest that you go to Lalena.com website (you do not need to be a member) click on DIY Audio and Video, there are lots of useful areas which you can look at. The one that applies to this question is "2-way Crossover Designer (Help).

"Speaker Box Enclosure Designer" is also very useful if you have the relevant values for your drivers.

 

[juanito305]

Midrange, when I design it as a 1st order solen split with my desired values the capacitor closely matches what I need. I'm unsure of the coil though. Can I increase the impedance by adding a 4 ohm resistor to the woofer?

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[AndrewT]

Midrange, when I design it as a 1st order solen split with my desired values the capacitor closely matches what I need. I'm unsure of the coil though. Can I increase the impedance by adding a 4 ohm resistor to the woofer?

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Yes, you can increase the impedance by adding a 4ohms resistor in series with your bass speaker.

Will anyone want to listen to that?

 

[juanito305]

Yes, you can increase the impedance by adding a 4ohms resistor in series with your bass speaker.

Will anyone want to listen to that?

How do you mean? Will that kill off the bass to the speaker? It's RMS is 20 watts and I'm currently running it on a 50w RMS amp. I thought it would do me a favor and limit the power the amp delivers anyway and have less risk of blowing the speaker at higher volume levels (on the amp)

 

[system7]

Here's a detailed answer.

Your HP crossover, below, is purely for the tweeter. You need to work on the bass too IMO.

These might do it:
Dayton Audio XO2W-3.5K 2-Way Speaker Crossover 3,500 Hz
HW 2/70 NG - 8 Ohm

All a bit rough and ready. The first order circuit sound rough IMO.
The second order is better. You will need to attenuate the 88dB tweeter too to match the 83dB Fullranger, with a resistor. Usually a 2-3 litres box for a 4" bass. Hard to say really, it's Qts around 0.9, like a car speaker, which hardly needs a box at all.

 

[juanito305]

Here's a detailed answer.

Your HP crossover, below, is purely for the tweeter. You need to work on the bass too IMO.

These might do it:
Dayton Audio XO2W-3.5K 2-Way Speaker Crossover 3,500 Hz
HW 2/70 NG - 8 Ohm

All a bit rough and ready. The first order circuit sound rough IMO.
The second order is better. You will need to attenuate the 88dB tweeter too to match the 83dB Fullranger, with a resistor. Usually a 2-3 litres box for a 4" bass. Hard to say really, it's Qts around 0.9.

Awesome!! Thank you so much my friend. That seems easy enough to build, I may just have all the parts minus the resistor (hopefully radio shack has it) and I should be able to pull it off this weekend.

I will keep you posted on the results.

 

[juanito305]

question:

If I were to wire the woofers in series to make them 8 ohms then the crossover (the parts express one) then the tweeter would I still see the 8 ohm load necessary? Will the crossover point be the same afterwards? Stereo imaging is unimportant in this project, overall SQ is my goal.

 

[AllenB]

I think the concern about the impedance difference is no worse than the guessing you are doing to begin with. I mean that constructively. The woofer response might be a little recessed up at the crossover but it can be worked around and it might even be beneficial.

Say for example you bring down your tweeter level until you have balance at the crossover. This leaves you to work on the bass. Unless you can measure, this is your lot. Just remember that many designs bring the woofer upper response down a little anyway so you might get lucky.