Crossover help

[ZipSnipe]

I need a lil help here, I am trying to wrap my head around a amp and use of a crossover?

Here is the amp specs
Chip: TPA3116

Audio Input: Bluetooth, USB, TF, audio input jack
Audio Format: MP3, WMA, WAV, FLAC
Output Power: 50W+50W(stereo)+100W(subwoofer)
Suitable Impedance: 4, 6, 8ohm speaker
Input Voltage: 12~26V DC

Woofer specs
Power Capacity: 20W/40W RMS/peak
Sensitivity: 86dB (W/M)
Impedance: 8ohm
Re: 6.8ohm
Le: 0.78mH
Frequency response: 50Hz ~ 12KHz
Fs: 60.0Hz
Qts: 0.38
Qes: 0.46
Qms: 2.41
Vas: 5.00 (liters)
Xmax: 2.75mm

I am also using 6 @2 inch speakers 20 ohm 5 watt(chinese no specs), wired parallel

The amp has a separate channel for the woofer and two channels for 6 of the mid/highs, I will also run the amp at 12 v which will reduce the wattage going to the speakers.

I really just want to cut out bass below 3000hz going to the mid highs, can I just run a 2.4uf Mylar cap to the mid/highs ?

Similar to this design? I assume I would do a cap on each of the two channels? Or do I need to make the whole crossover with the inductor also?


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[PRR]

Six 20 Ohm speakers parallel is 3.3 Ohms, lower than the nominal 4 Ohm minimum of the amplifier.

2.4uFd into 3.3 Ohms is a 20KHz hi-pass, not what you want.

Suggest 16uFd (15uFd). Non-polar electrolytic works fine in simple systems.

Yes, cap-only "crossovers" are super common in simple systems.

 

[ZipSnipe]

Thank you I will try what you suggest, however I was told that the speakers wired in parallel come to 6.7 ohms, please note that it will be 3 speakers on each channel

 

[eriksquires]

Zip,

The high pass and low pass filters prevent the impedance of the drivers from appearing in parallel exactly.

I suggest you grab XSim crossover designer, and build an example crossover. Examine the impedance curve.

Best,


E

 

[ZipSnipe]

Thanx I tried Xsim ,it won't let me input the ohms on the drivers instead relies on a file to be downloaded. Anyway I did try this site 3 Way Crossover Design Example

I used its crossover calculator which is how I derived the cap value, however I guess its either going to be a 7.91uf cap which it says is for 6.7 ohms (with 3 @ 20 ohm speakers wired in parallel )or 2.65 uf which is for 20 ohms which what the actual individual speaker impedance. Or if PRR is correct and the ohms of the speakers wired in parallel is less than 4ohm than I will have to wire them differently

 

[eriksquires]

Hi Zip,

The point was to just use an ideal 8 ohm speaker for tweeter and woofer with a HP and LP filter. You will seee the minimum impedance is not less than 8 ohms.

I did not mean that you would get exact values, but that you would get a sense for how the individual driver impedance adds up to make the final speaker impedance.

Best,

E