AF GB15 Tweeter - Capacitor uF?

[69661]

Hello,

Im an old hobbyist installer with some pretty tame professional experience 25 years ago or so. Acquired an older car and thought id put a new stereo in instead of replacing with factory stuff that old. Im running a JL vx1000-5i active to them at 75watts RMS for the Audio Frog GB15:

AF GB15 Speaker Specs:

• Nominal Impedance: 4 Ω
• RMS Power Handling: 100 W (with recommended crossover)
• Peak Power Handling: 300 W (with recommended crossover
• Frequency Response (-3 dB): 1.3 kHz – 20 kHz
• Sensitivity (2.83V / 1M): 90 dB
• Recommended Amplifier RMS Power Range: 20 W – 100 W
• Recommended High Pass Filter Frequency and Slope: ≥ 1.8 kHz, ≥ 12 dB/oct

Can someone help me calculate what cap I need? I have some 47uF around. What frequency would the 47uF cut off at?

 

[Perry Babin]

Is the tweeter going to have it's own dedicated channel with an electronic crossover?

 

[69661]

Is the tweeter going to have it's own dedicated channel with an electronic crossover?

Yeah. The amp has built in crossover and DSP.

 

[Perry Babin]

If the tweeter will have its own channel and the proper (safe) crossover frequency is used, the cap isn't needed but will help protect the tweeter if the amp fails and drives DC to the tweeter channel. The cap needs to be non-polarized.

 

[69661]

If the tweeter will have its own channel and the proper (safe) crossover frequency is used, the cap isn't needed but will help protect the tweeter if the amp fails and drives DC to the tweeter channel. The cap needs to be non-polarized.

Im well aware of this. What im looking for is what uF should the cap be...

 

[Perry Babin]

The value isn't important as long as the value has little or no effect at the crossover frequency. It's likely that the crossover frequency will be around 4kHz (or higher). The 47uF cap will be a crossover point of around 850Hz, well away from the electronic crossover frequency.

 

[69661]

The value isn't important as long as the value has little or no effect at the crossover frequency. It's likely that the crossover frequency will be around 4kHz (or higher). The 47uF cap will be a crossover point of around 850Hz, well away from the electronic crossover frequency.

Thanks. Im not looking for a crossover here, Im not sure why you keep referencing that, I'm looking for the translation of uF to make sure I protect the tweeter correctly from pops and what not or if I have an issue with the software and pass a full range...

 

[Perry Babin]

The cap probably won't do much to protect against transients (pops) but you shouldn't have any. If you want protection from the wrong frequencies reaching the tweeter, you need to use a cap that's going to give the same crossover frequency as the active crossover but this can cause strange response if you adjust the electronic crossover frequency.

The passive crossover frequency is 1/(2*PI*R*C)