Using a passive 2way crossover as a low cut filter

[lukeyluke]

Hi I've purchased a Skytec STP-1 crossover. This is so I can take the 8 ohm output from an amplifier (100w) into an 8 ohm guitar cab (140w). The crossover splits at 180Hz which is ideal for me to protect the speaker against damage from low frequencies from my bass guitar. By using it this way I will only be using the high output from the crossover and not plugging anything into the sub output. Does anyone know if this method is ok? I don't have a high level of knowledge when it comes to the components in a passive crossover so am a little anxious that I could adding 1 + 1 and getting 3 here!

 

[americanaudiophile]

Should work fine. Depending on the sound you want the crossover point might be too high for a bass but can't harm anything by trying it.

 

[makkem]

Hi
First is the amp solid state or Tube (valve) ? as solid state hates a short and a tube hates an open which you will have for frequencies below about 100 HZ.
Second,why are you doing this as your bass has frequencies as low as 40HZ so you will be losing large amounts of volume from nearly two octaves of your lowest E string.
Third what is the guitar cab as most guitar speakers will handle low frequencies pretty well.

 

[lukeyluke]

Thanks for the replies, I've got two outputs from the amp so the subs and traditional bass sound is taken care of through another cab but I want full range from that cab so routing it from the crossover isn't an option. My setup is heavy with fx involving layering and often I cut the bass completely so the guitar cab is really part of the sound. The amp is solid state. Can I ask what you mean by open and short? Does that refer to the unused sub out on the crossover? Type of guitar cab is irrelevant as I use an octave below bass guitar alot so I really need to protect my speakers. Mainly I want to make sure the 8ohm from the amp is still matched to the 8ohm speaker cab when I only use one output from the passive crossover. Thanks very much for the input guys!

 

[makkem]

Right,in that case it will work fine .
A short is a short circuit of 0 or very low impedance and will cause a solid state amp to overload and blow fuses.
An open is an open circuit or one of very high impedance and this can damage the output transformer of a tube amp,which is why you should never run this type of amp without it being connected to speakers.If you were only using the guitar cab with the crossover then low frequencies would essentially be open circuit and could cause instability or damage to the amp.However as you are using a solid state amp and another cab then this does not apply.
Yes the 8 ohm from the amp will still match the 8 ohm of the speaker as the amp will essentially see the low frequencies as being of a very high impedance and so will deliver no power into these frequencies.

 

[lukeyluke]

Thanks so much for your help, I had no idea that solid state and valve amplification could be so different in that sense so I'm glad to have learned something new as well. Just to clarify then, should I in a different setup use both of the outputs of the crossover (from an 8ohm output) I would use an 8 ohm speaker for each output wouldn't I because the overall impedance would balance out.

 

[makkem]

Thanks so much for your help, I had no idea that solid state and valve amplification could be so different in that sense so I'm glad to have learned something new as well. Just to clarify then, should I in a different setup use both of the outputs of the crossover (from an 8ohm output) I would use an 8 ohm speaker for each output wouldn't I because the overall impedance would balance out.

Yes thats right you would use two 8 ohm speakers into the 8 ohm amp because the output is essentially split into two seperate bands (with some mixing in the middle) with each frequency band seeing 8 ohms.