Hi, I have a question to run by the group. It's my first post in a while... TYIA!
I have a 212 guitar speaker cabinet wired in parallel.
The top speaker is an 8-ohm 65W guitar speaker with a 500uF cap wired to the pos terminal which acts as a 79hz high pass filter.
The bottom speaker is an 8-ohm 150W bass speaker.
The speakers are wired in parallel bringing them to 4-ohms.
The problem I''m having with this setup is the top speaker, being high frequency, is louder than the bottom speaker. I want to put an L-pad on the top speaker to lower its volume.
The amp I'm currently running is only a 15watt class a tube amp with selectable ohms. I have it set to 4-ohms. I'm looking at upgrading to a 50watt head in the future. I only want a one amp, mono setup.
My question is: if I order a stereo 8-ohm L-pad. How do I wire it in series to a single speaker? Will this setup function properly?
I have a 212 guitar speaker cabinet wired in parallel.
The top speaker is an 8-ohm 65W guitar speaker with a 500uF cap wired to the pos terminal which acts as a 79hz high pass filter.
The bottom speaker is an 8-ohm 150W bass speaker.
The speakers are wired in parallel bringing them to 4-ohms.
The problem I''m having with this setup is the top speaker, being high frequency, is louder than the bottom speaker. I want to put an L-pad on the top speaker to lower its volume.
The amp I'm currently running is only a 15watt class a tube amp with selectable ohms. I have it set to 4-ohms. I'm looking at upgrading to a 50watt head in the future. I only want a one amp, mono setup.
My question is: if I order a stereo 8-ohm L-pad. How do I wire it in series to a single speaker? Will this setup function properly?
Last edited:
You are "solving" the problem by wasting your "good" speaker 
I'd rather spend that money upgrading the weak one.
To begin with, Bass speakers are terrible for Guitar (unless you use an EVM12L) and actually produce less usable bass, because they are optimized to a lower octave than the Guitar produces.
The chest pounding bass of a classic Marshall 4x12" actually lies around 100/120Hz , go figure.
While your Bass speaker probably excels, say, between 40 and 60 Hz .......
And drop that 500uF cap, just wire them in parallel and set the impedance selector accordingly.
I don't even want to think about the "crossover cap" you used.
I'd rather spend that money upgrading the weak one.
To begin with, Bass speakers are terrible for Guitar (unless you use an EVM12L) and actually produce less usable bass, because they are optimized to a lower octave than the Guitar produces.
The chest pounding bass of a classic Marshall 4x12" actually lies around 100/120Hz
, go figure.While your Bass speaker probably excels, say, between 40 and 60 Hz .......
And drop that 500uF cap, just wire them in parallel and set the impedance selector accordingly.
I don't even want to think about the "crossover cap" you used.
Greetings
Your "high pass" cap is quite large. With an 8 ohm nominal driver impedance and the 500uF cap - your crossover point is about 40 Hz.
The single cap being only a 6dB per octave cross, still has a lot of lows coming through below 40 Hz...
The 65 watt driver must have a significantly higher sensitivity to make it louder than your "bass" speaker, especially considering the very low crossover point.
If you are seeking around a 79 or 80 Hz cross point, it would need to be 250uF non-polarized cap. Even that cap will still allow significant low end getting through.
Perhaps consider a lower value cap for a higher cross point.
An L-pad of sufficient wattage capability could be utilized AFTER the cap and properly connected to the "high" speaker, and permit an adjustable "high" level while maintaining the impedance so the crossover point does not shift. Which is a main reason for L-pad use.
I would consider a 100 watt rated L-pad even if you are only anticipating a 50 watt amp to use. It gives you some extra heat dissipation ability.
Your 4 ohm nominal load impedance will rise in value as the frequency content goes lower.
Setting your amp to a 4 ohm setting is appropriate.
Carry on
Last edited:
So, nominal driver impedance is what I use to select the cap? Not nominal load impedance? I did not know that... The same applies when choosing the L-pad impedance?
The sensitivity of the guitar speaker is 98dB, bass speaker is 97dB. I may not need the L-pad with the right cap in place.
Thanks djcgtr, very helpful.
The sensitivity of the guitar speaker is 98dB, bass speaker is 97dB. I may not need the L-pad with the right cap in place.
Thanks djcgtr, very helpful.
You are most welcome.
Yes, any passive crossover is calculated using the nominal driver impedance value it is feeding. Also a L-pad is to match the driver impedance.
The L-pad is basically 2 variable resistors within the unit, that maintains, in your case for instance, the 8 ohm "load" that the crossover components "see" feeding the driver. The resistances vary, changing how much signal is fed the driver but still results in an 8 ohm load which is what you need so the crossover does not appreciably move the cross point.
All drivers have a lot of different impedance values depending on the frequency being fed to it. If you seek the impedance graph from the manufacturer, it will show the varying impedances vs. frequency, within the suggested usable range of sound reproduction.
The driver is still marketed as a certain nominal impedance.
Your two drivers only being 1 dB difference in ratings is not much. This is assuming the manufacturer is providing correct - and - comparable information, such as 97 dB at 1 watt at 1 meter...
Another variable is what frequency did the makers "determine" the sensitivity...
You can use any of several charts found on the 'net to determine your desired cross point. You can certainly try the new cap in place and if desired, then add the L-pad.
A typical L-pad, when looking at it, with the knob shaft facing you - the left terminal is the (+) coming from the crossover (input to L-pad)
The center terminal will go to (+) on the driver and the right most terminal is the common that connects to the driver (-) and the negative of the amp feeding the crossover.
It gets a little expensive to procure and try several different non-polarized caps to decide where you do wish to cross the "high" driver.
Best of luck on choosing your cross point.
Carry on
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.