How do you high pass your main speakers?

In order to fine tune a subwoofer’s crossover you need to be able to select both frequency and slope of both the high pass and low pass filters independently.

Well.... kind of sort of but no... 😀

@mijostyn in an ideal world we could effectively turn a 2 way speaker system into a 3 way and apply the same amount of thought and flexibility to both the high and low pass filters and integrate a sub just like you would a driver in a speaker cabinet. I do actually favor this approach... but it’s not strictly required if the low pas filter section is flexible enough and lets us apply EQ and control the slope and delay. That is, we CAN get a little hack-y. with the method I suggested assuming I have a DSP to manage the subwoofer from and will achieve really good results.

I do agree that no matter what you do a delicate and fine tuned integration of the subwoofer is essential. After high-passing the mains the remaining issues are relatively minor and QED with good measurements and a DSP.

I keep meaning to do a blog post on exactly how this would work, so stay tuned gang! :) I will put my money where my mouth is and take lots of measurements.

@erik_squires , The only way eric that you can do what I have been talking about is with digital signal processing. The reason you have to have independent control over both high and low pass filters both 3 or 6 dB down points and slopes is because after matching time and phase the game is keeping the subwoofers out of the midrange and relieving the main speakers of as much bass as possible, two conflicting issues. Using digital signal processing to "room control" the subwoofers wastes a lot of power and stresses the drivers. It is better to use a cleverly designed room and subwoofer array to keep nodes to a minimum and use dsp sparingly.

I am going to be Beta testing DEQX's new Pre 8 preamplifier shortly. Read up on it. It is quite a unit.

Measuring your system is always a great idea if you really want to see where your problems are. I evaluated a friends system yesterday after installing his new Clearaudio Charisma. He has a small but very nice situation in the lower level of his condo. His system has minimal distortion but he complains of not being able to tolerate louder levels and he lacks refined imaging. His problems were laid bare on the computer. His system was +5 dB at 10 kHz and the left and right channels had very different curves throughout the midrange. The high frequency boost is the reason he can't listen at louder levels and the variation between the channels is killing his image. He also uses two subwoofers with low pass filters only. After seeing his issues on the computer he is ordering a MiniDSP SHD preamplifier with which we can conquer these issues and more. 

@erik_squires , The only way eric that you can do what I have been talking about is with digital signal processing. The reason you have to have independent control over both high and low pass filters both 3 or 6 dB down points and slopes is because after matching time and phase the game is keeping the subwoofers out of the midrange and relieving the main speakers of as much bass as possible, two conflicting issues.

@mijostyn

First, weird that you can actually see how my name is spelled and still chose to misspell it.

Second, you are thinking too much like a speaker builder, which I am and respect, but it’s leaving you locked in your thinking. As speaker builders we think of the electro-acoustical properties of each driver and come up with a happy balance of slope, delay and phase matching, but if we are limited by what we can do in one filter section we can compensate for it in another. For instance, if your tweeter requires a steeper rolloff then you can compensate by removing a pole in the woofer.

This same principle also means that we can achieve very good frequency and phase matching if at least one of your filters (high or low) is one you have complete control over. So a simple high pass filter on the mains + DSP on the sub will work beautifully.

I’m working on a project right now to help demonstrate this more fully, I hope you find it helpful.

In any case, no matter how you chose to integrate a subwoofer, whether we use a DSP for both high and low pass filtering, use no high pass filter, or take the approach I suggest, taking in room measurements is essential. The basic speaker specs are practically useless in determining the appropriate filter settings once in an actual room.

@erik_squires Please excuse me Erik and no it will not or rather it will but not optimally. It is a half baked method of crossing to subwoofers. 

@erik_squires , modern digital preamps like the Anthem STR, Trinnov Amethyst and DEQX do the measurement for you and correct most of the problems along with providing crossover filters. The DEQX will quadra amp a system if you so desire.