Sweeping up

I've learned a lot running this REW program and getting advice from the Home Theater Shack.

Here's what you want with a subwoofer: low frequencies with a 'ht' sound. This means that low bass is going to be louder than mid bass because how we hear depends on the frequency.

My 18" drivers have surprisingly good range- they seem to love the 100Hz range. Problem is- that frequency is directional. Everything over 80 is pretty much, so the subwoofer is confined to low frequencies- and you let your mains do the rest.

On advice, I set all my speakers to 'small'. This means the receiver should only send low frequencies to the subwoofer channel. I also set the crossover frequency to 100Hz- this is the point where the receiver tries to transition from the sub to the mains.

Here's what my mains only look like:


Here is what the sub by itself looks like (unfiltered):


And after a bit of fiddling, here's what the sub is by itself with several filters enabled.


I've saved my filters as 'FP6'. Heck, I'll store the file here: fp6.req

If you see, I had to really force the curve downward. This is even with the receiver allegedly trying to do its own crossover.

I try to match to a curve set for subwoofers- but with a 'house curve' thrown in. The intent is that sound at 30Hz should sound about the same as at 80. For that to happen, low frequencies needed boosting. If you look at the dark blue line above you can see that it isn't a perfect curve due to the house curve.

Now, let's see what happens when I add my mains back in.


Well, something weird has happened- with the mains added, the output is lower in some parts of the range. That's probably because of phase. Don't see it lower? Look here with all of them combined.




The black line is the combined signal. You can see it tracks the sub at low frequencies (<50) style="color: rgb(51, 102, 255); font-weight: bold;">mains at high (>100), but in that crossover region, it is lower than both.

scREWing around again

The new version of the program is pretty, but it is still frustrating. Actually, I've got some gripes (minor, because this thing is free!) that it is still painful to send settings to the EQ. Also, the new version makes it hard to compare reading after reading, opening each one in a new tab and making me reload my filter settings from disk if I want to compare what I changed on the last run directly.

In any case, I've got my sub-only response curve to be flat (actually, it rolls off like it should). I've barely started adding in my mains, but they really screw up my graph- there seems to be a lot of holes when they get involved. Part of it is probably because of where I need to set my cutover from my receiver- I've upped it to 200Hz so it doesn't take as much effect. The second thing is that my receiver is a little too smart- it wants to know what size my other speakers are so it can decide what should go to the woofer. Right now I've set my mains to 'large', and everything else to small, but wondering if I should set everything to small so the dedicated woofer does its thing alone?

REW again

One thing for any sub is that your room will have an effect on low-frequency sounds. To compensate for this, some high-end receivers can send and 'hear' sounds and do some amount of equalization.

None of them can approach the Room Equalization Wizard which is used in conjunction with a PC which plays a variety of sounds, sweeps, etc. Hook the PC output to the input of your sound system, and hook up a soundmeter to the line input. With the right cables, it can also program something like the BFD (DSP1124) with multiple filters to tune it right to your room.

As it is, I rebuilding my shuttle to do the work (it has a nice built-in soundcard), though you'd think I would use the HTPC. The HTPC is being used as the girl's PC for the moment mostly because software for HTPC is abysmal.