Should I apply more EQ to deal with the mains?

**mlmore** · **03-04-09, 08:27 AM**

Here's my situation. I used REW and BFD to EQ a set of subs and got reasonably good results. When I add the main speakers to the mix and re-measure the response, the interaction of the mains with the subs throws the curve out of whack. My thought is that for movies this isn't a big deal because every channel is discrete, but for music where the bass crosses over at 80 Hz and there is some overlap between the subs and the mains, this might be a problem. My question is: Should I add some additional EQ to correct the bass reinforcement due to the introduction of the mains? Does it make sense to have seperate EQ setups for movies and music (2 channel matrixed)?

**brucek** · **03-04-09, 10:21 AM**

Quote:

Should I add some additional EQ to correct the bass reinforcement due to the introduction of the mains?

You should first use the phase control of the sub to try and smooth the crossover area.

Quote:

Does it make sense to have seperate EQ setups for movies and music (2 channel matrixed)?

Some people do. It usually involves adding a house curve to the bass for HT.

brucek

**mlmore** · **03-04-09, 10:31 AM**

Thanks, I'll have to try that. Since I have 2 subs that are not co-located, I guess I can use the delay setting in the AVR because there is only a 0/180 degree toggle switch on the subs. Or move the subs from the wall but that will create some aesthetic issues.

**Wayne A. Pflughaupt** · **03-04-09, 08:05 PM**

Quote:

mlmore wrote:

When I add the main speakers to the mix and re-measure the response, the interaction of the mains with the subs throws the curve out of whack.

My question is: Should I add some additional EQ to correct the bass reinforcement due to the introduction of the mains?

If all else fails you might try EQ. I’ve seen people successfully EQ phase-induced response anomalies in the crossover region before, so it might work for you too. The EQ introduces some “phasing” of its own; possibly that's why it can work.

Regards,
Wayne

**mlmore** · **03-05-09, 08:30 AM**

Thanks for the responses. I have been successful in EQ'ing the x-over region somewhat, but not perfectly. My original question is based on maybe an incomplete understanding of what happens at the x-over point for movie and music source material. If I'm listening to a 5.1 movie soundtrack, a discrete sub channel handles LFE effects. Does my AVR also direct all frequencies below 80Hz (mains set to small) to the sub as well, or is the lower frequency material embedded in the .1 signal? My sense is that it is the former.

So I guess what I'm asking is should I really be concerned with trying to EQ the subs to produce a smoother transition to the mains at the x-over, or just get the subs calibrated and leave it alone? The room response above 80 Hz is pretty whacky anyway, as I would guess it would be for most small rooms. It's the boominess/muddiness in the lower frequencies that always bothered my most.

**brucek** · **03-05-09, 10:22 AM**

Quote:

Does my AVR also direct all frequencies below 80Hz (mains set to small) to the sub as well,

Correct. The LFE channel is a separate channel (when available in the material).

Quote:

So I guess what I'm asking is should I really be concerned with trying to EQ the subs to produce a smoother transition to the mains at the x-over, or just get the subs calibrated and leave it alone?

You should first EQ the sub alone, and then add the mains and try and get the crossover area as smooth as possible (with the subs phase control or a small amount of EQ if the sub phase won't correct it).

brucek

**Wayne A. Pflughaupt** · **03-05-09, 01:35 PM**

Quote:

I have been successful in EQ'ing the x-over region somewhat, but not perfectly.

"Perfect" response is not necessary to achieve improved sound quality.

Quote:

The room response above 80 Hz is pretty whacky anyway, as I would guess it would be for most small rooms.

Right - response gets more ragged in the upper frequencies, due to comb filtering. Fortunately, mics do not "hear" the same way our ears do.

Regards,
Wayne

**mlmore** · **03-05-09, 03:20 PM**

Thanks for the tips. Here's how my calibration looks:

I can't seem to get rid of the 78Hz dip, but it's relatively narrow so probably not a big deal. What so you think?

BTW, this is for two subs and the mains running together.

**Wayne A. Pflughaupt** · **03-05-09, 03:27 PM**

Looks good. Looks pretty flat, though. Done any experimenting with house curves?

Regards,
Wayne

**mlmore** · **03-05-09, 03:30 PM**

Not really. I've been reading up on them and I think I understand why they are used. I usually run my sub hotter than the mains by about 6-8 dB. Do you think I should be accentuating the lower frequencies (20-40 Hz) a little more?

**brucek** · **03-05-09, 03:33 PM**

Quote:

Do you think I should be accentuating the lower frequencies (20-40 Hz) a little more?

No one can tell you that except for yourself. It's completely subjective.

brucek

**Wayne A. Pflughaupt** · **03-05-09, 04:32 PM**

Quote:

mlmore wrote:

Do you think I should be accentuating the lower frequencies (20-40 Hz) a little more?

What brucek said. With the relatively flat graph you have now, it would probably make things sound unnaturally "heavy" and overpower the mid and upper bass, but it never hurts to experiment.

Regards,
Wayne

**JimP** · **03-07-09, 01:00 AM**

Sounds like you have a simple case of cancellation because you don't have the correct setting for the subwoofer distance. What's happening is that once you add your mains to the mix, the frequencies at and around the crossover region are out of phase with the subwoofer.

Thing to do is to keep adjusting (usually increasing) the subwoofer distance till the frequencies at and around the crossover frequency is peaked. Some recommend that you adjust till its flat but I think that might actually not be correct as I've tried both and prefer the former.

Once peaked, you can rerun EQ for any out of wack peaks.

Although sub boost is personal, I've found that if you overdo it, a lot of stuff sounds muffled that shouldn't. Its actually weird in that some people talking.

I use a house curve which makes it kind of hard to say how hot I run the sub. Probably no more than 3 dbs. I'd recommend to gradually adjust the sub level in your AVR till most programming sounds right. Avoid TNT when doing this test as they have bass boost on a lot of their programming.

**JimP** · **03-07-09, 01:01 AM**

If you get a chance, can you run a waterfalls chart of your dual sub installation?

**mlmore** · **03-09-09, 04:33 PM**

I added a house curve this weekend and the difference was very noticable. I didn't spend much time with it so I'm sure I can do a better job, but I like the results so far. Here is a waterfall of the response:

Name: waterfall.jpg
Views: 99
Size: 136.2 KB

Name: waterfall.jpg
Views: 99
Size: 136.2 KB

I did try add distance to the sub to correct the x-over dips, but no luck.

**hjones4841** · **03-09-09, 06:03 PM**

If you can fit bass traps into your room you will notice a significant improvement in bass clarity. You mentioned that boominess bothers you - traps can help that a lot. Boominess is not only a function of frequency response - it is also a function of the decay time of the bass in your room, what folks here call "ringing."

From the look of your waterfall, you have ringing due to room modes (resonances due to room dimensions) at the 50, 70, and 100Hz ranges. The 70 & 100Hz ringing will respond with a moderate amount of trapping. The 50Hz one will take quite a bit more - the lower the frequency, the more difficult it is to obtain absorption.

Traps can be bought or built yourself. GIK, one of the forum sponsors, makes very well built traps for reasonable $s. I have 7 of their Monster traps in my room and others have had good success with their 244 traps. The difference that traps have made in my room is amazing.

If you want to DIY, there are plenty of examples on this forum. Most folks use Owens Corning 703, 705, Roxul, or rock wool. Density of the material used and front-to back depth are important.

**JimP** · **03-09-09, 06:18 PM**

Now tell him how large the traps would have to be for those frequencies.

I still think he's got timing issues running multiple subs.

**mlmore** · **03-09-09, 06:33 PM**

I have several GIK traps in my room already. And yes, the very low frequencies would require traps too large for my wife's approval.

**hjones4841** · **03-09-09, 07:14 PM**

Quote:

JimP wrote:

Now tell him how large the traps would have to be for those frequencies.

Well, floor to ceiling in all 4 corners, 12-18" deep would be a start

I looked at his earlier posts and did not see anything about traps, so that is why I suggested it.

**JimP** · **03-09-09, 08:46 PM**

Quote:

hjones4841 wrote:

Well, floor to ceiling in all 4 corners, 12-18" deep would be a start

I looked at his earlier posts and did not see anything about traps, so that is why I suggested it.

....and his wife will

Then again, that's not the problem he was complaining about in his first post.

If your sub's response curve drops at the crossover region when the mains are added to the mix, then he's getting cancellation due to an out of phase condition.

Mimore....with subs and mains connected, adjust your subwoofer distance in your preamp/receiver until the crossover region peaks.

Although you can do this running sweeps in REW, you can also activate the signal generator set for 80hz and activate the SPL meter(either the one in REW or an external one if you prefer). While adjusting the sub distance, peak SPL.

Advertisement