Subwoofer calibration/equalization

[genesis471]

Hi,

Just wanted some feedback of the changed frequency responses in my ht room. I used the RS SPL meter, as well as the BFD DSP1124P. The blue line is what I started with, the pink is what I ended up with after some work. I have the Denon 3805 with the sub crossover set at 80hz, speakers on small, my M&K sub at about 1/3 to 1/2 volume, with the phase on +, the crossover on the sub all the way up to 150hz or whatever is was.
I guess the question is, do my settings look acceptable? I won't be able to really crank it up and listen to it until tomorrow since the kiddy's are asleep now. But at lower volumes, it sounds better then it did.
Tomorrow I am also planning on tuning the rear sub.
The M&K is up front next to my front left main. It is in cabinetry and I've been working hard at trying to get it to sound good. I've insulated the death out of the cabinet and the sub fits tight (sub-amp is on outside of cab).
I was struggling trying to flatten the FR until I read that I should have the crossover on the sub all of the way up. I was under the impression that it should be on 80hz to match the receivers crossover. Fixed that and now it was easier to tune. I just hope it is in the ballpark.
Thanks for any feedback!

Mike

 

[mike c]

why does it say HGS-15?

 

[corey]

Just in case the "pros" don't reply: it works for me.

 

[Buckle-meister]

Just wanted some feedback of the changed frequency responses in my ht room.

Hello Mike.

It's entirely possible that I'm missing something here, but if I read your plot rightly your BFD has boosted the frequency response by more than 15dB at 56Hz. Now 56Hz is a fairly low frequency and the amount of power required to add 15dB would, I believe, be enormous since an amplifier must double its power output to deliver just a 3dB increase in volume. For this reason, it's generally not recommended to raise frequency response by more than a couple of dBs so that you don't:

1. Overtax your amplifier beyond it's limits and/or;
2. Cause excessive driver excursion from your speakers.

Like I said, maybe I'm missing something, so hopefully others more knowledgable than I can confirm this one way or the other.

 

[shokhead]

Hi,

Just wanted some feedback of the changed frequency responses in my ht room. I used the RS SPL meter, as well as the BFD DSP1124P. The blue line is what I started with, the pink is what I ended up with after some work. I have the Denon 3805 with the sub crossover set at 80hz, speakers on small, my M&K sub at about 1/3 to 1/2 volume, with the phase on +, the crossover on the sub all the way up to 150hz or whatever is was.
I guess the question is, do my settings look acceptable to the pro's here? I won't be able to really crank it up and listen to it until tomorrow since the kiddy's are asleep now. But at lower volumes, it sounds better then it did.
Tomorrow I am also planning on tuning the rear sub.
The M&K is up front next to my front left main. It is in cabinetry and I've been working hard at trying to get it to sound good. I've insulated the death out of the cabinet and the sub fits tight (sub-amp is on outside of cab).
I was struggling trying to flatten the FR until I read that I should have the crossover on the sub all of the way up. I was under the impression that it should be on 80hz to match the receivers crossover. Fixed that and now it was easier to tune. I just hope it is in the ballpark.

[/IMG]

Thanks for any feedback!

Mike

I'll reply even though i'm not a pro. I've got my x over on 60Hz on my 2805 because it blended better with my mains. Setting it on 80Hz was more noticable when it went from the mains to the sub, a bit more of a ledge. Its really up to your ears,not the way we might do it. BTW, i used Avia.

 

[sivadselim]

why does it say HGS-15?

Because that's what whoever made this spreadsheet that everyone uses to graph their sub measurements, used.

 

[Buckeye_Nut]

Boosting frequencies by EQ'ing to treat nulls a big no-no.

 

[genesis471]

Thanks for the replies. I did boost some of the nulls (obviously), but didn't know much better. I can and will dial those back to what they were at and only focus on the peaks. I assume I should be needing room treatments to help with the nulls?
No worries for those that aren't 'pros', I just say I'm asking for help from the pro's because most here are better eduacated then I on the subject matter!

EDIT: Reduced size of picture in post 1.

 

[genesis471]

Hello Mike.

It's entirely possible that I'm missing something here, but if I read your plot rightly your BFD has boosted the frequency response by more than 15dB at 56Hz. Now 56Hz is a fairly low frequency and the amount of power required to add 15dB would, I believe, be enormous since an amplifier must double its power output to deliver just a 3dB increase in volume. For this reason, it's generally not recommended to raise frequency response by more than a couple of dBs so that you don't:

1. Overtax your amplifier beyond it's limits and/or;
2. Cause excessive driver excursion from your speakers.

Like I said, maybe I'm missing something, so hopefully others more knowledgable than I can confirm this one way or the other.

Thank you for the advice Robbie. This seems to be consistent from other posts that I have read. I'm trying to gain a better understanding of all of this but I'm such a novice!
I am going to the HT room after this post to pull the gains I put in the BFD and remeasure. I will post the graph when done.

Mike

 

[genesis471]

The latest. As you can see in the lower left hand picture I pulled filters 5, 6, 7,and 8.

 

[Mark Seaton]

The latest. As you can see in the lower left hand picture I pulled filters 5, 6, 7,and 8.

Hi Mike,

I guess I've been paid to do this once or twice, so I guess I'm a pro.

I would suggest that the best solution will be somewhere inbetween the two curves you have posted. Since you don't have the option of moving the sub, I would suggest looking at how much you can EQ the recession in the 50-80Hz range while still maintaining acceptable headroom and good sound.

I would first take some additional measurements across/around the listening spot. Since you have to measure each frequency individually, you can probably just take a look at the frequencies above 40Hz for comparison. This will show you how consistent the response is in the area you listen from. If the valley is there in all of the measurements, I would suggest applying some EQ. Try using two filters spaced out that both boost maybe 4-5dB. Instead of making them very sharp to try and match the dips, ignore the two severe dips and envision a smooth curve that stays above the little peak near 60Hz. You might want to start with only one filter for that area. Without making the response more ragged, try to bring that saddle point near 60Hz within 2-3dB of the level at 90Hz.

The short explaination of the above is that you do want to address the overall dip in the response, but often you want to leave sharper dips alone as that can cause other problems. Look for a smoother, broader filter shape to best fix the trend of the problem, not an exact match.

 

[jmprader]

A few thoughts, from a non-pro with some recent (and ongoing) hands-on experience.

1. Though lacking his credentials, I agree with Mark Seaton. A little boost is probably an ok thing, especially if you don't typically rock the house.

2. When you add the second sub, you may be able to improve the overall results. Even if moving the subs isn't an option, eq'ing the second sub will create an additional opportunity to reduce the nulls in conjunction with Room eq wizard. Caveat: the process can get perplexing for those of us whose higher math wasn't required for our career path...

3. I don't know anything about your mains, but you may want to run some plots on them. If they have decent output the next octave down and their FR curves don't result in the same null, consider a lower x-over.

4. Dealing with FR issues in the low bass is difficult with room treatments, but I'm getting some clear benefit from experimenting with acoustical cotton in the corners/at vertices. Lots of SAF factors, but it's not extremely expensive and may improve SQ at higher frequencies as well.

Good luck, hope to see some more graphs/comments on your project soon.

 

[genesis471]

Thanks to both Mark Seaton and jmprader on the last two posts. I will work on this a little at a time and post new graphs. I appreciate the feedback and ideas that are presented.
I'm not certain I mentioned it but the graphs are for the front sub in the cabinet. The second sub in the back isn't even the equasion yet. I know the second sub will help tremendously for movies also. But I don't really like the second sub on for concerts as an example, because I like the stage in front of me if that makes sense. So I'm trying to get the front one to sound good for music.

Thanks!

Mike