Tempest In-room Frequency Response - Needs BFD ? (1 Viewer)

[Joe Mihok]

Excellent, I do have Star Wars EP2. I'll have to spin it as soon as I get home.

I guess I'm lucky in the fact that my HT is on the second floor. The floor shakes very easily when one walks on it. The Tepmest makes it feel like it's gonna literally cave in. By the sounds of it, your HSU is doing the exact same thing (and with concrete which is amazing) so you know what I'm talking about. I'll never settle for anything other that "room shaking bass" again. Those guys with mulitple SVS subs must be out of their freaking minds. And the guys with the B4's .... well, they belong in the psych ward .

I got people coming over tonight for a "movie night". It will be their first time hearing my sub with the EQ. They always thought my sub was mind blowing before ..... I can't wait to see the looks on their faces now . Can anyone recommend some good "earth shaking" movies for us to watch ? Something new is preferred as we've already seen almost every bass intensive movie out there.

 

[Joe Mihok]

Thanks for the suggestion Mark. I was gonna do that to the 25hz frequency but setting the bandiwth to 1/3 @ 20hz on the BDF seemed to increase the 20-35hz region nicely. I'll also try what you suggest on another preset.

Another quick question. the only thing I'm still confused about is the "bandwith" setting on the BFD. While I know what is does, I don't quite know what setting to use. So far I've just been using 1/6 with the exception of the 1/3 @ 20hz. Can someone use an example ? Say I set a filter at 30hz with a 1/3 octave and a +5 gain. What frequencies would it also affect ?

 

[Mark Seaton]

An important part is to keep the transition between your mains (center channel is most important) and your sub to be a smooth and seamless as possible. That doesn't mean you can't have a general, shallow rise to the response through this range, but smooth response at this point is key to getting rid of the subjective "boom."

Also, in your surround setup, try telling the system that your subs is 1-4 feet further than it is in reality the EQ adds some latency (time from input to output) and there are other electro-acoustic factors which effectively "delay" the subwoofer such that you need to compensate for more delay than the physical distance would suggest.

As a final bit, what amp are you using to drive your Tempest? and what is the tuning frequency of the box?

 

[Brian L]

I am a BFD nOOb as well, but here's my take on octaves.

Using you example of 30 Hz, one octave lower is 15 Hz and octave higher is 60 Hz. That part I know is correct. The next part I believe to be true but will not be insulted if someone corrects me!

If you had a filter set with 1/3 octave width, that would be 1/3 of 15 Hz on the low side, and 1/3 of 30 Hz on the high side. So, the filter would cover 25 Hz to 40 Hz. Thats a pretty wide filter, IMHO.

Now, the art of setting a BFD is that, if you have peaks that do cover a wide range, a single filter of the correct bandwidth can deal with it.

But it does take some practice. As suggested in the BFD set-up guide, you probably want to use a a fairly narrow filter. I actually went with brute force over finess, and use 11 filters at 1/60th bandwidth (a setting of 1 on the bandwidth control).

Here is something else to be careful of with the bandwidth setting. If you have filters that are set such that there frequency centers are pretty close (I use close to 1/6th octave spacing), but then set the bandwidth to be wider than that, the filters will overlap. And if you do that, you can find that you are either boosting or cutting certain frequencies by more than you intended.

For example, if you had to filters that each were boosting by say +5dB, but their range overlapped, the overlapped frequencies would in fact be boosted by +10. Lets just say that I am in the "been there, done that" category.

BGL

 

[Joe Mihok]

The box is tuned to adires specs at 18.8hz. The amp for the tempest is my Retired Kenwood AVR. It's 100 watts per channel and I'm using both channels to power the tempest. Right now the Kenwood is set to -8 for gain.

My main AVR is a Denon 1804. There is no option to set my sub distance. Just mains,centre, and surrounds.

 

[Joe Mihok]

Brian - That makes crystal clear sense (if no one corrects you ). Thanks a bunch .

 

[Brian L]

This is the one part I am not certain about. That would make a given filter asymmetrical, and I am not sure if it does that or not. I do know that an octave is 1/2 or double a given frequency, but when one says "1/3 of an octave", I am not sure how that is applied to a given center frequency.

But since I dumb it down by working with 1/60th of an octave bandwidth, I avoid the problems that my ignorance could reveal!

But either way, I think the rest of my bandwidth explanation is fairly accurate.

BGL

 

[GrahamT]

Well prepare for the insults Brian!! Just kidding, that is the way I think it works too, at least it is a close enough method for the BFD.

Joe, by moving the sub or the listening position you may be able to get rid of that null. If not maybe look at diy bass traps.

 

[Wayne A. Pflughaupt]

You guys really need to deal with whatever’s causing your ground loop instead of taking this approach.

Regards,
Wayne A. Pflughaupt

 

[Joe Mihok]

Okay, I went home for lunch today and added a filter for 25 hz (+5 boost) and tweaked some other filters to make the response.

I took measurments with the BFD in bypass mode, and the other with filters active. The "bypass" is blue, and the "filtered" in pink. Here is the screencap:



Any comments ?

I can't seem to get rid of the null at 36hz and 57hz ....

 

[Brian L]

Well, lets just say that, since it was my first pass with the BFD (and I had a limited amount of time available for tweaking), I opted to go for the approach that I thought I understood best. And it did work beautifully, once I narrowed the bandwidth.

When I ran the test tones after the first round of adjustments, I was pretty surprised to hear that a bunch of my frequencies were boosted by at least twice what I had dialed in. Dohhhh!

But dialing the bandwidth back from 15 (15/60 or 1/4 Octave, right?) to 1 (1/60th octave) solved that problem.

In any event, I am going to use it to EQ my second sub (currently off line). I can try to be a bit more sophisticated on round 2!

I hear what you are saying WRT ground loops, but from my first sub, it always seemed that I would need to lift the ground or the sub would hum. Even with no input cable, my subs have hummed.

Given that the sub (a Klipsch SW8) actually came with a 3 prong adapter, I assumed that it was SOP, and did not question it.

But given the complexity of the rig (6.1 Channel AVR, Audiocontrol Bijou, BFD, stand alone DVD player, DVD-A/SACD player, ICBM, HDTivo, VCR, CD-R Deck, DVD Changer, two powered subs) I expect that I have no shortage of possible sources for the hum. And let me assure you that the back of my rack would make a really good "before" candidate for someone selling wire looms that wanted to do a before/after picture.

Calling it a Rats Nest would be insulting to Rats Nests everywhere.

BGL

 

[Wayne A. Pflughaupt]

That’s cute, I like that. Despite what everyone says, though, as long as you have good-quality cables with adequate shielding, you’re fine. I’ve seen a lot of people here chase down ground loops over the years, and I’ve yet to see someone nail it down to, “I didn’t have my cables in my rack routed properly.”

Regards,
Wayne A. Pflughaupt

 

[Joe Mihok]

ignore this post. i answered my own question .

 

[Joe Mihok]

Same here. My cables are all high grade coaxial with gold connectors. The problem is my sub being so close to the BFD. I move the BFD away from the sub (10 ft), and I get no hum.

 

[Joe Mihok]

Upon viewing again, I could probably just start from scratch and just filter 45hz and 73 hz with tighter octaves and bring things down nice. I think I'm using too wide a bandwith and I'm making my nulls even worse. Man this BFD stuff is fun. I love playing with my toys and this thing really lets you experiment.

 

[Brian L]

A couple general comments.

In many cases, a null is not really a null (and area of cancellation), but just a valley between two peaks. As such, combing some attenuation at the peaks with some boost in the valley can often flatten things out pretty well.

If I was faced with your Blue trace, I would probably start by drawing an imaginary horizontal line at about 94 dB (perhaps a dB or two lower), and try to dial each of my test frequencies up or down to that value.

Ignoring Wayne's sage advice to use the bandwidth control to my advantage, I would probably just take the 1/6 octave tones from 28 to 80 Hz, and see what I could do with those.

On second thought, a 45 Hz frequency with a 1/6th octave bandwidth should be able to take down the peak at between 40 and 50 Hz pretty well.

I am curious to see what the master will prescribe!

BGL

 

[Mark Seaton]

Indeed, quite often you are better off starting over with a better idea of your final target. I would also start by not touching anything below ~30Hz until you get the top end looking like you want. Then you could play with a little boost around 20-22Hz.

For low frequency EQ, you generally will want narrower band filters unless you have multiple problems building up. I would also suggest you look at the 40-80Hz range and check the response around your seating area to see if the peaks or dips are less. Finally, is this measurement with your main speakers connected as well?

Yes, if you start really looking at the many interactions going on, you will find a whole new world of learning and adjusting. One thing is certain... These tweaks are much cheaper than the ones sold at the local boutique stores, and are much more effective!

 

[Wayne A. Pflughaupt]

That’s the ticket – keeping in mind the probably overly-wide reaction area and watching those fringes (36Hz and 60Hz in this case).

Regards,
Wayne A. Pflughaupt

 

[Joe Mihok]

Ok, I moved the sub into the opposite corner (now the right side instead of the left) and things sound just great. Let me know what you think. I added a small boost at 25 hz (1/3 octave bandwith):



IMO, a BFD is THE most important thing for any sub. I don't think any sub/room is perfect. The difference is night and day when I switch between "filtered" and "bypass" mode. Thanks again to everyone who's replied in this thread to help me out .

 

[GrahamT]

Great job with the BFD. I knew you would like it I feel the same way about it. Now you can start to fine tune different programs for music and movies. I have dozens of different programs and find that I like flat (like your graph) for music and a "house curve" for HT. Wayne has made some very helpful posts on implementing a house curve.