Another BFD story - SVS PB13 Ultra

[kexodusc]

I remain convinced the Behringer Feedback Destroyer is the single biggest bang-for-the-buck investment that any system with a subwoofer (music or home theater oriented) can enjoy.

I convinced a friend to buy a Behringer Feedback Destroyer to go along with the subwoofer he's had for a few months now that was disappointing him somewhat. It's and SVS PB13 Ultra (hope I have the model letters right) and I believe he paid around $1500 for it.

Wasn't that the sub was bad (it's actually pretty impressive) but he knew nothing of room acoustics.

For those of you who don't know the, the Behringer Feedback Destroyer is an inexpensive device HT buffs use for its parametric equalizer feature.

Anyway...long story short, he had peaks in the bass as high as +15 dB from his reference point and some annoying dips too that lead to the bass sounding thin in some areas.

(I'm uploading a graph that will be available shortly to help show what was going on in his room....)

[kexodusc]

<a href="http://picasaweb.google.ca/lh/photo/OyCi2uHqtVghSUMlmOEExw?authkey=Gv1sRgCK2T4tf95YW3l QE&feat=embedwebsite"><img src="http://lh5.ggpht.com/_yDwIo198iNI/SqJdY8XD1QI/AAAAAAAAAjQ/5n6gi7vXjWo/s800/BFD3.jpg" /></a>

(sorry for the pic quality...technical difficulties with Windows)
The dark line represents the before EQ response, the pink line is the after (more on that later).
You can see the broad peaks between 40Hz and 65 Hz or thereabouts...he had set his sub to match with his mains based on some 30-40 Hz test tones, and by ear I guess. This big peak was 10-12 dB higher than that, so he adjusted subs level to bring it down...but then it left out out the rest of the frequencies. I estimated the response to be about +/-10 dB. You wouldn't own a speaker like that...why settle for bass response that terrible?
He was actually convinced this unit was a dud and that he got hosed. It wasn't until I convinced him it was a room acoustic issue that he bougth into the idea a small piece of equipment as ugly as the BFD could help.

His room for whatever reason resonates in a way that doesn't present relative big dips or suckouts in the bass response (they are there, but masked by the peaks, and not as bad as most rooms I've seen). After a few hours of trial and error we were able to just use 3 filters to achieve the pink line response you see. From 16 Hz to 30 Hz or so, we incorporated a slight boost (actually appplied less "cut") to have the resonse rise intentionally. This is to compensate for the human ear's reduced sensitivity to these frequencies, and give a little more rumble to movies (he de-activates it for music sometimes). The graph shows the reference level of the pink line to be around 80 Hz...+/- 3 dB pretty much the whole way from 25 Hz to 120 Hz. That's pretty good for an in-room response. He's going to tweak and I have no doubt he'll be able to do much better still. It's already better than I've been able to reproduce with my own room's acoustic challenges.

A good lesson for beginners here..take a look at the black curve's suckout between 70 and 125 Hz...this was mostly do to phase issues between main speakers and sub. It was resolved by using the phase controls until the SPL meter showed they were working together instead of against each other, cancelling out. Sometimes the dips in bass response are the biggest problem. You don't hear omissions in sound as much as loud offenses (peaks), but you'll recognize something's off when the bass sounds weak, thin, less punch, or whatever words you want to describe it.

The sub sounds fantastic now. It's an oddball design, 13" woofer...I didn't get to spend much time with in a real review setting so I won't comment much on it...better than I remember SVS, that's for sure. I'll have to go back.

Anyway, if you're on the fence with this item, don't hesitate, just pull the trigger.

[L.J.]

Great post Kex. Best $70 I could ever throw at my system :cornut:

I was definitely intimidated by the BFD (have you guys looked at that thing) but it all comes together once you actually start playing tones and adjusting it. I had some SERIOUS peaks and cutting those down made an easy day & night difference in SQ. My beautiful 15" Titanic actually sounded like crap before the BFD :nonod:

[anamorphic96]

My HSU STF-2 sounded pretty poor as well until I eq'd it. I ended up going with the Velodyne SMS-1 since they are down to 429 at most places. Plus I'm lazy and I didn't want to spend the time with the BFD.

Boy did it make huge difference. The bass is so much cleaner with better definition and extension.

[GMichael]

Hmmmmm... An upgrade I could actually afford. Thanks for the reminder Kex.

[kexodusc]

Thanks for the comments guys.

The graph above doesn't do the BFD justice IMO. This guy has some corner treatment and a few wall panels most people wouldn't have, should have mentioned that. (if I thought about it I should have taken a 3rd plot with the treatment out..damn) So the before curve was already improved somewhat by that. From the start this guy's room is a lot better than some of I've seen including my own, I've seen worse starting conditions that make the BFD even more valuable. Here, the eq'ing still introduced a significant improvement.

Keeping in mind the rising response below 30 Hz was intentional, this is a very accurate FR plot for in-room response, especially with bass. He's probably fine-tuned it a bit more on his own but it was really neat to listen to some tracks with the EQ disabled and then active. Night and day differnece for sure, it's amazing how much more musical the sub became once all the bass notes were audible and pretty equal in volume.

GM, if you can get one used, it's worth the sacrifice. Can't stress it enough.

[GMichael]

Which model is better?

The DSP1124P is $99 from most sources. As low as $70 used.
The FBQ2496 is running $130 on Ebay (new) $120 from Audioline (B-stock)

What does the FBQ2496 bring to the table thats extra? Is it worth the extra cash, or are the improvements only good if I were to actually use it to destroy feedback? Is it easier to use? (I could sure use that)

[kexodusc]

I've never used the newer one, but the DSP1124P is the one endorsed by most still anyway...since it's cheaper, go with that. The HT shack's official BFD guide says the 1124P is the best of the 3...

[Rich-n-Texas]

Beware the dreaded LF hum!!!

[GMichael]

I've never used the newer one, but the DSP1124P is the one endorsed by most still anyway...since it's cheaper, go with that. The HT shack's official BFD guide says the 1124P is the best of the 3...

Thanks.

The limited research I've done so far suggests that the DSP1124P is more flexible, but the FBQ2496 has higher quality components. Whether the increased QC for the parts is incremental or not seems to be an ongoing debate. In any rate, there is more information available for setting up the DSP1124P. That works for me (seeing as I'm cheap as h.ll)

Rich? Is that you Rich? You still around? I thought you ran off and joined a circus or something.

[Rich-n-Texas]

I'm here to keep kex in line.

[GMichael]

I'm here to keep kex's thang in line.

His what in line?!:skep:

[L.J.]

Rich, maybe you should sell your BFD(Cough) to GM. You know you ain't using it.....

[GMichael]

Rich, maybe you should sell your BFD(Cough) to GM. You know you ain't using it.....

Good point.

Rich, I'll send you a couple of phillies for it.

[Rich-n-Texas]

Rich, maybe you should sell your BFD(Cough) to GM. You know you ain't using it.....
Actually joystick boyyy, I am using it and it's working fine. I'm using a cheater plug and I have it plugged into a separate circuit, so I no longer have a problem with the dreaded hum that the Home Theater Shack boys can't seem to resolve. :devil: (I have no interest in hacking up XLR cables).

What I immediately noticed when the hum was eliminated was much more clarity out of my CC speaker. Dialog on TV shows and movies is much more pronounced and lifelike. Don't ask me why that is, but it was definately noticable. And even though I still have a nasty dip at 45 hz, the subwoofer response in my listening area is much improved over what it was previously.

[Rich-n-Texas]

His what in line?!:skep:
:rolleyes:

kex probably lost his "thang" in a hockey injury or something. :dita:

[Luvin Da Blues]

[QUOTE=Rich-n-Texas]Don't ask me why that is, but it was definately noticable.[QUOTE]

Probably due to the 'masking' effect of the 60Hz hum over the lower midrange freqs. Dat's my theory an I'm sticking to it.

[L.J.]

Actually joystick boyyy, I am using it and it's working fine. I'm using a cheater plug and I have it plugged into a separate circuit,

A cheater plug!! Really:confused5:

Can't you just take a pill for that sort of thing :D

[kexodusc]

Guy's...Am I the only one a little worried that Rich is spending time speculationg on the whereabouts and constitution of my "thang"???...

[Rich-n-Texas]

Knucklehead GM, as usual, is putting words in my mouth! :mad:

[GMichael]

Knucklehead GM, as usual, is putting words in my mouth! :mad:

Tex,

At least it's only words going into your mouth.

Kex,

Why should we worry? What Kex & Tex do together behind closed doors is.... well... BFD. But please, no pictures.

[Rich-n-Texas]

Off topic off topic!!! :incazzato:

[GMichael]

Off topic off topic!!! :incazzato:

BFD.......:3:

[kexodusc]

Tex,

At least it's only words going into your mouth.

Kex,

Why should we worry? What Kex & Tex do together behind closed doors is.... well... BFD. But please, no pictures.
Hey I'm pro-love, but there's more to Kex than just his thang...I feel so objectified.

[GMichael]

Hey I'm pro-love, but there's more to Kex than just his thang...I feel so objectified.

I'm sorry Kex. I do respect you very much. I'm sure that Tex does too.