Question About A Possible Design Flaw...

VR3

I'm probally one of the bigger SVS fans yall ever meet, I own 1 of every one of their shirts, a hat, anyone that ask me about home subs hears their name...

But I will have to question their 'design' - a design that indeed does seem flawed to me.

Cof at S&V measured the SVS PB10, he noted that the PB10 had NO internal bracing. Cof measured the subwoofer, and noted that there was an incredibly long 'time delay' (I think that was it) - and he added weights to the enclosure, and the time delay calmed down incredibly, this could be solved by one or two internal braces.

With the PB10, no bracing is understandable... It is a budget subwoofer, basically geared for HT, Cof noted it had a boomy sound to it, and adding the weights cleaned it up considerably...

Then Early B noted that the PB12 ISD didn't have bracing either...

So now I wonder if ALL of the box subwoofers don't have any bracing?? Is this just a way to save cost, or do they REALLY not think that it is needed? Obviously if the enclosure is changing the sound on a smaller model, the bigger models with bigger enclosures and drivers are going to be altered even more!

Does anyone have any info on this? Do the larger/more expensive box subs have bracing or not??

This isnt meant as a bashing or to start a fight of any kind...however...I want to know the skinny!

Early B.

My guess is that it's a cost and weight consideration. Seems that the larger SVS box subs are braced, though. I copied this statement from a review...

The PB12-Ultra/2’s enclosure is made of heavily reinforced, 1"-thick MDF. SVS states that internal bracing "stiffens things up without adding too much weight,"

I wonder what type of performance enhancement I could gain by adding bracing to my SVS PB-12 enclosure. Tight bass, less boominess, perhaps? Hmmm. I guess the first question that needs to be answered definitely is whether internal bracing is even necessary in these "small" subs.

FWIW, my Onix Rocket UFW-10 isn't braced either. Anyone know if the Hsu box subs are braced?

VR3

If you knock on the side of your subwoofer, and it makes any kind of noise other than a 'thud' - or like a 'resonance' of any kind... another way is to play music and see if it noticeable flexes with your hand on it, particularly in the middle of the enclosure - then it needs to be braced...

I figure in a 2 foot deep enclosure, I'd put atleast a horizontal and vertical brace...

This would help it out ALOT...

Wouldnt be THAT hard to add, cut it to size, drop it through the woofer or amp hole... drop it in place - put glue on the ends before dropping it in, or put glue around the edges after putting it in...

I doubt you'd want to run screws through your subwoofer...

Bracing is very important with subwoofers, only sub I can think of that could get away with it is those small cubes...

SVS drivers move ALOT, even the ISD driver moves 2" linear...

That enclosure will flex like crazy with no bracing, imo

If the PB2 Ultra or w/e is the only box sub braced, that is kind of scary..

The PB2+ has dual drivers that move like 2.5+" linear... jeeez

faster100

I have the original Pb2-isd before they changed the names... and ive had it pumpin, and it doesnt resonate or flex.. 2- 12" woofers at half volume would cause something if it were to ever.. I now feel however that these huge subs are geared towards more the ht side.. it sounds ok for music but i now listen to all my music on my 2 channel rig with no sub on sda 1's.... i never thought it sounded boomy either... i also had the original pb1, that i think sounded better on music then the 2 and shined on HT as well...

VR3

Shot in the dark here...

But [maybe] the leading cause to the PB2 ISD NOT being good at HT could be the fact that it does indeed need bracing (ever open it up?) - I dont know if it has it or not... (just pondering)

I've found that my sub is extremely easy to dissapear, even at higher volumes...

Cylinders don't need bracing, at all...I love that part...LOL

So, I wonder...does the PB12 ISD sound different than the PCi 22-31??

I wonder if anyone would be willing to run tests with 50 pound weights on top of their sub and maybe some draped over the side (with a towl over your sub of course) and running FR sweeps before and after...

dorokusai

I know mine is braced.

Early B.

I've found that my sub is extremely easy to dissapear, even at higher volumes...

Mine is easy to locate...sittin' right next to it:p

Sid -- e-mail Tom at SVS and see what he tells ya.

PhillyDan1969

I recently ordered the SVS PB10 ISD and I was wondering what is the best way to add weight as you mentioned to this sub?

faster100

Originally posted by Vr3MxStyler2k3

But [maybe] the leading cause to the PB2 ISD NOT being good at HT could be the fact that it does indeed need bracing (ever open it up?) - I dont know if it has it or not... (just pondering)

If this was meant from my answer, MY pb2 isd is Great at HT and to much for music IMO... Mine doesnt rattle.... it sounds great. I have no desire to open it up either...

But what do the sub pro's know anyway(SVS) I'm sure we could all redesign the box better... LOL

VR3

Originally posted by PhillyDan1969
I recently ordered the SVS PB10 ISD and I was wondering what is the best way to add weight as you mentioned to this sub?

You'd have to ask COF over at S&V how he did it, it dosnt look very good.

The best way to do it is bracing, but that is hard to add with a sub that is already built...


I know SVS knows what they are doing, seems the dual sub box subs get bracing, where as the single sub box subs dont...even those enclosures are big...

Whadyasay

You can look at it this way...with all the attention to detail and performance SvS puts into their subs, do you really think that a design feature like this would be so glaring a mistake? Aside from keeping the costs down...if they felt that lack of bracing would so muddle up the sound, I doubt they would have approved the design and went forward into production with the unit. I think the design is just fine the way it is, and you're still getting one heck of a sub that clearly blows away anything in its price range.

PhillyDan1969

I did a ton of research before buying this subwoofer and I don't think there is a better choice at the $400 price range when it comes to subwoofers for home theater. I am fairly certain from SVS' reputation among people on these and the forums for Audioholics that I made the right choice.

goingganzo

heck my syb moves my wall and the wall behind it. i even braced it up with some 2x6 but it still moves.

Dr. Spec

I would ask SVS if current production PB10-ISDs are braced.

An ETC (energy/time curve) that shows a change at the -35 to -45 dB level (relative to the signal strength) is very likely completely inaudible. The most respected audiophile mag in Europe evals spectral decay to -25 dB. I run it to -35 dB and that's pushing it.

I think COF/IG did a really good job on the PB10-ISD review. But the proper way to evaluate mods is with blind testing, where he wouldn't know which version (braced or unbraced) is playing. AFAIK, he never conducted any blind testing.

If someone can tell the difference 8/10 times in blind testing, it's considered reliable. If the results approach 5/10 over time, the listener is guessing.

kingtut

Originally posted by Early B.
... Anyone know if the Hsu box subs are braced?

My VTF3 MKII is braced. I don't believe the STF2 is braced.

rkn2903

My Paradighm PW2200 V.2 is braced. I guess bracing the sub makes it perform a little better.

Early B.

Don't let this thread die yet.

Like Sid, I'm interested in getting a more definitive answer on the bracing issue. Just wondering whether or not bracing is a cost/weight consideration or are the "smaller" subs designed in such a way that they don't need any bracing at all?

I'll e-mail SVS and ask them. Stay tuned.

VR3

There is no way to bypass bracing in any type of sub in ones the size of SVS subs, period... maybe their smaller cube subs...

But anything over 12" should have bracing vertical and horizontal - atleast in the center...

These are -huge- subs... and they need bracing... I saw a pic of marks PB 2 ISD/2 (or w/e) and it has a vertical brace...but no horizontal brace... thats not good enough (IMO)...

So yes, I am curious as to what they tell you.

Early B.

OK, here is SVS's response:

"The panel size (area of each wall of the subwoofer) is small enough not to need bracing. We use 1” thick MDF for the walls…which is about twice as strong as the ¾” thick walls most subwoofers use in this price class..:)"

I guess we should infer from this response that bracing is not necessary for the PB10/12's. Cool.

BTW, a very quick response from SVS as usual.

VR3

Note, the PB10 uses 3/4" MDF on the sides/top/bottom/back, the front only utilizes 1" MDF

The PB10 definetely needs it, COF confirmed this with listening tests... now whether its noticeable as Doc mentioned above...thats another story

Interesting response though

Curious though why the dual subs only have a vertical brace, and not a horizontal brace since the walls are the same depth

Mjr7531

Perhaps it is because it would be too difficult to implement effectively, while being cost effective at the same time? what type of bracing are you speaking of? (sorry I kinda skimmed this one)

VR3

Bracing isnt as complicated as it may seem, a vertical & horizontal brace (3/4 wide, thick, height of cabinet/width of cabinet) can do wonders...

Dr. Spec

The PB10 definetely needs it

I'll repeat my question.......has anyone asked if the current production PB10-ISD is braced? Manufacturers often make running changes/improvements to products without much fanfare or notice.

Early B.

I'll repeat my question.......has anyone asked if the current production PB10-ISD is braced?

Someone on this board who just bought a PB10 -- help us out by opening her up and inspecting her guts, then let us know for sure. Just unscrew the woofer (or amp), pull it out and peek inside. That's it.

On a side note, I also like to know how much insulation it has. My PB12 only had a smattering of fiber insulation in it (like the stuff in your attic).

Thanks.

VR3

Insulation is in there to help make the box bigger, I believe SVS put enough in there to get the enclosure to the appropriate volume...

Not sure canceling out the backwave in a subwoofer would do to much (might) -