Tuning SVS Subs to lower Hz vs not tuning (1 Viewer)

I've seen that you can tune the SVS subs or have them tuned if not a + version. What I am wondering is why you wouldn't tune for the lowest hz possible as it seems to me that this would give you the best bass. What am I missing here?

That really depends on the size room your in. If you want it toplay louder but not play as "low" you leave the ports all open. You can tune it down to the lowest by adding the port plugs but your always going to lose volume on it.

It can be personal taste as well...I tuned my 20-39PC+ to the 16hz setting and really didn't like the way it sounded in my living room...so I just left all the ports open which makes it play louder in my living room and still gives me the low end...not as low as 16hz but it goes low enough for me!

The bigger room you have the more likely it is you'll leave all the ports open.

I'm currently having a house built so I'm trying to find the correct sub for it. Once I get my floorplans from the builder I plan on asking here and Ron @ SVS which would be best. It's a fairly open floor plan though so I'm expecting to need a large sub which is fine by me

With what you said I would probably want a higher Hz tune but I will definitely want to get a plus series so I can test it out to make sure I get the best sound.

Thanks for the help!

you give up overall output at the expense of the extra extension

Something that I dont understand on the cylinders is this... If you can tune any cylinder to 16hz....why pay the extra money for the 16-46 instead of getting a 23-31 or the 39" cylinder and having it tuned at 16hz? Seems like same product but cheaper. Am I missing something here?

Its a compromise between bass depth or SPLs. The question is which has higher priority: Bass depth or louder SPLs. If we go with one, we lose on the other.

I have this gut feel that if we tune a 25-31+ to 16hz, we will lose so much SPLs that the compromise isn't worth at all. A 25-31+ tuned to 16hz will not have as much SPLs as a true-bred 16-46+.

I'm going to try to expound upon Ming's post. What you're missing is the overall SPL capabilities of these subs in their native tune points.

A 25-31 PC+ can be tuned to 16 Hz. The 16-46 is natively tuned to 16 Hz. If you plug two ports on the former to achieve the same tuning as the latter, you sacrifice headroom, and you do it for those last Hz where less material is available. If you are a big pipe organ fan, the 16-46 is probably your better choice. If you're a hip-hop fan with a large room, then you're best choice is probably the 25-31. There are advantages to both, but your primary needs, room size, and budget all need to come together to decide the best choice for you. The 16-46 will fill a larger room than a 25-31 with two ports plugged, but a 25-31 with no ports plugged will play louder (from 25 Hz on up) than the 16-46. I'd be willing to bet the 20-39 is their most popular cylinder for the reason that it meets the middle ground of these needs.

-Robb

Ming pretty much nailed it.

If you are unconcerned about cost or size, and have a good idea about the sort of extension you want (another way of saying how deep a sub goes) ... based on the sort of program material you like*, then ideally you get the cylinder (only Plus and Ultra SVS cylinders are "tuneable") that best suits your tastes, without regard to varying that tune. (Each SVS cylinder has a character of its own, but they are really shades of gray.)

So if it's a PC-Plus sub, pick the size that's going to work best for your needs, and run with the optimal three ports if possible; after all they are already tuned to just the right frequency for that given enclosure size.

But some people ARE concerned about size, or cost, or both. Or simply want to experiement with a deeper "tune", understanding that you do indeed trade off some upper bass capacity with deeper frequency response.

The long and the short of it is, a 25-31PC+ that's running far less enclosure space, and only one 3" port will mimic the frequency response of a 16-46PC+ with all its ports open, but it will not match the big SVS's efficiency or overall output over its operating range.

This is one reason the 20-39PC+ is such a popular seller. Out of the box, with corner placement in a mid-sized room it will be very very strong to around 15Hz or so. That's in its most efficient mode (20Hz amp setting, no port plugs). But if you find you have far more bass headroom (think of this as unused "volume") than you need, dropping in one port plug and flipping the amp's tuning knob to 16Hz provides still more depth (approaching 12Hz).

There's no free lunch with subwoofers or physics. There is indeed more stress on the woofer in anything but the "native" tuning frequency of any given size SVS cyinder. If you aren't pushing the sub to its limits in the first place though this ability to drop the response is pretty handy for those desiring such flexibility.

Hope this helps some guys.

Ron

* What sort of size SVS might you shoot for even if it's a variable sub? Or doubly if it's one of the PCi Non-variable subs?? Someone that's a hard core rock/pop/hip hop music fan that's only secondarily into movies is best served with a 25-31 cylinder. A mix of movies and music? The 20-39's are our switch hitters. Want to troll the absolute depths of movies, pipe organ or other ultra low stuff and aren't looking for the n'th degree in sheer output in more common bass ranges (call it 30Hz and up)??? The 16-46's are your bag baby.

Again, each of these categories can be "bent" if size or cost is an issue and you are getting a variable tune "PC-Plus". Keep in mind though that while dropping down the tune one setting (to 20Hz if it's a 25-31PC-Plus for instance) is no problem, but doing it TWO steps limits the sub's headroom/efficiency to a greater extent.

I see Ron was posting at the same time I was, and lo and behold, one of the SVS founders said it better than I ever could! Go figure...

-Robb

I hear you Robb. Glad I checked before I posted myself.:wink:

Just out of curiosity, how would running a 16-46PC+ AND a 25-31PC+ at the same time sound? My noob guess would be that it would sound great but kinda look silly in the room?

it'd probably sound awesome, especially if you could tune the 16-46 to it's lowest tuning (is it 12Hz?), yet have it still keep up with the 25-31. may require 2 or 3 16-46's in this configuration, to keep up, though, depending upon your headroom requirements.

Interesting question Jon W. I'm wondering where to go from a lone 16-46PCi myself. My wife is demanding ever more headroom on rock music in our 30 foot room! :b

I'd also be interested in hearing opinions on how an Ultra driver would perform in a 16-46 cylinder. Since it's 'native' enclosure is the 20-39. Of course the PC Ultra uses a more powerful amp as well. Do you just get louder organ music with a bigger cylinder?

Also, the question of multiple ports (+ & Ultra) versus one large reflex port (PCi) Is the single PCi pipe more efficient? Or do multiple pipes offer something more than just flexible tuning?

ChrisBee

IIRC, another problem with plugging two ports is port noise at higher volumes, all the air rushing out of that one port will generate an audible "woosh".

Ron has of course explained everything; to add in my case I bought a 25-31PCi tuned by SVS to 22 Hz (as I understand it, by using a slightly longer port than in a "standard 25-31). This was because I wanted the smallest cylinder available (for WAF), but since I live in an apartment and can't/don't play stuff loud, sacrificing headroom wasn't an issue. I'd much rather have bought a 16-46PCi, but between WAF and more expensive shipping, buying the smallest was a necessity. As it turns out, I'm perfectly happy with it and presently have no plans to change it to anything else -- sorry Ron, no upgrades for now, but if I ever do, there's only one brand I'd buy

Yes. All else being equal, the smaller cabinet will be less sensitive near the tuning point (Fb), and, consequently, more rolled-off down low. Also, as has been mentioned, a lower Fb passes more responsibility onto the driver above that point, so there's less output available.
In many cases, however, this lower tune and gradual rolloff can be a perfect complement to the room's natural gain resulting in ideal in-room FR and adequate output.

So looking at the different tube subs the difference is tuning point and height. Now, would it be possible to add on some height yourself to one to help the output? Not that it matters much as there is only a $50 step up difference but I'm just wondering.

Also, I'll most likely be going with a cube for the WAF but I'm just trying to learn here

Yes, although it wouldn't "help the output" as such. Adding box volume (Vb) would also lower the tuning frequency for a given port length. If you then shortened the port to get the tune back where you started, you'd have higher efficiency at Fb than where you started. It seems to me that it would be ridiculously complicated and pointless given the price difference...but I'd guess it's possible.
Were I in the market for a sub, I'd just buy one of the models as-is. They seem to know what they're doing.


Here's an online speaker FR calculator, play with it a bit to get an idea of how Vb and Fb relate. Not sure about the Vas, Qts, and Fs of the SVS driver, but maybe someone could post them and you could plug them in.
http://www.linearteam.dk/default.aspx?pageid=newdriver

I just did a sweep with one 25-31CS+ and then did another sweep with the PC-Ultra calibrated individually to the same level +-. After doing so I then recalibrated and did yet another sweep with both running. Hope this will help answer your question Allen. Numbers have been corrected. Could have measured lower with the Ultra also.

PC-Ultra--- 25-31CS+--- Dual/Together recalibrated

19 hz---72 ---62 ---68
2o hz---72.5 --63.5 ---69.5
22 hz---74.5 --69.5 ---73.5
25 hz---79 ---77 ---78
28 hz---83 ---83 ---84
^13db swing...^21db swing.....^16db swing

The numbers drift back down into the 70s after 45 hz and are pretty constant across the board. A db higher here and there with the 25-31CS+. I believe the numbers would be a little different if the level of play was increased. Higher hz material would be more noticeable on the 25-31CS+ and -well- the Ultra's performance on the lower hz material is noticed in the numbers and a out of body experience to be experienced Admittedly my leaky HT provides less room-gain than what many experience.

Now how to get the best out of both worlds?

EDIT> These kind of posts never post the way I submit. Editing doesn't help.:b

That helps out a lot. I should be getting my houseplans today I hope so I'll have a better idea of what size space I will need to fill up. I know it is a large room though as the living room, dining room, and kitchen are pretty much one huge room.

In a room like that a good choice might be the PB2-Plus, PB2-Ultra, PC-Ultra or the B4-Plus. All but the PC-Ultra come in the stock 25hz tune and can be tuned lower at will. I find that having both tunes available is a very nice option. Some material really shines with the lower tune and viceversa. It all comes down to whatever rocks your boat and the material respectfully.

You will notice in the numbers that running dual colocated in different tunes will cause some conciliation in the lower freqs also but still be a good amount more than the higher tuned 25-31CS+. But if I was for example to> try playing the first (Fly By) in SW II, which is basically at 30 hz scene. The 20 hz tuned sub would play it at say 104 db versus 108 db on the 25 tuned CS+ sub at the same listening level.

Give Tom or Ron a holler at SVS and share with them what your preferences/room dimensions are and they will do you right.

Congrats on your new house.