25-31PC+ @20Hz -vs- 20-39PC+ @20hz output charts (1 Viewer)

[Sebastian]

I thought 10dB was twice as loud, 3dB is an SPL level where the difference is discernable to the naked ear, and requires twice as much power to achieve (or is that 6dB)?

Ah, you are absolutely right Yee, thanks for the clarification. Too bad I just lost some credibility on that one.
Any way 3dB IMO (going by ear) is definitely noticeable, as someone already mentioned. Good Luck, I don’t think you can go wrong with any SVS sub.

 

[Chris Grillo]

Guys thanks for all the info!
I am going to check out audioenvy and see if there is someone who lives near me so I can here one of the PC+ models !! Chris Xolotl what did you have before the 25-31PC+? and how do you like your new sub???

 

[Chris Xolotl]

I had a small JBL 10" Sub came with a satellite system years ago.

I really enjoy the 25-31PC+. I think I need to place with placement a bit now. The attenuation of the low frequencies (20Hz-60Hz) is apparant when you start getting about 15' away from the sub when playing movies.

However, playing a music CD in stereo mode with the sub is amazing.

I used to have it behind the listeners in the corner but that caused a few concussions, so now it's in the front corner (about 2' from the corner because of setup reasons).

From what I understand, if that if you have a lot of volume to fill then you should get the 25-31PC+ instead of the 20-3xPC+

I am filling an open ended 6,000 cu-ft area with open areas opening up to more rooms. It's an open layout place where I am living

 

[Zack_R]

From what I understand, if that if you have a lot of volume to fill then you should get the 25-31PC+ instead of the 20-3xPC+

The trick with a lot of space (I have 7500+ cubic feet) is that you can't count on room gain if you in fact want to ensure you hit a certain low hz with authority. So depending on the individual, the 2039 or 1646 could be the best alternative for the bigger rooms.

My recommendation for people deciding on sub choices with larger room sizes is to calibrate your current system to Dolby Reference levels and playback movies like the Two Towers, Toy Story Two, etc and see just how loud you like to listen. If you are listening at -5db or more from reference levels, I would recommend the lower tuned sub as this will ensure you hit the subsonic frequencies with authority. In this example you have some headroom to run the sub 2-3dbs hot if you desire or you could buy an eq and bump the 25-35 hz region 2-3dbs.

 

[steve nn]

Well Chris G I wonder how much of a help we have been? I understand your dilemma and hope after factoring in all the info you are able to feal confident about which sub to go with. Both options are good and have their different strengths. My leaky HT is 12 X 24 with 10' ceilings (2880 cubic ft) and one 25-31+ does very well on it's own. I had a 20.7 tuned AV15 that did well also. I cant say which tune I honestly like better so my approach has been with going the multiple SVS rout.

I don't think you have mentioned the size room your new sub will be going in? Is it carpet over suspended wood floor?

 

[Chris Grillo]

steve nn,

Yes it is carpet over suspended wood floor! my main room is 1400sq ft with a 7ft opening to a 400sqft entrance hall behind it and a 3ft opening to the right with a room of 1150sqft.its sounds big but if you were to see it the main room is rather small and I guess because their is no way to block off the other rooms it req's more power. by the way my ceilings are only 8'4" high. My current sub is only a 100watt 10" and it never bottoms out even set +6-8db hot!mind you it it tuned at 27hz. if that makes a difference!!
I never thought I would need the kind of output SVS people suggested but it must be because of the other rooms that are attached!

 

[steve nn]

Chris G my hunch is 70% chance you would be more happy with the 25-31+. This was your own first thought and what you have to remember is the (Authority) the 25-31+ will have even in the lower material as opposed to your previous sub. It will have the punch that maybe you are wanting also.

This is no slam on my previous Velodyne subs but I ran dual ct-150's prior to trying out a 25-31CS+. The first thing I noticed in my own in-room experience was that one 25-31CS+ took out dual ct-150's in the lower freqs. At 30 hz the SVS was -1db. Now I possibly could have pushed the SVS a little farther but decided not to. The CS+ pulled away as the material went lower. The Velo's were tuned to 23hz.

Your other adjoining rooms will play a factor. How much I cant say? My 25-31+'s are just a few feet away from a entrance but my seating is definitely in the sweet-spot. I can hit close to 130db with three at 30 hz roughly. (Very leaky room) My ears hurt for two weeks because I did it over and over just to see what I could push :rolleyes.. The great thing about a SVS is the authority they have in the lower hz material where others will peter out and the different tonal characteristics it will produce. You would also still have the option of tuning it lower but at a cost of it being more susceptible to bottoming out. I generally have mine in their stock tune though. If I would have known in hind-site that I was going to go multiple. I would have gone the 20-39CS+ option rout though.

I understand your comment on your past thinking.> You do not need SVS type output. After experiencing it you will understand. Remember it's the low hz spl that many of us get so hooked on. Most DVD's are basically 25 hz on up so you will be covered very well imo for what it is worth. I need a bass fix so I'm out of here.

Edit>> Just watched (Matrix Reloaded) with all three port plugs engaged. Very nice having more spl in the lower hz range if you have the headroom?

 

[Chris Xolotl]

I think I can agree mostly with the above post. Chris, looking at your room size and what you had before (similar to my situation). The 25-31PC+ will certainly rock your space. The amp is capable of spitting out over 500 Watts of power.

Even with all 3 ports open, I think I get readings a bit under 20Hz using Avia (not at the same db's though).


Hey, does anyone know the upper frequency limit for the 25-31PC+ ?

 

[steve nn]

Well it has a +/-3 from 20-100hz so from there I wouldn't know myself. I spend my energy on the low hz.

I wish I would have saved my plot sheet in the two different tunes. I think maybe I'll search a Thread I posted awhile back and see if I can dig it up. It starts at 15hz on up.

(I'll be back!)

Edit> I found what I was looking for but it isn't what I'm looking for. So I'll do another in both tunes with calibrating first each time and then post.

 

[Chris Grillo]

You Guys are great!!
I love getting all types of input from SVS owners! I am pretty sure I will go with the 25-31PC+!!
What is the best way (what software)to see how low my current sub Goes down too? (so I can get an idea of what my room will do for me!!) So when I get my new SVS I can check it out also!!

 

[Shawn Shultzaberger]

I've got to throw my $.02 worth in as well. It's just so fun!

Chris G.,

I'd say don't rule out a (older model) dual 25-31CS if you could fit them in your room. Every once in a while I find them on Ebay going for quite a bit less than the $1025 or so that I paid for mine. I have a 4500 cu.ft. room (carpeted with suspended wood floor) and running dual 22-31CS's (tuned to 22Hz) gives me more than enough head room. I like the 25-31CS (22-31) because I listen to a lot of music as well. Even during the Ice Field scene in Titan A.E. my hair and pant legs are moving from the amount of air these things are pushing. And the bass is so darned clean! And this is two of SVS's older models.

No matter which one you go with you will wear a grin from ear to ear. I have for two years.

 

[Chris Xolotl]

Steve. That would be great if you could post a graph!!

 

[steve nn]

When I get home from work today I will post. I had time to do all the readings yesterday but no time to post.

 

[Chris Grillo]

Steve,
looking forward to graph! any thoughts on the software question for checking hz? so I can check my rooms help on low end hz!(as I posted earlier) Thanks

 

[Edward J M]

The cheapest way to run an FR sweep is with a CD burned with test tones (1/12 octave works well), and an RS sound level meter.

http://beyond_gomer.tripod.com/

You will need to use correction factors specific for the RS meter since it is C-weighted and also introduces its own additional error into the response. You will have to interpolate CFs for frequencies between those posted on the website.
http://members.tripod.com/~terrycthe...um/page11.html

Run the test tones, record the sound pressure at each frequency, add the correction factor, and plot the results in something like Excel. Voila! FR charts for your sub.

If you have a high quality sound meter, the above method can be pretty accurate, but is quite labor intensive. Even with CFs, the quality of the RS meter is somewhat suspect, and its accuracy in the extreme bass regions is questionable. But it's certainly better than nothing!

Run the test tones at around 80-85 dB or you will fry the VC of your woofer. They aren't designed to be continuous output devices with no rest periods - sine waves are tough on subs.

A less labor intensive means is with a powerful home PC, RTA software, and pro-grade mics and mic preamps. This is considerably more expensive though, and the learning curve is significant.

Here is what an Excel spreadsheet saved as a .jpg looks like. This is for my SVS PB2-Plus.

 

[Chris Grillo]

Hi Ed,

Great info thanks!! I do have one question!
When you say "Run the test tones at around 80-85db" Is that from your normal listening (or calibrated) position? or is there a different distance the the meter should be at??

 

[steve nn]

Well said Ed. I did a little playing around yesterday afternoon and this is what I came up with using what humble means I have to work with.

20 hz Tune____25 hz Tune corrected

18hz- 78.25- 70.25
20hz- 79.50- 73.50
22hz- 78.50- 75.50
25hz- 80---- 80
28hz- 87---- 90
30hz- 89---- 91

You can definitely see from 25hz on down the 20hz tune definitely has the advantage as one would expect. Just have to love that LOW HZ SPL. At 18hz the 20hz tune dropped rather quickly so I didn't bother to plot.

Uncorrected numbers>>
In MATRIX RELOADED scene (3-UPGRADES) the
20hz tune hit 96db and the 25hz tune hit 97.

Scene (4 ZION SHIP) hit 96db with the 20hz tune and in the 25hz tune hit 96 also.

In STAR WARS II on the big first FLY-BY scene I hit 104db in the 20hz tune and in the 25hz tune I hit 105db.

So there you go Chris. I also asked Frank Carter to post a pic of my SVS's so you can see what I'm up against with placement. One on it's own still does amazingly well though. If I were to place a single 20hz tuned sub in the same location I would have more of a problem with bottoming it out than a single 25hz tuned sub. If you can get away with it the 20hz will be more favorable in the lower freqs though.

Fire'm up and run'm Hot

 

[Frank Carter]

Here you go Steve:

Click to enlarge:

 

[Edward J M]

When you say "Run the test tones at around 80-85db" Is that from your normal listening (or calibrated) position? or is there a different distance the the meter should be at??

I always run my FR sweeps at the seating position.

The test tones I hotlinked run 10 seconds each and there are something like 42 of them so that's why you don't want to run the CD at 105 dB or something insane like that. It will overheat the VC and ruin the woof.

As the SPL increases, all conventional subwoofers begin to experience power compression and port compression and the curves will begin to roll-off sooner. So a sweep at 85-90 dB (like shown above) will not hold its shape forever. Even the PB2+ can't play 11 Hz at 110 dB for example.

I don't use the above described method anymore, but I still endorse it as being pretty accurate. I use RTA software and a digitally generated "chirp", which generates and plots the entire response curve in about 1 second. It's pretty slick and a lot easier than manually plotting test tones. The chirp gate is long enough to include room acoustics, which is exactly what I want. It is not an MLS-type narrow gate (which would simulate a quasi-anechoic response).

Running FR sweeps is a great way to look at how each tune affects the subwoofer, and also how it interacts with the room at various positions.

It's also a great way to compare different brands of subwoofers, as long as all conditions (placement, mic location, SPL, etc.) are kept the same each time.

 

[Frank Carter]

You will need to use correction factors specific for the RS meter since it is C-weighted and also introduces its own additional error into the response. You will have to interpolate CFs for frequencies between those posted on the website.

You can just download the excel chart below, just enter the number off the meter in the "RAW SPL" column and it will automatically compensate for the meter's imprecision.

http://members.cox.net/frankcarter/S...%20tests.xl s