SVS 20-39PC+ In Room Frequency Response - Amazing!

Dr. Spec

Hi Guys:

I figured it was time to verify the in room frequency response of my SVS 20-39PC+.

I burned a CD using a 1/12 octave frequency generator downloaded off the Shiva Sonotube webpage. Each tone is 10 seconds long, and the sweep ran from 10 Hz to 71 Hz.

I am using a factory certified professional-grade Bruel & Kjaer Model 2205 SPL meter which I just calibrated. This SPL meter is accurate down into the subsonic range, and does not need a "Rat Shack" type correction factor for bass tones. Meter settings are C-Weighted, Slow.

I mounted the B&K on a tripod at the listening position, about 11 feet from the sub, pointed toward the front of the room, and tilted about 40 degrees up toward the ceiling.

I set the master volume on my receiver to give me about an 80 dB average volume. I am not using any type of equalizer or feedback destroyer. This is the real deal in my HT room at the couch.

For the purposes of the test, I set the SS filter to 12 Hz, just to see how low this thing can really go.

I ran Test #1 with all three vent ports open, and Test #2 with two vent ports open and one vent port plugged with the factory supplied foam port plug.

Test 1 All Ports Open:

As can be seen from Test 1, the sub holds a nice flat +/- 4 dB from 70 Hz down to about 30 Hz, and then begins a gentle rise, cresting at +10 dB at 24 Hz, and then dropping back down to -3 dB at around 16 Hz. It hangs in there suprisingly well checking in at -5 dB at a staggering 11 Hz.

Test 2 Two Ports Open, One Port Plugged:

As can be seen from Test 2, the sub holds +/- 4 dB from 70 Hz down to 11 Hz. Read it again folks - an essentially flat line from 70 Hz to 11 Hz with no major peaks or dips - in my HT room, without EQ, or a feedback destroyer.

My Preference and Summary:

Although the in room response is obviously more accurate with one port plugged, I actually prefer HT playback with all three ports open. The flat response from 70 Hz down to 30 Hz gives me accuracy with no boom, and the gentle rise and peak at 24 Hz provides reinforcement right where most LFE effects are at their most impressive.

Nonetheless, the accuracy and flatness provided by plugging one port is quite simply amazing for ANY sub at ANY price. But for an $800 asking price - this in room frequency response is almost beyond belief!

Doc

Freq. Test 1 SPL Test 2 SPL

10 65 68
10.6 69 73
11.2 75 81
11.9 76 82
12.6 74 81
13.3 75 80
14.1 75 81
15 75 82
15.8 76 83
16.8 78 84
17.8 80 84
18.8 84 83
20 87 83
21.1 88 81
22.4 88 80
23.7 90 82
25.1 88 82
26.6 86 81
28.2 82 79
29.9 80 77
31.6 81 77
33.5 80 75
35.5 79 76
37.6 78 76
39.8 77 76
42.2 77 76
44.7 78 77
47.3 79 78
50.1 80 79
53.1 80 79
56.2 82 82
59.6 84 84
63.1 84 84
66.8 84 84
70.8 80 80

scottvamp

Sounds like alot of fun. Hey, movies are fun to watch also.;)

Dr. Spec

Yep - I'm a gear head at heart. I had more fun with this stuff yesterday than watching a movie!

I STILL can't believe this thing stayed FLAT to 11 Hz (!!) - in my HT room. That's with just one port plugged!

Hell, I couldn't HEAR anything until the sweep got up around 17 Hz, but I sure could FEEL the pressure on my ears!

If anyone wants to try this test, I'll email you the zipped MP3 file and the Rat Shack correction factors if that is your meter.

Doc

HBombToo

Thanks for sharing.

I tried to graph it for ya... We'll see if it works for ya.

HBomb

HBombToo

ATC, can you download the Word Document?
I'm not sure if it worked... Would be real cool if we could also attach .xls files.

Can Polk do that and who could we contact??

Dr. Spec

Great work Henry! How did you do that? I thought we could only attach .JPG or .GIF files. Anyway, that's the exact curves - perfect.

ATC - I'll give it a try. SVS asked for it and I had a delivery failure. But I was able to successfully send it to a HTF member. Go figure. Just unzip the files (there are 41 MPG files) and burn them to a disc. The sweep is actually 10-100 Hz, but I terminated my graph at 70.8 Hz. Mine unzipped with file #1 being 100 Hz, and file #2 being 10 Hz, so watch the order they unzip.

Doc

Dr. Spec

ATC: the file is 6 meg, zipped. It is too big for your mailbox - I got an error message. Is there a larger mailbox on an alternative address?

Doc

HBombToo

All I did was copy the text from your submission and copied it into an .xls workbook. Used the Text to columns feature to seperate the space deliminated data then used the graphing function. I then copied the graph and pasted it into word.doc which then I used the attach feature from the browser.

I really think Polk should allow us to attach .xls books for this type of information exchange.

HBomb

Dr. Spec

Ah so! We tried it here and it worked good. Thanks for the tip - I'll use that from now on to post graphs.

Doc

goingganzo

this is the sub i am bulding when the dricer comes in january this is 1 driver with 350 wats rms
Box size : 250.0 l
Tuning frequency : 16.00 Hz
Vent : 2 vent(s)
0.463 m length for each
0.102 m round


Relative
Freq Gain SPL
[Hz] [dB] [dB]
10.00 -19.12 94.82
15.00 -4.50 109.44
20.00 -2.54 111.40
25.00 -2.62 111.32
30.00 -2.41 111.53
35.00 -2.12 111.82
40.00 -1.83 112.11
45.00 -1.58 112.36
50.00 -1.36 112.58
55.00 -1.19 112.76
60.00 -1.04 112.91
65.00 -0.91 113.03
70.00 -0.80 113.14
75.00 -0.72 113.22
80.00 -0.64 113.30
85.00 -0.58 113.37



this is 2 drivers with 700 wats rms
Relative
Freq Gain SPL
[Hz] [dB] [dB]
10.00 -19.12 100.84
15.00 -4.50 115.46
20.00 -2.54 117.42
25.00 -2.62 117.34
30.00 -2.41 117.55
35.00 -2.12 117.84
40.00 -1.83 118.13
45.00 -1.58 118.38
50.00 -1.36 118.60
55.00 -1.19 118.78
60.00 -1.04 118.93
65.00 -0.91 119.05
70.00 -0.80 119.16
75.00 -0.72 119.25
80.00 -0.64 119.32
85.00 -0.58 119.39

total cost for drivers 320
total cost for boxes 100
amp cost ?300

this is moddled numbers off of win isd cant wait for the driver

but i cant decide between 500 wats rms or 350 per driver

Dr. Spec

Ganzo - your sono-sub displaces 240 liters?! I thought you were putting the Stryke AV-12 into your sono-sub.

Anyway, you don't have the venting capability for 2 drivers in one enclosure. The two 4" vents you are currently using are perfect for one of the Stryke AV-12 drivers. You would need to nearly double your venting area to avoid power compression and vent noise if you went with 2 AV-12's in one enclosure.

Doc

goingganzo

av15 i am putting into it but i might be bulding a box for it if it puts my velo to shame caues i will sell my velo and buy a seccond one and buld a huge box for it and put it where my velo is curentlay it is in the laundry room with it's woofer and port in the ht it is bult into the wall


in the 2 drivers box i will be putting 4 4in flaired pors with same lenth as above

freid

Hey Dr.
I too am interested in receiving a copy of that mp3 file. I will be using a rat-shack SPL meter.
My e-mail address is
freid@trinidadexpress.com

Dr. Spec

You've got mail..........let me know how it goes.

Doc

gplracer

I should try this with my dual SVS 20-39CS+/samson 100

Dr. Spec

Definitely! I will email you the stuff if you want.

I increased my sweep to 100 Hz and also ran it at 0, 90, and 180 degrees of phase.

I was astonished to find out that running my sub 180 degrees out of phase completely flattened a nasty null at the 80 Hz crossover point. This is counterintuitive since the sub and the mains are on the same wall, but the proof is there and I can't ignore it.

This obviously suggests the mains and the sub are out of phase. I have several theories brewing at this point, but wanted anyone else's input on this phenomenon.

Doc