Why so much SVS bashing...

Rotarydude

Okay here is what I got with the LSi25 playing by itself without the SVS.







Here is the SVS playing by itself without the LSi25 sub portion.




Looks I now know which speaker is contributing all the 80hz.

However it looks like 40hz is the room's resonant frequency. Would you agree?

Rotarydude

Okay after playing around...with the x-over...which didn't seem to help much. But what seem to really help is the Phase control on the SVS. I got the 100-50hz as flat as I could. But I just can't tame 40hz. I moved the Sub away from one wall, but still it's hitting pretty high.

Here are the results

Dr. Spec

Bravo!

You killed that huge null at 63 Hz by fiddling with the SVS phase control. This just demonstrates how important a feature variable phase control can be when deal with nasty rooms.

I'll agree, you have a room peak at 40 Hz, but the overall curve is now +/- 4 dB or so from 100 to 20 Hz.

Try setting the SVS filter to 85-90 Hz (switch enable) and see what happens to that hump at 87 Hz.

Anyway, I'd like to also point out to anyone reading this thread:

The LSi25 NOSEDIVES at 40 Hz and is some 20+ dB DOWN at 20 Hz compared to the average level in the 40-100 Hz region.

The SVS OTOH as advertised is FLAT to 20 Hz.

Don't always believe what you read about extension. The LSi25 is missing the entire bottom octave compared to the SVS. The SVS performs in the real world, in a real room, to 20 Hz.

This again graphically (sorry) demonstrates the need for a quality subwoofer, even with the flagship LSi25.

Doc

Rotarydude

One couldn't stress enough on how important it is to have a sub-sonic subwoofer. To really enjoy your movies at its most potential. For most music listening 40hz would be your lowest, this will include rap music with BASS. The only other music that I know that plays down beyond 40hz are classical organ.

However if you are a "hardcore" movie viewer, and require the up-most demand of your system. As you can see from all the graphs, 31hz-16hz is critical in movies. Because the director/sound engineer produce those deep low rumble effects there.

Now back to the tuning

I have asked Tom V to look at these graphs, and I also asked for his suggestion on using the filter and sS filter along with the port holes to see if 40hz is tameable with those tools. I will let everyone know.

There might be something I can do with the SS filter, as I understand it, its actually a high pass filter for sub-sonic frequency. But I like some input on that before venturing into messing with the SS filter.

Dr. Spec

Yes, the SS filter is simply a high pass set to extremely low frequencies.

It is designed to prevent the woofer from unloading below the tune point of the enclosure and bottoming out. The enclosure lacks restoring force below the tune point and allows easier bottoming of the driver, hence the SS filter.

There is no reason to set it to 25 Hz (the highest setting) since that is still far from the 40 Hz peak.

The proper tune to run with the ports/plugs and the SS filter is as follows (ports and SS filter listed in that order):

3/20
2/16
1/12
The stock 3/20 tune is by far the best to run the PC+.

If you plug a port and go 2/16, you will lose some output in the higher regions, but it won't alter than 40 Hz hump much.

You need a parametric EQ, or still need to experiment with sub placement to knock that hump down.

Grimster74

Since I've had my PB2+, I've never really played with plugging the ports and the SS filter. Just can't seem to find the time to play around with it. As it stands I'm set on 3 ports open and the SS filter on 25Hz. What do you guys currently have your PB2+'s set at.

Dr. Spec

3/16 in a SMALLER room gives good extension to 15 Hz, at the increased possibility of bottoming the drivers below the tune point.

In a larger room and/or at very high SPL, 3/25 is the WTG.

2/20 digs as deep as 3/16 but with far less potential to bottom the drivers.

2/16 goes to China, with a large boost in the 13-17 Hz region.

Don't even bother with 1/16 - too little port.
Overall, three ports open sounds the best, flows the best, and has the most effortless and impactful quality. In your larger room, I'd stick with 3/25. It will be strong to 21-22 Hz.

Rotarydude

Well instead of setting the SS filter to 25, I went 16hz. This flatten out the the rest of the sub-sonic frequency. I think this works in my room because my sub is on the opposite side of the room where it opens up to my dinning room and kitchen. With all that space.

Oh and it didn't change anything from the 40hz. So I think the only way to fix this....is with an EQ. I can't place my sub anywhere else.

Gonna see how I am going to fix this with an EQ. Because I don't think the SVS is contributing to this mess. I believe it's the LSi. Cuz the LSi are peaking much more than the SVS.

SO I have to figure out how to put the behringer in to the line.

Dr. Spec

Rotary:

If you run 16 on the SS, plug or port or risk bottoming the driver. I strongly advise 3/20 or 2/16 and not mismatching the port and SS filter configuration in that size room at the levels you are playing.

Rotarydude

Haha, don't worry, I got the one plug in right now. I lost 2db from the Avia test. But since it was 4-5db hot, it's okay. 2-3db hot is still pretty good.

I'll replace the previous graph with a new one to show the 16hz setting.

Dr. Spec

Normally what happens when a port is plugged on the 20-39PC+ is that you lose 1.5-2 dB in output, and you also squash the typical room gain hump at 22 Hz. Of course, the curve beefs up dramatically in the 13-17 Hz region, which is the whole point.

The 20-39PC+ trolls to 17 Hz in the stock tune, so I never saw the merit in plugging a port. It makes the woofers work harder and run hotter and obviously you not only lose static output for a given voltage input, but you also lose ultimate SPL capability - something it seemed you valued highly and were trying to get more of in the earlier parts of this thread.

You will not see 114 dB peaks on the meter with a port plugged, I can almost assure you of that. Probably more like 111 dB.

I'll agree the LSi seems quite a bit peakier than the 20-39 in the 40 Hz region (no surprise) but the room is definitely the culprit overall - that's a big peak.

Have you tried moving the meter around to map out that peak? Often times, moving the meter even 2 feet laterally gives drastically different looking room curves. Some peaks and nulls are very small in the area they affect.

That phase control REALLY made a difference in that huge null though. What a great feature that is.

Rotarydude

You'll be pleasently surprise, as I am right now....

I just stuck in SW: CW played Chapter 3 ( my favorite) at reference level. During the sequence where he say, "We are making our final approach to Coruscant", the RS SPL meter hit a 114.5!!! I am MORE than please with this finding. As before it was only peaking at 113-114db. Even though nothing fell off, I am really getting happy. Knowing that the freq is getting flatter, and deeper...plus still maintaining SPL.

Now I want to know how are some of you getting your pictures shaken off the wall! You guys must be hitting 120db+!!!

Dr. Spec

That doesn't jive with my experiences, but take it when you can get it!

Possibly the meter was in a slightly different spot - that can account for a 1-2 dB difference in measured output, and the RS meter isn't the most (ahem) accurate and repeatable unit under high SPL conditions. Although it works pretty darn well for basic calibration.

That SW-AOTC passage is primarily in the 25 Hz region, so I can't imagine a lower tune (which boosts the 13-18 Hz region) contributing to an overal increase in SPL. I'm not calling you a liar either - enjoy equal to or better SPL and the additional extension!

The PB2+ in the stock tune has about 6 dB more headroom than the 20-39PC+ in the >22 Hz region. In my 2000 ft3 room, I can indeed hit 120+ dB and I have knocked a small deer skull mount off the wall and rattled and moved other things around as well. But a securely attached picture will probably stay that way in my experience.

At lower levels, the PB2+ just loafs and laughs at everything thrown at it. Where the PC+ was starting to strain (113-114 dB region on the meter), the PB2+ is still only working moderately hard. With twice the driver and 70% more port area......what else would you expect? :cool:

kberg

Originally posted by Dr. Spec
...and the RS meter isn't the most (ahem) accurate and repeatable unit under high SPL conditions. Although it works pretty darn well for basic calibration.

Thanks, Doc. This is a good tip to remember, as I have seen my own RS meter vary quite a bit after repeating passages from exactly the same location w/ changing ANYTHING, and I'm sure it hurts me even more by using a digital instead of an analog meter.