Another thought...Sub's yes here.

VR3

If Russ owned a SVS, the port diamater would change constantly......with white internal *corrosion*

madmax

Euuwwwwweeeeeee..............

RuSsMaN

Good call Sid - how did you know I would need a 3" wide port?

dan t

Originally posted by TroyD
How many people are using subs (SVS owners need not respond)that REALLY get into the low 20's?

BDT

Count me in. I own a Velodyne SPL-1200 and like it. According to Sound and Vision Magazine, the SPL-1200 was measured at a "bone-rattling 16 Hz". I believe it.


Dan

dan t

Current front setup is:

Polk Monitor 10 Series2
Sony TA-E9000ES pre-pro
Adcom GFA 7700
Velo SPL-1200

My doors records sound pretty good.,.,

Dan

Dr. Spec

With my program increasing the port size lowers the resonance freq. It may be that they are already at the lowest response most people would choose with the ports plugged and are digging even deeper when the other ports are open. Given that, if you lower the res freq even more (by opening the ports) the response is drug even lower at the expense of not being flat. That is the only logical conclusion.

I've taught part time at a local college for the last six years, and I've seen this repeating pattern of behavior where my students are compelled to justify the answer that their PC or calculator is displaying, even if it means violating basic tenets of mathematics or physics. I always tell them that the answer being displayed has to make sense and if it doesn't, something is wrong and go back and check your input values and equations.

I'm picking on you here in the warmest possible terms and without any prejudice or malice; your post so perfectly fit this behavioral phenomenon I just had to relay my experiences with it.

I tried WinIsd again and I guess when you change port diameter it is automaticly changing port length making it hard to get a handle on port diameter while keeping the length the same and what it does to box res.

Now this post is after you have seen the long hand equations and are now pretty convinced something was amiss with your original thought process. So armed with that, you return to WinISD with your critical thinking cap on, and lo and behold you discover WinISD automatically alters a second key parameter when the one in question is being changed, making it impossible to prove or disprove our theory. Well done madmax.

Doc

Dr. Spec

Originally posted by ATCVenom
Was told that the PB-2 ISD would crawl down to about 16 hz with 123 db spl.. Hmmm wonder if that will be good enough
hehe

Regarding the relative merits of the PB2-ISD vs. PB2+ vs. PB2 Ultra:

All three will have the same extension capabilities, but the PB2+ will have an edge in clean output capabilities, and the PB2 Ultra will take that another step further.

Going from the PB2-ISD to the PB2+ will give you a 2-4 dB jump. Going from the PB2+ to the PB2 Ultra will give you another 1-2 dB jump. So going from the PB2-ISD to the PB2-Ultra will give you a jump in the 3-6 dB range.

All of the SV subwoofers are designed to produce any input signal (music or film) as accurately as possible. The PB2+ and PB2-ISD will sound identical until the PB2-ISD reaches its output limits. At that point, the PB2+ will still be able to play another 2-3 dB louder without straining.

I doubt the PB2-ISD can generate 123 dB at 16 Hz. It would only have one or two 3" ports open for this tune and this is simply not enough port to get the job done. It might hit 123 dB at the listening position in the 25-30 Hz region, though.

Doc

madmax

No offense taken. I consider programs such as WinISD tools and rely on them. Being 42 and having a BSEE leaves me lazy these days. Truthfully I hadn't given the port thing a lot of thought other than I noticed a relationship in port size while playing around with a bunch of different drivers. But lets get to a common sense summary. If you have one port it has a certain diameter and length. If you place another port of the same size in the box you would raise the resonant frequency of the box. If you then lengthen the ports you can again lower the res freq. This is fun stuff!
madmax

Strong Bad

Good lord! You guys make listening to music and movies a serious effort! Too much effort for me!

Just buy the damn thing, set it up and enjoy!

Dr. Spec

Originally posted by Vr3MxStyler2k3
A sealed enclosure hits lower than a ported enclosure. But not quite as loud.

This is not true. The sealed enclosure is not known for its ability to troll.

Unless it is equipped with a LT circuit, the acoustic suspension design obeys Hoffmann's Iron Law and needs to be incredibly large in order to achieve a really deep tune point with good volume. The Large Advent Loudspeaker we both own for example is tuned to about 32 Hz.

Most sealed designs are flat to the 30-35 Hz region and then they (correct madmax) roll-off at a slower rate (2nd order) than the 4th order vented design.

The benefits of the sealed design are almost ideal transient response and group delay characteristics and ease of design. A properly designed sealed unit with a good woofer will almost always produce excellent bass quality and they are often the DIY choice in a music only application.

The vented design cheats and relies on the resonator (port or PR) to deepen the extension and increase the volume. When the resonator is tuned properly, it begins to take over as the driver would naturally start rolling off and it provides a seamless extension of the frequency response along with maintaining considerable volume capability in the lowest octaves.

It's cool to look at a woofer excursion charts for a vented sub. The woofer excursion is the highest just before the tune point (this is the frequency which limits the overall SPL the sub is capable of producing) and as the resonator takes over, woofer excursion drops dramatically. It is at this point in a vented design that lots of air starts flowing out of the ports.

Below the tune point, the resonator fails to efficiently function and the woofer excursion again skyrockets and this can cause bottoming since the vented design lacks the "restoring force" of the sealed design and the woofer becomes poorly controlled below the tune point. Hence the need for a subsonic filter in a vented subwoofer at high SPL.

Doc

shack

Originally posted by john d. strong
Good lord! You guys make listening to music and movies a serious effort! Too much effort for me!

Just buy the damn thing, set it up and enjoy!

I tend to agree. I'll tweek my golf swing...I'll tweek the motor on my Mustang...but when it comes to audio, I'll set it up and if it sounds and looks good then I kick back and enjoy the music/video.

However...thank goodness there are those who like to tweek the audio/video stuff because it makes my enjoyment easy!

faster100

Doc, will they ever listen and learn? from the pro!

iTS A subwoofer people, it produces bass.. ok next subject!! LOL Kidding kidding, funny haha I know how you guys can get in here.. without the smileys and lol's

madmax

The subwoofer is only one little small part of the experience.
madmax

Tour2ma

What if it's a big subwoofer???

VR3

What if....
It's a SVS PB4? If I owned that thing, the first 24 hours of its playing would be all bass tracks.....

madmax

A friend just bought one of the SVS self powered subs. It sounds good but I noticed something that disturbed me a little. You can see the top of the tube moving in a horizontal plane. Up to maybe 1/2 inch. The woofer is facing downward obviously and the port is upward. It seems it should not move side to side? Any opinions on this? It seems that this would cause distortion or something. Do all of them do that?
madmax

Dr. Spec

You said vent in the singular, so I'm assuming this is a PCi and not a PC+ or an Ultra. The vent is screwed to the endcap with wood screws. The hole in the endcap is sized for the vent. I can't imagine it moves 1/2" back and forth. If it does, the screws are loose and something is wrong and he should contact SVS technical support.

I never had that issue with my PC+ and neither has my buddy with his 25-31PCi - those vents are pretty well secured in my experience. But anything is possible and he should email tech support.

faster100

those who have SVS love them, those who don't... just don't know yet!! Us foaming at the mouth SVS owners!! LOL

madmax

It is not the vent, it is the whole enclosure. Obviously the bottom doesn't move much because it is sitting on the floor (bare concrete) but the top does. I didn't look but given the way it moves it must have rubber feet.
madmax

Dr. Spec

Oh...by tube I thought you meant port. My mistake. You were talking about the entire cylinder.

Yes, the cylinder has small rubber feet and the reactionary forces of the driver are quite strong and the driver is capable of moving the sub around on a concrete or armstrong floor. Mine actually used to move a few inches at a time during the bassy heavy parts of movies at loud playback. A piece of carpeting under it should solve that problem.

It may appear as if the tubing is flexing at the top and not the bottom but it's not. The ruber feet are giving a bit and it's moving back and forth. That tubing is extremely strong and rigid in the lateral plane and is virtually impossible to flex or bend with the endcaps installed.

The tubing is far more rigid and stronger than Sonotube (or it's equivalent), being a custom laminate material made exclusively for SVS which is covered in a sound deadening polymer and cut to exacting tolerances on a CNC lathe. This tubing has survived being dropped off a roof top without damage.

How much time did you spend with the sub and do you feel it was properly calibrated and well placed and set-up? Did you listen to music or movies?

Thanks.

mantis

faster100
I just dig when someone loves what they own.

I just gotta hear a SVS sub go.One of these days.

Dr. Spec

Dan, you're coming up for Dr. Spec's LOTR EE marathon, right?

madmax

So far I have only spent maybe 20 minutes with it. It was sitting in the middle of the room to test it out. Nothing more. (the room is under major construction right now). We were running a generator through it to see what in the room made noise at different frequencies. It's amazing what freq's you can pick out as troublesome if you spend the time.
madmax

Dr. Spec

Is this a 25-31, 20-39, or 16-46 PCi?

madmax

I'll have to ask him the model. It appears to be about 4 feet high, single port, self powered. I would assume one of the less costly series.
madmax