Infinite Baffle Sub

[spharis]

Mine is installed and powered (and rocking pretty hard I might add) and I wanted to post some review on here for lurkers or others passing through. Short review is don't be scared of an infinite baffle. Ease of installation, and the heavy suspension, and how great it sounds make me glad I went with it vs. losing storage, and having to build a box for a standard sub.

When I purchased this thing I thought "WOW....that suspension is really stiff, I hope it can reproduce lower freqs OK." We'll the questions were answered today as I fired it up and literally watched my keys vibrate out of the ignition, and my TAPs guage start turning in the dash.....it jams. This is one of the most impressive subs I have purchased in a while, and I have purchased many subs. I put it through the works...everything from Bush Glycerine to Nonpoint to even some Run DMC lol......it held it's own, and I am very pleased, and feel it will provide a much added element of entertainment for me while boating. Having never installed or heard an enclosed sub of similar stature in a marine environment, I can' really do a comparison, but I will tell you that it is louder with much better SPL and reproduction than the last Diamond Audio sub had installed in a center console. Don't fear the infinite baffle sub!

And to the regulars on here....yeah the system is finished, and I couldn't be happier.

[dogbert]

Glad it worked out!

[Domsz06]

AWESOME!! I hope to get a box built thiss weekend for mine, but it seems I can never get anything done. Glad someone is!! Congrats sp. By the way my teak looks awesome, will have a pic tonight for your!!!!

OK back to topic, what is an infinite baffle sub?

[lee]

What sub did you go with?

[Jeff T]

Hey, did I miss a post earlier about this sub? I would like to see it for sure.

[spharis]

I ended up getting the Rockford M10......it is built identical to the Power T1-series that I have owned before, but with a much stiffer suspension. I didn't find any other free-airs that I liked the specs on. The worst part was getting it mounted. It weighs about 20 pounds.

[philwsailz]

AWESOME!! I hope to get a box built thiss weekend for mine, but it seems I can never get anything done. Glad someone is!! Congrats sp. By the way my teak looks awesome, will have a pic tonight for your!!!!

OK back to topic, what is an infinite baffle sub?

Speaker installation falls into three or four basic categories:
* Infinite Baffle
* Sealed
* Vented
* Bandpass (due to the nature of the discussion, let's not go into this one)

In general, any woofer has a set of parameters that can be controlled by the design engineer, and these parameters are used and manipulated in the design phase to tweak the woofers performance so it is suitable for a particular application. These parameters can also be used in the enclosure design phase to optimize the enclosure and/or environment that the woofer might be used in. The three critical parameters we have in a woofer are:
Fs: Free-air resonance. The natural resonance of the moving "soft" parts of the woofer, i.e. the cone, the voice coil, the surround roll, and the spider. Fs is expressed in Hz, or cycles per second.
Vas: Volume Acoustic Suspension: Expressed as a volume of air, either in cu.ft. or litres. This parameter tries to define the "stiffness" of the woofer's suspension as an equivalent volume of air confined in a vessel; picture a bicycle tire pump. Hold a finger over the valve, and push down on the cylinder; the resistance you feel is the compliance or springiness of the volume of air in the tire pump. The woofer has a similar springiness...
Qts: The woofer's "Q": Funny number; it has no dimension, no height, no volume of air, no nothing. In general the Q speaks to the "ringiness" if you will of the speaker. A bell for example has a very high Q. It rings and rings and rings.... Sound forever, as it is vibrating at its "Fs" for a long long long time. Grab hold of the bell with one hand and hit it again. "Clunk" Your hand has added a damping component to the resonant system, and it no longer rings. That bell with your hand on it is now "Low-Q"

In very general terms:
Woofers with very low FS values, very low Qts values, and very large Vas values work best in sealed enclosures. The woofer looks to the volume of air trapped inside of the sealed enclosure to provide the necesary spring stiffness to control the motion of the woofer.

Woofers with Fs values of pretty much anything, medium Qts Values, and smallish Vas values work well in vented enclosures. The small Vas and medium Qts values help to control the woofers motion, and the air inside of the enclosure still acts as a spring. Neat thing with a vented box: the springiness of the air inside changes in phase depending on frequency. At optimim tuning, the air moving in and out of the enclosure, is more or less in-phase with the cone of the woofer. I.e. when the cone of the woofer is moving outward, so is the air in the port, and when the cone is moving inwards, the air is doing the same thing. Hard to grasp, but realize this: a properly designed vented enclosure will have HIGHER pressures inside the enclosure when compared to a similar sealed enclosure. It is due to the fact that the air, acting as a spring, has gone through a phase shift and is moving in and out of the enclosure with the woofer, in the same direction at the same time. The sound created at the port is "in-phase" with the sound coming from the woofer, so a vented box will be louder typically, (emphasis on typically, therer are exceptions to every rule).

In both sealed and vented woofer systems, we are providing an effective means of preventing the pressure wave from the back of the woofer cone from interacting with and cancelling the pressure wave off of the front of the woofer cone.

An infinite baffle woofer is designed in such a manner that it has a very low Vas value; it does not need the help and/or support of the air trapped inside of an enclosure to control its motion. The control is provided completely and totally by the woofer's suspension; the surround roll and the suspension spider. As Spharis put it, a free-air woofer is inherently stiff; that is to prevent it from just jumping in and out of the woofer's basket. Due to this stiffness, we will see Qts values that are fairly high; this is a result of the stiffness, and while not totally analogous, the infinite baffle woofer will "ring" to an extent like a bell, quite naturally. Not to worry, it really does not afect the sound too terriby much.

I know, blah blah blah, I just wrote a book, but hang on, not quite done. When using an infinite baffle woofer, (or any woofer for that matter) we still have to do the critical job of preventing the pressure wave off of the back of the woofer from mixing with and cancelling the pressure wave off of the front of the woofer. This is done by mounting it in a wall of some sort; it is that simple. In a typical boat install, the woofer is put in the helm toe-wall, and the back of the woofer is inside the storage compartment fore of the helm. Since the storage area door is typically closed, we do not hear the back wave off of the back of the woofer; it stays inside the storage area. Try opening the storage area, and then stand at a point midway between the steering wheel, and the storage hatch, i.e at roughly the windshield. Notice how the bass volume goes down? That is because you are hearing the front wave mixing with the back wave and the two are cancelling each other out. That points to this point: For an infinite baffle woofer, we always want to prevent the sound coming off of the back of the woofer from interfering with the sound off of the front. Everything else as it relates to the woofers performance is totally dependent upon the woofer design, and not the box, the box volume, the vent tuning, blah blah blah.

Put simply, an infinite baffle woofer is one that needs no box to operate properly; just a wall to separate the sounds coming off the opposite sides of the cone.

Sorry for the long answer, but I thought an explanation of the relative differences would help with the understanding...

[NICKYPOO]

Whoa Dude, that warped my fragile little mind.

What are your thoughts on polyfil?

[spharis]

Polyfil is blah.....Do a search; I've posted alot on it.

OK back to topic, what is an infinite baffle sub?

Short answer, no box, just a seperation. Commonly found in home theater setups. The wall acts as the seperation.

[philwsailz]

Whoa Dude, that warped my fragile little mind.

What are your thoughts on polyfil?

In theory it works, at least in sealed enclosures. From a highly-technical standpoint it changes the cooling rate of the air inside a sealed box. Is it Boyle's law? Anyway, for a given volume, if you increase pressure, you increase heat. If you lower the temperature, you lower the pressure. If you increase temperature, and leave pressure constant, you increase volume.

For a sealed box, it interacts with the air, and affects the instaneous heating and cooling by slowing down the dynamic change in temperature; makes the box seem larger with a lower resonance, without the loss of cone control.

Now to spharis' point: yeah, it works, but can you hear it? Certainly not in a boat. it is really a diminishing returns sort of thing. Great for super-high-end home theater, but probably a waste of time from the pressure/temp/volume standpoint for your boat listening environment.

It can do some other good things, like helping to absorb the back-wave further improving the enclosures ability to isolate it from the front wave, but you are introducing a material that will trap moisture in the enclosure. Not too horrible thing, except for the rust that certainly will form on the ferrous parts of the woofer's motor....

[spharis]

The main benefit of polyfil is to help control standing waves. That's about all the good you are going to hear in audio applications.

[tarheeler]

i bet he is one of those kicker insiders using big words like that.

[tarheeler]

Free-air systems save space and have flat frequency response. The woofer must be specifically designed for free-air use. The lack of a box makes them more convenient to install, but their power handling levels are usually much lower than their boxed counterparts

[bake0296]

Spharis,
Do you have a pic of the sub and where it is mounted?

[lee]

I ended up getting the Rockford M10......it is built identical to the Power T1-series that I have owned before, but with a much stiffer suspension. I didn't find any other free-airs that I liked the specs on. The worst part was getting it mounted. It weighs about 20 pounds.

Is that the same as the Rockford M110S4?