Who's afraid of the BIG BAD WOOF?

Early B. · « **Reply #20 on:** 28 Nov 2010, 04:46 am »

Quote from: Vr3 on 28 Nov 2010, 04:03 am

Just a FWIW --

I recently installed the 15" TC Sounds Passive Radiator in my Larger Subwoofer -- because to this day I have never not heard the original PR bottom and finally could take no more.

Were you using the "original PR" or Brian's PR designed specifically for the OMG driver?

Vr3 · « **Reply #21 on:** 28 Nov 2010, 05:01 am »

I was using the original since I just have the Megawoofers... Even with the Megawoofers -- that PR goes about 1/2 volume before basically destroying itself. The TC Sound PR has a far stiffer cone, far more linear travel and a far better tuning method.

I cant imagine using the stock PR or even one with extended travel on those TC Sound woofers - that cone would flex like putty!

Either way - I can run my sub at reference level now on even Last Airbender without PR issues - where as before half to 3/4 volume would have it flopping and making all kinds of strange destruction like noises.

jwalker · « **Reply #22 on:** 1 Dec 2010, 11:39 pm »

Quote from: Vr3 on 28 Nov 2010, 05:01 am

I cant imagine using the stock PR or even one with extended travel on those TC Sound woofers - that cone would flex like putty!

Passive radiator cones don't flex in the way that you are imagining. Active drivers are driven typically from the voice coil which is located near the center of the cone. The cone can flex due to unequal distribution of force which is concentrated near the center.

But passive radiators are excited by pressure changes inside the cabinet which results in an equal force being distributed over the entire cone area. So cone stiffness in the traditional sense shouldn't apply.

Vr3 · « **Reply #23 on:** 4 Dec 2010, 02:26 pm »

While I was being some what serious about the cone flex, it was more sarcasm than anything.

Lets rephrase, those TC Sounds drivers could invert the stock PR.

My PR moves maybe .5 - .75 inches total before the surround becomes an accordion. In even low volume passages my PR hits the back of the basket.

Since I changed over to the TC Sounds PR, I have clean (HIGH OUTPUT) usage into the 16-17hz range...

Brax · « **Reply #24 on:** 6 Dec 2010, 12:12 pm »

I thought running the TC Sounds PR in a down firing position was not recommended and adding weight (tuning it) would make the problem even worse. I presume it's the weight on the suspension that would cause the problem and induce sag in the suspension. I considered using PRs in my sub design but this design restriction steered me away from them (I went sealed).

I think Brian's PRs can run in a down firing position because the are much lighter in weight them most.

Early B. · « **Reply #25 on:** 6 Dec 2010, 12:56 pm »

Quote from: Brax on 6 Dec 2010, 12:12 pm

I thought running the TC Sounds PR in a down firing position was not recommended and adding weight (tuning it) would make the problem even worse.

Did this recommendation come from TC Sounds? If so, is there a link?

DFaulds · « **Reply #26 on:** 6 Dec 2010, 05:21 pm »

On the PE site there is a link to what is referred to as a "manual" and it states that the product warranty for their PR does not cover sag due to down or up firing mounting for extended periods.

While that isn't exactly saying that you shouldn't, it's seems good enough for me.

Brian Cheney · « **Reply #27 on:** 6 Dec 2010, 05:42 pm »

Our old style 15" PR had a 1/2" travel and a 1/4" bump on the basket. The new "big bump" PR has 1" travel and a 3/4" bump. This should be more than adequate to prevent bottoming.

We will go to a higher surround next time we order cone stock to allow even more travel.

The TC Sounds PR should be fine firing down unless loaded with a large amount of extra mass.

DFaulds · « **Reply #28 on:** 6 Dec 2010, 05:50 pm »

Brian, if the TC PR would be OK down firing, wouldn't it be a good fit for your subs? It's 3+" cone travel seems very well suited to the 3" peak travel on the LMS sub driver. Of course I have no idea of the actual tuning of your subs, but in general, doesn't the excursion of a PR exceed that of a woofer at tuning frequency?

Of course, maybe the TC PR would need too much added mass in order to be tuned properly.

Brian Cheney · « **Reply #29 on:** 6 Dec 2010, 06:01 pm »

I have TC PR's due in this week, so I'll let you know. Yes, the PR can indeed travel further than the active at the tuning frequency. I usually tune for a subsonic Fs on the PR.

John Casler · « **Reply #30 on:** 6 Dec 2010, 08:01 pm »

And the OMG (TC) PR can now be ordered for $150 upcharge.

Brian will be testing the PR for proper mass loading for each volume cabinet and they will come "pre-tuned" from the factory.

EDIT:

Please refer to Brian's findings below

Brian Cheney · « **Reply #31 on:** 11 Dec 2010, 10:41 pm »

After examining the TC Sounds PR's and consulting with Thilo, I feel they are not really a good match for our Larger subwoofer enclosure.

The TC PR's are very stiffly suspended, and designed to be driven by the high sound pressures inside smaller boxes. The lower pressure inside the Larger Sub would not generate the desired output level or low cutoff frequency. A high compliance PR like the Big Bump is required, although with more travel that the current suspension allows.

So, we are sourcing a "High Rise" cone with plenty of travel and a high, wide, flexible surround, at least 1" in each direction. This should be available by end of January.

In the meantime, there is a fascinating alternative : using the TC Sounds 15" active with no passive radiator at all. Instead, two very long 4" diameter port tubes (with flares on both ends) would tune the enclosure to 20Hz without EQ. We would remove the PR entirely, seal the cutout, remove the 12", install the port tubes where the two input terminal cutouts are located, and voila, a high output, high efficiency subwoofer retailing for $1200. Any Larger in the field could be retrofitted with a kit we could sell for about $600 including the TC Sounds 15", plugs for the 12" and 15" PR cutouts, and the two very long port tubes.

We can also sell a 3cu ft version of the current Dedicated Sub with the TC Sounds 12" and a single, long 4" port for $899.

Owners using the 500W or 1000W Dayton amps we like could also use the TC Sounds drivers in a sealed box with EQ applied at 30Hz to bring the F3 down to 20Hz. Given the excursion of these mighty drivers, this method gives the user the good transient response of the sealed enclosure with the first-octave cutoff of a relatively compact box.

Either alternative should be heaven for Subwoofers and lowbass lovers everywhere, whether they currently own a Larger Sub or not.

Early B. · « **Reply #32 on:** 12 Dec 2010, 12:07 am »

Quote from: Brian Cheney on 11 Dec 2010, 10:41 pm

In the meantime, there is a fascinating alternative : using the TC Sounds 15" active with no passive radiator at all. Instead, two very long 4" diameter port tubes (with flares on both ends) would tune the enclosure to 20Hz without EQ. We would remove the PR entirely, seal the cutout, remove the 12", install the port tubes where the two input terminal cutouts are located, and voila, a high output, high efficiency subwoofer retailing for $1200. Any Larger in the field could be retrofitted with a kit we could sell for about $600 including the TC Sounds 15", plugs for the 12" and 15" PR cutouts, and the two very long port tubes.

We can also sell a 3cu ft version of the current Dedicated Sub with the TC Sounds 12" and a single, long 4" port for $899.
.

Brian -- will the 15" TC Sounds and 15" PR work well in a 3 c.f. box?

Brian Cheney · « **Reply #33 on:** 12 Dec 2010, 12:32 am »

The 15" Pr and 15" active from TC will work well in a 3 cu ft box provided you find room for them. There's considerable depth to both. But you should be able to mass load the TC 15" PR with the supplied washers to get first octave bass in 3 cu ft.

Brax · « **Reply #34 on:** 13 Dec 2010, 10:02 pm »

To avoid issues with mounting the PR down firing, you could mount the driver down firing and the PR on the horizontal face. This would allow you to tune the PR by adding weight and not risk inducing sag into the suspension. You may need to replace the base to allow for the travel of the down firing woofer and I would add a base plate so the sound would not be absorbed by carpeting but reflect outward.

Brian Cheney · « **Reply #35 on:** 14 Dec 2010, 04:32 am »

Firing the active woofer downwards, towards the floor, will act as a lowpass filter for the shorter wavelengths. This is fine if you cross over at 100Hz and below.

A carpet will not provide significant absorption for bass wavelengths, so no worries there.

John Casler · « **Reply #36 on:** 14 Dec 2010, 10:22 pm »

Quote from: Brax on 13 Dec 2010, 10:02 pm

To avoid issues with mounting the PR down firing, you could mount the driver down firing and the PR on the horizontal face. This would allow you to tune the PR by adding weight and not risk inducing sag into the suspension. You may need to replace the base to allow for the travel of the down firing woofer and I would add a base plate so the sound would not be absorbed by carpeting but reflect outward.

Hi Brax,

As well, you can "flip" that and have the active(s) firing toward the ceiling, and the PR firing to the wall or forward, which ever loads the room better.

Just get 4 Hockey Pucks to set it on.

As a side note Hockey Pucks are also good spacers to place between equipment if you need better ventilation in yout stack on the rack.

I have seen them for like $30 bucks for 30 pucks

pjchappy · « **Reply #37 on:** 15 Dec 2010, 07:14 pm »

Quote from: Brian Cheney on 11 Dec 2010, 10:41 pm

In the meantime, there is a fascinating alternative : using the TC Sounds 15" active with no passive radiator at all. Instead, two very long 4" diameter port tubes (with flares on both ends) would tune the enclosure to 20Hz without EQ. We would remove the PR entirely, seal the cutout, remove the 12", install the port tubes where the two input terminal cutouts are located, and voila, a high output, high efficiency subwoofer retailing for $1200.

. . . We can also sell a 3cu ft version of the current Dedicated Sub with the TC Sounds 12" and a single, long 4" port for $899.

I am now in the process of bringing my Smaller Subwoofer with Megawoofer back to life. Sadly, it has been in storage for ~5 years and cosmetically is not in great shape. Although I don't want to put any significant money into it, such as adding the TC sounds 12", what would be the result of swapping out the PR for the seal and port? I plan on integrating the sub using measurements and DSP (Mini DSP with ability to do multiple PEQ points and steep filter options).

Paul

Brian Cheney · « **Reply #38 on:** 15 Dec 2010, 07:24 pm »

There's no need to replace the PR with a port on the Smaller. If your PR is in bad shape, let us know which active you have and you can buy a new PR for $48 plus shipping. The PR has the advantage over the port of being easy to adjust via putty pinching.

Vr3 · « **Reply #39 on:** 16 Dec 2010, 03:00 am »

Why would the TC Sounds PR with full mass in my Larger with the Megawoofers have usable output to 17hz and not with the TC Sound drivers?