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RL-P18 meets the "DOH! button" - Page 7

post #181 of 330
11/7/07 at 8:08am
Quote:
Originally Posted by Willd View Post

We've already had first hand accounts of folks with similar albeit larger and lower tuned (by 2-3Hz) not bottoming out with a bridged ~2000W+ amp per Rl-p 18 playing WOTW.


who?

2kw on an LLT?
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post #182 of 330
11/7/07 at 9:32am
Quote:
Originally Posted by btp View Post

I'm just running one sub right now and really starting to wonder WTF was I thinking building two subs?!

All the panels and braces are cut for the second sub. I just thought I'd give myself a break from the late nights in the garage and have some fun with the first sub for a while. I was thinking about getting started on the second one the other day and I realized I cut the panels "wrong". I cut them EXACTLY as the first sub when what I really wanted to do was create a mirror image (as far as the port and port outlet is concerned). Not a big deal. I will just flip the sub over, so the top panel is on the bottom. Only difference would be the seams that are visible, as the front and top panel minimize the visible seams... however, it's all going to be painted with that Duplicolor bedliner product, so you'll never know the difference.

Hell yeah! Bust out the SPL meter and CRANK 'EM UP!

Seeing what a nice job you have done with the other sub, I am sure there will be plenty of guys willing to take the cut pieces for the second sub off your hands. For a guy with OCDin his sig, wont it bother you that the second sub isnt exactly what you wanted it to be?...
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post #183 of 330
11/7/07 at 10:01am
Quote:
Originally Posted by ssabripo View Post

who?

2kw on an LLT?

Blaser on HTShack.

Yes, approx.
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post #184 of 330
11/7/07 at 10:12am
Quote:
Originally Posted by Willd View Post

Blaser on HTShack.

Yes, approx.


And his is tuned around 14-15hz too. That means below Fb it has much less protection down low. Wonder whats worse, the excurson above Fb with 2k or excursion below Fb. Cause Ive got mine at 11hz and have had no ill effects just yet. I need more power.

Btw, 2k on a LLT has been tested with the TC2k by Illka on HTS. Wasnt that the 320L (?) tuned low clipping at 2k?
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post #185 of 330
11/7/07 at 10:16am
Thread Starter 
Quote:
Originally Posted by Willd View Post

Blaser on HTShack.

Yeah, but those are Egyptian watts.

No way I'd run that kind of power on WoTW without a serious HPF... 24 dB/octave, dialed in, and tested... that I know will limit the stuff under 10 Hz. Of course I'm pretty paranoid, neurotic, anal, etc., etc.
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post #186 of 330
11/7/07 at 10:50am
Quote:
Originally Posted by Scott Simonian View Post

And his is tuned around 14-15hz too. That means below Fb it has much less protection down low. Wonder whats worse, the excurson above Fb with 2k or excursion below Fb. Cause Ive got mine at 11hz and have had no ill effects just yet. I need more power.

Btw, 2k on a LLT has been tested with the TC2k by Illka on HTS. Wasnt that the 320L (?) tuned low clipping at 2k?

I think it was clipping. I am not sure if it has been completely established. I do know that Ilkka is saying the half-roll surround was actually the limiting factor in the 2Ks excursion, so it'd be a different ball game with the tall roll surround. I doubt he'll be able to test that particular sub again, but he may be able to test one of the 2Ks with the tall roll surround in the spring (if he still has them). It was 270liters @ 16.5Hz.

Quote:


Yeah, but those are Egyptian watts.

No way I'd run that kind of power on WoTW without a serious HPF... 24 dB/octave, dialed in, and tested... that I know will limit the stuff under 10 Hz. Of course I'm pretty paranoid, neurotic, anal, etc., etc.



Yeah, I don't blame you. Even though I am getting a pretty high powered amp for my 2K, I do plan on building Chuck's filter thing-a-ma-jig.
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post #187 of 330
11/7/07 at 4:10pm
Quote:
Originally Posted by btp View Post

I'm just running one sub right now and really starting to wonder WTF was I thinking building two subs?!


Dude!!!!
And your one of the ones that helped talk me into these monsters.......

Scott
Does homeowners cover damage caused by subs?...lol
I hope these don't knock the bricks off the walls.
Maybe if I had 2K each and tuned to 11, I could shake enough neighbors houses to trigger earthquake insurance.
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post #188 of 330
11/7/07 at 5:28pm
Hey if you're having second thoughts about that second sub I'll gladly take it off of your hands..
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post #189 of 330
11/7/07 at 8:38pm
Thread Starter 
Quote:
Originally Posted by Spezzy View Post

Hey if you're having second thoughts about that second sub I'll gladly take it off of your hands..

Not a chance! The first sub is getting lonely down there in the HT room all by itself. I better get crackulatin' on his/her partner in crime.
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post #190 of 330
11/8/07 at 7:31am
Thread Starter 
Question for you guys... as far as I can tell by watching cone excursion, the tuning on this first sub is damn close to 13 Hz. I was shooting for a 14.5 Hz tune, using 17 cubic feet net volume with a 35.25" long 8.375" internal diameter port. To the best of my knowledge, I got pretty close to those specifications in the actual "product", so... what happened?! Why is my tune so low? Just seems like it is off by quite a bit.

I suppose it's possible that I put too much polyfil in, but I know I have less than 5 bags (20 ounces each) in there, so I'm guessing under 6 pounds of polyfill. Maybe I should take some out and see what happens.
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post #191 of 330
11/8/07 at 7:47am
It's all about trial and error. Play with the poly and take some out.

This whole thing is not an exact science. Even manufactures say something and it's not exact. A car company says that this engine produces 200hp. Then when dyno tested and other tests, it's either lower or higher! Not only that, power can vary within the same engines made that day!
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post #192 of 330
11/8/07 at 12:44pm
Thread Starter 
That's what I'm going to do. If it was 14.0 Hz instead of 14.5, I wouldn't think so much of it. But it takes a pretty significant change in box volume or port size/length to go from a 14.5 to a 13.0 Hz tune so I am wondering what exactly is going on.

Does WinISD or Unibox account for the effect of polyfil or fiberglass to lower the tune? I know you can adjust damping (Qa, Qp, Ql) but I'm not seeing anything as far as how the fill makes the box "seem" larger.
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post #193 of 330
11/8/07 at 12:48pm
Quote:


Does WinISD or Unibox account for the effect of polyfil or fiberglass to lower the tune?

It does.
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post #194 of 330
11/8/07 at 3:07pm
Thread Starter 
Sorry... I had not looked at Unibox in a while, but now that I have it open... it's obvious that it does take the level of fill into account. Still doesn't seem to be enough to account for what I'm seeing, so I'm going to go home tonight, put down the crack pipe, and double-check my measurements.
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post #195 of 330
11/9/07 at 8:29am
Thread Starter 
Update: removed the driver and yanked a bunch of the polyfil out. Reinstalled and tested it again and it looks like the Fb came up to around 13.5 Hz. One thing I did notice is that my piece-of-crap signal generator is producing something that looks about halfway between a sine and triangle wave, so I can't say I really trust the measurement. I need to get a real signal generator (or use the sound card in my PC) and retest.
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post #196 of 330
11/9/07 at 9:50am
Take out all the fill and measure. If it hits your goal, then no fill. If it doesn't, put some in and repeat the procedure.
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post #197 of 330
11/9/07 at 10:25am
Quote:
Originally Posted by btp View Post

Update: removed the driver and yanked a bunch of the polyfil out. Reinstalled and tested it again and it looks like the Fb came up to around 13.5 Hz. One thing I did notice is that my piece-of-crap signal generator is producing something that looks about halfway between a sine and triangle wave, so I can't say I really trust the measurement. I need to get a real signal generator (or use the sound card in my PC) and retest.

The signal generator in roomEQ works well enough I think.
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post #198 of 330
11/9/07 at 12:08pm
Are you sure you put the glass pipe down?
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post #199 of 330
11/9/07 at 6:33pm
Here are my thoughts.. As your enclosure was optimally sized for your chosen subwoofer, no Polyfil is required.

As you already know, Polyfil lowers the air velocity within the cabinet giving the impression to the driver that it is in an enclosure of larger size. Since you designed the cabinet giving it optimal room (17 cu feet) this isn't a problem.

It also increases the damping factor which can be helpful in cases of poor bracing. In your case you had near perfect bracing.

Stuffing is common in commercial offerings as physical size limitations are a factor. However our DIY setups are much different. We over engineer and do it right from the start, designing our enclosures to optimal internal sizing.

In many cases stuffing in an adequately sized enclosure such as yours can actually detour performance causing unwanted incorrect tuning and lowered SPL.

I'd yank it all out and remeasure.
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post #200 of 330
11/9/07 at 8:35pm
Thread Starter 
Thanks for the added insight. I think I underestimated the effects of cabinet fill and I didn't fully grasp the reasons for using it (or not). I will probably build the second cabinet with little to no fill and see how that comes out.
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post #201 of 330
11/9/07 at 8:54pm
Yeah, I'd just stick to lining the walls.
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post #202 of 330
11/10/07 at 3:30pm
Treat those girls right and stuff em J/K

Would it be beneficial is this scenario where the box is large enough to still line edges, ports, and walls?
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post #203 of 330
11/10/07 at 6:16pm
Thread Starter 
I think I'll let the people here that know more than me answer that one. But for now I am taking the "less is more" approach to dampening material. For some reason I thought it was more necessary than it actually is. SOME dampening is probably a good thing, especially for higher and unwanted frequencies, but too much dampening just makes the sub less efficient and, as we've seen, the added fill can lower the tune more than you might want it to.
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post #204 of 330
11/10/07 at 6:21pm
Thread Starter 
I've spent the better part of the afternoon getting my PC hooked up to my entertainment system and getting acquainted with REW. So, without further adieu, here is my first REW graph with the mic about 2 meters from the sub on the armrest of one of the leather recliners.



For the most part I'm pleased with the results, although that big dip at 58.5 Hz is kind of annoying.
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post #205 of 330
11/10/07 at 6:58pm
Nice looking results. About that dip, have you tried playing with the crossover frequency and the phase yet?
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post #206 of 330
11/10/07 at 7:06pm
Great graph and results.

Of course, if you move the mic over a foot things change sorry don't worry about the dip especially if it is at armchair height.
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post #207 of 330
11/10/07 at 7:10pm
Is that graph with the calibration or not?
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post #208 of 330
11/10/07 at 8:47pm
Thread Starter 
Yes, the graph shows "corrected" readings using the calibration file for the Radio Shack digital SPL meter I have. The black line is actually the calibration curve for the meter.

For the sake of this measurement, I set the crossover to 200 Hz and switched the mains OFF so there is no chance for phase cancellation with any other speakers.
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post #209 of 330
11/10/07 at 9:01pm
Thread Starter 
Adjusted the mic position by moving it one chair over and pointing it up, maybe 60 degrees from horizontal. Previously the mic was horizontal and pointing straight ahead toward the projection screen and sub.

This graphs looks a lot better in the 60 Hz region.

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post #210 of 330
11/10/07 at 9:35pm
Damn! That is nice now.

I think I have to switch my mains off and try that approach...
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AVS › AVS Forum › Audio › DIY Speakers and Subs › RL-P18 meets the "DOH! button"