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Discussion in 'Speakers & Subwoofers' started by BraveHeart123, Oct 19, 2012.
Can you pls state as to why Crown XLS2500?
Any Crown is better than any Behringer. Behringer is really just a knock-off of someone else's design.
With respect to quality - I agree absolutely. It is important to note however that many of Behringer's EQ products actually have noise floors just as low as their counterparts from Crown/QSC. Not all - but a good number. Take each purchase by itself, do your research on the specific model, and make your decision based upon all the factors. I don't think you really sacrifice any "SQ" going to a Behringer for a subwoofer - while I would heartily agree that's a risky proposition for your mains.
I am using Crown xls1000 on a less than perfectly designed DIY car sub and it does a tremendous job. Now I wana make 2 sealed subs and run off xls2500, one on each channel. xls1000 just doesn't cut it for me to run 2 subs.
Before the final build, I wanted to put my calculations to test. WinISD suggested 23.6L (0.83 cu ft) sealed box dimensions. I calculated the driver volume at 6.8L through the following formula;
Pi x driver_radius ^2 x driver_depth
I added 6.8L to the suggested box volume by WinISD and total vloume came up at 30.4L (1.07 cubic feet) with -3dB point at 34 hz. Got the box made by a carpenter with cheap chip board. I slapped the driver in and hooked up the voice coils in parallel. Then I removed the high pass filter that was set at 50Hz on Crown xls1000 and tested the sub with crown in bridged mono mode at 1100 watts.
Although the sub performs extremely well in sealed box, but the driver still unloads at below 35hz and moves freely with no control over the excursion. Although, you said a sealed sub doesn't require subsonic filter. What could be the reason here???
Is it the bigger box dimension than what was suggested by WinISD?
Is there an air leak in the box and it is not properly sealed?
Am I overloading the driver; though it is rated at 800 watts rms? ..... I think 1100 watts at 4 ohms ain't going overboard that much.
Or am I doing something wrong here??
Pls suggest. I will do the final build after I completely test the sub in live environment.......one thing more.....driver doesnt unload when I run the amp in stereo mode but it only offers 550 watts at 2 ohms.
1. Larger enclosures just lower the final Qtc. There should be no drastic change at 35 hz when using a sealed box. Excursion should increase exponentially for every octave you drop. Play a 70hz tone and get 4mm of excursion. A 35hz tone needs 16mm of excursion to reach the same SPL. A 17.5hz tone will 64mm of excursion. Obviously, that would destroy the driver.
2. Entirely possible. Most air leaks are around the driver to enclosure seal. I use closed cell foam weatherstripping. You don't have a Lowes or Home Depot so check your local home improvement stores. As someone so knows NOTHING about Pakistan, I'm not sure which store near you will carry something like this.
3. That's the thermal rating of the driver. That's the amount of power over 5 minutes to 30 minutes (time depends on manufacturer) that it takes the adhesives to melt. It has nothing to do with how much power it takes to drive to full excursion. That can be plotted in WinISD.
4. Look closely for leaks. You are probably over powering the driver for the really low bass.
My TC-3000's can handle about 2000w of power. I feed them 800 because they can reach xmax at 10hz with only 800 or so watts.
I found something like closed cell foam weather stripping and sealed the box sub cutout where the driver sits. I removed the HPF set at 50 hz and fed full signal to it in bridged mode. The response is much better now but the driver still bottoms out near 40Hz.
I checked the excursion graph in WinISD. This Pioneer driver reaches its Xmax (9.8mm) at 61hz. At 40Hz it is roughly 25mm, which is more than twice the one way linear movement. So the driver is way over-excursing and crossing its mechnical limits. I think HPF engaged at 50Hz on the amp is the only choice I am left with, although the excursion is 16mm at 50Hz which is 6mm more than the Xmax but the driver doesn't bottom out at reference volume even with 20dB transient bursts during action scenes.
Any thoughts on this??
Edit: With HPF engaged at 50Hz, the excursion falls to 12mm till 45Hz.
Simulations aren't 100% correct but you are getting a good idea of how much power it takes to move the driver to it's limits. In reality, you are only using 10 to 20 watts with some 100 to 200 watt peaks for average listening.
Have you heard the mechanical noise of bottoming out the driver?
It's a mechinal thud. It's like somebody hitting a mallet against a wooden door in succession. I dont know if it is termed as mechnical noise or something else.
That sounds like the triple joint hitting the top plate rather than the voice coil hitting the back plate. Either way that driver will not last long if you continue to do that.
Here's what the coil sounds like when it hits the back plate -
Have you ever contacted these guys? https://www.facebook.com/teinuro.multimedia I ask because they build subs for TC Sounds - http://www.parts-express.com/brand/tc-sounds/150 In certain parts of the world, they are sold under the Teinuro brand. http://www.teinuro.org/product_list4a35.html?bid=43
Thanx Robert for your patience and on-demand intermittent advices. I will check out the websites u mentioned.
Anyway, I ended up engaging 50Hz HPF on crown, tamed both subs (Pioneer, and SUB-12) in REW, and shot for a 7 dB hard-knee curve on the 4-point averaged response. The result is really scary....amazing.
I sure will bug you on my next DIY project when I lay my hands on Alpine SWR-12D4, which will be available here this coming January. Many Thanx
On a side note, you once mentioned u use Dayton Audio Testing System. I was wondering I also buy it. Coz the devil inside says....take the SUB-12 apart and use its driver for DIY sub. I'm only hesitant coz I do not know its T/S parameters. So, was wondering I should get DATS. How difficult is it to use??
That's why I do this. It's frustrating to deal with the differences in time, available products and sometimes the language (not in your case). But it's worth it when someone says this.
For 1 woofer, it's not worth it. Heck, find someone over here that has both the DATS and knows someone with that sub. It is easy to use. Makes WinISD look like brain surgery. With practice, you can test a driver in under 20 seconds.
I just wana keep it and also to confirm the published T/S parameters. At times the published ones are wrong. For example, the pioneer driver I am using has 89dB sensitivity published in the parameters. Whereas, WinISD calculated it to be 76dB. It is a huge difference.
It depends on how they measured. If they say 1 watt at 1 meter then it might be correct depending on the impedance. At one ohm, 1 watt is about 8 volts (calculated in my head). If they say 2.83v at 1 meter then they are staying consistent with their measurements. 1 watt at 4 ohms is 2.83v. If you want to compare the sensitivity of a 1 ohm sub to a 4 ohm sub, you must look at the voltage being used and not the wattage.