How to tell if you are pushing the sub too far ? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 13 Old 08-16-2017, 01:31 AM - Thread Starter
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How to tell if you are pushing the sub too far ?

I built a approx, 7ft3 sealed SI HT-18 and I am running it from a bridged inuke 1000dsp............


I have been getting brave and cranking it up for the last few movies............it lights up 3 of the lights in the crazy bass scenes but has not been hitting the 4th clip/red light.



I have been adding more and more PEQ/DSP boost on the low end........


No clip lights and no crazy sounds from the sub yet.......but the cone is moving pretty good.


I just do not want to destroy the driver, but I have no idea how to tell if I am in trouble or pushing it too hard, other than bad noises from the driver or looking at the clip lights, which I am not getting either of.


I have some serious gain going and the output is way above what I got with the 12 inchers......help me not blow it up !


I have no idea what to look at or listen for.........it all seems good, other than the cone is really moving down low and the max watts I can put out is barely above the RMS rating of the driver.......


HELP!....

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post #2 of 13 Old 08-16-2017, 01:44 AM
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That box is a bit large for a single HT18. You may lose excursion control down low. That said, it has about 37mm of one way excursion before physically bottoming out where you can damage it. You'll likely hear the amp clip before you do any damage to the driver or distress it.
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post #3 of 13 Old 08-16-2017, 02:05 AM
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...build another one

TV: Panasonic P65ST60
AVR: Denon X-1000
Speakers: PSA MTM-210C, PSA MTM-210's, PSA MT-110's
Subwoofers: SVS PB-2000 x 4
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post #4 of 13 Old 08-16-2017, 04:43 AM
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Don't stop now.....keep going
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post #5 of 13 Old 08-16-2017, 05:57 AM
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The third light on a 1000 is probably only about 150watts.
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post #6 of 13 Old 08-16-2017, 08:32 AM
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...build another one
This!

Typed on a tiny keyboard, excuse any typos

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post #7 of 13 Old 08-16-2017, 08:37 AM
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If nothing else there is a small home built kit, led watt meter, a "Velleman K4307: Audio Power Meter Kit." It has 10 led over the range and therefore can at least give you a feel of power sent to the speakers, not just they ae clipping now so muyst be full power just before clipping. It connects across the speaker terminals at the speaker or at the amp and is otherwise not powered. Parts express as well as Velleman sell them for about $33 to $44 each plus shipping costs to your location. I got two of them to try to see what my front and surround speakers were actually receiving at normal and high listening levels. There are marked overlays for high power applications of 4 and 8 ohm speakers. The scale for 4 and for 8 ohm are provided in two levels depending upon a single resistor value. The high power scale 8 ohm version has an led at 5, 10, 20, 30, 60, 100, 200, 350, 550, and 1000 watts. All leds are red. For a 4 ohm driver there is an overlay which shows double of each of these values i.e., 20 watts thru 2000 watts. .

A lower power version of the settings resistor which I built for 8 ohm goes from 0.15 to 200 watts. If for 4 ohm you use the overlay from 0.3 watts to 400 watts. The kit contains an overlay for 4 and 8 ohms in both low and high range setup.
It is a great little unit and takes about half hour to build.
The only precaution is to only remove each part from the tape in sequence as it is called for . They are in a specific order in the tape strip but nothing tells you that. Just looking at the end part you can pretty mugh tell the direction you go. This is not needed for resistors if you have an ohm meter but for diodes and capacitors and transistors there are a couple of values and types and usually the average person does not have any meter to see what part you have in your hand. The markings on the faces of the transistors are tough to read so it is more important there to remove each transistor in order from the tape and install it in the next location. Circuit board and all parts (except a case if you want one) come in the kit. My subs have internal amps so it is useful for my bass and midrange speakers only. I found that my large front main speakers which are cut off at 60 cps by my AVR, a 25 watt peak was a real loud level. Efficiency is decent at 94 db/watt at one meter. I know this does not do exactly what you want but is a lot more detailed then any on amps which purely show clipping and maybe one or two levels below that. This 10 led scale is quite informative. At under $50 it is a nice toy.

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post #8 of 13 Old 08-16-2017, 01:18 PM - Thread Starter
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I am , I am.........


Probably 3 more ! There is reason they are only 36 inches tall, so I can stack em 2 high!


So this will make very recognizable bad noises and the amp will make noises before I destroy the sub ?


I have 16db of PEQ/DSP at 10hz, but it seems to like it and I certainly like it.....with no HPF.....

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post #9 of 13 Old 08-16-2017, 01:37 PM
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I am , I am.........


Probably 3 more ! There is reason they are only 36 inches tall, so I can stack em 2 high!


So this will make very recognizable bad noises and the amp will make noises before I destroy the sub ?


I have 16db of PEQ/DSP at 10hz, but it seems to like it and I certainly like it.....with no HPF.....
Yes. At the 24 second mark of this video, the voice coil bottoms out on the back plate of the motor. It's a metal on metal sound.


Same thing at the 17 second mark of this video.
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post #10 of 13 Old 08-16-2017, 01:41 PM - Thread Starter
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WOW.....I am not pushing things near as far as I thought I was.....my sub is not moving near that much and has never made that noise.......thanks!


That would certainly be audible and noticed by me since the sub is 10 inches behind me.

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post #11 of 13 Old 08-16-2017, 02:24 PM
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There are two things that wreak subs, excursion and heat. Determining heat can be tricky, think inverted cone and $20 laser thermometer. The vc-1 does this but voids your warranty.

There are two types of excursion events, average and peak. Peak is usually higher and only happens at the loudest part of the movie or a part that hits the boosted eq point. This is also tricky to determine.

Setting your gain correctly and/or applying a (proper) limiter... will fix the excursion problem. But you may have to suffer with weak bass on weak movies or unknown movies.

Doubling the subs reduces the excursion in half or doubles the spl. So adding more is a good way to not bottom.

You can also detect THD via a umik and rew rta. Although it only works well for sinewaves. For really loud systems (120db+) you'd need a termlab in nasa mode or an spl lab meter...
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post #12 of 13 Old 08-16-2017, 05:04 PM - Thread Starter
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Based on everyone here...a few more youtube vids and people running 1000 watts to these. I think I have been running these much easier than I first thought........I am still inside the safe zone I think, I sure have not bottomed it out yet and it seems like I am not pushing the excursion as much as I thought.


I am sure the second one will lighten the load and worry over hurting it.....



It seems pretty tuff and able to take a beating thats for sure, way more than I have been doing.......doubt they even recone these as cheap as they are ?

Link to budget Home Theater build

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post #13 of 13 Old 08-16-2017, 07:50 PM
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I am sure the second one will lighten the load and worry over hurting it.....



It seems pretty tuff and able to take a beating thats for sure, way more than I have been doing.......doubt they even recone these as cheap as they are ?
Yes, when you add a second one co-located, for the same SPL, the cone excursion will be cut in half.


That would be affirmative on the no-recone. Although, as cheap as they are, if you did manage to make the moving parts clash into the stationary parts, it would be cheaper than an evening out here:



Although from time to time, you might need to go there to get away from the shoe store and fat women trying to shove their hams into a size 5.....

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