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post #1 of 25 Old 03-06-2012, 10:23 PM - Thread Starter
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I have bottomed this subwoofer out already and you will be happy to know that cone dents on the 11" spider box before the coil hits the back plate, which is a good thing IMO (bottom less design, check!)




I'm finding that the iTech-8000 likes to produce more current than voltage, and therefore does better in 2-ohm mode than 4-ohm, the amp is 2-ohm stable in bridge mode but I really wouldn't recommend doing that.
Have it on a 240v/60hz line to squeeze every last drop of PFC power off the pole that I can.
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as for the LG Clone... I have no idea what it can or can't do, or what mode it likes best.
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post #2 of 25 Old 03-06-2012, 10:31 PM
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How do you have it wired in 2 ohm?? its a 2 ohm DVC sub. I am running mine 1 ohm in the car.

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post #3 of 25 Old 03-06-2012, 11:05 PM
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hmmm I could have sworn that is has been mentioned by a few people that you could damage these.

I am thinking your 20hz highpass is really whats saving them. How big is that enclosure?

Even modeled at 8ft3, 6000 watts puts it right at xmax with that 20hz HP. The xmech isnt that far off from xmax IIRC but you still have some room.
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post #4 of 25 Old 03-06-2012, 11:11 PM - Thread Starter
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Ah yes sorry this is 1-ohm, I stand corrected.

For a time I was using both channels of the amp in dual 2-ohm, and somehow that got stuck in my head
(But that is how you'd do that, which this is not.)
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post #5 of 25 Old 03-06-2012, 11:16 PM - Thread Starter
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box is 23x23x24.5 with 2.25" thick baffle inset.

So it's something like 6 cubes.
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post #6 of 25 Old 03-06-2012, 11:28 PM
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You realize, that having the cone impact the spider support does not make this a bottomless design, right? Having a design that damages the speaker when pushed too hard is anything but bottomless.
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post #7 of 25 Old 03-07-2012, 12:23 AM - Thread Starter
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There is no such thing as true "bottomless", everything has it's limits.

So the only solution is to turn it down, apply filters, and buy multiples.

I would recommend gluing some foam around the hard plastic edge, if anyone plans on pushing this thing to its absolute limits; soft limiter
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post #8 of 25 Old 03-07-2012, 07:43 AM
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Correct...There is no true bottomless design. 5400 cracks the spider spacer with the cone. If it hits hard enough it will mushroom the cone.
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post #9 of 25 Old 03-07-2012, 07:45 AM
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Quote:
Originally Posted by BassThatHz View Post

There is no such thing as true "bottomless", everything has it's limits.

Driver design is not my forte, however wouldn't a under-hung motor design, with significant Xmech/Xmax, be designed in such a fashion as to be considered bottomless? Whereas magnetically, the travel couldn't encounter soft part asymmetry/limits, let alone hard bottoming such as a coil hitting a back plate or spider hitting the top plate.

Is this correct thinking?

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post #10 of 25 Old 03-07-2012, 08:27 AM
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Aren't the the JBL GTI15's considered "bottomless" because of the differential drive?
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post #11 of 25 Old 03-07-2012, 09:42 AM
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Quote:
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If it hits hard enough it will mushroom the cone.

Been there done that.
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post #12 of 25 Old 03-07-2012, 12:16 PM
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Been there done that.

pics
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post #13 of 25 Old 03-07-2012, 12:59 PM
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pics

A bridged PL9.0 + a bonehead over-look on the gain knob =





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post #14 of 25 Old 03-07-2012, 01:14 PM
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you did this on your new AIY build already?

(European models do not accept banana plugs.)

 

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post #15 of 25 Old 03-07-2012, 01:28 PM
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you did this on your new AIY build already?

lol No, a few years ago during my 1st DIY venture.
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post #16 of 25 Old 03-07-2012, 01:31 PM
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lol No, last year during my 1st DIY venture.

I was about to say, dayum, that didnt last long

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post #17 of 25 Old 03-07-2012, 03:15 PM
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Quote:
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I was about to say, dayum, that didnt last long



The twins are up and running and kicking some major booty! Been playing around with the settings and I think I finally got them all dialed in. Last night was the first time ever I heard our home make some weird rattling/creaking noises. It was great!
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post #18 of 25 Old 03-07-2012, 03:38 PM
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Thanks, was looking for those pics to show someone once, but couldnt find.
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post #19 of 25 Old 03-07-2012, 04:31 PM - Thread Starter
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Looks like they need to add a fifth magnet slug and get a basket that is another inch deeper to avoid this situation.

Ideally the only thing that should hit its limit is the surround; given the price of these things, one would think it wouldn't be anything BUT perfection.
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post #20 of 25 Old 03-07-2012, 05:49 PM
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I want a muscle car that doesn't crash!
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post #21 of 25 Old 03-07-2012, 05:56 PM
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Quote:
Originally Posted by BassThatHz View Post

Looks like they need to add a fifth magnet slug and get a basket that is another inch deeper to avoid this situation.

Ideally the only thing that should hit its limit is the surround; given the price of these things, one would think it wouldn't be anything BUT perfection.

If you want absurd excursion, get an xxx. However, you kind of have a point about the cost.

On the other hand, these are super low distortion, very linear, and don't drop off nearly as hard as the XXX do. Altering the suspension may change this.

Either way, a sensible high pass filter should generally prevent this from happening.
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post #22 of 25 Old 03-07-2012, 07:03 PM
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Quote:
Originally Posted by FOH View Post

Driver design is not my forte, however wouldn't a under-hung motor design, with significant Xmech/Xmax, be designed in such a fashion as to be considered bottomless? Whereas magnetically, the travel couldn't encounter soft part asymmetry/limits, let alone hard bottoming such as a coil hitting a back plate or spider hitting the top plate.

Is this correct thinking?

There is no simple formula, but it is certainly possible to make a driver with a "soft bottom" where no mechanical contact is made, and the parts effectively stall out. Ultimately you need enough mechanical clearance for the suspension (preferably the spider) to stiffen sufficiently while having the BL of the driver drop sufficiently to create a stall point where the motor can't push past the stiffness of the suspension.

The tough part lies in having enough clearance but also enough linear travel. Typically you have to give up some linear travel or go to a progressive spider which works just fine, but does make a harsher (higher order distortion) when it gets into the steep part of it's Cms curve. A "linear" spider sounds more benign when driven to limits, but also allows more travel.

At some point you also have to make a call of how durable is durable enough? Car audio needs free air durability to very high power, where a driver always living in a sealed box of known size range requires much less.

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post #23 of 25 Old 03-07-2012, 09:30 PM
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Use limiters guys! This stuff is not cheap.

The negative BL (diff drive) or a breaking circuit is a great way to protect everything but again - adds tons of distortion and doesn't give any advantage over a limiter imo. Its similar to a very stiff spider.

Newer 5400's will have a slightly shorter spider spacer to prevent this, but you'll still be able to slam the coil into the t-yoke at -1.875" rear travel.

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post #24 of 25 Old 03-07-2012, 11:42 PM
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Quote:
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Use limiters guys! This stuff is not cheap.

The negative BL (diff drive) or a breaking circuit is a great way to protect everything but again - adds tons of distortion and doesn't give any advantage over a limiter imo. Its similar to a very stiff spider.

Newer 5400's will have a slightly shorter spider spacer to prevent this, but you'll still be able to slam the coil into the t-yoke at -1.875" rear travel.

Kyle,

What's the clearance on the 2010 versions before impacting the spider spacer?
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post #25 of 25 Old 03-08-2012, 09:07 AM
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Like Mark said it is possible to make drivers that soft bottom and there are quite a few examples out there. Its a trade of as usual though. If you increase mechanical clearances you end up with a deeper driver and a heavier one. Look how deep some of these are already. You also end up with a longer former which causes more moving mass which lowers efficiency and introduces more possibility for rocking at high excursion. If you have your motor force drop off quickly and the suspension tighten sooner then you lose some of the xmax and increase distortion. Tradeoffs as usual.
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