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  Excursion - Huh? 
 
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Rooin Mar 23, 2005, 12:57pm EST Reply - Quote - Report Abuse
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Ok, I know over excursion of a sub is bad, but can you give me a stripped down vs of how to detect/prevent over excursion?

I myself dont do much work with HTS (and subwoofers) for that matter. Im a Audiophile, but I tune mainly into car audio, where in most cases, your trying to get as much "Bump for your buck" as you can.

How do I know if Im causing to much excursion on a subwoofer? I mean other then the noticable "sound" a sub makes when its being stretched beyond its manufactured intentions.


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"Even Satan wouldn't use customer service as a form of punishment." - Lucas http://www.ctrlaltdel-online.com
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Sander Sassen Mar 23, 2005, 03:22pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
You'll hear it, if you push it far beyond the limit it introduces higher harmonics which aren't in the original recording, sounds a bit like amplifier clipping. Secondly you'll end up damaging your drivers because your voicecoil will hit the pole plate when going backwards and when going forward it will push the rubber surround beyond its limit. In the long run this will reduce the mtbf of these woofers, or cause for the voice coil to misalign. But to be sure you can measure the maximum excursion and compare to the manufacturer specification, it is easier to model the box though and make sure you're within the limits.

Sander Sassen
Editor in Chief - Hardware Analysis
ssassen@hardwareanalysis.com
Rooin Mar 23, 2005, 03:40pm EST Reply - Quote - Report Abuse
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Edited: Mar 23, 2005, 03:46pm EST

 
>> Re: Excursion - Huh?
How do I measure it? Were not talkin holdin a ruler up to the sub and watchin how far it punches are we?

Well in the case of these subs, they reccomended a 1.25 cft Sealed Enclosure, me an my friend were to lazy to build a box to the "exact" specs so we bought one, dang close at 1.3 cft.

The sub(s) are a 1000w (500w RMS) Dual Voice Coil Setup 4ohmx2 (wired down to 2ohms each)
we have a amp that will push 400w RMS x2 @ 2ohms

The subs pound, but Im worried we maybe over doin them a bit, but im not sure. The bass is so loud, its really hard to hear any strain on them. An the response an sound is great. Is it possible to feel or see over excursion ? Before its to late? I know we over did it if the cone blows out :S

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"Even Satan wouldn't use customer service as a form of punishment." - Lucas http://www.ctrlaltdel-online.com
Rooin Mar 23, 2005, 03:44pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
Oh, another thing.

Can you cause over excursion, without going over recommended wattage? or visa versa?

because as I noted before the subs are rated 500rms (1000w MAX)

with an amp that will do 400 RMS only....

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"Even Satan wouldn't use customer service as a form of punishment." - Lucas http://www.ctrlaltdel-online.com
Sander Sassen Mar 23, 2005, 03:48pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
No, there's no 'feel or see' way of determining over excursion. For car audio you can usually got by a gutt feeling, if you think you're pushing it too hard you probably are. There really isn't much you can do other than calculate or measure the maximum excursion. Do this with a tone generator, http://www.nch.com.au/tonegen/, at a low frequency (5...10Hz) and disable the rumble/subsonic filter on the amp, attach a piece of a ruler to the center of the cone and measure against a fixed point.

Sander Sassen
Editor in Chief - Hardware Analysis
ssassen@hardwareanalysis.com
Sander Sassen Mar 23, 2005, 03:53pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
Oh, you can easily push it beyond the max excursion even with a small amp, 50-watt for example, it al depends on what enclosure it sits in and what the specifications of the woofer are. Just look at some of the graphs in this article again. For the vented and passive radiator box you'll see just 160 and 120-watts are needed to get close to maximum excursion, keep in mind that this woofer is rated at 300-watts nominal. Hence feeding it with 300-watts will push it far beyond maximum excursion when you run it in either one of these enclosures.

Sander Sassen
Editor in Chief - Hardware Analysis
ssassen@hardwareanalysis.com
Rooin Mar 23, 2005, 04:01pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
Well, with different sub specs, and recomendations

in this subs case, it recommended a sealed 1.25 cuft enclosure.

we placed it in a 1.3 cuft enclosed chamber.

That .5 over lap on size, can that be what allows the over excursion?

Ive been told by a Pro DB Dragger, that its better to go OVER recomended size, then under it.

BTW:
With that Tone Software, How spendy of a input device am I going to need?

only Mic I have is a cheapo thing from a retail store, nothin fancy.

and how am I to ensure that Im goin 5-10hz during the testing, for the test..

================================================================
"Even Satan wouldn't use customer service as a form of punishment." - Lucas http://www.ctrlaltdel-online.com
Sander Sassen Mar 23, 2005, 04:07pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
That software will output a sine/square/sawtooth wave to your soundcard output, it'll also let you record it as a wav if needed. I usually have my notebook with me when doing measurements, but you could also record the needed 5 or 10Hz sine to a wav and convert to MP3 and use your MP3 player as a sub input. Simple really, and works just fine.

Sander Sassen
Editor in Chief - Hardware Analysis
ssassen@hardwareanalysis.com
Rooin Mar 23, 2005, 04:45pm EST Reply - Quote - Report Abuse
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>> Re: Excursion - Huh?
Well I have a laptop to use.


and I can burn the sound file to CD for playback

what do I want to use

sine ? it sounds like the most logical to use.

================================================================
"Even Satan wouldn't use customer service as a form of punishment." - Lucas http://www.ctrlaltdel-online.com
OCGW Mar 23, 2005, 07:04pm EST Reply - Quote - Report Abuse
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Edited: Mar 23, 2005, 07:06pm EST

 
>> Re: Excursion - Huh?
I built several speakers for my church

I think the most important aspect of a woofer is it spl/w/m rating

sound pressure/ watt/ meter rating (sensitivity)

Any quality subwoofer w/ over 100db spl/w/m WILL pound the walls w/ a normal amp

IMHO

OCGW

PEACE


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