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Old 25th March 2008, 12:07 AM   #11
SY is offline SY  United States
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You want the air spring to be dominant in the AS. If the volume is large, the speaker suspension is dominant and you approach an infinite baffle.
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Old 25th March 2008, 12:12 AM   #12
Elbert is offline Elbert  Norway
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Hei Svante!

Yes, my software actually plots a response curve, and so far I've been aiming for a flat response......

Your point about allowing for a slightly sloping response and to have it "compensated" by the room response is very interesting!

But then again, how does one predict the room response? And what might turn out to be right for my current living room might be completely wrong if (when) I move to another house.... that's the tough one with low frequency audio, the source and the room is really part of the same equation....

The best bet is perhaps to go for a reasonably flat response and use an equalizer for tuning to what ever room they might end up playing in?
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Old 25th March 2008, 12:13 AM   #13
Elbert is offline Elbert  Norway
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SY,

Am I correct in assuming that the air suspension is mainly a factor in a closed box design?
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Old 25th March 2008, 12:13 AM   #14
GM is offline GM  United States
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Default Re: Mass loading..

Greets!

Hmm, using the posted specs I get a 100.08 L, 34.5 Hz F3 T/S max flat half space vented alignment and since this keeps it from exceeding the calculated Xmax enough to matter it's a reasonable recommended max Vb.

That said, this alignment tends to sound 'boomy' in many home layouts, so tuning it down around Fs in as much as 150 L seems a better choice overall.

WRT mass loading for LF/sub duty, i.e. limited to its pistonic BW (~414 Hz), no real downsides besides the efficiency loss as long as the mass loading is done in such a way as to not damage the suspension.

GM
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Old 25th March 2008, 12:21 AM   #15
Elbert is offline Elbert  Norway
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Hi GM!

Interesting your comment about space alignment... I somehow suspected this to be of relevance with regards to a vented box being smaller than the theoretical value i get with my software (which really doesn't have any specific input or options for alignment"

Regarding Mass loading, from what you're saying it seems like I'll be fine as I'm planning to use these woofers for pure "sub-woofing" duty anyway!

Guess I'll explore that avenue a bit further then...
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Old 25th March 2008, 12:28 AM   #16
SY is offline SY  United States
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Elbert, yes.

Mass loading may give nice-looking models, but needs to ba approached with great caution. Getting a lower small-signal f3 does not increase travel and power handling- remember that you need four times greater displacement at 20Hz as 40Hz. I'd still recommend using this driver for what it was intended- a high-efficiency mid and upper bass driver, not a subwoofer.
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Old 25th March 2008, 12:37 AM   #17
Elbert is offline Elbert  Norway
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SY,

You are of course correct in your observation that a lower F3 obtained by means of mass loading will still require more amplitude to maintain SPL, and I fully agree that this would be a dubious approach.


But if I use some mass loading to obtain a similar F3 in a smaller box (e.g. 100L) as i would obtain in a larger (e.g. 170 L) box without mass loading, wouldn't this be ok? except of course for the reduction in upper frequency, which is not a problem in my case anyway?

Or did I miss something out completely here.....
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Old 25th March 2008, 12:50 AM   #18
badman is offline badman  United States
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Ah, I wasn't thinking about the distinction between acoustic suspension and 'sealed'.

I like oversized sealed boxes.

Badman
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Old 25th March 2008, 01:31 AM   #19
Thawach is offline Thawach  Thailand
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Quote:
Originally posted by Svante
There are other free softwares that will give you a response curve instead, and in this case I think that I would go for a BR of ~90-120 litres tuned to 25-30 Hz.

This will give a slightly sloping response towards lower frequencies and this will fit nicely with the room gain.

svante if i chose that i will chose 120 L tuned to 25-30 L a slightly sloping response at low frequencies have a litle.

yeah why do they offline at all.



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Old 25th March 2008, 02:08 AM   #20
SY is offline SY  United States
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Quote:
But if I use some mass loading to obtain a similar F3 in a smaller box (e.g. 100L) as i would obtain in a larger (e.g. 170 L) box without mass loading, wouldn't this be ok?
Efficiency, power handling (as a function of SPL), and Q will all be different, no?
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