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Old 11th October 2012, 08:48 AM   #31
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pretty sure in this instance the Lascala is actually going to be the loudest. please discuss if you feel otherwise.

RCW666, can you please go into a little more detail on what a QB5 II alignment is?
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Old 11th October 2012, 09:58 AM   #32
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You can find an article I wrote about them here....Satellites and Subwoofers

You can also compliance scale other drivers into these alignments.

What the group II ones do is to maximise excursion limited power handling so that the full voice coil and excursion limited power handling can be used.

In a 40 litre box the 12a reaches its rated 2.5mm. cone excursion with an f3 in the 100Hz. region and produces 120db. with 200 Watts.

In general these boxes can produce the same spl. as a horn in half to a third the volume, two 40 litre 12a boxes for instance will produce as much output as a horn that is at least 160=200litres in volume, they need more power but not that much, because if you use two of them close couples the output and increase by around 6db. in this region.
rcw

Last edited by rcw666; 11th October 2012 at 10:00 AM. Reason: punctuation
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Old 11th October 2012, 02:15 PM   #33
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The sealed cab i simmed in hornresp is 55L and in direct comparison to that the lascala is at least 10db louder than it through most of the useful range. I had a brief read on the alignment you propose but did not understand the maths behind it. Hornresp has proven to be quite acurate in its simulations provided driver data is entered correctly. Hence reassessing my data. Do you agree with the simulations i posted or do you still feel that the sealed cab would provide more outright volume/spl?
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Old 11th October 2012, 02:55 PM   #34
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The amount of sound you can get from a sealed box is nothing like that from a QB5, the reason is that the power output constant for sealed boxes is fixed at .8-.85 whereas if you look at that for the QB5 II alignments it is considerably more, you can expect it to be in the 30-50 region for a driver that has an f3 twice its free air resonance.

This is an increase in acoustic power for the same cone excursion of some 38 times, the delta 12a has no where near the linear cone excursion needed for a sealed box.

You do get an increase in on axis output with a horn, but its acoustic power output drops off above the drivers mass corner.
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Old 11th October 2012, 06:44 PM   #35
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For ported cabinets, you need to select for the combined output of the port and driver - I suspect you'll find your ported cabinets will go louder than the sealed version.

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Old 11th October 2012, 09:43 PM   #36
col is offline col  Australia
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Hi Robert,

Iv'e been reading your article on the ESP website. Very informative, interesting and well wrote.

Iv'e got 4 of these 12" P.Audio E12-250N that I pulled out of a set of sealed mid-highs. Iv'e tried them in a ported 50L and they were not much better. I would like to try and model them for a QB5 II alignment. Problem is My maths suck.

I'm wondering if you know of any software that will calculate a QB5 II enclosure? Looking at WinISD it's a shame that all development stopped as it could have been one of the alignments added to that.

cheers,
col.

Quote:
Originally Posted by rcw666 View Post
You can find an article I wrote about them here....Satellites and Subwoofers

You can also compliance scale other drivers into these alignments.

What the group II ones do is to maximise excursion limited power handling so that the full voice coil and excursion limited power handling can be used.

In a 40 litre box the 12a reaches its rated 2.5mm. cone excursion with an f3 in the 100Hz. region and produces 120db. with 200 Watts.

In general these boxes can produce the same spl. as a horn in half to a third the volume, two 40 litre 12a boxes for instance will produce as much output as a horn that is at least 160=200litres in volume, they need more power but not that much, because if you use two of them close couples the output and increase by around 6db. in this region.
rcw
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Old 12th October 2012, 02:37 AM   #37
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The only program I use is winisd.

Just put in the ratio between the drivers fs and the f3 you want, this is given in the tables.

Note that alignments are not chiseled in stone and there is quite a bit of leeway, for instance with that p. audio driver the alignment is close to the f3/fs one at 2.118, needing a Qt = .294.

If you use a 30 litre box tuned to 100Hz. with a filter at 100Hz. with a q=.5

For an input of 250W. the cone excursion is around 1.7mm. max.
rcw
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Old 13th October 2012, 12:11 AM   #38
col is offline col  Australia
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Hi Robert,

I'm wondering if we should hive this off into another thread? I think I'm going to give it a go. I played around in WinISD a bit last night and It's still not clear to me what I have to input into WinISD apart from the box volume, tuning frequency and EQ/filter. My inability to make sense of your tables maybe...

I have a 50L box with a adjustable 80mm vent. I could reduce the volume of the box by adding some "bracing", or can I align to the larger volume?

Click the image to open in full size.

Adjusting the EQ/filter in WinISD doesn't seem to change the modelled response?

cheers,
col.
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Old 13th October 2012, 02:05 AM   #39
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These are winsid simulations of a 30 litre box tuned to 100Hz...

For an input of 250 Watts the cone excursion is as shown, and the spl over this range is 120db.

The input filter has a q=.5, this is a second order L-R, it can also be done with two capacitors somewhere in the signal chain.
rcw
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Old 13th October 2012, 04:23 PM   #40
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just checked HR, the lascala cab with 250w driving the Delta12 makes 130db at around about 150hz, from 150-400hz its making 125db, and then it tapers off above 800hz.

im liking the idea of "focusing" the sound via a "waveguide" or horn path, as generally, off axis isnt important when the axis is focused on the D-floor.



and on a different note, i picked up a Behringer CX2310 active XO yesterday, so once i get the new psu for it, ill be hooking it up asap to see how much difference it will make to my reflex cabs.


going back to HR for a moment, my current cabs simulate at 92db@1w, and the LS sims at 102db@1w, so if 6db is thought of as twice as loud, wouldnt that mean that 10db would be nearly 4x louder??? can someone give me an idea/reference to this please? and, as to wether or not HR in this instance is at least 90% accurate? (because if it is, thats pretty dam good IMO.)
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