heart 21" scoop design

7 years 6 months ago #19706 by Reality Sound
21" scoop design was created by Reality Sound
I am currently playing around with the idea of designing a scoop around the 21LW1400. I can get them at an extremely good price.
Links are here ;-
www.usspeaker.com/eighteensound-21lw1400-1.htm
www.eighteensound.com/index.aspx?mainMen...oduct_simple&pid=196

GENERAL SPECIFICATIONS
Nominal Diameter 533 mm (21 in)
Rated Impedance 8 Ohm
AES Power 1400 W
Program Power 1600 W
Peak Power 7000 W
Sensitivity 99 dB
Frequency Range 24 - 2000 Hz
Power Compression @-10dB 0,6 dB
Power Compression @-3dB 1,5 dB
Power Compression @Full Power 2,2 dB
Max Recomm. Frequency 250 Hz
Recomm. Enclosure Volume 120 ÷ 500 lt. (4,24 ÷ 17,7 cuft)
Minimum Impedance 6,4 Ohm at 25°C
Max Peak To Peak Excursion 52 mm (2,05 in)
Voice Coil Diameter 100 mm (4 in)
Voice Coil Winding Material copper
Suspension Triple roll, Polycotton
Cone Straight ribbed, Carbon fiber reinforced Paper
THIELE SMALL PARAMETERS
Fs 28 Hz
Re 5 Ohm
Sd 0,1662 sq.mt. (257,6 sq.in.)
Qms 9,32
Qes 0,242
Qts 0.235
Vas 385 lt. (13,6 cuft)
Mms 296 gr. (0,65 lb)
BL 33,5 Tm

I will build with 1" ply, cab will end up being approx 2 ft wide, 5 ft high, & 3 ft deep.
Toying with the idea of upscaling/modding either,....
1/ Staips RS-18 full scoop
2/JBL 4520 or 4530
3/ Emmy

Thoughts?

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7 years 6 months ago #19707 by Reality Sound
Replied by Reality Sound on topic Re: 21" scoop design

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7 years 6 months ago #19709 by Dref
Replied by Dref on topic Re: 21" scoop design
That is going to be mad :P

The only input I have regarding design is use the VAS/4 rule and you probably already have an idea of what folding style you prefer the sound of. If you post a drawing of the design when you are done I will be happy to comment.

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7 years 6 months ago #19711 by Reality Sound
Replied by Reality Sound on topic Re: 21" scoop design
VAS/4 rule being?- with scoops and compliance is try to make the front chamber 4 times less than the Vas. So if the woofer has a Vas of 200 litres then make the front chamber 50 litres. Woofers with a high Vas of around 400 need a front chamber of around 100 litres to work well.

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7 years 6 months ago - 7 years 6 months ago #19712 by bitzo
Replied by bitzo on topic Re: 21" scoop design
I calculated the compression chamber volume using Leach formula and Keele using 80hz as upper rolloff frequency and the VAS/4 of that driver fall between the 2 calculated results.

I'm looking forward this thread.

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7 years 6 months ago #19713 by Dref
Replied by Dref on topic Re: 21" scoop design
Yep

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7 years 6 months ago #19715 by Reality Sound
Replied by Reality Sound on topic Re: 21" scoop design
What do you think the minimum cab width should be? Can I get away with 24"? I don't mind the change in height, or depth, but I need them (2 on there side) to be 48" as that is the height of my stage, and will be using them for center subs.

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7 years 6 months ago #19716 by bitzo
Replied by bitzo on topic Re: 21" scoop design
measure the door entrance. I think it's standard because of safety law.

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7 years 6 months ago #19719 by Dref
Replied by Dref on topic Re: 21" scoop design
2x1" ply sides + 21" driver. Should be doable to keep that under 24", but it will not look exactly like Tony's.

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7 years 6 months ago #19721 by Reality Sound
Replied by Reality Sound on topic Re: 21" scoop design
I am fine with that. I'm not trying to copy someones cab by any means. Tony's cab is 27" wide and I don't really want to go that wide. I might have to modify the depth to get the chamber volume needed. I'll probably crunch some numbers later.

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