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12 inch scoops, measured |
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Tonskulus 
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 Topic: 12 inch scoops, measuredPosted: 14 August 2019 at 12:42pm |
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Just got 2 x 12" scoops (empty). There has been some discussion about these, but I'm trying to take some mesurements out of these using different drivers.
First of all, these are very sensitive boxes for upper bass. Seriously, chest thumping mid bass even using very low power amps! Yes, there is no sub bass but still I'm impressed about the noise these produces even tho there are some bad things. First of all, final curve is made out of single 4mm ply (it does resonate and makes some nasty harmonics), need to make it stiffer or fill the empty space with foam. Rest of the enclosure is well made. I took some measurements using Dayton imm6 + cell phone (single enclosure). Distance 2 meters. JBL 2206H:  Acousto pro sh-1250 car subwoofer, high Qts and low BL, no where near optimal scoop driver.. but it works very well!! Actually better than JBL which is odd (however JBL can withstand more power):  'Notice: JBL = 8ohms, AP = 4ohms Enclosure itself:  Soon i'm going to make more measurements using rew-software and both scoops together etc.. Edited by Tonskulus - 14 August 2019 at 12:53pm |
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Ras Loud
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Joined: 08 January 2012 Status: Offline Points: 754 |
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Posted: 15 August 2019 at 3:11am |
This does not have to do with 12" scoops, but lately I was wondering about the necessity of filling empty space under the curves in scoops and I could not find much about it. Does it make any difference to fill the space in a well built 18" scoop? Some details about the scoops I am concerned about: they are properly made from birch and with a curve that consists of two layers bending ply that glued to each other and very stiff, together almost 18 mm. I built them with four wheels, so there is no slope/triangle shaped space under the curve like people often do when they use only two wheels. That makes the inner space under the curve bigger. There are also four half moon shaped braces under every scoops' curve which make the whole thing quite stable. I never recognized any resonating sound that would be different from other scoops, but I have also never heard the same scoops with the space filled up.
Edited by Ras Loud - 15 August 2019 at 3:12am |
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Tonskulus
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Posted: 15 August 2019 at 6:13am |
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I also wonder if it makes any difference to use just single 45deg piece of straight plywood instead of curved ply.
Try "kocking" that bent curve, if you hear any echo or resonance it might be good to fill that space with foam. Even if the resonance is out of speakers passband, it might add some harmonics. |
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studio45
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Posted: 15 August 2019 at 4:28pm |
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Using curves in a horn subwoofer reduces distortion - if you put a smooth curve in every fold, you will get a very low-distortion sub. It doesn't really make any difference to the 1-watt measured frequency response, but will sound nicer at full power.
However, I would expect that curving the folds nearer the throat make more difference than that final exit fold. So you would not notice much difference between a curved scoop and a straight panel.
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Spanners5
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Posted: 29 August 2019 at 11:06pm |
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but ...... if the curved bit was straight could you still call it a scoop? :)
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valve head777
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Posted: 30 August 2019 at 12:33am |
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in all seriousness, yes I think expanding foam will make a difference. That's the 12' version of the eminence design innit?
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Freedom of choice, choice of freedom.
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mobiele eenheid
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Posted: 30 August 2019 at 5:19am |
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A Thomas Danley anecdote is how he build a large bass horn with completely smoothed curves and measured it. It didn't change a thing in the bass range, except that performance was lowered because the curves effectively subtracted usable volume from the bass horn.
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Tonskulus
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Posted: 30 August 2019 at 5:59am |
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These are pretty close to eminence design but not quite 100%.
Anyway, not my cup of tea however only two different drivers tested. Honky, horrible midbass only.. well maybe I'll try to make some tweaks but I think there is not much to do to make these sound good? |
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paulus
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Posted: 02 September 2019 at 11:02am |
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Does it make any difference to fill the space in a well built 18" scoop massive difference done many a test and shocked people with the difference
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TRENDSETTER SOUND SYSTEM
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valve head777
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Posted: 02 September 2019 at 2:05pm |
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YYeah, it's not all about fundamental frequencies. Filling the void removes any resonance + dampens the scoop panel. Can only be a good thing...
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Freedom of choice, choice of freedom.
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dj jammin
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Posted: 02 September 2019 at 2:08pm |
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depends how you constructed the curved panel.. if its solid, its solid!
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Reverence Sound system
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studio45
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Posted: 02 September 2019 at 2:24pm |
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Try a peaking highpass filter? If you have any excursion to spare of course. I've been working on a super lightweight mobile 12" RLH, and with the right filter it *does* bass. Not sub, but plenty of bass.
Mine turns over at 50Hz, with about a +6dB peak there. It's 3rd order, made by combining a buffered 1st order RC highpass in series with a 2nd order Sallen-Key, with the S-K feedback resistor sized to give the required peaking characteristic.
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Tonskulus wrote: