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scoop for PD 1550

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bob4 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 14 January 2017 at 7:13pm
according to an old german ("exponential" LOL ) horn book, the 4520 (JBL double 15" scoop) has a smoother  freq and phase response. But 4520's are a bad idea if the system needs to be mobile. 

If you build some single 15" scoops, do tell us about results :) 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 4:56am
Originally posted by bob4 bob4 wrote:

Originally posted by odc04r odc04r wrote:


Have a read of http://volvotreter.de/downloads/Edgar-Show-Horn.pdf - this paper by Bruce Edgar. It contains the design process for a front loaded horn intended for 50Hz lower Fc cut off. With a rear loaded horn there is no sealed chamber on the front of the driver for damping as this box volume is the outside world and essentially infinite. This changes the design a little but a lot of the thoughts in there are relevant to both front and loaded horns.

Erm, sorry I'm far from an expert, but that paper on FLHs is completely useless in this context…. 





No, it is not useless, read about the corner reflectors, which was one of the topics I asked. But thank you for joining and for the link!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 5:02am
As I said in my first post, my 1550 is now in a Letterbox and it really sounds deep and good. I don´t have anyway to measure the Hz, but it must be near 30Hz. I realise that with scoop it is not possible to get that low with 1550, but I really like the look of the scoop and will do that next.

I will tell here how things go, but don´t hold your breath, I am not going to hurry :D
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 5:09am
Can not get my pictures showing?

http://hornplans.free.fr/fane_scoop. - http://hornplans.free.fr/fane_scoop.html


http://en.audiofanzine.com/other-pa-live--speaker-cabinets/jbl/4530/medias/pictures/a.play,m.1363553. - http://en.audiofanzine.com/other-pa-live-sound-speaker-cabinets/jbl/4530/medias/pictures/a.play,m.1363553.html


http://hornplans.free.fr/4530. - http://hornplans.free.fr/4530.html







Edited by rastim - 15 January 2017 at 5:21am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 5:25am
What I wonder is; why in Super Scooper the panels that are 405 and 406 mm set like that and in 4530 the panel marked n:0 6 is tilted and not made of two panels? For extra stiffnes in a bigger box? 

Edited by rastim - 15 January 2017 at 6:41am
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JR.junior View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JR.junior Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 7:58am
Following exponential pattern.
Support the scoop technology, larger mouth plays louder!
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rastim View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 8:11am
Thank you all for the answers!

If someone wants, I am more than happy to see some plans made in Hornresp or similar with PD 1550 in a Jbl 4530 scoop :) can not use Hornresp myself....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 9:54am
Originally posted by bob4 bob4 wrote:

Originally posted by odc04r odc04r wrote:


Have a read of this paper by Bruce Edgar. It contains the design process for a front loaded horn intended for 50Hz lower Fc cut off. With a rear loaded horn there is no sealed chamber on the front of the driver for damping as this box volume is the outside world and essentially infinite. This changes the design a little but a lot of the thoughts in there are relevant to both front and loaded horns.

Erm, sorry I'm far from an expert, but that paper on FLHs is completely useless in this context…. 

Martin king has a long blurb about backloaded horn design on his page:




No it definitely isn't useless, but you need to be able to understand the differences in FLH and RLH to get the best out of it. As said if you assume the rear chamber volume is infinite (best modelled as slug of air mass in RLH case) and do not worry about the directly radiated part of output they are the same in concept.

I really just wanted to get the idea across that it was possible to do a couple of simple numerical checks from driver parameters and plan dimensions that give you an idea of how suited a driver might be to a particular combination
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 9:59am
Originally posted by rastim rastim wrote:

What I wonder is; why in Super Scooper the panels that are 405 and 406 mm set like that and in 4530 the panel marked n:0 6 is tilted and not made of two panels? For extra stiffnes in a bigger box? 


The super scooper has a longer horn path to load the driver at a lower cut off Fc as it is intended to be used with 18" drivers which typically have resonance at 30-35Hz. It is going to be an exponential type horn so for good performance the cross sectional area of the horn needs to vary with distance according to A(x) = Se^(mx) where A is horn area, S is throat area, m is flare rate, and x is distance. The flare rate at the horn throat also affects the low cut off. Those extra pieces of wood are in there to keep the horn area as a function of distance as close to possible to this relationship for best performance of the horn. The extra stiffness they provide to the cabinet is just a bonus! Although some may say they also represent wasted space that could be better used. Personally I think the bracing is good, not a lot of volume wasted there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastim Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 2:26pm
^ Thank you for information.

I will build only one scoop for the 1550, because it comes inside, so the starting point is not so good as it could be. More scoops with 18": s would do the job better :) but now I have to be satisfied with just one.

Maybe someday will build the whole system....................................................
rastim
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickyburnell Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 3:44pm
It's everything, not everythink!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JR.junior Quote  Post ReplyReply Direct Link To This Post Posted: 15 January 2017 at 4:05pm
Originally posted by rastim rastim wrote:

Thank you all for the answers!

If someone wants, I am more than happy to see some plans made in Hornresp or similar with PD 1550 in a Jbl 4530 scoop :) can not use Hornresp myself....

Search the forum. I've made many HR scoop plots, inbetween 4350, PD154,1550,158..

Edited by JR.junior - 15 January 2017 at 4:08pm
Support the scoop technology, larger mouth plays louder!
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