scoop for PD 1550

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   The answer to nearly all of your questions are, it depends 

The 1550 looks like a pretty decent driver for a rear loaded horn. Good Bl, low ish Qes. Enough displacement to make some SPL. The 45Hz Fs says you will not get much lower then that out of any bin using it, so you might as well design a plan or look for one that has this has an intended cut off frequency from the start. It will not need to be as long, or have as large a mouth as a bin intended to get lower. Or you could have a largeish mouth with less bins together to approach an ideal horn situation from another direction. 

Some wadding can help extend the length of horn that the air inside it sees, I recall reading somewhere that a typical transmission line length can be 80% of the theoretical length for cut off if you wad it properly. Wadding also helps damp higher frequency horn harmonics and resonances but if you have 180 degree bends in the folding they aren't a large concern anyway as they will naturally filter.

Definitely do not just put it in an 18" design. You will be wasting a lot of space and probably not get optimum performance because the volume of the chamber behind the driver will probably be too large to damp the driver motion well. 

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. 

Edited by odc04r - 14 January 2017 at 9:34am

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odc04r Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482	Post Options Post Reply Quote odc04r Report Post Thanks(0) Quote Reply Posted: 14 January 2017 at 9:30am
	The answer to nearly all of your questions are, it depends The 1550 looks like a pretty decent driver for a rear loaded horn. Good Bl, low ish Qes. Enough displacement to make some SPL. The 45Hz Fs says you will not get much lower then that out of any bin using it, so you might as well design a plan or look for one that has this has an intended cut off frequency from the start. It will not need to be as long, or have as large a mouth as a bin intended to get lower. Or you could have a largeish mouth with less bins together to approach an ideal horn situation from another direction. Some wadding can help extend the length of horn that the air inside it sees, I recall reading somewhere that a typical transmission line length can be 80% of the theoretical length for cut off if you wad it properly. Wadding also helps damp higher frequency horn harmonics and resonances but if you have 180 degree bends in the folding they aren't a large concern anyway as they will naturally filter. Definitely do not just put it in an 18" design. You will be wasting a lot of space and probably not get optimum performance because the volume of the chamber behind the driver will probably be too large to damp the driver motion well. 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. Edited by odc04r - 14 January 2017 at 9:34am

rastim Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 14 January 2017 Status: Offline Points: 30	Post Options Post Reply Quote rastim Report Post Thanks(0) Quote Reply Posted: 14 January 2017 at 8:13am
	Your build looks really good. Actually I´ve been staying on this Speakerplans many many years, not a member until now and have seen your post earlier too. So you are voting for 4530? I was alittle worried of if the motor is too strong for this plan but in your experience it is not so. So maybe I will build the 4530. But if anyone has an opinion, please write here!

JR.junior Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 14 December 2009 Location: Slovenija Status: Offline Points: 1789	Post Options Post Reply Quote JR.junior Report Post Thanks(0) Quote Reply Posted: 14 January 2017 at 7:38am
	I've build some time ago JBL 4530 replicas for PD154, it has even stronger motor as PD1550, dimensional the same. They're now n a club Driven by Crest CA12, ipmprresive SPL at least to say.. Here the build. http://forum.speakerplans.com/4530-replica_topic37990.html?KW=4530
	Support the scoop technology, larger mouth plays louder!

rastim Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 14 January 2017 Status: Offline Points: 30	Post Options Post Reply Quote rastim Report Post Thanks(0) Quote Reply Posted: 14 January 2017 at 6:59am
	Hello there. I have been using my PD 1550 in a cabin that was planned specially for that driver, a modified version of X1, somekind of a Letterbox. It really sounds nice and very very low. But now I want to build a scoop and wondering would a Fane- scoop (for 15") or a Jbl 4530 suit best for this driver? Will I be needing stuffing for scoop? Some are suggesting scoop needs it, someones opposite :) or Or would it be best just to scale down the original Superscoop plan for 18": s and stuck the 15" in? Thank you! Edited by rastim - 15 January 2017 at 5:06am