Difference between Super Scoop and Folded Horn Subwoofers

Hello Guys!

I am fairly new to the construction of PA equipment, i have done a lot of work with Car Audio builds.

I am going to be performing at a couple of outside parties (fields) this summer and i am looking at getting some bass bins for my gear! It seems to me the best way to go would be either folded horn or super scoop!

However, i havent a clue what design would be good for me?

I currently have 2x JBL JRX 115 which are great! but i will need more energy especially if im outside.

I plan on building two bins using 2 x 18" Pa Bass Drivers around 1000 watt RMS with 4" voice coils.

Can you guys help me please!!!!!!!!

Superscoop:
[IMGDEAD]http://www.performing-musician.com/pm/jun09/images/thumbs/DIYPAcabs_04.jpg[/IMGDEAD]

Folded Horn:
folded%20horn%20sub.gif



PLEASE HELP!

Steve
-DubRoach Production
DubRoach Weekly HOME
 

Xoc1

Member
2008-11-08 8:25 pm
Devon UK
Your JBL JRX115 are fairly flat to 100Hz so there are many subs that will work.
The front loaded folded horn design you posted is not really suitable as it is designed to be used in a corner which tend to be in short supply outdoors. Front loaded horns tend to be used in multiples to produce high SPL levels - Think very big and loud.
The Scoop design can work and are certainly loud - They tend to have a big hole in the response about 80Hz so if you choose to build one take care that the frequency response will match your JBL mid tops
Speakerplans.com
A Scoop bin is closely related to a Tapped Horn. Tapped horns have a smoother response that would match you speakers better. Plenty of designs around here that would be suitable!;)
How much noise do you want to make?
It you want to avoid trouble and keep the neighbours happy you might be better off with a pair of reflex ported subs - they certainly would be the most compact option.
 
This is very accurate and helpful info thanks!!!

I would want to use these for a large outdoor party this summer (to give you an idea of size) for about 500-600 people. So i would want as much as possible!

What do you mean by Scoop design ???? this term confuses me! Could you give me an example? maybe an image ? that would be great!

I dont need to worry about neighbors ;) They all have pretty much no hearing at all anyway !!!
 

more10

Member
2011-02-08 10:00 am
Solna
Scoop is a nickname for JBL 4530 (single driver) and 4520 (dual driver) back loaded horns:

4520jbl-1.jpg


attachment.php


They look like big scoops.

Superscoop is the 18" driver version from speakerplans. Also a back loaded horn.

All backloaded horns have a design problem with cancellation when the output from the horn is out of phase with the front of the driver. At about 3 times the lowest frequency of the horn. But the backloaded horn will give 3 dB more output at the low end compared to a front loaded horn. The JBL 4530 has the first cancellation at about 150 Hz:

[IMGDEAD]http://img149.imageshack.us/img149/8316/jbl4530ua1.gif[/IMGDEAD]

A good compromise would be to build (or buy) several backloaded horns with a bit shorter horn path, like the JBL 4530. The JBL 4530 will be useful from about 50 Hz to about 140 Hz. You can stack them lying down in two rows with the driver end toghether to achieve "long throw". I believe 8 of these will achieve pretty good output outdoors.
 
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more10

Member
2011-02-08 10:00 am
Solna
A properly designed front loaded horn will sound better than a back loaded horn or a tapped pipe. It will have less output though, or be bigger than a back loaded horn or tapped pipe. If you want quality go for front loaded horn.

The warfedale is a front loaded horn.

You will need to decide on how low you want your system to go. The size and cost for a 20 Hz system is probably 4 times compared to a 30 Hz system.

Find a few plans, Speakerplans.com, PA Systems, sound systems, speaker boxes, live Sound - Dancetech, match them to you needs. A good plan should have advice on which drivers to use, and how many you will need for outdoors use.

Precision Devices makes excellent low cost drivers and are based in the UK.
 

tb46

Member
2006-01-09 7:04 pm
Texas
Hi ClackS02,

You can use Hornresp by David McBean to answer many of your questions.

Hornresp

Without a tool like this you will be talking mainly in generalities (which is fine too. :)). You need to share what you are actually going to use these subwoofers for, and with (the more detail, the better).

Regards,
 
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Hi ClackS02,

You can use Hornresp by David McBean to answer many of your questions.

Hornresp
Regards,

Thank you :)

A properly designed front loaded horn will sound better than a back loaded horn or a tapped pipe. It will have less output though, or be bigger than a back loaded horn or tapped pipe. If you want quality go for front loaded horn.

The warfedale is a front loaded horn.

You will need to decide on how low you want your system to go. The size and cost for a 20 Hz system is probably 4 times compared to a 30 Hz system.

Find a few plans, Speakerplans.com, PA Systems, sound systems, speaker boxes, live Sound - Dancetech, match them to you needs. A good plan should have advice on which drivers to use, and how many you will need for outdoors use.

Precision Devices makes excellent low cost drivers and are based in the UK.

Could you give me an example of a front loaded and a tapped pipe? I need it to be LOUD for outside and large halls. I will be playing electronic music, from house to Dubstep/Trapstep.

I just really dont want to spend money building something that will be no good! as you can imagine ;) I appreciate your help !
 

more10

Member
2011-02-08 10:00 am
Solna
Rog Mogales 1850 horn is a front loaded horn:

1850horn.jpg


It is called front loaded because the driver has a back chamber and the horn is in the front of the driver.

A front loaded horn is good because there is only one source for the sound, through the horn. This kind of horn will work for about 3 octaves.

Another one is the lab horn:

[IMGDEAD]https://www.prosoundweb.com/lsp/3d1-4-23-02.jpg[/IMGDEAD]

That one is actually very cleverly designed.

Martinssons tham15 is a typical tapped horn:

THAM15MKII_BUILD.JPG


A tapped horn is a tweak on the back loaded horn. It has two sound sources, the back of the driver through the horn, and the front of the driver. The sound from the back will be delayed relative the sound from the front, you will hear everything twice with small delay. This kind of horn will work for about 1½ ocaves. This kind of horn has the advantage of giving more output in the low end compared to a front loaded horn.

The horn path length is determined by the lowest reproduced frequency, it needs to be 1/4 wave long. For 20 Hz the path needs to be 344/20/4= 6 meter long. The horn opening need to be a full wave in circumreference for a horn suspended i free air. 344/20 = 17 meters. Diameter will be approx 5 meters. If placed on the ground you can do with half the area. Horns going down to 20 or even 25 needs to be very large. This kind of horn will have a bandwidth of full 3 octaves, that is 20-160 Hz.

In order to make the horn smaller, you can make the horn opening much smaller, it will be more like a pipe. This is how the tapped horns work, they should be named tapped pipes instead. The pipe will have much less bandwidth say 20-60 Hz. It will be very large anyways. If you need to reach 100 Hz, the lowest frequency of this kind of horn will have to be 35-40 Hz.

Yet another solution is a front loaded pipe, a long pipe with small exit area and a back chamber, like this one I built:

[IMGDEAD]https://dl.dropbox.com/u/106944188/image024.jpg[/IMGDEAD]

It is still bandwidth limited (using hifi criteria) to about 2 octaves.
 
This is only true if you use a classically defined horn flare. As I've mentioned several times, a front loaded 1/4 wave resonator (the small things that most people call front loaded horns) don't need to be any larger than tapped horns for the same spl and low corner. I can actually usually get 2 db more out of front loaded 1/4 wave resonators than tapped "horn" (with same volume and low corner) AND flatter response but sometimes it takes an unusual flare geometry to get there.
 
This is only true if you use a classically defined horn flare. As I've mentioned several times, a front loaded 1/4 wave resonator (the small things that most people call front loaded horns) don't need to be any larger than tapped horns for the same spl and low corner. I can actually usually get 2 db more out of front loaded 1/4 wave resonators than tapped "horn" (with same volume and low corner) AND flatter response but sometimes it takes an unusual flare geometry to get there.
Just a Guy,

Using Hornresp simulations I found the same thing as what you just wrote, while the actual FLH build measurements came out far less than predicted.bI spent extensive time tweaking the Domino DFLH, it had more upper output than a TH, but less LF.

Do you have an actual measured comparison of an actual build that actually shows a FLH that puts out 2 dB more LF level than a TH of the same volume using the same driver?

Art
 
My primary experience is Hornresp simulations.

My secondary experience is with front loaded 1/4 wave "horns" and tapped "horns" that I've built. In all horns I've built, the measured response almost exactly overlays the simulation BUT I don't have an spl calibrated mic and I haven't built a flh and tapped horn specifically to test this case (same volume and low corner).

Regardless of the fact that my mic is not calibrated, the sims overlay the measurements almost exactly, so unless the entire bandwidth is lower than predicted, in my experience there's no reason not to trust Hornresp for any alignment.

I'd like to look over your results if you have published them. Your experiences don't seem to match mine.
 
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