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Old 13th March 2013, 09:37 PM   #21
Xoc1 is offline Xoc1  United Kingdom
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Quote:
Originally Posted by ClackS02 View Post
Hello Guys!

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

I plan on building two bins using 2 x 18" Pa Bass Drivers around 1000 watt RMS with 4" voice coils.
Reality Check Here
The JBL speakers you have are quoted as 98db for 1 watt
The JBL spec sheet says that they can peak at 128dB - That 30db increase is 1000W. Add in a 3db power increase to compensate for thermal compression and were up to 2000W to reach that volume
The 1850 horn is 105db for 1 watt add in 30db for 1000W subtract 3db for compression and we are already at 132db. The 1850 horn is a good cabinet but really works best groups of 4 or more
There is no way your current speakers can keep up!
If you choose a less ambitious design for the bass bins you can still achieve enough SPL to match your mid tops, but with a lot smaller cabinet, or one that trades some efficiency for more bass extension
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Old 13th March 2013, 10:26 PM   #22
more10 is offline more10  Sweden
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How about this for tapped horns---over 2 full octaves
I would like to see group delay as well. Impulse response is also interesting.
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Old 13th March 2013, 10:39 PM   #23
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Originally Posted by weltersys View Post
Thanks.

WRT the first link, I don't think you mentioned a problem with tapped horn measurements vs simulations, so I don't think I need to read that whole thing right now. (I've read quite a bit of it in the past, and I'll revisit it again as time allows, but I don't think it's got much to do with this conversation.)

WRT the second link, I took a quick look but didn't see a hornresp sim anywhere so there's nothing to compare.


Quote:
I'd like to see your sims and measured results.

Art
Sure, but I don't have anything to show that's going to convince you of anything. I lost most of my measurements and sims when my old computer died unexpectedly, so all I have left is really old stuff that I posted online in various places when I was still learning.

In addition, most of my sims were done in hornresp and refined in akabak and I don't have any of my old akabak records. Also, most of my measurements are not documented. (Some were done outside at 10m, some were done in my driveway right beside the house, some were done in the middle of a room at 1ft, some were done in room with the mic inside the horn mouth and most of them are not marked.)

So I can show you a bunch of sims and measurements that may or may not show anything useful or you can take my word (or not) that I noticed a strong correlation between response curves in sims and measurements. Especially down near tuning.

Here's an example. This is a hornresp sim.

Click the image to open in full size.

I imported that into Akabak and continued the design, trading a higher tuning for more peak spl but ultimately keeping the same response shape. Unfortunately I don't have the final Akabak sim.

Here's a measurement. The top (green) line is the one to look at. But I think this was done in room (in the middle of a room) about a foot from the mouth. I don't have any of the measurements that I took outside anymore, but the curve shape was the same. (I could prove that by showing the measurement of the other horn in the pic as measured outside but there's no point in trying to qualify these measurements.) The dip at 90 hz was unexpected and likely due to a problem with the fold.

Click the image to open in full size.

Here's another one, I think the mic was right in the horn mouth this time.

Click the image to open in full size.

Anyway, all the resonances are right where they are supposed to be, the measurement matches the Akabak sim (that I don't have anymore). Unfortunately I can't resimulate this with Hornresp since I made changes that Hornresp can't simulate due to lack of segments and I can't remeasure it since I don't have the horn anymore.

So as I said, I've seen a strong correlation between the sims and measurements but I don't have anything to show that will convince you of anything. I lost all my more accurate sims and most of the outside measurements.

Last edited by just a guy; 13th March 2013 at 10:46 PM.
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Old 13th March 2013, 10:49 PM   #24
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by more10 View Post
I would like to see group delay as well. Impulse response is also interesting.
Agree, Without a Phase response(Not minimum phase as it's pointless) or an impulse response any shown TH FR + a minimum phase plot is IMO a 'clever' 'floobydust' thrown at those who just want to be impressed with eye-candy.

b
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Old 13th March 2013, 11:12 PM   #25
more10 is offline more10  Sweden
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Lots of OT stuff in previous posts.

Canīt we just cooperate and help Steve? Answer his questions that is and give advice on request?

This is what we know
1) He will be playing dubstep outdoors for 500 people. Lower frequency is 20-25 Hz.
2) Top section is JBL JRX 115. These will go down to 100 Hz. Probably not adequate in terms of output for outdoors 500 people, but Steve did not ask advice on these. If the subs outmatch the tops maybe he will trust us with advice for new top section next season :-)
3) Steve wants to go for front loaded horn. Probably because I stated that they sound better because of better impuls response. Anyone challenging this?

This is what we donīt know
a) Budget
b) Transportation capability and people helping setting up the equipment.
c) Carpenting skills

This is what I assume
I) Budget is limited, otherwise Steve would just have bought the stuff and not asked here
II) Size of the system is not of big importance since it is outdoors.
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Old 13th March 2013, 11:48 PM   #26
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Originally Posted by more10 View Post
Lots of OT stuff in previous posts.
When you state something as fact and people disagree, that's not OT. The conversation that results is also not OT but I agree it doesn't help the OP. In conversations like these, a lot of generalizations and sometimes misinformation is passed off as fact, like the tapped horn 1.5 octave bandwidth statement. Even the statement about the required horn length to achieve a given tuning is a generalization since it depends so heavily on the flare geometry.

Quote:
Canīt we just cooperate and help Steve? Answer his questions that is and give advice on request?
Sure.

There's not many horns of any type that can hit 20 hz with the required high pass filter in place. There's Gjallerhorn and F20 cinema horn and maybe a couple others at avsforum. Then there's Danley products like DTS 10 and similar. All of these will need multiple cabs to be loud enough. And none of them will be flat down to 20 without eq when used outside without boundary support.

Or he can design his own, or request a design, but that's a lot of work.

Quote:
3) Steve wants to go for front loaded horn. Probably because I stated that they sound better because of better impuls response. Anyone challenging this?
I've heard tapped horns that sound better than front loaded horns and vice versa. It depends on a lot more than just impulse response. Different materials (and thickness of materials) will sound different, different response shapes will sound different, every choice you make has the potential to introduce audible differences. There'a also personal preference - some people prefer the high distortion of ported boxes, some prefer the lower distortion of horns for example. Sweeping generalizations may or may not turn out to be true and "better" is a judgement call. The only way to decide which design will sound best is to listen to them. (Unless one of them has a clear and blatant defect in design.)

Last edited by just a guy; 14th March 2013 at 12:06 AM.
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Old 14th March 2013, 03:18 PM   #27
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Im not going to lie there is a lot of information there i am struggling to understand...

Thank you for all your help so far though!

Yes i will be upgrading my mid/tops this summer, but i'd like to get some bass bins first! i will probably build mid/tops at some point.

So its a switch between tapped and front loaded folded horn.

Can someone please in less technical terms (though i am not a complete n00b) explain to me the benefits and disadvantages of both. PLEASE!

Im building for the future! I would like the bass to be filling! but at the same time accurate.

to put it in my terms, i would choose a ported sub over an enclosed sub!

Thank you people
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Old 14th March 2013, 04:34 PM   #28
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You are asking the wrong questions. You need to define your goals before you start picking designs. You still have not defined how loud the system needs to be (spl at furthest distance of interest), how low it needs to play, and probably most important, a budget. You also need to decide how large you want the entire system to be, and how large each cab can be.

You haven't defined any goals and yet you've already disqualified simple ported boxes.

Ported boxes are the best bang for the buck as far as size vs spl. If portability is important and you don't want to move a stack of subs the size of a garden shed (or potentially much larger), ported might be the best way to go. If you are not so worried about size and instead want to use less power then horns might be the way to go.

So the first thing I would do is figure out how loud you want it to be at the BACK of the audience. Are there any solid boundaries you can use to reinforce the output or is it a wide open field?

Next, use a program like Audessey to figure out how low your music actually goes. If it actually does go down to 20 hz you need to determine if it's important for you to actually reproduce that.

Are you expecting to be able to move this system in a car? Or do you have a bunch of vans or a moving truck?

How much power do you have? What kind of amps? Is there somewhere to plug this in or are you using generators?

The pros and cons of front loaded vs tapped horns is a question you should be asking near the end of this process, not at the beginning.

The system needs to be designed as a whole, you can't just pick a random design that looks good and keep adding more and more cabs until it's loud enough, especially if you need it to be tuned very very low. At some point the stack is going to get large enough to cause big problems with dispersion patterns unless you split it up into separate stacks, but that will not take full advantage of mutual coupling.

If you want to do it right the first time you need to start by clearing stating your goals.
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Old 14th March 2013, 04:45 PM   #29
more10 is offline more10  Sweden
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I totally agree!
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Old 14th March 2013, 06:32 PM   #30
OscarS is offline OscarS  United States
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Originally Posted by just a guy View Post
And Danley regularly gets a full 3 octaves out of the low tuned tapped horns. It's bumpy but it's a full 3 octaves.
That's beyond me, lol.

Quote:
Originally Posted by more10 View Post
I would like to see group delay as well. Impulse response is also interesting.

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