jbell's set of four tapped horns

[littlemike]

And a response plot at the 50 yard line!

[Samuel Jayaraj]

jbell, how do they sound with the cabs standing upright, stacked beside one another and the horn mouth firing on to the floor?

I have a pair of 3015LF drivers and a pair of Lab12 drivers. I plan to start next week with Wayne Parham's 12Pi design using Lab12 drivers. I'll probably make about 6 cabs.

I want to use 3015LFs in a TH and plan to make 6 of these as well. However, I have not yet found a fold which is portable for PA duty.

Could someone please help with a portable fold for the 3015LFs going down to about 35 Hz?

If nothing else comes up then using the same fold and dimensions as yours would be good. Could someone in the know draw out a rough sketch with dimensions and angles, scan the image and post it here. I am sure it will be of help to many.

Thanks,

[littlemike]

Jim has posted everything you need above - it is literally a connect-the-dots type build. All dimensions are in inches, the hornresp parameters are in centimeters.

From jbell's post:

For anyone who wants to replicate this (not sure if anyone does) It's 46x36x25.5 wide. (because I used 3/4" 7ply arauco)

Points of interest in plan layout: 1st point is 10.75 down from top, 8.5 from front. 2nd point is 12.25 from top, 14.25 from back 3rd point is 18.5 from bottom, 16.25 from back.

Those are the horn fold (toward outside) measurements.

The front panel is 25.25 long, and the throat is exactly 4".

From that and the pic above showing the fold, you can get to everything needed.

Hornresp params are 600cm throat, 3000mouth, 16.9,235,16.9

Point 1 is at the left side of the picture of the open horn, point 2 is in the middle, and point 3 is at the right. These three are the only points required for layout, the rest is connect the dots.

Good luck with your builds.

edit: clarification of units and measurements

[HK26147]

Jim - Will you be able to take them to "The Shootout" before you have to install them?
A whole lot of people want to see those numbers.

[Samuel Jayaraj]

Originally posted by Samuel Jayaraj
I want to use 3015LFs in a TH and plan to make 6 of these as well. However, I have not yet found a fold which is portable for PA duty.

Could someone please help with a portable fold for the 3015LFs going down to about 35 Hz?

Thanks,

Thanks a lot for the pointers to jbell's TH layout.

So should I give up on pursuing a more portable fold with a cut off at around 35 Hz or a little higher?

[littlemike]

The 3015 LF is one of the more popular drivers for TH's used for PA. There are several other designs for this driver in the "collaborative" thread, as well as a number of different folding topologies discussed. If you expand your search beyond the diyaudio site, there are a number of other pertinent discussions and designs that are well-documented on the web.

Jim's design plays to 40 Hz with authority (102 dB 1W 1M 2pi). It is -5dB @ 35 and -12dB @ 30 Hz. It uses an efficient folding pattern (no wasted internal space), and is already too big for your use. Physics and basic horn theory tell us that a 35 Hz horn will (with all else being equal) be even larger, regardless of the folding pattern used.

Taking the 3015 LF driver, placing it into a lower-playing tapped horn, then designing that tapped horn with a smaller mouth will cost you efficiency through the passband as well as increase the driver's excursion. It can be done, and may even yield a flatter response, but you will most likely not get the same SPL capability and you will reach driver excursion limits sooner. Jim's design was chosen based on maximum output within a given passband and a given amount of space for the installation.

In fact - a TH for the 3015 that is -0 dB @ 35 Hz is also 5 dB less efficient than Jim's through the passband, but requires essentially the same cabinet size. Additionally, 1W excursion increases approximately 20% due to the lower frequency. There is no free lunch.

If the 3015 is too big, consider the 4012HO. It also performs very well in a tapped horn, will reach the frequencies you want, and requires a cabinet that is approximately 1/2 the size. The efficiency is similar for the two drivers in a cabinet capable of an honest 35 Hz.

Once the driver is chosen, there are only four variables in the simplest form of a TH (which Jim's is L12=L34, conic flare). Area at the throat, area at the mouth, length, and location of the tap.

Jim's folding technique?

Simple, but brilliant.

Draw up a scale model of the horn's taper, cut it into sections, and slide them around on the paper to see how it all fits together. (Sorry about letting your super-duper top secret folding technique out into the wild Jim....)

Lots and lots of options out there. There are lots of examples, and lots and lots of screenshots. Learn to use hornresp. It is not hard to figure out.

We'll show you the trail, tell you about our trips, share our maps, provide assistance and encouragement where we can, but we're not gonna climb your mountain for you.

Design, build, test, evaluate, redesign.....

[jbell]

No shootout for this set of subs, other than halftime....
Hopefully they will be in place and running within the week. Football season is almost here...

[Samuel Jayaraj]

Originally posted by littlemike
The 3015 LF is one of the more popular drivers for TH's used for PA. There are several other designs for this driver in the "collaborative" thread, as well as a number of different folding topologies discussed. If you expand your search beyond the diyaudio site, there are a number of other pertinent discussions and designs that are well-documented on the web.

In fact - a TH for the 3015 that is -0 dB @ 35 Hz is also 5 dB less efficient than Jim's through the passband, but requires essentially the same cabinet size. Additionally, 1W excursion increases approximately 20% due to the lower frequency. There is no free lunch.

If the 3015 is too big, consider the 4012HO. It also performs very well in a tapped horn, will reach the frequencies you want, and requires a cabinet that is approximately 1/2 the size. The efficiency is similar for the two drivers in a cabinet capable of an honest 35 Hz.

Lots and lots of options out there. There are lots of examples, and lots and lots of screenshots. Learn to use hornresp. It is not hard to figure out.

We'll show you the trail, tell you about our trips, share our maps, provide assistance and encouragement where we can, but we're not gonna climb your mountain for you.

Design, build, test, evaluate, redesign.....

Thanks for the instructive reply. I will learn to use hornresp. Jim's TH is a must do, well almost; what with 2 drivers waiting for a cab.

However, the comments about the 4012HO is very interesting. I will search here and beyond this forum. Any pointers?

Thanks once again,

[ttako]

Originally posted by jbell
you were talking behind my back...

However, I did achieve 114db/10m/20v/40hz.

I was impressed.

and yes, the cabinets have to be like the pic above in the install, and bass steering does work.

more later

Hi Jbell,

I guess in that case, that all cabinets are getting 100W, meaning 400W alltogether at 10m are giving the 114dB SPL?

Also the drivers are 4 ohm drivers, right?

Thanks for clarifying this...

Tamas Tako

[jbell]

nope, 3015lf is 8 ohm.. approx 50 watts per cabinet.

my lock fell apart on my garage door about 5 meters back @20v, so I didn't push it on up to 28.3 volts, which is what I should have done, to get a real 1M/1W reading. (10M/100w = 1M/1W)