30Hz Tapped Horn Sub project

[SteadySteve]

A square TH sub on the go.
Will do 30Hz, little lower minus a few dB.
Will use the venerable Eminence Lab12 sub woofer.

First side gluing up.
Using Evostick expanding urethane glue.
Also be sealing the wood.

I’m building it to pair with the Danley SH50 style cabs I build and am loving.

Won’t be in the music / cinema room (the two tapped horns are there still), but on a little jaunt in September.

To provide the lowest octave 60Hz to 30Hz.

I would have liked 2, but 2 will not fit in the car.
Corner loaded so should be adequate.

Will be powered by my Cerwin Vega 1800 in Bridged Mode.

[murrayjohnson]

What are the cabinet dimensions going to be? hxwxd

[crimsondonkey]

[SteadySteve]

38" x 30" x 15.25"

The 20Hz at 60" x 30" was too big.

[SteadySteve]

Bit of progress.

Sides on and internals test placed in.

Driver baffle / mount done.
Will be sealed and bitumen sheeted.

Bolts and T nuts

Xmax catered for

The wee beasty

[SteadySteve]

Realised I didn’t put the Hornresp modelling data up - here it is

Parameters

How they are measured out for Hornresp

Schematic (how it looks straightened out - 30Hz or anything below 100Hz doesn’t see the folds acoustically)

The all important SPL.
This is a 2.83V / 1 watt.

The first peak will be flattered by a DSP PEQ, above 60Hz I’ll have a 4th order L-R slope killing everything off nicely.

I’ll also have a 4th order killing of anything below 20Hz to protect the driver.

The driver diaphragm displacement.

When the SPL is flattened it’ll give around 107dB/W and 29Hz flat.

Wonder how many Watts I’ll be chucking in to pressure the hall?
Have upto 800W peak, 400W music on the driver before it melts😂
But I don’t think / hope🤞 we won’t go anywhere near that!
It will be going right in a corner.

The CV amp can give 1800W in mono bridged mode. No bottleneck there!
It will be suitable throttled back by it’s built in control.

[SteadySteve]

Today was test day.

Long post and will set off TLDR; unless this is your sort of thing🙂

Here’s the driver mounted

Workshop dimensions are 7m X 7m.
Should give a room mode or two…

Then got my 2nd Najda and the spare Behringer Inuke amp down from the loft.

Wired up.
Bridge mode for the Inuke.
Fiddled with the settings…
This not only gives more peak power than the driver can handle in theory, but also puts stereo to mono.

The inputs are the same L+R from Najda DSP dac, but a 4 pole Neutrik Speakon plug is wired plus lead to 1+ on the plug, as usual, but instead of minus lead to 1- it goes to 2+ (the 2nd pole as it were).
Clever - hard to mess up.

Then plug in mic / phantom amp to laptop. Ditto WaveIO USB to laptop coax RCA to Najda.

Then fire up REW to measure.

Using the current Najda set up file for my system, modifying to suit the Lab12 tapped horn sub.

Remove the odd PEQ I use in the music loft with the 2 X 4.2m long 20Hz Tapped horns.
X/O setting the same 60Hz low pass.

Adjust the gain… measure, lots of this🙂

Add some PEQs (just as Hornresp showed I would require / predicted).

Measurements

Normal volume 1/3 smoothing

1/6 smoothing

Giving it more power!

Then I had a listen to just the rumbling bass.
I have a bass test playlist.

Here’s Dark But Just A Game - Lana Del Ray, known for gob of 30Hz;
quick measurement, at -30dB on Najda and a long way from the sub.
Hence well form on dB.

Sounded suitably deep and rumbly😂

Some tracks registered at 28Hz and even 26Hz on some tracks.

Might play with steeper Low Pass XO. 6th or 8th order.

The 2nd hand Lab 12 driver seems fine after a long test.

Pleased with this…

Paint it black (Tuff cab PA gear paint next).

[SteadySteve]

Tapped horn sub all but done.

I’m making a grille insert for it just to keep any unwanteds out.
Cat for one

[murrayjohnson]

Need to be careful leaving it out like that. Before you know it, it’ll be playing Thus spake Zarathustra and be surrounded by chimpanzees wielding femurs.

[SteadySteve]

Listen to The Gage Lanza Tapdance Extravaganza by Thus Spoke Zarathustra on Qobuz Open Qobuz

My favorite!