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!

[hoopsontoast]

Steve, sorry to bump an old thread, would a very low Qts driver work in a similar Tapped Horn?

I’ve a spare custom ATC PA75-314 12" driver from my Castle Subwoofer, with a low 28Hz fs but a very low Qts of 0.18 which makes it difficult to get any bass out of it without a horn enclosure.

[SteadySteve]

Since this thread and before it got used in anger at the wedding I swapped the driver to an Eminence Definimax 4012HO.

It measured better and made a bit more noise👍

I then put the Lab12 driver in a smaller boom box. The two together made plenty of 30 to 60Hz bass in a very large Marquee.

I’ll a look at the T&S of the Definimax and compare with your driver.

[SteadySteve]

Just looking at the T&S, it is a really low Qts!
That suggests a strong motor but the BL (motor strength) is 12.6.
The Lab12 has BL 15 the Delfinimax 19.6.

You need a good motor power and cone strength in a Tapped horn I think.
If you are going to gig them then the cone needs to be strong enough not to have the coil punched through it when trying to quickly move that stiff column of air it’s driving.
Also the super low FS of say the Lab12 doesn’t seem to be needed. It works better in boom boxes!
So, its a bit confusing.

If you are near enough you’d be welcome to bring it over and we could load it into the TH and measure it. Assumes the bolt pattern is standard / like Eminence.

I’m sure it will work - esp for hifi / AV use where you are not going anywhere near maxing out.
Also helps if you are DSP’ing and can EQ a little bit.

[hoopsontoast]

Thanks Steve, this would be for just Music, at home (5m x 4.5m room) so I think just the one would be enough.

I’ve been reading up on MEH builds such as yours and other on DIYAudio as I already have some drivers that might be suitable. Just trying to work out if I can actually achieve the woodworking required with just my track saw and limited skills!

[AmDismal]

@hoopsontoast

with just my track saw

Dude, you’re doing it wrong. Each new project is a reason to buy a new tool.

[SteadySteve]

Yeah I’d go for it.
Worse case is get yourself a Delfinimax afterwards.
I got my one from Lean Audio.
It was new but in the sale, so only cost £100.

Track / circular saw, expanding urethane wood glue and filler are all your friends.

Getting the throats done nicely takes time but filler and careful sanding gets you there.
Everyone wants to print everything these because it’s the new kid on the block..

If you just want a pair and don’t have use for a large enough 3d printer to do good stuff, handmade is perfectly doable.

I also got the Celestion 5" sealed back drivers from Lean.

The Eminence Kappa 12As I had proved very suitable for HiFi use in the SH MEHs.
I’m sure others would be fine too.

[hoopsontoast]

Yeah, I was reading through the one below, using just a single bass driver (my case could be the 10" Volt BM2500.4 I have) and then my BMS 4524 as tweeters with the two Celestion Mids as you suggest. Mine would not be in corners but ideally up against the rear walls.

Massive MEH Home Theater Build

I’ll continue to do some more research, I already have the 18mm plywood I bought earlier in the year.

This one seems to be pretty much what I am thinking:

Synergy build with TF0410MR mids

[SteadySteve]

Sounds like a plan.

I really like the 60° profile.
Would certainly work on the 4.5m width and probably the 5m too.

Several over the years commented about 50° being to narrow for wider large rooms.
I’d second that.

If you are going tapped horn, then you really want to get the LF of the MEH down to somewhere where the tapped horn thrives.

Mine do work up to 100Hz but the MEHs are much better at the 60 to 100Hz than the Tapped horns.

To get down to 60Hz odd you’ll need the rear enclosure and LF ports.

Not utilising the horn AND reflex loading of the SH format is limiting I feel.

If you use another type of sub that can play higher, unless sealed and huge to get 30Hz, it may be ponderous.

I really don’t get the comments made about taps and ports being a big disrupter.

I measured with the MF taps taped over and around on axis there was virtually no difference.
That was with the 4 LF taps and ports open of course.
All my measurements have been.
I certainly don’t hear a problem!

The SH60s continue to absolutely amaze me. So non-fatiguing and yet interesting yet dynamic.