The Horn of Mass Destruction

[mgoedeke]

The Horn of Mass Destruction

This thread serves to document my progress on a Horn to be installed at Sony Music, London. Their current system consists of a pair of JBL DMS-1 sofit mounted, digital controller and 1.2 kW worth of amplification. But the execs like their tinnitus loud and they asked for something more.

So here goes: simulation of the room shows that the 12dB/oct room gain starts just above 20 Hz and the two dominating room modes of interrest for LF extention are at ~30 Hz and ~16 Hz, perfect for some horn action. (Horn terminates flush into the middle bottom of the front wall underneath their projector screen)

Drivers: 4x JBL SUB1500

Sd = 830 cm^2
Fs = 21Hz
Bl = 20
Re=2.9
Qts=0.3
Qes=0.32
Qms=6.7
Vas=181 l
Xmax = 18mm
Xdamage = 25.4mm
Low distortion driver with copper shorting rings

Amplification: VOID Acoustics Network4

1,8 kW into 4 ohms both channels driven
5 band Parametric eq and limiters

Horn:

18 Hz Hyperbolic T=0.45
St = 1480
Sm = 16,000 cm^2
Vb = 270l
Shortened to 440cm

I will post pictures and other info as I go along. Project deadline is end of April.


Martin Goedeke

[Tim Moorman]

Martin,

I really can't imagine such output. A true bone crusher!

The bass horn I built from a John Sheerin design can run everyone out of the house with just a pair of 10". This will approach structural damage levels. Frankly, with what, 103 - 105 db/w/m(?), I can't see that they will ever use more than a fraction of the amplifier output. Not and stay in the same room.

As I'm sure you are aware, the large drivers are physically hard mount in a compact cluster and fire into a small terminus. How will you array the drivers? Poles of a compass? Dual slots with a pair of drivers for each?

You are allowing access to everything, right?

What are they using above the horn for mid/hi?

Very interested in your progress. Keep those posts coming.

Good Luck.

Tim

[mgoedeke]

I will post more details as I get to be able to, hopefully including the results of the sims and how that compares to the measurements in due time.

I know the system is extreme, but they wanted something impressive and accepted our bid for the system so I am not complaining.

The DMS-1 is an MTM using 1401Nd 14” bass-mids from about (curerntl) 30Hz to 1k and the tweeter is a JBL 2450SL-A 1,5” compression driver in a 90x40 CD horn (2332). Distortion is extremely low, but they blow even such a system quite regularly and regularly exceed legal levels in a large room (11,1 x 8,6 m). They were given the option of a conventional sub, but decided for the horn.

Modeling the horn will show a peaky response, but this is intentional because of the room mode at 30 in the back of the room where the board sits (if the sims are to be believed). And if they are wrong, well that’s what eq. is there for…..plenty of headroom for such trickery. I am not quite sure how low it will go (probably related to how “leaky” the room is) but it wouldn’t surprise me to see 120 dB from as low as 10 Hz.

Any hints as to stuff to play to show off such a system?

[markp]

Pass out diapers to hold the result of 120db at 10Hz! Your bowels will let go!

[mikee12345]

you are so lucky



use a measurement system after to see what the response is including the room,mlssa clio etc.

[Magnetar]

3 horn loaded 18's, four horn loaded 15's, two horn loaded 10's, compression drivers, and slots.

And it's real and in my room -- not even simulated..

[GM]

>Any hints as to stuff to play to show off such a system?
====
http://www.smr-home-theatre.org/Sub-...How-Low-2.html

GM

[phase_accurate]

Any hints as to stuff to play to show off such a system?

Maybe a starting space-shuttle or a stomping and belching T-Rex ?

Regards

Charles

[Tim Moorman]

Martin,
With the bass improvement underway, I would try to get them used to the idea of horn loading the midbass, too. I always hear the transition from horn to direct radiators. Not necessarily really bad or anthing, just different sounding, dispersion issues aside here.

The systems with the cleanest transients, kick drum and the like, were horn loaded in the midbass too, like Magnetar's. While the fundamental may be on the high end of the subwoofer's bandwidth, the harmonics carry through the crossover into the midbass. Critical to get that part right too, wrt phase, etc., but the epitome of speed/attack without overhang.

As far as a test CD, I use Me'Shell Ndegeocello's "Peace Beyond Passion" for midbass/bass. She's a bass player, so decent extension but nothing much below 30 Hz. Lots of great grooves though, and more than usual amount of decent low end. The recording is well made and good sounding.
There is a test CD out with the actual launch of a NASA shuttle which is scary loud (no compression/limiting on the recording) on the right system. Sheffield Drum CD for transient behavior.


Magnetar,
I saw the system over at AA, HE forum. Posted you a note. Looks terrific. Wished I hadn't missed the chance to hear it.
That is one impressive effort. Must sound simply amazin'.

I'm working on a set of midbass horns with 2226's to use above the sub horn, hoping to get enough bandwidth to use with my 2440s or the Community M200s. Still have the TAD 2001 for highs out to maybe 15 -16K. I considered the 2405s, but no exposure to them.

Anyway, the fully horn loaded system looks really good and should be supremely capable.

Tim

[mikee12345]

Your in luck,just yesterday i was on the HT forum and saw a HUGE thread on which has the lowest bass. A guy was using the spectrometer on SOUND FORGe to good effect

Its mainly DVDs that have the lows.music less often

Just get a behringer sub bass pro, synthesises bass 1 or 2 octaves lower


-il find that thread again.