Comments on system plan

Question: Having two hornloaded bass units running at the same power results in an output increased by 6dB (assuming they are operating within the coupling distance of ¼ wavelength, above which you’d get directivity) like a direct radiating system right?

If so, subtracting a generous 6dB for power compression a single stack of the proposed system (assuming 105dB sensitivity) should be capable of peaks of 140dB@1m when powered by 1kW per cab (4 cabs, acoustic output referenced to 1m rather) in the bass (ignoring the tops for now) calculated back to 50m I end up with peaks of 106dB per stack. Add 3dB from the other stack (non-coherent addition) and one ends up with 109dB peaks at 50m from the stacks after accounting for compression.

Now how loud does one need to have the sound at the rear of the concert? Allowing 20dB for headroom and crest factor in the music and by the above I get 90dB average levels at the back (50m) (and a shed load more up front). Surely this should be sufficient for a rock concert with 1000 people?

Does anyone have a good link or a recommendation for a book on the topic? Been thinking of buying the Yamha “Bible” on Sound Reinforcement, is it any good?

Regards

Martin

Yes and no.

This forum has taught me that there is nothing like real practical experience to back up the theory, hence the questions. My mate who does freelance mixing, says that a fair bit of the South African industry seems to work on a rule of 2W per person (I'll have to make that acoustic watts for the free party people, seen some pics of stacks in the middle of the English countryside, beautiful, in a mad scientist 140dB+ way)

It's just the comment that such a system would be sufficient for 200-400 people earlier on in the thread made me a little quezy, as it is supposed to be useable for music festivals with 1000 or even double the amount of people in attendance eventually. Whilst this is not what I expect to do at first, the capability of the system to scale is what I need and the 40 degree horizontal dispersion of the porn horns is exactly what I need.

Martin

Timber_MG wrote: It's just the comment that such a system would be sufficient for 200-400 people earlier on in the thread made me a little quezy, as it is supposed to be useable for music festivals with 1000 or even double the amount of people in attendance eventually.

hi
the 2-400 estimate was probably more along the lines of the 140+db stacks in the english countryside you mentioned.
at something like that you often see about 100 people, sometimes even fewer, dancing to a couple of those stacks.....
with two (i thought you were only building one stack, i misread) i reckon you would be able to cover quite a lot more than that estimate, at least in a more concert-like setting. still i think 1-2000 is pushing it a bit, and you might well want 3 stacks, with one split and used as rear delay stacks.
even that seems a bit small, but like i say, i like my music very, very loud ;)

Ok. My Tannoy 15s I use at home come to about the same limit at 2 meters as the above described level at 50m and for me that is sufficient, even for a rock concert (used indoors though). Also those at the back might not want to have long term hearing damage inflicted on them like those at 3m so I recon for a throw of 40-50m such a system should be sufficient. Would the Tops (2x double 12"/1.4" per side) be able to cope in this situation or would that have to be increased due to the increased HF energy in rock?

Thanks for the advice

Martin