VOTT Inquiry

[LICORNE]

Hi Mark,

You should consider dual HF drivers with your 1505 horns (15 cell). GPA could do this for you
and bring those drivers to 299A standard 8 ohms series connected in series.

THe other alternative is to add 3 more 210 cabinets. This is getting a bit costly.

What is the distance from screen to back wall of the theatre seats?This is a huge place! what is your screen ratio? and dimensions?

I presume this is 5.1 system.

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[LICORNE]

Hi Gm,

How about retrofitting his 288C into 299A 16ohms
by GPA. I think that we need a little more power
here. 50 watts Horn are the norm for todays films.

It would be less expensive and we could probably reach the back wall of the balcony .

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[LICORNE]

Hello GM,

I agree with you entilery. The extra horn for vertical dispersion will help greatly.

The need for 50 watt drivers is to avoid clipping.
Not to increase SPL

The wiring (paralell etc) I think he knows all about that,Mark is a sound Engineer.

Their system could also be SDS Dolby?

We need more info on theatre measurement to determine best possible solution.

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[LICORNE]

Here is some guide lines according to Altec back in 1945.Probably for monophonic reproduction.

http://www.voiceofthetheatre.com/ima...catt1945.8.jpg


http://www.voiceofthetheatre.com/ima...att1945.14.jpg


http://www.voiceofthetheatre.com/ima...att1945.15.jpg


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[martyh45]

Hi,
RCA used a 60 degree radial for balcony coverage on top of a 90 degree radial for main floor coverage. Would using an 805 on top help to punch the sound all the way back or is that a technique that works best for radials? Picturing the dispersion patterns in my head, it seems that 80 degrees would be sufficient to get good coverage of the balcony seats in any of the oldies but goodies I have been in. While I am dreaming of how cool it could possibly be, wouldn?t it be neat to build some monster horns for the 515s? Mark has digital delay and plenty of room at his disposal so some 36 square foot big boys would be doable. Too bad I don?t live in Seattle, I would donate the time to help build them just to hear what they could do.
Marty

[GM]

Yes but his 288c's measure 16 ohms. He would have to change the 288c's for 8 ohms to stay in match
with Crossover net.

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

Not really, wire 16 ohm units in parallel and add a 16 ohm series resistor. This will also make them sound more like Altec voiced them originally with impedance matching amps. This flattens the horn's response so the apparent 3 dB acoustic power loss isn't nearly as bad as it implies since it just means the horns need less shelving. This requires some form of EQ to 'lift up' the highs, especially when firing through the screen at DD/DTS/THX reference.

Regardless, filling the balcony is more about increased vertical dispersion than sheer SPL, hence by suggestion and why I believe a second driver on the 1505 isn't the answer. That said, with more facts available, a 1005 on top should suffice. This will allow the 1505 to be angled down more if need be to improve the main floor's coverage.

Ideally of course, a complete measurement of the theater is best so that CD horns better suited to the task can be implemented.

GM

[GM]

Originally posted by CONVERGENCE:
Hello GM,

I agree with you entilery. The extra horn for vertical dispersion will help greatly.

The need for 50 watt drivers is to avoid clipping.
Not to increase SPL

The wiring (paralell etc) I think he knows all about that,Mark is a sound Engineer.

Their system could also be SDS Dolby?

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

?? Since he's using a single 210 less wings, assuming the system isn't EQ'd excessively 'hot', the only way any amp's going to clip is if it has too low a power rating.

My wiring explanation was for your (or anyone else's) benefit as to why I think swapping VC's is money better spent elsewhere.

So he says.

What is SDS Dolby? There's Sony's SDDS and Dolby's Digital format, but I couldn't find any SDS on Dolby's site. Anyway, he says he uses a Dolby processor.

GM

[LICORNE]

Hi,

I apoligize ,I ment SRD DOLBY DIGITAL.

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[GM]

Greets!

The RCA units I'm familiar with didn't go as high as the W.E./JBL/Altecs, so maintaining dispersion up high wasn't as critical. Anyway, any horn that has two different dispersion patterns is a radial, with the multi-cells maintaining it over a wider BW than the RCAs I experimented with in the '60s.

The 805 probably would have too narrow a dispersion for a large balcony, which I assume this one is based on the number of seats.

WRT to angle, it depends on the main floor and balcony seat distribution as well as screen height and how high off the floor it is and why so many different multi-cells were offered for mono systems.

Multi-channel sound OTOH requires a narrower horizontal polar pattern than mono. Here, the radial CD is much preferred over the traditional multi-cell and to a lesser extent the radials with the small HF multi-cell at the horn's throat.

Monster horns are cool, but in multi-channel sound the mains are typically brickwall high passed at 120 Hz, so the 210s suffice, and anyway they only drag this stuff out of storage twice a year, so a permanently installed true full range system probably isn't a viable option.

I forget who/where, but awhile back I read about a huge basshorn being built into the stage of an old theater with the mouth spanning the entire stage front. Bet that one flaps some pants/skirts!

GM

[jnorv]

Hi, What is the name of your theater? I have friends in Seattle and occtionally go there on a vist. Would like to hear your system in operation.

Jim N
San Jose