Morning Gentlemen- I come from the world of Mobile Audio and have been asked by our church leader to look into replacing some aging equipment. The enclosures are stand alone PAS TOC MF-218s. Four single 8ohm drivers, two per cab being ran on a pair of QSC RMX1850s each running bridged @4ohm.
The OEM enclosure looks to be around 10cuft and tuned very high with triangle ports tucked into the four corners. I can't find T/S numbers on the subs themselves but looking at very similar drivers I intend to throw them(2) in a 12cuft box fitted to the back wall w/180sqin of port @37hz
Now, coming from the car world this seems like an awesome music set up that will up the energy in that space. My concern- is that these PA drivers are very light and responsive compared to my heavy power hungry drivers that I used to compete. Should I make any drastic adjustments to the design to facilitate the lighter moving mass and less power requirements?
Pics
https://i.imgur.com/2WoW54I.png
https://i.imgur.com/J3PvZMf.png
The OEM enclosure looks to be around 10cuft and tuned very high with triangle ports tucked into the four corners. I can't find T/S numbers on the subs themselves but looking at very similar drivers I intend to throw them(2) in a 12cuft box fitted to the back wall w/180sqin of port @37hz
Now, coming from the car world this seems like an awesome music set up that will up the energy in that space. My concern- is that these PA drivers are very light and responsive compared to my heavy power hungry drivers that I used to compete. Should I make any drastic adjustments to the design to facilitate the lighter moving mass and less power requirements?
Pics
https://i.imgur.com/2WoW54I.png
https://i.imgur.com/J3PvZMf.png
Simply throwing the same drivers into a different (but fairly similar) box isn't going to improve much.
You really need the T/S parameters of the woofers in question. Measuring them is not difficult.
However, I'd suggest that a single modern high-power 18" in a tapped horn would eat 4x older 18"s for sheet output.
Chris
You really need the T/S parameters of the woofers in question. Measuring them is not difficult.
However, I'd suggest that a single modern high-power 18" in a tapped horn would eat 4x older 18"s for sheet output.
Chris
Agree w/chris661 that the improvement would be disappointing, especially considering the time/effort/expense you'll put into building those cabinets. The proposed design is clever, beautiful and well suited to the venue, but you'll be replacing the only part of the existing system that is NOT suffering wear and tear.
Doubtless some people do, and probably successfully, but I personally would not run the QSCs bridged driving 4 ohms. It's a big challenge for any amp and IMHO not worth the risk. If you've been anywhere near using that 3-1/2 kilowatts, those woofers are surely well-worn and a reasonable replacement target for that reason alone.
Also, a couple additional facts would help us give better advice: What is the crossover frequency of the existing installation? And, what program material?
What you described sounds more like 'woofers' than 'sub-woofers' - crossed over at 500, 800 or even 1200 Hz. That knocks a few design options out of consideration if the replacements have to work that high.
A couple/3 microphones to produce speech is an entirely different challenge than a combo w/keyboards-bass-guitar-drums and vocals, or even bulk-mike-ing a large choir.
And keep in mind, churches are notoriously under-damped, w/the only absorption often being the patrons. Furthermore, the bottom two octaves are usually treated to less absorption than the rest of the spectrum. 3-1/2 kilowatts driving high-efficiency cabinets could swamp the whole space anytime that it isn't packed.
Cheers,
Rick
Doubtless some people do, and probably successfully, but I personally would not run the QSCs bridged driving 4 ohms. It's a big challenge for any amp and IMHO not worth the risk. If you've been anywhere near using that 3-1/2 kilowatts, those woofers are surely well-worn and a reasonable replacement target for that reason alone.
Also, a couple additional facts would help us give better advice: What is the crossover frequency of the existing installation? And, what program material?
What you described sounds more like 'woofers' than 'sub-woofers' - crossed over at 500, 800 or even 1200 Hz. That knocks a few design options out of consideration if the replacements have to work that high.
A couple/3 microphones to produce speech is an entirely different challenge than a combo w/keyboards-bass-guitar-drums and vocals, or even bulk-mike-ing a large choir.
And keep in mind, churches are notoriously under-damped, w/the only absorption often being the patrons. Furthermore, the bottom two octaves are usually treated to less absorption than the rest of the spectrum. 3-1/2 kilowatts driving high-efficiency cabinets could swamp the whole space anytime that it isn't packed.
Cheers,
Rick
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