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JBl 728 passive 2x18 sub
Art Welter:
--- Quote from: Mal Brown on October 01, 2021, 11:22:56 AM ---Interesting read Scot. The places I go where my 4 181's are overmatched have 50 amps, 220v on either a range plug ot a CA style connector. I use a construction spider to break that out to 20a 110v lines. What let's me skate is that the LA400's I own are so efficient. 900 to 1000 watts per side at 4 ohms is all it takes... same to the mid-bass / low mids drivers. So the power requirements for what I'm doing are modest. I can see where going crazy on the sub front could actually run me out of power.
--- End quote ---
Mal,
No experience with the QSC KW 181, but sounds from Tim and Scott, the SRX728 wouldn’t offer a whole lot more output, though would save a bit of weight.
A dual B&C 18NW100 bass reflex of similar size and Fb would have a bit more output potential than the SRX 728.
Since you mentioned DIY, if power and output is a concern, you might consider my Keystone Sub “tapped horn” (TH) design using the B&C 18SW115-4.
Dimensions are 45 inches tall, 26.5 wide, 22.5 deep.
Unlike many horn designs, the Keystone is not much more difficult to build than a bass reflex box.
Due to the TH advantage, sensitivity is nearly identical to the SRX 728, it’s smaller and lighter, and uses a single four ohm driver, so uses the same power as the SRX for the same output.
That said, because the 18SW115 has almost double the excursion potential of the JBL2268H (14mm Xmax, 16mm Xvar vs 8mm), the Keystone can put out quite a bit more SPL than the 728, as doubling excursion equates to a 6 dB level increase.
Plans are available in this thread:
https://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers.html
Art
Scott Holtzman:
--- Quote from: Mal Brown on October 01, 2021, 11:22:56 AM ---Interesting read Scot. The places I go where my 4 181's are overmatched have 50 amps, 220v on either a range plug ot a CA style connector. I use a construction spider to break that out to 20a 110v lines. What let's me skate is that the LA400's I own are so efficient. 900 to 1000 watts per side at 4 ohms is all it takes... same to the mid-bass / low mids drivers. So the power requirements for what I'm doing are modest. I can see where going crazy on the sub front could actually run me out of power.
--- End quote ---
It always surprises me when venues don't take into account power requirements.
Mal Brown:
--- Quote from: Scott Holtzman on October 02, 2021, 04:34:50 AM ---
It always surprises me when venues don't take into account power requirements.
--- End quote ---
Well, as mentioned before. I live out here in what isn't even secondary market... The venues are muni parks, the events are small festivals and families in the parks. I will occasionally see crowds of 2500 but more often 500 to 1000. There isn't an actual commercial venue anywhere near me that has capacity over 500... There are afew events I do that bring in MultiQuips with 100 amps on board. Generally I get 50 of that and supplement with 110v shore power...
Scott Holtzman:
--- Quote from: Mal Brown on October 02, 2021, 05:29:23 PM ---Well, as mentioned before. I live out here in what isn't even secondary market... The venues are muni parks, the events are small festivals and families in the parks. I will occasionally see crowds of 2500 but more often 500 to 1000. There isn't an actual commercial venue anywhere near me that has capacity over 500... There are afew events I do that bring in MultiQuips with 100 amps on board. Generally I get 50 of that and supplement with 110v shore power...
--- End quote ---
Let me be clear Mal, your venues with the range plugs are ahead of 90% of the cover band crowd lounges. I noticed when I was in CA and Denver that even the dumpiest bar if they have a stage they generally have some time of aggregate power connection.
Mal Brown:
--- Quote from: Scott Holtzman on October 02, 2021, 05:32:43 PM ---
Let me be clear Mal, your venues with the range plugs are ahead of 90% of the cover band crowd lounges. I noticed when I was in CA and Denver that even the dumpiest bar if they have a stage they generally have some time of aggregate power connection.
--- End quote ---
We'll probably as being private enterprise they also get inspected. Muni parks? The inspector is on the city or county payroll and hey it was good 15 years ago and I have other places to inspect ... I mean, they meet code just aren't necessarily venues thought out as alternatives to Red Rocks ;-)
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