Moderators dtel Posted July 19, 2009 Moderators Share Posted July 19, 2009 The room is 45x30 and sound system is on the long wall. [] That's not a room that's a real full size movie theater ! [] Quote Link to comment Share on other sites More sharing options...
Wrench722 Posted July 19, 2009 Author Share Posted July 19, 2009 The room is 45x30 and sound system is on the long wall. That's not a room that's a real full size movie theater ! It sounds big. But the big problem is there is a door on every wall. So it is like I am putting a system in the middle of the room. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted July 20, 2009 Share Posted July 20, 2009 I'd think that you would want a lot more output than that. For a room that is essentially 11,000 cu ft, you need a LOT more horsepower than a singe 15. I would look at using 3-4 18's in a large vented box or building an infinite baffle. ( assuming you have another room that you could use for the backwave ) Power wise, for the money nothing will touch a pro amp, the Behringer EP2500 will do 1200 w RMS bridged into an 8 ohm load, close to 1900 w into a 4 ohm load. The EP 4000 is a newer update of the same amplifier, it has a newer faceplate and updated graphics, but it's the same under the hood. Most all pro amps have different input connectors than home amplifiers. These can be connected with a cable that has an RCA connector on one end and an XLR on the other, or a cable that is RCA > 1/4 Mono. You can get these at a lot of places, even your local music instrument place. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted July 20, 2009 Share Posted July 20, 2009 I'd think that you would want a lot more output than that. For a room that is essentially 11,000 cu ft, you need a LOT more horsepower than a singe 15. I would look at using 3-4 18's in a large vented box or building an infinite baffle. ( assuming you have another room that you could use for the backwave ) This might work. Quote Link to comment Share on other sites More sharing options...
Wrench722 Posted July 20, 2009 Author Share Posted July 20, 2009 I already have two RWS-15 and two little JBL E-250 and I want to replace them JBL,s with two subs that would out power the RWS-15,s. So I would like to use a bass plate so that I can move them around and have auto switching (on/off) and 1000 watts on a 15" sub. MAN! CECAA850 That is cool pic! Quote Link to comment Share on other sites More sharing options...
michael hurd Posted July 23, 2009 Share Posted July 23, 2009 I understand that you want to use a plate amp, but without any other parameters, that's sort of like saying you want to have 500 horsepower in a pickup. Does the pickup weigh 3500 pounds, or 8000 pounds? Without knowing what the actual power requirement of the driver in an actual box is, you could be under or overpowering it. I still say you need a lot of horsepower. If you want to have more output than a pair of RSW-15's and you like how they sound, you may look into buying a pair of 18" pro audio drivers and installing them in 10-12 cu ft ported cabinets. Of course, depending on the actual driver parameters, and the box tuning frequency, you may only need 300 watts a piece to get to the maximum safe excursion level. 500 watts may cause damage to your wallet when you clank the coil on the backplate or tear the suspension. Hoffman's Iron Law: One of the most fundamental design principles that the new DIY speaker builder mustlearn is generally known as "Hoffman's Iron Law". First formulated back in theearly 1960's by Anthony Hoffman (the H in KLH), Hoffman's Iron Law is amathematical formula that was later refined by Thiele and Small, whose work nowforms the basis of all modern loudspeaker design. Hoffman's Iron Law states that the efficiency of a woofer system is directlyproportional to its cabinet volume and the cube of its cutoff frequency (the lowestfrequency it can usefully reproduce). The obvious implication is that to reducethe cutoff frequency by a factor of two, e.g. from 40 Hz to 20 Hz, whilestill retaining the same system efficiency, you need to increase the enclosurevolume by 23=8 times! In other words, to reproduce everlower frequencies at the same output level you need an extremely large box! However, box size isn't the only variable… You can continue to use asmall box by accepting a much lower efficiency. In order to retain the same soundpressure level (SPL, meaured in dB's), though, this requires both avery large amplifier and a driver that can handle a lot of power and move a lot ofair (requiring high excursions). Furthermore, it must be able to do so with minimaldistortion. This is exacerbated by power compression, a phenomenonwhere the power heating of the driver's voice coil results in a non-linearrelationship (read "distortion") between the electrical power in and the acousticalpower out. Another variable not often mentioned is bandwidth… You canprovide the perception of violating Hoffman's Iron Law by using abandpass design, which can provide a lot of bassprimarily across a very limited bandwidth. In all too many bandpass designs, theimpressive bass is produced around a single frequency. This is often referred to as"one-note bass". It can rattle the furniture and impress your friends, and may evenbe OK for sound effects in action movies, but don't expect too much accuracy whenlistening to music with a lot of low bass content. Summarizing, Low-frequency capability, box size, and efficiency form the three keyaspects of system design. To increase any of the three, you have to give upsomething from the other two, with box size being the most sensitive. The oftenunpopular bottom line is therefore to plan on using the largest box you cancomfortably live with. This partially explains the popularity of subwoofers, whichcan be both large and hidden from view, and often include their own built-in highpower amplifier. Quote Link to comment Share on other sites More sharing options...
Wrench722 Posted July 23, 2009 Author Share Posted July 23, 2009 Well I guess I am kinda doing things backwards. I was going to find a good amp and then build around it. So what 18" Pro Audio are you referring to? Quote Link to comment Share on other sites More sharing options...
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