QSC amp or AVA250, crossover's needed??

Discussion in 'Archived Threads 2001-2004' started by Cam S, Jan 21, 2002.

  1. Cam S

    Cam S Screenwriter

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    I've been planning out a Shiva SonoSub for a while now, and was thinking of going with either the Amp350 or AVA250 plate amp to power it. I have heard alot about QSC apmlifiers and how good they are, and the price/power ratio is better than the plate amps, 830 watts @ 4 ohms mono for $500can. My question is this, what, if any, crossovers, EQ's, etc etc would I need to have an optimal working powere subwoofer. Is there any difference to the crossover's used on the QSC or the AVA250/amp350?? I've been nothing but confused about all this Linkwitz riley talk etc etc, so if someone could clear it up for me that would be greatly appreciated!
     
  2. Brandon B

    Brandon B Second Unit

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    The QSC's are pro audiom amps and as such, do not have crossovers, phase switching, etc. built in. You would need to add one unless you are using a receiver with one (Dolby Digital) built in. AVA 250 has all that included.

    What the QSC will give you is a lot more power and better performance.

    It will also give you fan noise and another box to locate.

    BB
     
  3. Cam S

    Cam S Screenwriter

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    For a reciever I am running a Technics SADA-10. Any idea if this has any of the features you are talking about built in. If not, what type of product will I need to allow the adjustments needed for a subwoofer.
     
  4. Aaron Smithski

    Aaron Smithski Stunt Coordinator

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    If you decide to go the QSC amp route one option is to use their SF-1 subwoofer filter if you use the PLX or DCA line of amps. This is available at the www.QSCaudio.com on-line store for $158. Have not looked for it elsewhere but I am sure there are resellers that are probably cheaper. I don't think it will work with the RMX series but there are other outboard options you could pursue.
    Cam, I believe you are comparing apples to oranges. The QSC amp you mentioned puts out over 3 times the power than that of the Adire plate. Although the Shiva is rated for 600 or so watts many a sub builder has been more than satisfied with the 250 watts that the Adire plate puts out because of the Shiva's efficiency. But if you were to purchase the QSC RMX 850 you would have enough power to drive 4 Shivas @ 207.5 watts apiece. Granted that is huge output but that is what I am saying. The QSC amps are for the bass hungry.
    I recently ordered a few QSC PLX 2402 amps. These will do 850 watts mono/16 ohms, 1500 watts mono/8 ohms, or 2400 watts mono/4 ohms. Should be perfect for a multiple driver array!
    Aaron Smith
     
  5. Cam S

    Cam S Screenwriter

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    Thanks for the help Aaron, much appreciated. I'd really like to get the AMP350 from Stryke audio since it has 100 more watts for a little bit more money. I guess getting a QSC amp (or anything like it) would end up costing 3 times as much over the plate amps.
     
  6. Brandon B

    Brandon B Second Unit

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    Your receiver is a dolby digital receiver,. so it does have an LFE (low frequency effects) output. I did not find info on it's crossover point, however.

    Your receiver takes the .1 (of 5.1) track and puts that out the LFE output. It likely can also route bass information from your other 5 speakers to the sub, when they are set to a small setting. This means you do no need a crossover to use your sub with a QSC amp. You will need to look in your manual to find out what the crossover frequency is, and if it is adjustable.

    Most dedicated sub plate amps also have other features however. They have line level and speaker level inputs, so you can run them with a 2 channel source by runningn the speaker connections through the sub, then to the speakers. They have a phase control or switch so you can adjust the phase of the sub to mitigate some cancellation effects in your room. If only a phase switch, the same result can be accomplished by switching the speaker wire leads to the sub. Neither type of amp really gives you eq capapbilities. You'll need to get an equalizer of some sort if you have room response issues (reinforced or cancelled frequencies) that bother you.

    If you think you might want to build a bigger sub in the future, or really like the power reserve (I personally am a big proponent of overkill), I'd get the QSC.

    However, with your setup now, Aaron is right, the plate amps are PLENTY of power.

    BB
     
  7. Dustin B

    Dustin B Producer

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    Remember that the the Shiva's voice coils are rated at being able to handle 650W continously. This just means they won't melt if you apply that much power to them continously. The more important number for power applied is excursion (ie Xmax). It will take a lot less than 650 watts to get a Shiva past Xmax in just about any enclosure.

    You should download LspCAD from Adire's site. Model the enclosure you are thinking about. Make sure you configure the voice coils in parallel. Then in the watts into 8 ohms box enter half the amount of power you intend to apply to the driver at 4 ohms (LspCAD assumes a perfect amp and doubles that number when you specify the VC are in parallel).

    If the excursion plot gets to 31.6mm you are applying enough power to hit Xmax. More power is pointless.

    Everyone of Adire's suggested vented allignments hits or exceeds Xmax of a Shiva with 250 watts at 4 ohms (ie 125 entered into the watts into 8ohms box).
     
  8. Cam S

    Cam S Screenwriter

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    I tried lspCAD but it was too confusing, so I tried WinISD instead. It doesn't show the Excursion like lspCAD does but it is ALOT easier to work with. Sounds to me like even the AMP350 plate amp would be too much. Has anyone used this amp with a Shiva or any other sub in a DIY project??
     
  9. Dustin B

    Dustin B Producer

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    Take a little time to figure out LspCAD. It's really just looks harder to use than it is. WinISD is significantly less accurate.
     
  10. John A. Gordon

    John A. Gordon Stunt Coordinator

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    Hello Cam,

    How goes the amp decission? Here are a few comments regarding QSC amps.

    - It is correct we do not have built in crossovers with the amps in question, though many of our amps have High Pass Filters (30Hz or 50Hz) you can set, or defeat.

    - We do have accessory units for crossover use:

    - the SF-1 mentioned is actually for our MXa line of amplifiers, it will not work with the PLX or DCA line.

    - the SF-3 is a subwoofer filter used with the DCA line of amps--it attaches on the rear of the amp.

    - but what is even better is the DSP-3 or DSP-30 units. These little babies will do whatever you program them to do: crossover, EQ, filters, etc. etc.

    Enjoy,

    John Gordon

    QSC Audio Products

    Costa Mesa, CA
     
  11. Cam S

    Cam S Screenwriter

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    Right on, can't get help from a better source, thanks John!!!

    My amp decision will come down to price. I will have to order in from the states, so there will be a significant price difference between the two.

    It's a shame we couldn't buy a plate amp such as the one on the Ariel SW-12, wow, that thing is NICE.
     
  12. Aaron Smithski

    Aaron Smithski Stunt Coordinator

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    John,
    Thank you for your input here. Did I misunderstand the applications of the processors? It states "BusCards are required to add certain accessories to PLX, CX, DCA, and PowerLight amplifiers" at the top of the BusCard adapter page at the www.qscstore.com. I figured with the addition of a BusCard to the PLX amplifier one could use the SF-1 filter. Guessed (incorrectly I think) that the SF-1 was a rack mount.
    I am expecting some PLX 2402 amplifiers to arrive soon so could you please clarify if I can add any of your processors to my amp. I kind of fell into these amps not knowing the ins and outs of them but the price was too good to pass up. I was sold on all of the positive QSC posts on this forum and figured I could make them work.
    The DSP-30 looks like a nifty piece. Can it be configured as a parametric eq and a subwoofer crossover simultaneously?
    Thanks,
    Aaron Smith
     
  13. John A. Gordon

    John A. Gordon Stunt Coordinator

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    Aaron,

    The DSP-30 will do what you desire: x'over and parametric EQ, plus a host of others if you wish. And it is rack mountable. You program the DSP-30 to your liking, the number of configurations are almost limitless. One thing to remember though, it is a tool, so use it wisely.

    As for the BusCards, I would not recommend for you to use them. The BusCards are needed if you were to add one of our analog accessories to your PLX. The DSP-30 is a much better choice.

    btw. The SF-1 subwoofer filter is not compatible with the BusCard or PLX, it is for our MXa line of amplifiers (the SF-1 attaches to the inside of the MXa amp and is not rack mountable.

    Enjoy the PLX 2402's (you said some, so I assume at least 2 units?). One benefit of the PLX is a built in filter you can set to 30Hz, 50Hz, or off. Great for speakers that do not go too low.
     
  14. Aaron Smithski

    Aaron Smithski Stunt Coordinator

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    Thank you for your expertise John! Couldn't ask for a better source. I will be using 4 Tempest drivers in an infinite baffle configuration and was considering the DSP-30 as the crossover. Not sure if I will need any eq yet but right now all I have at my disposal is an old Audio Control Richter Scale 1/2 octave eq/crossover. The crossover point is changed via a plug-in module (clunky) and I'm certain the eq frequecy adjustments will not be precise enough to fix any problems I may incur.

    Yes, multiple PLX 2402's are on their way. This was not my original intention but I happened to see 7 of them on an auction site and the price was attractive. I bid for 3 of them but was bumped out of the bidding. I increased my bid and was bumped a few more times. Kind of irritated by this time I was maybe a bit rash and increased my bid and went after all 7 of them. I am now the proud owner of 5 PLX 2402's even though I need only one! Off to the Hardware For Sale forum I go...
     

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