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AudioEngine A2+ Modification and Mini Subwoofer

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  • AudioEngine A2+ Modification and Mini Subwoofer

    Hello,

    Have a couple questions regarding modifying the AudioEngine A2+ desktop speakers to work well with a small subwoofer. I currently have a Peerless SLS-P380945 5-1/4" subwoofer driver that was originally intended to replace a Logitech driver but the magnet was too large to clear the port so I had to make a new box. Made the new box to fit the logitech amp but then the amp broke during the rebuild so now have a Lepai LP210PA powering the sub.

    Questions would be:

    1. Can anyone provide any guidance or advice on how I would be able to add a high pass filter to the AudioEngines so they don’t keep trying to reproduce the lower frequencies and doubling as a desk fan?

    2. Would someone assist with providing some best practices or modeling on an optomized enclosure for that subwoofer driver? I don’t need extreme volume, just something to house that sub and be driven by that amp to get the lowest frequency response I can. The box I built seems to work pretty well above 60hz but goes pretty quiet below that. I think the port might be too small since I get chuffing below 60hz or so. Current enclosure is about .17cf and ported with the Logitech port which was 1.25” diameter.

    Thanks for any any help or suggestions. I read through several posts about other somewhat similar projects but tend to get lost in some of the calculations.


  • #2
    I'm not sure if I can be helpful.

    When I built a Voxel sub for my Quarks, the plate amp (sa70) had a cutoff for frequency response for the satellites.

    Amp (ad18) } plate amp (subwoofer) , to satellite

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    • #3
      Thanks for the reply, the plate amp I’m using does have an adjustable low pass filter but the problem I’m running into is that the AudioEngine speakers have built in amplification with line out to a sub. If I EQ the AudioEngines then it ends up EQ’ing the sub as well. Was hoping there’d be a way to install a filter somehow between the amp and the drivers in the AudioEngines that wouldn’t mess with the existing built in crossover network, just want to limit the bass that the AudioEngines try to reproduce.

      Comment


      • #4
        ^ if you can provide a circuit schematic or link to it, there are several experts around here that can read it, then simulate it and likely provide exactly what to do and where to make that happen.
        Feel free to rip my assumptions apart when wrong, or fix if close.

        Passive Radiators:
        All PR(s) Vd must at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). If all PR(s) Vd at-least double all woofer(s) Vd they'll work.
        For woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax will work.
        A PR max weight is said to be its Mms x3

        PR Systems - tight focus with key parameters.
        PR Speaker Design - thorough coverage.

        Comment


        • #5
          You're going to need an active filter before the signal to the A2's. What signal source is feeding your setup?

          Lots of options...
          A computer can be setup to use software for an active filter using a output pair for the A2+, and a separate audio output for the sub. You could get a stand alone active crossover for the system, either a pro audio one or even an automotive one run by a 12V wall wart. You could use a MiniDSP to both provide the high and low pass as well as add EQ correction to your response.

          As for your box questions... I'm sure that box is tuned too high for the woofer, but without the length of that logitech port there's no way to calculate that. You could either: A - get WinISD and do some modeling to see what you need to change, or B - look for similar designs with that woofer for suggestions.
          Electronics engineer, woofer enthusiast, and musician.
          Wogg Music
          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

          Comment


          • #6
            Signal source is a Mac Mini connected by USB to the A2+ builtin DAC. The A2+ has RCA out to subwoofer which is how the sub is hooked up now.

            MiniDSP is a great suggestion! I looked into that it could likely get that to do exactly what I need. Only downside is that it would bypass the A2+ built in DAC.

            Port length on the sub is 6" which is likely way too high of a tuning for this. I did download WinISD and input my driver T/S data but I'm still digging into how to use and interpret the results.

            I looked into the Voxel sub design that mlau mentioned. That looks really promising for my application. I should have enough MDF left over to build that. Would the design in the post below be directly applicable to my driver? Paul seems to be using the TB W5-1138SMF and I have the Peerless SLS-P830945. Should I make any modification to that design to fit my driver?

            http://techtalk.parts-express.com/fo...xel-a-mini-sub
            Last edited by fassj; 10-15-2018, 11:16 AM.

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            • #7
              Probably more than you want to spend, and needs windows to run the software, BUT..., this Dayton sub amp will take your stereo signal, run a subwoofer, and then send the remainder to your stereo amp or powered speakers. I have one, it solved my problem of 2.1 amps running the satellites full range.

              Software allows considerable adjustments.

              It powers the sub and sends the stereo signal on minus the low frequencies. Your audioengines will never see the lows.

              Dayton Audio SPA250DSP 250W Subwoofer Plate Amplifier with DSP

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              • #8
                Yeah, would love to play with that amp at some point but for this project, I'm just looking to use what I have and possibly add passive high pass or low cost filtering like MiniDSP as a most expensive option.

                Comment


                • #9
                  You could try a passive 1st order HP filter on the A2's woofers. Basically a non-polarized electrolytic cap in series with the woofer.

                  Also, the Peerless sub is a nice speaker, I used one in a 2.5 system. I'd use an oversize box than WinISD's default size; 0.25 ft3 and a 7.5" port made out of 1 1/2" PVC pipe. That will get an F3 of 47 Hz. Note PVC 1 1/2" pipe has an inside dimension of 1.61" (in case you wanted to recreate my model).

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                  • #10
                    Thanks! Do you run into any port noises? I modeled the Voxel build in SketchUp but I’m not clear on if I’d need to make any changes since I’m not using the Tang Band in the original design.

                    I have almost no experience with the components of high pass filters or crossovers. Would you be able to recomend any resources I could look into to determine which components I’d need to high pass the A2 woofers? Is it possible to maintain the existing crossover system in the A2 while just cutting out the low frequencies that are passed off to the external sub?

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                    • #11
                      No port noise problems, but maybe I didn't recognize it?

                      Paul's builds are extremely well thought out.
                      Also, not sure about the other driver...I know that one he recommends is really beefy and heavy....I was impressed

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                      • #12
                        Thanks! I think I’m leaning towards the Voxel design. I came across a few passive radiator design that look really fascinating but probably a bit beyond a beginner level build... unless anyone would be able to help me model something based on the driver and amp I have.

                        Comment


                        • #13
                          Your 5.25" 830945 woofer will only do mid 50s in 0.17cf.
                          If your 1.25" port is 5" long, you COULD go up to 1.5"id, but it'd have to be about 8" long then. A larger dia. would have to be even longer.

                          If you really want to keep that box, a Tang Band W5-1138SMF driver could get down to nearly 40Hz in that box, but the tuning would have to be even lower - which means an even longer port. A (good) alternative would be to use about a 6-1/2" "passive radiator" to tune it (instead of a port tube).

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                          • #14
                            Originally posted by Chris Roemer View Post
                            … A (good) alternative would be to use about a 6-1/2" "passive radiator" to tune it (instead of a port tube).
                            +1

                            Was going to recommend this last night (and in another thread for same reason) but was too wiped out to be coherent.

                            The other guy will need 2x 8" or 1 10" to 1 12" I think, but need to confirm first.

                            Here's a couple sites I've been digging around in recently to refresh myself on them (for finishing Esoteric LCR) and gain a more comprehensive understanding since I've been recommending them. They're fantastic in mine:


                            Passive Radiator Speaker Design - deep, thorough dive in many aspects.

                            Still digging around for more sites so I have a small library on the matter. May wind up adding these to my sig for fast reference.
                            Feel free to rip my assumptions apart when wrong, or fix if close.

                            Passive Radiators:
                            All PR(s) Vd must at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). If all PR(s) Vd at-least double all woofer(s) Vd they'll work.
                            For woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax will work.
                            A PR max weight is said to be its Mms x3

                            PR Systems - tight focus with key parameters.
                            PR Speaker Design - thorough coverage.

                            Comment


                            • #15
                              Thanks for all the replies! I don't particularly need to keep the box I have for any reason, I already ordered ports for the Voxel design. I would consider re-using my current box for PR if someone would be able to help with modeling which PR I'd need. Chris, are you suggesting a 6 1/2" PR with a 5 1/4" active? Sound interesting to me if you think i could mod that into my .17cf box.

                              Would that mean just removing the port, sealing the hole and adding a PR like this?
                              https://www.parts-express.com/dayton...iator--295-498

                              I currently have this as my active (https://www.parts-express.com/peerle...-ohm--264-1604)

                              Internal dimensions of my box are 6" x 7 3/16" x 6 3/4"

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