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Workshop audio system

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  • #16
    Originally posted by zobsky View Post
    If this is for a garage / shop project, . .I'd advise revising your requirements.
    1. You aren't going to be nailed down to the sweet spot (not intentionally, at least), .. so wide dispersion is important.
    2. Go cheap, .. the environment and temperature swings won't be kind to the drivers long term.
    3. Since you already have a 2 way crossover, .. consider building something with a fullrange and use the crossover to cross over to subwoofers (if needed or desired)
    4. You need something to get reasonably loud or sound punchy. Utmost fidelity is not a prime concern here.

    With these factors in mind, I'd look at some of the smaller Karlson variants and hang them from the ceiling with the apex of the slit facing downwards.. Most folks on this board don't know about them, or understand them, let alone heard them (or have heard the old school karlsons), The load on the driver will control cone motion, minimizing intermodulation distortion - so you could plausibly get away with a fullrange driver.

    For example -

    You could put a cloth grill behind the K-slot to protect the driver from dust if you want to.

    From that thread
    It's very musical sounding and very engaging to listen to. There is no fatigue and in fact, you can take a driver that normally may have some nasty peaks that cause fatigue in an open face speaker, put it in a Karlsonator and the aperture smooths out and cleans up the peaks - homogenizes it and the speaker can be listened to without harshness. Listen to some sound clips in the mini Karlsonator thread and you will get an idea.

    What's the downside? The K-aperture will cause some dips in the mid response, the famous W shaped set of dips. These are not that audible or noticable, but prevent the Karlsonator from being a hifi speaker or a "monitor". For normal listening to music though, it is, again and again, my preferred "go to" speaker. Also, I would recommend it as a first full range speaker build. Very easy to make.

    Very interesting.
    I thought about dipoles or bipoles for this space as well.
    1. listening area creates some challenges, yes. I will post a diagram
    2. big temp swings, currently no insulation. 40s to 110s.
    3. I will look into a full range,
    4. correct goal is not utmost fidelity. I think speaker placement will be important.


    • #17
      Here is the basic layout of the building. Currently the main speaker hang from ceiling (the little squares). The listening area is mainly fixed at workbench and 2 post car lift.
      Other options include placing speakers in either red or blue pill locations.
      Haven't though about placement of 4 mains yet


      • #18
        little amp finally showed up after being stuck in the mail for a month. I built the rack out of leftover 2x4s and a pair of rails. P3D2-12 on order only $63 each. Been playing with 'Woofer Box and Circuit Designer 5', great toy.... thanks to those who support it.


        • #19
          Unfortunately at this point I have too much going on to have the time to design/build/test/modify a set of main speakers. So I have been looking on Craigslist for a decent set of bookshelf speakers. After a few failed attempts at actually purchasing something, I decided to use some equipment I already have. I also realized I have never actually bought complete speaker system, I have always made my own starting when I was a kid.
          So plan C is to use these RF component speakers that have been sitting for 4 years until I actually use them in a vehicle. They are power T156. The x-overs have a 'on/off axis' switch that attenuates the high end and a selectable tweeter attenuator.

          I whipped together some enclosures out of MDF

          Applied a thin coat of lacquer and installed the drivers. The grills defeat the sealing gaskets on the drivers so I left them off.

          I installed in the same location as the old ones. So how do they sound? Well, the QSC main amp has some issues. I hoped it was related to the old speakers but it looks like the current limit circuit in the amp has a problem. Once it heats up from driving a load one clip light comes on and the output goes to crap. The 4ohm load of these speaker is even worse.

          I found a service manual for the amp, and have identified where to look. Just need some time to dig in and see what's going on with it.


          • #20
            Made some progress on the subs, cut all the pieces and assembled one unit. Being short on time I decided to not fabricate custom flared ports. Yes I could spend $100 on flared ports, but I am too cheap. I went with a pair of 4" ports which given this driver should be fine under most conditions. Going with this simple design also allows them to be easily removed for tuning. After farting around with design s/w I chose an alignment consisting of a 2.9cuft box and a port tune target of 28hz. This yields an effective -3db point at 24hz, and a +3db bump centered at 32hz. A flat response needed REALLY LONG ports and not much music has info below 25hz (or 32 for that matter).
            I needed more than a whole sheet of MDF for a pair of ~3.5 cu ft enclosures.

            The nominal port length is 25" so I build a brace that supports the other end.

            Installed a driver. Need to measure system resonance and adjust as needed.

            How does it sound? Better than what I had but I just placed it on the ground for now, which isn't a good location. Even at moderate volume port velocity is very low. I'm Bummed that the main amp is not working properly, so I didn't really get to evaluate the system. oh well, adapt and overcome.
            Last edited by rattle_snake; 11-07-2016, 02:58 PM.


            • #21
              Sub #2 going together. To try and get best fit I do the following
              -clamp the pieces dry and drill pilot holes thru both
              -remove the piece and drill clearance holes, countersink for screw head
              -Apply glue to both surfaces, clamp back together
              -install drywall screws
              Basically what you have to do if you were using steel or some other metal, although in this case the fasteners are just to hold the pieces together until glue dries.

              I install the piece opposite the baffle last (back). This allow me to apply a bead a sealer to all the joints except the back, and after installing the back I can seal it through the speaker opening.


              • #22
                Finished building sub #2 and placed them in the back corners of the building. This location works well for the most part and gives a fairly uniform response in the building, better than I though it would. I don't want to use the floor space for the subs although placing them on the concrete greatly reduces the energy transferred into the structure and subsequent buzz/rattles. The system meets my SPL expectations and likely exceeds what my neighbors think is reasonable. So far I am happy with results but still need to tune ports, decide on a finish and come up with some mounting system or feet for them.

                With the active x-over I am able to heavily attenuate main channel #1 and run the rest of the system. This further indicates an issue with the current limiter circuit in the QSC amp.


                • #23
                  Box tuning came out close to predictions from 'Woofer Box and Circuit Designer 5'. I measured impedance min at 29.1 and 29.5hz for the respective boxes against a target of 28.7. One contingency plan was to fab an extension plate/ring out of MDF with a 3/4" radius routed into it that would effectively extend port length another 3/4", and provide an outside flare. Given my observations this isn't needed.

                  At full power port airflow is surprising low and there is no perceptible port noise, even with tones.

                  With Sine inputs the sub's are pretty impressive at full power

                  Interestingly, the main speaker's output is degraded/overdriven before the subs clip or distort. Opposite of most my experiences.

                  The corner placement of the subs does provide higher output and even coverage, however when listening in the center position there are standing waves in the room that muddle the response. When close to the enclosures the response is tight provides the punch I am looking for. So more experiments are needed, but will have to wait as it's back to construction on the building itself. Getting iMM6 mic to tune the system.

                  Murphy law prevailed as I wasn't able to reproduce the main amp's current limit issue before I removed it from the rack to investigate. I can only figure this is from playing the tones at high SPL (one sub is directly below the rack) and the vibrations affected a cracked resistor or a suspect solder joint. I ran the system at a decent level for several hours without issue, but right before shut down the issue can and went a few times further indicating a intermittent bad connection. Up to this point the issue was always present.


                  • #24
                    An easy way to lengthen the ports a inch or so id to cut a coupler in half and fill the end of the coupler with spare pipe. You could even route a small flare given the double thick PVC at the end..

                    Note you may have to sand the end of the pipes circumference for the coupler to fit flush as I don't think a slide coupler is available in the larger PVC pipe sizes.


                    • #25
                      Update on this extra slow going process. After moving stuff in and out for drywall and other projects, this is where the speakers are for now.

                      finally built another rack for the equipment. Still need to finish all the speaker boxes. Subs will hang from wall or ceiling and not stay on the shelf, as it will get doors.


                      • #26
                        Finally painted the main speakers, a year later....

                        I spent some time re-tuning the system to it's new speaker locations. The EQ curve is quite different that it was before for and sounds a hell of a lot better. I am also using a bluetooth link instead of headphone jack and the frequency response is noticeably different, interestingly but not surprising. Still need to finish the subs.

                        The system has exceeded my expectations. It pounds out heavy metal in a brutal fashion. Cheap, big low end, loud as [email protected]%&.


                        • #27
                          Wow....Nice job!