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  • I got my hands on some high quality 1inch thick EPS......Although they sound a little more accurate the highs are not there just like with the lower grades of EPS, so I am a little disappointed thinking that the better grade of eps material would of solved my higher frequency issues.....now I am focusing the issue more on the exciter then on the materials itself. I will see when my order of my 25TP exciters get here if these exciters have a higher frequency range then my 30he.

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    • Originally posted by Crapflinger View Post

      I've done a lot of craft work with foam core and....glue warp is a yuge problem. it's caused by the paper absorbing the glue while the foam doesn't, so as it dries it contracts the paper with it. it does it with PVA, paint, spray glue...just about anything that wets the paper. rubber cement seems to be a bit less of a bear as it doesn't soak in as much.

      I've had SOME success in the past with affixing the "back side" (i.e. whatever side you're not gluing at the time) to a bit of a frame made out of wood or something stiff with double sided tape. also, if it's even remotely possible (pro-tip it usually isn't) you can mitigate a lot of the warping by painting the glue on both sides at the same time in exactly the same way (the one time I did this was for something specific project. had to suspend the panel from a stand I made out of bent up coat hangers and me and a friend painted each side at the same time, in the same place...like I brushed on the right side of my side and the friend brushed on the left side of her side....it was a MASSIVE PITA).

      maybe if the side were treated with a very very thin coat of primer of some kind, it would prevent the glue from absorbing as much?


      also, fellow IT guy

      Hey Crapflinger! Thanks for the input, man... sounds like your you have a tad bit of experience with foam core. So coating both sides as quickly as possible was my initial thought but standing it up was a piece I didn't consider... thought some pressure to flattening the panel as needed but I'll try the keeping the panel upright and see how that goes. It doesn't need to be perfectly flat so this may do the trick. Will just need to move quickly with the roller!

      Thanks for the suggestion ma man!

      Comment


      • Originally posted by Unbiasedsound View Post
        I got my hands on some high quality 1inch thick EPS......Although they sound a little more accurate the highs are not there just like with the lower grades of EPS, so I am a little disappointed thinking that the better grade of eps material would of solved my higher frequency issues.....now I am focusing the issue more on the exciter then on the materials itself. I will see when my order of my 25TP exciters get here if these exciters have a higher frequency range then my 30he.
        Hey UBS, sorry to hear about your experience with the higher grade EPS. What grade did you get and where did you purchase? I'd love to get my hands on some.

        I'm curious what the panel size is, how it's suspended, panel positioning in the room, what they are suspended on to get them off the ground, etc.

        See these measurements below for different materials and exciter combinations. Small small EPS panels have good extension to 10K with a 10dB dip centered around 16K and comes back up to normal levels around 20K. The ply panels are the smoothest and most extended without EQ.
        Click image for larger version

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        One thing to consider with a DML is the panels power response. As per one of the white papers that I've mentioned here before, there is a rising power response that peaks +6dB at approx 15K. I cannot validate this myself, but when EQing a panel perfectly flat, I do feel the response is peaky and they sound shrill so have always believed the power response published is reasonably accurate. I do question whether the power response truly peaks at 15K or not... that is in a bit of question to me.

        See the light green trace, its a KEF Q500 with the mic at tweeter level. The panels where placed on my typical stand and the mic kept at the same location so the last octave was not always at the exciter level which could change the 10K+ level.

        Anyway, I hope this helps!


        Comment


        • Originally posted by rmeinke View Post

          Hey UBS, sorry to hear about your experience with the higher grade EPS. What grade did you get and where did you purchase? I'd love to get my hands on some.

          I'm curious what the panel size is, how it's suspended, panel positioning in the room, what they are suspended on to get them off the ground, etc.

          See these measurements below for different materials and exciter combinations. Small small EPS panels have good extension to 10K with a 10dB dip centered around 16K and comes back up to normal levels around 20K. The ply panels are the smoothest and most extended without EQ.
          [ATTACH=CONFIG]n1276135[/ATTACH]

          One thing to consider with a DML is the panels power response. As per one of the white papers that I've mentioned here before, there is a rising power response that peaks +6dB at approx 15K. I cannot validate this myself, but when EQing a panel perfectly flat, I do feel the response is peaky and they sound shrill so have always believed the power response published is reasonably accurate. I do question whether the power response truly peaks at 15K or not... that is in a bit of question to me.

          See the light green trace, its a KEF Q500 with the mic at tweeter level. The panels where placed on my typical stand and the mic kept at the same location so the last octave was not always at the exciter level which could change the 10K+ level.

          Anyway, I hope this helps!

          I got the hardest grade they had out of I think 5 different grades and I ordered it on ebay...down fall is that there is only a set standard size which is approx. 15X23 inches and you have to buy a minimum of 10 pieces. They come in 1inch and 1/2inch thick. I got the 1 inch thick in which I sort of regret not getting the 1/2 inch thick ones as it seems the vibrations travel better through the less thick panels.

          Thanks for the graphs it helps me to see what my ears may have been missing. It could be that dip at 15-16k that makes it seem like it is lacking in the higher frequencies.

          Comment


          • I received my DAEX25TP yesterday. Did some comparisons with my DAEX30HE and the DAEX25TP seems to have a slightly higher frequency response from what my ears can tell me LOL. As most of you all know I use 2 exciters per panel like my bertagni speakers. With 2 DAEX30HE its kind of over powering and that extra power seems to cancel some highs out. By using the DAEX30HE with the DAEX25TP together it seems like it blends better as the 25TP does not produce a lot of bass/power as the 30HE. Although the highs are still not up to my desired preference they are better then they were before. My next project is too make 2 separate panels one for the highs and for the bass for each speaker so that only one exciter is used per panel instead of two.

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            • After more experimenting using 2 DAEX25TP together on the same panel sounds better to me then using 1 DAEX25TP and 1 DAEX30HE together. The DAEX25TP IMO just sounds better all around then the DAEX30HE including the bass. The bass is not as strong as the DAEX30HE but the tone of the bass just sounds better as well as the higher frequency response and clarity, similar to what Mildperil on the other forum mentioned....I have 4 of the DAEX25TP and I will be ordering more of it in the near future.....I also want to try other exciters to see how they compare like the Tectonics brand of exciter.

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              • I finally found a little time this afternoon to post some things I've been working on. Sorry, but it's going to be a flood of pics.

                First up is a pic the way the 20x28.25" speakers are hanging in the room. You can tell how small the room is in the pic, and I'm concerned about how much that may impact the sounds, but it is what it is.

                In this setup, there seems to be a lot more bass when I get my ear down to the level of the panels. When standing, the bass seems much less.

                I've also tried squeezing the panels at various points with my hands (to increase the suspension), but I can't tell a difference.

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                • Next up, I thought it would be cool to make a 24x48" ceiling tile as this room has a drop tile ceiling. For suspension, I used a really soft foam tape made to seal doors and windows (it's 5/16" thick), and I wrapped the sides and the bottom edges - basically everywhere it might touch the ceiling support grid. Suspended this way, there is a little bit of vibration that I can feel in the ceiling support grid, but it's not enough to make audible noises in the ceiling.. so I'm pretty happy with it.

                  The panel itself is the same 1" XPS that was used in the 20x28.25" panels. The top of the panel is rounded, but the bottom was left untouched to have a good edge for the suspension tape to stick to. I figure this is a pretty good way to terminate the edges in this configuration.

                  When the panel is leaned against a wall, it sounds like total crap, but when mounted in the ceiling it sounds pretty darn good. It's still a bit 'shouty' in the vocals, but the bottom end is so much fuller sounding compared to the 20x28.25" freely suspended panels. Rich, I think you're right about needing more suspension for the smaller panels.

                  The REWS plot shows much better bass extension for the bigger panel. There's still a roll off in the high frequencies, but it's more gradual (not as steep) as the smaller panel - which is unexpected to me.

                  Comment


                  • Ok.. so all fun and games up to this point, and now on to my real goal for these speakers ;) . I'd really like to get a set of speakers to use for home theater in the living room. There are a couple of challenges here that I'm trying to over come:

                    1.The room is large, and the listen positions are diverse. There are 6 people in the family and every Friday is movie night. Some people might be on the floor right in front the TV, some on the couch 15' back, some on the balcony 10' up and 25' back, sometimes off to one side or the other. I was looking hard at line arrays to reduce the effect of listening position when I came across Rich's DML article. Given how much cheaper and easier these are to play with, this seems like a great place to start. Honestly, the 'shouty' nature of these panels amps up the vocals, and I think that's a positive thing for movie watching.

                    2. I need something that looks good to the better half, and raw pink panels ain't it. I'm currently thinking wood frame with black speaker cloth wrapping, and that means I need a way to enclose the panels.

                    3. The space between the TV and window is about 12" on each side. This means I need a NARROW speaker - and this right here might be the DML deal breaker.

                    Pushing on.. I made a wood frame from 1x6 pine. Given the narrow space I have to work with, the widest panel I can fit is about 9", but I have lots of vertical space. I made two configurations for testing. One with a 9x44" panel, and one with 2 9x20" panels. They are minimally suspended at the top and bottom with 2" acoustic foam. I figured this would be a good way to keep vibrations out of the frame, and it does a great job at it.

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                    • The 9x20" and 9x44" sound indistinguishable to me, but the REWS plot of the 44" panel looks a little flatter on the low end. All of the panels I've tested so far share some similarities:

                      1.1" XPS pink foam
                      2. treated with two coats of 1:1 water / Elmer's white glue - front and back
                      3. DAEX32U-4 Ultra exciter (one per panel)

                      Next up to try: I have acquired some different thicknesses of XPS pink foam - 3/4" and 2" . I'm thinking of sanding the 3/4" down to a 1/2" or thinner.

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                      • ..and finally, just for fun, I tried to make a speaker out of a glass window. Where I work, there is a datacenter with server racks on side and a lab on the other. There's a wall between with a 4'x5' single pane window. I thought it would be fun to pump 'invisible' music in to both rooms at the same time :D so I stuck an exciter to one side of the window. Sadly, the sound quality was universally hated... sigh. ah well.. back to high speed fans and 60 cycle hum ..

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                        • jp7189 ... As far as the WAF goes, does she like any particular kind of art? Know someone good with a brush? Turn the panels into a piece of art.
                          http://techtalk.parts-express.com/fo...khanspires-but
                          http://techtalk.parts-express.com/fo...pico-neo-build
                          http://techtalk.parts-express.com/fo...ensation-build

                          Comment


                          • Originally posted by Unbiasedsound View Post

                            I got the hardest grade they had out of I think 5 different grades and I ordered it on ebay...down fall is that there is only a set standard size which is approx. 15X23 inches and you have to buy a minimum of 10 pieces. They come in 1inch and 1/2inch thick. I got the 1 inch thick in which I sort of regret not getting the 1/2 inch thick ones as it seems the vibrations travel better through the less thick panels.

                            Thanks for the graphs it helps me to see what my ears may have been missing. It could be that dip at 15-16k that makes it seem like it is lacking in the higher frequencies.

                            Hey UBS! yeah, 1/2" for a higher density panel would probably be a better choice but you might want to use something like a golf ball or ?? to sand a scooped out area (inverted dome) in front of the exciter... something to try since you have the EPS!

                            About the dip in my EPS freq. response above... that is likely a resonance within the cavity of the exciter/panel. I didn't troubleshoot that issue since they were test panels but feel that it should be able to be corrected. Unsure of the root cause but may be the inconsistent/uneven/rough surface of the EPS.

                            You are probably having some issues with the HF response due to multiple exciters on a single panel. I don't recall the source, but placing 2 exciters increases the low freq. response by +3db compared to high frequency... can't say at what frequencies and what the shape of the transfer function of this effect, but more bass will, subjectively, make the panels appear to have reduced high freq. response. If you have a few capacitors around the shop, I would high-pass the "tweeter" exciter and assess the result.

                            Miss being around this forum... soccer and track in full swing so very little time at home... work has been busy so little time during the working day too... such is life. Hope everyone is doing well!

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                            • Yeah with the thinner 1/2 inch eps one has to be fairly careful as I have made a hole in them when experimenting with carving out designs in those think 1/2 inch panels. lol

                              I dont have any capacitors but I did have a old pair of 2 way cross overs that I took out of a mirage M490 speaker a while back and tried to see if the highs would improve. Well IMO it didnt really improve the highs and it actually sounded better with the high being used as a full range due to a fuller sound.

                              The big improvement though was using a less powerful XT25 exciter for the highs and the powerful 30HES exciter for the bass...or even 2 XT25 exciters but the down fall is lack of strong bass and lack of volume.

                              I seen a can of epoxy resin at the store but it was around 35 bucks for the can. I only need a cap full of it too test it out and the rest will be wasted if it does not meet my sound quality desires. LOL

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                              • I've been out of the loop for a while due to health issues and hospital stays, I hope to get back to playing with DML's soon.


                                I still think multiple exciters need to be on separate panels to increase power handling and maximum high frequency response.
                                In my walks, every man I meet is my superior in some way, and in that I learn from him.

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