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  • DIY LCR passive sound bar

    Hello…I’m new to this site and am looking for advice on my first speaker build. I’m in the process of creating a new entertainment setup cause my 60” tv needed to be replaced. I wanted a 70” replacement but I also wanted a sony which meant a 65 or 75”. I ended up going for the 75” with a viewing distance of 12’. The living room tv wall is tight so I’m wanting to build a sound bar for my right, center, and left speaker. I have been researching the project for 3 weeks but that is the extent of my speaker education. I know a horizontal orientation for the left and right channels are not an ideal setup but l’m not an audiophile. I’m willing to give up some sound quality for the appearance of the setup. The speakers will be powered by a Harman Kardon avr 2600 receiver. I have currently been running the Polk rm510 5.1 speakers which I liked just fine but I recently plugged in my older definitive technology center channel and was quickly reminded of how much better this setup could sound. The Polk sub amp died so I replaced it with an rsl speedwoofer. I’ll use the surrounds from the Polk system one the bar is built but will prob get some in wall/ceiling surrounds to replace them. This gets us to the new speaker bar design. The design is currently based on the overnight sensations but I am open to other options. The others that pop up a lot are the sopranos, the swope ht, and continuums. I’m flexible on price but would like to keep the speaker kits under $500 total. Would like to be closer to $400 but if a lot greater sound can be achieved with a little bit more than why not. I plan on building the cabinet out of 3/4 mdf with a walnut veneer and it will be attached to the wall under the tv. So here’s where I need a lot of help…should I do an mtm,mtm, and mtm design or a mtm for the center and tmm for left and right? Maybe just a tm for left and right? Does anyone see where one of these kits would be a better performer in the horizontal position for left and right? Any advice would be greatly appreciated. I have other notes in the photos.

  • #2
    TM or TMM for the R and L channels will have less comb filtering. Safest bet is TM. The only advantage you're getting with the TMM is higher sensitivity.
    Isn't it about time we started answering rhetorical questions?

    Paul Carmody's DIY Audio Projects
    Twitter: @undefinition1

    Comment


    • #3
      Thanks for your input. So I’ll look at using a tm or tmm for the left and right. The tmm will just allow me to listen at slightly higher volumes without distortion…is that correct? For a 20’x14’ living where listening time is split 50/50 music and tv shows I suppose either combo would sound good? I really like the idea of a compact bar which is how I discovered your designs…very cool! I was originally planning to build this bar with the overnight sensations due to the scale and many rave reviews but I think I’d like to have black speakers. I’m planing to have the speakers exposed at the moment so a black speaker will draw less visual attention. I’m also thinking I may need a bit more output but it’s hard to say. If the overnight sensations turn out to be the best fit I can always design the bar to have a speaker cover which I think the gf would like the best. For a setup like this in a medium sized room, what 3 speaker kits would fill the space with sound? Once I figure out which speakers to purchase I can get into the final design of the cabinet. I have read that as long as you maintain the inner volume of the original design you can play with the length, width, and height a bit. Should I try to maintain the baffle width, height in reference to bar, to the original design or can it be a bit taller? I ask cause I’m looking for ways to make the cabinet sit more flat against the wall. Should I be looking to create a cavity in between each inner speaker volume or will a simple 3/4 mdf be just fine? …as shown in one of my sketches. Again…thank you for your time and advice!

      Comment


      • #4
        I still wonder why there aren't more designs out there that fit what you are interested in doing. I don't understand the acoustics (with so many talented designers out there and at my age it is easier to stand on the shoulders of others) but it seems like there are a lot of people that are interested in a design like this.

        I have built several designs over the years and other than the first few nights after completing them I don't remember doing a lot of critical listening.

        I actually have drawn out a design on paper to try using the OS design in a 5.1 soundbar and see how it sounds with the correct distances programmed into my AVR. Hopefully after my grandson finished baseball this spring I will find the time to rest it out.

        Comment


        • eavo44
          eavo44 commented
          Editing a comment
          I was also surprised that this type of design, LCR bar configuration, isn’t a concept which is pursued much. Is it mainly due to the fact that for optimized sound, you have separate cabinets for each speaker which can then be moved independently in your space to tune in the desired sound? I am not very knowledgeable about the science of sound so some of the ideas fly over my head. I am an industrial designer by trade so my eyes are very critical but my hearing isn’t as sharp. I’m trying to create a solution that will feel more modern and sleek which will fit in our environment better. If the sound quality is going to be reduced by a lot then maybe I need to force myself into creating three separate cabinets where the left and right can be more vertical, like most people build. If other members think the bar concept is doable with minimal reduction to sound quality then that would def be my preferred direction. The area where the entertainment system sits is limited so a speaker that sits closer to the wall helps traffic flow in front of it.

      • #5
        Most of the time, the closer you can get the woofer pairs together, the better.

        Assuming you're building with 2woofers per tweeter:
        If you're building a 2way crossover I think you'll have better results staying MTM and trying to crossover lower...treating the crossover like the woofers are a single 6-10inch driver instead of two 3-5inch drivers, because the woofer pairs can sort of "beam" at higher mid-frequencies. Crossing a little lower, like you would with a tweeter meeting a larger woofer, will help avoid this.
        OR
        Design the crossover like a 2.5way and try your hardest to get the tweeter centered/above the midwoofer that's meeting it up in the higher mid-frequencies. The 2.5way crossover will avoid the "beaming" issues of two side-by-side woofers playing the higher mid-frequencies together...and having the tweeter as close to centered/above the midwoofer that's meeting it and playing the higher mids will help avoid a drop in volume around the crossover point for listeners who the speakers aren't pointed directly toward (which is everybody with at least one or two of those speaker sets).


        Also, make sure whatever woofer combination you're choosing will end up as an 8ohm load. Don't accidentally select an MTM or TMM design that uses two 8ohm woofers in parallel, resulting a 4ohm load for the L/C/R which your amplifier won't like.
        My first 2way build

        Comment


        • eavo44
          eavo44 commented
          Editing a comment
          So if I understand correctly, your preference would lean towards a mtm, mtm, and mtm setup? Mr. Carmody suggested that a tm or tmm may give me less comb filtering. I had to look that up and read it several times to make a little sense out of it…lol. But I understand some of the basics of comb filtering now. I plan to purchase 3 kits and combine them in a single cabinet so I hopefully I can avoid any xo modifications…above my know how. Aligning the tweeters on a higher horizontal plane than the mids will avoid beaming? I suppose this is what pushes a vertical setup for speakers in general is to allow for tweeter to tweeter meshing and the same for the mids? Very good point you mentioned about running a mtm or a tmm with 8 ohm woofers in parallel…I’ll keep that in mind. If I decided on a mtm or tmm what descriptive term am I looking for that will keep both mids running on 8 ohms? Thanks.

      • #6
        Three of these in a soundbar configuration would be ideal, IMO. 4" coaxials. Front ported, or sealed like the original designed center channel unit. I crossed my ported pair at 80 hz in a 2.1 situation. No comb filtering, precise imaging. At least as capable as the Overnight sensation. IMO of course. Inexpensive design, 4 piece crossover. Great first project. IMO of course.

        The box drawing shows 1/2" mat'l, that's what i used. Overnight Sensation kit flat packs use 1/2" mat'l.

        If I were making a soundbar, I would use this driver. The three designs other than the Overnight Sensations you mention in post #1 would put you over budget. This would be way under budget. I've built the Overnight Sensations, Sopranos and Continuums but not the Swopes.

        Of course, three discrete boxes would have their own charm, and be flexible for different placements in some future scenario.

        https://techtalk.parts-express.com/f...0-8-easy-build

        https://www.parts-express.com/Dayton...-8-Ohm-295-384
        Last edited by djg; 04-05-2022, 04:27 PM.

        Comment


        • eavo44
          eavo44 commented
          Editing a comment
          Thanks djg…That’s a cool idea…a simple bar with only three speakers would look clean. I’ll keep that in mind. I have this vision of multiple drivers but def open to other ideas. I’m flexible on the budget, so $600 or under should be good. The bar could be three separate forms that link together also…so they could be used in different placements down the road as you mentioned.

      • #7
        Originally posted by eavo44 View Post
        So if I understand correctly, your preference would lean towards a mtm, mtm, and mtm setup? Mr. Carmody suggested that a tm or tmm may give me less comb filtering.
        I agree that TM could be more ideal than TMM or MTM (assuming the single woofer/speaker gets loud enough for your needs), particularly if you can get the tweeter nearer the top/center of the woofer instead of beside it.

        A lower crossover point and keeping the woofers close together will also avoid comb-filtering in an MTM or TMM 2way, while a 2.5way will inherently avoid comb-filtering by having one of the woofers only playing bass+LowMids so it doesn't comb with the other midwoofer.
        Comb-filtering is more of a problem at higher and higher frequencies and more of a problem with larger and/or farther apart drivers (playing the same higher frequencies). You can avoid comb-filtering by keeping the drivers' centers closer together and crossing lower, and/or using a 2.5way crossover which avoids the two woofers overlapping except at lower frequencies where combing isn't a problem.


        The MTM/MTM/MTM suggestion is specifically IF you'll need multiple woofers per tweeter to reach the loudness you want, and IF the chosen tweeter can safely cross low enough to treat the woofer pairs like a single larger driver (aka, closer to 1500-2000hz instead of 2500-3000hz).

        I think TMM or MTM could work ~equally well if the design/crossover is 2.5way instead of 2way.
        I also thiiiink a TMM with the tweeter centered above the midwoofer would have an advantage over almost any design that forces you to squish the tweeter down toward the side of the woofer/s for height limit reasons....AKA, so I think a 2.5way TMM could have an advantage over a TM that needs a larger woofer to reach the same loudness IF the extra tallness means you'd have to move the tweeter down/sideways while the smaller woofers of a TMM would let you keep the tweeter over-top.


        Sorry about repeating the same things over and over again in slightly different ways. I'm hoping maybe one or two of those explanations will make as much sense as they seem to inside my head, lol.
        My first 2way build

        Comment


        • #8
          As I continue to do research I’m liking the idea of going for a kit with a little more output than the OS. The living room is a decent size and it open to a 12’x12’ kitchen and we’ll turn up the tunes while we’re cooking. The kits that appear to be a step up from these are:
          1_Sopranos
          2_S2000’s Is this the same design as the OS with diff drivers?
          3_swope
          4_c notes
          Seems like there are supply issues with the swope’s and the S2000’s? Do we see these becoming available again soon or should I just look at other options? The c notes are only slightly larger and it sounds like there is a center channel that’s currently being designed?

          Comment


          • #9
            There was a recent design named The Transformers which consisted of three separate cabinets, L C R, which could easily be combined into one. The drivers used were the inexpensive TCP115 and ND20
            https://techtalk.parts-express.com/f...ormer-soundbar

            Comment


            • eavo44
              eavo44 commented
              Editing a comment
              This is looking good too…how was the performance?

            • randyohoh
              randyohoh commented
              Editing a comment
              I don't remember seeing any comments on the sound quality of the Transformers. There is also an older (2016?) t-m design on this forum using these drivers and a simple series crossover with very good comments from members of this forum. I believe it was in a contest.

          • #10
            Usually speakers (aside from coaxials like djg mentioned) will have the tweeter above/below the midwoofer. This above/below design usually means there will be a dip in the mids if the listeners are far above/below where the speaker points, but most people don't have stadium-style seating in their houses, so this isn't a huge issue.
            This above/below design helps keep the sound pretty similar for all listeners even if they're pretty far sideways from where the speaker points, so this is nice for wide seating and most real-life situations in a house.

            Placing the tweeter beside the woofer/s is basically like laying a normal speaker on its side. Now the dip in mid-frequencies effects most listeners. And the previously wide/horizontal sweetspot is flipped sideways to form a tall/narrow sweetspot that is much less helpful.
            A really careful design can help lessen these mid-frequency dropouts, but it usually still needs a tweeter that can play/crossover extra low AND a smaller tweeter+midwoofer diameter to help them squeeze extra close to each other.

            This stuff isn't the end of the world either way, but it can be the difference between a mediocre design and a nice design..and the difference can often cost $0 if you have the vertical space to build the speaker tall enough to help center the tweeter.

            I think there's also many nice designs with the tweeter offset toward one side, and I'd assume that comes with a similar disadvantage, but I'm also pretty new to this and have a lot to learn.
            My first 2way build

            Comment


            • eavo44
              eavo44 commented
              Editing a comment
              Lout…thanks for that explanation. Describing the sweet spot in that manor makes sense. I’ll play with the proportions of the cabinet to possibly create more height…and try to get the tweeter above the mids.

          • #11
            https://www.parts-express.com/C-Note...inets-300-7140

            https://www.parts-express.com/C-Note...r-Kit-300-7142

            Comment


            • LOUT
              LOUT commented
              Editing a comment
              I think the Cnote Center is 4ohm while the H&K 2600 AVR/reciever wants 8ohm minimum.

          • #12
            The Tritrix MTM and TM are very good with kits available from PE. The TM is 6 ohms and the MTM is 8 ohms.

            All of the S2000s are 4 ohms.

            Comment


            • #13
              I don't know if your images were to-scale or close, but this is what I'd suggest if there's room.
              Click image for larger version

Name:	Soundbar arrangement.jpg
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ID:	1484816
              My first 2way build

              Comment


              • eavo44
                eavo44 commented
                Editing a comment
                They are to scale for the overnight sensations just to get a look at actual proportions. I am looking into several speaker kits with smallish cabinets. Your sketch could def work! I like the idea of getting the cabinet closer to wall so the taller the cabinet the more flush it should be.. Part of the reason I want to hard mount these speakers is due to our two cats and big dog that like to knock my polks around. Would changing the front baffle in height like this drive the need for a different xo compared to a xo you’d get in a kit? Great images…thanks.

            • #14
              Keep in mind this is just showing a simulation, but this is an example of why it isn't ideal to have a tweeter beside the woofer/s like the Cnote Center and most other 2way MTM designs:

              Their vertical dispersion is kept really nice and together, though there's limited advantages from this.
              Click image for larger version  Name:	Soundbar VituixCAD_Directivity_(ver,_pos_front).jpg Views:	133 Size:	39.0 KB ID:	1484823

              BUT their horizontal dispersion has some noticeable dips for any speakers/listeners outside of their 10-15degree sweetspot.
              Click image for larger version  Name:	Soundbar VituixCAD_Directivity_(hor).jpg Views:	132 Size:	40.9 KB ID:	1484824

              EDIT:
              In defense of some MTM designs (and their designers), I think some were primarily intended to be used upright...not laying on their side.
              Last edited by LOUT; 04-12-2022, 11:43 PM.
              My first 2way build

              Comment


              • #15
                Originally posted by eavo44 View Post
                They are to scale for the overnight sensations just to get a look at actual proportions. I am looking into several speaker kits with smallish cabinets. This could def work! Would changing the front baffle in height like this drive the need for a different xo compared to a xo you’d get in a kit? Great images…thanks.
                The three lower/tweaked versions I posted didn't change the front baffle height nor driver sizes from what you originally posted..just moved the woofers/tweeters around a little.
                But pretty much any changes to the baffle size or shape or driver positions compared to the original design will cause some differences.
                I think the differences of a few db from the baffle changes or driver positions (if ignored by leaving the crossover the same) will likely be smaller than the off-axis dips of the tweeter-beside-woofer options (the lesser of two evils, so to speak) but I think a little tweaking to the crossover could make it a win/win.

                Or, it looks like you have plenty of space between the credenza top and TV bottom to fit traditional TM or TMM speakers in their normal/vertical arrangement. That'd let you order parts and boxes for three matching speakers without needing any tweaks. It looks like you could fit anything around 12-14inches tall or less.
                Is the soundbar asthetic a pretty important part of this?
                My first 2way build

                Comment


                • eavo44
                  eavo44 commented
                  Editing a comment
                  Thanks for all your input and taking the time to share your knowledge. From the beginning I’ve had this vision of a sleek, monoform bar so it has been an important part of this investigation up to this point. Early on it seemed like I would lose a little quality…I was ok with that if it meant I could have the look I wanted. The more I investigate and receive feedback from this forum, it has me thinking it could be a wasted effort. Last thing I want to do is to spend a lot of time, effort, and cash to end up with something that looks good but lacks in performance. When you explained the sweet spot being more vertical vs horizontal with the bar…I can see why this concept isn’t one that’s more popular. I’ll take it back to the drawing board and see how I can create a modern feel with a more traditional speaker layout. I do have a little vertical height I can play with under the tv. Not giving up on the bar 100% yet but I’m going to work on some other solutions for a bit. I do have some vertical room in there to play with and I’m going to design and build another credenza that’s not as wide and somehow can fit the subwoofer. I’ve read this could also be a bad idea so maybe the credenza design can house a diy sub or two…but that’s a discussion for another day. The sub is overlapping the kitchen opening and looks kinda thrown together. I need to get the whole entertainment area streamlined.
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