Blog Forums DIY Speakers and Subwoofers Trying to design my first soundbar

last updated by dameo182 5 months ago
4 voices
42 replies
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    • #25039
      dameo182
      Participant

      It’s been a while since I had the time to think about this project, I’ve been asked to design and build a small soundbar for use above a tv in a static caravan, so the width of the space available is a maximum of 1110mm (just over 43″) and I have a max height of 90mm, so given that, im pondering what the best lay out of the drivers would be. It seems that most soundbars use an MTM layout on each side, I don’t think I have the width to allow for that and also the cost of using 4 woofers and two tweeters is a little high. So would using one woofer and one tweeter on either side be sufficient? I will draw up my design in fusion as soon as I’m able to just so I can get some constructive criticism from people who know better, but I would just like to get the basic layout sorted first.

      As it’s being used for audio from the tv as well as music listening I also wondered if I should aim to raise the FR slightly in the 2-3khz area to try to bring out a bit more clarity in the voices to make films a bit more intelligible, or is that a bad idea?

      I have more questions about this once I’m sure on the basic design, more to do with wiring, which amp to use and how to take the measurements on such a wide speaker etc but I’ll ask those later, thanks

    • #25050
      tvor-ceasar
      Moderator

      What’s the approximate size of the viewing area? I’m guessing it’s rather intimate as its in a static caravan. Also, do you have any idea of the approximate depth you have available? If deep enough, you may be able to fit a 2.1 system in there with a bit of creative ingenuity. Last 2 things, budget for parts and places where you’ll be looking to buy. That way we can make sure we’re all on the same page.

      For a bar with that height, I’d start by looking at something along the lines of the PC-83. It has a really nice full range graph (as full range as a driver that small can go), so you might be able to get away with not needing a tweeter pair.


    • #25056
      dameo182
      Participant

      Yeah I’m really limited on space width and height wise but as for depth the enclosure can be as large as 600mm if needed, I did consider trying to make it a 2.1 system but as its on a quiet caravan site I think the other people on the site would feel some kinda way about bass booming into the night haha. So yeah I think just having a stereo set up would work better. As for the drivers, I’ve used the pc-83 on my surround speakers and I do love them, but unfortunately my overall height of the enclosure has to be under 90mm, so I plan to use the ND65 mated to an ND20fb tweeter, as I’ve used that combination on the speaker in my profile pic and to my ears it sounds great. I actually love how good that little 2.5″ driver sounds, and it’s bass is impressive, I am open to other suggestions though. The main reason I made this thread is because this will be my first soundbar and tbh I dont know much about those designs.

      I apologise for this long reply but this is my thinking on the design, I’ve seen that most bars use an MTM either side, but i was under the impression that MTM horizontally isn’t a good idea for off axis listening, so I’m curious why its used on a bar? Is it because there’s one set of MTM on each side that improves the off axis response? I think ill probably use just a two way on each side, tweeters being furthest apart from each other, does that sound ok or does it really need more drivers? And would it be designed as one enclosure or divided into two separate enclosures?

      • #25059
        123toid
        Keymaster

        The reason MTM’s are used so much on a bar, is the exact reason you are mentioning (space limitations). But you are correct, it is not ideal. That is unless you will be listening directly in front of it (ie no seating on the sides). In general with the size limitations you have, you will probably have dispersion problems, which is one of the reasons I think a BMR driver will be ideal for you.


    • #25057
      dameo182
      Participant

      Oh, also I plan to buy all the parts for this build from sound imports (it’s the only place I’ve found that has what I need and doesn’t take weeks to deliver to the UK) as for budget, it’s basically as cheap as I can make it without giving up too much on sound quality, all my builds so far have cost more on crossover parts than it has on the drivers as I prefer to buy high quality components, I mean if I’m doing something I try to do it to the best of my ability, which usually gets me in trouble with mrs once she sees how much I said it would cost to how much it actually did 🙂

      • #25058
        123toid
        Keymaster

        @dameo182 have you considered using the Tectonic TEBM35C10-4 BMR 2″ Full-Range Speaker? You could obviously go with a bigger driver if you want, but in general I think the BMR technology would be pretty perfect for a soundbar. They have amazing off axis performance (much better than a traditional driver), which, in my opinion is one of the most important factors when designing a soundbar. You could use this as the tweeter part and use something like the ND65-4 for the low end (which is where that really excels). Or if you are up to it, maybe even just use a few of the tectonics and run a small subwoofer. There’s a lot of choices here. I know @elliottdesigns has some strong opinions on the Tectonics, so maybe he can also help if that is the way you want to go.


      • #25077
        Elliott
        Participant

        rscomponents has a few good drivers too, and typically cheaper than soundimports


        Elliott Dyson – Elliott Designs (YouTube) – 3rd year MENG Student
      • #25078
        Elliott
        Participant

        Yeah, I think the BMRs are great, especially if you are on a budget since you can easily cross them over with a gentle slope if choosing a typical crossover point. My personal favourites are the TEBM46C20-4 at the moment, they seem to have the best off-axis performance. Apparently they’re coming out with BMR-k line of drivers at some point though, which are their next gen BMRs which should be fun. If going passive, the best sound quality would be to have plenty of crossover between the two drivers’ frequency range, that way you can do 1st order crossovers which have very minimal phasing issues so off-axis response, vertically, (and therefore power response too) will be much more behaved too, plus a smoother transition between directivities of the two drivers. Honestly, IMO, one of the best builds you can probably do on a tight budget.


        Elliott Dyson – Elliott Designs (YouTube) – 3rd year MENG Student
      • #25223
        123toid
        Keymaster

        That is sweet. I hope they come out sooner than later. But I am not holding my breath with the delays of new products coming out. Hopefully they do though.


    • #25069
      dameo182
      Participant

      @123toid when you day dispersion problems, how do you mean? Is it due to the distance between the drivers being limited by the width of the soundbar?

      This is the first time I’ve heard of the BMR drivers, I do like the look of them, but I assumed that I would have to use a small tweeter for the highs to reduce beaming, so does that mean that the 2″ drivers technology will allow it to beam at a higher frequency than an equivalently sized normal driver does? I think for the woofer I will use the ND65 simply because I really like that drivers bass for such a small unit, but I’m really not 100% set on anything yet, I’m finding it hard to make a decision for some reason. Maybe once I’ve got it drawn up in a few designs I can post them on here and get everyone’s opinion on which will work the best? Luckily the people who have asked for this are in no rush for it.

      • #25070
        123toid
        Keymaster

        @dameo182 You hit the nail on the head. One of the advantages of the BMR technology is that you get excellent off axis response. It gives you a much better off axis response than you would receive from a normal 3/4″ tweeter. Which will allow you to hear voices much better off axis. Here is a good article from the company explaining the technology.

        By the way, I understand thinking about a few designs before you commit. Feel free to post them and we can take a look.


    • #25071
      dameo182
      Participant

      @123toid thanks for the article, they seem almost too good to be true 😄 but yeah I’m going to try using those, the people I’m making this sound bar for are in there 60’s so if these little drivers can help them hear the voices coming from the tv better then I’m all for them.

      When I get to the measuring part of this design, is it using the normal method of 16″ from the tweeter?

      Using just one set of drivers to get the z offset etc, then adding a matching crossover to the other side of the bar. Or are they taken from the centre of the bar from further away than 16″? What has thrown me is theres two sets of drivers a fair distance apart so thinking about where I would measure its response from to create the crossover has thrown me into new territory 😄

      • #25074
        123toid
        Keymaster

        The first is the typical way to do it. Measure, get the z-offset and then replicate it on the other side. Think of it as two different (left and right) speakers, just connected in this instance. So you will design it as such.


      • #25076
        123toid
        Keymaster

        @dameo182 I think you are right though, a lot of people don’t know about BMR technology. I think part of it has to do with the fact that they are such limited sizes.


      • #25079
        Elliott
        Participant

        @123toid Honestly, I think it has to do with quite a few things. People think because its full range you won’t get any good high-frequency content out of it, also, sensitivity isn’t the best on paper, but IRL (particularly small to medium rooms) is much better than it is rated due to the low directivity, that, and people just like to stick to what they know, BMRs are very new and certainly not mainstream in DIY. The closet you have is the Philharmonic BMR, and they don’t even utilise the BMR in the way it is intended (full range), so people end up not really seeing the benefits I think. I mean they aren’t the be-all and end-all, but probably the best drivers you can get for the price (best value).


        Elliott Dyson – Elliott Designs (YouTube) – 3rd year MENG Student
      • #25080
        Elliott
        Participant

        As Nick said in reply to your previous comment, drawings or pictures really help in our understanding of what you are trying to achieve and will help us help you better! 😉


        Elliott Dyson – Elliott Designs (YouTube) – 3rd year MENG Student
    • #25084
      dameo182
      Participant

      Thank you for all the info everyone’s giving me on this subject, I literally only have experience building MTM (2 designs completed) and a small pair of two way speakers that I spent a lot of money on to get to a flat response due to a bad choice in woofer, maybe some of you remember them from the post I made a few months back. But yeah I feel a little more confident about the build now, so I’ll try to get my thoughts down onto a fusion drawing asap and post it on here for critique, I’m also trying to renovate my house for a sale too so I apologise if I can’t get it done in the next few days.

    • #25096
      dameo182
      Participant

      Can someone please do a quick check for me in winisd, I’ve input the perimeters for the 8ohm version of the ND65 and I’m confused by the f3 it is giving me, although the driver database says the integrity checks of the values I input are ok I kind of don’t believe it. It says my f3, for 2 drivers, vented and chebychev is only 73hz where as the same design using the 4ohm version has 50hz f3. I must be missing something?

      • #25098
        tvor-ceasar
        Moderator

        Basically it’s the function of the Qts and the Fs, both of which are vastly different from 8 ohm to 4 ohm. That explains why you get the big difference in F3. In my calcs I get an F3 of 70 for the 8 ohm and 46.5 for the 4 ohm – optimum.


    • #25101
      dameo182
      Participant

      @tvor-ceasar thanks for explaining that, I’ve never input an 8ohm and a 4ohm of the same driver before so I hadn’t realised it would change the f3 so much. This leads me into another question, since the 8ohm version gives me 73hz f3, when they are wired together in parallel and they become 4ohm does that mean they will have the same f3 as the 4ohm version, and vice versa for using 4ohm drives in series? I’m sat here trying to decide if that is a stupid question or not 😄 I can’t decide so I’ll leave it in anyway.

      What was your box volume and tuning frequency to get the 46hz? I could get to 50hz by messing a bit with them but my graph started to look a bit too lumpy if I tried to take it lower, granted I am still learning what the graph should look like for the best results though.

      • #25108
        tvor-ceasar
        Moderator

        No, it does not. The Fs and Qts stay the same, just the Vas changes depending on how you configure things. I suggest you take a few minutes and go to Hexibase’s YT channel and look for “T/S Parameters Explained” (a 2 part series), currently 3 years ago, so 2019. He does an extremely thorough job of showing how everything is derived, with equations and ultimately charts, making it easy for inquiring minds to understand. I have screenshots, but I would rather people watch his videos for all the nuances he adds.

        As for the boxes, I used my QuickBASIC programs that were adapted from a series of articles in Popular Electronics by William R. Hoffman in the 90’s. They usually come up the same as WinISD’s defaults. I like them because I can input the parameters in less than 10 seconds and be at an idea that quick. I’ll have to rerun them later to get the box sizes, but they were very small.


    • #25103
      dameo182
      Participant

    • #25104
      dameo182
      Participant

      So above is a quick render I did of the unit that will house this soundbar, it can’t go below the tv since they have it on a stand, I will try to get them to wall mound the tv to allow it to be a standard type soundbar but I’m not sure they’ll agree to it. So for now the design will mount in the gap above the tv but flush with the front to try to avoid too much diffraction etc. As I said that gap is 95mm tall and 1110mm long, the depth is actually 300mm not 600 like I mentioned before, I saw my error once I looked at the dims they sent. Once I’ve figured out the volume and design that I need for this bar I can then draw it up and place it into this render to see how it looks.

    • #25109
      dameo182
      Participant

      @tvor-ceasar thank you, I’ll take a look at his video, I’ll go with the 4ohm versions in series for this build then as I want as much bass as possible, once again thanks for clearing that up for me

      Winisd gives me an f3 of 50hz with a box volume of 0.124ft3 and a tuning frequency of 59hz. That’s the best I can get it without the graph dipping in the middle too much.

    • #25121
      dameo182
      Participant

      @tvor-ceasar thanks for going to the trouble of getting that for me, it seems like a good software to have. At least now I know I haven’t done something wrong in winisd when uploading the parameters, so I can finally get started on the design. I would have used your box volumes but as I plan to divide the bar into two cabinets each with a slot port instead of the standard round tube I’ll have to use what I can from winisd, also so that I can check the rear port air velocity.

    • #25123
      dameo182
      Participant

      @tvor-ceasar @123toid You know when I’m doing the enclosure design in winisd and I change the wattage in the signal tab, those drivers are rated at 15watts RMS and since I’ve put two in the enclosure, what should I be adding as the wattage amount? Should it be set to 30? It’s just as I’ve been messing with it it seems impossible to keep the cone excursion below the red line above the tuning frequency unless I drop the power down to around 10-15 watts. I’ve always been unsure about that part when there’s multiple drivers in the enclosure, as I’m not sure how winisd is seeing those two drivers if you understand what I mean.

      • #25127
        tvor-ceasar
        Moderator

        This is the same basic question I posed a while back and no one has had a definitive answer, and I have not been able to sleuth one out from the internet either.

        So, I looked at the impedance graphs when you change the number of drivers in WinISD, I didn’t see the base impedance change as you’d expect it to such as when going in parallel or series. Either way you add the RMS up and the max up to get the composite of each. Now, if you are using the 4 ohm, you would most likely (and should in this case) be wiring in series. That means that for each driver, you are dividing the power by the # of drivers. 2 in series means that at 1 watt, each basically sees 1/2 wattage hence would only move approximately 1/2 the excursion it would at 1 watt each. But then again, you are doubling (at least) the piston area. So it seems that multiple driver scenarios in WinISD are not that easy. Hmmm….


    • #25154
      dameo182
      Participant

      @tvor-ceasar is it really that important though as most of the time people listen at average volumes rather than running the speakers at full tilt? My first build was the surround speakers that you guys helped me with, and as I didn’t know any better at the time I designed that enclosure with just 1watt of power, all 5 speakers have been used daily for 2 years now, sometimes at high volume and digging deep while watching some movies , and I’ve never had a problem with them, I’m still impressed by the sound they produce, so I wonder how it would have changed had I added 50 watts into the power tab instead of leaving it at 1. I admit it has concerned me a little bit though that maybe they are getting damaged and I just can’t hear it?

      • #25155
        tvor-ceasar
        Moderator

        Really, as long as you keep it in the realm of its advertised limits (2 in a pair = 30W RMS, 60W Max) and you don’t hear port noise, you’re ok. And when you think about it, you should be pushing somewhere near 100dB at 30W. That’s loud, and even more so in a Caravan. I think you’ll be alright.

        And just to give you an idea of what you are looking for as a ballpark with (2) ND65 drivers on the faceplate in the same enclosure:
        Inside Box Vol: 0.218 CuFt
        Box & Port Freq.: 58.6 Hz
        -3dB (F3): 46.5 Hz
        1-1/2″ eqiv. round port: 5.3″ long
        or
        2″ eqiv. round port 9.8″ long

        Sorry about the Imperial units, us Yanks are mostly still using them. 😁

        You’ll have to play around with the port size in WinISD to make sure 1st resonance is not too low. I chose those sizes as standard ID pipes we can get here, because a pair of 2-1/2″ drivers is ~ equal to a single 3-1/2″ driver in piston area. Best part is, since you are going with a slot port, you can use whatever size (x-section area) you want, so you are not limited to what you can buy.


    • #25159
      dameo182
      Participant

      Yeah thanks for your reply, it think I’ll add 10 watts to the signal power tab just to give a bit of headroom, but like you say it’s never gonna be run at full wattage. Ill give it another try on winisd and try to get close to your box size etc, and see how it goes. As for the first port resonance, as long as it’s above double the tuning frequency it’s fine right? Or should I try to keep it out of the 2-4khz region as well?

    • #25240
      dameo182
      Participant

      I’ve drawn up the enclosure now, which I will post tomorrow, well at least one design of it, I may change it after some thought as it’s turned out to be quite big due to adding a higher wattage in the signal power, I landed on 15watts in the end just because I’m constantly second guessing my decisions, as I really have no idea how that really works. But because of that the port has to be huge in comparison to using 1 watt.

      Anyhow I have a couple more questions about those BMR drivers ,

      •Does it need its own sealed enclosure even though it’s acting as a tweeter, I plan to cross around 4k, unless I’m advised to change that.

      •Does it also need to be flush mounted to help with diffraction, if not what is the reason that it can be proud of the baffle?

      •Also regarding the cone excursion, after trying to find answers for hours about the ins and outs of adding it into winisd, I found a few comments that every driver should be protected from over excursion under the tuning frequency of the box, to stop damage and distortion, but I have no idea if that is really true and if so how I would even do that?

      I realise I’m asking a lot of questions and I do appoligise for causing you guys to spend time explaining for me but just so you know I really do appreciate any help that you give to me. This little project is showing me once more that I still have a lot to learn!

    • #25260
      dameo182
      Participant

      @tvor-ceasar @123toid

      I’m just posting this image to get your opinions on the design, I’m not sold on the ports being towards the middle, although they with be covered by an inset mesh panel. Haven’t decided on the colour or finish I’ll use yet this is just a quick drawing done to show my idea.

    • #25262
      123toid
      Keymaster

      @dameo182

      I really like it. I might consider rear porting though (depending on location) as you might be able to increase your bass response by gaining off the wall behind it. Overall I think it is a great design. And I really like the idea of crossing over low enough with the Dayton Audio that you won’t have to worry about the off-axis as much as you would with a normal MTM. This is a really great design.


      • #25264
        dameo182
        Participant

        I did consider putting the ports to the rear, but the front baffle is such a large panel that it looked a bit empty without the ports, really I added them to the front for aesthetic reasons and I just hope it doesn’t reduce the bass output too much. I also wasn’t sure about the 4k xover point until your reply so I feel a little better about that now, thanks for giving the design a once over for me.

      • #25275
        123toid
        Keymaster

        @dameo182 I misread the crossover point. I read 400hz not 4khz. Personally the major advantage of the BMR is being able to use a lower crossover point to minimize the MTM effect. I would still try to cross closer to 500hz or below if I could. Or at least try it and see what you think of it.


      • #25277
        dameo182
        Participant

        I’m glad you corrected me 😄 yeah it makes sense, I’ll do that instead, I just assumed it would only be the highest frequencies that had to be sent through the bmr driver and the nd65 would handle the Voices, but that’s the reason I come here for advice 👍

    • #25263
      tvor-ceasar
      Moderator

      I like the look of that. Not too sure how it’ll sound, but I’m sure way better than the TV speakers.

      One thing g that popped into my head was: Have you given any thought to angling the faceplate down toward the seating position? That way you aren’t dealing with off axis sound lobes. With the mounting position and the fact its in a caravan, I’d think the listening position would be at least 30° below the soundbar.

      Just a thought.


      • #25265
        dameo182
        Participant

        What about it makes you wonder how good it will sound? I ask as I want to do the best possible job I can do with this build so if you noticed something that I can improve on it would be a great help. Also I did consider tilting the front baffle downward but I’m hoping (if this turns out to be good enough) to try to sell a couple of these, just to family and friends, and in that situation I would have to redesign the speaker and probably the xover slightly to allow it to be used as a normal soundbar, as far as I am aware most people place them under the tv, I’ve never really been a fan of soundbars so I’m guessing on that though 😄

    • #25266
      tvor-ceasar
      Moderator

      I don’t have much first hand experience with MTM soundbars. Most I’ve used or tried were just single drivers per side.

      For pure frequency reponse, I’m sure they’ll be impressive for their size. And all the regular MTMs I’ve heard have amazing Soundstage. From what I’ve read, the sideways versions become narrow, but there are many from the big companies out there that are this way, so it must be quite usable. Nick ( @123toid ), what’s your further take on them? I know you definitely have experience there.

      As far as tilting the front, I doubt you’d have to change anything. I only thought of it because you’d tend to be higher above the ear with that mounting than you would be below the ear with the under screen mounting. Maybe the sideways lobing will be a benefit in this situation. 🤔


      • #25267
        dameo182
        Participant

        I think the main reason @123toid suggested I use the full range BMR driver as the tweeter is mainly to improve the fact that it’s a horizontal mtm design, those drivers seem to do some sorcery with the sound from how I understand them, and yeah I was considering just putting one woofer and one tweeter on each side, to bring down the cost and because I had heard that mtm horizontally we’re lacking in the off axis. But I went with the MTM design mainly because I wanted better power handling by sharing the load and also after modelling the single woofer enclosure it was way over the xmas limit on the cone excursion and I’m yet to understand why since it’s suppose to handle 15watts rms, I’m sure I’ll figure it out at some point though. I understand it a little better than I did after your input though.

        My reasoning for keeping the baffle level at the front was because I have the height limit, and to keep that height with a pitched baffle I’d have increase the length from top to bottom, I Know its probably only by a few mm but I’m not sure how much you can change the dimensions of a baffle before it changes the response with the designed crossover, so to then make one with a 90° baffle for someone else I thought might mess with the response and need crossover adjustment. I’m probably overthinking it again though 😄 luckily it’s easy to change in fusion at this stage.

      • #25276
        123toid
        Keymaster

        @tvor-ceasar You are absolutely correct about the horizontal MTM. I mentioned the BMR since it has a very wide dispersion pattern (almost 180 degrees). If it were me doing it, I would cross the BMR’s over low (200-500hz range to get the wide dispersion with minimal issues you typically have with a horizontal MTM.

        @dameo182 That is the main reason I suggested the BMR. The high end will definitely be better with this type of build. As I mentioned before, the lower you can cross the BMR’s over the better it’ll sound to all seats.


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