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

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    dameo182
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    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

  • Trying to design my first soundbar

    dameo182 updated 3 days, 1 hour ago 4 Members · 42 Replies
  • tvor-ceasar

    Moderator
    June 14, 2022 at 8:41 pm

    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.


    Trying to design my first soundbar

  • dameo182

    Member
    June 15, 2022 at 11:59 am

    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?

    • 123toid

      Administrator
      June 16, 2022 at 12:35 am

      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.


  • dameo182

    Member
    June 15, 2022 at 12:09 pm

    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 🙂

    • 123toid

      Administrator
      June 16, 2022 at 12:32 am

      @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.


    • elliottdesigns

      Member
      June 17, 2022 at 7:48 am

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

    • elliottdesigns

      Member
      June 17, 2022 at 7:53 am

      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.

    • 123toid

      Administrator
      June 23, 2022 at 4:51 pm

      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.


  • dameo182

    Member
    June 16, 2022 at 11:43 am

    @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.

    • 123toid

      Administrator
      June 16, 2022 at 2:37 pm

      @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.


  • dameo182

    Member
    June 16, 2022 at 4:08 pm

    @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 😄

    • 123toid

      Administrator
      June 17, 2022 at 2:28 am

      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.


    • 123toid

      Administrator
      June 17, 2022 at 2:40 am

      @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.


    • elliottdesigns

      Member
      June 17, 2022 at 7:58 am

      @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).

    • elliottdesigns

      Member
      June 17, 2022 at 8:01 am

      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! 😉

  • dameo182

    Member
    June 17, 2022 at 9:47 am

    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.

  • dameo182

    Member
    June 18, 2022 at 3:38 pm

    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?

    • tvor-ceasar

      Moderator
      June 19, 2022 at 12:23 am

      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.


  • dameo182

    Member
    June 19, 2022 at 5:28 am

    @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.

    • tvor-ceasar

      Moderator
      June 19, 2022 at 12:04 pm

      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.


  • dameo182

    Member
    June 19, 2022 at 7:09 am
  • dameo182

    Member
    June 19, 2022 at 7:21 am

    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.

  • dameo182

    Member
    June 19, 2022 at 12:59 pm

    @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.

    • This reply was modified 1 week, 3 days ago by  dameo182.
  • dameo182

    Member
    June 20, 2022 at 2:22 pm

    @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.

  • dameo182

    Member
    June 20, 2022 at 6:37 pm

    @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.

    • This reply was modified 1 week, 2 days ago by  dameo182.
    • tvor-ceasar

      Moderator
      June 20, 2022 at 8:51 pm

      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….


  • dameo182

    Member
    June 21, 2022 at 6:52 am

    @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?

    • tvor-ceasar

      Moderator
      June 21, 2022 at 7:44 am

      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.


  • dameo182

    Member
    June 21, 2022 at 11:28 am

    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?

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