DIY LCR passive sound bar

[LOUT]

If the box/baffle simulation is accurate, it looks like there's even less change than I thought there'd be.
If you didn't already know, raw speakers are usually professionally measured while set on a large (practically infinite) baffle, while the much smaller real-world baffles we all use cause a 3-6db drop in bass and low-mids and usually a slight 1-3db bump in the higher mids. Flip that upsidedown and becomes a handy "target" you can use in simulations if you only have the manufacturer measurements of the drivers on an infinite baffle.

But it looks like they all line-up very similarly:

I think they're all within about 1-2db of eachother.
The different baffle shapes/sizes and driver positions also changes the off-axis baffle responses, which I'm also guessing might be small-ish changes in this situation but still worth mentioning in case I'm totally wrong.?

[mobius]

I think LOUT's 2-way MTM suggestion from post #13 is your best bet. The 2nd woofer will get you an extra 6dB of output over a single driver and when you are talking HT and using 3.5" or 4" drivers, the more SPL output, the better.

I would discard the 2.5-way idea however because first, it would probably mean designing your own xo's which you're not up to but 2nd and more importantly, because in a 2.5-way design, the 2nd woofer (the .5 component) functions to overcome the 6dB of baffle step loss when you wire the 2 woofers in parallel (resulting in a 4ohm speaker usually which also doesn't work here) but in an on-wall application, there actually is no 6dB of baffle step loss.

And I would go with the Sopranos for the following reasons:

1. arguably, they use best quality drivers out of the kits you are looking at
2. they use quite a low xo point, about 1700Hz, which as LOUT explained is advantageous in a sideways MTM configuration
3. the xo design is intended for flexible placement, either out away from the back wall or right up against it
4. and they are designed by the legendary Jeff Bagby. Can't go wrong there.

Now if I was really concerned with high fidelity, I would redesign the xo to account for the different baffle dimensions and driver placements that you are going for as well as the lack of baffle step loss due to the on-wall placement, but since that's not one of your requirements, and because of the way Jeff has designed the xo, you might want to just let your receiver's built-in EQ make up for any significant differences in the frequency responses. I might also consider going sealed on the center module to get rid of the sub 100Hz stuff for possibly more dialogue clarity. That point may be debatable though.

Btw, you should try to do a little reading about room modes and subwoofer and seating placement. Putting the couch right up against the back wall is never a good idea and putting the sub up against the front wall (or a corner) makes things even worse. And is that a window on the back wall? At a minimum, make sure you have some heavy drapes covering such a reflective surface right behind everyone's ears if that's the case.

Jeff's write-up of his Sopranos: Sopranos-Write-up.pdf

And it looks like 3 of the Soprano MTM kits will get you right about to the $600 mark too. Not too shabby.

[eavo44]

The layout of the room is tough… it only has one functional way to place the couch and tv. The door to the left of the tv is the hallway to the three bedrooms. We had to put a door on the hallway entrance to keep the cats from running across my face at night…lol. The area right in front of the entertainment/tv wall is a high traffic area. That is a large window right behind the couch but we do have some thick blackout curtains in place. We could pull the couch away from the wall a bit but it just makes the room feel smaller. I’ve only recently started to educate myself on speaker design and placement. When I got the new sub i started reading up on speakers. I tried the sub crawl and thought the corner, left of the couch, was going to work but I didn’t like it there. You could tell the base was coming from that corner and didn’t feel as integrated as it does to the right of the credenza. Still in the learning stages. My instincts for speaker layout come from my visual preference which unfortunately seems to produce poor sound quality…lol. Want to visually have this bar for lrc but this is starting to sound like a poor design…also want to hide the sub but I’ve read placing your sub in another cabinet can give you poor results…lots to think about. Thanks for your input mobius!

[LOUT]

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.

I've been trying to see what happens with different soundbar options using woofer pairs while keeping a somewhat short-height soundbar.
The 2.5way stuff I've tried with 4inch woofers has some tradeoffs where the low/mid frequencies have more of a drop (around -3-4db) in one direction left/right while the other has a slight ~+1db boost...which probably isn't awful, but I'd prefer the left/right response to be more symetrical if possible.
The 2.5way also looks a little odd unless the tweeter is centered between/above BOTH woofers instead of centered/above the midwoofer in an "L"shape...and being centered above BOTH still wants a pretty low XO to avoid asymmetry around the tweeter/midwoofer crossover.

2way seems to make horizontal symmetry (both appearance AND sound) easier.
The 2way stuff I've tried seems to suggest 4inch woofers really want a super low crossover point (around 1500hz) to the tweeter to avoid beaming or a mid-frequency droop for listeners more than 15-20degrees left/right. And that's with the woofers butted right next to each other. Farther apart (like with the tweeter down between them) makes the crossover want to be even lower to keep the sound nice and flat.
I had much better luck using smaller woofers with a ~90mm outer diameter (including the ND90/ND91/DMA90 woofers that have corners but can still be butted up close on their flatter sides) because this closer Center2Center distance between the two woofers works well with crossovers up around 2000hz which gives more freedom for tweeter selection...opening the door to some of the smaller-diameter tweeters.
This still results in soundbars that are probably taller than some folks might want (around 5.5inches or taller), but it should be possible to make something that reaches ~100db along with bass reaching down to 60-70hz F6 for easy pairing with a subwoofer.

When you compared the two CenterChannel speakers you currently have, I wonder how much of the improvement in sound was because the fancier one plays down into the mid 50's while the other drops off around the 90's for bass. I'd assume both should work okay when paired with a sub (although 90hz is a little high), but the one reaching into the 50's would sound noticeably fuller and nicer if you're trying them alone or without the subwoofer dialed-in.
I'm mostly mentioning it because a lot of really nice dedicated center-channels DON'T have much bass, so they'll sound kind of wimpy without the subwoofer dialed-in. They'll have some nice advantages for staying clean and clear-sounding up really loud, and their sound will stay balanced from different seating positions instead of sounding strange in some seats, BUT their bass won't exist since they'll be relying on the subwoofer...and that lack of bass is an easy first thing you'll probably notice. It might give a real "eww" impression when you first listen to them.

[eavo44]

The larger center I have in the pic is much larger and produces nice sound and base. It’s a much fuller sound than the Polk center…as you’d expected. I’m looking for something in between the old polks and the larger center in both sound and size…puts me in that 4” driver range. It seems like the expected performance of a 2way is sounding positive. I’ll take some time soon to apply your notes of speaker placement. I’ll post some inspiration pics of I found that got me thinking about the bar shape. Thanks again Lout.

[eavo44]

Some images that got me thinking about this bar concept. A few of these where done by a company called Leon…nice looking projects!

[djg]

$200, precise imaging, fits your limited space, my 4" coaxial suggestion seems right to me. I understand difficult and expensive and impressive driver arrays also. Good luck.

[eavo44]

Just took a look at your design…looking nice and clean at the proportions needed. Going to figure out the credenza tonight if I don’t get too tired. Can you attach a pic in a comment? I’ll post below. Do you feel the 3 coaxial speakers will out perform the Polk rm 510?

[djg]

I think the Bobinga 4" coax is a good fit for the limited space available to you. I couldn't comment on the Polks, I've never heard any Polk speakers. Also, if you don't like them, punt them to surround duty. You can't put attachments in comments.

I had 4" S2000 TMs as L/R in my 5.1 setup, 80 hz cross to sub. Perfectly adequate. I only changed because I like building speakers.

[LOUT]

^^^ The coaxial does give you great symmetry (appearance and sound) plus a 4inch driver without the added height of having the tweeter above it...since the tweeter is in-front/inside of the 4inch woofer.
There's also at least one or two designs already using it if you want to use an established crossover design instead of making or finding a crossover design afterward.

The only reason I haven't also been pushing toward it is because the Dayton tweeter measurement has an ugly squiggly-line up high around 45degrees off-axis that makes my eyes angry at the simulation. I'm guessing it's maybe diffraction off the woofer cone, but there's a chance other designs will still end up with similar diffractions and squigglies from it so it's not like the coaxial itself is necessarily any worse than anything else in this regard, AND I'm not sure how noticeable it even is since it's pretty far off-center and up high where hearing isn't as picky and I don't think it's a huge drop.
Basically, I'm being paranoid about something that's probably pretty insignificant AND hypocritical because other parts will likely have a similar issue in real-world measurements.

[djg]

The Bobinga design I linked has a simple 4 element XO. If you want to spend more money, one of PE's boombox designs uses the CX120-8 and has a more elaborate XO. I was impressed with the pair I built to Bobinga's design. I made his center channel concept into a pair of 2.1 satellites. If I hadn't heard them myself I wouldn't be mentioning them twice.

[djg]

3 of these would perform. I built the SR71s, great speaker.

https://techtalk.parts-express.com/f...center-channel

[eavo44]

I bet 3 of those would sound great! The boxes may be a little large but I’ll check it out.

[djg]

These would probably do better on your credenza than off your wall, heavy.

[eavo44]

Hey djg…I applied your design or the Bobinga design to the length of bar I would need. It’s looking promising! I placed the right and left speaker at 4.5” from center to edge…should that dimension stay the same as the original design? The speaker depth is 2.5” so I made the overall depth 4.5” leaving a .25” gap from speaker to inner rear of cabinet. Will spend some more time tonight designing the credenza and bar together. This bar will be the same depth off the wall as the tv which will create the same look as some of the pics I shared last night.

[djg]

I might make it a hair deeper internally, another 1/4". 1/2" thick material is adequate IMO, that may give you some design leeway. 3/4" for the baffle because you are rebating the drivers Bobinga's original was sealed. I think the driver spacing looks good, I made my cabs 5 1/2" wide, 1/4" more than Bobinga's. He really made his as narrow as possible, I assume he had a space crunch, I think 5 1/2" with a small roundover looks better. If I do say so myself.

I didn't delve into volume. If you did port them, porting out the bottom with a 90 degree elbow would be the best looking solution, IMO.

[djg]

RE: 3 Soprano MTMs. The kit calls out two 8 ohm woofers. This would make them 4 ohm speakers. If, as Lout mentioned, your AVR needs 8 ohms loads, could be a problem. Of course you can always upgrade.

[djg]

Sorry, sorry, sorry/

[mobius]

Yes, I'm still a little surprised that a modern AVR by HK won't be happy with 4ohm speakers but that is what it says.

Thanks djg, I had assumed that the Soprano MTM's were using 2 of the same 4ohm drivers as the TM but in series for an 8ohm speaker. My bad. However, it's not that difficult to take the TM design and re-work it for an MTM (this time with the soundbar's proper baffle dimensions and with no baffle step compensation) and get excellent consistency between the old and new speakers in terms of sound quality. I've done that a couple of times with excellent results.

I think what might help the OP at this point is to just refine your requirements a little. So far we have:

- budget: < $400-$600
- an existing design that will work in an on-wall soundbar application
- an 8ohm load for each module
- minimum LF extension to ~80Hz to xo to the sub
- best sound quality possible without sacrificing appearance, includes good off-axis performance
- 50/50 split tv/music
- maximum dimensions --> ??
- maximum SPL at seating position --> ??

It's those last 2 that are still undefined and I think could very much help you narrow down your selection.

To help: I'm with djg on material thickness - I think 1/2" thickness will be fine in this application with 3/4" for the front baffle. When figuring out the minimum cabinet dimensions, I also like to make sure that there is enough space for a 45 degree chamfer around the backside of the driver opening. Also as a general rule, when there is a vented pole piece on the back of the magnet (ie. an opening in the center), you should leave clearance to the back wall at least equivalent to the diameter of the hole. So I would say at least a 1/2" clearance to the back wall with a driver like the Dayton coaxial.

Now a closer look at the Dayton CX120. In a sealed box of about 2-3L, LF extension (F3) is down to about 140Hz. Therefore you'll need to go ported for each module. In a 4.5L ported box with a 1.5" x 4" port (tuned to 80Hz), F3 is ~70Hz and maximum SPL at 1m with a 80Hz HP filter to a sub is about 100dB and will need about 30W*. At about 2.5m away, you'll lose about another 6-8dB, so max SPL in the listening position will now be about 93dB. You'll want about a minimum of 10dB headroom for peak passages which means the basic listening level will now be around about 83dB.

Personally for HT, I want a little more headroom and a little higher SPL in the listening spot but this might work fine for you. Otherwise the dimensions required look good (the sketch pictured in post #23 come pretty close to what you'll need if you change to 1/2" material and fine tune it a little more). The coaxial's off-axis response will probably be the best out of all your driver choices and sound quality should be very good although I still think the Sopranos will be a little better in that department. Now if you wanted more SPL and were willing to go to a larger box, unfortunately, that's out with these drivers because running 2 in parallel will get you a 4ohm speaker.

Any of your other selections should require the tweeters at least somewhat above the woofers for decent off-axis response and so you'll have to go with a taller design. I'm not 100% sure but I think that will probably rule out the Swopes and the Continuums which both use larger woofers (closer to 5" and 6"). With the Overnight Sensations, box dimensions and max SPL look pretty similar to the Daytons except a little more height required. If you wanted more SPL with an MTM version, you're again running into the 4ohm problem.

With the Sopranos TM, you'll need about 4.5L ported tuned to 70Hz with a 1.5" x 4.75" port for an F3 of about 61Hz and with an 80Hz HP filter, you get a maximum SPL of about 103dB at 1m using 60W. So that's a similar size requirements as the Overnight Sensations but probably just a little taller again. Max SPL though has increased.

Now if you wanted more SPL still and were willing to go to a larger box size and you were willing to trust someone to modify the existing design, then with 3 of the Soprano MTM's using 2 of the 4ohm drivers in series, you would need to go up to about 7" in height or so with 1/2" material to accommodate ported versions using about 9L each for the left and right modules but going sealed for the CC module with about 2-3L. Add 6dB to the maximum SPL when using 2 woofers instead of 1, so you're looking at a maximum SPL at 1m now of about 109dB and at your couch of about 102dB or so. So running Soprano MTM's will allow you to get just about twice as loud as with the single Dayton coaxials. (the perception of twice or half as loud happens with a difference of 10dB) F3 with the sealed box is about 100Hz, not exactly reaching down to 80Hz but acceptable for a CC in my experience. Others might take exception to that. Again sound quality wise, I think these are your best bet even with slightly poorer off-axis response compared to the Dayton coaxials.

Hopefully most of that doesn't sound too technical but I ran through it to try to give you an idea of how each of your initial speaker choices stack up against each other in terms of what they are capable of and in terms of what size boxes they need.

*Box calculations are based on manufacture specs and use Unibox. Just in case: Liters = (inches^3/1728) x 28.317 and the box volumes needed are always net volumes, so they exclude the volume of the drivers, the xo, the port, the bracing and anything else solid that goes inside the box. Maximum SPL is determined to be the maximum cone excursion allowed that stays below the xmax of the driver, or in other words the maximum possible excursion that keeps the voice coil within the magnetic gap. Outside of the gap, distortion and compression rise quickly.

[eavo44]

Thanks for the info mobius. I’ll try to answer those last 2 questions as best I can…
_maximum dimensions… I think it depends on the concept I end up going with. If a bar is selected, I’ll post options bellow, then the bar will have a lot of volume to play with. I’ll include options for a standard set of speaker kits that may have more predictable output. I think if I go in this direction then smaller units will be desired. Maybe similar in size to the s2000 or a max height of 12.5”. I used the s2000 design as an example but I just noticed the driver is 4ohm also so I think the s2000’s are out also. Lol.

[eavo44]

- as far as spl I’m not really sure. I looked up the spl for the Polk rm510 and it is labeled as 89db. The older definitive dr7 speakers are labeled at 90db. These are speakers I inherited from my crazy, and mostly deaf, grandfather. I have a hard time understanding how the two have an spl that are so similar. I am definitely wanting more output that the Polk units so maybe somewhere in the 100 db range? Just guessing here really.

[djg]

Again sorry for spreading misinformation.

[mobius]

Sorry, I just realized that the Soprano TM's are a 4ohm speaker so those are out too. doh!

[eavo44]

I’ve been playing around with the options that have been mentioned on the forum for this project. Let me know what you guys think about your preference. I do like the look of options 1 and 2 the best, but I’m open to all these. If option 6 could use an additional set of mid drivers I’m open to that also. Would I be correct to say that any of these bars would need a custom xo due to the change in baffle scale?

[djg]

Personally, if I were making a L/C/R soundbar, I would use the CX120-8 in Bobinga's design. It was meant to be in close proximity to a TV screen, is 8 ohms, and can be sealed or ported. And it's cheap. If I wanted 3 separate boxes, I would build 3 Continuum 2s and mount them on short stands on the credenza away from the wall. IIRC, Mr. Bagby said the Continuum is flexible in placement. It is also 8 ohms.

I love the S2000s, but they weren't really meant for on wall use being rear ported. And they are 4 ohms. Same for the Sopranos

As far as your TM MTM TM picture, the only reason people use a toppled MTM in the middle is lack of space below the TV. If you have L/R TMs, you have room for a center TM.

I'm commenting only on speakers already brought up in this thread.

[djg]

I think a wall mount soundbar looks very nice in your situation. It's a fairly modest approach that works in your confined area. If you aren't happy, it will suffice while you build your dream system.

[eavo44]

‘ It's a fairly modest approach that works in your confined area. If you aren't happy, it will suffice while you build your dream system.” Djg…very good point there!

[Wolf]

Since these have not been mentioned is why I am now, even though they are both 4 ohm designs. Since you wanted more output potential, and if the upgrade path hits you.
My Synchaetas are a 4 ohm TM, originally designed for Minimus7 rehab, but they fit in 2 ltrs sealed and stuffed, and are 86dB sensitivity. They also favor well to being adjacent to a wall without sounding overy chesty.
My BarGain in the Project Gallery on PE's website are another 4 ohm design designed as a sound bar. This would only require the addition of the 3rd channel in the unpopulated center section where the Q5 is placed in my stereo build.

Additionally, you have to be prepared for squeezing in the xovers into the cabinet via a removable panel for ANY soundbar application. They likely will not fit through the driver holes, and can take up some serious real estate. The BarGain shows how I dealt with that problem.

Good luck, you have a lot to sort out...
Wolf

[mobius]

As pictured, options 3 and 4 are probably out because if the TM's are 8ohm that will mean parallel wiring for the MTM's which will be 4ohm and if you choose 4ohm drivers wired in series for the MTM which will be an 8ohm speaker, then the TM's will be 4ohm. Which probably means you need to stick with all TM's or all MTM's across the front.

Of the other options, I prefer the soundbar right up against the wall. If you did go with separate cabinets, I was also thinking that the Continuums would be a great choice, although 3 of them will take you above budget I think.

It struck me in at least 1 of the pics framing out the tv you attached in post #19 that because of the depth of the soundbar, the tv probably needed to be mounted on an extra piece of wood between it and the wall to help keep everything flush. That or an adjustable wall mount.

In terms of max SPL needed, I think there are free SPL meter apps for smartphones. Maybe download 1 of those and then just sit in your listening position and play something at your preferred top volume and then see what the highest SPL reading is.

Just because I suggested it, I went ahead and simmed the CC module of a horizontal Soprano MTM using 2 of the 4ohm drivers wired in series on a 66" x 7" wall mounted soundbar using Jeff's original TM measurements with the baffle diffraction adjusted for the different cabinet dimensions and the lack of baffle step loss to make sure it was viable and it worked out fine. There was no difficulty getting the same summed frequency response as the original TM with just some small changes to the xo values and 1 additional small component on the tweeter. I mention that just so you know that an 8ohm MTM option might still possible.

[eavo44]

I really like the look of the framed in tv, post #19, but Sony tv’s require 4” space around them for proper cooling which didn’t look so great. If I could keep the gap between the tv and frame in the 1” range, similar to pics, then I’d go in that direction. The 4” gap just made the tv look even larger and ate up all the negative space on the wall…ruled that out until I get a bigger house…lol. That’s encouraging that the sopranos are still a possibility. I’ll download one of the spl apps you recommended. Thanks!

[davidroberts]

Forgot about this one. You would need to do some simulation on the impedance as it is technically 4ohm but it may only be in the lower range that will be filtered out by your AVR assuming you are using a sub.

[eavo44]

The first few times I tried this link it wasn’t working right…but it worked today. This looks like a very similar project using only slightly smaller drivers. Interesting how the builder created the sand filled dividers in between the speaker volumes…was wondering if some sound dampening material in those two zones would be advantageous. Thanks for the link.