A theorized commission: "Bar-Gain"...

[Wolf]

Back in late June, I was commissioned by a coworker to build him a soundbar. Most of his music is via the web or on his phone, so this will likely have a Bluetooth dongle added for that purpose. He and his roommate are/were not exposed to higher quality speaker designs, and have no room for a pair of speakers unless it were to go under the flat screen. He knew I talked a lot of music, and a lot about speakers, and they felt I was a trustworthy person that likely knew what he was doing. He thought it would be cool to have something unique, and likely better than the commercial sticks they pass off as speakers nowadays.

So, I devised a plan for this with some drivers I had around, and tried to keep the drivers' costs down, because he was aware of the cost of the SMSL Q5 Pro that would be the integrated interface for this bar. I gave him a reduced rate on the used 1139 sub I built back in 2004, as I know he'll be happy with it and 'bachelor chic' is pretty much the finish expected here. On to the Bar I went. I found a set of the Dayton PC105-4 midbasses that I acquired within the last year, and looked up the spec sheet. 50W into 4 ohms from the Q5 was a benefit here, the sensitivity of these 4" drivers seemed to be a bit higher than the normal, and an offset TM vs MTM would be cheaper and able to achieve the goals since bars don't require as much BSC. Most bars also have nothing larger than 3" drivers for the slim-sake.

Then I had to find a tweeter to mate well. The guy likes a lot of techno and psy-trance, as well as speed metal, so accurate treble was likely a concern. I found Dayton had a new set of automotive tweeters, both textile and titanium, that would likely suit well with similar sensitivity- and PLUS have an integrated grill for protection from who knows what. I chose the AN25Ti-4 model titanium tweeter pair. His roommate has a small child that is sometimes there, so I felt it best to keep little fingers at bay and that these would suit. I really didn't know what to expect, but they were inexpensive enough to give them a shot.

One of the reasons this was put off a little later, as the Tent Sale was coming up and it was possible to shave off some cost on his end for the SMSL, etc. At the time of this posting, the cab is complete awaiting pieced xover trials, so that will be coming soon....

Gain for high sensitivity, Bar for soundbar, and Bargain for inexpensive. Bar-Gain is very befitting a moniker.

Enough for now, progressive build pics will come later on this evening....

Later,
Wolf

[civit]

What is the name of the dayton tweeter? How does it perform? I'm looking for an inexpensive small tweeter for a bookshelf design.

[Beau]

Have you decided on the Blue LED layout?

I would focus on that first.

[OldBeginner]

Very cool! I am looking forward to seeing what you've come up with. I picked up a Q5 myself with the intention of doing something similar, but I'm only in the very preliminary stage. Likely I'll be using an existing project and just incorporating the SMSL into it, so I'll have a 'soundbar' with a remote. But I will follow this with interest!

[mlau]

If it's a Wolf design, it's a good one

[Wolf]

Have you decided on the Blue LED layout?

I would focus on that first.

If the SMSL has one, it'll have one. Otherwise, Hong will see this as a Bar-Loss.

FWIW, I used the SMSL as the amplifier for the FRD generation, with the bass and treble controls set to 0. This was the only way to ensure this would measure as intended. The influence for using the Q5 came from seeing Scott Sehlin use it in his Helium Soundbar project. It is indeed a wise choice.

Later,
Wolf

[Wolf]

I wanted to make this wunderbar 'under-bar' as simple, low profile, understated, and inexpensive as possible to construct. I managed to use one 2' x 4' (49") 3/4" MDF handipanel, and only a few minor pieces of scrap 3/4" MDF to make the main chassis. My coworker's TV required a 12" x 38" bar top surface, and I was able to get a 12" x 39" bar made from the single board. Within this basic framework, a lot is possible. You could actually make a full 5 channels with the drivers used, and still have room for a pair of dual-opposed 3" ported subwoofers; but an HTR would then be required, and additionally a sub amp to power them all.

More or less- I sliced the board right down the middle lengthwise to make the top/bottom, and then 3x 3" wide boards off the end of each of those 2 boards that would be the internal verticals. 2 to either side of the SMSL, and 2 to either side of the left and right channels at the ends. 3" internal height allowed for the size requirement as well as the low-profile goal. It also allowed the 4" drivers to be screwed to the top and bottom panels for a good mounting. This meant that the baffle needed to be thin to allow the 4" drivers to still breathe easily. I obviously would not be able to scallop the rear of the baffle were I to use a thicker substrate, so this was a necessity. Where needed, 3/4" MDF supports and braces are required to keep the thin material from flexing, resonating, or just actually being too thin in a region wear thicker is required.

So, chassis is figured out. Box alignment time...

This ended up being a bit more difficult than expected. The Fs is higher to yield a higher sensitivity driver, granted, but it also does not like to be used in pretty much anything over 2 liters according to the simulation, because it will unload in both vented and sealed boxes with relatively low power input. An aperiodic looked better to a point, but then still unloaded down low. This is all whilst trying to get some bass response in any shape or form below 100Hz. Since the Fs is 101/102Hz range, this proved to be a difficult balance. I recall having the same bunch of issues when I used the PRV 4MR60-4 in the Synchaeta project, and ultimately went 2 ltrs sealed on those as it was the best compromise. The PRV woofers would take quite a bit power too in this little alignment. These PC105-4 are very similar and likely would be okay in a 2 ltr sealed box as well, but I wanted improvement in the damping of the driver in hopes to get a little more low end. I referenced Jurgen Micka's on-line calculator to try some other types of box designs. You can find his powerful program here:

http://www.micka.de/en/advanced.php

DCR boxes are complicated with 3 ports, and they really had no modeled benefit. So, I tried something not much seen nowadays similar to the MAPD of Northcreek fame. Multi Chamber Aperiodic Damping. I made some assumptions about how many holes in a pegboard panel I could fit in the 2 ltr box with the pb across it diagonally, at 1 liter a piece. Apparently, my math was wrong, and the model did not match the measured impedance I got as a result. Even so- the result I got was a welcome surprise, with a lot more damping of the driver's resonance, and no chance to unload in the 'pretty much' sealed box unlike the Aperiodic box still did.

So- this will likely forever live in infamy as the 'ice-cream-sandwich' dual-chambered-aperiodic box. I used adhesive spray on the pegboard only, and applied the pegboard to either side of the 1" foam. The front piece is full diagonal length, while the rear is 1" shorter in length, and all pieces are full 3" wide. After I applied glue and clamped the lower board and wall supports, I laid glue where the sandwich boards would go, and compressed the foam by about a 0.25" to get it into position. Holding this in place by clamp and shim, I applied the glue to the top of the sandwich boards, added the L-shaped 1" thick foam in the rear chamber, and glued the top-panel on. I did have to clean glue out of some of the holes later, but this was relatively easy to do.

The box is all biscuited construction with MDF and polyurethane glue. The front to rear edges were rounded at a 1" radius. The baffle is black faux-chalkboard vinyl coated MDF from HD. The rest is rolled on Duratex.

Dayton PC105-4 impedances:



Driver in sandwich alignment:


Construction layout:



And an AN25Ti-4 tweeter impedance plot:



More to come...
Wolf

(EDIT: please ignore Vas data on tweeter. Somehow I did not clear the data before I took the sweep.)

[Wolf]

Construction...







And more...
Wolf

[Wolf]

Tweeter is a 1.75" hole. Wrap perimeter with adhesive-backed craft 'foamie', then a layer of Gorilla Tape, and it will press fit into the hole.

Midbass is a 4 1/16" hole, with a 1/8" deep rebate of about 5/32" width. This pincushion frame has a step in it like many older 4" pincushion drivers, and the step is what the gasket is adhered to as well as the surround installed in the recess on the front that is makes. (The Dayton ND105 is one of the few pincushion 4" drivers that do not have this step in the frame.)



And another reason this took a little longer; the dreaded OOPS!!! My experience with 0.25" thick MDF was minimal, and I cut the rebate fine. Then I cut the through hole, and I oblonged what was supposed to be circular when the MDF broke apart and allowed router drift. When I pieced in the replacement, I cut the rebate, and then used the jigsaw to cut the through hole with really good results. Just go slow.



More to come..
Wolf

[Wolf]

Driver spacings:



L-bracket that holds the PSU in place:



Drivers mounted on left side:


Patched right side:



Stay tuned...
Wolf

[Billet]

Looking very good! There is a lot of engineering going into these.

I had to search a little to find info on Multi Chamber Aperiodic Damping, but that is a very interesting concept. I really like the resulting impedance curve.

The "ice cream sandwich" aperiodic vent is very clever also, what an excellent idea. And it really does look like an ice cream sandwich, doesn't it?

Nice work,

Bill

[ernperkins]

Most interesting build I've seen in a while Ben. Bet it will sound great!

[tomzarbo]

Yeah, smaller doesn't mean easier, this thing is complex. This is in the "very interesting" category for me too.
TomZ

[Wolf]

Some notes before I get into the xover measurement and design stage...

-Being that some TVs are heavy, I felt including the 6 vertical uprights was best, as well as the sway-brace inside the front baffle to keep it vertical. The L/R chamber back-walls also help in this regard. The 8 feet prevent sag in the middle of the bar, as well as support the corners. This will therefore support the multiple types of stands that newer TVs include.

-The real wood square-dowel brace in the bottom panel is an absolute must if you have the hole in the bottom cut for access to the amp's rear panel and use MDF for construction. It was literally too weak in the aft half of the center portion that rigidity and strength was sacrificed. The front half by contrast has 1.5" thick upper and lower panels surrounding the SMSL. I later added another vertical brace behind the SMSL PSU to further strengthen the area from top to bottom, and I needed a place to mount the other end of the L-bracket to hold it in place. This vertical rear brace does not fill the entire area, and the cables for input to the SMSL will either pass through the remaining openings, or underneath and in through the bottom access hole.

-I'll just mention that I did a xover sim beforehand for this utilizing spec sheet graphs. Since the design is what it is, it came out much different measuring in situ placed in front of my TV atop my entertainment center. This is just so I mentioned it, but none of the graphics loaded herein on this subject will reflect the initial simulation.

And xover models next up...
Wolf

[Wolf]

As stated above, I setup the Bar-Gain to be atop my entertainment center to take the FR measurements, trying to get the proximity effect added into the responses I took. I also did something really different this time around. I measured at about 10' distance, in about the center of the bar, trying to optimize the off-axis response towards the center position. This placed the Omnimic just above my couch, and the end slightly in front of the backrest.

What surprised me at this point, was that I had to have the Anthem preamp's line-out at -9dB, and the SMSL at 45-50 of a dial that peaks at 60; just to get enough level to take the measurements as I normally do. The noise floor of the SMSL is very noticeable above 50 on the dial. This is likely due to FR/HD measurements normally being taken at a meter and 90-95dB. I wanted to test HD levels as it would likely be utilized, so that I did not exceed the tiny tweeters' comfort zones.

Here is the FR curve of the left channel tweeter, followed by the HD curves of both of them:





You can see that the HD is slightly higher in the right unit over the left one, with the nominal magnitude not really changing much. The FR is also relatively flat but tilted, and the dip in the top octave is actually better than the spec sheet indicates. This may be due to the mounting style I chose. It looks as though 2.5kHz+ is a good recommendation for these little metal boogers, even though the HD is higher on one over the other.

Apparently I did not take a snap of the PC105-4 FR, but only saved the FRD. I will point out that the dips in the range just below 1kHz are likely reflections or BSC blemishes and also not likely to be real. We'll see if they are audible or not. See attached for the AN25Ti-4 Right (higher HD unit) and the midbass FRD.

Xover modeling in the next post...
Wolf
AN25Ti-4_BarGainRight.frd
PC105-4_BarGainLeft.frd