A DIY attempt for a TL Sub with some twist

[Lionx]

I would like to share my latest DIY attempt with fellow forum members for valuable suggestions and feedback. This is going to be a long post with multiple stages of my thought process and build.

Some details about my current setup,
TV : Samsung 51” Plasma
AV Receiver : Marantz SR5200
Front : The famous Tritrix TL MTM ( another DIY way back in 2011 with speaker kit from Parts Express). https://www.parts-express.com/project-gallery-speaker-project-tritrix
Center : NAD 808CC
Sources : Pioneer BDP 170, PS3
Projector : Optoma 141HD (Projection on the wall)

I was happy with the way Tritrix was performing but as you must have noticed the absence of a Sub in my current setup which was felt during high action movies. As per the designer, the towers go down till 40Hz and I had confirmed it with a frequency test as well. This would be more than enough for music and most of the movies but the heart pounding thump was missing, more to blame my movie sessions at my friend’s house who was sporting an SVS PB2000.

It all started with this thread (Bolton) where I had asked help of forum members to identify an old Bolton woofer, and there you go; I was thrown in to the world of Open Baffles. I should mention my gratitude to yogibear this time who was always there to answer my silly doubts on or and off the forum. I did make an OB sub with that for my home in Kerala and I was awed by the quality of the bass and the openness. Now I want the same for my Bangalore flat where I spend most of my days due to work.

This was how it was running all these years with my makeshift arrangement of a long shoe rack as TV unit and there is no way I could accommodate a regular sub among that leave alone an OB. The DIYer in me saw an opportunity here, Why not a TV unit with inbuilt sub. I started searching online forums for such a design which took me to this Hideaway Design ##Hideaway TL## which is perfect for my requirements.

This is a TL enclosure based on Quarter wave design which I thought would be a perfect fit for my TL towers.

I started reading about various box design tools and speaker TS parameters but most of those jargons were non-digestive with my limited knowledge in this area. Anyways I have decided on the design so started looking for different components, this is going to be a 100% DIY in its true sense.
The design board had the following elements,

1. A solid woofer 10/12 inch with around 300W RMS 8 Ohms
2. Class D mono amp board
3. LPF board
4. Toroidal Transformer for power duty

The hunt for woofer was the toughest as I didn’t find any promising candidate under 8K except Ahuja but Fs was high where my design wanted something in the range of 30Hz. Drivers in Amazon had mixed reviews and had no TS values, after a frustrating week of online search I decided to scout the local market in Cochin. Sadly none of the shops had the driver I wanted but I met a speaker winder who was ready to make one for me as per my requirement, seeing no other options in vicinity I agreed. The next day I had this in my possession and oh boy it’s a beast.

There you go, 12 inch, double magnet, 400W RMS, 8Ohm woofer and those are the only values me and the winder knows. There go my speaker box design hopes for a toss, it’s impossible without TS values and I was not equipped to find it myself either.



The amp I shortlisted was using TDA8954TH chip which is capable of doing 420W RMS in mono configuration, ordered the same from AliExpress. ##TDA8954##

The filter board is from Eight Audio of Hyd, a 25-250Hz one using TLO72 opamp.##LF Filter##


Regulated power supply for filter board from Eight Audio again. ##Filter Power ##

Transformer was from ebay, 24-0-24 220VA ##Transformer##


Other miscellaneous items were ordered from diyaudiocart.

to be continued ......

 

[arunkvivek]

The bill of materials looks intriguing and your writing has spiced up the suspense...looking forward for your next post.

 

[Aniket]

Interesting project. the woofer looks decently built. But, as visible the voice coil looks like a double layer 2"-3" mid bass, so is the spider, straight from a 12" mid bass driver. expect Fs to be 40hz or more.

I think you hurried a bit while ordering modules and parts. this Class D chip is never going to do 420W with that puny 220VA transformer. you need at least a 500VA transformer with a little higher voltage rating. then it might do 400W, but that too at horrible 10% THD. expect it do 250W clean at max. there are in fact much better discrete Class D amp modules available on Aliexpress based on IRS chips.

Good luck !!

 

[Lionx]

Interesting project. the woofer looks decently built. But, as visible the voice coil looks like a double layer 2"-3" mid bass, so is the spider, straight from a 12" mid bass driver. expect Fs to be 40hz or more.

I think you hurried a bit while ordering modules and parts. this Class D chip is never going to do 420W with that puny 220VA transformer. you need at least a 500VA transformer with a little higher voltage rating. then it might do 400W, but that too at horrible 10% THD. expect it do 250W clean at max. there are in fact much better discrete Class D amp modules available on Aliexpress based on IRS chips.

Good luck !!

May be you are right buddy, I was not really worried about the THD being a Sub amp and I don't expect it to do the claimed 420W either.
What was more important me to have an amp which matches the driver and I got lucky there. I don't have equipments to measure the F/db chart to get the exact values but all I can say is this one goes down to mid 20s in the box which I checked using a frequency analyser app. More about that in my coming post.

 

[Lionx]

Part 2
I was vacationing in Kerala and had enough space and tools to start the wood work, things can get messy if I do it in the flat (experience from my Tritrix build). I had decided to use ¾” MDF for the build and got 2 8x4 sheets and was ready to do the initial cut. Then it occurred to me, I don’t have any measurements for the box neither have an option to design it using any of the tools as driver TS values were unknown. The only way forward was to follow my gut and make the box as per the size availability in my living room. I had noted down the max length/width available between my front speakers and the depth required for the AVR and Center channel, decided to start keeping those as base values. I have taken the dimensions of the original build from the thread and then scaled up as per my requirement keeping the ratios intact, ie Box volume/tunnel volume, wide tunnel volume/tapered volume and box length/tunnel length. Let me tell you all these were guess work and I didn’t have any clue how this going to sound at the end, worst case I would end up with a TV unit with a dummy speaker and I was prepared for that.

Finally, I had all the measurements ready and mapped that to the MDF sheet, started cutting with circular saw and within an hour I had the below jigsaw puzzle.


I test fitted the box to check the edge geometry and necessary sanding was done using agile grinder, the end product looked like below.


Assembled,



Once satisfied with overall fit, I dissembled it for transporting to Bangalore for the final assembly. The driver mount was cut using jigsaw cutter and I almost got a perfect circle.

Back in Bangalore, things were in hibernation for almost 2 weeks then parts started arriving from different parts of the world and I decided to start the assembly. Glued the pieces with Fevicol and screwed together using wood screws, sealed the edges with silicon sealant to arrest any air leaks.



Inside coated with wood primer for durability.


Plate amp build to follow...

 

[Lionx]

Part 3

Plate amp was a straight forward design where I decided to keep the power supply as a separate section to avoid any interference. I was not able to get a plate amp case hence went with usual jugaad, the candidate was an aluminum top case of a cable TV amplifier. It was perfect in size and drilling and cutting was easy being soft metal. I laid out the components and draw the outline for cutting and drilling.

After the initial cut


Testing the connections, please note the filter power supply board was delayed hence I made a temporary one using the components available in the parts bin. It was not a regulated supply and as expected there was hum while powering on.

Plate amp arrangement



The final version of the amplifier.




I cut a small piece for ply and mounted the transformer and filter power supply board and screwed it to the box.


The completed unit fired up for testing.

 

[Lionx]

Time for some cosmetics!!
I started the cosmetic part once everything tested to my satisfaction. I didn’t have any prior experience with fixing mica sheets but I had seen the work during our kitchen renovation and was confident of doing it myself. Got a sheet of mica and started cutting to shape then glued it with Fevicol Heatx, guess I did a pretty neat job for a first timer.



The edges were also covered and the driver mounted.


Fixed the plate amp


Inside of the box with some polyfill, given a thin layer till half of the tunnel also. Note the new power supply board.


The end product.

 

[Lionx]

The Twist !!
Since I have created something which looks like a table why not make it a proper TV unit . Got 12mm tinted glass cut into shape and drilled 4 holes for studs. This being a custom design and an afterthought, no standard size studs were suiting. I got the longest ones available in the local store and extended height by making a base with curtain fixing wood and a piece of ply cut using circular saw bit, painted all thing black to match.



I was a bit worried about the glass fitting where precision is the key, but luckily everything went well and this is the final outcome.



Here it is on the designated place.


Summary of listening experience, I was playing some heavy bass files for testing the sub performance and I heard some cracking sound. Initial suspect was the driver but it was not, turned out to be my bathroom door in the bedroom was shaking and I was like .

Reduced the gain to 50% and everything went back to normal, it produces heart pounding, room filling bass and more importantly without making its presence felt. End of the day I achieved the goal without burning a hole in my pocket and the joy of a successful DIY is just priceless.

Signing off

 

[sadik]

Very well Built ... Keep up the DIY Spirit

 

[Lionx]

Very well Built ... Keep up the DIY Spirit

Thanks brother, it's nothing compared to your builds.

 

[mpw]

Congrats !!

 

[somakmaitra]

The Twist !!
Since I have created something which looks like a table why not make it a proper TV unit . Got 12mm tinted glass cut into shape and drilled 4 holes for studs. This being a custom design and an afterthought, no standard size studs were suiting. I got the longest ones available in the local store and extended height by making a base with curtain fixing wood and a piece of ply cut using circular saw bit, painted all thing black to match.

View attachment 28252

I was a bit worried about the glass fitting where precision is the key, but luckily everything went well and this is the final outcome.

View attachment 28253

Here it is on the designated place.
View attachment 28254

Summary of listening experience, I was playing some heavy bass files for testing the sub performance and I heard some cracking sound. Initial suspect was the driver but it was not, turned out to be my bathroom door in the bedroom was shaking and I was like .

Reduced the gain to 50% and everything went back to normal, it produces heart pounding, room filling bass and more importantly without making its presence felt. End of the day I achieved the goal without burning a hole in my pocket and the joy of a successful DIY is just priceless.

Signing off

Excellent built, what is your impression of the TDA 8954th board? I am planning to buy one.
The wattage is enough for my small room I am pretty impressed with TPA 3116d2.
Regards
Somak

 

[somakmaitra]

There is an option of phase switch in the eight audio board you can put a toggle phase switch .

 

[Lionx]

There is an option of phase switch in the eight audio board you can put a toggle phase switch .

I am aware of that but really didn't see the need for it in real world.

You may go for the TDA amp if it's for Sub, i am not sure about the stereo application as THD seems to be in higher range.

 

[somakmaitra]

I will use itfor my sub as i will save a lot of space . Therr are option for 2.0 with tda8954 but i will go with the TPa 3255 later when I will make a three way with my continuum.

 

[Lionx]

Executing a TL with no TSP of the driver and no TL simulations, can be a hit or miss. The whole plan was guided by the objective of having bass in the setup which can be accommodated in the given space.

The plan was very interesting, and if it sounds as good as it looks and being a DIY, I would say it’s a very high VFM and a great project to have TL bass at very low investment. TL bass is kind of deep, open and omnipresent. It sounds like the bass source is not just the driver cone but all the sides of the enclosure. For HT purpose it can do wonders if it’s a hit.

Aniket, since you are an amp designer and builder, can you suggest better Class D amp modules available on Aliexpress good enough to do sub-bass duty ?

Aniket, I would also like to know a better Class D, may be for the future experiments.

 

[Ravindra Desai]

Good job! DIY Rocks!!
I love the twist!

Regards,

Ravindra.

 

[Aniket]

Stunning, absolutely beautiful build.

some good class D modules:

https://www.aliexpress.com/item/Aiy...7a1c-485a-be3a-6843ca58f7e8&priceBeautifyAB=0



https://www.aliexpress.com/item/IRS...7a1c-485a-be3a-6843ca58f7e8&priceBeautifyAB=0

https://www.aliexpress.com/item/HIF...7a1c-485a-be3a-6843ca58f7e8&priceBeautifyAB=0

https://www.aliexpress.com/item/QUE...rch0604.8.55.24f93131A48lgU&priceBeautifyAB=0


Regards,
Aniket

 

[Krishroy2004]

Great job Lionx,
You are doing wonders.

 

[Lionx]

Thanks everyone for the kind words, it's really motivating to see such comments from the Gurus here.
My idea was to create a sub under 20k which is comparable to high end brands and I think it's very close to my reference sub SVS PB2000. I got lucky with the box dimensions and especially the driver which turned out to be a diamond in the rough.

Next I should finish the front facia of the towers also, may be a 10mm ply for flush mounting of drivers along with grill clothing.