[prasanth DIYer]

Hi all, i am sharing my experience in building a 100W+100W Boom box for my Home and picnic Audio needs.

Being a audiophile always wanted good sounding speaker with good clarity on notes and sound quality reproduction.

I have done the Enclosure and Electronics wiring as part of my DIY here, i had bought quite some parts from various sources for making this happen.

The Need:
I wanted a Speaker box with full range capabilities and can be transported by car, also with docking table at house to convert has a Music system on my living room.

Definitely wanted a Bluetooth capability as Audio can be streamed wirelessly from TV, phone , PC.

Search for Quality Speakers

The tricky part here is sourcing a Home theater or Hi-Fi speaker is hard, as there is not much of a B2C crowd, as you cannot really find a good quality speakers in Amazon and other regular online retail places.

I was also aware that using a Car Audio speakers for home Audio needs is not a right thing and usually car speakers are tuned for Car environment and its not a Flat response speakers and the coil tuning is done for Current based displacement than voltage based displacement, as cars are usually limited to 12V max , the coils will has less ohms <4ohms, so it can drive more current.

some link here for more understanding >>

youtube

Parameters considered in the build

• Output watts - 100W RMS Left , 100W RMS right ( total 200W RMS)
• Amplifier power supply
• Speaker characteristics
• enclosure volume and port tuning

The Amplifier:
I have considered this particular amplifier for the build as i have good amount of experience with this Chip and its performance, TDA7498



Features:

• High power digital audio amplifier; power supply: DC 15-32V; output power: 100W+100W
• 90% high efficiency; please note that the differential inputs can minimize common-mode noise
• Output impedance 4-8 ohm; Four fixed gain settings available: 25.6 dB, 31.6 dB, 35.1 dB and 37.6 dB
• Output power: 100W+100W (Vcc = 36 V, RL = 6Ω, THD: 10%); Output power: 80W+80W (Vcc = 34 V, RL = 8Ω, THD: 10%)
• With short-circuit protection, over temperature protection; also with standby & mute features on this amp board

Amplifier power supply:

As the Amp can run upto 32V and as its a audio system, i would always go for a isolated power supply which is harder to find but the trick is to use a regular Laptop charger which is ideal and comes with proper cables .

I had used a iball laptop charger 19V, which i had already, but you can pretty much use any between 15V to 32V.

Speaker characteristics

This is a important section as it defines the quality of the speaker and how efficient in terms of reproducing sound close to original signal.
I will not add too many parameters here and try keeping it simple.


Most of us look for speaker watts and maybe Ohms to find the right speaker, but there are few more other specs which defines speaker quality which most of manufactures do not disclose these are called Thiele-Small Parameters

First let me explain basic parameters like watts and ohms,
Watts: This parameter explains the amount of input power it can handle, mostly there will be two types of watts mentioned
1) Rated watts :This is the watts the speaker is designed to run most of the time >90% of time
2) Peak or Max watts: This is the watts the speaker can handle in short bursts without Damaging itself <10% of time.

Ohms: This parameter gives DC resistance between coil terminals, usually this is for matching speakers with amplifiers, Amplifiers come with designed Ohms limit for speakers it can run, and it can also affect output performance of amplifiers if paired properly.

say if your amp can run 4ohms speakers, you can run a 4ohm speaker or speaker network, if a amplifier of 4ohm is paired to a 8ohm speaker the amplifier just cannot run the same watts of output over the higher rated ohm speaker, and will lead to distortion , audio quality issues and thermal issues.

The effect is vise versa of 4 ohm speaker is paired with a 8ohm Amplifier.

Did you notice the word Network i mentioned below? what if i say if you are stuck with a 2 no's of 8 ohm speaker with a 4ohm amplifier?
you can basically run two 8 ohm speakers in parallels to convert final two leads to a 4ohm speaker network, which your amplifier can run it seamlessly,
same you can do in series to add ohms.


Speaker Quality parameters:

Q factor of speaker: a unitless number that describes how the speaker's suspension and motor control cone oscillation at its resonant frequency

As your car suspension has a spring and a damper, speaker also has the same, so it has its natural frequency at which it takes less watts but generates maximum sound output (dB)

Natural frequency Fs will be your speakers tuned frequency or center frequency, where other frequencies on other far ends of spectrum will have lower sound output or less speaker response.

There are 3 Q factors in a speaker to consider while buying, for more detailed please visit here for more understanding.
Qts - toal Quality of speaker
Qes - speakers Electrical quality
Qms - speakers Mechanical quality
Sensitivity - movement or sound producing sensitivity of speaker for less voltage or watts, the average output across the usable frequency when applying 1Watt/1Meter (higher sensitivity speakers produce good treble response)


I will not explain the above terms, as you can visit the link shared for understanding, but will share what is a good value and what is not.

Qts Range :0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications
Qes Range : lower the better
Qms Range : lower the better

both Qms and Qes are resistances in mechanical and electrical side of speaker to produce sound, will help you design the enclosure based on these two parameters. ideally lesser is better.


Enclosure Volume and Tuning:
Every speaker needs a good enclosure for sounding best, the design of enclosure is something highly debated and lot of experts still understanding this, example ideal shape of a speaker is actually a spherical speaker than a cube, due to manufacturing constrains Cubes are much easier.



I had calculated the speaker volume and port based on the some online references, i will leave a link here for your computation

Usually ports are used to tube low frequency response (bass) i had tuned for 50Hz with a 3inch PVC plumbing tube with 150mm length for the enclosure i have used, you need to use enclosure volume to get port diameter and length.





After multiple research i had filtered down to doogesound speakers.
Mid Range -DE525-01 Woofer 5.25" 4Ohms 50 Watts
tweeter - DE15-04 SILK DOME TWEETER 4" 8Ohms 40W
Sub woofer -DE800-01 Woofer 8" 4Ohms 80 Watts
Speaker crossover network - DE80R-07 2 WAY CROSSOVER

If you have good budget and can import speakers look for peerless speakers
They are the best you can find and speaker parameters are out of the world and will provide IMAX level output. you can buy these speakers from DIGIKEY website.

The Design

I had used a CAD software to Generate approximate design and dimensions, as it will be progressive over the build i had chosen to change some design elements over the build time.



As you see i had gone for a retro design with removable legs which can be replaced by trolley wheels for portability.

The Build:

I had purchased 8x4 feet 20mm High density MDF for the build and taken it to a nearby DIY woodworking place for all my wood works

Some videos of working

https://youtu.be/V0Q7wkTBuUg

https://youtu.be/sNjt2Ya6tCI

Photos of build








Bluetooth Module for the build: xcluma MH-M28 Wireless Bluetooth BLT 4.2

I had also considered a APTx CSR8645 Bluetooth module with Mic for calling with buttons for music control, but it comes with dual output which needs two amps for each side of speaker as the output is bridged(4 wire), go gone for MH-M28 for now because my amp accepts single sided output (3 wire input).

I also have used polyester sponge inside the enclosure for increasing enclosure design volume to make it feel like a big speaker.

Cost :
speakers :7k
MDF :2k
Glue and consumables:500rs
DIY garage :1.5k
Elbow grease : 2 days

final look



Final Audio quality and thoughts:

As you might have noticed i had switched once of the 5inch speaker with 8in woofer, this made hell of a difference with Bass and added a full range to the boom box, if you are planning to make it as Front speakers for Home theater, 5inches are fine as that setup had good midrange performance and voice clarity.

My friends who had come over mentioned their Sony boombox worth 25k sounds 50% of what i had made.

Overall very happy with the build and planning to make two more as my home theater front speakers.

I had left it look rustic for now, I will be also adding a lithium pack so it can be made portable, will share pics of insides of speaker box soon with fitment of Amplifier and networks.

I might add in some analogue DB meters for looks.

[bijims]

Great boombox you made for yourself, I appreciate that you took all the effort to build yourself one and it works fantastic it seems.

[null]

I am deaf music wise, so cannot differentiate good vs great here, but have to admit, I have become a fan of your workshop (looking at the pictures).

[tejas.negandhi]

Hi Prashanth,

its an interesting build. Hope you are happy with the build and it sounds as per your expectation.

Well you reminded me of my build which I did sometime back (2018-19). Well my custom build was for an itch which I had to make a portable system from car audio. The output which I had was awesome sounding, customisable, expensive and not so portable.

What I built was a home audio from car audio components -
1. Pioneer 2-din head-unit
2. Focal Performance Speakers 130AS
3. Kicker CompRT 6.75' subwoofer
4. Kenwood compact Amplifier KAC - M3004 (downward firing)

It was an expensive build plus tons of effort behind it. I am not good at carpentry so had to take help of an expert. I found a loose-nut like me and he helped me with the carpentry work and even lent some space in his workshop for my build. It took me around 8 weekends to complete it. Some technical hic-ups which were resolved by discussion on online forums and speaking to Crutchfield experts. Cosmetically, I couldn't make it any better (lacked expertise). If I have to make it again (which I wouldn't) it would look much better aesthetically and sound even more ballistic.

My two cents on the whole experience is -
1. I built a system which can blow away any party (hands down)
2. Its very customizable (just change the Head-unit with latest one and you will have all integrated features
3. Learnt a lot in carpentry, electronics and audio
4. I could have easily bought a Marshal or Bowers and Wilkins and had a beautiful looking system in my living room. But this one is my personal favorite (no one else in family) and is standing tall in my study
5. DO NOT VENTURE INTO IT (unless you have an itch and money)

[prasanth DIYer]

Hey Tejas, thanks for sharing your build. its a interesting one, good that you used car stereo to drive the speakers.

what power supply are you using for DC?

[tejas.negandhi]

I used AC - DC transformer 12V, 20A, 240w

[BudhaBaba]

Hello Tejas,
You took me deep down memory lane with your post and looking at your workshop made me down right envious. Kudos for your build and am sure the thrills accompanying the DIY cannot be expressed in words.
A few clarifications
1) The MDF joints need to be re-inforced to prevent rattles in the long run. What was your solution?
2) No mention of steel wool packing to improve acoustics?
3) Could not find any details pics of the crossover.
You are so right that the larger the diaphragm better the handling of the lows. Large woofers are better at reproducing these longer wavelengths because they can move more air, creating the low-frequency sound waves.

Cheers!

[prasanth DIYer]

Originally Posted by BudhaBaba

Hello Tejas,
You took me deep down memory lane with your post and looking at your workshop made me down right envious. Kudos for your build and am sure the thrills accompanying the DIY cannot be expressed in words.

Hey Budhababa I guess you are referring me, on the workshop photos.

1) The MDF joints need to be reinforced to prevent rattles in the long run. What was your solution?

It did rattle, but i had used fevicol in all the inner edges for tight sealing, and nailed the sheets every 1 inch for better fit.

2) No mention of steel wool packing to improve acoustics?

I had used polyester wool for packing, you can use steel wool too, but its notorious for shorting electrical contacts inside the speaker.

3) Could not find any details pics of the crossover.

please check the link in the top post for the crossover from doogesound website.

[pugram]

A wonderful DIY. I am a technical noob but like good music.

Any idea what the frequency range of this system would be.

And would you be interested in making few more with 'Live to Hear' branding on them. I am from Chennai but would gladly drive the distance to pickup one ��

[prasanth DIYer]

Just incase if any of you all missed adding links for parts used in the build

Links below

Amplifier
https://amzn.in/d/0hjLGiEW

speakers

DE800-01 Woofer 8" 4Ohms 80 Watts - https://www.doogesound.com/products/...67000000065110

DE525-01 Woofer 5.25" 4Ohms 50 Watts - https://www.doogesound.com/products/...67000000025029

DE15-04 SILK DOME TWEETER 4" 8Ohms 40W - https://www.doogesound.com/products/...67000000017154



speaker wires - https://www.doogesound.com/products/...67000000550681

crossover - DE80R-07 2 WAY CROSSOVER - https://www.doogesound.com/products/...67000000017278


Bluetooth module - https://amzn.in/d/05iR4BSd


polyester foam - https://amzn.in/d/08dMLOLL


speaker screws - https://www.doogesound.com/products/...67000000022100


Speaker port - https://www.doogesound.com/products/...67000000022490

[prasanth DIYer]

Originally Posted by pugram

A wonderful DIY. I am a technical noob but like good music.

Any idea what the frequency range of this system would be.

And would you be interested in making few more with 'Live to Hear' branding on them. I am from Chennai but would gladly drive the distance to pickup one ��

The speakers currently producing a good audible response from 25hz to 18khz.

You are welcome to Bangalore to take one if you are interested.

[pugram]

Originally Posted by prasanth DIYer

The speakers currently producing a good audible response from 25hz to 18khz.

You are welcome to Bangalore to take one if you are interested.

Thanks for the offer. I will PM you on this.

On the frequency response, I find most of the soundbars start from 40 to 80hz now a days. My reference point in music systems was a Kenwood Hifi system that I heard few songs in Tamil ( Poove Sempoove, if you know) in the early 90's. Don't remember the model name / number. I am not getting that feel in any of the current budget sound bars out there.

[tejas.negandhi]

@BudhaBaba

I presume the question was for Prashanth. I will still reply to your questions.

1) The MDF joints need to be re-inforced to prevent rattles in the long run. What was your solution?

The MDF joints were joined with wood glue and even with screws. You can see the reminisce of the screws below the black paint. (lacked the expertise to fill the gaps neatly). Once the whole structure was ready, the inside edges were resealed with M-seal like glue to get a perfect seal.

2) No mention of steel wool packing to improve acoustics?

No steel wool was used as the package was quite compact inside. However used the acoustic foam in the subwoofer enclosure as the space was too tight for a 6.75' subwoofer. I don't remember the brand of acoustic foam and it came free with the Kicker Subwoofer.

3) Could not find any details pics of the crossover.

The crossover used was the one which came with Focal speakers. I will opening the speaker to replace the dead battery. I will show the insides of the package when I open it.


I was kind of sure that Focal speakers alone were enough for making a great speaker and I was not getting a compact subwoofer (as the main condition was using only car speakers, amp and player). However, I always wanted to get that extra low-end punch and the search was on. Finally stumbled across the Kicker subwoofer. In case, I didn't add the downward firing sub, the overall speaker would be 4' shorter and 2'-3' narrower.

[Prowler]

Congratulations for your Nice DIY Boom Box.
A couple of questions: 1. Your TDA7498 can deliver 100 W rms + 100 W rms into the load - only when fed with adequate power supply. A laptop brick can never deliver 250 VA. One more crib is it has 10 % total harmonic distortion ( ok for normal usage -but a crime for pure audiophile)

Choice of Sub woofer Speaker: Why restrict your low frequency response to >=40 Hz. Why not 12/15 inch Sub woofers ?

Just a thought.

[prasanth DIYer]

Originally Posted by Prowler

A couple of questions: 1. Your TDA7498 can deliver 100 W rms + 100 W rms into the load - only when fed with adequate power supply. A laptop brick can never deliver 250 VA.

You are right, I'll be adding a meanwell PSU soon with some filters!, The current adaptor is good enough to pump good sound for my living room.

One more crib is it has 10 % total harmonic distortion ( ok for normal usage -but a crime for pure audiophile).

10% THD at 100W, the Amp can do 80W at 1% THD and 0.01@50W. As I am running the amp in 25db gain, noise is pretty much nil for most of the ears.

All amplifiers have ratings for 1% and 10% THD even the audiophile ones! It's the Watts O/P which varies THD from 0 to 10% or more.

Choice of Sub woofer Speaker: Why restrict your low frequency response to >=40 Hz. Why not 12/15 inch Sub woofers ?

Not a big fan of sub 20hz, I get a headache soon, love the Imax 40-inch subs, they are real ones to create proper lows.