Boombox Port necessary?

[leontin2001]

Hi!

Update 1: Pardon me, the dimensions are actually, Length 45cm , Height 19.7cm and Depth 26.5 cm . Sorry !

I'm new here and I've scoured for a week or so gathering information about my project. I'm currently set on the dimensions of the cabinet and all of the electronics are ordered and are on the way.

I'd like to apologize beforehand if this is in the wrong section of the forums or if this has already been answered. Sorry!

For anyone out there who would like to replicate my upcoming project here are my parts.

1. Speakers 2x (6.5" or 17cm) Pioneer TS-1746II Full range 4 ohm
(Old car speakers, anything of the like will probably work fine)

2. Amplifier TDA7492P 100W + Bluetooth 4.0 (realistically it's much lower in the 15 W range) Ebay link

3. Battery This was actually kind of hard. You need at least 12v to power the amp so I came up with this configuration: Battery then I bought a splitter to be able to mount the female to the outside of the cabinet for charging the battery and connected one of the males to the amplifier and the other to the battery. Splitter

4. I used MDF 16mm (0.63") thickness, made a cabinet with these dimensions = Length 45cm (17.7"), Height 20cm (7.87") and Depth 26.5cm

Volume of the cabinet should then be 45*20*23 = 20.7 litre or 0.73 cubic feet

I'll be covering the front with black paint and then giving the rest a Walnut wood vinyl cover. I'll also be using a power switch, mount the amplfiier to the top for use of the built in buttons and thereafter install the female DC jack to the back. Then there's the big question, is it necessary with my specifications of the "boombox" to install a port or keep it sealed?

I'm mainly looking to use it for outdoor use, like playing basketball or taking it to a party, if invited of course. ;(

When finished I'll be sure to post some photos

Anyway, thanks for the suggestions,
Kind regards,
Leontin

 

[kevinkr]

Moved from tubes / valves

 

[Khron]

Are you sure this doesn't rather belong in the Subwoofers or Full Range sections, in fact, rather than Class D?

 

[leontin2001]

No one wants to add their hat to the ring? I'd really appreciate some feedback!

 

[vacuphile]

Your question is difficult to answer without further information about the specifications of your speakers. But if you are using run of the mill car speakers and don't have that information, I would go for a sealed enclosure as the safest option. Stuff the enclosure well.

 

[leontin2001]

What kind of information? Sensitivity, volume? I really have no idea what I'm supposed to be providing. According to some chaps my specific speaker needs about 10 litres of volume per driver and the sensitivity is 92db/1w meter. 6.5" // 17cm dual cone. I've made a tube around 17cm with a diameter of 4.2 cm. Would this be optimal?

 

[Sonce]

You need to know Thiele-Small (TS) parameters of the speaker to calculate the box. But, as vacufile pointed out, without TS parameters known, sealed and well stuffed enclosure for car speaker is the best bet. 10 litres box volume is OK.

 

[leontin2001]

Those are unknown, most likely. Where can I find those? The box is 15 litres of volume, and I'm looking for some good bass. Is a sealed enclosure still the best bet?

 

[JMFahey]

IF you know full data, you might design a somewhat better enclosure

IF you do NOT, as is the case, best is a sealed enclosure, rather than a poorly tuned one.

 

[leontin2001]

Is there a significant difference in how the bass is felt between a sealed configuration or a ported one? My high priority with this is the bass, I want it to be felt if possible. I mean, can someone enlighten me with these tuning frequencie? I was given 17cm for a 32hz tuning, I've got no idea if that's what I want or if it's even possible to go that low given my dimensions? I mainly listen to Rock, Pop I'm a big imagine dragons fan and their songs has that punch to it that I want to be felt. Any suggestions or is the sealed enclosure the thing that I should go for?

 

[JMFahey]

Is there a significant difference in how the bass is felt between a sealed configuration or a ported one? My high priority with this is the bass, I want it to be felt if possible. I'm a big imagine dragons fan and their songs has that punch to it that I want to be felt.

Sorry but forget it, don´t keep asking the same question again and again as if somebody could come with a magical solution.
You can´t beat Physics Laws.

You have too small, light and weak speakers, low power, small cabinet , that counts a 3 handicaps.
You should improve all 3 ,even meeting 2 is not enough.

Check in this same Forum area what the Boominator guys are doing.

They get *reasonably good* Bass usng a battery supply like you, but 4 x 10" way heavier speakers in a WAY larger cabinet.
Yes, they do tune their cabinets ... but they use way heavier "serious" speakers where all data is available.

I mean, can someone enlighten me with these tuning frequencie? I was given 17cm for a 32hz tuning,

You believe you´ll get 32Hz chest thumping Bass just by tuning your cabinet that low?
Think again

I´m certain somebody else will be able to suggest some literature on building Bass cabinets; read it.

I've got no idea if that's what I want or if it's even possible to go that low given my dimensions?

You can´t.

 

[leontin2001]

Eye opener, thank you!

Alright, I'll just accept it that it's physically impossible to achieve it given my configuration.

So is it going to sound good or will it be loud for that matter, you have any experience with the TDA7492P amp?

What do I stuff the speaker with? I've got an old pillow with cotton inside, how much would I fill the cabinet with if it's applicable?

I've been reading a lot about the boominator but frankly, it's WAY too large for my purposes. I'm sure I've got no idea what good bass sounds like, my reference is a wall powered Audio Pro Addon T5 which does sound good to me, that's what I'm trying to compare it to, would it be able to sound like that if you've heard it?

Also, I didn't want a magical solution to the question, I just wanted to ensure I'm fully read on what's possible to do with portable speakers that fit my volume. I want the best, don't want to make any stupid mistakes that's all! Sorry

Thanks!

 

[vacuphile]

Leontin, it is never a mistake to start out on the interesting path of building your own speakers. Therefore, I would like to strongly encourage you to go ahead with your project. There is a lot to learn, and a first step to be taken before that can really begin. You are at least willing to learn and dare to ask questions. Keep us posted about your project.

As to stuffing: please keep the pillow for your cat . What works very well is rock wool of glass fiber, the kinds that are used for insulation. Just make sure the fluffy material faces the inside of the enclosure, so not the paper backing.

Have fun!

 

[JMFahey]

Your speaker will sound fine, build it.

 

[leontin2001]

Hey,

I'll upload some photos of it later this weekend on how far it's come, the cabinet per say is already finished. All that's left is awaiting the arrival of the electronics.

Good day!

 

[OffGridKindaGuy]

Just a note..


The battery you have chosen has a current limit circuit built in. Once the draw exceeds ~2 amps, it will shut down. The load will need to be removed and the battery turned off/on for it to reset. Your amp could hit that limit easily at higher volume..


Bass and portable is a holy grail. Simple battery scenarios limit things. I've had better luck designing with a 2.1 amp. (Separate Woofer) I've used this amp with the same battery you have selected..


Mini Hi-Fi 2.1 Class D Audio Amplifier Board 2x15W + 30W


Use 8 ohm L/R drivers and 4 ohm on the sub. Add the pot to the sub connections on the board (You Will Need It) and do the mod (Low Pass Filter) to the trace on the board..


I've built several units with great success. Operates on the battery you have chosen for up to 6 hrs. Larger woofer for more full bass. (I prefer 12" in a sealed enclosure) May not be Bluetooth but that's an easy resolve..


Just a couple pointers. Good Luck!

 

[leontin2001]

Just a note..


The battery you have chosen has a current limit circuit built in. Once the draw exceeds ~2 amps, it will shut down. The load will need to be removed and the battery turned off/on for it to reset. Your amp could hit that limit easily at higher volume..


Bass and portable is a holy grail. Simple battery scenarios limit things. I've had better luck designing with a 2.1 amp. (Separate Woofer) I've used this amp with the same battery you have selected..


Mini Hi-Fi 2.1 Class D Audio Amplifier Board 2x15W + 30W


Use 8 ohm L/R drivers and 4 ohm on the sub. Add the pot to the sub connections on the board (You Will Need It) and do the mod (Low Pass Filter) to the trace on the board..


I've built several units with great success. Operates on the battery you have chosen for up to 6 hrs. Larger woofer for more full bass. (I prefer 12" in a sealed enclosure) May not be Bluetooth but that's an easy resolve..


Just a couple pointers. Good Luck!

Thanks for the information, is this circuit removable? The sole purpose is to have it at nearly full volume. Any other battery you can suggest that doesn't have this limit?

 

[Sonce]

What works very well is rock wool of glass fiber, the kinds that are used for insulation. Just make sure the fluffy material faces the inside of the enclosure, so not the paper backing.

Yes and no. Rock wool or glass fiber is the best indeed, but use that staff without the paper or foil backing! Fill the whole enclosure and as last layer between the wool an the loudspeaker driver place a piece of polyester wadding.

 

[leontin2001]

Just a note..


The battery you have chosen has a current limit circuit built in. Once the draw exceeds ~2 amps, it will shut down. The load will need to be removed and the battery turned off/on for it to reset. Your amp could hit that limit easily at higher volume..


Bass and portable is a holy grail. Simple battery scenarios limit things. I've had better luck designing with a 2.1 amp. (Separate Woofer) I've used this amp with the same battery you have selected..


Mini Hi-Fi 2.1 Class D Audio Amplifier Board 2x15W + 30W


Use 8 ohm L/R drivers and 4 ohm on the sub. Add the pot to the sub connections on the board (You Will Need It) and do the mod (Low Pass Filter) to the trace on the board..


I've built several units with great success. Operates on the battery you have chosen for up to 6 hrs. Larger woofer for more full bass. (I prefer 12" in a sealed enclosure) May not be Bluetooth but that's an easy resolve..


Just a couple pointers. Good Luck!

Thanks for the information, is this circuit removable? The sole purpose is to have it at nearly full volume. Any other battery you can suggest that doesn't have this limit?

 

[OffGridKindaGuy]

I use this type of battery in 12 volt situations where current draw causes issues. They can be easily daisy chained to increase the current draw limit by ~2 amps with every battery added and increase aHr. capacity. The protection for each battery is still there and each battery should be charged individually. (Chargers are usually provided on purchase) If you shop around, you can find larger capacity units of the same configuration..


Long Life 12V Rechargeable Li-po Battery for CCTV Cam 6800mAh #2 | eBay


I wouldn't advise altering the protection circuitry in any LiPo battery. If it doesn't work, find one that will..