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Small BT boombox build - help please

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  • Small BT boombox build - help please

    Guys, I'm wanting to do one last build for the time being using some parts I still have and get a few others.

    As I already have the class d amp, I have decided to give this a go.

    The drivers will be
    https://www.parts-express.com/peerle...-ohm--264-1352

    And

    https://www.parts-express.com/peerle...-ohm--264-1600

    The Sim appears to work alright with a ported 0.025cuft per 2inch tuned around that 120hz range and the 0.1ch being the 3.5inch in a ported 0.07cuft at 65-70hz. All look to need a 20mm port around 95mm long. Was thinking the mid range can be downwards firing so it can be hidden, which I believe is fine due.to the low range nature of the driver. These drivers were selected due to the half space sensitivity and they seem to look ok in Winisd.

    My questions area this is a battery powered build and going to be 12v,

    1. , would I need a BSC on any of the channels?

    2. Do I really need to have separate enclosures for.the 3 drivers.

    Not sure if this would be ideal to go down the path of the passive aggressives due to the size of the enclosures and already have 1 of the matched PR's, so would keep an open mind if suggested, but leaning towards the budget alternative of a port at this moment in time


    2.1 Hi-Fi Class D Audio Amplifier Board 2 x 15W + 30W 10-18 VDC

  • #2
    With 2 nd91 you can twice as loud in the same enclosure ( 3.5 peerless) but have to give it 4 times the power. I don't have it but I really like the 26650 battery board from dayton wich you can put a small step down converter between. But you need enough space and I don't know if it's a problem to use 2 drivers in the same enclosure with stereo output from the amp

    Comment


    • #3
      Question 1: I don't know. Question 2: Yes. At least you need to seperate the ".1" from the L/R. You cannot tune one box two ways.

      Comment


      • #4
        Down firing mid-range? I'll let others council your on that.

        You will not get 30 W into the 0.1 channel using a 12 V supply. The amp's ratings are simply it's thermal limitations. Power out is defined by the supply voltage and the speaker impedance. That's electrical physics, no getting around it. A good ROT is W rms = (PSv-1)2 / (2 x SPr). W rms equals power supply voltage -1 squared, divided by 2 x the speaker impedance.

        So at 12 V into a 4 ohm driver you'll get ~15 W rms. Given the Peerless woofer's sensitivity along with some BSC, you won't get much volume out of the sub channel. It won't be able to keep up with the L-R drivers. Each L-R will get the same power as the woofer, are more efficient, and there's two of them.

        Given your initial post, I'd recommend you build a proven DIY design. Like Paul Carmody's Isetta. And think about a larger amp and a 5 S Li-Ion battery module for higher voltage (all sold by PE).

        Comment


        • #5
          Originally posted by Millstonemike View Post
          ...A good ROT is W rms = (PSv-1)2 / (2 x SPr). W rms equals power supply voltage -1 squared, divided by 2 x the speaker impedance.

          So at 12 V into a 4 ohm driver you'll get ~15 W rms.
          Hi Mike, I've been wanting to ask, is the divided by 2 because it is a stereo amp? i.e., is your calculation above 15 W rms for two 4 ohm speakers and if it was a mono amp would to the 12 v power supply provide 30 W rms for one 4 ohm speaker?

          Comment


          • #6
            Originally posted by Millstonemike View Post
            Down firing mid-range? I'll let others council your on that.

            You will not get 30 W into the 0.1 channel using a 12 V supply. The amp's ratings are simply it's thermal limitations. Power out is defined by the supply voltage and the speaker impedance. That's electrical physics, no getting around it. A good ROT is W rms = (PSv-1)2 / (2 x SPr). W rms equals power supply voltage -1 squared, divided by 2 x the speaker impedance.

            So at 12 V into a 4 ohm driver you'll get ~15 W rms. Given the Peerless woofer's sensitivity along with some BSC, you won't get much volume out of the sub channel. It won't be able to keep up with the L-R drivers. Each L-R will get the same power as the woofer, are more efficient, and there's two of them.

            Given your initial post, I'd recommend you build a proven DIY design. Like Paul Carmody's Isetta. And think about a larger amp and a 5 S Li-Ion battery module for higher voltage (all sold by PE).
            i might have lead a stray with the downwards firing part. I'm assuming that if there is a 150hz low pass on the circuit that maybe it isnt classed as a mid range as such. I do have another board which is similar to the ones used in the isetta, where it claims to have 2x50 and 1x100, which also has the BT on it.

            I do like the isetta, but also know im not interested in the physical size of it and would be hacking at a proven design. I wanted something around that 0.1-0.12 cuft max. I do have a spare DTA-2 class t circuit as well, but think i will have the same issue with 2x the 3.5inch peerless and the size box and the 12v option as i would with the 2.1 class D?

            Comment


            • #7
              i must admit when i bought the circuit, i assumed that being in a power supplly of between 10-18v that 12 should be able to easily do it, epecially if the drivers are 4ohm. I never actually made anything using either of the 2.1ch chips i had and they were gathering dust in my garage. My thoughts were as i already have some bigger gear, that i really wanted to push the boundaries and go small and batter powered, whilst still get a bit of a kick to the chest on those lower notes, but reality is you wouldnt be filling a room and not cranking that volume up, that was why i saw that peerless as a nice little gap filler between the 2inch drivers. If that isnt how it works, i guess back tothe drawing board.

              Comment


              • #8
                W/only 1/2 mm! of Xmax, those 2"ers get in trouble below 300Hz (2w limit !).
                Cutting them off even higher would be best (400>500 even?).
                Not much point in porting them.
                Then you can go w/ONE interior space w/some kind of isolation cup behind the little guys.
                Project doesn't SEEM to have much potential - as is (to me).

                Comment


                • #9
                  Originally posted by a4eaudio View Post

                  Hi Mike, I've been wanting to ask, is the divided by 2 because it is a stereo amp? i.e., is your calculation above 15 W rms for two 4 ohm speakers and if it was a mono amp would to the 12 v power supply provide 30 W rms for one 4 ohm speaker?
                  All my statements are "per channel". The "divided by 2" in the power equation is a result of sine wave power calculations with respect to DC chip amps in BTL mode.

                  For each of the channels, L, R or sub, the power out is defined by the supply voltage and the speaker impedance. Since all three drivers are 4 ohm, and the amp has one supply at 12 V, each driver can attain 15 W rms at full volume.

                  As before, that's a mismatch in audio output (i.e., volume) between the sub and the L-R channels. There's 2 L-R drivers and each is more efficient than the sub. And your amp doesn't have the ability to match output levels between the sub and the L-R channels.

                  Comment


                  • #10
                    Originally posted by Chris Roemer View Post
                    W/only 1/2 mm! of Xmax, those 2"ers get in trouble below 300Hz (2w limit !).
                    Cutting them off even higher would be best (400>500 even?).
                    Not much point in porting them.
                    Then you can go w/ONE interior space w/some kind of isolation cup behind the little guys.
                    Project doesn't SEEM to have much potential - as is (to me).
                    Chris brings up other design criteria that's amiss with your plans,

                    I reiterate my recommendation to build a known design. Paul Carmody's "Sprite" and his "Isetta" boomboxes span you initial design.

                    These are links to the Sprite and Isetta designs.

                    Comment


                    • #11
                      "Scrunch, scrunch, scrunch......Jordan!"

                      Shoots plans into nearest bin.....

                      Yeah if Chris says in doesn't have much potential, I'm going to listen, might need to rethink my driver options

                      Comment


                      • #12
                        i havent really thought about it before, but those designs with PR's in the 0.04cuft boxes seem like a proven design that would meet the size requirements, albeit with all the parts may get a bit expensive. Maybe a design using 1x FR driver in each with a 3.5" Peerless PR, I have done some googling and seen the passive aggressives, bantams and heliums, which all seem to have the driver, tweeter deal, which all look awesome, but any floating around that i may not have the name of that use on the 1x driver\PR combo with maybe a BSC? i'm thinking of dropping the sub idea, too hard to get everything into something less than a 0.1cuft total enclosure.

                        Comment


                        • #13
                          While I realize everyone has a different method of accomplishing things and their designs will vary from person to person, I am having a very difficult time with this build. This is no knock on the OP. If you do continue down the road you have chosen, I would highly recommend a HP filter for the 2" drivers as the Xmax is going to run out quickly at 120Hz as you have listed. Also if you do use this method, DEFINITELY put those in a separate sealed chamber from the other LF driver. Just my $0.02

                          I can see a few different methods to accomplish a BT Boombox, but not utilizing the components you have listed. Again not coming down on you 3rutu5

                          I personally built a BT Boombox using full range drivers with a single 2 channel blue tooth amplifier board from Dayton. Dayton also provided the two (2) battery boards I installed within the box.

                          Click image for larger version

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                          Options:
                          1. I would advise using a full range method such as above.
                          2. Use a 2 way method with a dedicated mid range driver and tweeter and passive crossover
                          3. use a 2.1 method utilizing Dayton's new boards they just released: two (2) full range drivers and a small subwoofer
                          4. use a 2.1 method with a 2 way (mid range driver and tweeter and passive crossover) and a separate amp for a small subwoofer.

                          There is no order to the four (4) methods listed above. Those would be my recommendations though. Take it with a grain of salt.

                          "I don't know everything and do not claim to. I continue to learn and that is what makes me human."

                          Comment


                          • #14
                            Originally posted by STIchris722 View Post
                            While I realize everyone has a different method of accomplishing things and their designs will vary from person to person, I am having a very difficult time with this build. This is no knock on the OP. If you do continue down the road you have chosen, I would highly recommend a HP filter for the 2" drivers as the Xmax is going to run out quickly at 120Hz as you have listed. Also if you do use this method, DEFINITELY put those in a separate sealed chamber from the other LF driver. Just my $0.02

                            I can see a few different methods to accomplish a BT Boombox, but not utilizing the components you have listed. Again not coming down on you 3rutu5

                            I personally built a BT Boombox using full range drivers with a single 2 channel blue tooth amplifier board from Dayton. Dayton also provided the two (2) battery boards I installed within the box.

                            Click image for larger version

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ID:	1429831 Click image for larger version

Name:	20180729_165331_resized[5942].jpg
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ID:	1429832

                            Options:
                            1. I would advise using a full range method such as above.
                            2. Use a 2 way method with a dedicated mid range driver and tweeter and passive crossover
                            3. use a 2.1 method utilizing Dayton's new boards they just released: two (2) full range drivers and a small subwoofer
                            4. use a 2.1 method with a 2 way (mid range driver and tweeter and passive crossover) and a separate amp for a small subwoofer.

                            There is no order to the four (4) methods listed above. Those would be my recommendations though. Take it with a grain of salt.
                            Cheers.

                            honestly i have already built something where i used the Dayton v230 board and pretty happy with it. I looked at the battery boards for this build, just havent added it yet.

                            http://techtalk.parts-express.com/fo...3rutu5-boombox

                            A while ago i bought the 2.1 amp and was just going to use it having a go at a 2.1 portable setup, but doesnt really sound like it has enough power to move those drivers @ 12v and the smaller ones cant really model as low as what i thought, so consider this idea tanked. Around the same time i sourced from china 2x 3S BMS a 5v bluetooth receiver board and a voltage step down in anticipation that i was actually going to use the 2.1 as a portable device.

                            I have always been facinated by the tiny setups that can provide a bit of a hit. I just need to keep on reading and having a crack and hopefully one day i come across something that is worth while.

                            thanks for the responses guys, much appreciated.


                            Comment


                            • #15
                              Originally posted by 3rutu5 View Post

                              Cheers.

                              honestly i have already built something where i used the Dayton v230 board and pretty happy with it. I looked at the battery boards for this build, just havent added it yet.

                              http://techtalk.parts-express.com/fo...3rutu5-boombox

                              A while ago i bought the 2.1 amp and was just going to use it having a go at a 2.1 portable setup, but doesnt really sound like it has enough power to move those drivers @ 12v and the smaller ones cant really model as low as what i thought, so consider this idea tanked. Around the same time i sourced from china 2x 3S BMS a 5v bluetooth receiver board and a voltage step down in anticipation that i was actually going to use the 2.1 as a portable device.

                              I have always been facinated by the tiny setups that can provide a bit of a hit. I just need to keep on reading and having a crack and hopefully one day i come across something that is worth while
                              Well you definitely have me beat on your last build! I have always wanted to try the succession of cuts so that the wood can be folded as you did! I really like what you did with that. Hopefully you don't think I was bashing you earlier; I was simply trying to give you some ideas to re-route your current build a little bit. From what I can tell, you know what you are doing, but are rather looking for some input from the community. There is no harm in that by any means. If you don't mind me asking, how did that little guy turn out SQ-wise?

                              I spent some time last evening researching some ideas/parts for your current build, but was striking out with the new Dayton DSP BT boards. They make a 2x50 @4ohms and a 1x100 @4ohms that I believe can link together, but don't play well with a battery board (I believe). There was also something about the boards losing their BT function? I couldn't find all the information on it and @4am my brain stopped working! keep us posted on what you come up with.

                              Cheers,
                              Chris

                              "I don't know everything and do not claim to. I continue to learn and that is what makes me human."

                              Comment

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