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  • speaker eficiency small box

    hi, i want to build a bose soundlink style bluetooth speaker and have bought 4x B&C 2ndf26 because they have a good xmax to dept ratio and can handle a lot of power for a 2 inch speaker. the FS of the speakers are around 165 hz but with a dsp amplifier i can get them to 50 hz (95db). i don't know they are not made for 50hz but if i put them in winisd they recommend a box wich goes to 100hz, so pretty low. i already test them in a box and they sound clean and can handle 50 hz so i want to try them in a small bluetooth speaker. the bluetooth speaker i want to make has a netto volume of 1,1 liter so i have to give them 90 watt RMS. they are rated at 30 watt RMS x4 so they could handle 120 watt RMS. i have a amp that fits and the batteries are enough to get 6 hours out of it.

    Now i have modelled a tangband w3-1876S in that same enclosure and it works twice as eficient at around 50 to 90 hz. the w3 can handle only 15 watt RMS, have more build in dept and only can go to 2000hz wich make it a bit harder to add a small tweeter and it's only 1 driver so i can't get stereo( i know it's not real stereo, but 4 speakers with 25 cm distance between them sound better as one driver in the middle i guess). now the question--> why is this, i know the w3 is build for 50hz so it makes sense, but the energy have to go somewhere. i know all parts of the speaker can affect this but how does this goes. the B&C 2ndf26 goes +- 3 DB less loud but does this mean they wasted half of the power or is the amplifier just working less because of some parameters of the speaker. i don't know if this is possible but they have the same VAS so where is the -3DB come from and where is the energy go to.
    Attached Files

  • #2
    To get near 95dB @ 50Hz (in a closed box) it looks like you'll need +23dB or so (@ 50), and to mod that driver to have an Xmax of 45mm (instead of 3.5mm).
    A quad (in series/parallel) will pick up +6dB, for 4 in .05cf. 4 in 1.1L would need an Xmax rating of 9mm to get near 95dB. This is at 2.5wRMS, not 120, 90, or even 30.

    It LOOKs like if your gain was less excessive (only +12dB @ 100Hz) you could achieve near 95dB (@ 100) w/ 3wRMS and stay within the realm of Xmax limits. They really won't be able to do 50Hz.

    The W3 IS made for 50Hz, can take its rated 15w down to 50Hz, and should yield about 88dB @ 15w. It needs a vented or "PR" cab to do this.

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    • #3
      when you say bose soundlink, what one you using as an example? so far i've found the ND65 models best in that 2 inch range, but still looking at a 0.04 cuft-ish enclosure size, but you are making re think my methods as you could have that W3 firing downwards and something else firing upwards doing that 360 sound. Problem for me would be its too big to be a bose either way im watching this thread as i'm interested in what you are doing

      Comment


      • #4
        Originally posted by Chris Roemer View Post
        To get near 95dB @ 50Hz (in a closed box) it looks like you'll need +23dB or so (@ 50), and to mod that driver to have an Xmax of 45mm (instead of 3.5mm).
        A quad (in series/parallel) will pick up +6dB, for 4 in .05cf. 4 in 1.1L would need an Xmax rating of 9mm to get near 95dB. This is at 2.5wRMS, not 120, 90, or even 30.

        It LOOKs like if your gain was less excessive (only +12dB @ 100Hz) you could achieve near 95dB (@ 100) w/ 3wRMS and stay within the realm of Xmax limits. They really won't be able to do 50Hz.

        The W3 IS made for 50Hz, can take its rated 15w down to 50Hz, and should yield about 88dB @ 15w. It needs a vented or "PR" cab to do this.
        Hi Chris, i use 2 passive radiators and 95 DB at 50 hz schould be possible with 2.2 mm of excursion( speakers have 2.6mm xmax). Everything fits, the amp, speakers, passive radiators and batteries. I use a 1.6 liter enclosure wich left me with 1.1 liter netto

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        • #5
          Originally posted by 3rutu5 View Post
          when you say bose soundlink, what one you using as an example? so far i've found the ND65 models best in that 2 inch range, but still looking at a 0.04 cuft-ish enclosure size, but you are making re think my methods as you could have that W3 firing downwards and something else firing upwards doing that 360 sound. Problem for me would be its too big to be a bose either way im watching this thread as i'm interested in what you are doing
          3rutu5, i use the B&C 2ndf26 and have put them against the nd65-8( nd65-4 maybe is better with less VAS but i already had the nd65-8 in winisd ). they both can get 95DB at 50hz with 90 watt RMS but the 2x nd65 only can take 30 watt RMS and are Xmax limited because there are only 2 of them. you can at 1 or 2 extra but it makes them less efficient at 50 hz. also the nd65 are 45mm deep and the B&C are 33mm deep without surround. this make the diy soundlink 49mm thin with 9mm MDF and a few mm(3mm layer) cut out the MDF. the blue line is the nd65!!!
          Attached Files

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          • #6
            Well, I think one of us is doing some bad modeling ... ?
            I can see a quad of the B&C 2" 2NDF26-8 drivers, in 1.1L (about 0.04cf, net), tuned to around 140Hz, CAN (w/9w RMS) achieve an F3 near 120Hz near 96dB, but @ 50Hz they're down over -30dB ! No?

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            • #7
              Originally posted by 3rutu5 View Post
              when you say bose soundlink, what one you using as an example? so far i've found the ND65 models best in that 2 inch range, but still looking at a 0.04 cuft-ish enclosure size, but you are making re think my methods as you could have that W3 firing downwards and something else firing upwards doing that 360 sound. Problem for me would be its too big to be a bose either way im watching this thread as i'm interested in what you are doing
              i don't know aren't they all the same. i use the soundlink 3 because its the newest version. i will upload a sketch tomorrow of the measurements(build plans)

              Comment


              • #8
                Originally posted by Chris Roemer View Post
                Well, I think one of us is doing some bad modeling ... ?
                I can see a quad of the B&C 2" 2NDF26-8 drivers, in 1.1L (about 0.04cf, net), tuned to around 140Hz, CAN (w/9w RMS) achieve an F3 near 120Hz near 96dB, but @ 50Hz they're down over -30dB ! No?
                i tuned the enclosure to 54 hz and get -18DB but i tried tuning them to 140 hz and get indeed under -30db at 50 hz
                Attached Files

                Comment


                • #9
                  Originally posted by Scarface1 View Post

                  i tuned the enclosure to 54 hz and get -18DB but i tried tuning them to 140 hz and get indeed under -30db at 50 hz
                  http://techtalk.parts-express.com/fo...rinted-project

                  This was the one i was talking about, the audio in the YouTube isnt the best and recorded with a crap phone, but , I used the DA 1*60 watt mono and a ND65-4 with two ND90 PRs,. I can push it pretty hard but does start to distort when pushed too hard, I'd say 12v it's ok, but when you go the 19v you can go louder but probably blow the little thing. I can't remember the size I ended up with but overall it was a tidy smallish unit that sounded pretty nice.

                  I found there were soundlink minis, normals and over variants which were either 0.01cuft in total to 360 degree downwards firing and then larger. I've had a go at a couple of small builds inspired by them, but in the end gave up as I don't have that commerical backing and research to get deep droney bass out of a.1inch driver lol.

                  Comment


                  • #10
                    Originally posted by 3rutu5 View Post

                    http://techtalk.parts-express.com/fo...rinted-project

                    This was the one i was talking about, the audio in the YouTube isnt the best and recorded with a crap phone, but , I used the DA 1*60 watt mono and a ND65-4 with two ND90 PRs,. I can push it pretty hard but does start to distort when pushed too hard, I'd say 12v it's ok, but when you go the 19v you can go louder but probably blow the little thing. I can't remember the size I ended up with but overall it was a tidy smallish unit that sounded pretty nice.

                    I found there were soundlink minis, normals and over variants which were either 0.01cuft in total to 360 degree downwards firing and then larger. I've had a go at a couple of small builds inspired by them, but in the end gave up as I don't have that commerical backing and research to get deep droney bass out of a.1inch driver lol.
                    That looks very nice! A fantom build! The diy soundlink i want to make should go 10db louder and is around the same size i think. I want to use a 4x50 dsp amp, 2 channels for the fullrange and 1 channel for the tweeters. The PR i want to use is 50cm2 and have i hope an xmax of 10mm. They are from aliexpress and have a 10mm tick surround( i have an pr at home with a surround of 7 mm tick and it have an xmax of 7mm) so i hope i can get 7 to 8 mm excursion out of it

                    Comment


                    • #11
                      Originally posted by 3rutu5 View Post

                      http://techtalk.parts-express.com/fo...rinted-project

                      This was the one i was talking about, the audio in the YouTube isnt the best and recorded with a crap phone, but , I used the DA 1*60 watt mono and a ND65-4 with two ND90 PRs,. I can push it pretty hard but does start to distort when pushed too hard, I'd say 12v it's ok, but when you go the 19v you can go louder but probably blow the little thing. I can't remember the size I ended up with but overall it was a tidy smallish unit that sounded pretty nice.

                      I found there were soundlink minis, normals and over variants which were either 0.01cuft in total to 360 degree downwards firing and then larger. I've had a go at a couple of small builds inspired by them, but in the end gave up as I don't have that commerical backing and research to get deep droney bass out of a.1inch driver lol.
                      Again nice build, i watch the video it's a cool little speaker. Why haven't you used a dsp amp so you can tune them how you want..

                      Comment


                      • #12
                        Originally posted by Scarface1 View Post

                        Again nice build, i watch the video it's a cool little speaker. Why haven't you used a dsp amp so you can tune them how you want..
                        I bought that particular amp and then soon after i noticed that there were ones that came out with the in-built dsp I have a 2*50w wondom with dsp I got after that build but happy with the little thing. I did another built years ago where I made a soundlink mini clone and a dsp would have been great in that, if you are bored you can check out the quarantinee thread in the projects folder. It used chinese passives

                        http://techtalk.parts-express.com/fo...aran-teeeeenie

                        also made a.couple of beer can ones that had an aliexpress bt/amp that was low powered but had a customisable CSR chip you could tweak the EQ on, but the contacts are tiny and I would cook the board trying to solder the programming module.

                        http://techtalk.parts-express.com/fo...-speaker-mkiii
                        Last edited by 3rutu5; 03-08-2021, 03:03 AM.

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                        • #13
                          3rutu5, i made a testbox and it's sound very distorted the lower you go. There are a few possibilities why this happen.

                          1. Air leaks
                          2. To much weight on the passive radiator
                          3. No bracing
                          4. The left-under speaker is detached(solder problem)
                          5. It's difficult to know the tuning point and set the highpass filter

                          I already tight the air leaks and the speaker is only playing at
                          -8 db of max limit so maybe it's playing just above xmax at the lowest frequency ( wrong highpass ).

                          And i have to open it up because 1 driver doesn't work, isn't connected but i'm not sure if this will lead to distortion at the moment because it's working as a passive at the moment. It will change the frequency response i guess but thats all, maybe i'm wrong..
                          Attached Files

                          Comment


                          • #14
                            Originally posted by Scarface1 View Post
                            3rutu5, i made a testbox and it's sound very distorted the lower you go. There are a few possibilities why this happen.

                            1. Air leaks
                            2. To much weight on the passive radiator
                            3. No bracing
                            4. The left-under speaker is detached(solder problem)
                            5. It's difficult to know the tuning point and set the highpass filter

                            I already tight the air leaks and the speaker is only playing at
                            -8 db of max limit so maybe it's playing just above xmax at the lowest frequency ( wrong highpass ).

                            And i have to open it up because 1 driver doesn't work, isn't connected but i'm not sure if this will lead to distortion at the moment because it's working as a passive at the moment. It will change the frequency response i guess but thats all, maybe i'm wrong..
                            I completely missed this post, didnt even get a notification....that first photo is deceiving, i thought it was packing a bunch of 3-4 inch woofers on the side under i focused in on those passives. I'm not familar with those drivers, might need to have a looksy, for that size driver have you considered the ND65? the size itself is wrong as the 65mm isnt for the speaker like the others in the range, but in this case it is actually the external dimensions. But as you already have them, i think you are right, air leaks are a killer as you would have glued in those membranes and almost impossible to model them as well as at least with mine there are no TS parameters. My quarentinees have a little sag on them and i glued a few coins on the back and they can go loud enough, but i used 1.5inch drivers. you possibly will be getting a lower DB's as you have 4 drivers in the space that i had two, in a 0.02cuft enclosure, which i separated by 3d printing a L shaped piece. Just talking about loud here, have you considered running only 2 drivers and the two passives in two separate voids? There is a guy on youtube called aukits which sells a kit but has a build video, which started me looking around at a heap of videos similar.

                            Maybe check out the two youtube videos i had in the visaton build and see if yours sounds similar as it is basically the same concept, yours is just bigger and more drivers. I find passives a nightmare to model and use, with my only successful one being the phantom clone.

                            keep on with it though, i want to see how it plays out

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