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Nd91-4 with nd90 passives doesn't go as loud as i wanted to be

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  • #16
    I was going to ask about the TCP115 as an alternative, but I couldn't remember if some ND91 projects were running FullRange instead of 2way (which I don't think the TCP can do). Glad to see the TCP getting mentioned.

    I thought the ND91 could reach ~50hz around 90db (around 20watts, before counting BaffleStep losses) in 1.5-2liters with the right PR (or port), but a PR with lower VAS seems to automatically limit the low end reach quite a lot regardless of added weight or cabinet size...and most of the small PR's seem to have really low VAS.
    Is there any way to increase a PassiveR's VAS?
    My first 2way build

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    • #17
      Originally posted by 3rutu5 View Post
      Chris raises a good point, re enclosure sizing, with mine I ended up increasing the box size and loved the extra thump, but was also using a mono 60w Dayton board...plus I haven't used a DSP, outside of my Qualcomm chip amp and it didn't go well, but think it was due to my step up module. I'm interested in how yours goes mate, that would be cool something so small sounding so loud
      Still not close to what i want LOL, i hope someone have the answer.

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      • #18
        Originally posted by Chris Roemer View Post
        Why do you want to add so much weight (tune so low) that your max output @80-100Hz is down -5dB from the normal PA tuning?
        I can SEE that tuning @50 can increase your output about +4dB AT 50Hz, but you're around -18dB down at that point.
        You've raised your F3 (the way that term's typically used) from 75Hz up to around 110Hz.

        So, your internal box volume (not counting an amp) is pretty close to (the "stock") 0.04 cu.ft.box?
        For ME, a pr. of ND105 PRs models about the same as the ND90s (using the same mass).
        EYE would run those PRs (either set) with much less added mass, like maybe 6g (total) ?
        Hi Chris, at 50 hz i'm at -9db, i'm curious how you get -18db. Also my spl chart says 90db at 50hz while winisd calculate RMS, so peak is at 93db. This is with 40 watt RMS but with 30 watt RMS it should be 1db less, so 89db. I only get around 82db with distortion and 77db without distortion. I have set a low pass at 57hz and highpass at 47 hz, so i should get almost the max spl out of it.

        I have changed the nd90 PR for a simple PR from ebay( only a steel plate with surround ) and attached a magnet to get a 50 hz tuning( did some Rice on the cone and played with the frequencies to know the tuning frequency), its between 48hz and 54hz. Still got the same results, 77db or 82db with distortion. The PR is moving like crazy at 82db and excursion is 1cm or maybe even more. The PR from ebay is around 38 cm2 and with 10mm excursion it should go WAY louder.

        So its not the lack of excursion so the only thing i can think of is that the Passives are canceling each other out OR roomgain but other speakers i have goes louder and if i seal the nd91-4 enclosure( remove passives and seal the enclosure ) i still got 77db from a sealed enclosure, wich winisd calculated the same, so it has to be some cancelation from the passives but i never heard something like that on the parts express forum.. what could it be???

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        • #19
          Are you actually getting 30/40 watts? What amplification are you using? Sorry If I missed it somewhere in the thread. If you play a 50hz tone what is the voltage you're measuring at the output?

          As an example, I've had a cheap Class D "150Watt" per channel pro sound amp on my bench before (band new) that was barely able to muster 9volts at the output without clipping and distortion (given standard audio RCA input @ 2volts) - a mere 20watts into 4ohms. A lot of these cheap class D amps are absolutely rubbish - not worth the raw materials they are made from.

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          • #20
            Originally posted by DeZZar View Post
            Are you actually getting 30/40 watts? What amplification are you using? Sorry If I missed it somewhere in the thread. If you play a 50hz tone what is the voltage you're measuring at the output?

            As an example, I've had a cheap Class D "150Watt" per channel pro sound amp on my bench before (band new) that was barely able to muster 9volts at the output without clipping and distortion (given standard audio RCA input @ 2volts) - a mere 20watts into 4ohms. A lot of these cheap class D amps are absolutely rubbish - not worth the raw materials they are made from.
            I use a dayton audio dspb250 , 50 watt rms x 2. I have a multimeter at home but i don't think it can measure fast enough to give me a precise measurement. The passives are moving around 10mm, so i think they have enough power, maybe even to much. The strange thing is that when i seal the enclosure, i still get around 75db from the sealed nd91-4 driver only. So in other words the passives don't add any spl at all while they are moving like crazy..

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            • 3rutu5
              3rutu5 commented
              Editing a comment
              I might have the sure version of it. Does it have a series of pots on it?

            • Scarface1
              Scarface1 commented
              Editing a comment
              Yes its probably the same as the sure amp but maybe some slight changes. I think i have found what i have been doing wrong. I will explain below..

          • #21
            I could be wrong but I thought I remember something about the design of those (Earlier pre-dsp boards at least) 50x2 boards not really outputting more than the 30x2 units, or maybe that was just on Bluetooth?

            Anywho, I had to high pass my nd-91 / PR setup to prevent issues with unnecessary cone movement. It is a single nd91 with a single 6.5” DS PR. Didn’t have the luxury of dsp so just used some big NPEs.

            Also, trying to make up 9 db @ 50 just to get to where it should be with DSP is killing your headroom and ultimate output potential.

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            • #22
              bcodemz was always trying to get tiny speakers to make bass. Hasn't been here since 4/21.

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              • #23
                Originally posted by Scarface1 View Post
                I have a multimeter at home but i don't think it can measure fast enough to give me a precise measurement.
                that's why you just play a test tone. connect your multimeter to the outputs of the amp, play say a 50hz tone and check what voltage you get.

                Remember most speakers can produce 80-90db with a single watt. So your speakers can be bouncing around a lot but still not be getting a lot of power.

                Other way to test is to connect it up to a real amp instead of these kiosk modules and see what happens.

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                • #24
                  Thanks guys, i think i know what i have doing wrong. First i have a cheap spl meter, the dayton imm-6 wich is probably broken after it felt on the floor from 1 meter. So it measured 9db below the real SPL. Second.. for some reason i tuned my passives at like 65 hz while Winisd predicted 50 hz. So maybe i put a wrong number in it or the Dayton specs are not right( nd105 pr ) but i tried the first passive i used ( peerless 3.5 ) and get more SPL. The reason i replaced the peerless is because it have a 2 db loss because of the low Qms, so with equal loudness contour that is a 3.33 db loss wich is to much for a project wich aims for high SPL.

                  So with winisd i simulated with 65 hz instead of 50 hz and only had to use 27 grams instead of 45 grams. The weight wich comes with the passive is 21.5 grams and i attached a 5 grams ring to it, so 26.5 grams total wich is like the same as the simulated 27 grams winisd added.

                  So Chris Roemer this is probably where the simulated confusion come from, because i think we both simulated different and i think that is because Winisd calculated added mass for 1 passive i guess while i tought it calculated it for both because i put in 2 passives at winisd.
                  Last edited by Scarface1; 09-07-2021, 10:01 AM.

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                  • #25
                    Here is the 65 hz plot with 27 gram added mass. While i knew i had to put 2 times the weight with 2 passives, i tought ofcourse because its 2 passives so 2 weights but probably this means 2 times the weight per 1 passive. So for a 50 hz tuning i had to add 45 gram, so i added 27 gram per passive while it had to be 45 gram per passive!!
                    Attached Files

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                    • #26
                      Originally posted by Scarface1 View Post
                      Here is the 65 hz plot with 27 gram added mass. While i knew i had to put 2 times the weight with 2 passives, i tought ofcourse because its 2 passives so 2 weights but probably this means 2 times the weight per 1 passive. So for a 50 hz tuning i had to add 45 gram, so i added 27 gram per passive while it had to be 45 gram per passive!!
                      I know for me, those peerless passives always modelled weird and put a huge dip in the lower end (in winisd) but the ND90's and ND105s with the included weight's or not we're quite flat and forgiving. Considering I have 4 of the peerless I'd actually like to get them going in a project, but can't find anything that I want to use to match them with ..

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                      • #27
                        Originally posted by 3rutu5 View Post

                        I know for me, those peerless passives always modelled weird and put a huge dip in the lower end (in winisd) but the ND90's and ND105s with the included weight's or not we're quite flat and forgiving. Considering I have 4 of the peerless I'd actually like to get them going in a project, but can't find anything that I want to use to match them with ..
                        Yes they simulated weird. They raised the speaker xmax at tuning frequenty and give a dip in overal low bass, like -2 db. I have to say the peerless sounded a bit cleaner and i like the looks of it, more professional.

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