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Do I need a protection capacitor for a full range?

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  • #16
    Without the xo, that looks like a very bright speaker. You are about 2db hot even in your "listening window." Please remember the dispersion of this speaker is freakishly broad and the off axis doesn't drop as much as a normal driver.

    My response was similar to yours below 1.7k and I tried it without the notch -it wasn't good. It's a few $ well spent. You could try a slightly smaller inductor after the notch to roll the top of a tiny bit less if you want. If it's a cost thing, for literally a few $, I can't see a reason not to use the little inductor. The notch is a bit more money, but I'd it was my ears (and it was) I'd use it. It was worth it to me.

    Are you happy with an f3 in the 90's? Box tuning doesnt look bad but I'd probably go a little bigger ( is it really problematic to make it a tiny bit taller) or stuff they enclosure to limit that tuning bump to about 1db, but I don't like big peaks around there- but a little peak will do that driver well.

    No opinion on the 8 vs 4, but the xo values would need to change if you use the 4.

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    • #17
      Difference is likely measurements vs. simulated.
      John H

      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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      • #18
        Originally posted by Adam_M View Post
        Are you happy with an f3 in the 90's? Box tuning doesnt look bad but I'd probably go a little bigger ( is it really problematic to make it a tiny bit taller) or stuff they enclosure to limit that tuning bump to about 1db, but I don't like big peaks around there- but a little peak will do that driver well.

        For me I have to make a compromise because it's a box size issue. I have a small space these need to fit in. It's not ideal, but I don't think I can do anything else in a 1.7L box ?



        Originally posted by Adam_M View Post
        Without the xo, that looks like a very bright speaker. You are about 2db hot even in your "listening window." Please remember the dispersion of this speaker is freakishly broad and the off axis doesn't drop as much as a normal driver.

        My response was similar to yours below 1.7k and I tried it without the notch -it wasn't good. It's a few $ well spent. You could try a slightly smaller inductor after the notch to roll the top of a tiny bit less if you want. If it's a cost thing, for literally a few $, I can't see a reason not to use the little inductor. The notch is a bit more money, but I'd it was my ears (and it was) I'd use it. It was worth it to me.




        I'm not criticizing but I'm just trying to fully understand this notch filter issue. So your saying that a -7 ish dB notch actually was an improvement in your case? Even though my charts show that without a notch it's actually already "notched" by a 1-2 dB ? How wide was your baffle? Note the baffle I'm using is 5.5" so this might explain why my simulations show I don't need it?



        Do you think I could get away with a 0.15 mH inductor https://www.parts-express.com/dayton...-coil--257-022 its 2.7$ to roll off the highs just a tad. A 0.3 mH inductor is half the cost of the driver and they are pretty massive in size.



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        • #19
          Sure, the .15mH coil could work, but it's only going to cut at about 10k and up, where the .3 will cut starting at about 5k (if I've done my math correctly - I didn't sim this - although the impedance up there is pretty flat so this should be semi-accurate). I'd be worried about excessive sillibance with the .15. I'd probably use a 16-18ga inductor, but a 20 isn't the end of the world.

          Regarding the notch, if you look at my raw measurements (last post in my earlier linked thread), you'll see there's a pronounced 5dB peak that needs crushed by the notch. That hump was not pleasant. You'll also see that my notch values are different than jhollander's - although they target the same flaw (and for the record, without measuring equipment, I'd trust John's notch over mine - he's a FAR more accomplished designer than I am) - but note I designed mine to be mounted quite close to the wall. I don't know, but I suspect John's was designed for more traditional placement. I also used an NPE cap to keep the cost down on that part.

          This is likely a difference between predicted and measured results - and the reason lots of us prefer to measure, rather than use manufacturer traces and simulations. My baffle was literally a couple thousanths under 5.5" - so that's not the difference.

          Regarding the cabinet - I'd fully stuff it - 1.7L stuffed will probably be fine. You want the cabinet full, but you don't want the fill touching the driver or so compressed that it's a dense clump of stuffing. Be careful that AVR autocorrection doesn't try to lift the bottom end too much and overdrive it.

          It's also fairly common, especially in budget designs, for the crossover to to be a significant cost of the unit as a whole.

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          • #20
            Great thanks for the reply!

            Is post 11 in the raw response http://techtalk.parts-express.com/fo...eaker-bmr-sb19

            Do you know which of the two curves is the driver response? Is this the response with the baffle or infinite bafle?

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            • #21
              The response with the prominent dip (the brighter red one) is the BMR. The other one is the SB19 tweeter. I took those measurements with the drivers in the box with the front of the box a little less than a foot off the wall.

              Please note - the dip isn't what we're trying to notch out - the hump from about 1.3k-1.6K is what we're trying to notch out - while affecting the dip as little as possible. I worked very hard with the notch to NOT make the dip worse - including some filter transfer functions that had a peak in the area of that dip - but the q of the peak was too low and messed with the areas I was trying to notch out - below the dip.

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              • #22
                Oh my god, thank you so much ........ Here I was all this time thinking you were trying to notch the dip further down hahahah.


                Yes I agree 0.3 mH inductor is probably the best bet for this driver and that the 0.15mH might be too small.




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                • #23
                  Here's where I'm at. I think I will first try without the notch. I'm then contemplating two designs. One is your original notch and then the second is a smaller attenuated notch. The reasons for the smaller notch are cost and also a smaller inductor . Any thoughts?





                  Click image for larger version

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                  • #24
                    If you put a resistor in parallel with the inductor and cap, you can make the filter less peaky and control the depth a bit better. I'd try a few values and see what looks good. Keep simming until you like the way it looks. You can adjust the width of the filter too by adjusting the LC values

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                    • #25
                      Excellent point.


                      Ok I think I'm going to order your design values 0.22 mH and 68uF capacitor and also a 10 and 20 ohm resistor (to play around with and find out how peaky the filter needs to be on my units)


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                      • #26
                        I've built the speakers. They sound OK. I find that I didin't like them with the inductor rolling off the highs, i.e. I liked them bright.

                        My main issue is that they sound a bit boomy/boomboxy on the low end. Would this be fixed by implementing the notch filter?

                        I filled the box with a bit of polyfill since it's a sealed enclosure.


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                        • #27
                          Boomy is probably caused by the box being too small and the polyfill not being a dense enough stuffing - that's why I originally suggested going to a larger box. IT also might be caused by the speaker being mounted to the wall. Move it 3-4 feet away from the wall and see if it goes away. The notch filter won't solve this problem - isn't in the boomy range.

                          You may want to listen for a few days with the inductor bringing the highs level. What sounds like more detail now may sound exceedingly bright and irritating in a couple weeks (ask me how I know). If you still don't like it - well - take it out and enjoy it!

                          You should give the notch filter a try. You may like it.

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                          • #28
                            Here's the finished product. Banged it out in a quick week, with hand tools only.

                            Click image for larger version

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                            Indeed, I think I might give the notch filter a try now. I'll try it with 25 Ohms and also 15 Ohms.


                            Yeah I gently stuffed it with polyfil, there's not that much space in the box and I was worried about getting the polyfill up in the diaphram of the speaker



                            Do you have a suggested cheap material I can attach the crossover items to? The stuff that parts-express sells e.g. https://www.parts-express.com/white-...5-x-5--260-182 are massively overpriced.

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                            • #29
                              Right now they are being used as surrounds, and for this purpose, the stated flaws (boomy low end, a bit bright, and the potential spike that needs the notch) don't really affect the performance as surrounds, since it's not critical.

                              I do plan on building perhaps another set for my desktop and bedroom, where it would be more important. I'm not sure what other full range in an attractive frame would be better suited for this size project.



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                              • #30
                                They look good! Nice!

                                I use 1/8" hardboard (available at any home depot/lowes) and use hot glue for light parts and zip ties and glue for heavy parts. Just drill holes where necessary for the zip ties.

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