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  • #31
    Originally posted by dcibel View Post
    John, was there any specific measurement that I can take for you apart from what is already shown?
    Thanks the measurements look good. I find it interesting to see the how the directivity breaks into nodes off axis.
    John H

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

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    • #32
      Had some time to listen a bit more today. Here's where I think I'm settling on the response. I didn't retake all the off-axis measurements, this is on-axis with the tweeter at 20". I came around this response after looking at the average off-axis response, with higher weight applied to the on-axis measurements. Later on when I find their final home I'll worry about the response on the low end a bit more.
      Click image for larger version

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      Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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      • #33
        Just one more measurement image for the AMTPRO. I wanted to see what effect the felt has on the rear wave of the tweeter, so here it is. This measurement was taken 1.5" from the rear of the driver. The top trace is without any felt, middle trace is a single layer of felt, bottom trace is with both layers of felt applied.
        Click image for larger version

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        And the effect on the front wave, measured about the same distance. Same colours correspond to the same measurements. Note the scale here is 1dB/div instead of 5dB/div to show the detail.
        Click image for larger version

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        Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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        • #34
          This weekend we have a heat wave with some +30 deg C weather, some years there is still snow...As a result I am hanging out in my very cool basement as we don't have A/C in our house. I went a little crazy with the mic.

          First, I retook my polar measurements with a bit better care to keep the high frequencies reflection free. Here is the front polar response of the speaker, with no felt applied to the tweeter, normalized to the on-axis response:
          Click image for larger version

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          Next is the same conditions, rear side polar response for interest sake:
          Click image for larger version

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          Here's the individual response curves, with my current EQ applied that I've been enjoying:
          Click image for larger version

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          Last but not least, I took the above individual response curved, and created a weighted average, applying a higher weight to the forward facing measurements:
          Click image for larger version

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          Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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          • #35
            Next up, I added one sheet of the provided felt to the back side of the AMTPRO tweeter. This felt is about 3/8" thick. It affects both the front and rear response as you can see.

            Front polar response, normalized to on-axis:
            Click image for larger version

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            Rear polar response, same conditions:
            Click image for larger version

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            Individual response curves of the front facing measurements:
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            I think the next step is to adjust my EQ curve to get a close match to the previous response, and see how my ears like the addition of the felt. Based on the measurements, I should prefer the felt as it has a more consistent response in the upper frequencies, however the rear wave is also attenuated. But with the felt I also have a bit raised level from 5kHz and up so the response will be adjusted to make a better comparison with my ears. That's all for now folks!
            Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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            • #36
              Baffle Detail:
              The baffle is a 1.5" thick bamboo counter top from Lowes. Originally I was going to use baltic birch plywood, but I liked the look of these boards more and the price was right so here we are. The baffle shape is optimized for dipole operation, and the shape was cut by CNC. I was fairly disappointed with these boards after cutting them, as there were significant gaps inside that needed to be filled. The gaps were filled with sawdust, then epoxied over top and sanded down. The round-overs were completed by hand.


              Thanks for sharing your experience with the bamboo countertop material from Lowes. It looks really nice. Was it difficult to cut & route?

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              • #37
                Originally posted by Balocco View Post
                Thanks for sharing your experience with the bamboo countertop material from Lowes. It looks really nice. Was it difficult to cut & route?
                Not at all, you can treat it just like any other hardwood. The grain is very straight so it has a higher tendency to split when screwing into it, so be sure to drill pilot holes and test on some scrap for your driver installation where the holes are near the edge of the material. If using wood screws use a fine thread as you would for hardwood. Routing at high speed I did not have any problems with tear out.

                The countertop used was a 2ft x 6ft board, both baffles were able to fit on it with some scrap left over, I think the cost was CAD$175. I think there's a number of places that sell this type of board, probably advertised as a countertop.
                Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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                • #38
                  I couldn't find the passive crossover between mid and tweeter?

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                  • #39
                    Originally posted by ontariomaximus View Post
                    I couldn't find the passive crossover between mid and tweeter?
                    If you look in my photo galleryt (see the end of my 1st post), there is photos of the passive crossover and its installation in the woofer cabinet.
                    Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

                    Comment


                    • #40
                      what are the inductor values? can't read them

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                      • #41
                        This crossover is of little use outside of this design, a DSP is needed in addition to the passive filter to flatten the response and provide the high pass filter on the midrange. I don't really understand what use the values are to you, but if you must know...

                        The woofer circuit is a 2nd order filter consisting of a 1.3mH inductor and 22uF capacitor.

                        The tweeter circuit is a 3rd order filter consisting of a 11uF capacitor, a 0.36mH inductor, and a 22uF capacitor. a 3 Ohm resistor is in series with the tweeter post-filter to bring the level down to match the midwoofer.

                        The tweeter is wired in reverse polarity.
                        Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

                        Comment


                        • #42
                          First off, beautiful speaker! Second, that top end drop with the AMT pro is why I added the AMT mini to my 442 project. Just added that top end bit that the big tweeter was missing. Last, I used the felt in back as it just smoothed the midrange FR. Looks like it does the same for your set,too. Nice job man!
                          A mains
                          The Ventures
                          Open Invit8tions
                          RSR
                          Sound Troopers
                          Acorns
                          442
                          DGBG's
                          The Monuments

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                          • #43
                            Originally posted by 6thplanet View Post
                            First off, beautiful speaker! Second, that top end drop with the AMT pro is why I added the AMT mini to my 442 project. Just added that top end bit that the big tweeter was missing. Last, I used the felt in back as it just smoothed the midrange FR. Looks like it does the same for your set,too. Nice job man!
                            Thanks! Yes, I think I am settling with a single layer of felt, in the very top end it definitely tames the refection from the motor and baffle coming back through the diaphragm, and my room isn't very acoustically absorbent so damping the rear response a bit I don't think is a bad thing. Based on the published off-axis response of the AMTPRO, I assume they measured without the felt installed, which is odd since the response is better with it in place.

                            I decided against the extra supertweeter on the top end to prevent having another lobe in the polar response. Leaving a bit of the natural rise of the tweeter in there has done the trick for me. It is a very directional tweeter vertically, but in that sweet spot it is truly wonderful. These were designed as a sit down and listen speaker anyway, and serve their purpose very well.

                            I continue to tweak the response every few days. I think I have the level between the mid and woofer and the phase alignment there just right now. Comparing my EQ curve to my passive crossover, I think I might have been better off to have just left the 3 ohm resistor on the tweeter out completely. I may do that soon, as I think I may dismantle it a bit and use a buffer on the baffles to make them really shine. I think the Tung Oil has had sufficient time to fully cure by now.
                            Don't waste your money on a new set of speakers, You get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

                            Comment

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