Announcement

Collapse
No announcement yet.

Preparing to build my first speakers and have some questions

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by rpb View Post
    I'm not the posting police, but Parts Express doesn't want links to competitors posted. Maybe copy and paste photos rather than links.
    Oops sorry I didn't realize. I'll go back and remove the links.

    Comment


    • #17
      Originally posted by Kornbread View Post
      That last one is 2.5x as much as the first two!?! Passive or active? If passive, have you attempted to sim up the crossover for any of these drivers using supplied specs?
      Yup the last one is pricier - it's a set I had originally bought for a different purpose but ended up not using. The speakers will be passive - I prefer to not be constrained to a system and also active requires much more $$$ in amplification. Plus, I'm really enjoying the challenge of designing crossovers in addition to selecting drivers and building a proper cab.

      As for simming x-overs, I'm waiting for the DATS V3 to arrive to get T/S params and then I need to dig out an old Windows XP machine I have. As far as I know none of the available sims are made for a Mac.

      Comment


      • #18
        So, the OW1 is only 87dB. Your paralleled mids should run near 92, making the Thiel dome (27TDFCG) the better choice for the MTM section.
        Due to BSL, ideally you'd like about a 98dB woofer. Those (w/decent bottom end) are hard to come by (outside the "pro" arena - and THOSE won't go as low, probably).

        How do you feel about an MTMWW? A paralleled pair of RS225P-8As in 3cf w/a 4"id x 5" long port will have the desired sensitivity and an Fb and F3 in the upper 30s.
        (Yup, preliminary XO is ready to go.)

        Comment


        • #19
          Thanks for your response Chris.

          Originally posted by Chris Roemer View Post
          So, the OW1 is only 87dB. Your paralleled mids should run near 92, making the Thiel dome (27TDFCG) the better choice for the MTM section.
          Due to BSL, ideally you'd like about a 98dB woofer. Those (w/decent bottom end) are hard to come by (outside the "pro" arena - and THOSE won't go as low, probably).
          What is "BSL"? I am not familiar with the acronym.

          Originally posted by Chris Roemer View Post
          How do you feel about an MTMWW? A paralleled pair of RS225P-8As in 3cf w/a 4"id x 5" long port will have the desired sensitivity and an Fb and F3 in the upper 30s.
          (Yup, preliminary XO is ready to go.)
          I've thought about doing MTMWW but the bottom woofer doing vocals so far from the mid and tweeter somehow feels wrong. Perhaps this is a non-issue in the real world but without experience I have a hard time wrapping my mind around it. I've thought about a WMTMW but I'm not sure if that alleviates or adds problems.
          Last edited by GoodMusic; 11-16-2019, 06:44 PM.

          Comment


          • #20
            Originally posted by GoodMusic View Post

            I am familiar yes - via ton of research in the past 6 months. So I would say I'm mostly well versed on the hypothetical side of things but I've yet to put any of it into practice so I don't have the benefit of real world experience. There is still some "book learning" I need to do and I have a checklist of specifics that I need to do more research on. I literally do 2-3 hours of research a night but there are some things I've just not been able to find satisfying answers on - like the mid to woofer transition. Properly matching power handling and sensitivity across drivers is one of those things I need to do a deep dive on.
            It's not complicated at all really. The maximum clean SPL of you speaker will be limited by something. Sometimes it's the tweeter power handling. Sometimes it's woofer excursion. Sometimes it's the heat going to the driver rather than the excursion. Sometimes it's the power available from the amplifier. You don't have to maximize the output potential of the speaker for it to sound excellent at modest SPL, but if you want to play louder, then you have to look at limits more closely. One mid will work until its excursion gets out of hand, or until the voice coil temperatures get so hot that the voice coil warps or melts the glue holding things together.
            An 87dB mid will work fine with a 90dB woofer, or an 84dB woofer. The x-over will use padding resistors to match them up. These resistors potentially can also get very hot, so that's a concern as well. (I've never had any even get warm, but I've heard others have. )

            I've used the RS270P-4 in a 2-way, and it sounds very good to me. It can go very deep in a large ported box too! If you needed to cross higher than 400hz due to using one mid, this driver would not have any issues with crossing higher. I'd go with the 8 ohm version if you were to go this route. There are lots of opinions on what the ideal x-over points are for a 3-way. I'm not trying to suggest this over the others being discussed. Most of my decisions come down to cost, and speaker size. There's endless compromises, but that's what makes it interesting.

            Comment


            • #21
              Click image for larger version

Name:	GMmtmWW.jpg
Views:	130
Size:	110.3 KB
ID:	1424956
              I feel like you feel that I'm trying to talk you into something...

              I've got this XO worked out already. The 4" mids (mtm) run from 400Hz to 4000Hz (nearly).
              The "flat" (un-summed) line @ 86dB is a single 4".
              There would be nothing wrong w/just a 3-way (TMW). A single RS225P would be the blue curve shifted down -6dB. You could use the (fabulous) OW1 3/4" alright then.

              Thing is, while the 4" mids should have great dispersion, and look flat as HE-double hockey-sticks, the "active" part of the cone is barely over 2-1/2", and their stated Xmax is only 2.6mm.
              There biggest limiting factor (however) is their (thermal) rating of only 15w RMS (probably due to some fairly fine wire wrapped around a small v.c. former). An 86dB driver will run at 96dB @ 10w. At their rated 15w they'll push almost 98dB. In a sealed/stuffed 0.04cf box, they can play @ 150Hz @ 15w w/out hitting Xmax. At 120Hz however, they hit 2.8mm.

              Paralleling two 8ohm 4"ers raises their sensitivity by +6dB (the center pale-orangish curve, w/its band-pass filter applied). Half this comes from doubling the cone area, the other half comes from halving the impedance.

              W/the mids running at 92dB, the 87dB OW1 turns into the limiting driver. You still COOULD use it, but the mids would need about -6dB of attenuation to stay in balance.

              So, using the 27TBFC lets the mids open up, but then you need a 98dB woofer so (after about -6dB of BS-loss) you can end up level-matching the tweet/mids near 92dB.
              A "pro" woofer could be had w/a sens. of 98dB, but typically they won't have that good of bottom-end reach.

              If you're worried about the lower vocals coming offf the woofer ('cause the mids aren't "robust" enough to run much below 300-400 Hz), then you won't really be able to run the woofer down at the floor level. MY XO has FULL (6dB) BSC, so not only CAN you keep the woofs up under the upper mtm, that's actually the best place for them. You can see I've got a pretty smooth BSC line running roughly between 1kHz and 100Hz. If you ran a single woofer (which has to be up off the floor because of your 4" mid(s), you'd need full BSC anyway, and on, and on, and on, . . .

              I'm running out of steam here -

              Comment


              • #22
                And.... With two mids, half as much heat is sent to each at any given SPL level compared to one mid. Excess heat causes dynamic compression. Cooler operating mids would be an advantage.

                For speaker sensitivity, I look first at the woofer sensitivity, and my desired amount of BSC. The speaker sensitivity will be the woofer sensitivity minus the amount of BSC.
                For an example, the Dayton DSA315-8 12" woofer is 92 dB in the 100hz to 400hz range. So, if you assumed 4dB of BSC, the mid(s) would need to be 88dB in the 400hz to 3k range. The speaker would then be 88dB as well. So at this BSC, the OW1 is marginally going to work with no padding resistor(s). One mid would also work, likely with no padding resistor. Two mids would still be preferred, but would cost more. Two mids would have lower distortion too!

                https://www.parts-express.com/pedocs...ifications.pdf

                Comment


                • #23
                  The RS225-8 is on sale.

                  Comment


                  • #24
                    One more thing. Consider the amplifier power needed for a given SPL. The DSA315 would need a lot less than the RS225. (Unless I missed something, which I might have.)

                    Comment


                    • #25
                      Thanks guys. I'll chew on the above responses and probably have more questions lol.

                      Comment


                      • #26
                        Originally posted by Chris Roemer View Post
                        Thing is, while the 4" mids should have great dispersion, and look flat as HE-double hockey-sticks, the "active" part of the cone is barely over 2-1/2", and their stated Xmax is only 2.6mm.
                        There biggest limiting factor (however) is their (thermal) rating of only 15w RMS (probably due to some fairly fine wire wrapped around a small v.c. former). An 86dB driver will run at 96dB @ 10w. At their rated 15w they'll push almost 98dB. In a sealed/stuffed 0.04cf box, they can play @ 150Hz @ 15w w/out hitting Xmax. At 120Hz however, they hit 2.8mm.
                        Chris, could you tell me how you calculated what Xmax would be @ 150Hz and 120Hz?

                        As for the woofer, I suppose I can do 2 RS225Ps for a sensitivity of approximately 89-91db with BSC and be just about in line with using 2 mids and the 27TBFC. I could go WMTMW

                        Comment


                        • #27
                          You CAN go WMTMW, but I'd go MTMWW which makes it easier to keep the tweeter at (seated) ear-level (36"-40"?).
                          WinISD ( linearteam.org - sorry Craig ) can show you cone excursion w/any given source level. "X-max" stays the same, but excursion varies by freq. (more stroke at lower freqs.). I actually simmed a pair of those mids in more like a sealed/stuffed box of 0.06cf.

                          Click image for larger version

Name:	xmax.jpg
Views:	84
Size:	116.4 KB
ID:	1425343

                          Comment


                          • #28
                            What sort of speaker are you wanting to build? This is your first speaker. Do you plan to build more? Will these be used with a sub, or as part of a home theater? How loud do you want to play? Do you know how loud 90dB sounds? Do you want much more than that? How much amplifier power do you have,or plan to have? Where in the room will the speakers be located? How big is the room? Part of designing your own speakers is designing for your specific goals, or needs. Trying to design one that pleases everybody, or every situation, is not usually the best approach. You seem to be overly focused on sensitivity. Why?

                            Comment


                            • #29
                              Originally posted by rpb View Post
                              What sort of speaker are you wanting to build?
                              Full range-ish strictly for 2 ch listening in a non-WAF area (non-WAF = room treatment). May add a sub or 2 somewhere down the line for the bottom octave.

                              Originally posted by rpb View Post
                              This is your first speaker. Do you plan to build more?
                              Yup. I want to do a 3 way stand-mount for the bedroom. Also, I can easily see myself getting hooked and building speakers just for ****!!s and giggles.

                              Originally posted by rpb View Post
                              How loud do you want to play? Do you know how loud 90dB sounds? Do you want much more than that?How much amplifier power do you have,or plan to have?
                              I normally listen at ~65-72 at the listening position (~71-78 @ 1m). 90db is pretty loud for me (at listening position) and I have no NEED for more but would like to know that I have more available if I get in the mood and want to crank up a song or two. I currently use an NAD C370 that's rated at 120w/ch but measured 170/ch by Stereophile. Future amplification is (power-wise), whatever I need. BUT, I'd love to have some freedom as some of the amps I'd like to try are relatively low powered (I'm speaking strictly SS).

                              Originally posted by rpb View Post
                              Where in the room will the speakers be located? How big is the room? You seem to be overly focused on sensitivity. Why?
                              For my own listening enjoyment, they'll be located wherever I can get them to sound best. I can move them out of the way if needed. The area is open (the entire downstairs of a small townhome) and I'd like to be able to get some volume out of them if I have a party.

                              Comment


                              • #30
                                Good music, I have a 3 way with a single rs225p, and it does everything that you described wanting. If you have two of them on the bottom in parallel, they could blow you out of a room, if 90 db is LOUD to you. The great thing about a mtmww using them is you will barely be running your amp at your volumes, which equals low the, and the speaker distortion will be much lower because they will barely be breaking a sweat.

                                Comment

                                Working...
                                X