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  • Help With Crossover Design

    Hey all, I'm a complete noob at crossover design, but I've read enough to know I don't necessarily want to venture out on this alone.

    I think the biggest hurdle here will be that there are no response graphs posted for the woofers I'd like to use.

    270-180 - Tweeter
    299-2198 - Woofers

    I'd like to use these in an MTM configuration, as a HT setup (music too, but not critical listening, just jamming out a bunch of noise). So, 4 sealed standard orientation, and one sealed on its side as the center. Further, I'd consider doing the main L&R as ported towers, whereas the sealed boxes will be hung on the wall. So that would be two ported, two sealed standard orientation and one sealed and toppled. BSC will be tricky as the front baffle will be 12" or so from the wall and the L&R will be very close to the screen (so one side of the baffle will essentially be several feet wide, where as the other side will be 2-3" wider than the woofer.

    I've read through this guide and understand enough to get started, but does anyone else have any recommendations or would be willing to supply a quick and dirty crossover? My goal is to keep this in the 'pretty darn cheap' tier and not spend more on crossovers than woofers. http://www.diyaudio.com/forums/multi...asurement.html
    If that link doesn't go through, it's an "introduction designing crossovers without measurement" page on another forum, which will pop up as the first search result if you are so inclined.

    I'd also consider going digital/active amping, as I'd love to be able to make tweaks without buying parts and resoldering, but I'd need recommendations on DSPs that aren't crazy expensive.

    I'm not looking for perfect here, I know I'd need to model the woofers, and the room, and the built speakers in the room with crossover 1 through crossover x. I don't have the equipment (yet, though maybe I will eventually) and definitely don't have the time to devote to dozens of variations. Two crossovers and an A/B test, cool no problem, just not dozens!

    Can anyone help?

  • #2
    Hello

    People on this Forum are happy to help, as long as they either have used the drivers or (without mentioning names for fear of embarrassing them) are simply brilliant at working out possible crossovers using the driver specs, etc and various software. But of no one's used the drivers and there are no spec sheets, it might be challenging. Keep your eyes peeled for replies.

    Are you choosing these drivers based on cost? If not, there are many proven designs from brilliant designers like Curt Campbell (eg Tritrix, in its various forms) or Paul Carmody (Overnite Sensation series) which would get an excellent result for you for not a lot more $$. For example, the Tritrix designs, (which use the same crossover with five parts, so not expensive) comes in vented MTM, MTM transmission lines and TMs.


    Good luck

    Geoff

    Comment


    • #3
      Shot in the dark . . .

      Oh, I'd put 'em in a 2.3cf vented box (the L/R mains), with a 14" long 3" Precision Port. Should do about 102dB @ 12w RMS @ Xmax in the 50s (Hz).
      Could go sealed in same size box, but vented has slightly better power handling.

      (There are other large hurdles Stated Fs on tweet is 1k, but you can see they measured it at 2k. Shouldn't cross below 4k probably. C-C distance is nearly 6-1/2", indicating an Fc near (or below) 2k. Will NOT be suitable for a horizontal MTM - 8" woofers never are.

      Low Pass (for 2 4n(ohm) woofers in series (no SPL gain), an 8n load:
      A 0.30mH series coil (gauge won't matter), and a 8n + 8uF Zobel.

      HP: 2uF series cap, 0.30mH shunt coil (to ground), L-pad: 3n SR and 15n PR. Only attenuated several dB.
      Crosses near 3-1/2 kHz w/just a bit of BSC. Reverse polarity indicated on tweeter, but try it both ways.
      Solid 8ohm design. Prob'ly not much real output above 15k - but that's not really so bad.

      Suggestions:
      Use a woofer w/known F/Z data (something smaller if you really NEED a horizontal CC), AND more Xmax (Dayton's "Classic" 8" has 50% more throw.)
      Use a smaller dia. (neo - probably) tweeter to cut down on C-C spacing.
      Just use sealed TMs for rears, then the box can be just over 1 cu. ft. (for wall hanging).

      Comment


      • #4
        Thanks for the replies! You all rock!

        I want to go with these woofers 1, because of the great value they look to have, and 2 I'd just love to have 10 8" woofers on tap. Should be able to crank nicely!

        I don't 'have' to go with a horizontal center channel, but the center channel will be located below the screen, would that still sound okay? (tweeter would be two to three feet below ear level)

        I'm not married to either driver, though I do like the woofers. I'm totally okay with going to a different tweeter (so long as it's not terribly expensive, say $30 max)

        Thoughts?

        Comment


        • #5
          Chris Roemer is a crossover wizard. What he gave you is as close as you will ever get without any measurements. If you chose Dayton drivers, which have full sets of accurate responses, impedance files, and measurements, he can take you from pretty close to an incredible final product.

          You need to get what will make you happy because that is what matters, but without a tweeter that can cross incredibly low, an 8" two way is not optimal. You can crossover an 8" two way at 2-3k, and it will "rock", but just know that there may be off-axis nulls and other issues, which you may not care about with this build and that is fine.

          Don't get discouraged with any advice, we all just want to make sure your final product is good and have all asked the same questions as you before! Good luck with your build. Nothing much better than being able to say "I made those!".
          Projects:

          transcenD: http://techtalk.parts-express.com/fo...5035-transcend
          Summits: http://techtalk.parts-express.com/sh...75-The-Summits
          References: http://techtalk.parts-express.com/sh...-My-References
          Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

          Comment


          • #6
            https://www.parts-express.com/dayton...eeter--275-070

            Legendary tweeter for not much than you are already spending. Performs well beyond its price would lead you to believe.
            Projects:

            transcenD: http://techtalk.parts-express.com/fo...5035-transcend
            Summits: http://techtalk.parts-express.com/sh...75-The-Summits
            References: http://techtalk.parts-express.com/sh...-My-References
            Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

            Comment


            • #7
              https://www.parts-express.com/dayton...oofer--295-310

              Here is the woofer Chris recommended if you want to stick with 8"
              Projects:

              transcenD: http://techtalk.parts-express.com/fo...5035-transcend
              Summits: http://techtalk.parts-express.com/sh...75-The-Summits
              References: http://techtalk.parts-express.com/sh...-My-References
              Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

              Comment


              • #8
                I'd go with this if you want to stick with the 8" MTM format.
                https://www.parts-express.com/peerle...eter--264-1020
                You'd have no problem crossing below 2kHz and it sounds pretty good. Dirt cheap too.

                Dan
                _____________________________
                Tall Boys
                NRNP Computer Sub
                The Boxers
                The Hurricanes
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                Conneccentric
                UX3

                Comment


                • #9
                  Again, thank you all for your contributions. I'm really glad I asked first instead of pulling the trigger too soon (closeouts have that gotta-do-it-now affect, ya know?)

                  Okay, I'm definitely willing to consider other drivers. Here's what I'm thinking. The proposed woofer (Dayton 295-310) and tweeter (Dayton 275-070) will drive the cost of drivers up by 60%, which is okay, just moving out of my super-budget-minded mode. The biggest problem I see is that the woofer is 8ohm, meaning I'm stuck with having to support a 4ohm load (greater sensitivity but harder on amp selection) or a 16ohm load (easy on amp, but no more sensitive than a single woofer with twice the power handling)

                  The load seems like a pretty significant compromise to me. Thoughts on that?

                  Also, if anyone has experience with a vertical center channel that lives below the plane of the L&R speakers, please let me know if it's terribly distracting or not a big deal. Does it still anchor the dialogue in the center of the screen or does it sound like it's coming from below?

                  Comment


                  • #10
                    A couple of comments:

                    it's rare to see a '16 ohm' set of speakers; generally, when designers do an MTM or TMM it's a 4 or 8 ohm nominal design (e.g. the Tritrix MTM is 8 ohm as it uses 2x4 ohm woofers in series). I don't have the knowledge or experience to know why this is

                    remember that the 'ohm' rating of speakers is nominal and actually fluctuates according to frequency, which you can see on the designers' frequency response graphs. So, a 4 ohm speaker might range between 3 and 9 ohms.

                    most modern amps/receivers will happily run 4 or 6 ohm nominal speakers unless you overdo the volume; my Yamaha RX-596 is almost 20 years old and has no problem at all running my 6 ohm "Slapshot" MTM speakers. The Yamaha manual says it will run 6 ohm speakers.

                    From memory, the "Dayton 8" TMM or MTM (I'm not sure which) was designed with these drivers, although as a stereo pair, not home theatre, I think the details are on this Forum somewhere. From memory it had rather large cabinets. Of course, I haven't heard it so can't comment on its sound but you might want to search it out.

                    Hope this helps

                    Geoff

                    Comment


                    • #11
                      Well I don't know what to do anymore. :-)

                      My first pass at the HT thing was to do a mmtmm with the above mentioned tweet as well as buy out 6.5s 299-2196. The difficulties I initially identified was having to do a 2.5 way (see first post about crossover difficulties!) as well as the final impedance being 4 ohm with those woofers. After some of the discussion here, having a mmtmm on its side would probably be worse than just the mtm, so that's another drawback. It would have been visually impressive though, just look at it! I'd probably use the magic of woodworking to incorporate the three speakers visually into one u shaped thing.

                      So now, I guess the question is what HT solution should I look at? I'd like to have pretty high sensitivity and output. I'd prefer an 8ohm load. I also want to keep this budget friendly. My initial estimate for drivers (the 8T8 version above) was $200 for 5 speakers. That's pretty outstanding, however the reasons against that design are numerous, mostly the unknown driver and the low power handling (seriously, 12 watts to hit x-max, I didn't expect that!) I like the meaty punch that a handful of 8s would deliver, or two handfuls of 6.5s. I currently have a 15" sub to take care of the very lows, but the lower I could cross over the mains, the better. 8s have the advantage there.

                      I'd be okay with going to a TM as long as the drivers can deliver. Personally, I like the idea of a ton of cheap drivers performing well because they aren't stressed, it's just cool. I'd look at line arrays, but the drivers have to be stupid cheap to fit in budget and the center and surrounds would be more of a mismatched mess.

                      Moving up to the nice and known 'Classics' works okay with budget, but then presents a 4ohm load. Some folks say it's not a big deal, others will disagree (though not in this thread yet). I know I'd prefer 8ohm nominal, but could probably deal with the 4ohm thing if needed.

                      Still researching what people say about having a vertical speaker below the screen. Not surprisingly some people say it's totally cool, and other people act like it kicked their dog.

                      Sorry for seeming so directionless, but I'm doubly glad I'm asking the questions and getting great feedback from you guys before buying and building and being disappointed! I want big, loud sound from my home theater - cheap (but not crappy) . I want to be able to say that, with the help from you all, I built it. I know that budget-minded systems are not the sweet-spot of the DIY hobby, but I'm not expecting that $300 worth of drivers is going to put $30,000 home theaters to shame either. I'm realistic. In a project, the best way to save money is not to build the wrong project :-) That's why I'm here.

                      Thanks all!

                      Comment


                      • #12
                        Dave Tenney's ( Google "Dayton 8" - or similar ) LARGE (3-4cf) MTMs do NOT need a sub. They'll do a strong 30Hz, but they ARE 4ohm.
                        Since you HAVE a sub, you could:
                        Build the "Classic" 8" TMs for L/R mains, and maybe go to "Classic" 6-1/2" (w/275-070 "Silky" tweeter) for rears, and "possible" horiz. MTM CC.
                        (probably better for you >) Build "Dayton-III" (MTM using Classic 6-1/2 drivers - but again, THAT would be 4ohm) L/Rs, w/TMs for rears,
                        and a horiz. MTM for CC (using 6.5" or 5.25" woofers).

                        4ohm note: the 8" Classic is ONLY avail as an 8n(ohm) driver, so MTM ends up being 4n, but . . .
                        the 6.5" and 5.25" Classics also come in 4n versions, making an 8n MTM possible - see "Tritrix" (PE sells a very popular kit for this one - not that you'd have to use it).

                        Comment


                        • #13
                          I keep going back to those monster Dayton 8s. One complaint I was able to dredge up is that the upper midrange isn't the best on those woofers. There was a project to update the Dayton-III with a tweeter that crossed lower, but that tweeter is discontinued/NLA. That project was deemed a success for the Dayton-III and should also apply well to the Dayton 8s, but I'd need to find a different tweeter to cross lower, then rework the crossover.

                          I've nearly pulled the trigger on Tritrix a dozen times in the past. The only thing holding me back is the 5.25 is so little. What I've read though, they sound great and are a super value!

                          Gaaaaah! Decisions are hard.


                          One thing I don't understand is how the Dayton Classic 8 in a large ported enclosure can get so low and so loud and handle so much more power with only 1.5mm more x-max (granted that's over 30 percent longer throw) over the buyouts I originally liked. Thiel Small parameters aren't my strong suit (obviously)

                          Comment


                          • #14
                            I haven't looked at those particular driver parameters, but try to avoid the "handle so much power" factor being anything worth considering relevant. A brick can take lots of power (from a blowtorch!), doesn't mean it makes any more sound output. It's like evaluating an automobile based on how much gasoline it can burn. . Look at efficiency (or sensitivity, dBSPL/2.83V/1m), effective cone area (Sd) and xmax for hifi. Power handling is relevant only for pro audio installations and frat parties, not hifi.
                            Free & Free-form simulator/designer for Passive Crossovers
                            SynergyCalc 5: design spreadsheet for Wooden horns and DIY Synergy Waveguides
                            Super easy and cheap to make high performance sound diffusers

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                            • #15
                              I kinda of get where you started - max output and visual appeal. But consider this ... these cheap woofers are just a small component of the over all cost of a system. Just building the enclosures will be a big investment in time and money. Worst case, you may not be happy with the results, best case , you'll outgrow the sound and want better.

                              So ... I would recommend building part of the system using an existing, quality design with the budget (front mains and sub?) and add to that later. You can always use something cheap for surrounds until you do.

                              Google Paul Carmody's Swopes.

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