Announcement

Collapse
No announcement yet.

Crossover Confusion and the B652 Air

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

  • Crossover Confusion and the B652 Air

    I didn’t see an intro thread, I apologize if I missed it. Posting from Sacramento region of Northern Cali. I recently got back into cars & car audio which led to needing music in the garage while I work which let to, well so on and so forth. Please forgive my ignorance as I have never dived this deeply into speaker/crossover design so I am just learning.

    Background:
    Picked up a DA DTA2.1BT2, the MK402X speakers (back ordered), and the HSU VTF-2 for my garage 2.1 system.
    I liked the mini set-up so, even using my car speakers, much I decided to get a system for my daughter’s college studio. She needs a headphone jack so I picked her up:
    Topping MX-3, B652 Airs (because they were in stock versus the MKs and the right $), and a DA Sub-800

    So I’ve been reading and learning about crossovers and also reading on all the mods for the B652 Air (and I didn't want to resurrect any of those old threads).

    Just when I think I am figuring out crossovers and have components picked out I find info that confuses me.


    For example, in this thread linked here 63991-dayton-b652-air-improved?244602-Dayton-B652-AIR-IMPROVED=&highlight=b652 Calspeak says
    “The next thing I did was reverse the tweeter polarity connections at the back of the tweeter like the other modder did. Also added considerably more stuffing. About 10 inches of stripped R-13 OCFG insulation.
    Replaced the 3 ohm tweeter resistor with a 12W Mills 6 ohm resistor because the highs were measuring and playing a bit hot. Lastly, I added a 1 mH air core coil (20 ga.) in series with the woofer”
    The first part all makes sense but isn’t adding a 1 mH inductor in series with a woofer creating a 1st order low pass XO well below a woofers upper frequency limit not to mention well below the tweeter’s low end range? I realize some of the calculators out there don’t account for the “R” value of the electrical component being used but that wouldn’t have that much of an influence would it?

    The Zaph woofer crossover also shows a 1.0 mH inductor but with an 8.0 uF cap. Again, any calculator I tried whether LR, Butterworth, undefined seems to indicate a low pass Freq <1400

    Click image for larger version

Name:	Dayton-B652NEW-crossover_Zaph.gif
Views:	728
Size:	3.3 KB
ID:	1433438


    I won’t get into augerpros mod, post already too long

    At first, I was confused by the Dayton Audio crossovers,
    dayton-audio-45k-lpf-4-low-pass-speaker-crossover-4500-hz-12-db-octave--260-1912

    XO uses a Series inductor value of 0.28 mH and parallel capacitor value of 4.4 uF, the calcs I’ve seen suggest values of 0.20 mH and 6.25 uF are needed

    But then I found the calculator on part express where you can pick the type of crossover. The DA values line up with a 2nd order LR XO. What I don’t know is what the other sites are basing their calcs on (BW?).

    I’m assuming this discrepancy is due to the effects of the overall circuit and the rest of the components properties (i.e. like their resistance) but in the end I don’t like to assume. Am I looking at this the right way?

    I was going to try out the free software from Vituix. I have had good luck (I think, from a privacy standpoint) with REW, EAC, and various other open source software but for some reason I got a little paranoid with this one. No rhyme or reason, I guess just getting a little paranoid the older I get. Unfortunately I missed getting back to my computer yesterday for the 15% sale (it was 15% not $15 I think). I may have been able to talk myself into the speaker DATS and the PE XO software.


    I guess the takeaway is to find a better single source to learn more about crossovers then multiple snipets from various websites. What are those things called we used to buy to learn, books or something like that.

    Ultimately, I am not looking to spend a lot on the B652, my daughter will never know, even if I do, but if I can do some low cost 1st order XO to smooth things out a hair, I would like to do that for the fun factor and learnings I get out of it.

    I'm interested in improving the blending of the sub with the B652 on the low end and get the B652 away from where they may distort. Maybe a highpass around 100 to 120 Hz

    I will have install materials left over from the car project so I can install CLD and CCF foam in the speakers without any additional cost.

    I can add in a couple 1/2" diameter rods as well, can these just be glued/wedged in?

    The tweeter mod, if not already done on the set I have, is easy enough.

    Is it worth doing a 1st order low pass on the woofer before its natural roll off or in essence use a band pass on the woofer? I can't start the roll off where some of the known woofer breakup is because the tweeter doesn't reach that low according to the specs so what LP freq makes sense? I was thinking 4000 to 4500.

    Thanks in advance to all of those that made it this far!

    Take care!

  • #2
    I'm not too experienced at these things, but I suggest you ignore any crossover calculator as they're highly unlikely to produce a good result. Also, crossover simulation programs like Vituix and Xsim need you to input measured data in order to work properly.

    In your position, would just go with the mods suggested by Calspeak, which involve replacing the woofer with the Dayton DC160-4 and other tweaks. As I understand it, the standard woofer in the B652 is allowed to run full range (i.e. with no inductor), so if you use a different - and by all accounts, better - woofer you need to control its response. That's why you need the 1mH inductor.

    Zaph's modifications are on the standard B652 and don't involve replacing the woofer; he also suggests it's not worth spending too many $$ on the speakers.

    I'm not familiar with the cabinets so I don't know how easy/hard it will be to insert some strengthening.

    I'm sure other members with more experience and knowledge than I will be able to help you out.

    Good luck!

    Geoff

    Comment


    • #3
      A great book for digging into all this stuff is Ray Alden's "Speaker Building 201".

      It's not a good idea to mix&match mods. If you don't want to do a driver swap then just follow THAT mod.
      If upgrading the woofer suits you (prob. adds too much to the co$t?) then follow THAT mod entirely.
      There ARE some fairly bad projects in the "Showcase" - they really aren't vetted much, BUT . . .
      it's MOSTly different here on PETT - both the guys you've mentioned know exactly what the he-doublehockeysticks they're doing.
      XO design is no where near as simplistic as those online calculators make it appear.
      If you want to see what's going on you need to run a sim using your exact driver's .frd (frequency) and .zma (impedance) data files.
      An "8ohm" (or 4ohm) woofer will probably only run exactly at that "nominal" impedance at 3 places on its "curve": below its Fs, above its Fs (on its way to Zmin), and on its way up to its highpoint ( at 20kHz ). These 3 points will typically all be below 200-300Hz, nowhere near where they'll be low-passed (so those calculators really are no good).

      Comment


      • #4
        OK, the B652's "mid-woofer" is nominally a 4 ohm impedance and to "tame" it at a reasonable cost, just a 1 mH inductor and 8 uF cap (electrolytic is fine) is more than sufficient. For the "Air" version, raising the tweeter XO frequency above the regular Zaph design MIGHT be an improvement, but I'd probably just go with a 8uF cap for "C0" and call it a day, along with any suggested resistor for padding down the "Air" tweeter. For what it's worth, I sure wouldn't spend the money on a 6 ohm Mills resistor, I'd just put another 5 watt PE 3 ohm resistor in-line with the OEM one.From my playing with the B652's I wouldn't use fiberglas insulation either. It eats up the sound too much. Just some plain Wally-World poly-fill (or any crafts store) pillow stuffing worked better for me.
        I got silly on one pair of mine, adding a rear cabinet that about doubled the cabinet volume and costing me over 1/2 the stock power handling at the gain of MAYBE 10 Hz of lower extension, and MAYBE "smoother" SQ, probably not! The very best you can hope for the B652's is to be a passable "surround" side speaker. The PE MK402X will eat the B652 alive, and it's humble enough.
        Good luck and have fun!

        Comment


        • #5
          Thanks for all the replies, I am looking forward to my MK402X backorder making it here eventually, to be honest, I would have bought a 2nd set of them if they weren't out of stock. I was a little impatient since I was doing so much work in the garage and didn't want to deal with the MK towers since she has to move twice a year for a couple more years. Still, the B652's will suit my daughter fine, she's used to a Monoprice bluetooth speaker, one of their cheapest ones, that has ZERO bass to say nothing of the distortion.

          Comment


          • #6
            You could always buy your daughter another pair of kit speakers for a special occasion: maybe a pair of C-notes, Hitmakers or Classix so she can decorate the cabinets to taste?

            Seriously, it's great to give the gift of music.

            Geoff

            Comment


            • #7
              Later production B652 speakers use an 8 ohm mid bass and 4 ohm tweeter. Mine are about 8mo.old. I modified the crossover to 4500hz. 6/6. Total cost under $10 using PE parts.

              Comment


              • #8
                Originally posted by Regore View Post
                Later production B652 speakers use an 8 ohm mid bass and 4 ohm tweeter. Mine are about 8mo.old. I modified the crossover to 4500hz. 6/6. Total cost under $10 using PE parts.
                Good info, thanks! I planned on getting inside of them eventually, but I've been pre-occuppied with other stuff. I will definitely take a look. Because I am new at this and don't want to make any assumptions, can you please elaborate on your 6/6 comment? Did you add a cap in series to change the high pass to the tweeter?

                Comment


                • #9
                  Hi MegaG. My upgrade was for the B652 not the B652 air. I added a .25mh 20 gauge inductor in series with the woof. Part # 257-026 $3.10. I don't know what the impedance of the air tweeter is so i can't recommend the proper value of capacitance for the tweeter.

                  Comment

                  Working...
                  X