Feel free to ask questions. I'll do my best to answer.


Thursday, July 22, 2010

More on the B2031P and diffraction





I also wanted to test my diffraction theory with the ports next to the tweeter. So I got some cotton balls from the "stuff" drawer and filled the front of those ports with white cotton balls! Well, the results are something to see. The top polar and impulse graph are prior to port stuffing. The next are after the cotton balls were installed.  Now I'd say it doesn't look like the woofer break up was any problem.

91 comments:

  1. Hi - really interesting posts so thank you very much for those! I'm currently considering an upgrade to my home studio speakers from old JBL Contorl 1s to eith the Behringer 1030a or the equivalent KRKs. Would you have a moment to spare some advice for me? Money is not really an issue (but obviously I wouldn't mind saving some!) but the Behringers do seem good value for money. Many thanks, Chris (chris_evans1973@hotmail.com)

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  2. I wish I knew how your old JBLs performed. Without that info it's hard to make a recommendation. I will say that the KRK are not as good as the Behringers(that comment would make a few people gasp!). The 1030s are shockingly revealing. I've always wanted to hear/measure the 1031A... Should be a fairly ideal speaker provided the QC is good. Good luck.

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  3. how deep and how densely did you stuff the cotton in? was the idea just to level it with the baffle so that there are no edges to diffract from? do you think foam felt strips on the sides/edges of the ports could be (as) effective?

    thank you very much

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  4. They are stuffed about 1-1.5" deep and tight!

    The original idea was just to absorb the wave coming off the tweeter. I'm planning on doing another experiment with a flat baffle. I'd guess that placing strips beside the port would help, but I'd also guess it would be to a lesser degree. I'd be interested in those results as well and will place it on my list of experiments. Thanks for the idea. Next time I do something with the one I have left, I'll do that too.

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  5. Oh, the cotton sticks out just a little bit from the front of the baffle.

    You are most welcome. I just wish I had some time to do some new blog posts. Several good ideas right now, but utterly no time.

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  6. I was wondering about one idea for the diffraction issue. What if one were to take thin foam piece the size of baffle, cut out portions such that waveguide, tweeter and woofer is exposed and put that on the baffle. Also stuff some foam inside the ports. That would make it almost like 1031a. Do you think that would help ? Hopefully foam absorbs and doesn't diffract the sound....
    If that does away with diffraction and makes sound smooth, one may have better speaker than 1031a as 2031a has better pattern control and a lower crossover as well....

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  7. The foam would have to be carved so that it would have ridges perpendicular to the baffle. Wool felt should be more effective. I've been doing a fair amount of fine woodworking lately. I actually want to rebuild the one B2031P I have left. That will still be a while though. I so want to get back into this hobby. I just set up a home theater for my GF and now have the Mackies as my gag rag system. It's a blessed life. The B2031p is her center channel--it already works great there. When I rebuild it, the ports will be in the back.

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  8. Agree, foam was just an example, many other materials can be explored.
    But a sealed 2031 with no diffraction should be amazing...

    I have one more idea which I came up with recently which though pricing wise would be higher than something like 2031A but would end up mimicking genelec 8260 or a TAD compact reference
    Basically this involves using 2 KEF Q300 bookshelfs (6.5" coax) and keeping them each on top of a NHT super 8 . the super 8s can easily go upto 200 Hz so Q300 will cross to super 8 at 200 Hz . They will also be kept inverted on super 8 for closer CTC. This should be pretty close to 8260 or the TAD compact ref . And coax would behave as a waveguide better due to reduced excursion. And horizontal and vertical dispersion is no worry here...
    Although a pricey combination but maybe a very good one esp for nearfield [ my core objective :) ]

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  9. That set up should work well.

    I was actually thinking about making the B2031P's baffle shape more similar to the shape of the plastic WG/woofer frame. I really want to do large round overs as well. It's a lot of money and work for a little sonic improvement though. However it would make a lot nicer looking speaker! It almost seems like chasing better sound than the Primus or B2031 is a high price to pay for a small (if any) reward. Listening to my ADAM Artist 5 vs. a Primus/B1031P system shows a definite performance improvement in the former, but the price difference is definitely bigger than the performance difference. The bigger difference is actually in the bass--room calibration. 4 subs vs. 2, Audyssey vs Yamaha's calibration, and a better damped vs. a less damped room.

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  10. Makes me feel like I must have been crazy to shoot for better than one if these lower cost options. That said, the 4 subs seem worth it in the long run.

    I'm not saying the midrange and treble don't seem better with the ADAMs, because they do, but it was a couple thousand dollars vs. a couple hundred. The ADAMs also look a lot nicer! My Primus look pretty ugly IMO and are best with the grill left on most of the time. The ADAM look badass with the grills off. I only leave them on for protection and take them off every time I listen to them. The silver/grey look of the Primus does look low rent. The cheap pioneer look better to my eye than the Primus, but I also think they don't sound as good. If my Primus had zero grey, they'd look good enough for me. Still I love the gloss black ADAM.

    For sound though, the difference is there, but it's not really enough for 5-6X the price especially considering home theater use and the fact that the floor standing Primus have less need for a sub.

    Anyway, injustice rambling now.

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  11. Oh, one other thing: perhaps some packing tape over the B2031Ps ports would do the trick. You would probably still need to pack the ports tightly with some wool felt or something. The black wool felt I have in mine looks a million times better than the cotton balls and performs the same.

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  12. But then that would mean possible crossover changes isn't it ?
    Which is why I just thought of "improving" on current baffle shape ?

    and yes I do expect the KEF+NHT setup to be good, but I have the same worry which you mentioned. How good will it be, esp for additional amount spent over a well modified 2030A/2031A. Thats an very very imp question :)

    Btw the new JBL LSR305 has promising measurements and is quite popular as well - see here
    http://www.soundandrecording.musikmachen.de/Magazine/SOUND-RECORDING/2014/5/JBL-LSR-305-308-Nahfeldmonitore-Testbericht

    And you can download for adam artists
    http://www.soundandrecording.musikmachen.de/Magazine/SOUND-RECORDING/2011/9/Testbericht-ADAM-ARTist-3-und-5-Studiomonitore

    Btw now I am bit hesitant to about larger 2-way monitors and now understand the worry related to vertical dispersion [which you mentioned multiple times:) ]
    Thats apparent in the larger LSR308 as well in the above link.

    So 6.5" looks like max to go for, so if Behringer may go for 2030A (with baffle modifications )

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    1. Good thinking--I shouldn't mess with the baffle size much, but larger round overs would be in the works.

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  13. Btw many times Primus 363s are $99 on Amazon , the best option for HT!!! :)
    buy 4 if required and their centre [ or the same 363 as centre :) ]

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    Replies
    1. That's pretty much what I would recommend everyone on a budget should do. They get the sound pretty close to incredible.

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  14. Bw for a fair comparison ( with KEF+NHT ) the 2-way monitor will also need one sub atleast

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  15. Long back ago I think wMax had shared 2030p measurements, the links don't exist now. ( in some posts where you had posted too)
    Do you remember if they were better/same/worse than 2031p.
    The 2030a has 2khz crossover ( same as 2031) and a 0.75" tweeter. Should have wider dispersion than 2031....

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  16. I found those - http://hardforum.com/showthread.php?t=1543769
    THD not so good at 100Hz

    2031 THD can be seen here
    http://techtalk.parts-express.com/showthread.php?224685-Some-first-behringer-truth-measurements/page2

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  17. I also wonder if I can keep 2030A inverted on top of NHT super 8 and also cross them much higher (~200 Hz) for better SQ

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  18. I think few of my earlier comments went missing

    Basically found some measurements for 2030 also
    http://hardforum.com/showthread.php?t=1543769

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  19. I've never done THD measurements, and there no shred of evidence of them correlating to any detrimental SQ issue that I know of.

    None the less, the ones on TT look pretty darn good. I wouldn't get too concerned over them, but I still like the idea of crossing over on the high side with the sub very near the speaker.

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  20. You can definitely hear high(ish) distortion on test tones. That tells me I don't want it--just to be safe. It's really necessary to know what output level the measurement was made--every speaker has its limits.

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    Replies
    1. True, the output level is to be known.

      And yes, irrespective of the mains, the two nearfield (stereo) subs upto 200 Hz looks like the way to go...

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    2. except for large mains like 2031a where one sub crossing at 60hz would be good enough. So no need to keep it near mains....

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    3. Right now at least one night a week I go to dance party level on one of my sound systems. I actually prefer a higher crossover F. I don't know if it is just my OCD or what, but things seem cleaner that way and it certainly doesn't effect imaging much if any at all.

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    4. Not sure how much of that is a fear of frying an amp vs actually hearing bass distortion. Without a DBT... Going with what works for me--going with my gut.

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    5. Part of that is also knowing that once you get past a certain limit, SQ doesn't suffer that much.

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    6. Can't believe I just said that--me of all people. If I didn't have my ADAM/Canton/Marantz system, the quest for the ultimate system would still be burning in my soul. Right now I'm listening to FM with simulated SS and loving it! I would have thought that impossible 1 year ago.

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    7. Well thats true, once you go below or above the certain measurement numbers its beyond audibility.
      Doesn't matter if one falls from 1000 ft or 10000 ft :)

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  21. "ones on TT" - you mean the 2031A's ?

    btw, though one can't really compare across, here are Q300 ones just FYI
    http://www.audio.de/testbericht/im-test-kef-q300-1145180.html

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  22. I thought they were the 2030s? Maybe I misread.

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    1. The ones on PE forum post are 2031A, and the lower distortion due to 8 incher is apparent. Just psychologically, feels nice to have HD numbers below 40 dB :)

      The ones on hardforum are 2030P which come close to -36db and would need the high crossover subs. 2030A should measure same.
      2031A will not even need a sub! confusion :)

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  23. Listening near field, HD should not be an issue for any of these speakers. The 2031 are pretty big for a desktop. By pretty big I actually mean huge ;)

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    1. True, though only advantage I see ( if I can fit them on desk and listen on tweeter level) is I need not bother buying a sub, or maybe delay that for much long time. Based on the FR on the PE post, they go very low and cleanly... only thing remains is diffraction correction which we discussed earlier (true even for 2030 though)

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  24. That's pretty much it. I really need to measure what happens if I smooth the baffle out. Keeping the output from the ports would be nice(r) for a no sub setup.

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    Replies
    1. Do blog if you have any updates with baffle experiments. You tried the simple tape over ports ? Or bung instead of cotton...
      Then measuring the F3 will let know if sub is still must (sub will good though)

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    2. Unfortunately I won't have time this weekend. :(

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  25. I will. I should have done it a year or more ago. Hopefully this weekend. I'll do some ground plane measurements for the low end change(stuffed and taped vs. unstuffed).

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    1. Much appreciated! Thanks!

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  26. Don't thank me yet--I haven't done it. :) I do hope to do it. I also hope to perfect my girlfriend bass in the HT.

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  27. 2 HT related questions :

    1) Do you find 7.1 real beneficial over 5.1 ?
    2) Since you listened to both, what do you think is better for HT : 5 x P363 or 5 x 2031P ?

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  28. 5 x 2031P has one WAF advantage . They can be hidden behind acoustically transparent screen and all can be mounted on wall :)

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    1. If you are willing to do the work or pay for it. At that point, I wonder if there are better in wall options?

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    2. Hmmm,
      And will 363s work ok close to wall or they are better off being few feet away ?

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    3. I think it would be a bad idea to place any broad dispersion speaker near a wall unless you were going to place it in a wall. The VERs will color the sound. I have theories on that, but they have yet to be adequately tested.

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    4. I guess Behringer went with front ports so it can be soffit mounted. But the passives would have incorporated the bsc, so i guess crossover would have to be reworked to put 2031p behind screen (assuming its side wall to side wall)

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    5. I'm betting they did it because the Genelec 1030A did it.

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    6. As far as BSC goes, I think you'd still need to measure to know what's best at the listening position. Bass in small rooms is complex.

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    7. But crossover will still need to be changed/tweaked.
      The active ones have that option via a switch (the bigger problem is finding cheaper av pre if using actives for HT)

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    8. I'm not sure the crossover would need tweaked.

      What changes are you referring to?

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    9. I meant chgs related to bsc in passive crossover network, unless one can tweak that using external EQ

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    10. Yea, a BSC filter of any sort may be better or it may be worse. Without measurements your sort of flying blind. Ultimately, bass EQ, and a multi band parametric is typically needed.

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  29. I've never actually tried 7.1. Not many people actually do.

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  30. I'm not really sure which of those is better sounding. I'd say the Primus if you didn't want to modify the B2031. The thing I really like about the Primus is that it is a floor stander. It eliminates the stand and just makes a more stable and lower cost speaker option. If you have kids and dogs it becomes much better! My biggest gripe with the Primus is how they look with the grill off.

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  31. You mentioned in wall options earlier. Aware of any good ones ?
    Though I doubt measurements will be available

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  32. I'm not sure if there are any good ones available in the USA. I'm pretty sure there are in Europe

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  33. Again about HT, do you see an advantage of having large mains so that one can cross a sub at 60Hz or below or one can safely cross at 80-100z (in a medium 22' x 14' room). If the latter, one can go with wall mounted 5.25-6.5" speakers .And spend more money on 3-4 12" subs [ primus 363 at 99$ is an exception :) ]

    Also you indicated earlier that the primus PC351 MTM being a promising option. Whats about its driver layout you think makes it promising...

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  34. I actually don't see much of an advantage if any at all. I always end up crossing my speakers over higher than that and never hear a reall loss in localization or imaging. The only advantage I see is not having to but a stand that will not be as good as a tower speaker. Theoretically, there is an advantage, but in practice it's not a big one.

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  35. The 351 doesn't have a front port. Other than that I'm not a big fan of the driver configuration. I want my drivers aligned vertically.

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  36. And what would be ideal dispersion pattern for HT . With multiple speakers in small room, is narrow better... ?

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  37. My ideal would be narrow--but I couldn't say that would be better.

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  38. Bit OT : Not sure if I mentioned this -
    http://www.amazon.com/JBL-Studio-230-Bookshelf-Loudspeaker/dp/B00GJXSWZW

    This speaker from JBL has a crossover of 1.1 kHz (I confirmed with their support as well ). Pretty unusual for its size...

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  39. Holy cow! That is an interesting speaker.

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    1. More of passive version of LSR303/308 all of which are similar to their flagship M2...

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  40. PSB speakers should also be hi on your list of looking for great speakers. Several rear ported waveguided speakers.

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    1. Ok.

      As of now have narrowed the list to JBLs (LSR305 or the above studio 230) , the Behringers and the KEF Q300

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  41. The JBL look good to me. So do the KEF. I just don't want to have to fiddle with a speaker after I buy it. I may want to fiddle with those as well, but I've never measured them...

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    1. Makes sense. No fiddling is best, in that case JBL LSR305/Studio 230 and Kef Q300 are best. Later , as I mentioned earlier, i will look at adding 2 nearfield subs for KEFs as they will benefit a lot from highish crossover. For JBLs a single sub,upto 80 Hz, should be enough.

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  42. I think I'd probably choose the JBL... The KEF still have a front port and that means I need to fix something right off the bat.

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    Replies
    1. KEF does provide a bung . That should help isn't it ?

      Regarding 2031P : Anything special about the waveguide shape ? If it can be exactly replicated on a larger scale (say to match a 15" woofer) should be one amazing DIY speaker...

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  43. The bung should help, but how flat/smooth is it one the baffle?

    The best WG I've measured is actually the Mackie.

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    1. "but how flat/smooth is it one the baffle?"

      didn't get...

      Is Mackie WG shape geometrically a sperical cap ?

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  44. So does the bung nearly disappear when installed in the port?

    I'm not sure what you mean by spherical cap.

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  45. Basically I wonder how can one replicate the hr624 baffle, but on larger scale (equivalent to 12" or 15" woofer)

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  46. after a long time :)

    here are some detailed measurements for q300 from a german website. What do you think ?
    https://www.hifi-selbstbau.de/testberichte/fertiglautsprecher/411-kef-q300

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  47. Have both Q300 and Q100 attached here

    http://techtalk.parts-express.com/showthread.php?246359-Kef-UniQ-6-5-quot-vs-5-25-quot&p=2070580#post2070580

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  48. The Q300 looks pretty good--perhaps as good as any?

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  49. Should be pretty good for PC setup , isn't it ? (have already purchased Emotiva mini x a100)

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  50. It should be. I had some pretty bad luck with the Emotiva gear. Hopefully that's not a buggy model.

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  51. Hope so :)

    You finished your garage spk ?
    Many have reported the Behringer 212XL/215XL to be quite good...

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  52. I haven't even started one yet. Just can't get free time any more. :(

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  53. After long time :)
    And I am yet to purchase my nearfields :):)

    Btw I was comparing the relatively small NHT classic 3 3-way bookshelfs with some of the best of the KEFs and they seem quite good horizontally.
    Seems to have wider dispersion than KEFs, though its vertical is obviously not as good, but should be enough ?
    A foam "moustache" is also included to address dips in tweeter response at around 7kHz


    http://www.soundstagenetwork.com/measurements/speakers/nht_classic_three/
    http://www.soundstagenetwork.com/measurements/speakers/kef_201-2/
    http://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=941:nrc-measurements-kef-ls50-loudspeakers&catid=77:loudspeaker-measurements&Itemid=153

    http://www.stereophile.com/content/nht-classic-three-loudspeaker-measurements#kXSWUg6KsQSf0LfZ.97
    http://www.stereophile.com/content/kef-reference-2012-loudspeaker-measurements#FAop6x5YVWghQF3l.97
    http://www.stereophile.com/content/kef-ls50-anniversary-model-loudspeaker-measurements#p50c3ITehsCYwCuF.97

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  54. I like the design of those NHT! The matching sub looks interesting as well. Good find.

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  55. you mean classic 10/12 ? Those are discontinued .
    Though I wonder, if in nearfield, I will need a sub..

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  56. Specifically the 10. "Need a sub", probably not. "Want", definitely. ;)

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  57. Btw, just to confirm , you see any issues with vertical polar of classic 3s ? ( there stereophile review has it)

    About HT setup ? I am just confused as to what db level should one shoot for ? Ref level just sounds too much to me [ pun intended :) ]. In my living room (22’L x 14’W x 10’H) at a distance of 6ft from spks, even 80 was loud to me, 105 peak will be just too much, eve if transients (probably no issues in dedicated and treated HT room). The SPL target dictates the speaker sizes to be used, esp to keep it discreet in the living room as well have smaller speakers behind an AT screen.
    Though for subs, shooting for bit more would be needed to compensate for equal loudness contour
    I am wondering if 5” 2way is enough for side and surrounds and 6-8” 2 way for LCR (say classic 3 though its low sensitivity is not beneficial here)

    What kind of setup do you use for HT ?

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  58. It's always difficult to read stereophile's vertical polar response graphs. From what I can tell though it certainly doesn't look great.

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  59. In my HT I use the ADAM ARTist5--3 across the front. It's plenty loud enough for me at 6 ft. I've never heard them even strain.

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