Page 3 of 9 FirstFirst 12345 ... LastLast
Results 31 to 45 of 126

Thread: DEEPER BASS: D. B. KEELE/E-V's STEP-DOWN MODE

  1. #31
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Hi Richard,

    I spent some time to summarise the article as you omitted factual information relevant to Jbl forum members.

    My intent was to provide a clear view of the article.

    My feedback and opinion;

    You omitted key facts concerning the article making the thread impossible to follow and you appear very confused in your postings.

    I asked my wife could she understand your posts?
    The response “what is that?”

    Can you please structure your points like an educated adult so we can understand the purpose of your posts.

    Enough said

  2. #32
    Senior Member Lee in Montreal's Avatar
    Join Date
    Sep 2010
    Location
    Montréal
    Posts
    2,487
    Wondering where all this will lead us... Any build or projet we can expect to see?

  3. #33
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Hi Lee

    Good point

    Hence my request to Rob for some relevance and benefit to our forum member on the 2269 woofer as an example .

    We all know the B380 and B460. The w1500 is NLA

    So it means something useful as in a modern obtainable Jbl driver with decent Xmax and power handling.

    That is a plus if we can make use of it.

    As for the Ev step down or the Keele b6, it’s not new or a biggie and frankly the math behind it is mundane.

    BassBox Pro can spit out what we need with Robs skills.

    Only a few manufacturers did anything with B6 as a step down for a main full range system (domestic) and that was before HT subs became popular.

    IMHO I don’t see the point unless designing a new Jbl sub as a project or a group buy

  4. #34
    Senior Member Lee in Montreal's Avatar
    Join Date
    Sep 2010
    Location
    Montréal
    Posts
    2,487
    Wanna reduce your box size by half? Then simply fit two woofers in the same box half the usual size in isobaric configuration and obviously feed the box with twice the power. If the goal is to please the lady of the house or your "life partner" with a smaller bass box, then consider the job done. I feel that this kind of topic gets sterile pretty quickly if it doesn't end up with an application. ;-)

  5. #35
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Hi Lee,

    Totally and nice to see you posting in this thread.

    The isobaric would be one mean sub with a big crown amp hanging off it.

    Unless you have dedicated man “cave “ the WAF is a barrier to execution.

    I still recall watching years ago a B460 suck the life out of a 250 watt amp and it shut down.

    This stuff is fun

  6. #36
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,170
    Just to be complete here is a 2235 set-up for extended bass vs a B380 Yeah doing this with the newer drivers makes more sense especially with the availability of cone kits becoming questionable

    Rob
    Attached Images Attached Images  
    "I could be arguing in my spare time"

  7. #37
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Location
    Canada
    Posts
    1,626
    Hi Robh, (RE POSTS # 26, 27)

    Thanks for posting the enlarged plans, which include a little more details, response curves and data of the 12 cu. ft. box. Kramer/Timbers do refer to that box in their article, first as a classic sixth-order alignment (P. 4), then in "Alternative Designs" on P. 6 along with smaller size plans shown. However, your post adds the response curves for these designs as well as the computer generated tables of performance. Not really the box-size for me though.

    I tend to think one has to have endless space (I don't have), be pretty fanatic or really "switched-on bass" as John Hoge titled his 1976 subwoofer article (21 cu. ft./almost 600 liters!), especially when considering GROSS/NET volumes involved...

    In the near future, I will be covering in step-down stuff, a commercial E-V box of 76 cu. ft./net weight of 550 lbs !! , 8 ft high, 4 ft wide, 32 in. deep. Driver originally presented for "home" use if I'm correct. Old enough to remember? I do... Try to get that into a somewhat normal living room!

    As for the BX 63 Instruction Manual in post # 27, thanks for that too I saved it on hard disk as I do for all JBL/E-V stuff of interest. After looking at that manual, I note it also does not address the unexplained "loose ends" in JBL's own "step-down" story. I'll just have to "play it by ear" as they say, when time comes to provide some credible or logical explanations on some of the issues involved. Like I tried to do in post # 24 and others. Regards,

    Richard

  8. #38
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Location
    Canada
    Posts
    1,626
    RE POSTS 31-35 I WILL LIMIT MY COMMENTS TO THE FIRST PARAGRAPH:

    Well, look who's talking. Blaming the "messenger" when you can't contradict the facts, the usual. Then Ian and Lee should do themselves a favor and look elsewhere or start their own Isobarik configuration thread. This would alleviate their "suffering" in reading or following this one it seems, which they're not obliged to do. Then we'll see which thread is more confused. Purpose? Very well mentioned in the first paragraph of the Intro (post # 1), and since nothing was mentioned about it leading to a specific project box, you might as well turn the page and leave now. P.S. I don't need to use my wife as an excuse to desperately try to sustain my writings, nor to defend myself...

    For others, during spare time i'm in the process of compiling the large amount of applications data to be presented here, in a few installments, regarding E-V's own step-down mode applications as I mentioned in post # 24, and considering what I then said "E-V's peak boost frequencies are "all over the map"...". In APPROXIMATE B6 alignments (JBL's 12 cu. ft. assisted box was called in the article a CLASSIC 6th order alignment), the "beauty" is the peak boost filter does not necessarily have to be precisely at Fb, contrary to what JBL SEEMS to have done in its modelings (though there appears to be some unexplained "looses ends" in their method/application, as mentioned in post # 24, that other members haven't yet tried to explain logically). Naturally, there are possible reasons and consequences for E-V's frequency choices some > 5% tolerance! (e.g. driver capability, excursion, distortion?) which we'll try to address, in the absence of clear explanations found.

    For those who may think I'm too hard on JBL and that I may be nothing more than an E-V fan, wait they'll get their kick in the butt too... (starting right here with the above-mentioned "some > 5% tolerance! " which is THEIR number re peak boost being sufficiently close to step-down Fb to provide no significant performance compromise...)

    Richard

  9. #39
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Location
    Canada
    Posts
    1,626
    Hi Robh, RE POSTS # 29 & 36

    Had a quick look at these posts. Seems to me you're being unfair to 2235H in that comparison. I don't own it so have no interest in defending it. But in all fairness for the driver one must compare apples with apples as you have done with 2269. In the 2269 comparison same box size 8.8 cu. ft. is used and same QL number. However, in the 2235 comparison one box is 7.2 cu. ft/Fb 22 hz and the other box is 4.5 cu. ft. with no QL number given. In the former much larger box with pretty low tuning this is a scenario where the 2235 is destined to run-out of steam anyway (being overstretched), in my view. So the dices seem to be loaded against it... It would appear more fair to do as in the 2269 case, meaning same box size in 2235 comparisons, along with same QL, and a more acceptable Fb around low 30's for unassisted box. Regards,



    Richard

  10. #40
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Location
    Canada
    Posts
    1,626

    Deeper bass - bx 63 - addendum/clarification




    Going back in some JBL documents to check some wording this time, instead of specs pages, I think I've found the "missing link" to make this BX 63/63A usage thing logical here regarding "Step-Down Mode "VS B380/B460, 12 cu. ft. filter assisted box in Kramer/Timbers article (plus large size plans by Robh in this thread), 5233A, 5234A and 5235 crossovers. Lets sort out that below.

    The BX 63/A is really a dedicated "single usage" device for B380/B460 original speakers (and exact clones too!). This is revealed by the following quotes:

    "The response of the BX 63 has been specified by computer for the B460 and B380... Any other network considered for use with either system should exactly duplicate this response curve. Beyond its unique suitability as a dividing network for the B460 and B380, the BX 63..." (JBL, Low Frequency Systems, B460/ B380/BX 63, P. 3, Document LFS/ 5-83). BTW that doc. date is pretty consistent with that of the Kramer/Timbers article considering normal writing/publishing delays. These quotes are pretty clear.

    Now, on to the 12 cu. ft. filter assisted box. The above stock BX could not have been used for that box's 20 hz lower tuning, since the BX's peak boost frequency is at 26 hz, as mentioned in the Kramer/Timbers article and also in graphs posted by Robh here in post # 5.

    This is why in post # 24 I wrote: "the only explanation I may see is CUSTOM MADE BX?: "We would also like to thank D. B. Keele Jr. (JBL) for his kind assistance with the computer. His efforts made the special voltage drive of the BX 63 a reality." I purposely underlined the word "special", since Kramer/Timbers had already mentioned "...Model BX 63 which was chosen for this application because it was designed specifically for the present combination of driver and enclosure." That application and present combination of driver and enclosure was the B460 equivalent they presented extensively, but later in the article they added other offerings like the B380 equivalent that "requires the same equalization" as they said (P. 7).

    The stock BX 63 they already had for their "B460" project box, so nothing special there. However, I'm pretty sure from the above what D. B. Keele (then working for JBL) did is custom-design a "special", though similar, filter for the 12 cu. ft. box with a peak boost at 20 hz this time (P.6) instead of 26 hz. That 20 hz filter is also special in the sense that, to my knowledge, it has not been commercially available from JBL like the usual 26 hz BX. I didn't find any trace of it, other than in the Kramer/timbers article. That should put the 20 hz filter issue to rest, except for what should I do if I want a JBL 20 hz peak boost filter? The 5235 crossover does have such a filter, as well as the 5234A, both being two-channel devices, and if I remember correctly the one-channel 5233A may also have such a filter.

    This leaves a few other applications issues to discuss briefly. Can the BX 63 be used with other speakers than those mentioned above? Possibly yes, if the step-down box tuning frequency is close to the BX peak boost frequency and the woofer has enough LF "steam". Close means Fb equal to or a bit LOWER than BX 26 hz which implies the latter will be equal to or a bit HIGHER than Fb. Its much preferable to avoid having the BX boost at less than box Fb since a vented box starts unloading the driver below that frequency, with increased excursion/distortion, imagine if you add a bass boost below Fb on top of that, its a recipe for driver damage. {In the forthcoming application examples that I have from Electro-voice there are two similar boxes in which E-V applied the peak boost a bit (3 hz) below Fb! But these are Engineer designed with computer modeling so they know what they are doing}.

    As for 5235/5234A such applications, the peak boost frequencies are at 20, 30, 40 hz which seems convenient for a number of applications, as long as you play it safe, and keep boost frequency equal to or a little ABOVE box Fb in your own applications... A little above Fb has minor lesser deep bass consequenses, which are far better than the other way around with a busted driver...

    Richard

    EDITED FOR MINOR TYPO CORRECTIONS

  11. #41
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,170
    Can the BX 63 be used with other speakers than those mentioned above? Possibly yes,
    With DSP you can borough the idea from it and adjust Q and Frequency as required for a specific application or just use DSP to mimic a BX-63 if the requirements are the same. DSP has essentially made any of these dedicated analog boxes obsolete. Especially as far as subwoofer applications are concerned as many contain multiple EQ filters for adjusting the in room response to deal with primary room mode issues.

    Rob
    "I could be arguing in my spare time"

  12. #42
    Senior Member Lee in Montreal's Avatar
    Join Date
    Sep 2010
    Location
    Montréal
    Posts
    2,487
    The Linkwitz Q transformer can indeed now be easily applied (and modified) in the digital domain. Rendering most of the "old boxes" totally obsolete except to collectors. I sold my old Kef Kube 200 Linkwitz Q transformer as soon as I got my DSP many years ago.

    https://www.minidsp.com/applications...witz-transform

  13. #43
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    The Bx63 can be modified to other F and Q but would require invasive modifications to change out parts on the pcb. They are so rare why would you do it?

    Probably not the easiest approach

    If analogue is your only option and you can solder this link could help

    http://www.ska-audio.com/diy/BassXt.html

    (This engineer previously worked for Mark Levinson and the pcbs are first rate)

    I agree the dsp particularly if in the power amp is a far more flexible and easier solution for diy

    Below is the 1200 watt Dayton amp with dsp.

    http://www.daytonaudio.com/index.php...er-wl-dsp.html

  14. #44
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Location
    Canada
    Posts
    1,626

    Re posts # 41 and 42




    Even though DSP in your Crown amp was mentioned in earlier post(s), it remains an actual and relevant topic.

    No doubt DSP is the new or modern way to fly. Agreed, nobody in his right mind can deny that. However, to me this doesn't automatically mean older stuff suddently all disappeared or was scrapped, based on what I see here in some threads. There's still quite an interest from folks for older JBL gear whatever it may be, even non-collectors. Right or wrong, I do sense some nostalgia right and left... I tend to think there are probably still quite a few BX/5234A/5235/etc. out there, or being looked after.

    RE BX 63, 5234A, 5235 and/or many other examples, obsolete? Yes and no. Certainly NLA in many cases, but still sought by some and for the many who happen to have one in good condition it can still continue to do the job right even in a changing world to DSP. Am I getting rid of, for example, my original analog Mackie mixers in nice condition, from the time Greg Mackie made them (20+ years!), simply because the new trend is to digital mixers? NFW (sorry for that). Not until they die on me... The newer "el cheapos" are not worth that.

    Changing for changing, or because its more "fashionable" ? The newer DSP equipment does offer more flexibility in many cases, which I happen to like, but as for quality, reliability and "built like a tank" I'm attached to, its very questionable in this world of cheap and disposable stuff... e.g. my oldest EQ was purchased in 1979 and still works like new. The "damn" thing just don't want to die! I only cleaned once or twice an in/out switch with Caig's Deoxit in almost 40 years of ownership! Should I dump it just for the sake of it, or because I already have a replacement model on the radar? If it does the job right, what's the purpose?

    Lee mentioned having sold his Kef stuff, no problem with that re flexibility, but I understand on the other side of the equation there was a buyer for that which logically wanted it to use it. Hence my point in the first paragraph. I'm not against DSP at all, nor convinced that DSP suddently made all older boxes only good for the dumpster, considering what I see around this Web site. When a piece of equipment dies on me or is really obsolete (e.g. incompatible, etc.), for sure newer technology will replace it, and that's OK.

    EDIT: I seem to recall that member BMWCCA mentioned in the past on this site having Crown D series amps for some 35 years. Should he replace them with newer digital amps with or without DSP? Tough call isn't it? Cost/benefit approach then? Still tough. I also remember reading on Bryston's web site some time ago that their 20 year warranty did not apply to digital equipment since they didn't have enough reliability experience, data or maybe faith in it? Can't remember the exact words used. Add to that today's lowest-cost manufacturing practices in general, its scary.

    Bottom line, analog or DSP the LF peak-boost frequency rules remain the same!

    Richard

    P.S. To Robh, out of curiosity, when you modeled the 2269 in Bass Box (post # 29) you used filter Q 1.5 instead of the usual Q 2 for step-down filter. Any specific reason, like driver or software limitations?

  15. #45
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,170
    P.S. To Robh, out of curiosity, when you modeled the 2269 in Bass Box (post # 29) you used filter Q 1.5 instead of the usual Q 2 for step-down filter. Any specific reason, like driver or software limitations?

    Because I got too much of a peak @ 26 Hz with a Q of 2. Better overall response curve using 1.5. In a modern DSP set up you just type in the Q you want. For the older analog boxes you need to change out parts to make the mods. For what's it's worth I use a BX-63A on my stereo B380's and use the DSP in my amp for my LFE subs. I also use older PS 200 and 400 crown amps in my HT set-up. I have quite a mix of modern and "vintage" gear in that set-up and they all seem to play very nice together.

    Rob
    Last edited by Robh3606; 02-03-2018 at 08:47 AM.
    "I could be arguing in my spare time"

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Early 80's Don Keele & Mark Gander / JBL horn plans
    By Mike Caldwell in forum Lansing Product DIY Forum
    Replies: 4
    Last Post: 04-30-2014, 07:18 PM
  2. D.B.Keele.Jr's
    By stephane RAME in forum Lansing Product General Information
    Replies: 0
    Last Post: 04-12-2010, 11:52 AM
  3. Step Response
    By Robh3606 in forum General Audio Discussion
    Replies: 17
    Last Post: 02-09-2009, 05:14 PM
  4. Resurround Step-by-step
    By boputnam in forum Lansing Product DIY Forum
    Replies: 43
    Last Post: 01-21-2008, 09:23 PM
  5. Resurround Step-by-step
    By boputnam in forum Lansing Product Technical Help
    Replies: 31
    Last Post: 12-25-2005, 03:26 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •