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  1. #91
    Administrator Robh3606's Avatar
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    Apr 2003
    Back to the fun stuff has anyone heard a Sunfire sub. You know the 2700 Watt 1 ft square cube?
    Hello Ian

    I have seen them often enough but never heard one in use. So why do you ask as it pertains to this thread?? Does it use a similar alignment?? Always wondered what they sounded like. I have always had a preference for large surface area with minimal movement as compared to small surface area with extreme movement. Not sure why because if the displacement of air is the same it shouldn't mater. The larger cones just seem to sound better??

    "I could be arguing in my spare time"

  2. #92
    Senior Member Ian Mackenzie's Avatar
    Join Date
    Apr 2003
    The Tardis


    I bought it up because of the recent discussion on placement.

    If this thread was a newspaper on the coverage of who will get in next election it would be one side A4 sheet.

    Itís a look through a key hole.

    Sometimes raising product outside of the immediate discussion opens up the mind.

    The beauty of the Sunfire is it can be placed anywhere without hinderance or in multiples across a room or typically in corners.

    Corner placement of 9 cu ft3 or other options is going to be restricted by sheer size. Location and spread of subs is critical to obtaining a worthwhile result.

    Yes itís time to enter the real world. Context is a useful thing when applying theories to reality.

    If you google bass, particularly in small rooms itís well documented as one of the most difficult things to get right if at all. In some rooms their are non recoverable issues that impact deep bass.

    One way around this is to place the sub right next to the listening position. Itís called global.

    The other point is power. The Sunfire is a good example of why you need a line to the local power station of you have a relatively small driver. I donít believe the physics in laymanís terms has been spelt out in a way that makes the notion of the step down tuning real. It hasnít been qualified.

    So before you buy longer pvc ports do some evaluation of your room then look at your woofers.

    Is attempting deeper louder bass realistic?

    Look up REW to find out what is and isnít fixable with EQ of your bass.

    Will my existing box cut the mustard?
    Will step down of my LE8T give me low bass? How loud can l play it?
    What can l expect out of my 4311 in step down mode? What are the pros and cons of attempting the modification?

    The thread has looked at the step down tuning in almost isolation of the realities of reproducing deep bass other than some notable examples of Jbl subs. No factual attempt has been taken to screen or quality existing system or drivers for suitability.

    Then there is the application of home theatre or music?
    I would suggest a lot of people today have blended systems. Those with dedicated HT would almost certainly have existing subs.

    The other obvious but overlooked point in these arm chair style forum discussions is that todayís recordings are nothing like the 70ís when the step down paper was written. Back then it was vinyl or cassette.

    CDs, DVD audio and SACD donít take take prisoners in terms of what bass placed in a recording. The demands on a woofer are much higher. Amps are much more powerful today and will pole a VC.

    I donít think a real scenario exists where you want play a recording with deep bass quietly.
    Anyone selling that is absolutely full of shit.

    Therefore one would hope common sense applies and the user out sources the desire for deeper louder bass to a dedicated sub rather than squeeze a quart out of a pint bottle. It ainít gonna work and many Jbl recones are now NLA.

    Of course some idiot go and do it.

    In summary the usefulness of the content in this thread needs to be well
    qualified. It requires well thought out discussion on the introduction of step down to an existing loudspeaker system and a process for evaluating suitable drivers for a new system or sub.

  3. #93
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    Thanks for coming back again and again, its the best way of expressing that you really like it.

    Making the usual noise, distortion and beating around the bush that doesn't cut it, is quite similar to the guy repeatedly saying this store is real crap but keeps shopping there all the time... even though there are numerous other stores available (like threads). Looks pretty much like "if you can't beat them join them" to me.

    The most important signal is certainly that you keep voting for it everytime you click on the thread's link... to have more than a peek. So as it is the Thread DOES capture a lot of interest otherwise you wouldn't be here, Right? Getting close to 4,000 views isn't bad for an "irrelevant" thread don't you think? Unless they're all your clicks.

    Even though you have all leisure to compete with this thread, for the benefit of all readers, by setting-up your own thread on LE8T/4311 or other step-down process, with your own material and info, but as usual refrain from it. Similar to "bleachers managers" at the baseball game.That says a lot. Of course you prefer to come back here for two reasons we probably know already.

    After all is said and done, the recurring views only confirm there's a lot more here than you like to pretend. Otherwise, others sure would not hang around an "uninteresting" thread on this site. We're all convinced it won't be long before you show-up again as there is other stuff to post, and you certainly can't avoid looking so you don't miss a thing or two that you'll learn, without admitting to have. We understand.

    Thanks again for clicking, and voting for it, one more time, the best flattering expression! We're glad you enjoy this like others do by viewing regularly. Otherwise you'd stay away from it, right?

  4. #94
    Senior Member RMC's Avatar
    Join Date
    Feb 2017

    Some issues re step-down mode


    E-V, JBL (in post # 26 data sheets ) and Kramer/Timbers' article did not provide in their documents cone excursion graphs/curves for the modelings they did. But we can refer to some excursion data provided in some posts here. One must remember there are TWO bumps on a cone travel graph with these B6 or so alignments, one on each side of tuning frequency, whereas the usual vented-box design has one bump above Fb and a continuing excursion increase level below Fb (e.g. post # 11).

    Its interesting to note for these high level curves there is LESS cone travel reduction at Fb with assisted alignment VS conventional unassisted alignment. This is considered to be the result of applying a 6 db boost at Fb or so (subject to further explanation below), which is equivalent to supplying four times the power at that point. However, this lesser cone travel reduction by the vent at that point is somewhat compensated elsewhere with MORE cone travel reduction, below the assisted tuning frequency VS unassisted design. That reduction is the result of the subpassband 12db/oct. high-pass filter included with the 6 db filter boost (i.e. boost/cut filter).

    The excursion bump above the new Fb (in the region of original tuning) may well reach driver excursion limit first because the driver's maximum acoustical output capability is usually reduced by a few db in the region of original box tuning, as a result of lower than normal box tuning. Consequently, more cone excursion there. On the other hand, the excursion bump below the new Fb, a result of bass EQ applied, has a slower rise than with usual vented box, thanks to the high-pass section of the bass EQ filter.

    The older 15" 2235H (Xmax 8.4 mm) in post # 11 illustrates at the 150W power rating with assisted alignment the driver isn't out of bounds, excursion being a bit less than 8 mm on the right cone travel bump, and a bit more than 7 mm on the left excursion bump. Not a lot of loose left, but it doesn't have its back to the wall yet. That slower rise on left bump permits here to add, with an equalizer or DSP, maybe about 1-1.5 db or so of bass equalization around the boosting filter's frequency (Faux), then the driver is about done with Xmax on both bumps at the same time...

    Vance Dickason also produced a computer simulation, in his Loudspeaker Design Cookbook 5th edition, of a Class I sixth-order alignment similar to others in this thread, "... to show the dynamic consequences..." of such. He used a 12" woofer (Qts 0.30) in a QB3 aligned vented-box, that he tuned at 24.8 hz, used an active filter frequency of 27.14 hz with a Q 1.77, giving a bass lift of 5.33 db.

    So Dickason's boost was applied 2.34 hz above Fb, similar to Keele's and many of E-V's own boxes. Comparing his F3 numbers with/without filter shows the expected 10 hz F3 gain from assisted alignment (and the predicted half-octave extension). With regards to cone travel he writes: "Excursion only 5.8 mm maximum for the speaker/filter combination, plus the typical continuing increase in excursion rate below Fb has been attenuated to a low level. Given the 6 mm Xmax of the driver, the Class I system should provide good high SPL performance." (P. 63).

    Also interesting from this simulation, are its cone excursion curves (btw similar shapes or so at higher level to 2235H's in post # 11). At the same low input power level the pre/post bass EQ excursion curves match more closely at Fb. But as the level increases they deviate more from each other at Fb (and elsewhere). Since the boosting filter is also present on the low level post EQ curve, and there's a relatively good match of curves at this level at Fb, then why less at higher level? As if the vent's cone travel reduction effect at Fb (and others) couldn't keep up with more input level.

    E.g. On "" one fellow that went the B6 way did mention "... and made port noise a big problem." No box, driver, port or power info being given its hard to even try to name the culprit with any reasonable accuracy.

    It seems the bass EQ filter's sole presence/action, which is independent of power level, doesn't explain everything at higher level. Some Port compression also? There's a coincidence: as power input increases the shape of the post EQ excursion curve changes, and as power rises so does port compression according to Salvatti, Devantier and Button's Port Performance article I mentioned re port size in a previous post. They say:

    "As the SPL of a port is increased, there is no escaping some degree of port compression." (P. 32) "Several complications occur in vented designs as the output is increased beyond the point where the air in the port is able to respond in a linear fashion." (P. 19). Examples given: extraneous noises made in the port, acoustic compression and distortion. Some food for thought regarding the above-mentioned issue.

    More coming with other drivers.


  5. #95
    Senior Member RMC's Avatar
    Join Date
    Feb 2017
    A parenthesis regarding speaker/subwoofer placement mentioned in some previous posts.

    Floyd E. Toole is THE person to go to for this: from The Science of Audio series of Lectures, "Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3 - Getting the Bass Right", from Harman's V.P. of Acoustical Engineering! He's been with JBL for many years, is a world- renowned expert on speaker acoustics and knows more about this than almost anybody else. Relatively easy to read, follow and understand, the form is similar to that of a presentation with boxes/illustrations on the left, and short explanations on the right hand side of the page. Google this as its on the Web for free and worth it! If you can't find it let me know I'll post it.

    For those wanting a more extended view/explanation on the subject, from two other Harman Engineers : Todd Welti and Allan Devantier, "Low Frequency Optimization Using Multiple Subwoofers", JAES, May 2006, p. 347. Available free on Harman's Web site in the technical papers section where I took it, if I'm not mistaking. Naturally they do discuss some single sub issues also. Even though its from the JAES, there is still a good part of it that is accessible to all.

    Like Floyd E. Toole, in addition to being an Electrical Engineer Todd Welti is also an acoustician. ALL these fellows here are practicing JBL Engineers, not theorists hidden in some University department. They know what they're about in real life. There are numerous others available on the Web, however the above two papers from well-respected sources should put you in business...

    My next post is about 75% completed, so it should be here in a short while. Regards,


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