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Thread: What to do with my 4699b

  1. #31
    Senior Member Val's Avatar
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    Quote Originally Posted by RMC View Post
    Hi Val...
    Richard - thank you for running those calculations!

  2. #32
    Senior Member Lee in Montreal's Avatar
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    Sadly, tuning a box so high at 55Hz means that the driver will unload under that frequency. Over excursion at high volume. Considering that the driver has an FS_30, that would be a waste of a good driver for home duty. I'd think that if the max cab volume allowed in the living room by wifey is 3,5cft, perhaps another driver shall be used. Lets not forget that JBL's data are for SR, not necessarily sound reproduction. Tuning to 55hz means lotsa of boomy bass and no bottom end. Fine at the Barmitzvah or basement party, but perhaps not the best sounding. ;-)

  3. #33
    Senior Member RMC's Avatar
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    Hi Val,

    Lee should re-visit his vented-box knowledge. Any vented box will start unloading below tuning frequency, wether its tuned at 30 hz or 55 hz. This is why a high-pass filter somewhere below Fb is always recommended in using a vented vox, to minimize risk of over excursion.

    An Fs at 30 hz in itself is almost meaningless if not associated with other relevant parameters such as Qts and Vas numbers which impact box size. And this is a good example with woofer Qts of 0.20 often leading to smaller boxes. The E-155 is not subwoofer class material for sure.

    The objective here was to try to save the woofers in the context of Val's requirement of smallest box possible. SR is a form of sound reproduction as opposed to sound production.

    Tuning at 55 hz lotsa boomy bass?? Lee should run some curves for himself in Winspeakerz or Win ISD Pro to verify his pretention... Bass does appear pretty flat in the software with that cab size and tuning. And, BTW, Win ISD author in the help files of his software and John Eargle of JBL (see * below) both indicate that modeling of a driver in software using T/S parameters already assumes one boundary (Half-space or 2 Pi) radiation into the room ( ground or wall placement). So no additionnal room reinforcement of the bass for such speaker placement alone, than what predicted by the software. More often than not, a single boundary speaker placement is the usual way its done.

    In posts # 16-18 and # 26-27 Martin Wu has an opinion quite contrary to Lee's about the sound of these boxes. As for bottom end, it's knowingly limited by Val's box volume as indicated in post # 29...

    Richard

    * John Eargle, Loudspeaker Handbook, Chapman & Hall, 1997, P. 58; Handbook of Sound System Design, ELAR, 1989, P. 106.

  4. #34
    Senior Member RMC's Avatar
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    Hi Val,

    I also did a quick modeling of the E-155 in a 3.1 cu. ft. box tuned to 55 hz, using Win ISD Pro 2016 Edition with QL 7 as the usual box loss assumption, and here again there is NO bass bump in the low end. In fact, not only is the response quite reasonably flat, but it drops in the low- end a bit faster than with Winspeakerz.

    Instead of the - 3 db @ 58-9 hz in Winspeakerz, WIN ISD gives me -4 db @ about 59 hz. Quite close from one software to another. As long as one compares apples with apples using QL 7 box loss in both programs as I did. So my post # 30 is still valid...

    However, with regards to vent length (Winspeakerz: 2 X 5" dia. vents 6.167" long), WIN ISD gives longer vents for 2 X 5" dia. vents: 7.58 inches long. The difference may be explained by the different vent length math formula each software designer used. Therefore, my suggestion is to start with the longer vent lengths and reduce them by cutting- off small portions as need be to reach the target Fb. If you end-up with an Fb of say 57 hz don't lose sleep over that, WIN ISD tells me response will be even a bit flatter in the bass range... (up to Fb around 59 hz).

    You can check box Fb by running test tones (e.g. 70 to 50 hz) to the woofer when the speaker is almost finalized and putting a finger lightly on the cone near the surround to feel which test tone frequency leads to least or no cone vibration, that corresponds to box tuning frequency (Fb).

    You can seal temporarily around the vent on the inside of the box with modeling clay for example, while doing your Fb tests and when you get the result you want then replace the clay with permanent silicone around the vent on the inside of cabinet. Air- tight boxes (except for vent) are a MUST HAVE here.

    BTW there are tons of ready-made Sound Reinforcement boxes on the market from known manufacturers with an F3 around 55-65 hz, including many with 12", 15" or 18" woofer in two or three-way configurations. Yours would certainly not be the odd ones. My previous EQ (with high-pass filter) and/or placement suggestions also remain relevant if need be. Regards,

    Richard

  5. #35
    Senior Member Val's Avatar
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    I appreciate the comments and calculations. For now, I'm planning on working on a cabinet design with no less than 3 cu ft for the E155...hopefully a bit bigger.

    I do have a question about the 2342 horn mentioned below. I see they take the screw mount and my 2425 is a 3 bolt mount. Is there an adapter or a different version of the 2342?

    Thanks,

    g

  6. #36
    Senior Member RMC's Avatar
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    Hi Val,

    Your cabinet size MUST be (not hopefully) larger than 3.1 cu. ft. (net volume needed) to account for box air volume displaced by woofer, bracing, vents, etc (excluding soft fiberglass wool for example lining interior of box) otherwise your NET volume will be too small to deliver the performance the software modeling predicts...

    As for your question, I don't have an answer at this point.

    Richard

  7. #37
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    Have you tried these with any tubes? Mine sound great with 6v6's or el34's.

  8. #38
    Senior Member Val's Avatar
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    Quote Originally Posted by dezmond View Post
    Have you tried these with any tubes? Mine sound great with 6v6's or el34's.
    Sadly, no tube amps here

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