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Thread: LE14A Project: Enclosure Design

  1. #1
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    LE14A Project: Enclosure Design

    I sat down at the puter today and got started on my LE14A project. My goal is to improve upon the S99 using the LE14A's in a 3-way system. I had originally thought that I would modify the existing enclosures but have since settled on building new cabinets, saving the old ones for sake of comparison between original and modified.

    The new enclosures will have the same intenal volume as the original S99 taking into account the added midrange/enclosure and additional bracing so the external dimensions will be slightly larger. The front baffle will be in two sections, woofer section and mid tweeter section. The woofer baffle will be permanently glued in place, the mid/tweeter baffle will be removable allowing me to experiment with other drivers.

    To make room for the additional midrange driver, I reshaped the port into a rectangle and placed it at the bottom so that sides and bottom of the cabinet form the sides and bottom of the port, simplifying its construction.

    This is just the first step. Any comments or suggestions are welcome.

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    Hi Bedrock from Hood Canal'

    I'm curious as to why (since this is a new construction) you didn't make the box a little taller and put the HF and MF on the same vertical plane instead of horizontal? I always did wonder why JBL didn't make a larger sized "bookshelf" with the le14 rather than a 12. Maybe they did and I just didn't know it.

    Have fun
    Ed
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    Administrator Mr. Widget's Avatar
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    I’m with Ed on this.

    Aesthetics aside, if you can get the tweeter up to standard seated ear height, or about 39” above the floor, you will usually find that as an improvement. Also, all things being equal, vertically stacking the mids and tweeters is typically preferred to help control off axis response.


    Widget

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    Administrator Robh3606's Avatar
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    This is what I would be building mirror imaged though L240ti Silly starting with a clean slate to not just go for it.


    http://www.lansingheritage.org/image...-ti/page07.jpg


    Rob
    "I could be arguing in my spare time"

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    My original plan was to modify the S99 baffles to accept a tweeter and mid, so I simply used the original size and shape for the new enclosures, but this is just a starting point. I'll layout a cabinet with tweeter and mid oriented in a vertical plane. I'm curious, why do speakers like the 240Ti have the tweeters and mids offset from the woofers?

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    Senior Member Don C's Avatar
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    There is a small response anomaly caused by the diffraction or reflection from sound traveling across the front of the baffle and meeting the edge. The frequency of this anomaly depends on the distance from the driver to the edge of the baffle. By offsetting the driver to one side, you get two small anomalies at different frequencies instead of a larger one that is the sum of two due to the equal distance. In my experience it's difficult to hear this kind of thing. You would also want to avoid a lip or step or thick grille frame on the front of the speaker. These were common on older speakers, less common on more modern designs.

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    baffle revised

    Ed & Widget,

    Took your advice and stacked the tweeters and mids. Regarding height, I always have my speakers on stands that bring the tweeters at ears level when seated. Please let me know what you think.

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    baffle moved forward

    Don C,

    I offset the tweets and mids and removed the "lip" at the perimeter. I took a couple of details from my L110's which have a 1" thick baffle that protrudes a 1/4 inch from the cabinet sides and top.

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    Dang. Amateur speakerdave's Avatar
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    There's also there option of giving the LE14A some more room to work lower.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    "old" LE14A vs "newer" LE14H

    Rob,

    I'm wondering if my aged LE14A's would be appropriate for the L240Ti boxes. I used a woofer tester to get the t/s parameters of my LE14A's. (I'm a novice so forgive my ignorance)

    Re: 5.67 / 6.317
    Fs: 18.58 / 20.033
    Zmax: 173 / 175 ohms

    Qes: 0.1721 / 0.2297
    Qms: 5.088 / 6.1355
    Qts: 0.167 / 0.2214

    Le: 1.839 / 1.599 Mh@1k

    Vas: 14.7 / 3.4385 cu.ft.

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    speakerdave,

    I tried the same woofers in a pair of L55 cabinets, which are the same as the Lancer 101 cabinets, in the same listening space and the sound was thinner than in the S99 cabs. In that space, the S99's sound much better in the lower frequencies.

    The room is approximately 8-1/2 feet deep by 9 feet wide. My ears are about 7 feet or so from the baffles.

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    Dang. Amateur speakerdave's Avatar
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    JBL's need in the late fifties and into the sixties when the LE10 and LE14 came on line was for speakers with good bass in smaller cabinets to meet the sometimes conflicting needs of two-speaker stereo and WAF/decor. Although in the component series the S1 and S12 systems with the LE14A were recommended for up to 5 cu ft, in finished systems the LE14 series was never used in a 3 or 3.5 cu ft cabinet until the later Aquarius, L220, L240, L250 and finally the Array. The LE14A may not quite have the performance of the later versions, but it will benefit similarly by having the larger box to work in. If building from scratch I think a larger box is worth considering.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    small room, big speakers?

    speakerdave,

    The room where these will be living in is a small guest room 8'-6" x 9'-0". I currently have a pair of L110's in there that sound excellent but after hearing the bass response from the S99's in the same room, I was impressed. The S99's don't sound as good as the L110's in the mid and high frequencies though, that's why I decided to build a new system around the LE14A's.

    I could build larger enclosures, but considering the space am I risking muddying up the bass? As I mentioned earlier, I tried the LE14A's in L55 cabinets in the same space and they did not sound as good as the S99 cabinets.

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    Hi Bedrock,

    I think that you have improved your design considerably, but I agree with Speaker Dave regarding the larger box. If you note his examples of later use of the LE14, they are all 3+ft3. I wonder if the better bass you are hearing is the knee
    of the response curve of the driver in an incorrect box. Of the examples he gave I think the 240ti ( perhaps reconfigured ) might be the best for your needs. You could make it taller and deeper than the box than the 99 box. BTW, what kind of music do you listen too?

    Ed
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    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by bedrock602 View Post
    speakerdave,

    The room where these will be living in is a small guest room 8'-6" x 9'-0". I currently have a pair of L110's in there that sound excellent but after hearing the bass response from the S99's in the same room, I was impressed. The S99's don't sound as good as the L110's in the mid and high frequencies though, that's why I decided to build a new system around the LE14A's.

    I could build larger enclosures, but considering the space am I risking muddying up the bass? As I mentioned earlier, I tried the LE14A's in L55 cabinets in the same space and they did not sound as good as the S99 cabinets.
    I agree that may feel like a small space, so the bass should be carefully managed. I would try to avoid a prominent knee. As GT said in the context of designing speaker systems for the Japanese market where small rooms are the rule, "I will have my banana roll off."

    I was just trying to be more explicit about what I said. Not meant to be pressure. Existing cabinets are often a boon for sure. JBL certainly was successful getting satisfying bass out of small boxes with that woofer. While it is often a very good idea to follow JBL's successful designs exactly, in the case of the 14's there are many choices. One of the advantages of diy is that one need not be bound by JBL's marketing and price point driven design choices, if they are understood. The later applications I listed above could be considered the liberation of the 14.

    The concern about bass muddiness reminds me that it is a good idea to get the woofer off the floor.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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