LE14A Project: Enclosure Design

[bedrock602]

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.

84379

[Ed Kreamer]

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

[Mr. Widget]

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

[Robh3606]

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/images/jbl/specs/home-speakers/1984-ti/page07.jpg


Rob:)

[bedrock602]

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?

[Don C]

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.

[bedrock602]

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.

84415

[bedrock602]

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.

84416

[speakerdave]

There's also there option of giving the LE14A some more room to work lower.

[bedrock602]

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.

[bedrock602]

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.

[speakerdave]

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.

[bedrock602]

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.

[Ed Kreamer]

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

[speakerdave]

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.

[bedrock602]

Thanks speakerdave and Ed for the input. I'll admit that using the S99 box and port size would make things much easier but if the LE14A will work better in a larger encloser, even in a small room, then that's the route I'll take.

If I'm starting from scratch, I would like to take this opportunity to learn how to size the enclosures for my particular woofers. This is something I have been thinking about for a couple of years but didn't have a clear goal untill now. I'm not expecting to be spoon fed information, but if someone could give me a basic outline of the steps needed to properly size the cabinets, it would be greatly appreciated.

[Robh3606]

Look up Win Isd and use that to determine a preliminary enclosure size. The Le-14 is a loaded JBL driver in the database. I used 3.8 cubic ft for my Array bases Le-14H-3.

http://www.linearteam.org/

http://www.audioheritage.org/vbulletin/showthread.php?27553-Universal-Bass-Modules&highlight=universal+bass+modules

Rob:)

[bedrock602]

Thanks Rob,

I downloaded the program but there were only a handful of JBL drivers listed in the database, LE14... was not one of them.

Nice work on the bass modules.

[Robh3606]

Hello Bedrock

Thanks, you downloaded the newer version try the older 2002 they have both the 14A and H loaded as well as many other JBL drivers or just load up the T/S parameters into the program as a new driver.

Rob:)


http://www.lansingheritage.org/html/jbl/reference/notes/tech1-3a.htm (http://www.lansingheritage.org/html/jbl/reference/notes/tech1-3a.htm)

[RMC]

Hi bedrock,

For example, below is a pic of the driver response modeled in Winspeakerz with 3.8 cu.ft. tuned at 35 hz, and the usual QL 7 and half-space loading. Reasonably flat being within less than one db. So you should get something comparable to this with using same box parameters (Vb, Fb, QL).

Win ISD bugs when different versions were installed on my computer (pro 2016, pro 2002 and the smaller Beta). Had to uninstall pro 2002 and Beta to restore peace... Kept pro 2016 and Winspeakerz, the latter not free but not expensive, paid $40. few years ago and it has a 1,500+ driver database (including LE14A/H) to which I add as need be. Also has crossover design and cabinet design features, plus many easy to edit parameters. No hassles, no bugs. Fast and easy to work with, that's why I use it much more than Win ISD.

I've tried many free or low cost softwares over the years and Winspeakerz from True Audio is the best price/features/performance wise in my view. For the few who may think Winspeakerz isn't that good, well they sure have not read Linearteam's own! 20 page Technical Paper comparing eleven (yes 11) different speaker design softwares on the most criticized aspect of box design (Lv accuracy ). That comparison includes known names such as Win ISD, JBL Speakershop, Winspeakerz, Bass Box Pro v.6, etc. The results would be eye opening for "the blinds leading the blinds".

In the past Rick Carlson's free Box Plot 3.0 was among the favorites of mine up to Windows XP with 32 bits architecture, but I was never able to make it work on Windows 7 Pro 64 bits architecture, even using the compatibility mode in Win 7 Pro. As far as I know, Carlson never updated his software for more recent windows versions.

There's a sequence to follow when entering driver data in previous 2002 ISD pro version otherwise it bugs. Let me know if you need that sequence, I think I still have a copy of it. That bug was corrected in the 2016 edition, but that edition has very poor number of drivers in database.

Many people don't know ISD Pro's (2002 & 2016) has default QL10 which isn't standard, it can be changed to standard QL7 when in "box" tab then go to "advanced" at bottom of screen and replace QL 10 to QL 7. This software will always default back to QL10 with a new project, except when reopening a previously saved project with QL7, so you must not forget to change it back to QL7 again and again... Winspeakerz has the default standard QL7 which is very easy to change at will, plus or minus. Regards,

Richard

P.S. Just checked and Winspeakerz still goes for $39.95. For such small amount of money I stopped screwing around with Win ISD free versions a while ago, except for when I want to double check on something, like Lv, to get a "second opinion"...


84441

[bedrock602]

I finally got a break from work this weekend and sat down with BB6 software that has been collecting dust for a couple of years.

It took several tries at inputting data to figure out the nuts and bolts of the software but I think I have the very basics covered.

I started with the T/S parameters of one of my LE14A's as measured with the Smith & Larson Woofer Tester 2. I could have used the T/S parameters that are loaded in BB6 but they were slightly different than what I measured. That said, I'm not entirely certain my measurements are correct in that I may not have used the WT2 properly, but what the hell, I usually learn the hard way anyway...:banghead:

I think this is a good time to remind anyone reading this that I am a COMPLETE NOVICE so you may read things in my posts that make no sense or are completely idiotic. My apologies in advance to all who have devoted their careers to the design and engineering of speaker enclosures...:o:

For the first and second designs, I simply used my S99 and L55 enclosure dimensions and port sizes to get a feel for the software and to get feedback from the forum.

Box Properties are as follows:

S99:
Vb = 1.307 cu.ft.
Fb = 48.07 Hz
F3 = 47.44 Hz

L55:
Vb = 1.891 cu.ft.
Fb = 39.93 Hz
F3 = 40.6 Hz

I then increased the box sizes slightly for five more designs from 2.0 cu.ft. thru 4.0 cu.ft., as Vb increased, Fb decreased but F3 kept increasing.

84553

[bedrock602]

I found this post by 4313B in 2005,

http://www.audioheritage.org/vbulletin/showthread.php?4659-4-7-Cu-ft-too-big-for-LE14A

in his designs, F3 decreases as Vb increases, the opposite of my results. What am I doing wrong? :confused:


http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=5302&stc=1&d=1107966363

[RMC]

Hi bedrock,

Quickly as I don't have time now to analyze your results.

I note your measured driver Qts is very low 0.19 vs 0.32 and your Vas is much larger at 7.53 cu.ft. vs 5.2 cu.ft. for 4313B. The latter's predicted response curves are also flatter than yours which I think is a reflection of the higher Qts he used.

Qts and Vas are the two box size influencers.

If you look carefully 4313B varies box volume but his tuning frequency remains about the same at 30-31 hz. You also vary box volume but your box tuning frequencies are all over the map for some unknown reason (I don't use BB6). Did you change Fb manually each time or BB6 assigned those FBs automatically when volume changed? Gotta go... Regards,

Richard

[bedrock602]

Thanks for the quick response Richard. I'll take another stab at it this weekend. I'll start with the pre-loaded T/S Parameters and see if the results are closer to 4313B's. I'll also re-test the drivers with WT2 and then load them into BB6.