JBL 4315 Studio Monitor

4350のプロトタイプとして有名な"Texas Bookshelf"(テキサスブックシェルフ)は、1971年のAESで展示されました。
2216が2発、2130、2392と2440、2405という4ウェイ。
サイズ等はわからないので、例の魚眼レンズで撮影された画像から描き起こしてみました。

Mr. Don McRitchieと、Mr. Steve Schellは、"The History and Legacy of JBL"の38ページ右欄に以下のようにこのスピーカーシステムについて説明しています。

Market Dominance of JBL Studio Monitors

If one looks carefully at the fisheye photograph at bottom left, one can spot a huge, unique loudspeaker system con-taining two 15" bass drivers mounted along a vertical axis, with a top section containing a 12" driver, horn/lens and slot radiator.
This was a seminal prototype that laid the founda-tion for JBL’s rise to market dominance in the studio moni-tor industry by the mid 70s.

The prototype was the brainchild of Walter Dick, the head of JBL’s Transducer Engineering Department.
This depart-ment title was a bit of a misnomer, since it had responsibil-ity for engineering all aspects of loudspeaker systems, both professional and consumer, including transducers, networks, enclosures, and overall system parameters.
In 1971, Walter decided that JBL needed a showcase to present at the up-coming Audio Engineering Society (AES) convention.
He set the parameters for a professional loudspeaker with an unparalleled combination of output and accuracy.

The system illustrated above utilized two 2216 bass drivers, which were the professional equivalents of the LE15B de-veloped for the L200.
The mid-bass unit was a 2130, while the mid- and high-frequency drivers were the 2440 and 2405, respectively.
The system was bi-amplified with sepa-rate amplifiers for the bass section and mid/high module and was affectionately nicknamed the “Texas Bookshelf.”

As intended, the system generated a high level of attention at the AES convention.
Walter Dick recognized that there was enough interest to develop the prototype into a production model.
While the prototype was not targeted at any specific market, he realized that a studio monitor developed from that concept made the most sense. As previously mentioned, rock music was at the center of the popular culture in the 1970s.
This genre placed ever increasing demands on playback levels for which the still widely-used Altec 604, and even the JBL 4320, were inadequate.

Google Translateで翻訳してください。

1971年のAESの大会に展示した時点では、このシステムは特定の使用目的を持っていませんでした。
しかし、このシステムはAESで注目を集めたため、これをベースにしてスタジオモニターである4350が開発されることになります。
スピーカーシステムの開発は、グレッグティンバーズ氏がインタビューで答えているように、技術者主導で行われているわけではないそうです。
"誰かのアイディア"をみんなで検討することからスピーカーシステムの開発が始まり、そのアイディアというのは、おそらく企業戦略やマーケティングや販売店で聞いた顧客の要望のようなものだと思います。

テキサスブックシェルフは、4320や604のような貧弱な低音の時代から新たな力強い低音の時代の到来を告げるためのデモ用であったため、低音を強調したシステム構成を持っています。
12インチや15インチのコーン型ユニットは、迫力と厚みのある音、すなわち"ウーファーの音"をそのキャラクターとして持っています。
この"ウーファーの音"は、8インチや10インチからは聴くことができません。
テキサスブックシェルフは新たな低音の時代をアピールする目的があったので、10インチではなく12インチのミッドベースが選ばれているように思います。

同じ4ウェイ構成ながら、すべての帯域に適切なユニットを分配した改造ALTECシステムに比べると、この4350のプロトタイプは低音を偏重した構成であることがよくわかります。
12インチのミッドベースは、"ウーファーの音"を感じされるので、このような構成の15インチシステムのミッドベースとしてはあまり適切ではありません。
そういう観点から同程度の低音再生能力を持つシステムで10インチのミッドベースを備えるモニタースピーカーを眺めてみると、4345モニターやWest Lake AudioのBBSM-15の意図がわかると思います。

West Lake Audio BBSM-15

Lansing Heritage DIY Forum

改造ALTECシステムはなかなか面白いシステムですし、興味をお持ちの方に参考になればと、例のスレッドに書き込んでおくことにしました。
ランシングヘリテッジの管理人さんのMr. Widgetさんにレスをいただきました。
うれしいな。




10-21-2019, 04:08 AM
kiirojbl

Hi,
I made this Remodeling Altec System 11 years ago.
Since then, the system and I have been getting along well.
I recently added Selenium HM17-25 and JBL 2408H to the system.

The Remodeling Altec System is controlled using Behringer DCX2496, DEQ2496 and ECM8000.
The systems are driven by 3 way multi amp system.
I uses AUTO ALIGN function of DCX2496 and AUTO EQ function of DEQ2496 to flatten the frequency response from 25Hz to 20kHz, and the following parametric equalization settings of DEQ2496 are made.

10-21-2019, 06:31 AM
kiirojbl

I like classical music, especially orchestras, so I like speakers that can make dynamic expressions in a wide range.
This Remodeling Altec System meets this demand with an 18 inch woofer and ALTEC MR94 Large Format Horn and 291-16K.

The 828B cabinet is divided into upper and lower chambers by a partition plate.
The lower chamber containing the PEAVEY LOMAX 18 inch woofer has a capacity of 8.0 cubic feet/225 L.
The enclosure volume recommended by PEAVEY are 4.0cf a small volume enclosure (44Hz/-3dB), 6.0cf a medium volume enclosure (37Hz/-3dB), 8.0cf a large volume enclosure (31Hz/-3dB).
Therefore, the volume of this lower chamber is ideal for this woofer unit.
The vent dimensions are 4.7inch/12cm x 5.5inch/14cm for the opening and 11inch/28cm for the length.

This Remodeling Altec System succeeded in efficiently storing an 18 inch killer woofer.
And this system with excellent space factor is a very compact system for me.

One of my other systems is Yellow Horn System which driven by 8 way multi amp system.

My other system is DIY Horn System which driven by 7 way multi amp system.

These systems are also controlled using Behringer DCX2496 and DEQ2496.

This Remodeling Altec System is a very small system compared to the Yellow Horn System and the DIY Horn System, but I like it because it sounds great despite being compact.




10-21-2019, 07:06 PM
Mr. Widget

Pretty spectacular looking systems! Not sure they would fit in very many homes, but it looks like you’ve made them work.

Widget




10-21-2019, 10:12 PM
kiirojbl

Thank you Mr. Widget
The Lansing Heritage site brings me a lot of knowledge and fun.
Thank you very much.

I'm sure my speaker systems are a little big and my wife says so too.
The next day after listening to the orchestra in the concert hall, I don't want to be disappointed when I listen to the same CD on the audio device.
I believe the size of the speaker should be reflected in its height.
I think a height of about 6feet/180cm is desirable.
I expect the Texas Bookshelf is a speaker system built on the same idea.

I don't like the muddiness of the mid-low range sound of the woofer during high-power playback.
Many classical music fans are delighted to hear the muddiness as an expression of the depth of strings section of orchestra, but I don't think so.
After all, I think that the woofer which reproduces the lowest range and a unit which reproduces the mid-low range should be different units.
I totally agree with a 4-way concept that Mr. Greg Timbers pioneered in the 4315 monitor.

The Remodeling Altec System is not intended to add an 18-inch woofer to get the lowest range, but rather to remove the lowest range sound from the ALTEC 3156 woofer.
Therefore, the crossover frequencies of DCX2496 of the system are 90Hz and 500Hz, and the slope types are LR-48dB/oct.

Large speaker systems, such as the yellow horn system, naturally have some disadvantages.
The most serious problem is that 7-way or 8-way mluti amp systems are difficult to organize, that is, it is very difficult to adjust the out put levels of DCX 2496.
However, by using the AUTO ALIGN function of DCX2496 and AUTO EQ function of DEQ2496 to flatten the frequency response, I can easily obtain extremely accurate phase and balance.
Furthermore, sound that lacks musicality due to its flatness can be revived by performing parametric equalization of DEQ2496.

10-22-2019, 10:48 PM
kiirojbl

Mr. Don McRitchie and Mr. Steve Schell wrote the following in the right column on page 30 of "The History and Legacy of JBL".

"The mid 1960s saw JBL take one more run at Altec’s stran-glehold on the cinema market, and it resulted in the same resounding lack of success. The Altec Voice of the Theatre (VOTT) was an industry standard because it had become a reference and not because it represented the pinnacle of accuracy—which it did not. Sonic limitations such as the uneven response of its horn/reflex enclosure and restricted high-frequency extension were well-known in the industry."

My impression of VOTT is as follows.
The good news is that VOTT gives a fresh expression when JAZZ is played at high volume, and has a cool appearance, and can talk about history and legend.
And the bad points are everything else.
In particular, compared with a modern speaker system, the low frequency reproduction capability is extremely low, and the high frequency is not worthy of evaluation unless a large format Manta Ray horn is used.

Why did I get VOTT?
It was an offer from my friend, and at that time I responded lightly without thinking too much.
If I don't like it, I just put it in the warehouse.
I knew that I couldn't get very good results using VOTT as it was, so I decided to install a subwoofer.

The lower chamber of the 828 has a volume of 8 cf, so it can hold almost any 18 inch woofer.
Another idea was to use a 15 inch woofer.
Enclose the circumference of the woofer unit like Electro Voice MTL-4, and place the woofer unit in a recessed position.
I thought that there is enough volume of lower chamber even if a recess is provided, and that a bass with a punch might be obtained.

Electro Voice MTL-4

Yesterday, 09:03 AM
kiirojbl

I was at a loss between the 18-inch plan and the 15-inch plan with a recess, but eventually adopted the 18-inch plan.
At that time, 18-inch woofers with "mms" of about 200g began to become popular, so I wanted to try the 18-inch plan.
This prospect was successful and I was able to get a deep and transparent bass.

I am fascinated by the appearance of vintage products, but the sound of these products is many problematic.
I listened to the large multicell horns and sectoral horns of ALTEC, huge horns of Western Electric, and front loaded horns or scoop with 15 inch woofer(s), but I was disappointed.

By understanding the weaknesses of vintage products well, remodeling the weaknesses and using the automatic adjustment capability of digital equipment, you can extend the life of vintage products and deepen your understanding of audio technology.
I often hear stories of people who notice the poor sound of his vintage products and throw away everything.
I recommend you to take some measures before that happens.

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