Saturday, August 27, 2011

DIY car audio with digital graphic equalizer

Last year, I showed DIY car audio using home audio components. I have been satisfied middling, but recently I occasionally found a digital graphic equalizer, Behringer DEQ2496, and I couldn't stop trying it.

Here, I show the configuration.




The 44.1kHz 16bit S/PDIF signal is converted to 88.2kHz 24bit signal to minimize a quantization error using Behringer SRC2496. It is transferred to the digital equalizer, Behringer DEQ2496, which was installed beneath a driver's seat and fixed by velcro fastening.





A characteristic feature of DEQ2496 is automatic equalization with a measurement microphone. Behringer ECM8000 is inexpensive and suitable one for the measurement of acoustics. I measured a frequency response of my speakers using DEQ2496 and ECM8000.

DEQ2496 can automatically flatten the frequency response by the graphic equalizer. Starting from the automatically set config, the graphic equalizer was manually set for fine tuning. Listening to some music sources, the equalizer was adjusted so that the speakers had little presence in the acoustic field. The following photos show settings of the graphic and parametric equalizers of DEQ2496.




Since high frequency had significantly low response because of the installed position of speakers, it was compensated with another digital equalizer in the digital amplifier.




In practice, the frequency response was roughly flattened using it, and then finely tuned by DEQ2496.

How was the sound with the equalizer? Amazing. Really amazing. Now I understand that the equalization is essential for car audio. With the digital system, I could not recognize any loss of sound quality from the equalizer. The Behringer products, SRC2496, DEQ2496, and ECM8000 are inexpensive but valuable devices not only for studio but also car audio.

Friday, July 30, 2010

DIY car audio using home audio components

Car audio is the only way for me to listen to music with standard loudspeakers. Although a listening space in the car is far from ideal because of various noises and limited installation/listening space, etc., it's the only space that is isolated from the outside, enabling to use loudspeakers without complaint by anyone else. Here I show my approach to car audio, using home audio components.

There were some reasons why I chose home audio components but not car audio components. My primary motivation was a difficulty to replace a audio deck of my car, 2nd Gen Mazda Demio (Mazda 2) DY-3W, that I purchased recently. Its front panel of the audio deck was unified with a controller of air conditioner, and Mazda and and any 3rd parties did not provide alternative panel for standard DIN-size audio decks. This meant that I had to use home or mobile audio components for the audio player.

Since I have all music albums in my iPod classic 6th gen with Apple Lossless format, I chose it as a juke box and transporter of the digital data -- but not the analog source. The key component for it was a digital data converter, Onkyo ND-S1.
ND-S1 converts the digital data from iPod to standard S/PDIF outputs. It was installed beneath the passenger seat.

A step-down DC/DC converter was used to supply 5V power for ND-S1.
The iPod classic was connected to ND-S1 through a dock extender cable.
Its optical output was connected to a digital amplifier, Rasteme RSDA302P.


RSDA302P is a low-cost high-quality digital amplifier that amplifies digital data using STmicro STA328 without conventional D/A conversion. Its compact size and low-power consumption are very suitable for car audio.


A step-up DC/DC converter, which was originally designed for laptops, supplies 24V to RSDA302P. Well, perhaps you can make it better by yourself... but I was lazy.

A speaker output of the default CD player and AM/FM radio tuner deck was input to a high-low converter manufactured by Audio Technica, and then input to the analog in of RSDA302P.


It was not necessary to use home audio loudspeakers, but I chose them instead of car speakers that could be installed easily. The reason was that I preferred full range speakers rather than coaxial units or multi-speaker units which are usually adopted for car audio. Since high-quality full range speakers for car audio are rare, I chose full range speakers from home audio components. After investigation, I purchased Markaudio Alpair 10.

To install Alpair 10, I designed a speaker baffle using a free 2D CAD software.


This CAD file was sent to a wood processing pro, which offers the service inexpensively.
The baffle was delivered after 3 weeks from the order.

Before installing the speakers, it was necessary to strengthen the damping of the doors -- so-called deadening.

This photo is the door panel before the installation.

The door panel was removed. You can see the default paper cone speaker. The service hole was covered with a plastic, which seemed to contribute to weight saving and deadening.

The default speaker was removed, and damping sheets made of asphalt were attached behind the speaker hole and on a part of the plastic. I purchased the sheets from Tokyu Hands.
On the damping sheet behind the speaker, I attached acoustic absorption sheet.

The Alpair 10 was installed.

At this step, once the door panel was attached and the sound was checked. Unfortunately, I found large acoustic resonance from the plastic plate. To reduce the resonance amplitude and to move the center resonance frequency around a few hundred Hz to a few ten Hz, I pasted lead sheets, Tokyo Bouon TA-1000.

I pasted 1.5 sheets, which have approximately 3 kg, for each door.


The damping sheet was pasted on the lead sheet to reduce the resonance further.

Since the speaker conflicted with the door panel, its inner plastic was grinded by a grinder. This photo shows the door panel before grinding.

Using a grinder, the plastic was grinded.

Using a metal brush attached on an electric screwdriver and air brush connected to a compressor, grinded dust was cleaned up.


After the grinding and cleaning.

The acoustic absorption sheets were sticked inside the door panel.

At last, the door panel was attached on the door.



The system sounds smoothly and mellifluously, and best suits jazz music. The RSDA302P drives the Alpair 10 nicely. It's not powerful, but easy to listen, which would be rather preferable for BGM when driving. This simple, low-cost, high-quality, full digital, full range car audio system using home audio components can be recommended to anybody who wants to listen to music in a car. I'd welcome any questions and comments.

Sunday, May 23, 2010

Photohitoとtumblrのブログパーツ

Photohitoにアカウント作ってブログパーツを置いてみた。
常に動いてるとちょっとうざったいかもしれないので、下のほうに。

もう一つ。
Tumblrのブログパーツを探したら、Yahoo pipesで作っている人がいたのでこちらも置いてみた。
こっちのデザインのほうが落ち着いてますね。

Sunday, January 3, 2010

Mini-ITXなPC自作

昨日母の実家に行ったところ、叔父が古いPCで手間取った話をしていたので、 うちで余っているパーツを活用しつつPCを組んでみることにしました。 叔父のPCはAMD Duron 800MHzくらいのWindows XPマシンで、何度かメンテに行ったことがありますが、それはもう遅いなんてもんじゃありません。 従姉妹にとってもそろそろまともなPCでリテラシーを学ぶべき時期ですので、一晩考えてパーツを選んでみました。

まず、うちで余っているパーツ。
  • CPU: Core2Duo E6420
  • Mem: DDR2 800 1GB*2
  • Monitor: Sony SDM-S75F (17-inch SXGA)
これらはそのまま活用で問題ないでしょう。 モニタは現在使用中ですが、これを機に自分のはアップグレード予定。

さて、重要なのがマザーとケースの選定です。 今回の場合使う人がPCケースの中を開けてどうこうするということがまず無いと思われるので、mini-ITXフォームファクタを採用してとにかく外形を小さくする方針としました。 PCでゲームをすることもないので、GPUはオンボ。 マザーの候補はこのあたりでした。

GF9300系はオンボの割にグラフィック性能が高く、Hybrid SLIにも対応していて自作er心をくすぐる製品なのですが、必須性能ではないので却下。 最後のBT901はマザー・ケース・電源セットで\15,000程度と安いのですが、ケースが無駄にでかくて今回の狙いに合わないので却下。 そんなわけでIntel DG45FCを選択しました。

次にケースです。 今回の狙いとして、
  1. できるだけコンパクト
  2. 設置場所の都合によりキューブではなくスリムタワータイプ
  3. 5-inch 光学ドライブベイ x1
  4. 3.5-inch HDD シャドウベイ x1
を設定しました。

候補としてはこのあたり。
迷いましたが、カードリーダー内蔵と余裕のある電源をとってScytheのほうを選びました。 また、IN WINのほうが高級感があるのですが、今回は変に気を使わせたくないので逆に高級感は無くて構わないのです。

というわけで手持ちと購入した物品をまとめると下記のようになりました。
  • CPU: Core2Duo E6420
  • Mem: DDR2 800 1GB*2
  • Monitor: Sony SDM-S75F (17-inch SXGA)
  • Keyboard: Happy Hacking Keyboard Lite 2 PD-KB220B/U
  • Mouse: Logicool MX-320
以上手持ち、以下購入。
金額は送料代引き手数料込み。
  • Motherboard: Intel DG45FC \11,908 (コムロード)
  • Case: SCY-402-ITX-BK \7,933 (e-tokka)
  • DVD drive: I-O DVR-S7240LEK \2,980 (Amazon)
  • HDD: HDS721010CLA332 \7,461 (sofmap)
  • OS: Win7 Home Premium 32bit DSP \12,310 (無人島)
  • Office: MS Office Standard 2007 20周年記念優待アップグレード版 \15,468 (Amazon)
  • Fan1: Scythe S-Flex80B SFF80B \1,492 (Amazon)
  • Fan2: アイネックス Omega Typhoon 60mm CFZ-60S \1,227*2 (Amazon)
  • Grease: Sanwa TK-P3S \535 (Amazon)
番外
  • 自分用液晶モニタ: Hyundai W240D \24,400 (NTT-X store)
なんだかんだで結構な額になりましたが、まあ納得いく構成ではないでしょうか。たまには自腹で好き勝手やってみるのも楽しいです。もし何も流用しないなら、デスクトップ代替型ラップトップの特価品でOKでしょう。小さいデスクトップってのはなかなか難しいなぁという感想です。

Saturday, November 7, 2009

Win7へのリモートデスクトップでのマルチモニタ機能のエディション制限

Remote desktop connection 7.0 client for vista/xp がリリースされました。

新機能としてマルチモニタ(従来から存在したスパンモードではなく、真のマルチモニタ)がサポートされたので、それ目当てでインストールしてみました。 環境は下記の通り。
  • Host: Windows 7 Pro x64
  • Client: Windows XP Pro x86 with RDC 7.0
ところが、オプションでマルチモニタにチェックを付けてもシングルモニタしか使えません。 これは怪しい・・・ということでググってみたら、MSのブログのコメントが引っ掛かりました。
リモートデスクトップでのマルチモニタ機能は、どうやらホスト側がWin7 Enterprise/Ultimateでないと有効にならないようです。

さらに調べてみるとwikipediaに表が見つかったのですが、これが何と上記コメントをソースとしています。

信じ難いことですが、Windowsの各エディションの機能制限という重要事項の割に、ブログのコメントしかソースが無い状況のようです。少なくとも、検索で引っ掛かりません。

Vista以降のWindowsのエディション体系というのはユーザーを無視して純粋にマーケティングの要請に最適化した結果なのだろうと邪推しているのですが、それにしても、このような中途半端な機能制限はやめて欲しいですね。 上位エディションの差別化のために制限するとしても、MS自身がもっとわかりやすくユーザーに情報を提供すべきでしょう。