ミッドレンジホルン型ラウドスピーカー / Midrange Front Loaded Horns Continued

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以前も述べたように、ホルンスピーカーから流れるあの力強いサウンドが好きで、ミッドバスシステムも発表しました。制作の流れや反響振動の測定値、ALTEC 511Bホルンクローンや3インチ圧縮ドライバーは後日アップします。

In previous article i mentioned i like the powerfull sound from horn loudspeakers and presented a mid-bass horn system. I will continue showing how it was built and show frequency response measurements and how i integrated the ALTEC 511B horn clone and 3 inch compression driver.

The 10 incher driver i used was a 6366 i worked on with HiPower. Other 10 inch drivers that can be used:

RCF L10-568

Precision Devices PDN.10MH25

Faital Pro 10PR310

The mid bass construction is made of MDF of 20mm thickness and 8mm thickness. Below you can see some pictures with the construction:

Mid bass horn dual 10 inch Mid bass horn dual 10 inch Mid bass horn dual 10 inch Mid bass horn dual 10 inch Mid bass horn dual 10 inch Mid bass horn dual 10 inch

The main problem with front horns loading cone drivers is high frequency response. Especially if the cone is large in diameter. You can have a strong motor, a very light cone, and a low inductance and still have a poor high frequency response. That is because of the air trapped between the cone and the horn throat.

This is similar to compression chamber in high frequency compression drivers. What happens is that at low frequencies all the air is pushed to the horn through so air behaves like a mass, similar to the air in a bass reflex port. At high frequency however not all the air from that volume gets into the throat. At some point is starts to be compressed and thus it acts like a compliance. This is a basic acoustic low pass filter and it’s the main culprit for high frequency response roll off.

Compliance of air at horn throat

This is very important when front loading a fullrange driver. You can only use minimal compression ratio so that most of the radiating surface of the driver is in the horn throat.

Observing this i constructed a 10 inch driver with a 4 inch voice coil so that the cone has a flatter profile and be closer to the horn throat.Took some experimenting but i went for a softer suspension and a high BL of 24Tm. Below you can check some pictures:

DIY 10 inch Horn Cone Driver DIY 10 inch Horn Cone Driver DIY 10 inch Horn Cone Driver DIY 10 inch Horn Cone Driver DIY 10 inch Horn Cone Driver DIY 10 inch Horn Cone Driver

High Frequency response did increase and the driver had tremendous force but unfortunately i built just one. Not only high frequency improved but the overall sensitivity improved due to the stronger motor. The diameter of the magnet ring is 200mm and the system had a Qts of 0.14!

Below you can see two on axis frequency response curves for the horn using 2 6366 10 inch units. The black trace shows response with the back wall installed and the blue one is with the back chamber left open.

Frequency Response of mid-bass horn

For high frequency i used a large format compression driver with a 3 inch diaphragm made from titanium and mylar surround. The driver can go to 700Hz fairly easily and has a pretty good high frequency response. It is based on 8074 from Hipower but modified the design for mylar surround and different phaseplug.

3 inch compression driver

3 inch compression driver and ALTEC 511 Clone Horn  コンプレッションドライバーとALTEC511ホーン

I used an active crossover to setup the system, using a first order filter at 3kHz managed to get an acoustic xover point around 700Hz. Horn cut at 600Hz 12db/octave. Here is the on axis system response:

Front loaded Horn frequency response

I also tested Peavey RX-22 and RCF ND650 and winner would be the RCF driver having better top end.

As this is an old project of mine i am still trying to find the detailed schematic of the horn through my files. I will do another followup once i find them.

Thank you for visiting.

ご覧いただきありがとうございます。

11 comments

  1. Doug Ogilvie says:

    I am interested in these plans if they exist.

    Thanks

  2. lawton Deane says:

    saw your site in my search for a front loaded midbass horn. Is the plans available for sale?

    Thanks
    Lawton

    • Stefan says:

      hi Lawton,

      Its not a matter of sale, the plans are buried in my old data so i just need to find some time and dig it. Once i find it i will post it here.
      Thank you for your comment.

  3. Oli says:

    Are the plans for this box available would love to build this and play it in my Toyota hiace

  4. Oli says:

    We are in February. Still waiting.

  5. shane says:

    Real keen on the plans hope to see them up here soon been checking most days!!

  6. William Geiger says:

    Would like more details on your 10″ x 4″ driver build,
    particularly the sources for the basket, magnet assembly and moving parts as well.

    Thanks,

    WHG

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