Archive for July 25, 2013

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。

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

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Hello / こんにちは,

I like very much the sound of front loaded horns. They have very good dynamics and the impact that i associate with live sound. I had quite a few experiences with front loaded horns which i will be presenting on this blog.

In the video above you can see a 2 way FLH system composed of a mid-bass horn with dual 10 inchers and a 500Hz horn clone of Altec 511B loading a 3 inch compression driver.

I made this horn because i felt there is not enough impact from direct radiators in the midrange. A driver that can be crossed low can be pretty expensive although i have been looking at Monacor KU-516 or Klipsch K55 which are reasonably priced.

A basic sketch of the mid-bass horn is shown below. It is a conical horn loading the front of the drivers and a bass reflex enclosure loading the back of the drivers.

horn 2x10

You can find below the Akabak script that describes this horn system:

|FLH 210 Mid-bass

Def_Driver ‘6366’
dD1=8cm dD=23.2cm tD1=4.8cm
Mms=34.9g Cms=0.19mm/N Rms=.15mks
Re=5.3ohm BL=13.8Tm Le=0.95mH

System ‘Mid-Bass Horn’

Driver Def=’6366′ ‘D1′ Node=0=1=10=20
Driver Def=’6366′ ‘D2′ Node=0=1=30=40

|Front Wave

Duct ‘FrontChamber1′ Node=10=11
dD=23.2cm Len=2cm
Duct ‘FrontChamber2′ Node=30=12
dD=23.2cm Len=2cm
AcouMass ‘Entry1′ Node=11=13
Ma={ (1.2/(3.14*0.1))*(sqr(0.26-0.23)/(2*0.26*0.23))*ln((0.26+0.23)/(0.26-0.23))+ln(sqr(0.26+0.23)/(4*0.26*0.23))}
Horn ‘FrontHorn1′ Node=13=14
Conical
WTh=10cm HTh=26cm
WMo=54cm HMo=34.5cm
Len=30cm
x=0 y=17.5cm z=0 HAngle=0 VAngle=0
AcouMass ‘Entry2′ Node=12=15
Ma={ (1.2/(3.14*0.1))*(sqr(0.26-0.23)/(2*0.26*0.23))*ln((0.26+0.23)/(0.26-0.23))+ln(sqr(0.26+0.23)/(4*0.26*0.23))}
Horn ‘FrontHorn2′ Node=15=16
Conical
WTh=10cm HTh=26cm
WMo=54cm HMo=34.5cm
Len=30cm
x=0 y=-17.5cm z=0 HAngle=0 VAngle=0

|Back Wave

Duct ‘D_rear1′ Node=20
WD=26.5cm HD=21cm Len=32cm
Duct ‘D_rear2′ Node=20=40
WD=26.5cm HD=27cm Len=32cm
Duct ‘D_rear3′ Node=40=41
WD=26.5cm HD=21cm Len=32cm
|AcouMass ‘Entry1′ Node=41=50
|Ma={ (1.2/(3.14*0.1))*(sqr(0.12-0.04)/(2*0.12*0.04))*ln((0.12+0.04)/(0.12-0.04))+ln(sqr(0.04+0.12)/(4*0.04*0.12))}
Waveguide ‘D_rear4′ Node=41=42
WTh=16.5cm HTh=4cm Len=35cm
WMo=27cm HMo=4cm
Radiator ‘R1′ Node=42
WD=27cm HD=4cm
x=-14.5cm Y=-30.4cm z=0
Waveguide ‘D_rear5′ Node=41=43
WTh=16.5cm HTh=4cm Len=35cm
WMo=27cm HMo=4cm
Radiator ‘R2′ Node=43
WD=27cm HD=4cm
x=14.5cm Y=-30.4cm z=0

You can remove “|” from:

|AcouMass ‘Entry1′ Node=41=50
|Ma={ (1.2/(3.14*0.1))*(sqr(0.12-0.04)/(2*0.12*0.04))*ln((0.12+0.04)/(0.12-0.04))+ln(sqr(0.04+0.12)/(4*0.04*0.12))}

and modify nodes 41 with 50 on D_rear4 and D_rear5 to consider acoustic mass at the port entrance caused by the 90 degrees bend. Also you can model any other 10 inch driver by defining its parameters.

Running the sims you can see results below. 90 degree directivity point is at 700Hz somewhat lower than i expected and that meant i need to cross the high frequency horn below 1kHz.

Front loaded horn polar response

Front loaded horn polar response

Front loaded horn frequency response

Front loaded horn frequency response

Frequency response is optimistic on high frequency but we will see how it turns out in next article.

 

Thank you for visiting.

ご覧いただきありがとうございます。

LM13600: Noise Gate Project ノイズゲートプロジェクト Part 1

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Here is a noise gate module built around LM13600. You can use the newer and better LM13700, i chose LM13600 because i already have a few of them from National Semiconductor. I use these modules to clean up sound in audio surveillance applications but also can be used with music instruments like electric guitars.

LM13600 noise gate project

 

In the past i was using a FET transistor, mostly 2SK30, as a variable resistor and create a voltage controlled… voltage divider hehe. However better performance comes from using a VCA (Voltage Controlled Amplifier) not to mention the versatility of having the entire module in the form of a integrated circuit.

2SK30 FET noise gate module

2SK30 FET noise gate module

In LM13600 we have two operational transconductance amplifiers giving the posibility to varry the current through the input stage long tail pair. Its input will be a voltage and output will be current so you can find these devices named OTA (Operational Transconductance Amplifier) or VCCS (Voltage Controlled Current Source). They are very handy when you need to adjust gain of an amplifier dynamically.

In a noise gate we want to pass all signal with an amplitude higher than a settable threshold and block all signal with lower amplitude. What we’ll do is take the input signal rectify it, compare the result with our threshold and then modify the gain of the amplifier based on the comparator output.

As a first step i built the VCA around LM13600 as i wanted to check how the amplification works. You can see the schematic (pretty much the one from datasheet) and construction. I was able to trace the gain vs control voltage plot and it shows a pretty linear function.

LM13600 VCA schematic

LM13600 VCA schematic

LM13600 VCA Test

LM13600 VCA Test

Gain vs Control Voltage Plot

Gain vs Control Voltage Plot

Looking at the above chart we can see that if our input signal amplitude is below noise gate threshold then we need to set the control voltage to -15V (with +/-15V supply) and if it is above threshold ideally we will need 15V control voltage.

To rectify the input signal i use a two opamp schematic fairly common discussed on ESP website and other materials. The DC voltage is then compared with our threshold with a LM393 dual comparator. Supply voltage for the LM393 is +/-15V so output will swing close to these values providing the control voltage.

LM393 Dual Comparator

LM393 Dual Comparator

LM13600 Noise Gate Temp Schematic

LM13600 Noise Gate Temp Schematic

Before the rectifier you can see an amplifier, this is used to adjust sensitivity. Threshold is set by R16. C3 C4 are very important as they reduce artifacts caused by ripple in the rectified signal. Even so as it is there are a few issues when the signal level is equal to the set threshold level but solution for this will be presented later.

LM13600 Noise Gate Module

 

Dual power supply

Dual power supply

The voltage from the LM393 output can be passed through and integrator and thus adjust the attack time. This can be a very cool effect for musical instruments as it provides a swell effect similar to a volume pedal.

Circuit works of course will be improved pretty much in next articles so hope you will visit again. Below you can see a scope trace with TrueRTA (the scope feature is free). You can see pink noise signal and only peaks with an amplitude higher than my threshold are passing through.

Scope view of pink noise through gate

 

Thank you for visiting.

ご覧いただきありがとうございます。

ESOTERICの製品内部 – P-02 – D-02 – I-03

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P-02 SACD/ CD Transport

Esoteric P-02 SACD Transport

Esoteric P-02 SACD Transport

Esoteric P-02 SACD Transport

Esoteric P-02 SACD Transport: Top Side

Esoteric P-02 SACD Transport

Esoteric P-02 SACD Transport: Bottom Side

Esoteric P-02 SACD Transport

Esoteric P-02 SACD Transport: Mechanics

D-02 Digital To Analog Decoder

D-02 Digital To Analog Decoder

D-02 Digital To Analog Decoder

D-02 Digital To Analog Decoder

D-02 Digital To Analog Decoder: Bottom Side

D-02 Digital To Analog Decoder

D-02 Digital To Analog Decoder: Top Side

I-03 Integrated Amplifier

I-03 Integrated Amplifier

I-03 Integrated Amplifier

I-03 Integrated Amplifier

I-03 Integrated Amplifier: Top Side

Thank you for visiting,

ご覧いただきありがとうございます。

DENON AVC-A1HD内部 / Inside DENON AVC-A1HD

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こんにちは、

DENON AVC-A1HDの写真。

dsc02160 dsc02159

dsc02161

Thank you for visiting,

ご覧いただきありがとうございます。

Paper Tweeter

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I had a little fun Sunday night while listening to Elvin Jones. Found a pair of small paper tweeters, seemed of german made, probably Grundig, i think used in higher quality TV sets.

I hooked them up via a 3.8uF capacitor and listened a bit. While not the most revealing sound i like their timbre and thought they are good for jazz. I measured their respomse and impedance and then hooked them to a pair of OB speakers i have with a single russian fullrange driver. Very old drivers but got them in great condition.

There sure is something about light paper pulp cones that i like alot. Is it transients, dynamics or sensitivity i dont know for sure but my guess the secret is somewhere along those lines.

Paper Tweeter

Paper Tweeter

Paper Tweeter

Paper Tweeter

Paper Tweeter

Paper Tweeter

You can see response starts falling with increasing frequency. This is a much disputed issue with audio enthusiasts. Some prefer it like this (me as well) some like it flatter some prefer a bit on the rise. Either way you can see the tweeter with a 40mm diameter radiating cone can hold up to almost 60 degree dispertion within 6dB. Pretty impressive and pretty linear power response.

I hooked it to the fullrange system with a 2.2uF MKP capacitor.

Thanks for visiting.

DALI Epicon6スピーカー

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DALI成分の写真。 小さなTHD磁気回路を見ることができます。

Components of DALI Epicon 6 loudspeaker. You can see the low distortion magnetic circuit.

Dali Epicon 6 スピーカー

dsc02167 dsc02168 dsc02169

Thank you for visiting, ご覧いただきありがとうございます。

Accuphase DAC-30デジタルモジュール

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ACCUPHASE DAC-30の写真。デジタル – アナログ変換器。

Digital to analog module DAC-30 from Accuphase.

Accuphase DAC-30 digital to analog module