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D'Amore Engineering SMD IM-SG+ Owner's Manual

Impedance meter/signal generator
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IM-SG+
Impedance Meter /
Signal Generator
Owner 's Manual

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Summary of Contents for D'Amore Engineering SMD IM-SG+

  • Page 1 IM-SG+ Impedance Meter / Signal Generator Owner ’s Manual...

  • Page 2: Table Of Contents

    Table of Contents The Purpose and Benefit of This Tool What is Included About the Design Specifications Power Requirements General Notes for using the IM-SG+ A Special Feature of the Range button Compensating for test harness impedance General Notes for Measuring Raw Speaker Drivers Finding the Resonant Frequencies of a Vehicle or Room Finding the Resonant Frequencies of parts (finding rattles) Using the IM-SG+ to tune the response of an audio system...

  • Page 3: The Purpose And Benefit Of This Tool

    Limited warranty information The Purpose and Benefit of the IM-SG+ The D'Amore Engineering IM-SG+ was designed to test the impedance of raw speaker drivers, loaded speaker enclosures, passive crossover networks, audio signal cables, speaker wires, and multi-speaker systems over the entire audio frequency range.

  • Page 4: Specifications

    Specifications • Impedance Measurement Range 1 ohm-100 ohms with 0.1ohms resolution • Low Impedance Measurement Range 0.00 ohm- 0.99 ohms with 0.01 ohms resolution • Operating Range of Battery for tool accuracy 6.4 Volts – 10.5 Volts • Sine Wave Generation Frequency Range greater than 8Hz - 20kHz in two ranges •...

  • Page 5: Power Requirements

    Power Requirements Pull the silicon rubber boot off of the unit by starting at one end and pulling off towards the other end. On the back side you will see the battery compartment. Slide battery compartment cover off towards bottom end of unit to reveal the 9V battery compartment.

  • Page 6: A Special Feature Of The Range Button

    General Notes for using the IM-SG+ continued The rotary knob - Rotate slowly to sweep through the frequency range. The display - The display shows the generator frequency "f” and the measured impedance "Z" simultaneously. Range button* - Press to cycle through the modes (Low Range >...

  • Page 7: Compensating For Test Harness Impedance

    Harness Compensation If making critical measurements, like those needed when trying to derive Thiele/Small parameters for a speaker driver (Page X), the IM-SG+ can compensate for harness impedance to obtain the highest accuracy possible. 1. Turn on the IM-SG+ by holding the On button for 1 second.

  • Page 8: General Notes For Measuring Raw Speaker Drivers

    General Notes for Measuring Raw Speaker Drivers (out of box) When measuring raw speaker drivers it is important that the room in which the speaker is being tested is quiet and the air in the room is still. If a fan is blowing and air is moving in the room it will cause inaccurate readings.

  • Page 9: Finding The Resonant Frequencies Of A Vehicle Or Room

    Finding the Resonant Frequencies of a Vehicle or Room (For max SPL) 1. Connect IM-SG+ to any auxiliary input of a source unit or amplifier to use the IM-SG+ as a signal generator. Turn the volume of the source unit or amplifier gain down. 2.

  • Page 10: Finding The Resonant Frequencies Of Parts (Finding Rattles)

    Finding the Resonant Frequencies of vehicle parts (finding rattles) Most of the interior and exterior parts of a vehicle, and even furniture and other items in a living room can be subject to mechanical resonance. A door panel for instance, at some frequency it has a natural resonance frequency, or a frequency at which it will start to vibrate due to its physical properties.

  • Page 11: Using The Im-Sg+ To Tune The Response Of An Audio System

    Using the IM-SG+ to tune the response of an audio system By using the IM-SG+ with an audio spectrum analyzer (RTA) or with a inexpensive handheld SPL meter, it is possible to analyze the frequency response of an entire audio system and correct the response with equalization or by swapping phase of individual speakers, or by adjusting crossover points.
  • Page 12 Using the IM-SG+ to tune the response of an audio system - continued SPL Meter Method Connect IM-SG+ to any auxiliary input of a source unit or amplifier to use the IM-SG+ as a sine wave generator. Turn the volume of the source unit or amplifier gain down.

  • Page 13: Checking The Impedance Of Speaker Cables Or Signal Cables

    Checking the Impedance of Speaker Cables or Signal Cables With the IM-SG+'s low impedance mode and harness compensation it is easy to test the impedance of power wire, speaker cables, signal cables, and more. A few examples are listed below. Testing Power Cable 1.
  • Page 14 Checking the Impedance of Speaker Cables or Signal Cables - continued 4. Wait for the impedance reading to settle before reading it 5. This is a good way to compare two different types of wire as long as types are the same length. 6.

  • Page 15: Checking The Final Speaker Load On An Amplifier

    Checking the Final Speaker Load on an Amplifier With the IM-SG+ it is possible and useful to test the impedance of a speaker system be it a component set, an individual speaker, or a multi subwoofer setup. 1. To measure the f , make sure the room or area around the subwoofer is quiet and free from moving air.

  • Page 16: S )

    Finding the f of a Raw Speaker Driver The f is the speaker's natural resonant frequency. This will give you some idea of the usable bandwidth of the speaker. Generally the speaker will not produce usable output below the frequency of f 1.
  • Page 17 Figure 1, Impedance curve of a single 4 ohm voice coil, 15 inch subwoofer. Notice the f at 24 Hz.

  • Page 18: The Significance Of F

    The Significance of f Subwoofer - The f value of a subwoofer is the frequency at which the cone naturally resonates or vibrates at. This is one of the factors that determine how low a subwoofer will play. Example: A subwoofer with an f of 35 Hz is going to have a harder time trying to reproduce a 25 Hz tone than a subwoofer with a f...
  • Page 19 The Significance of f - Continued Tweeter - Most tweeters have a measurable f frequency. There are some types of tweeters, (ribbons for instance) that have an almost flat impedance across its operating range. For this type of tweeter, follow manufacturer's recommendations for crossover frequency.
  • Page 20 Figure 2, Impedance curve of a typical 4 ohm, 1" tweeter. Notice the f at 1.59 kHz...

  • Page 21: C )

    Finding the f of a Sealed Box Subwoofer System 1. The f is the driver's natural resonant frequency while in the sealed enclosure. This will give you some idea of the usable bandwidth of the speaker. Generally, the output of the sealed subwoofer system will start to decrease as the frequency goes below f 2.
  • Page 22 Figure 3, f of a single 4 ohm, 15 inch subwoofer in a 2 cubic feet sealed box.

  • Page 23: Tc )

    Finding the Q of a Sealed Box Subwoofer System The Q of a sealed subwoofer box system will give you some idea of how the frequency response of the system might be. The effects of different Sealed Box Subwoofer Q values are shown in the chart below.
  • Page 24 Figure 4 For a given driver, the Q of the sealed subwoofer box system will be affected directly by the volume of the enclosure. The larger the enclosure, the lower the Q value will be. The box can be stuffed with polyester stuffing or lined with fiberglass insulation to make adjustments to the enclosure's Q value.

  • Page 25: Finding The Volume Of A Subwoofer Enclosure

    Finding the Volume of a Subwoofer Enclosure By taking some measurements with the IM-SG+ and knowing two of the T/S parameters of the driver, it is possible to find the exact volume of a subwoofer enclosure. For this method to work, the enclosure has to be completely sealed. As such it may not be possible to use this method on a ported enclosure unless it is possible to seal off the port completely.
  • Page 26 determine the volume of the enclosure using the following formula. �� ���� �� �� �� �� − 1) �� �� 7. On our sample 12 inch subwoofer driver used in the Finding the Thiele / Small (T/S) parameters of a driver section we measured the f to be 27.1 Hz.

  • Page 27: B )

    Finding the Tuning Frequency of a Ported Subwoofer Box System (f The f is the resonant frequency of the ported subwoofer enclosure. Measuring this will give you some idea of the usable bandwidth of the speaker and also if the target tuning frequency when constructing the enclosure was met.
  • Page 28 Finding the Tuning Frequency of a Ported Subwoofer Box System (f ) - continued 8. Figure 5 below shows the impedance curve of a 12 inch woofer in a ported box tuned to 30 Hz. The minimum impedance between the two peaks is f , the tuning frequency.

  • Page 29: B )

    Finding the Tuning Frequency of a Passive Radiator Subwoofer Box System (f Finding the tuning frequency of a passive radiator subwoofer box system (f ) is exactly the same procedure as finding the tuning frequency for a ported box. Follow the instructions for Finding the Tuning Frequency of a Ported Subwoofer Box System on page 18.

  • Page 30: P )

    Finding the Resonant Frequency of a raw Passive Radiator (f 1. Connect IM-SG+ to any auxiliary input of a source unit or amplifier to use the IM-SG+ as a signal generator. Turn the volume of the source unit or amplifier gain down. 2.

  • Page 31: Finding The Characteristics Of 4Th Order Bandpass Box

    Finding the characteristics of a 4th order Bandpass Box (single reflex) 1. With the IM-SG+, it is possible to find the port tuning frequency and the approximate bandwidth of a single reflex bandpass subwoofer system. 2. To measure the impedance characteristics of the subwoofer system, make sure the room or area around the subwoofer is quiet and free from moving air.
  • Page 32 Finding the characteristics of a 4th order Bandpass Box (single reflex) - continued 9. f and f tell us about the usable bandwidth of the system. Output of the subwoofer will start to decrease at frequencies below f and subwoofer output will decrease at frequencies higher than f Figure 6, the impedance curve of a single 4 ohm voice coil subwoofer in a single reflex bandpass enclosure (4th order).

  • Page 33: Finding The Thiele / Small (T/S) Paramters Of A Driver

    Finding the Thiele / Small (T/S) parameters of a driver (Advanced Topic) You don't need more equipment and a computer to do this. With the IM-SG+, a small digital postage scale, and some play dough or coins; it is possible to derive all the T/S parameters that are needed to design a perfect custom subwoofer enclosure specific for your driver.
  • Page 34 Finding the Thiele / Small (T/S) parameters of a driver - continued Speaker Type Range Subwoofer 10 - 70 Hz Midbass 20 - 150 Hz Midrange 30 - 900 Hz 6. Record the frequency where the impedance reaches its maximum value within the range above. This Frequency is the f 7.
  • Page 35 Finding the Thiele / Small (T/S) parameters of a driver - continued represents an impedance that we are going to try to find with the IM-SG+. This impedance will happen twice, once at a frequency lower than the f and once at a frequency higher than the f .
  • Page 36 Finding the Thiele / Small (T/S) parameters of a driver - continued Figure 8, finding f and f 12. To find Q plug in the recorded values for F and F into the equation below. �� �� �� √ �� ��...
  • Page 37 Finding the Thiele / Small (T/S) parameters of a driver - continued 13. Now calculate and record Q using this formula �� ���� �� ���� (�� − 1) �� Using the measurements from our test woofer we get: 3.21 �� ����...
  • Page 38 Finding the Thiele / Small (T/S) parameters of a driver - continued 15. To measure the V we need to add some mass to the cone and re-measure the f with the mass on the cone. We found that play dough or modeling clay works well because it is easy to make various weights and it molds easily onto the cone.
  • Page 39 Finding the Thiele / Small (T/S) parameters of a driver - continued For our sample we used 135 grams and measured the new impedance peak to be 21.3 Hz. So MA = 135 and f 21.3 MA = 18. Calculate F with by plugging in F and F into the...
  • Page 40 Finding the Thiele / Small (T/S) parameters of a driver - continued Photo 1 From the measured value of the diameter, D, we can calculate the cone area with this formula �� ���� (���� ������������ ������ℎ����) = ( ∗ π So, for our woofer which measured 10 inches from center of surround to center of surround we get: ����...
  • Page 41 Finding the Thiele / Small (T/S) parameters of a driver - continued 21. Calculate and record M ���� �� ���� 106.13 For our example we get 78.5 �� ���� 106.13 So, M = 6.6 grams 22. Calculate and record M ��...
  • Page 42 Finding the Thiele / Small (T/S) parameters of a driver – continued 23. Calculate and record C �� = 1000/((2 ∗ �� ∗ �� ∗ �� ���� �� ���� For our example we get �� = 1000/((2 ∗ 3.14 ∗ 27.1) ∗...
  • Page 43 Finding the Thiele / Small (T/S) parameters of a driver - continued Table of parameters found in this process, in order, from 12 inch woofer used in example. Ohms 27.1 38.3 Ohms 11.4 Ohms 3.21 unitless 0.31 unitless 0.28 unitless 224.6 grams 0.000154...
  • Page 44 Notes:...
  • Page 45 Notes:...

  • Page 46: Troubleshooting

    Troubleshooting: Problem: The LCD displays “battery bad replace now” and won’t go to next screen Solution: Replace battery Problem: It won’t change ranges or to pink noise by short pressing Range button Solution: Make sure the impedance being measured is greater than 0.5 ohms.
  • Page 47 Troubleshooting - continued: Problem: Some high frequency chirping can be heard when generating frequencies under 200 Hz. Solution: This is normal and should not affect any measurements or readings. It is an artifact in the 10 order harmonic. We actually consider it a feature as the low frequencies can be difficult to hear at low volumes so it serves as a bit of audio feedback for us as we use it, but at such an attenuated level compared to the fundamental...
  • Page 48 Limited Warranty - continued Any applicable implied warranties are limited in duration to the period of one year beginning with the date of the original purchase. No warranties shall apply to this product thereafter. Some states do not allow limitations on implied warranties;...

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