Supreem Circuits Diagram and Projects: Speakers

Loudspeaker Impedance Meter

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Also suitable for Headphones Operates in conjunction with a DVM</div>
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A   simple Impedance Meter can be useful to measure the actual impedance a   loudspeaker or headphone is presenting @ 1kHz standard frequency. The   circuit, designed on request, relies on an earlier design   (Spot-frequency Sine wave Generator) to obtain a stable, low distortion   1kHz sine wave avoiding the use of thermistors, bulbs or any special   amplitude-limiting device. The sine wave output, after some amplitude   setting obtained by means of P1, is sent to the device under measurement   through a resistor.</div>
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A regulated supply is necessary  to obtain a  stable output waveform. D1 and D2 force IC1 to deliver 6.2V  output  instead of the nominal 5V. The measurement is done in two  stages: as a  constant current supply of the device under test is  necessary, this can  be set at first by adjusting P1 and measured across  the series resistor  (R7 or R8, depending on the impedance value to be  measured); then, the  meter is switched across the device under test and  the actual impedance  will be read directly on the meter display.<br />
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<b>Circuit diagram:</b></div>
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<b><a href="http://lh4.ggpht.com/-psKYFW7kyJc/T48BHTevxII/AAAAAAAAFHI/CeAgcdea2z8/s1600-h/Loudspeaker%252520Impedance%252520Meter%252520Circuit%252520Daigram%25255B5%25255D.gif"><img alt="Loudspeaker Impedance Meter Circuit Daigram" border="0" height="256" src="http://lh4.ggpht.com/-tuVys0J8960/T48BJEC0Q3I/AAAAAAAAFHQ/sjjhfRWLK2c/Loudspeaker%252520Impedance%252520Meter%252520Circuit%252520Daigram_thumb%25255B3%25255D.gif?imgmax=800" style="border-color: -moz-use-text-color; border-style: none; border-width: 0px; display: block; float: none; margin-left: auto; margin-right: auto;" title="Loudspeaker Impedance Meter Circuit Daigram" width="383" /></a>Loudspeaker Impedance Meter Circuit Diagram </b></div>
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<b>Parts:</b></h5>
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<pre>P1_______________4K7  Linear Potentiometer
R1______________12K  1/4W Resistor
R2_______________2K2 1/4W Resistor
R3_______________1K  1/2W Trimmer (Cermet)
R4_______________1K5 1/4W Resistor
R5_______________4K7 1/4W Resistor
R6_______________3K3 1/4W Resistor
R7_____________100R  1/4W Resistor (See Notes)
R8_______________1K  1/4W Resistor (See Notes)
R9_______________1K  1/4W Resistor (Optional)
C1______________22nF  63V Polyester Capacitor
C2_____________330nF  63V Polyester Capacitor
C3______________22µF  25V Electrolytic Capacitor
D1,D2_________1N4148  75V 150mA Diodes
D3_______________3mm  Red LED (Optional)
Q1,Q2,Q3_______BC550C 45V 100mA Low noise High gain NPN Transistors
IC1____________78L05   5V 100mA Regulator IC
SW1,SW2_________SPDT Toggle or Slider Switches
SW3_____________SPST Toggle or Slider Switch
B1________________9V  PP3 Battery

Clip for PP3 Battery</pre>
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<b>Circuit set-up using an oscilloscope:</b></div>
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Connect the oscilloscope in place of the DVM and rotate P1 fully clockwise.<br />
Short the speaker output and adjust R3 to obtain a sine wave of about 2.2V peak-to-peak amplitude. </div>
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<b>"By ear" circuit set-up:</b></div>
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Connect  a small loudspeaker or  one of the two earpieces forming a pair of  headphones to the circuit  output and rotate P1 to obtain a moderate  output sound level.<br />
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Carefully adjust R3 until the output sound  will stop; then turn back  the trimmer very slowly and stop adjusting  immediately when the sound  will start again.</div>
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<b>Measurement:</b> </div>
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<li>Connect a Digital Voltage Meter set to 200mV ac range to the DVM output terminals</li>
<li>Connect the device under test to the Speaker terminals</li>
<li>Switch SW1 in the position towards R7 if the impedance value to be measured is below 100 Ohm or towards R8 if above</li>
<li>With SW2 in the "Set" position power-on the circuit by means of SW3</li>
<li>Adjust P1 in order to read exactly 100.0mV on the DVM display</li>
<li>Switch  SW2 in the "Measure" position and read directly the  loudspeaker or  headphones impedance value on the DVM display, e.g.  8.5mV = 8.5 Ohm</li>
<li>Please  note that when measuring devices with impedance values above  100 Ohm  (SW1 set towards R8), the decimal point in the DVM reading  must be  ignored. E.g. if the display shows 70.5mV, the impedance will  be 705 Ohm</li>
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<b>Notes:</b></div>
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<li>For very precise measurements use 1% or 2% tolerance resistors for R7 and R8.</li>
<li>D3 LED pilot light and its current limiting resistor R9 are optional.</li>
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<b><a href="http://streampowers.blogspot.com/2012/06/loudspeaker-impedance-meter.html" target="_blank">Streampowers </a></b></div>
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Loudspeaker Impedance Meter

Also suitable for Headphones Operates in conjunction with a DVM A simple Impedance Meter can be useful to measure the actual i...

Loudspeaker Protector Monitors Current

Speakers 04:45

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This  circuit uses a 0.1O 1W resistor connected in  series with the output of  a power amplifier. When the amplifier is  delivering 100W into an 8O  load, the resistor will be dissipating 1.25W.  The resulting temperature  rise is sensed by a thermistor which is  thermally bonded to the  resistor. The thermistor is connected in series  with a resistor string  which is monitored by the non-inverting (+)  inputs of four comparators  in an LM339 quad comparator. All of the  comparator inverting inputs are  connected to an adjustable threshold  voltage provided by trimpot VR1.  As the thermistor heats up, its  resistance increases, raising the  voltage along the resistor ladder.</div>
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<b>Circuit diagram:</b><br />
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<span style="color: black;"><a href="http://lh6.ggpht.com/-xRxa9SpHm4s/TfEjsOw4J3I/AAAAAAAACjI/aQTLbssjVQQ/s1600-h/loudspeaker-protector-circuit-diagram-monitors-current%25255B6%25255D.jpg" target="_blank"><img alt="loudspeaker-protector-circuit-diagram-monitors-current" border="0" height="482" src="http://lh4.ggpht.com/-pLk1S22lDB8/TfEjwnooZFI/AAAAAAAACjM/ywqZHCIVmcA/loudspeaker-protector-circuit-diagram-monitors-current_thumb%25255B4%25255D.jpg?imgmax=800" style="border-bottom: 0px; border-left: 0px; border-right: 0px; border-top: 0px; display: block; float: none; margin-left: auto; margin-right: auto;" title="loudspeaker-protector-circuit-diagram-monitors-current" width="506" /></a></span> <b>Loudspeaker Protector Circuit Diagram</b></div>
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When  the voltage on the non-inverting input  of each comparator exceeds the  voltage at its inverting input, the  output switches high and illuminates  the relevant LED. NOR gate latches  are connected to the outputs of the  third and fourth comparators. When  the third comparator switches high,  the first latch is set, turning on  Q1 and relay 1. This switches in an  attenuation network (resistors RA  & RB) to reduce the power level.  However, if the power level is  still excessive, comparator 4 will  switch, setting its latch and  turning on Q2 and relay 2.</div>
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This  disconnects the loudspeaker load. The  thermistor then needs to cool  down before normal operation will be  restored. The values of R1-R4  depend on the thermistor used. For  example, if a thermistor with a  resistance of 1.5kO at 25°C is used,  then R1 could be around 1.5kO and  R2, R3 and R4 would each be 100O  (depending the temperature coefficient  of the thermistor). The setup  procedure involves connecting a sinewave  oscillator to the input of the  power amplifier and using a dummy load  for the output. Set the power  level desired and adjust trimpot VR1 to  light LED1. Then increase the  power to check that the other LEDs light  at satisfactory levels.<br />
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Source by : <span style="color: black;"><a href="http://streampowers.blogspot.com/2012/06/loudspeaker-protector-monitors-current.html" target="_blank">Streampowers </a></span></div>
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Loudspeaker Protector Monitors Current

This circuit uses a 0.1O 1W resistor connected in series with the output of a power amplifier. When the amplifier is delivering...

Crossover For Subwoofer

Speakers 08:05

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The  crossover network is intended for use when an  existing audio  installation is to be extended by the addition of a  subwoofer. Often,  this additional loudspeaker is one that has been lying  around for some  time. If its frequency response extends down far  enough, all is well  and good, but a filter is then needed to cut off any  frequencies above,  say, 150 Hz. Often, a subwoofer network is an active  filter, but here  this would necessitate an additional power supply. The  present network  is a passive one, designed so that the speaker signal  of the existing  system can be used as the input signal.</div>
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<b>Circuit diagram:</b><br />
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<b> Crossover Circuit Diagram For Subwoofer</b></div>
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Since  the bass information is present in  both (stereo) loudspeakers, the  signal for the sub woofer can simply be  tapped from one of them. The  network is a 1st order low-pass filter  with variable input (P1) and  presettable cut-off frequency (P2). The  signal from the loudspeaker is  applied to terminal ‘LSP’. Voltage  divider R1-R2-P1 is designed for use  with the output signal of an  average output amplifier of around d 50 W.  The crossover frequency of  the network may be varied between 50 Hz and  160 Hz with P2. The values  of R3, P2, and C1, are calculated on the  assumption that the subwoofer  amplifier to be connected to K1 has a  standard input resistance of 47  kΩ.</div>
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If this  figure is lower, the value of C1  will need to be increased slightly. It  is advisable to open the volume  of the subwoofer amplifier fully and  adjust the sound level with P1.  This ensures that the input of the  subwoofer amplifier cannot be  overloaded or damaged. Make sure that the  ground of the loudspeaker  signal line is linked to the ground of the  subwoofer amplifier. If  phase reversal is required, this is best done by  reversing the wires to  the subwoofer. If notwithstanding the above  additional protection is  desired at the input of the subwoofer  amplifier, this is best effected  by ‘overload protection ’ elsewhere in  this site.<br />
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Source by : <span style="color: black;"><a href="http://streampowers.blogspot.com/2012/06/crossover-for-subwoofer.html" target="_blank">Streampowers </a></span></div>
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Crossover For Subwoofer

The crossover network is intended for use when an existing audio installation is to be extended by the addition of a subwoofer....

Crowbar Speaker Protection

Speakers 01:26

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Crowbar  circuits are so-called because their  operation is the equivalent of  dropping a crowbar (large steel digging  implement) across the  terminals. It is only ever used as a last resort,  and can only be used  where the attached circuit is properly fused or  incorporates other  protective measures.</div>
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A  crowbar circuit is potentially destructive  - if the circuitry only has a  minor fault, it will be a major fault by  the time a crowbar has done  its job. It is not uncommon for the  crowbar circuit to be destroyed as  well - the purpose is to protect the  device(s) attached to the circuit -  in this case, a loudspeaker.   </div>
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<b>Description</b>    </div>
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There's  really nothing to it. A resistor / capacitor circuit isolates  the  trigger circuit from normal AC signals. Should there be enough DC  to  activate the DIAC trigger, the cap is discharged into the gate of  the  TRIAC, which instantly turns on ... hard. A TRIAC has two basic  states,  on and off. The in-between state exists, but is so fast that it  can be  ignored for all intents and purposes.</div>
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<span style="color: black;"><a href="http://lh5.ggpht.com/-eqgcsHalaDo/TfElj95U39I/AAAAAAAACjQ/aDDVepjXfgs/s1600-h/Crowbar%252520Speaker%252520Protection%25255B6%25255D.gif" target="_blank"><img alt="Crowbar Speaker Protection" border="0" height="149" src="http://lh4.ggpht.com/-F-AOC1-zPcY/TfElnPTCXeI/AAAAAAAACjU/2vGeBTmomoM/Crowbar%252520Speaker%252520Protection_thumb%25255B4%25255D.gif?imgmax=800" style="border-color: -moz-use-text-color; border-style: none; border-width: 0px; display: block; float: none; margin-left: auto; margin-right: auto;" title="Crowbar Speaker Protection" width="349" /></a></span> <b>Figure 1 - Crowbar Speaker Protector</b></div>
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The  BR100 DIAC (or the equivalent DB3 from  ST Microelectronics) is rated  for a breakdown voltage of between 28 and  36V - these are not precision  devices. Needless to say, using the  circuit with supply voltages less  than around 40V is not recommended,  as you will have a false sense of  security. The supply voltage must be  higher than the breakdown voltage  of the DIAC, or it cannot conduct.  Zeners cannot be used as a substitute  for lower voltages - a DIAC has a  negative impedance characteristic, so  when it conducts, it will dump  almost the full charge in C1 into the  gate of the TRIAC. This is  essential to make sure the TRIAC is switched  into conduction.</div>
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The TRIAC is a common type, and  may be  substituted if you know the specifications. It's rated at 12A,  but the  peak current (non-repetitive) is 95A, and it only needs to  sustain that  until the fuse (or an output transistor) blows. A heatsink  is  preferred, but there is a good chance that the TRIAC will blow up if  it  has to protect your speakers, so it may not matter too much. The 0.47   ohm resistor is simply to ensure that the short circuit isn't absolute.   This will limit the current a little, and increases the chance that the   TRIAC will survive (albeit marginally). Feel free to use a BT139 if it   makes you feel better - these are rated at 16A continuous, and 140A   non-repetitive peak current.</div>
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The peak short  circuit current will  typically be about 90A for a ±60V supply, allowing  ~0.2 ohms for wiring  resistance and the intrinsic internal resistance of  the TRIAC, plus  the equivalent series resistance of the filter  capacitors. That's a  seriously high current, and it will do an injury to  anything that's  part of the discharge path. Such high currents are not  advised for  filter caps either, but being non-repetitive they will  almost certainly  survive.</div>
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<b>Construction & Use</b>    </div>
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Apart  from the obvious requirement that you don't make any mistakes,   construction is not critical. Wiring needs to be of a reasonable gauge,   and should be tied down with cable ties or similar. C1 must be   polyester. While a non-polarised electrolytic would seem to be   acceptable, the circuit will operate if the capacitor should dry out   over the years. This means it will lose capacitance, and at some point,   the crowbar may operate on normal programme material. This would not be   good, as it will blow up your amplifier!</div>
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Make  sure that all connections are secure  and well soldered. Remember that  this is the last chance for your  speakers, so it needs to be able to  remain inactive for years and years  - hopefully it will never happen.  The circuit doesn't have to be  mounted in the amplifier chassis - it can  be installed in your speaker  cabinet. Nothing gets hot unless it  operates, at which point no-one  really cares - it just has to save the  speakers from destruction once  to have been worthwhile.</div>
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Remember  that the crowbar circuit absolutely  must never be allowed to operate  with any normal signal. A perfectly  good amplifier that triggers the  circuit because of a high-level bass  signal (for example) will very  likely be seriously damaged if the  crowbar activates. To verify that no  signal can trigger it, you may  want to (temporarily) use a small lamp in  place of R2, and drive the  amp to maximum power with bass-heavy  material.</div>
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A speaker does not need to be  connected. If  the lamp flashes, your amp would have been damaged. If  this occurs, you  may want to increase the value of C1. Note that bipolar  electrolytics  should never be used for C1, because they can dry out and  lose  capacitance as they age. This could cause the circuit to  false-trigger.</div>
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Source by : <span style="color: black;"><a href="http://streampowers.blogspot.com/2012/06/crowbar-speaker-protection.html" target="_blank">Streampowers </a></span></div>
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Crowbar Speaker Protection

Crowbar circuits are so-called because their operation is the equivalent of dropping a crowbar (large steel digging implement) ...

Sub-Woofer and Controller Circuit Diagram

Projects, Speakers 00:09

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<b>This is a simple Sub-Woofer and Controller Circuit Diagram. Sub woofers are popular, with home theater being of the driving forces. However, a nice sub adds considerably to normal hi-fi program material, & so if it is predictable & has nice response characteristics.</b><br />
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 all of sub woofers use a immense speaker driver in a immense box, with tuning vents & all the difficulties (& vagaries) that conventional operation entails. By conventional, I mean that the speaker & cabinet are operated as a resonant technique, using the Thistle-Small parameters to get a box which will (if everything works as it ought to) provide excellent performance.</div>
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<span style="font-size: small;"><b>Completed Prototype</b></span></div>
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A fast word is warranted here, to let you decide if the speaker you have will actually work in a little sealed enclosure. The EAS principle will permit any driver to extend to twenty Hz or even lower. A lovely fast check is to stick the speaker in a box, and drive it to 100W or so at twenty Hz - you ought to see lots of cone movement, a few things will rattle, but you should not actually listen to a tone. A "bad" speaker will generate 60 Hz (third harmonic) - in the event you don't listen to anything, the speaker will work in an equalized sub.</div>
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If a tone is audible, or the speaker shows any signs of distress (such as the cone breaking up with appropriate terrible noises), then the driver cannot be used in this manner. Either discover a different driver, or use a vented enclosure.</div>
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Before you can build your own EAS box, you will require to pick an appropriate driver, using the above as a guide. Cone tour will be high at the lowest frequencies, so the speaker needs to be able to high power, lovely tour, & of reasonable size (there is no substitute for cone area for moving air at low frequencies). I am using a 380mm (15") driver, but smaller drivers (say 300mm - 12") can be used, or even a bigger number of smaller drivers. I have also had excellent results with a single 300mm driver, which has lower sensitivity (as would expect) but is perfectly adequate for normal usage.</div>
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The check methods I used are applicable to any combination, but in general I recommend either a single giant driver or a pair of (say) 300mm units. The next hurdle is the amplifier needed to drive the speaker. This is not trivial. If the selected driver has a sensitivity of 93dB / W @ one metre, then you can safely assume that the efficiency will be less than this below resonance, by a factor of possibly 6dB or more. In case you are used to driving a sub with 100W, this means that you have increased the power to 400W - although this is an over-simplification.<br />
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If they are to operate the sub from 60Hz (my aim from the outset), they will increase the power by 12dB for each octave, so if 20W is necessary at 60Hz, then at 30Hz this has increased to 320W, & at 15Hz, you will require over 5kW.<br />
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Fortunately, the reality is a tiny different, & 400W or so will be over sufficient for a powerful process, due chiefly to the fact that the energy content in the low bass region is not normally all that great. (Although some program material may have high energy content, in general this is not the case). The EAS process augments the existing process, which is allowed to roll off naturally - contrast this with the normal case, where a crossover is used to separate the low bass from the main process, so existing speaker capability is lost.</div>
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The box I built is made from 25mm (1") MDF (Medium Density Fiberboard), & filled with fiberglass. Apart from the fact that it is very heavy (which is a lovely thing, because it desires to walk with low frequencies), the cabinet is acoustically dead, with no resonances in the low frequencies at all ( unlike my house & furniture, dammit !). The woofer is recessed in to the baffle, & sealed with weather sealing foam. When attaching the speaker, do NOT use wood screws, or any other screw in to the MDF. I used "Tee" nuts. I have no idea what they are called elsewhere in the world, but they look like this</div>
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<b>TEE NUT</b></div>
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The middle is tapped, and accepts a metal thread screw, and the small spikes mean that you must drill a hole, and hammer in the Tee nut. In case you use a screw through the hole and screwed lightly in to the Tee nut, you can hold it in place as you bash away at it, and can also see that it is straight when you are done. make sure that the finish of the screw doesn't stick out the finish, or you will seldom remove it again after the hammering! I recommend that you lock the tee nut in to place with some construction adhesive (don't get any in the threaded section) so they don't fall out while you are installing the speaker.</div>
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<b>The EAS Controller</b><br />
The controller is (actually very) simple, & the circuit is shown in Figure one. An input buffer ensures that the input impedance of the source does not affect the integrator performance, & allows summing of left & right channels without any crosstalk. The output provides a phase reversal switch, so that the sub can be properly phased to the remainder of the process. If the mid-bass disappears as you advance the level control, then the phase is wrong, so switch to the opposite position.</div>
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<b><small>Figure 1 - The Original EAS Filter / Controller</small></b></div>
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It turns out that the controller can be simplified, but there is no point. While the dual pot appeared like a lovely suggestion when I built my unit, it actually only changes the gain. Now, having experimented some more, this is an excellent thing, since it means that the level through the controller can be set to make positive that there is no distortion - there can be a immense amount of gain at low frequencies, & if the gain is high, distortion is assured!<br />
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The integrators (U1B & U2A) include shelving resistors (R6 & R9), & the capacitor / resistor networks (C1-R4, C3-R7) be positive that signals below 20Hz are attenuated. In case you don't require to go that low, then the worth of the caps (or the resistors R4 & R7) can be reduced. I used four.7uF caps, & these are non-polarized electrolytic - a high value was needed to keep the impedance low to the integrators. I originally included the dual pot (VR1) to permit the upper frequency roll off to be set - however it does no such thing (as described above). The final output level is set with VR2, which may be left out if your power amp has a level control.</div>
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It is OK to substitute different op amps, but there is tiny reason to do so. Any substitution tool ought to be a FET input op amp, or DC offset may be an issue. Do not be tempted to make use of a DC coupled amp. If the you are planning to make use of is DC coupled, the input ought to be isolated with a capacitor. Pick a value to give a -3dB frequency of about 10Hz, as this will have tiny effect on the low frequency response, but will help to attenuate the subsonic frequencies.<br />
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The unity gain range (using a 20k pot as shown) is from 53Hz to 159Hz. This ought to be sufficient for most systems, but if desired, the resistors (R5 & R8) can be increased in value to 22k, or you can select a bigger value pot. Using 22k resistors & the 20k pot will give a range from 36Hz to 72Hz.</div>
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To permit lower frequencies, you can increase the 100k shelving resistors (R6 and R9) to 220k, and increase the high pass capacitors (four.7uF) with 10uF (or R4 & R7 may be increased - a maximum of four.7k is recommended). This will give a turnover frequency of around 8Hz, but expect to make use of much more power, as there will likely be significant sub-sonic energy that will generate huge cone excursions with no audible benefit.<br />
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The input must be a standard full range (or for a stampeded method, the whole low frequency signal). Do not use a crossover or other filter before the EAS controller. For final modification, and to integrate the method in to your listening room, I recommend the constant-Q equalizer. The final result using this is extraordinarily nice - I have flat in-room response to 20Hz!</div>
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For the power supply, use the in anything else will provide +/-15V at a few Milli amps. My supply is not even regulated, & the whole method is as close to noiseless as you will listen to (or not listen to). Construction is not critical - I built mine on a piece of Overboard (perforated prototype board), & managed to fit everything (including the power supply rectifier & filter) on a piece about 100 x 40 millimeters with room to spare.<br />
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The EAS method is surprisingly simple to set up with no instrumentation. Of coursework in case you have an SPL meter & oscillator you can also confirm the settings with measurements. Keep in mind that the room acoustics will play havoc with the results, so unless you require to drag the whole method outside, setting by ear might be the simplest. Even in case you did get it exactly right in an anechoic surroundings, this would alter one time it was in your listening room anyway.<br />
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It takes a small experimentation to get right, but is surprisingly simple to do. When properly set, a check track (or bass guitar) ought to be smooth from the highest bass note to the lowest, with no gross peaks or dips. Some are inevitable because of room resonances & the like, but you will discover a setting that sounds "right" with small difficulty.</div>
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<b>Performance Of My Prototype</b><br />
I measured 80dB SPL at one meter in my workshop (sub-woofer perched on a chair in more or less the middle of the space) with at 25Hz & 70W. This improved dramatically when the unit was installed in the listening room, but as I said earlier, there is usually not a lot recorded below around 35Hz. The longest pipe on the organ is usually about 16Hz, but larger pipes still may be used. It was found necessary to cease group of diapasons (able to 8Hz) in the famous Sydney Town Hall organ because when they were used, the very low frequency caused building destroy.</div>
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A couple of orchestral recordings revealed traffic (or perhaps underground railway) rumble that I was unaware of before (however this was before it was set correctly, and the bass was a tad louder than needed). One time set up properly, its presence is unobtrusive - except I now have about and a half octaves of additional bottom finish.</div>
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I finally decided on a 20Hz maximum frequency (-3dB), and this is reflected in the part values shown in Figure one. The actual roll-over frequency is 16.5Hz, after which the output is attenuated at about 12dB / octave (see Figure two). Without the roll off capacitors, the gain would be 20dB at 20Hz. Unity gain frequencies are about 4Hz and 63Hz with the 20k pot(s) centered.</div>
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<span style="font-size: small;"><b>Figure 2 - Frequency Response of EAS Controller</b></span></div>
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awesome Australian readers may recognize the woofer brand in the picture (Figure three) of my done unit. The compact size of the box can be seen from the fact that there is tiny spacing around the speaker itself, and most of what is there is the top and sides - I used 25mm MDF, so it makes the outside of the box a bit bigger than the inside. Outside dimensions are 470W x 450H x 410D (18 1/2"W x 17 1/2"H x 16"D), which gives a capacity of 60 liters (about two.1 ftÂ³ - excluding the internal space occupied by the speaker. I think you would agree that this is a small box indeed for a 380mm loudspeaker that performs down to 15Hz.</div>
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<span style="font-size: small;"><b>Figure 3 - Photo of Completed EAS Cabinet</b></span></div>
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Overall, I would must say that I doubt that any conventional design would be as compact, or would have such clarity & solidarity. Being a sealed box, there is not of the "waffle" that ported designs often give, & the speaker is protected against excessive tour by the air pressure in the box itself (below the cutoff frequency, anyway).</div>
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The bottom finish in my technique is now staggering. It is rock solid, & absolutely thunders when called on. The 400W amp is over sufficient for the job, thinking about it's to keep up with a biamped main technique able to high SPL (up to 120dB at my listening position). In fact a fast check indicates that 200W would have been (but \. better to have it & not require it than require it & not have it).</div>
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The fact that the EAS design augments the existing speakers than taking over from them with a crossover goes a long way towards ensuring the power requirements do not get out of hand. As an added benefit, I have found that I get the same aural sensation at much lower SPLs - I can listen happily at 90dB, but it sounds much louder. I may even listen to the phone ring while listening now !<br />
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All in all, I feel it is unlikely that anything other than an isobaric enclosure could give the same performance for a box size even close to the EAS box,& even then would be limited to about 35Hz. Added to this is the unpredictable combined response of the main speakers and the sub, which is not an Problem with this design. With an EAS system, more power is necessary than a standard design, but for plenty of people, power is less costly than space.</div>
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