thch

my definition of SQ is less elitist: "sound the way you want" which, while deceptively simple, is not. I seperate "hi-fi" from "sq". "hi-fi" is an objective goal of making things sound just as they were supposed to. but the end goal is my happiness, so what if I want things to sound different from the recording. Maybe if there was a bit extra warmth, or sparkle, or more depth, I would be happier. That is SQ to me -- acheiving a quality of sound that you enjoy. I only differentiate SQ from SPL/Street with the added constraint that SQ users are not specifically looking for maximum SPL. (SPL user are, and Street users attempt to maximize SPL, but retain some amount of SQ) as for the list, none of that matters in a rickety honda with fart can exaust. gotta have some environment suitable for audio as well.

transistors can be used. each device has a different benefit or flaw. Relay = slow switching, allows current in both directions, requires current to the coil FET = fast switching, current pretty much in 1 direction (not entirely true), no need for current to control the device BJT = fast switcing, current in 1 direction only, small contol current. SRC/TRIAC = application specific. for DC the issue is that they don't turn off... A PFET would be the best alternative to a relay. applying a voltage to the gate would cause the FET to turn off. removing the voltage at the gate would cause the FET to turn on. has a few milliohms of impedance through the device. probably should not go over 50A with a single device. NFETs would also work, but you'd have a 2V or so drop across the device, limiting current to under 10A.

here is a full schematic. values chosen to fit what you'd find at radioshack. note that the metal cased TO220 will have a metal tab at 12V. don't let it touch anything. if you can find a plastic case transistor for 250mA, it will also work. likely the 2n3906 and 2n3904 will work for the npn and pnp transistors, but they are just on the edge with 200mA ratings instead of 250mA ratings. the devices will be saturated, so i don't think they'd burn up or anything.

you know, its funny. earlier yesterday i said "any atom with more or fewer electrons then protons would be an ion". a friend said "no, if it had more it would not be an ion -- it would be a cation". "why is it everyday i have to explain basic set theory to someone" i guess a day has passed. analogy time: cations are a subset of ions square waves are a subset of signals requiring high peak powers.

definatly use the regulation. make sure you have the cap "Co", many regulators seem to have either stability or noise issues if its not there. LM317 is also an option, or LM7805. in both cases you need to have 2 extra resistors to fool them into giving you 6V instead of 1.2V or 5V respectively. 250mA is a lot of idle current. I advise using a relay or some switched source. a TIP31 NPN transistor would be a cheap alternative to a relay. +12V attaches to the collector pin, the base attaches to a 300-1000 ohm resistor which then attaches to the remote wire*. the emitter lead attaches to Vin of the regulator. * - this resistor is there because this type of circuit really isn't the best choise of switching capacitive loads. if the circuit oscillates it will probably block cell phones inside the car, and the noise will likely get past the regulator... the resistor is there to keep the circuit from oscillating.

1.) square waves are AC. you can define a frequency even. 2,) square waves merely show the point the easiest -- they are the worst case scenario. further analysis with square waves is fairly easy.

(Vin)--------| |-----+----/\/\/\-------------(GND) this is the best i can do for a circuit. Vout is seen from the middle node to ground and is the voltage across the resistor. Vin -> 1V, capacitor charges to +1V. (+1V)-------|+1 0|----+------/\/\/\------(0V) Vout = 0V. Vin -> -1V, and at that instant: (-1V)-------|+1 0|------+-----/\/\/\-------(0V) KVL: -(-1V) +1V +Vout = 0 Vout = -2V (+1V)-------|-1 0|------+-----/\/\/\-------(0V) if the cap charges to -1V, then the input switches to +1V, the output will become: -(+1V) -1V +Vout=0, thus Vout = +2V ---------------------------------------------------- obviously this example is applicable for square waves of freqeuncy, f < 1/(8 pi R C) 4 R C for 4 time constants to "fully" charge the capacitor, and 2 pi for radian to Hz conversion. of course there will be overshoot for square waves of higher frequency, but not the doubling shown here. these high peaks will be short lived, and the output will quikly move to 0V, given by (after the switching) |Vout| = 2 e^(-t/RC) peak power is thus 4x what is normally possible. (lets assume R=1). RMS power is lowered though: P = 1/(4RC) Integral(0 to 4RC)(4e^(-2t/RC) dt) P ~ 1/2 (middle steps for anyone interested) u = -2t/RC du = -2/RC dt dt = -RC/2 du P = 1/RC INT ( -RC/2 e^u du) the intgral of e^u du is merely e^u, and e^u is only signifigant at u = 0. at u = -8, the value of e^u is pretty insignifigant, so i'll ignore it. P is then 1/RC * RC/2 of course for lower frequency square waves you'd have a lower RMS power. because the 1/4RC term gets lower and lower, while the integral pretty much stays as RC/2. a typical square wave would have an RMS power, and peak power, of 1 for a 1ohm load.

just something i was looking at today. The basic highpass filter will allow for higher peak voltages then the input has. basically -- if you put in a 1V peak square wave, you can get peaks of 2V from a highpass filter. this is easy to show with RC circuits such as a simple cap inline with the speaker. Square wave goes to 1V. cap charges to 1V. square wave goes to -1V, cap is still charged to 1V. voltage across speaker is now -2V. cap will charge to -1V, square wave chages to +1V, speaker sees +2V. note that RMS power is lower, but peak power is higher. ----------------------------------------------------------------- This brings up two issues: 1.) the peak values can be high, thus higher power amplifiers may be needed to allow for this. basically the peak-power output becomes the metric of choice, but peak power is misrepresented... tragically, some amps may allow for a higher peak output power then 2*RMS for low power signals such as these. 2.) highpass filters focus on differences. this means that the output may need to be able to make very large voltage swings very quickly. possibly the amplifier's slew rate may not be high enough. ----------------------------------------------------------------- now first let me cite some flaws in my argument and tell you that this is for discussion, and as such should not be accepted as "important". in engineering there are often things that do happen, but are not important. some effect might create distortion at 300khz which would be inaudible and isn't too important. flaw 1 -- square waves. amps aren't made for square waves. audio bandwidth is only 20-20khz, square waves have harmonics up to daylight frequencies... so a true square wave input shouldn't be assumed. flaw 2 -- no statistical data. i have not compiled any data as to common songs' characteristics. its possible that natural musical songs do not have properties that emphasize this.

no, typically running this way won't damage the equipment, but it does increase the risk. there are many factors at work here: box size and type, amp class, power supply design, gain setting, HU setting, musical choice, duration of music, woofer design. all of these play a role.

just a small topic that always seems to be explained without being explained. --------------------------------------------- amplifier Gain and DMMs. Most guides that talk about gains and DMMs are a bit simplified. you may want a higher or lower gain. Obviously to set the gain you would need to ask yourself what you are trying to accomplish by setting the gain! but this is overlooked in most guides. --------------------------------------------- ** most guides assume you want maximum undistorted power output from the amp ** Q -- What's wrong with that??? A -- you may not want maximum power. ---------------------------------------------- When you wouldn't want maximum power: * possibly the bass is drowning out the other speakers. * possibly a speaker is distorting badly due to the high power output of the amplifier. the amplifier's power output can be reduced to reduce this distortion. * you need to match the level of one set of speakers to the level of another set. ---------------------------------------------- When you'd want more then maximum power: * your music is not recorded at full levels. * you need the compressive* effects of clipping. **** WARNING -- if you increase gain and allow clipping, you have a higher chance of damaging equipment. While its likely ok for minor clipping for short durations, you should realize that you are intentionally pushing the equipment beyond the rated maximums. **** ---------------------------------------------- So i shouldn't use a DMM? I never said that. it is useful to know where the maximum power without distortion point is on the amp. EXAMPLE -- you have a goal to maximum the output of a system without excessive bass or midrange. basically, loud and sounding reasonably good. in such a case you would set both amps to the maximum gain without distortion setting, then reduce the gain of the amp corresponding with the louder speakers (woofer or mid). ----------------------------------------------- NOTE: If your HU has level adjusting features, you may be able to set all amps in a system to this maximum power without distortion setting, then adjust the levels of the speakers at the HU. * amplitude compression basically means that that lound notes become slightly distorted loud notes, and soft notes become medium-loud notes. the music is louder on average, but has distortion. (edit -- as for the topic discription: basically it refers to the idea of looking for a specific number on the DMM then declaring that "I win" because the number is correct -- even if the resulting setting results in a speaker that is too loud or distorting badly.)

notes on thread: 1.) shunt components are still in the signal path. (#3) 2.) amp class is based upon biasing. there are class AB tube amps. such would be inappropriate for a hybrid amp though. (#4) 3.) sounds like a class-A output stage. and without feedback i'd hope so! (#6) 4.) audio amps are typically a voltage gain stage followed by a current gain stage. (#8) 5.) classA only means the output devices never change states from the active region to a fully on or off region. (#8, #5) 6.) not necessarily MOSFET, but likely given the MOSFET's high input impedance. (#9) 7.) do not run 12AU7, 12AX7, or 12AT7 from 12 volts. (#9) 8.) car tubes might be concidered things like (IIRC) the ECC88 dual triode which unlike the 12AU7 was designed to work at low plate voltages like 12-36 volts. further, something can be done to reduce mechanical noise in the tube. (#15) 9.) some car audio tube amps have placed orange LED's near the tubes to give excessive tube glow. because this is deceptive, it caused controversy. (#15) 10.) home tube amps are allowed to have the large output transformers and the high impedance, high efficinecy speakers that allows tube amps to drive the the speakers. car audio is not known for high efficiency or high impedance speakers. (#16) 11.) nice subjective reviews. (#18, #20)

It'd be interesting to see some filters with passband zeros. an example would be an "elliptic" filter. such filters have a very steep slope near the cutoff freqeuncy, but have a low slope beyond that. basically, past 1/3rd octave it might be -30dB or less, but the slope after this 1/3rd octave would be lower then normal. a limitation of any high slope filter is matching. in this case, things need to be matched moreso then a simple 24db/oct filter, and this may mean that potentiometers are out. either that or use DSP. the benefit of this filter to car audio may become pronounced when the tweeter is located in the dash area and the mid in the door.