Little things we've found to get more thump for your buck
I designed this childishly simply system over 30 years ago, (see below) back in the days of the discrete four channel revolution. At first it was just supposed to be an alternative low cost way to get the rear channels and reverb effects without having to replace all of my then "state of the art" stereo equipment with a new quad system. It worked so well that I've continued to use it . In my opinion this passive system works much better on standard recordings than the 5.1 simulator does. I've set up a simple speaker selector to switch the speakers back and forth between the systems to have the best of both worlds. The only time I actually use the 5.1 system now is with a movie that has mega THX or surround sound effects encoded in it. In my opinion I think that most of the movies and especially CD's sound much more natural with the passive system than with my full blown 5.1 system.
Circuit Overview:
In a system without a sub woofer the main L & R front speakers should be high quality "full range" speakers that will handle the amps' full power output. The rest of the speakers can be lower power full range units. The center channel speaker should be shielded if it's to be used near a TV. In a system with a sub woofer, you only need to use speakers that handle the midrange and upper bass frequencies above the sub's crossover point. These speakers can be the much smaller easier to hide satellite variety that are widely available for a low to modest cost.
The main advantage to this passive surround system is that you don't have to have an expensive 4 or 5.1 channel surround amp to get 90% of the surround or THX effect, That old 2 channel monster amp you have hiding in the closet gathering dust will work like it never did before. One of the beauties of this system, aside from the low cost, is that this system works extremely well with "standard" stereo recordings. It will recover the ambient echo, delay and reverb while enhancing the performers location and presence dramatically. You will hear embedded sounds from your recordings that you didn't even know existed before, especially live concert recordings. When I get time, some free time, (yea right!! hehe) I'll post the theory of operation here.
Note for musicians: This system works extremely well with all standard 2 channel PA systems commonly used. All you need to do is locate the rear speakers behind the audience. You'll be pleasently suprised at how much it will improve the live sound that your audience hears.
FAQ: How do I choose the right power rated speaker for my amplifier?
Answer: The RMS power rating of a speaker should allways be equal to or greater than the RMS power rating of the amplifier driving it. The peak power rating of a driver only indicates the instantaneous peak power a driver can incure without mechanical failure. Over powering any speaker, no matter what brand it is, will eventually result in voice coil or mechanical failure of the driver!
FAQ: How do I hook up speakers to my amplifiers?
Answer:
The receiver line output feeds into the amplifiers for front, rear and subs. (you may need a equilizer with additional outputs)
The sub amplifier drives the subwoofer from the bridged outputs.
the front and rear speakers should be fed from individual channels from the Receiver or another totally separate amplifier.
A power rating of 20 to 50 Watts RMS per channel is more than enough for Mids and Highs.
Here is how I'd hook up your system:
I would dedicate 1 power amp for the subwoofer by itself.
In that configuration: The receiver source L & R RCA's feeds the outboard power amp. If the receiver source is not a subwoofer only (low frequency only) output then you'll need to add an active 2 way high impedance crossover to eliminate any high frequency program from the sub woofer amplifier input. With an external 2-way crossover you can also adjust the sub gain and add +12 dB of bass boost. Hook the subwoofer up to the amp in a bridged mono configuration.
To adjust and balance the system out, keep the receiver tone controls or EQ flat, especially on the bass end and add the +12 dB bass boost from the crossover (turn it on) and by adjusting the subwoofer amplifiers gain. Balance to taste trying to get as linear (or flat) response across the band as possible with a broad range of music. After the system is balanced you can add a touch of bass or treble as needed for a particular song to suit your preference in listening.
>I'm also looking at 4 more tweeters as well. How should I divide them up?
Mount two tweeters somewhere on the dash (maybe inside the A/C vents) for L & R running off of the existing receivers normal speaker outputs for the L & R. I'd mount 1 in the center of the dash (poss. A/C vent ?) The center channel tweeter will need to be a summed L+R wiring hookup.
The center channel wiring is done by putting 2 - 25 Watt 4 Ohm resistors into the tweeter circuit. Here is how to wire it. Take the L (+) speaker output from your receiver, hook it up to one side of the first 4 Ohm resistor, take the other end of the 1 st 4 Ohm resistor and hook it up to the tweeters (+) crossover terminal. Duplicate the process for the R side. Take the R (+) speaker output from your receiver, hook it up to one side of the second 4 Ohm resistor, take the other end of the 2 nd 4 Ohm resistor and hook it up to the tweeters (+) terminal also. (both of the 4 Ohm resistors output ends hook up to the tweeters + crossover terminal) Hook up the tweeters (-) connection to the (- ) speaker output of the receiver (or chassis ground in some cases). This configuration gives you a summed front center channel tweeter for proper sound staging.
In the back: Hook up each tweeter in the normal fashion across the appropriate L an R rear speaker leads.
If you have a spare full range speaker or even a tweeter that can be mounted in the rear center of the car you can also create a center rear channel for even better sound staging.
Here is how to hook it up: Connect the receiver L rear (+) to the (+) terminal of the new rear center speaker or tweeter, and the R rear (+) terminal to the (-) terminal of the new rear center speaker or tweeter.
If you would like to see a drawing of a little more sophisticated version of how all of this is hooked up (See the System at the top of the page)
What is the Optimum Sealed Enclosure for the Performance Teknique 12's?
Answer:
The drivers work best in a sealed enclosure between 1.1 Cu Ft ant 1.6 Cu Ft. The optimum size is about 1.35 Cu Ft. You can go above or below the limits a little bit +/- 20 % but you start to notice a little loss of performance. If the enclosure is below .9 Cu Ft. the lowest octave starts to drop off around 40 Hz if it's above 1.8 Cu Ft. the bass will become less tight and won't have quite as much punch in the lowest octave although it will be a deeper bass. Also if your operating above the upper size recomendation the driver won't be able to handle quite as much power in the lowest octave 20 - 40 Hz because of the increased volume of air (more compliance) there is less resistance to control the cone motion. BTW, this is true of all Subwoofers operating in sealed enclosures outside of their optimum enclosure size that they were designed for.
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The drivers work best in a sealed enclosure between 1.1 Cu Ft ant 1.6 Cu Ft. The optimum size is about 1.35 Cu Ft. You can go above or below the limits a little bit +/- 20 % but you start to notice a little loss of performance. If the enclosure is below .9 Cu Ft. the lowest octave starts to drop off around 40 Hz if it's above 1.8 Cu Ft. the bass will become less tight and won't have quite as much punch in the lowest octave although it will be a deeper bass. Also if your operating above the upper size recomendation the driver won't be able to handle quite as much power in the lowest octave 20 - 40 Hz because of the increased volume of air (more compliance) there is less resistance to control the cone motion. BTW, this is true of all Subwoofers operating in sealed enclosures outside of their optimum enclosure size that they were designed for.
