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Old 25th July 2012, 06:47 PM   #1
focal1 is offline focal1  United States
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Default Series, Parallel, or custom component setup for 2ch amp?

Hi everyone, I did some searching and I didn't find anything on this forum (or a few others I checked) that seemed to answer my question, so I am hoping for some input.

Firstly, here is the situation:
I have a 1987 SAAB 900, and it has factory 4" front speakers in the dash (facing up towards the windshield) and 4x10" speakers in the back (facing up towards the hatch-back glass). The car has aftermarket speakers in there now from the previous owner (JBL up front and I haven't checked out back yet), but no extra amplification. From a previous car of mine I have a 12" sub and amp, as well as a 2x125w at 4 ohms 2ch amp (Zapco i2100).

So, I am looking to incorporate the subwoofer (easy) and my 2ch amp to provide a little more power to the car's audio system. Here is where I run into my questions, as well as a few proposed solutions.

Idea #1: Run the front and back speakers (both 4 ohm load, but different size, shape, and performance) in parallel so that I have to channels for the amp at 2 ohms. The problems with this are: low impedance slightly degrades audio quality, lower impedance creates higher wattage (~200w at 2 ohms) per channel (each speaker is realistically only designed for 35-50 watts). My understanding is that it is acceptable to run an amp that is more powerful than your speakers are designed for as long as you keep the gain way down, and this can help reduce the load and heat at the amp, but you are also wasting potential.

Idea #2: Run the front and back speakers in series so that each channel presents an 8 ohm load to the amp. The amp specs don't specify the wattage it would provide at 8 ohms, but we can guess it would be on the order of 50-60 watts per channel. This would be 25-30 watts per speaker, so within their design specs, but also not much more than a typical head unit would provide (20-22 watts into 4 channels). Even if the wattage per speaker would be essentially the same as with a head unit I would guess that the sound quality would be a bit improved, but again it's hard to say (and might be harder to hear in a 25 year old car at highway speeds). I have heard that this can present some problems for the amp as each speaker will change its impedance with the load/frequency, but I must admit I don't fully understand just how much of an issue this might be.

Both of these plans have a common drawback, which is the inability to fade front-to-rear. If the front speakers are a lot more (or less) efficient than the the rears there would be a volume difference and no easy way to correct it. I know I could use an L-Pad to attenuate the louder of the two channels, but that got me thinking of a third solution.

Since there are not a lot of 4" or 4x10" speakers available commercially (and most of what's available is coaxial rather than component), and I know that at least in home audio there is often room to create a better value speaker when using off-the-shelf drivers (from Parts-Express of Madisound for instance), what about creating a component system for the car?

Idea #3: Buy a 4" driver and a tweeter (there is an unused factory location a tweeter could be added to easily) for the front, and a 4" driver for the rear. This could be set-up with a 2-way crossover I think, with 2 x 4 ohm woofers in series and an 8 ohm tweeter. As I understand it this would present a 4 ohm load to the amp, and provide 125 watts per channel which seems pretty reasonable over three speakers.

Idea #4: Use a 3-way crossover with a 4" woofer, a 4" mid and a tweeter. This idea seems like it might work well, and would give the option to better tailor the sound in the car, but would create the most complex crossover and creates more chances for mistakes! If 3-way, the tweeters would go in the dash. But where would the mid driver go, and where would the woofer go? I would think that from an imaging perspective it would be best to have the mid driver in the dash and the woofer in the back with the sub. With that setup all of the bass would be coming from the back, though, and the woofer might get drowned out by the sub (not if I set my levels right). Would it make more sense to have the woofer in the front to help provide some bass closer to the driver and have the mid in the back to help round out the sound? Or would the mids then be drowned out by the sub?

So, if you've made it through such a long post I want to start by thanking you, and then continue right along (for those of you with the longer attention spans).

Which of these seems like the best option?

#1 and #2 would be cheapest, and that is a big consideration for me. I just don't want to create a terrible situation by using a powerful amp with mis-matched speakers. I know the easy answer is to buy a 4ch amp, but I think that would be even more expensive (to get a nice amp) than my component speaker idea.

With the component speakers, is there any value to a 3-way setup over a 2-way setup in a less-than-ideal place like a car, especially when there is a sub to help with the low end? And if 3-way is the way to go, how would you arrange the mids/woofer?

Thanks for any help, and please let me know if any of my assumptions were grossly off the mark.
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Old 25th July 2012, 11:58 PM   #2
freax is offline freax  Australia
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dunno about you but I've gone the 2nd hand route and gotten myself a couple of these: Alpine 3553 Classic Audiophile 4/3/2 Channel Bridgeable Power Amplifier amp | eBay

my one came out of my 1995 fairmont ghia EF

what you are saying about hooking up say a 125 watt per channel amplifier to a 50 watt speaker is true and I love the idea, so you are going in the right direction there, just keep the gain below 1/2 way so that even in the high peaks of the audio material, you won't be pushing out more than the rated maximums of your speakers, but its up to you in the end, you've gotta gauge where its gonna clip or not.

also before I forget, have you thought about sound deadening material yet? I'm thinking about putting it all inside my doors and underneath the floor and all that in my car. but just like you I am also very very poor lol, and i'm gonna have to buy some stuff a box at a time off ebay somewhere.

btw I loved the SAAB 900 design when they first came out, I was only a little kid, and thats exactly why I loved it so much , my family was a huge Audi fan tho, they had friends who worked in the Audi factory in germany...

Last edited by freax; 26th July 2012 at 12:14 AM.
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Old 26th July 2012, 12:38 AM   #3
freax is offline freax  Australia
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I've thought about putting a HUGE horn and driver underneath my front seats, facing foward, or mounting them somehow underneath the front dash area, but I have no idea where to start, I did find this video however which details a car with a horn driver installation: Old School Orion HCCA Subs w/ Image Dynamics Horns - EXO Dr. Stereo Arc / SQ Car Audio Shop Tour - YouTube
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Old 26th July 2012, 03:21 AM   #4
freax is offline freax  Australia
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With reguards to the 3-way idea...If I were forced to make a descision right now on where to put my midranges, I would put them underneath the front dash, down where the pedals are, facing downwards, so that entire area gets a nice fill of midrange material, to carry only 1kHz-3.5KHz.

I don't really like the idea of having midrange fill up on the front windscreen, it doesn't sit well with me personally.

I am however going with a 2-way setup for now, seeing how that sounds, and if the side 5.25" drivers aren't up to the task of creating a nice midrange soundstage I might do exactly as I described, put a couple of midrange's in underneath my dash for the fill in of material between 1kHz-3.5KHz.

Then the front tweeters would carry 3.5kHz and up, and the door speakers would do 1KHz and down.

But my reason for this is this, I used to have a Ford Falcon XF that they used to make here in Australia, and that had very nice sounding 4 inch paper cone midranges in underneath the front dash, with a long tube that connected to the back of them, to create a sort of baffle/port thingamajig going with it, and that sounded nice when it came to midrange.

Also, my thinking goes like this, if you have the midrange in underneath the dash, facing towards you (if you can manage that somehow), and the tweeter on the front dash, and the bass/midbass driver in the door, then you've got a nice triangle setup, where every speaker is at roughly equal distance from each other and the same distance from your ears.

My feeling that with 3-way setups you get more loudness/sound output from each band of frequencies than you would with just 1 or 2 drivers, so you have a dedicated driver for the midrange, which its sole purpose is to generate midrange frequencies, so it can ignore all of the other frequencies, both high and low, and when you think about it, a midrange driver cone cannot reproduce low frequency rumble, or high frequencies, while at the same time trying to reproduce clean vocals without any distortion.

The main reason why I would go with a 3-way setup vs a 2-way would be to get a louder sound while remaining a high quality sound as possible, having a dedicated channel for each driver is just icing on the cake and would allow you to increase or decrease the gain on each individual channel and as a result you will get a louder and cleaner sound with lower distortion from having a dedicated amp channel drive a mid-bass/midrange/tweeter driver individually.

So have a set of 5.25" door speakers or 4" woofers in your dash run frequencies from 100Hz to 1KHz
Then have a set of 4" midranges in your dash run frequencies from 1KHz-3.5KHz
Then have your tweeters on your dash take over at 3.5KHz and up.

And having a second dedicated 4 channel amplifier for the midranges and tweeters should allow you to put in a highpass capacitor circuit which will give you exactly what you want.

But as I've illustrated up above, a second amplifier doesn't need to be expensive, I got my Alpine 3553 for free out of my car, amps are cheap especially amps that come from a friend for cheap, its everything else that is expensive.

This is very similar to what I am trying to do with my car audo setup in another thread, but I've already decided that I'm going to be using 5.25" focal's in my front doors, and the doors will be very sound deadened so they don't rattle.

Last edited by freax; 26th July 2012 at 03:50 AM.
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Old 26th July 2012, 06:06 AM   #5
freax is offline freax  Australia
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failing that, notice how this guy has a midrange driver on the floor down where the pedals are? pointing towards his head: SQ S500 - YouTube

thats another option that you could have too, especially if you have an automatic instead of a manual (no clutch pedal).

that to me sounds like a good idea if you are strapped for space.

what you can also do is mount your tweeters up on the window pillars, up near where your head is, that then will give you room to mount a set of midrange and woofers in your front dash? maybe...

Last edited by freax; 26th July 2012 at 06:08 AM.
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Old 26th July 2012, 02:52 PM   #6
focal1 is offline focal1  United States
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Okay, well thanks for all of the advice, though it sounds like I might be aiming for something slightly different from what you are thinking of. Because the car already has nice openings for a 4" driver in the dash (which is pretty ideal place to have it from an audio perspective) I don't want to put speakers in the doors, or under the dash, or in the pillars. I would like to use factory locations to make the work significantly easier and to make it less apparent that there is an aftermarket stereo worth stealing (which has happened to me before.

I am mostly concerned with whether there are major problems to be had from wiring the speakers up in series, and if I decided to buy separate component drivers whether it would be worth going 3-way over 2-way. The amplifier that I have right now is nice enough that anything I would feel like spending money on would be lower quality, so that is why I am trying to see about upgrading the speakers rather than buying a cheaper amp to use with the cheap speakers.
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Old 26th July 2012, 06:07 PM   #7
freax is offline freax  Australia
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you might want to try asking the series/parallel question in this forum, I can't get any response from the car audio forum on the best of days.

also have you considered getting an expensive 4 inch full range speaker? for those all important dash positions...
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