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Ok, here's a link to the article I was talking about that discusses the Dolby Pro Logic system in the C70.
http://www.imicom.or.jp/kcc/volvo/showroom/c70/c70_audio.html
Unfortunately, the pictures are unrecognizable when you zoom in; I need to find blow-ups of those diagrams to see what goes where in order to determine where best to tap in for a sub or two.
It seems that exploration of this issue is producing more questions than answers... especially since the convertible has a different speaker setup than the coupe. Does that mean that the Dolby knows the difference as far as crossovers and signals and such goes? That link to the swedespeed thread was good too... it may explain some of those differences. Perhaps somewhere in there we can extract a dedicated LFE channel to get a good signal to a single 12" sub or something.
-Jon
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CPT Jonathan T. Belmont-- '99 C70R 48K 'Valdemar'
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John,
I took advantage of yesterday's snow day in the northeast here and installed a sub into my C70. I'm so much happier with the system now. Here's what I did.
I installed a second amp, wired for 1 X 300, mono to a 10" subwoofer. To wire this in, I spliced the rear speaker wires, under the rear deck, before they reach the white connectors. I connected those "spliced sections" with solder and ran speaker wire from there to a line ouput converter to step the powered output from the stock Alpine down to preamp levels. This converter also acts as an adapter from speaker level inputs to RCA outputs so it plugged nicely into my amp.
I also intalled a capacitor in hopes that it would eliminate headlight dimming (more on that later). It also provides enough power to my aftermarket amp, when it needs it to generate those power sucking, low signals. I installed the capacitor so that it's wired to the battery and ground, and the aftermarket amp is wired to it directly.
The remote power on wire, I ran from the Yellow and Violet ACC wire in the back of the stereo. I cut a section of the insulation of that wire (so I didn't have to sever it) and connected the remote power on wire to the exposed wire and wrapped some electrical wire around the connection to secure it.
I snaked this wire along the driver's side, under the kick panel and under the plastic panels along the footboard. Also I ran the power cable to the rear in the same way, but to the front - through the existing tube in the fire wall, to the engine compartment. I removed the bottom rear seat cushion to send the wires to the back and hide them along the rear seatbelt holder.
So when all was said and done, I flipped on the switch and WOW! The system suddenly turns into an animal! I had to adjust the gain on the line output converter and on the amp to tone down the bass. After that, everything sounds so smooth and even. Pro Logic works just fine as well as the center channel. I'm so much happier with the system now. However, there's a problem. I went for a ride last night to test out the new sounds without disturbing my neighbors and my headlights still dim when the bass punches. I looked this up on Crutchfield's tech support page and they recommend upgrading the altenator. UGH! How much will this cost now?!?!? I don't have much a budget cuz I'm buying new wheels and tires. Catch is, if I don't upgrade the alternator, it is likely to burn out within a year.
So all in all, it was a lot easier than I thought. The sound is worth it. I put in a 10" sealed sub and that is more than enough - I wouldn't want to add any more. I got free CPR on my way to work today! But the headlight dimming issue bothers me. So if you can handle replacing hundreds of LEDs, this should take you just a few hours.
Steve
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I took a look back in the trunk area yesterday while installing a backup alarm ($25 on eBay, less than 2 hours to do a very clean install, I'm pretty happy with it) and the amp looks just like alpine's 4 X 100W V12 amp. I'm not sure dimensions-wise whether the five channel amp will fit in the same spot, but I've pretty well decided that when I add a sub to this car, that's how I'm going to do it. All I'll have to do is find a DIN to RCA adapter or figure out which pins go to what. All the speaker connections and power wires and such are already there (although I don't think the power & ground wires are 8 gauge as is recommended by Alpine for the 5 channel, and I'll probably install a .5 or 1 farad cap as well) so the only thing that DIN connector out of the back of the radio could be is all the line level outputs. I double checked this against the wiring diagram, and that all jives. Looks like that'll be the first project when I get back from overseas!
-Jon
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CPT Jonathan T. Belmont-- '99 C70R 48K 'Valdemar'
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Good luck over there...and thank you!
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posted by
someone claiming to be Frank
on
Thu Feb 20 00:40 CST 2003 [ RELATED]
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"Catch is, if I don't upgrade the alternator, it is likely to burn out within a year"
Simply not true. The capacitor should help with dimming lights but with or w/o it, your alternator will be fine. On my '86 745T, I use to have a large cap but something happened to it yrs ago and it apparently shorted (or ?) as it began causing fuses to blow (no probs with it disconnected) so it's been disconnected for about 3 yrs now (havent replaced it yet). My car has a 100W amp from a newer '92 740 and I now have 2 amps, one for 4 speakers, one for the sub only and both total around 850W. My lights will dim at high volumes, volt guage goes down but the alternator's doing fine. I had another car with similar amp draw for many years, also had a 100W alternator and never had alternator probs.
Now, if you're always driving with high volumes, lights on often (like in winter) with blower motor on high and/or AC used often in summer, the battery doesn't get charged as well as it would be normally but that's it, usualy not a big deal. My 4 yr old battery doesn't always crank as fast as it should but it always starts the car. The lights dim a bit but only the guy in front of me is likely to notice so I don't care.
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Thanks Frank! That's great news. I also adjusted the gain on my line output converter (again), as the sub was too bassy. Sounds just right now and the dimming has subsided a little.
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Just to make sure I understand you correctly... now your two rear speakers produce exactly the same signal, they do so at full range, plus your 10" sub also produces the low frequencies that the rears receive. That's good news that the pro logic still sounds good, it's certainly a simple solution.
I think that if the car is currently powered by a four channel amp, I'm going to look into replacing that stock amp with a five channel amp as described in my previous post. That way no external crossovers, bass blockers, line out converters, etc are needed. Alpine makes the stock four channel amp as part of their V12 series, although I'm not sure which model number it is. They also have a 5 channel V12 that is my most likely candidate right now.
-Jon
--
CPT Jonathan T. Belmont-- '99 C70R 48K 'Valdemar'
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posted by
someone claiming to be Frank
on
Tue Feb 18 16:26 CST 2003 [ RELATED]
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Maybe you're thinking this is more complicated than it needs to be? I only use ONE large 15" mono sub in each of my two cars. I'm now powering it with a 450W amp in my Volvo wagon which is more than enough. With an aftermarket sub amp, it doesn't really matter where you decide to tap into your speaker wiring but I'd just tap into the two closest to the trunk (or amp location, easiest way). A mono sub amp takes both L and R inputs and combines the output to one single speaker output. One good powered sub is more than enough IMO, one doesn't really need 2 subs but many people do that too. The surround sound, etc doesn't matter at all when adding a sub amp. Don't compare anything aftermarket to how Volvo does it in the C70 convertable as it won't matter if going aftermarket.
Rather than keep asking people here, why not discuss it with people at stereo install places to get their opinions? It'll all end up depending on how much bass you want and how much money you want to spend.
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Frank-
I understand what you're saying, and that does solve things, sort of...
There is a difference between a regular two channel stereo setup (left and right channels, or L & R) and the surround setup in the C70 as I understand it (left, right, center, and surround, or L, R, C, & S). The center channel can be ignored as it doesn't receive signal below 100hz and is driven off of a 25w amp internal to the head unit. However, the surround speakers in the rear of the car may receive different information, essentially acting as a left rear and right rear... this leaves us with LF, RF, LR, and RR as our four distinct bass-producing surround channels. This is the only part I wasn't able to verify from dolby and Volvo... those rear speakers MAY be receiving the same information. Still, with a combination of balance and fader controls, it is conceivable that they could be receiving different levels.
Those four speakers in the C70 coupe that reproduce low frequency sound in the 120hz and below range are the two 8" woofers in the front doors, and the two 8" woofers on the rear hat shelf. IF your intent is to have each speaker only receiving the frequencies it is intended to reproduce, then you end up with crossovers and bass blockers and such directing your high freqs to tweeters, your mid range stuff to your mids, etc etc etc. To separate the low frequency into two ranges, woofer (8") and sub-woofer (12-15"), you would probably do something like send the same signal to your woofers and subwoofers, but use bass blockers or an amps internal crossover to keep the right frequencies going to the right speakers. That way, there isn't some sound that doesn't get reproduced at all. Only issue you might have with that is if you ran your rear speakers' signal to your subwoofer, then used your fader to play only out of the front speakers, then you wouldn't hear anything at all out of your subwoofer, and your fronts would be reproducing the whole spectrum. However, usually your fader will be set normal, and you'd be ok. Option two for a regular ol' two channel (L & R) stereo would be something like a five channel amp... I had this setup in my '85 740, my first volvo. The head unit had left and right, front and rear line level outputs. These went into the five channel amp where the low freqs were shaved off and sent to a fifth channel for the subwoofer. Then the four other channels were for the left and right, front and rear. With that setup, no matter what you did with your fader, ANY low freq signals that were going to ANY of your speakers would end up making it to the subwoofer.
That would be a more ideal solution for the surround sound setup, because unlike stereo, you may be getting different musical info sent to your front speakers than what is sent to your rear speakers. SO, in order to accurately have your subs reproducing any and all low frequency music, you'd need to have either a five channel amp like what was described above, or you'd need a FOUR channel mono amp like the one you described (do they make those?) that would combine four distinct inputs (LF, RF, LR, RR) into one output, or you'd need two 2 channel mono amps like the one you use, and have one sub for the front (combining LF and RF) and one for the rear (combining LR and RR), OR one sub for the left (combining LF and LR) and one for the right (combining RF and RR). Any way you went, ANY low frequency bass that went to ANY of your four main speakers would get shaved off and sent to a subwoofer.
In summary- I believe that all four channels of the C70's audio system should be trimmed of their low frequency bass and have that signal sent to a subwoofer. This could be accomplished by a five channel amp designed to shave that signal off and never send it to the main speakers in the first place, OR by a set of crossovers, line level input converters, and mono amps to shave the signal off AFTER it has already left the original amp but before it reaches the speakers.
I'm pretty sure alpine made the amp for volvo, a V12 4X100 watt model. I think I'm going to look into whether or not they have a five channel version...
-Jon
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CPT Jonathan T. Belmont-- '99 C70R 48K 'Valdemar'
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posted by
someone claiming to be Frank
on
Wed Feb 19 00:59 CST 2003 [ RELATED]
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You ARE making this far more complicated than need be. A good aftermarket amp has built in, adjustable crossovers so all it needs is basic 2 wire stereo inputs (your rear speakers) and the amp does the rest, no need for more crossovers, etc. All you need is one good amp, one or two subs, a little wiring and that's it. It's easy. Don't even consider the center surround speaker as being any part of your equation nor do you need a 5 channel amp if only to be used for adding subs. Most good aftermarket amps are made to be used for either amplifying several door speakers (4 channel) or can easily be bridged for one or two subs and have selectable crossovers. Each amp comes with detailed instructions that'll explain how to do that either way.
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You're right about an amp having speaker level inputs and crossovers, but then your 8"s are still getting muddied by having to use energy to reproduce the low frequencies that the subwoofers are taking care of. Also, if you only tap off of the rear speakers, then the front 8"s are still left to reproduce full range sound and any low frequencies they receive (but the rears don't, because they're surround speakers) will not be reproduced by the subwoofers.
-Jon
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CPT Jonathan T. Belmont-- '99 C70R 46K 'Valdemar'
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