Hi,

Just got done building my 1-10" sub box. Now I have a question concerning amplification... I have an older Alpine 4/3/2 power amp. For 2-channel operation (2x70w), it has two cables... one for ch 1/2 and one for ch 3/4. Each have + and - connections.

Is there a way to bridge these two cables and create a 1x140w mono output? If so, how?

I don't know, maybe I'm asking for trouble but it'll save me the cost of a new amp

Thanks,
Jon

 

Nope.

It is a VERY rare feet to find a 4 chan amp that can be bridged down to 1 chan. Sorry.

 

Yeah, I've never seen a 4 bridgeable to one, unless it has a switch and/or a seperate set of connectors it's basically imposible. You might want to use 2 channels for mids/higs/full range and one channel for the sub. I wouldn't advise running just a sub off one channel and nothing off the other. Most amps tell you not to load just one side, can't explain the technical side of that though.

 

Thanks Deus and Viper...

Yeah, I can throw 70w at the 10" sub and 2x25w at the rears or fronts. Not enough power IMO... especially for the sub. I guess I'll be looking for either a 2-channel bridgeable sub amp or a 5-channel model (if that's available?). I had planned on running the main speakers with an Alpine 4x40 head unit. I've got some Polk DX7s that sound pretty good with the Ford SC stock unit so I was banking on them sounding even better with the Alpine.

Cost is a concern unfortunately ..

Thanks again,
Jon

 

Jon, If you don't have your sub amp yet, DON'T bother with bridging a 2 channel amp. You limit yourself when you do that. Buy a mono sub amp that is capable of 2 or even 1 ohm loads. Especially if you have a 4 channel that you want to use for your main speakers. If you already had a 2 channel amp laying around and wanted to use it, that would be another matter. But if you are still looking to buy, get a mono amp that is designed for sub use. You will be glad you did.

 

Thanks 97f250

I can understand that to a point.... however my cabinet is only built for one 10" 4-ohm sub (a Polk GNX10), and honestly that'll be enough "punch" for me. Is there something that mono amps have that a bridgeable 2-channel design doesn't, other than versatility?

I do have an older Alpine amp but it only puts out 4x25w into 4-ohms. That's less than my Alpine head unit. I wish I could find a 5-channel amp that maybe delivered 120w to the sub and 50w or so to the mains. Still researching

Thanks for the advice,
Jon

 

Most head units only actually put out 10-12 watts a quality amp will put out real numbers.

 

Thanks RoadRacer...

So my Alpine 4x25w@4-ohms amp's output will be "continuous" power as opposed to "peak" power? I was under the impression that a 4x40w head unit put out closer to 20w "continuous"... and therefore, not a major difference between my 10-year-old amp and my newer model CD head unit

Jon

 

Crewd, I misread your post about using your HU's amp for your main speakers. I would never recommend someone to use a HU to power speakers if they are using a subwoofer. It is commonly done, but the balance of the system suffers because the sub tends to overpower the rest of the sound spectrum produced by your main speakers. You CAN balance everything, but at the cost of cutting back your sub's output substantially. Maybe not so much using just one 10". I can't guarantee, but if your old amp doesn't have anything wrong with it, it will almost surely be better than the HU. Especially if you have a mild sub and you're giving it about 120 watts. The problem with HU amps is that the power supply is limited by how much juice your battery can supply, so they suffer greatly when one "cranks it up", especially when using AC, lights, etc. A separate amp has a different type of power supply that is more suited for "maintaining" a certain voltage level under conditions that a HU can't. So a 25x4 HU is in no way the same as a 25x4 dedicated amplifier of any quality at all. If you are going to use one 4 ohm single voice coil sub, you can definitely use a nice bridged 2 channel amp. But if you buy a mono sub amp, future upgrade flexibility would be there. On the subject of 5 channel amps, I currently am using a Hifonics Zeus Z8000 in one vehicle. It's 50x4 and 200x1. It is a very nice mid-quality amp. Very nice looking with lots of features. I bought it brand new, not refurbed, on ebay for less than $200, shipped. No warranty, but no problems as of yet. I have had Hifonics before and had great luck, so I took a chance. So far, so good.

 

Crewd,

I am assuming from the power ratings you give there that the amp your talking about could very well be the older Alpine 3527 (i used to have one) that had those same ratings. Anyway long story short that amp was at the time slightly under-rated as were many of that era of high-end amps (you know, when in Rome). Anyway, that amp will do just fine for the setup your talking about. Back in my younger years when i ran an amp like that I had half on my front components and the second half driving 2- 12's and although it wasn't the loudest on the block it did quite nicely.

 

Thanks 97f250...

Yeah I agree with you about running a head unit by itself. It's easy to think you're happy with that setup, but a quality power amp can really make good speakers sound great. Right now I can get an Alpine MRV-F450 5-channel amp (4x50w + 1x200w) for about $300.00 on eBay. Otherwise I'd have to buy either a mono or 2-channel bridgeable amp just to power the sub. I think I should just go for it and buy the Alpine 5-channel!

 

cgorris,

You've got a good memory. Actually it's a Alpine 3550 4/3/2 amp. It did sound very powerful in the early 90s. I used it in a 3-channel configuration and those 70w going to my Alpine 12" sub kicked my butt! However, I'll probably end up putting it in my wife's vehicle since I'm adding a sub to mine and need to power 4 speakers w/fade controllability. Besides, she's not as car stereo conscious as I am.

 

Well that definitely would make a good amp for her car. Probably provide all she needs and then some. Another thought you could look into would be to use the 3550 for mids and highs and add on a seperate mono block for the sub. I can tell you now that amp would keep up with 300-400 watts on a sub with no problem. True output on that amp was actually in the neighborhood or 45-50 watts RMS per channel @ 4 ohm. Everyone under-rated at that time. Now it seems unless you buy competition quality amps they are all over-rated. If I remember correctly the 3550 retailed for about $250.

 

"Another thought you could look into would be to use the 3550 for mids and highs and add on a seperate mono block for the sub"

Yeah I was thinking about that too. Unfortunately my CD receiver has only one RCA preamp out and I'd lose the ability to fade front to back. I'm going to install the head unit (4x40w) tomorrow and see how it sounds using the onboard power. I can cut all frequencies below 60, 80, 100, or 200Hz so maybe I'll get an idea how it'll sound prior to adding the sub

It seems like my only other option is to buy another head unit with more RCA outs to take advantage of the 3550

 

Crewd,

Before I would bother changing out the HU I would look at adding in a preamp/EQ. It will give you the fade control, and sub level control that you want and also add in more overall sound control. If you get the half din size it will fit right in the dash and look good as well.