Amp and Speaker Questions

**unixxx** · 02-23-2006, 11:22 PM

I'm a newb to car audio and have a few questions about my setup before I purchase the amp(s) and speakers.

How many watts per channel should I look for in a mid to high end setup with four full channels, two tweeters, and a sub?

Are the Alpine V12 amps justifiably better than the Alpine V-Power amps?

Should I split up the two front full range speakers into HF and LF as they are in the factory setup?

If I have two full channels in the front do I even need to use tweeters where my factory tweeters used to be?

Thanks.

**3onDubs** · 02-24-2006, 11:43 AM

If you have factory tweeters, than the speaker in the front of your car is not a fullrange...it is a midrange. IT covers all of the middle frequencies, and the tweeter covers all of the high frequencies.

HPF and LPF are filters. HPF filters out all of the sound below the set range (at the amp's specified slope). IF I set my HPF to 80HZ, for example, then all of the sound below that frequency will be faded out to nothing gradually at a rate depending on my amp. Most amps have 12 db slopes....which means that for every frequency interval, the sound drops a 12 db level, until all sound below that point is eventually filtered out.

LPF filters out all of the sound above a set range. You would only use the LPF for subwoofers. HPF is for speakers and tweeters. If you have stock tweeter locations and are going to be upgrading to aftermarket speakers, than you should definitely get a component set. It comes with a tweeter, a midrange, and a crossover. The crossover will do all of the filtering between the midrange and tweeter, but all you have to do is set the HPF at the amp to filter out all low level frequencies (that the sub would need to handle).

I don't know much about the different Alpine amp line-ups, but I do have a 4 channel amp, a component set, and a coaxial set for sale in the classified forum if u were interested.

**unixxx** · 02-24-2006, 01:17 PM

I'm using the PXA-H701 as my DSP. It actually has seperate front tweeter outputs so that they can be independently adjusted (it has a builtin crossoever). I was thinking about using 2 four channel amps in this config:

Amp1:

Channel1: Front Left Mid
Channel2: Front Right Mid
Channel3: Front Left Tweeter
Channel4: Front Right Tweeter

Amp2:

Channel1: Rear Left Full
Channel2: Rear Right Full
Channel3/4: Sub

The amps I'm looking at support the 4/3/2 channel configurations. Would I just feed the mono sub input into both channels 3 and 4 and then wire the sub across both channels? The amp manual isn't very clear on this. Also, would an independant channel on an amp that powers mids be too much power for a tweeter? Thanks.

**3onDubs** · 02-24-2006, 01:47 PM

When you have a crossover connected to a mid and tweeter...it takes the power from the amp and gives the exact same power to the mid and tweeter. If there are 100 watts comming into that crossover, than the mid is getting 100 watts and the tweeter is getting 100 watts.

So...to answer your question about the tweeter getting too much power...no, it should be able to handle the power. I also have the H701 and am using Front 1 for my tweets and Front 2 for my mids. I am running a 4 channel amp for my fronts and a mono amp for my subs. I had a small 2 channel amp hooked up for my rear speakers, but then I realized that i can't even hear them when the fronts are turned up and it wouldn't make a noticeable difference if I just ditched them...so i did.

The amp I'm selling has 4/3/2 operation. There is a switch on the amp that lets you select which mode you want to run it in. There is usually always a switch unless the amp could autodetect the inputs. I wouldn't recommend powering the rears on ur sub amp. You want as much power as possible to go to ur subs. I would just get a small two channel amp for the rears and a bigger amp for the subs.

Check these amps out...they're a matching set. The 180 is a smaller version of the 720, but they look exactly the same and they both have the same sized chrome spider on top: FS: Soundstream Amps & Excelon Speakers

**Will Albers** · 02-24-2006, 02:48 PM

Thats a LOT of wasted power in the 8 channel configuration above. Also keep in mind that adjustability is not always a good thing. Most high end seperates will build speaker deficiencies into their cross over networks. They have gone to great lengths to work out the best sound quality in the crossover. Now you think that you have the ability to make it better?

Let me give you another example... I have a honda with a programmable ECU. I can adjust fuel curves, timing etc. I have COMPLETE control over the who power band!!! Sounds great!? Well sure, if i knew what the hell i was doing. If i had a dyno to play with and loads of time, could tune that bad boy til no tomorrow.

Now do you have the tools needed to create your perfect crossover points? Do you have access to a RTA and the confidence that you are not making the sound worse by messing with the crossover points? If you did, i would guess you wouldnt be asking questions in this forum!

Keep things simple. You need 5 channels of amplification. 2 for the front speakers, 2 for the rear and a sub channel. work that out anyway you need but i highly advise using the passive crosovers. It will draw less current, be cheaper and sound better.

**EricE** · 02-24-2006, 03:17 PM

Originally Posted by Will Albers

... but i highly advise using the passive crosovers. It will draw less current, be cheaper and sound better.

Passive crossovers are less efficient, not more. They send the same power to the tweeters as the mids (assuming they don’t have an attenuator). With an active crossover you can power the speakers AFTER the crossover which allows very fine tuning of the balance between tweeter volume and mids.
As to which sounds better. That is debatable. A well designed passive is better than a poorly setup active crossover. But it is easy to get an active crossover system tuned every bit as good and better sounding than a passive crossover system.

Short answer, don’t ask car audio questions on a computer forum. Go to a car audio forum and ask there. I suggest Elite car audio. Good peeps there.

You paid for an extremely tunable/configurable sound system in the H700/701. Use it.

**Will Albers** · 02-24-2006, 04:46 PM

if he were to use passive crossovers, he will use less channels of amplification and draw less current. The lessened current is obtained via cutting back on amplifiers by using a passive crossover and not the crossover itself.

**unixxx** · 02-24-2006, 05:34 PM

But if I run two speakers off of each front channel I'll also have less power and have to buy a passive crossover.

**EricE** · 02-24-2006, 05:52 PM

If you have 8 channels available and ran this setup like you posted above:

Amp1:
Channel1: Front Left Mid
Channel2: Front Right Mid
Channel3: Front Left Tweeter
Channel4: Front Right Tweeter

Amp2:
Channel1: Rear Left Full
Channel2: Rear Right Full
Channel3/4: Sub

Then you would be set. The mono for the sub would just be used on either right or left (whichever the amp told you to use with mono, usualy it is right). Doing it this way you would not overpower the tweeters because you could/would adjust the amps output on channels 1 & 2 to balance with the output from 3 & 4. Since you have the H701 I would suggest getting the amps to setup the system properly (namely, avoiding passive crossovers and getting 8 channels to do the system above). The H701 is extremely configureable but you will initialy have to spend some time tweeking it to get it all setup right.

BTW, for a sound quality setup most (all?) recommend ditching the rear speakers. It ruins your sound stage and imaging. Tune your system with just the fronts and sub and click on the rears only when you have passengers.