I'll admit that I don't have too much knowledge when it comes to car audio installs. I have my empeg installed, and I'm surprised that it works so good.

My problem is this, The front and rear 6.5" speakers are getting a full range of sound when I only want them to get tremble. And when I install my 10" sub I only want it to get bass. Right now I have to use the empeg's EQ to only send out high notes to the amp, otherwise the 6.5" speakers sound bad.

I am pretty sure that my amp doesn't have a crossover built-in, I'm not sure what differences there would be though. It is a 4 channel amp with gain control knobs on it. And I expect that people who want big bass would add another amp dedicated to the subs, but I'm running out of space(and don't really care to have my car shake).

What kind of crossover should I get. Does it matter if it is an active or passive one? Would simple capacitors and inductors work? And where should I put this?(oh wait, I figure that out. I don't really need that air bag sensor, do I?)

Thanks

An active crossover goes on the low level lines (RCAs), between the head unit (empeg) and the amplifier, it also has active components inside that need a power feed (not very much current though). The passive crossover goes on the speaker wires between amp and speaker and consists only of passive components (coils, caps and resistors)

The very simplest thing would be to put a cap in series on the speaker wires to the normal speakers (aka "Bass blocker"). That'll provide you with the least possible filter slope (6 dB per octave) - higher slope is normally considered "better" - ie if the filter frequency is specified at say 200 Hz, you will still have signals lower than that pass, but the 100 Hz signal (one octave lower than 200 Hz) will be attenuated with 6 dB, the 50 Hz signals attenuated 12dB etc.

To prevent the sub from playing higher than wanted frequencies you can add a coil in series on the speaker wire - this'll provide a 6dB low pass filter.

It is easier to build active filters with higher slopes than passive ones.

How are you planning to power your sub? Connecting it to your existing amplifier in "tri-mode"? (ie bridged over the rear channels while keeping the current rear speakers also) In that case you need passive filter components in order not to bring the Ohm load down too low on the rear channels. (Also, if you were to filter already on the RCA signal, you would not have any high frequency content remaining to be amplified and sent to the rear speakers.)

Here are some links to more reading:
Crossover slope
Electronic/Active crossover
Capacitor & Speaker
Inductor & Speaker
Passive crossovers
TriMode speaker connection
TriMode power

The entire site is very good for understanding basic car [audio] electrics.



/Michael

I am pretty sure that my amp doesn't have a crossover built-in, I'm not sure what differences there would be though. It is a 4 channel amp with gain control knobs on it.

If the only controls it has are gain control knobs, then you are correct, it does not have a crossover built in. There would be other controls for crossover, such as high or low pass switches, and perhaps even a knob to set the crossover point.

What kind of crossover should I get.

Actually, you can do a poor-man's crossver by using something like F-mods. Very inexpensive, and they work. I've used them myself from back in the day before I had an amp with built-in crossovers.

But if you've got the money, I'd just dump the amp and buy a proper one that's got crossovers built-in. That gives you the best control, and also is the least likely to induce a ground loop noise problem. Since you're planning on adding a subwoofer anyway, now is the time to just replace the 4-channel amp with a 5-channel amp that's got crossovers built in. That's your best bet.

Thanks for all of the information. It looks like I will be busy this weekend with this project.

The thing about buying a new amp, while it sounds good, I've never heard of 5 channel amps. And second, if I had enough money to buy another amp, I could probably hire an expert who isn't guessing at what he hopes will work and not blow up his cars' electrical system. This kind of happened once before I took over ownership from my Dad, a wire shorted out in the turn signal lever and caused $400 worth of repair bills. So, I have to become an expert on something I should be good at, but don't have much experience in doing it, and hoping my car won't turn into a paper weight.

I am planing on hooking up one 10" sub to channel three, and one 10" sub to channel four on my amp. I currently only use the first 2 channels, channel 1 is the front pair, channel 2 is the back pair. It is warnings like "don't bring the Ohm load too low" that concern me. Basically because I'm not really sure what my Ohm load is at right now.

And I haven't made up my mind yet on doing the capacitors/inductors thing or crossover. I'm going to have to look at how my system is setup again and if I can fit it in someplace.

For the crossover, could I plug the empeg out (to amp) RCA wires into it, or is it better to have it close to the amp? I'm guessing it doesn't matter...

Sorry 'bout not responding earlier, but my internet connection has been down for the last two days... the shaking has just about stopped

I am planing on hooking up one 10" sub to channel three, and one 10" sub to channel four on my amp. I currently only use the first 2 channels, channel 1 is the front pair, channel 2 is the back pair. It is warnings like "don't bring the Ohm load too low" that concern me. Basically because I'm not really sure what my Ohm load is at right now.

Shouldn't be a problem then. Most likely your amp can handle a load down to 2 Ohm per channel. You need to check your 10" subs as to what impedance (ohm) they are per coils and if they're single or dual voice coil subs.

If they're single voice coils there shouldn't be any trouble at all - haven't heard about any 1 Ohm SVC subs...

If they're DVC, then you need to decide if you want to connect the 2 coils in series (doubles the impedance, compared to the impedance of a single coil) or in parallell (halves the impedance).

If you post exactly which subs and/or what configuration they are, I'll be happy to show how to wire them up. Also the same for the amp, so we can be sure of what it can/can't do...

Now, will the subs be in a common airspace box? Or are they separated by a divider?
This'll also affect how to best wire the subs.

In general, if possible - considering their config and the amps capabilities - I would join the 2 subs together (electrically) and connect them to channel 3 & 4 in bridged mode. That way they will see, and play, the exact same signal.

The Ohm load stuff gets simplified alot when you're not doing things like tri-mode...

As to filters, I'd either get fmods /that Tony linked above) or a cheap simple 2 channel crossover - something like this. This one is a bit better.

/Michael

Sorry 'bout not responding earlier, but my internet connection has been down for the last two days... the shaking has just about stopped

ROFL
I know what you mean!

It is getting scary how much I know about subwoofers and crossovers now. Well, I'm sure there is more to know, but I can design and build boxes now.

The subs have a 4 Ohm impedance, and each have their own box. Well, one has a box right now, the other one will have to wait a little while until I make it. So, I think I pretty much have to wire it directly to each channel. And there is ~.85 cu ft. in each box when the recommended is 1.0, but I did put polyfill inside to make the box appear larger to the driver.

But, what benefits would I get if I wired them up together in a bridged setup? I have heard good subs before and I have heard bad ones, but I’m not sure on the details of them. I did get the chance to test one of my friends’ 10” subs in my car and it was a little louder, but it didn’t produce a lot of bass. I am guessing this is due to 2 problems, one was the box it was in was way too small. The box was designed to fit in a pick-up truck cab. And the second may be because I am sending the full range of audio to it. I am considering using inductors for now, is there really anything bad with just using these? In the WinISD program there are circuit diagrams to build active-passovers that a computer engineer like myself could build. The only disadvantage I can see is that they aren’t adjustable and the crossover rolloff is only 6db/octave. But by adding 2 capacitors I could get that up to 12db/octave it seems. And the active ones would be around there or better, I’d assume.

Now I just need to order some carpeting from Crutchfield to complete it, but I’m sure I’ll test it before then.

Thanks for the help.

The subs have a 4 Ohm impedance

But SVC or DVC?

If DVC you can get a final single ohm load of 4 ohm, by wiring them in series/parallell to the bridged amp. This will give you the max power the amp is capable of (each sub will get the same power as the amp delivers on a single channel into a 2 ohm load)

If they're SVC, you´ll have to wire them in series, for a 8 ohm load bridged. You´ll get the same power as if you wired each sub to its own channel (ie what the amp produces per channel into 4 ohm)

The benefit of bridging is that both subs play the exact same signal, not one playing the left signal and the other the right signal. (nowadays probably not that much of a problem as the bass typically is present in both channels, but on older recordings that may not be the case)

Common active filters typically have 12/18/24 dB/octave.

No real problems with simple cap/inductor filters - for killing bass to front speakers they´re commercially sold as "bass blockers"

/Michael

I saw those Bass Blockers, but at $10 for two capacitors they were a little much. I was able to by 4 capacitors for $7 at the electronics store. I will probably put them in today, but my speakers were working good earlier. I found the inductors on-line for $1.31 each.

I looked up some info on DVC subs, but since my sub doesn't say anywhere, I would say they are single. But, I guess what I don't understand is what does having a 2 Ohm load change things? Will the 200 Watts per channel be used more effieceintly? If I bridge them will there be 400 Watts going through each sub? I could see doing it then, but I'm not sure if it is possible since the instructions didn't say anything about wiring.

I was able to by 4 capacitors for $7 at the electronics store.

Bipolar caps I hope, considering that we´ve got an AC signal.

I looked up some info on DVC subs, but since my sub doesn't say anywhere, I would say they are single.

If you only have one set of wire terminals on the back of the sub, you´ve got SVC subs. If there are 2 sets of terminals you probably have DVC subs.

But, I guess what I don't understand is what does having a 2 Ohm load change things?

The ohm load on a channel determines (together with the amps construction) how much power the amp makes - according to the formula P=U^2/R, where U is voltage related to the amps internal powersupply (the amp boosts up the 12-14V the amp is fed in order to be able to make more power) and R is the impedance of the load (sub).

If the amp does 100W per channel into a 4 Ohm load, it´ll (if it´s a decent design) do 200W into 2 Ohm - if it is capable of handling a 1 Ohm load without going up in smoke it´ll nake 400W into a 1 Ohm load... Most multichannel amp can handle a 2 Ohm load per channel, but not lower.

When you combine 2 channels into 1 by bridging the channels, the lowest possible load doubles, ie typically a 4 Ohm minimum load.

A 2 channel amps makes the same total power into two 2 Ohm loads as into 1 (bridged) 4 Ohm load, ie 2x200W @2 Ohm and 1x400W @4 Ohm

Will the 200 Watts per channel be used more effieceintly? If I bridge them will there be 400 Watts going through each sub?

The combined load of the (serially wired) subs would split the total power the amp makes between them.

If you have 2 SVC 4 Ohm subs and the amp is stable down to 2 Ohm per channel, you simply can´t use the full capacity of the amp, whether in 2 channel mode or bridged - you´re limited to the power per channel @4 Ohm.

HTH,

/Michael

I'd rather not see smoke coming out of anything in my car, that would be bad. I did get the bipolar capacitors, but I am reconsidering the crossover now since the inductors are hard to find. The crossover will allow me to fine tune the sound as well.

Is ebay the best place to buy crossovers, or would going to a local car audio shop be better? And how much of a difference will an active, passive, or no crossover make on my system, basically will spending this money for the best now be worth it, or is it not worth it? I'm pretty sure it will help, I'm just wondering how much.

Thanks for the help.

personally, i wouldnt bother and just get a really good 5 channel amp with crossovers, if you're gonna spend the pney. the HIFONICS ZEUS ZX8000 is a good one. i personally have the older model Z700, but its basically the same. at 2 ohm, the total output is at 700W, and you can choose from 3, 4, or 5 channel.