Martingale

Right now I am running Alpine seperates up front and Alpine coaxials in the sail panels powered by a 55x4 Alpine amp. There are three MTX subs in the hatch powered by a Hifonics BX1500D amp. I have both amps set on full range and I'm using the filters in the head unit that go in 20hz intervals. I have the HPF for the speakers set a 120hz and the LPF for the subs set at 80hz. Now I know I'm missing a bit of sound here, but with the LPF at 100hz the subs distort and with the HPF at 100hz or 80hz you can't really hear a difference except sometimes the speakers want to distort at higher volume. Is it okay to leave a gap between the speakers and subs or should I try eliminating the gap and adjusting the audio controls to pull out the higher end of the lows and lower part of the mids to stop the distortion? Any suggestions on base settings to start working with? It seems to sound great, and I'm thinking the sound in the 80-120hz range would be drowned out by the lower bass anyhow. Input? Thanks.

FSUNole17

iTrader: (18)

i seroiusly would look at filling in that gap, as 80-120 HZ can make a difference. try playign with the EQ on the headunit so that u can allow ur components and coaxials to play them. also, try using BOTH crossovers, amp and HU, as this will give u a steeper rolloff for teh crossover point and therefore attentuate the higher or lower frequencies more sharply. for example, if you have a 12db/octave hp filter on ur hu and a 12db/octave filter on the amp, if u use both, the combined effect is a 24db/octave slope. worth a shot!

GPz1100

FS is right.. When you have cascaded filters (one right after another), the filtering result is additive.

Is that amp suffificent for running the 3 subs (12"? 10"?).

These are the specs I pulled for the amp at one site.

1 X 500 Watts RMS into 4 ohms
1 X 1000 Watts RMS into 2 ohms
1 X 1500 Watts RMS into 1 ohm

How do you have your subs hooked up, what's the apparent impedance the amp sees?.

I wonder if your sub distortion is caused by the amp's inability to drive them all. Also, is the distortion from the sub itself, or from some other resonance..

Richiec77

iTrader: (3)

No. No. No.

Adding x-over's will not sum together,It will filter @12db then Filter it again @ 12db. That does not make it a 24dB x-over ciruit. The drop off wil be different. Phasing and time lag will also become a problem, and Extra-Distortion can become present. So they will add, just not the way you would think. Physics.

These are 2 discussions that have covered it. Got Pretty Technical in the Second one.

https://ls1tech.com/forums/wiring-stereo-electronics/320595-x-overs-part-ii.html
The last post of this discussion pretty much hit it on the head.

https://ls1tech.com/forums/showthrea...6&page=1&pp=20

Also, Depending on the Accoustics of a Vehicle, that 80-120 Hz range may or maynot be missed. You say you can't hear the difference. That is probably becuase it is not all that needed.

Also, when you do develope a High and low to merge 2 freq ranges together, Then can have either a Dip or a Peak in the x-over point. Depends on the Type (butterworth or Linkwitz-reily).

Firehawk526

iTrader: (1)

FILTERS = EVIL

They'll get you into real trouble if not careful!

Richiec77

iTrader: (3)

LOL

GPz1100

Richie,

Thanks for the correction and the links provided. Very interesting reading (and surprisingly I still remember what most of it means from the classes I took some years back).

The conclusion I came up with is, by cascading these filters, you are in effect getting what would amount to an additive effect, but you're also affecting other frequencies in unexpected ways..

Richiec77

iTrader: (3)

Yes, plus Time Phasing issues. Will probably/probably not hear the difference in a regular install, but in a Good install you will definitly chase your *** trying to figure out why it sounds the way it does. Learned the hard way before I understood the theory.

FSUNole17

iTrader: (18)

My fault, I was under this impression, sorry for posting bad info. On this same topic, I am using both of my HPF and LPF on my HU and amp and it sounds ok to me, could it sound BETTER if i turn the HU filters off and strictly use the amps?

Martingale

A lot of great info here guys, thanks for the replies. There's so much adjustability with these new head units.

GPz100, I think the amp is able to push the subs. Those specs you listed are correct. I have three 10" MTX "Blue Thunder" subs in a tri box circa 1999. From what I can remember I am pretty sure they are wired for a 4 ohm load and are capable of handling up to 600 watts RMS. The Hifonics amp is rated at 500 watts RMS @ 4ohm. Whether or not it actually makes those numbers is anyone's guess. One thing I did notice about this set up is that the subs hit really hard but they're not that loud or deep. I used to have the same box powered by a briddged MTX 2-channel amp and it was louder and deeper with that amp.

Rich, what would be the difference between a good install and a not so good install? I hear about people blaming a lot of problems on the install before but I'm not sure what can go so wrong. We used Rockford Fosgate wiring through the whole car. 4 gauge power wire to the sub amp, 8 gauge to the 4 channel. RF speaker wire...16 gauge and 12 gauge for the subs. Pretty decent RF RCA cables run on the opposite side of the power wires. We have a good ground and everything. Is there anything I should double check?

GPz1100

Consider this. You got 3 subs capable of 600 watts each rms.

You got an amp thats capable of 500 watts rms into 4 ohms.

Assuming the apparent load to the amp is 4 ohm (although i don't see how that could be.. although 12||12||12 ohms would yield 4 ohms ), that means that each sub is getting ~170 watts at max.

Unless there is something I over looked, I think you're under driving them... If you could run the amp in 2 ohm load, you'd be ok I think.

You don't recall what the impedance of each sub is do you?

Martingale

I'm thinking back a long time here but from what I can remember the whole box is wired for 4 ohm, so I guess it has 12 ohm subs. I could be wrong but that's what I remember. I used to have the same box hooked up to a bridged 2 channel MTX amp and it would clip and stop working all of the time, so the box could be 2 ohm or 1 ohm or something and the little MTX amp wasn't stable that low. The whole box is capable of 600 watts, so 200 watts for each sub. The Hifonics amp should be making enough power I hope unless the amp is overrated big time which could be the case. The whole box was like $300 with the subs so they're not really high end subs, but they're reliable as they've been in 4 cars now and never had a problem so I want to keep using them. Plus the tri box fits like a glove in the hatch of an F-body...almost looks like it's made for it.

Richiec77

iTrader: (3)

Try either/or. Your ears are the best judge.

And that truelly depends on the equipment being used. Sometimes the filtering is better in the Amps, Sometimes the HU. A HU will manipulate a much smaller siganl than the amp would. So if the HU filtering is only so-so, it can add noise that is small, but then becomes amplified to become the actual output from the RCA. The AMP recieves a larger signal and filters it, the noise will be small and stay pretty much small (Only on the Input side).

So, depending on how good the equipment is, it can go either/or.


Glad you asked the question again. I like these discussions becuase it gets rid of falsehoods.

Also, A good install is not just the components that you use, it's they way you install them, plus the set-up of Gains, X-overs, EQ's. A Good to great will employ stuff like, Kickpanel speakers, Midbass along with Midrange (Not just a single 6 1/2 for all that range. Can do it, but has to be a Great driver), Phasing measurements, Knowledge of teh cars accoustics, etc..

Let's relate this to Engines. We're here becuase of that type of stuff mostly.
It's the same in that it's a "Package" and not 1 item that makes the difference.

Basically, an "OK" install is just parts swapping. Figure you have PArts and you install them with no tune. It won't run at it's optimum. Needs to be tweeked to run @ it's best.

A "Good" install will have the parts in place and a decint tune. Figure a Knowledgeable guy or an Ok/Average Mechanic.

A "Great" install would be like having the Engine Blueprinted and built. Lot's of measuring and machining to make it work the best. They would also know what Tolerances for all the bearings, and what works and doesn't. Then they would have the Ported heads matched to the Intake, and flowed that way. Then they would have a Cam custom built for that combination.

Same thing for Stereo equip. An "Ok" install would be just swapping out speakers or components.

A "Good" install would go for better equipment, and pay attention to some of the therories involved in Sound Reproduction. Like how a x-over works. Amp Gains. etc. Better than normal knowledge.

A "Great" install would have a Package put together based on the Application of the system. (Hence I'm always asking what Kind of music you listen to when making recommendations) Could go for just a Good street install, SQ competetion, SPL comp., Etc.........

It would focus on these goals and choose parts for that type of purpose. For SQ comp, Kick panel speakers, UnderDash compression horn drivers, Appriotic Dampening pads, and other esoteric stuff starts to be consisdered. You begin to choose equipment for SQ purposes. Stuff like THD, S/N ratios, Stereo Seperation, Skew factors, become important.

You also need test equipment to set stuff up right. RTA's, Pink noise, O-scopes. Freq generators, Tape measures for freq. become more important. You have to pay much more attention to physics to know what is going on. You would have to decide between Active and Passive x-over's. Building Mock-up panels to test with. A lot more work.