400.4 X-over Question

[dolfan87]

When using the amp to bi-amp a set of components, does the internal X-over have a limit on the bottom end,or does it just allow the mid-bass to play full range?

I am asking because I want to cross my midbass at 80-90hz, up to around 2.5khz where the tweets will kick in.

So will I need a seperate X-over?

87

[exalted512]

why so high??
-Cody

[Jstas]

Did your components not come with external crossovers? What kind of speakers are you using? If you do not have external crossovers that allow a bi-amping option(two circuits in the crossover, one for highs, one for lows) you are either going to have to find a crossover that will work for you or you would be better served by returning your 400.4 and getting a pair of 2 channel amps with an active crossover network. That way one amp runs the highs and the other amp runs the lows and the crossover networked is handled at the line signal level.

why so high??

2500Hz is not really high at all. Infact, that is pretty much smack in the middle of the mid-range. Most crossover networks will cut the upper mid-range crossover point at right around 2000-8000 Hz depending on the crossover topography and properties of the drivers and enclosures. Although, 2500 is a tad low for a two-way crossover network. I would sooner put the crossover point up around 4-6kHz and cut the tweeter off around the 3500Hz-4kHz mark to get a decent overlap to cover fall-off. If the drivers were capable of handling that crossover point.

[exalted512]

i was referring to the 80-90Hz
-Cody

[Jstas]

Oh, I see. Sorry. Well, it's not really all that high. Sure, everyone is used to running subs at 80 Hz and lower but some people run them at around 100-120 Hz, especially in ported enclosures. Unless of course it is a bandpass setup. Then I have set up crossover networks to keep excessivly high frequencies from getting to the subs but it still allows the full frequency range that the bandpass is designed to reproduce to reach the subs without truncating the already truncated response of the bandpass enclosure.

That's all conjecture though and to really understand what's going on, more info on what he wants to do is needed.

[dolfan87]

Guys, I am running Image Dynamics CX52 components with the NX30 tweet.

I was asking about the internal X-over because I am setting my sub to play from around 80-90 down, so the 5.25"s only need to cover from there up.

The 400.4 is basically two, 2 channel amps built onto the same chassis. I have two sets of RCA inputs, thus I could buy a 2 way X-over and get the same effects without selling my amp and buying two others.

Can anyone answer my original question?

87

[Jstas]

I think you just answered you're original question.

If you crossover your subs at 80 Hz and your full range speakers at 80Hz, you are going to have a fat hole in your response curve that will kill a good portion of your bass information right in the 50-120 Hz range. Your setting choices have not taken into account frequency curve falloff which can be drastic. You should lower your lower crossover frequency for teh mid-range to 50-60 Hz to adequatly cover the upper register fall-off from the subs. I know the ID CX52's are capable of it, I used a set myself and ran them at that crossover frequency without issue.

As far as your crossovers, if you didn't get the ID crossovers like these:


http://www.cardomain.com/item/IDSX4

then you will have to buy them seperatly. I would not bother at this point though because it does not seem that those crossovers are bi-ampable. You will need to get yourself a line-level active crossover like this:

http://www.cardomain.com/item/PHOTX2

[neomagus00]

I don't believe you need anything else: the Pre-EQ button on the 400.4 will do rather well, i think:

"In the C400.4, Pre-EQ is an auto-preset filter (2nd Order HP, Fc 5.5kHz, Q of 0.707; 2nd Order LP, Fc 3kHz, Q of 0.707; 3rd order HP, Fc 50Hz, Q of 0.707; Notch Filter, Fc 11.7kHz, Q of 5.5, -2dB) that replaces the MMC Series passive Xover, and provides greater dynamic range and efficiency with MMC Series Speakers."

That'll cut your tweets at 5500 and bandpass your mids at 50 and 3000 (i'm pretty sure those frequencies are at the beginning of rolloff, NOT the -3dB point that is usually quoted - but even if they're not, it's meant to do this). The 50 is a mite low, so you could use the 400.4's xover on highpass to tweak that bottom number for the mids. the standard biamp setup is used - 2 tweets off the front channels, and 2 mids off the rears.

[dolfan87]

Originally posted by neomagus00
I don't believe you need anything else: the Pre-EQ button on the 400.4 will do rather well, i think:

"In the C400.4, Pre-EQ is an auto-preset filter (2nd Order HP, Fc 5.5kHz, Q of 0.707; 2nd Order LP, Fc 3kHz, Q of 0.707; 3rd order HP, Fc 50Hz, Q of 0.707; Notch Filter, Fc 11.7kHz, Q of 5.5, -2dB) that replaces the MMC Series passive Xover, and provides greater dynamic range and efficiency with MMC Series Speakers."

That'll cut your tweets at 5500 and bandpass your mids at 50 and 3000 (i'm pretty sure those frequencies are at the beginning of rolloff, NOT the -3dB point that is usually quoted - but even if they're not, it's meant to do this). The 50 is a mite low, so you could use the 400.4's xover on highpass to tweak that bottom number for the mids. the standard biamp setup is used - 2 tweets off the front channels, and 2 mids off the rears.

Those were exactly the numbers I was looking for. I will use the amps x-over then.

Thanks for your help.

[MacLeod]

A little late but I agree the 400.4 will work fine and I applaud your wanting to bi-amp. Im a huge advocate of this practice.

Jstas makes a good point, you dont necessarily want to cross your mids and the same point of the sub. Its usually better I have found to cross the mids a little lower then the sub. My mids are crossed at 50 Hz and my sub at 70 Hz. A little overlapping helps blend them in better. You want to have the illusion the bass is coming from the front with the rest of the music and overlapping helps this.

[dolfan87]

Originally posted by MacLeod
A little late but I agree the 400.4 will work fine and I applaud your wanting to bi-amp. Im a huge advocate of this practice.

Jstas makes a good point, you dont necessarily want to cross your mids and the same point of the sub. Its usually better I have found to cross the mids a little lower then the sub. My mids are crossed at 50 Hz and my sub at 70 Hz. A little overlapping helps blend them in better. You want to have the illusion the bass is coming from the front with the rest of the music and overlapping helps this.

My problem is in the fact that I am running the 5.25"s, and I want to free them up a bit. Having them try to play down to 50 hz will only make it harder for them to play clean clear midbass and mids.

I haven't got the speakers in the car yet, so I obviously will play around with X-over points if I don't like how the 400.4's internal preset works out.

I do have a set of MB Quart passives that will allow me to bi amp, and they are designed for the 5.25".

We'll see.

87