Just got the sub to complete my SQ system - need some tips hooking it up
 

Hey guys,

So I'm an SQ fanatic and now have the ultimate sound quality system. Well, for me it is! I have the following:

Head Unit: Pioneer DEH-P800PRS (Dual 16-band EQ copper chassis burr-brown dacs the whole works..)
Fronts: JL Audio C5 Components 6.5"
Speaker amp: JL Audio 300/4 v2 Slash Amp
Subwoofer amp: MRPM-2000

And the sub I am putting in is a Boston Acoustics G5 Dual 4 ohm subwoofer.

What my question is basically regarding the ohms. I'm wondering if it's OK and if it's actually better in this case to run the subwoofer at 8 ohms - I know 8ohms is generally used for sound quality setups if possible, and in this case I can because I have an amplifier rated for 2300 watts RMS at 2 ohms, which will mean around 1000 at 8 ohms. I only plan to run the one subwoofer, and it's also in a ported box so power is no issue.

Just worried about the amp. Other then that, it's all setup and time corrected just need to put it in and do a bit of tuning!

Thanks guys.

if you have enough power at 8ohm then do it. you may not notice a difference in sound quality, but it means less draw and heat generated by the amp.
as long as you have sufficient power, then there isn't really a drawback.

Hi there,

Thanks for your response. That's what I figured too - less draw on the amp, less draw on the alternator, all around good stuff for the equipment. Plus I think running 2300 watts into the one sub is too much! I have the big alternator but that's just a lot of power to throw at the little sub, even with the gains all the way down.

Thanks again! I'm gonna hook that sub up right now and we'll see how she goes.

All right, all finished! I got it hooked up at 8 ohms and no problems whatsoever.

In fact, I'm very happy how it turned out because the gain on my amp isn't even at nominal and I'm getting a LOT of bass! The sub even hits full excursion. Quite the setup I must say.

Again thanks for your quick reply. I wouldn't have put it in this morning if I didn't know better. But I do now and it sounds INCREDIBLE!

I'll have to get some pictures of it all :)

Cant wait to see pics!

Lymen

glad you're happy! I'd like to see pics too. that is some nice gear you have.

Thanks! Speaking about my gear, do you know much the DEH-P800PRS? I know what specs it has but I know nothing of the actual components inside.

I'm assuming it's something like the DEX-P99RS, but I doubt it's anywhere near it! :)

it is a completely different beast than the P99.

the 800 is an amazing unit in its own right though.
there are lots of threads floating around the internet on both units.

once you get good at tuning, you will really be able to dial it in with the 800. do some reading on tuning with and utilizing a L/R eq as well as T/A. It is a little different process than a combined eq.

Hey jstoner22,

Well I did indeed do some research. Wow, you aren't kidding! I had no idea what I had until now - this thing is incredible. It's almost a crime what I originally paid for it!

I understand what you mean about the left/right equalization. You have to long-press the multi control button while in audio adjustments to get into the independent mode. And also I had no idea about the 3-way network mode. Truly incredible device. After learning all of this I have a new plan with my stereo, and I was wondering if I could get your input.

The way it is right now my front speakers are bridged on the 300/4. I'm going to change that; I'm going to run my 6.5" drivers off of one channel and my tweets off of the other. As far as crossovers go, I'm not sure if I should use the crossover supplied by JL or just completely toss it altogether and only use the DEH-P800PRS. My feelings are leaning towards that - much simpler, but the only drawback is all the settings are kept inside of the DEH-P800PRS. I do have a solution though and that is to just simply write down all of the settings. I don't have a problem redoing them if that needed to happen.

Then after that it all comes down to a matter of tuning, but with THAT amount of separation between the channels and that much adjustment I can see how much of an upgrade it will be. I've never tuned a system before so this will be an awesome learning experience.

Thanks for the advice. I didn't even realize there was so much more info on the internet about the unit. Thought I had found everything until I looked a little more :) It really is an amazing unit.

You already have the means, so I would definitely go active.

You will be able to fine tune it much better like that. The passives are convenient if you don't have the DSP capabilities and just want a plug and play, but that isn't the case with you.

Run each driver of a single channel. Then you gain the ability to properly time align and can level match the gains between tweeters and mids and sub much better.

Sounds like you are quickly learning a lot! Just keep reading and asking questions!

Personally for the tuning I will,
set my crossover points & slopes
level match gains
t/a
adjust combined eq by ear so each frequency band is same volume
adjust eq L/R separately for center image
t/a

everyone is going to do it differently though.

Thanks for the info.

I am definitely learning an immense amount here in a short amount of time. The real fun is yet to begin, though!

Basically I'm just waiting on getting some speaker wire for the tweets and then I am gonna go ahead with the upgrade. At that point I'll shoot some pictures and put them up when I'm all done :)

For the tuning part, I understand how slopes and octaves work. The only thing I'm wondering about is setting crossover points - is there any objective information you use as a reference point or is it all done by ear (or RTA if you had one)? I guess I'm just worried about damaging the equipment.

Thanks again, you've been very helpful!

no problem.

the crossover points are really going to vary depending on your car and listening habits.

look into the manufacturers specs on the drivers to get a baseline of what the drive is capable off first.

while at my loudest listening levels, I will generally cross my drivers as low as possible while maintaining safe operation and just tweak from there.
you are listening to it, not a machine. personally I do it all by ear.

^ Agreed. I like to start at the top for crossover points and work down. So I start with the tweet and set my initial crossover point at 2x Fs. So if the driver has an Fs of 1800hz, I start in the 3600hz range and go from there. If you have a slope steeper than 12db you can lower the point if desired but be careful. Play your music at a fair volume and listen for distress.

Then move onto the mid. I set the low pass of the mid at or up to half an octave below where the tweeter is high passed. Again, set the high pass at about 2x Fs and work from there. First play the mid alone and work the low pass until you drop it to where the mid still plays clean and without distress. Now bring the tweet back in and work the high pass on the mid so they blend well.

Move onto a midbass if you have it. Set it up the same way as the mid.

Finally end with the sub.

One of the things many people new to active systems get hung up on is gap and overlap. It is natural to think that one speaker should end at the same frequency the next begins. Truly, depending on your car, speakers, and setup, you may arrive at your best sound with one speaker overlapping another or with a gap between two speakers. Don't sweat it - you're not going to hear a half or octave wide gap, even with 18db or 24db slopes. Set it up so it sounds right, not what your pencil tells you should be right.

Thanks for all the information, jstoner22 and Dukk. That is extremely helpful. Especially since I will be doing this upgrade today or tomorrow :)

Quick question for you Dukk, regarding Fs, how do you determine the Fs of the midrange and tweet? The box for my C5's as well as the manual do not state anything about these kind of specs. Is there any way of determining it or should I just ballpark it?

On JL's website for the tweet, they say: "The C5-100ct is designed to operate above 5 kHz with a minimum high-pass slope of 12 dB / octave."

They are talking about the 1" tweet, but it's identical otherwise. So my guess for this is the Fs is around 2k hz? But that's probably not accurate. Basically I just want to know if it's really important to know it or not, or if there's another way to determine a good starting point.

Thanks again guys this is helping me big time. I will actually have a well-tuned system now :)

If you don't have access to Fs then look either at the crossover point of the manufacturer passive or any suggestion from the manufacturer, in this case 5k, which IMO is pretty high but not unheard of. What diameter is the midrange?

It's the JL Audio C5 component set - comes with a 6.5" midrange woofer and a 0.75" tweet.