New Setup Questions - Speaker Level Inputs

[Potsy24]

Hi everyone, this is my first post here. I tried searching, but did not find the answer to this. I'm installing a Rockville Rockghost powered sub, a Pioneer GM-D1004 mini amp to drive the speakers (45 watts X 4 RMS), and all new speakers (matched to Pioneer RMS) in a 2016 Kia Forte5 SX. I want to keep the stock stereo, so I know I'll be using speaker level inputs for both amps.

My question is: for the sub, should I use the signal from the stereo (split the front speaker signal and send to both amps), or should I use the stronger signal coming out of the Pioneer amp? Would using the output of the Pioneer amp have a negative effect on the signal to the speakers or damage either of the amps? Is there even an advantage to using the higher wattage signal? Thanks in advance!

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[BCotrell]

The speaker signal is a high level. The Rockville unit you bought specifies low level. You need to connect the high levels into the aftermarket amp and find and amp that has an additional preout. That amp you specified doesn’t have that. Can you return it and get a gm-d8704? It has a preamp that can be used for that purpose.

 

[Potsy24]

The speaker signal is a high level. The Rockville unit you bought specifies low level. You need to connect the high levels into the aftermarket amp and find and amp that has an additional preout. That amp you specified doesn’t have that. Can you return it and get a gm-d8704? It has a preamp that can be used for that purpose.

Thanks for the reply! It's only low level for the RCA inputs. It has at separate high level inputs. I'm just trying to figure out which high level outputs to use (factory HU out or mini amp). Here's the section of the subwoofer manual about that:

 

[BCotrell]

Yeah but you need a flat de equalized signal which your high level inputs will likely not provide and may even include bass limiting (to protect weak factory speakers). Specific to bass, Your strategy would be better if you had factory subs because you would have high level sub channels. I’d switch that amp to an amp with an extra rca out (like that pioneer)

 

[Potsy24]

That particular amp wouldn't work for what I'm trying to do. The one I chose is designed to be tucked away behind the dash and is rated at half the power of the one you suggested. So the speakers I already ordered are also rated for 45 watts RMS. The biggest goal is to improve the sound of the stock system a little and have no extra audio equipment visible. I don't want to change the appearance or practicality of the car at all. I know that makes for less than the perfect setup, but that's ok.

Anyway, if the high level outputs of the stock hu already have some of the low end rolled off-- I don't know that converting to line level would help that. Maybe there are locs or amps that have eq built into their line outputs, but there's eq built into most every sub amp already (bass boost is just a 40 hz shelf eq right?). It can’t boost what isn't there, but if the lows are just cut and not completely gone it'll help.

 

[BCotrell]

That particular amp wouldn't work for what I'm trying to do. The one I chose is designed to be tucked away behind the dash and is rated at half the power of the one you suggested. So the speakers I already ordered are also rated for 45 watts RMS. The biggest goal is to improve the sound of the stock system a little and have no extra audio equipment visible. I don't want to change the appearance or practicality of the car at all. I know that makes for less than the perfect setup, but that's ok.

Anyway, if the high level outputs of the stock hu already have some of the low end rolled off-- I don't know that converting to line level would help that. Maybe there are locs or amps that have eq built into their line outputs, but there's eq built into most every sub amp already (bass boost is just a 40 hz shelf eq right?). It can’t boost what isn't there, but if the lows are just cut and not completely gone it'll help.

the speaker high inputs are not subwoofer inputs they are for full range door speakers. They are equalized by the factory headunit. You won’t be able to correct that on the sub if you use those high level inputs for your sub. They’re probably fine for your aftermarket speakers (might sound meh at high volumes)

bass boost won’t boost something that won’t be there. Don’t want to be a hater on your plan though so here you go, I assume you bought component with a crossover up front and coaxials in the back or coaxials all the way around. If that’s correct you don’t need filters but that addition preout would be a big win.

similar micro amp but with preout that will be a low voltage rca preout

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[Potsy24]

Thanks, I'll check that out

 

[n2audio 5,000+ posts]

You would not want to use an amplified signal for input to a 2nd amp. 45w at 4 ohms is about 13v -- that's extremely high for any amp input.

I would use stock front speaker outputs for the pio amp's front inputs, and stock rear speaker outputs for the pio's rear AND the rockville inputs.

Regarding stock HU bass filtering -- Here's a little experiment you could do (assuming your stock radio has an aux input -- BT or wired doesn't matter)...
Get access to a speaker wire where you can connect a DMM (you can find them for <$10). Download a tone generator on your phone. Play a 100hz, maybe 200hz tone loud (phone 90%+ vol, HU ~75% vol). Measure the AC voltage -- probably 5-10v. Then play a 40 or 50hz tone and see how much the voltage drops.
If it's a lot, say - 50% it won't give you a good signal. If it's about the same or just 10 or 20% less it should be fine as the 45hz boost on the amp should allow you to make up the difference.

 

[Potsy24]

That was an extremely helpful reply, thank you for answering my question about which output to use. Also, I didn't think of testing the outputs with a multimeter like that. I can also compare front to rear that way and see if there is any difference. To my ears, just fading full front vs full rear, the front sounds much better. But I know they're the exact same speaker front and rear. It may just be because I was sitting in the front. I'd love to rely on a more scientific method. I'll let you know what happens.

 

[Potsy24]

I installed front and rear speakers today (of course they sound like crap because I haven't intalled the amp yet), and I checked out the voltage at different tones. Here's what I got:

Rear:
200 Hz - 1.8
100 Hz - 0.83
80 Hz - 1.55
50 Hz - 1.61
40 Hz - 1.13

Front:
200 Hz - 4.28
100 Hz - 5.26
80 Hz - 7.2
50 Hz - 6.5
40 Hz - 4.2

These may not have been at exactly the same volume front vs the back on the hu, but very close. I had read on a Kia forum that the front speakers got a lot more power than the back. And it makes sense to me, because I have had it faded to the rear a few clicks to get it to sound centered. I don't know why the rear has that dip at 100 Hz, but I checked multiple times to make sure. Anyway, it seems like this is a pretty good result and I'll be able to use the speaker outs for the amp input. I think I'll use the fronts to feed the subwoofer though, since it's a stronger signal and more even.

 

[n2audio 5,000+ posts]

Those are interesting numbers. Obvious attenuation in back.
Might think twice about using rear speakers outputs for the sub amp, although ~1v shouldn't be a deal breaker by any stretch.
It wasn't ALL that long ago the average hu line outputs were 1/2v

 

[keep_hope_alive Premium Member]

Awesome work taking those measurements. It's super common to see higher output voltages for the front speakers because we want sound to come from in front of us.

I do usually recommend just using the front output due to the higher signal, but the benefit of using the rear outputs for the sub is that the fader can act as a sub level control. Higher gain settings for the sub amp (to make up for the attenuated rear signal) are usually less problematic because you won't hear noise as well.

 

[Potsy24]

Well, yesterday I wired in the mini amp to drive the speakers (and the wires for the sub signal). It wasn't a dramatic improvement over stock, but it's hard to say since I keep doing it in increments. New speakers without the amp was worse than stock because they were underpowered. New speakers with the amp is better than that, and better than stock-- but not by a huge margin. Definitely more clarity on the low mids, like on low toms in rock/metal music. Not really more bass than stock, but these are just 6.5" speakers. Probably more clarity in general. I bet if I could a/b them I'd really hear a big difference. Anyway, the stock dash tweeters are out right now and I haven't added the new ones back in, and I still have the subwoofer to add. Hopefully with those and when the speakers break in a little, it'll be a much more impressive change. Hopefully tomorrow.

 

[Potsy24]

Oh, and the sub has a wired remote with gain, crossover, bass boost, and phase. It's actually the only place to control all those. That'll go to the glove box or center console. So I don't need to worry about using the stock hu to control the sub level.

 

[Potsy24]

I got the subwoofer installed today and I'm really happy with how the car sounds. This Rockville Rockghost sub is actually pretty good. Not bone shaking, but that's not what I wanted. It does sound super tight and clean, and plenty of volume for me with the gain around 50%. It can go up to 80-90% before it gets distorted, so it's not like I'm even pushing it as hard as it can go. And my main goal was to have great sound without changing or seeing anything else. I did crack one trim peice by the driver's door, so I'll try to find a replacement.

I still have to install dash tweeters. I'm using 3 ways in all 4 doors, so it sounds good for now and hopefully even better later. This is the same setup the car had stock-- full range in the doors with no crossover and tweeters in the dash with an inline crossover. I'm calling this project a success! Thanks for the help!