I just finished installing a MTX 10" 6000 series sub and MTX 6152 amp in my car last night. I had these laying around, so I built the box from some plans and wired it up. I went for a cruise and noticed something a bit odd....

With the windows cracked a little ways or down completely, the system absolutely pounds. Things are shaking, I can feel the bass, sounds pretty good all around. With the windows up, the sub seems stifled. I mean the hit almost entirely goes away. You can still "hear" that the system is playing lower notes...but the hit is really diminished. Any ideas??

The sub - MTX T61044a (dual 4 ohm vc; 250W rms/500W max power handling)
The amp - MTX Thunder6152 (90W rms x2 @ 4ohm or 325W rms x 1 bridged @ 4 ohm)
The box - similar to a Subthump stealth box (.76 cubic foot airspace)

Since I thought it would be underpowered to hook both voicecoils (one to each channel of the amp) I simply bridged the amp and ran the leads to one voicecoil. The other voicecoil is just un-powered. Any ideas since it hits hard with the windows down but not up?? Thanks!

 

Hmm. Is the box sealed? What is it crossed over at? Seems kinda strange to be acting like that, and I would experiment with wiring options to see what sounded best.

Fej

 

Fej...thanks for the ideas....

The box is sealed. I don't know the specific crossover point. I am using a PAC AOEM-VET1 adapter to send full range back to the MTX amp. I have it set for low pass and have tried turning the crossover freq **** to various positions. There are no markings to show what it's at...

I know the MTX literature says in LP mode, the freq is from 40-200 Hz. I have it turned around half way...my guess is it is at 100 Hz now.

The whole window up/window down thing is throwing me. Usually with windows up, a vehicle sounds and hits harder due to confined airspace. The air doesn't "leak" out of the car. Nice terminology there isn't it.

 

DOH!!
Please, before damage is done, wire up both voice coils to the amp. You will damage the woofer by just running one voice coil of a dual voice coil sub.

 

I forgot, your sub will sound better with just 180 watts wired correctly

 

If you are havin trbl let me know I will be more then willing to help a buddy out

 

Knewblew...will do. I'll change the wiring tonight. I figured it was worth a shot as I have had that sub and amp laying around unused for a year and I got them used.

Greg...I am hoping to meet up with you and Dave someday. I saw Dave's car on Sat and it rocked! I think he mentioned you were working when he and I met up. Thanks for the offer to help

 

yeah I had work... we are doin his components tonite

 

Yeah...that's what Dave had told me. I'll be looking forward to hearing them as I am leaning towards CDT's when I do an install in my car.

I'm anxious to see if hooking up both vc's will help with my sub issue. The hit really diminished when I rolled up the windows....

 

Got home and did as KnewBlew suggested and hooked up the two voicecoils. I ended up running the two voicecoils in parallel (a 2 ohm load now) and hooked it to one channel of the amp (165w RMS). Sounds really good and was hitting much harder with the windows up and everything sealed shut.

With the windows cracked open, the hit was still there. I thought I perceived the sub hitting lower frequencies with the windows open, but that might just be my imagination. Definitely an improvement in sound and "hit" by using both voicecoils compared to how I had it last night.

My next thing to try is run each voicecoil to a channel on the amp. This will give me 90w RMS to each voicecoil (180w RMS total compared to the current 165w RMS). I need to buy and install another speaker plate (binding post) in order to run speaker wire from each channel of the amp to each voicecoil.

This may help with slightly more power but also better damping. The amp will be running two 4 ohm loads instead of a single 2 ohm load. Thanks for the help everyone

 

Ok, I haven't taken the time to read the other responses so I may be repaeating what has been mentioned already.

1. wire up the sub correctly using both voice coils. It will sound better and you won't damage the sub that way. if the amp pwering it has a "mono" mode switch it to that so that both left and right chaneels are feeding the voice coils the same information. In stereo mode the channels are often different information and throwing two different signals to the seperate voice coils is not a good thing.

2. the reason the bass sounds and hits harder with the windows down is a basic accousic theory. The lower the frequency being reproduced the longer the soundwave is that must develop before it can be heard. with the windows closed the soundwave is "trapped" within a very small, confined space and cannot develop properly therefore the reason for your "stifled" sound.
opening the windows allows the soundwave to expand to it's correct length although it's doing it outside of the car. You will hear the difference in the car as you have noticed because you are actually sitting within the soundwave itself but it's going to sound even better outside the car than it does inside. Small cars and small interiors such as our Vettes many times require special "attention" to get things to sound right, especially in the lower frequencies because of this.
You can try changing the positioning of the sub to make a difference. For example, instead of placing the sub at the back wall firing forward ( I have no idea how you have your sub placed but i'm using this as an example) try placing the subbox directly behind the seats and firing back toward the rear of the car. What happens there is you increase the path the soundwave has to travel so it can develop more fully because it will than reflect off the backwall and go forward. It's best if you can place the sub low and just slightly angle it up so it's not firing DIRECTLY straight back. even just a very slight angle to it helps.
you can measure this yourself: measure from the back wall to the windshield of the car. write that length down. Now, measure from the backs of the seats to the back wall and back up to the windshield.
The longer the soundwave has time to develop the better.
You will never get the entire soundwave to deveopment inside the car but you do need a mininuum percentage of it to develop first before you can actually have the frequency become audible

 

Run the amp bridged at 2 ohms the MTX isnt necesarily rated for it but it will take it just fine and will give u the best amount of power

 

BarryK....thanks. KnewBlew had already suggested wiring up both VC's and I did in fact do that. Sounds much better. I did perceive lower frequencies with the windows down compared to up and that is probably because of what you said about more airspace and length to develop the wave.

Pentavolvo...will try that. I didn't want to go hurting the ol' MTX, but ehh.... Now if I follow your advice, do you promise to give me an amp if mine melts down.

 

if you don't want to bridge it at two ohms just run the coils in series and bridge the amp. It will give you the same power as running a channel to each voicecoil and you won't run into any problems with variations in signal/gains on each voice coil.

 

that is great advice, never thought about it that way.

 

Thanks for the suggestion.... I currently have the sub's voice coils wired in parallel inside the box. I am using just one channel of the two channel amp to power it. So there isn't any gain issues between vc's the way I have it right now.

Granted the way it is right now, I could possibly be missing some signal input into the amp since I believe the left RCA input is the only input tied to channel one. The right RCA input is just going nowhere since there isn't anything hooked to amplified output.

I just got back from a nice cruise and it is sounding pretty good. I think any more power to the sub and it'll over run the Bose. I may just try MYKVR6's idea so that I will have the same power as right now but with the added bonus of using signal input from both RCA's.

 

Glad you got it resolved!

If it's any consolation, voice coil wiring is what I was thinking as I read your initial post.

I made a mistake and wired up a DVC sub wrong, so one was reverse of the other! Guess what? nothing much happened...

 

Bogus...thanks! I didn't think not powering one of the voice coils would make that kinda difference. I appreciate your consolation

Definitely adding that sub made a world of difference. I actually feel a part of the music now

 

music should be experienced as much as heard!

Glad it's working!!!!

 

Yeah a sub IMO is necessary in every stereo, it adds a nice fill to it and rounds it off, then again 2 12s is always nice as well haha