high distortion MM2124

bordominc

I've had a problem with this for a while..... I have 2 MM2124's and I first had them in a small sealed enclosure. They can play real low notes fine, but when its a higher not it distorts really bad...the higher the volume the more sensitive it is....so i thought i would build a ported box. I called polk and they told me how large to make the port... 2" X 13" X 6" with each chamber having 1.5 cu ft. I made the box and the subs are a lot louder along with the distortion. Im powering them with a Rockford Fosgate 500w MONO, i even used a diff amp to make sure that isnt the problem...but same thing happened. Anyone have any suggestions? Thanks

neomagus00

i'm assuming you've tried this with many types of music, and that it happens for every song you play. at what frequency are they crossed over?

i've personally never heard of the higher sub-bass distorting, but i'm sure we can help you figure it out...

bordominc

The amp itself has a frequency x-over however i am not using a seperate x-over. If thats what your talking about, I have turned the nob from the lowest to the highest....the higher i go the easier it distorts (even the lowest notes distort). And I've tried every type of music.

1996blackmax

What knob are you turning? I hope not the gain control. Are you sure that the gains are adjusted correctly?

bordominc

no i have the gain set at 50%, im turning the freq. control. Im gonna put some different subs in the box to see if they distort.....it might just be something wrong with these subs?.?.?

MacLeod

You may have your gain turned up too high. 50% is about as high as youd ever want to go with any quality aftermaket head unit. Ive got mine set at about 25%. You may want to back it down a bit and see cause the amp may be clipping.

I have nearly 400 watts going to my MM2104 and it hasnt sputtered yet.

neomagus00

http://www.andrew.cmu.edu/user/dhuston/gains.html

run through that, just to make mac happy

as a note, you'll want that frequency dial to show 80 Hz or less... what you're hearing as 'distortion' may very well be the lower registers of guitar and voice, and the low notes of voice and guitar sound really really weird by themselves... you'll want the highpass xover up front to match the lowpass xover for the subs. you also want the slope, if you have a choice, as steep as possible for the sub, trial and error for the front.

can you give us a list of EVERYTHING you have in the car? that may help narrow it down...

bordominc

I have a pioneer 7600 head unit, all stock front/rear, and the 2 mm2124 with the RF amp. I have had it all wired in a whole seperate car and it did the same thing. I have tweaked the gain control but the higher I go the more it distorts, the lowest is pretty much nothing and everthing in between is gradually worse. I have never had anything like this happen before...I have a friend that has 2 pioneer 12's that im gonna put in my box with my amp to see if they distort at all....im thinking its something wrong with the subs.

Jstas

Do you have your tone cntrols turned all the way up?

It sounds to me like you do. The distortion you are getting is not amp clipping but rather signal clipping.

Thom

If you're crossing the subs over at 250 Hz or higher it's going to sound bad. Try other subs and see if you're happier, but I don't see why you'd want a sub crossed over higher than 80 Hz. I usually lowpass subwoofers between 50- 80 Hz. You could be lowpassing at 250 at 12 db/ octave and nothing will sound good. They're subwoofers, not midranges.

bordominc

i feel so stupid.....i was getting pretty mad and went out and pulled my h/u and everything out.....went and bought an optima batt. (i've been having batt. troubles too) and reinstalled everything.....to my amazement, i had the subs out of phase.....go figure.... thank you all for your help...now if anyone has the same problem tell them to make sure they are in phase....dangit... thanks

MacLeod

That shouldnt cause distortion. Wiring the sub out of phase would only make it fire behind the speakers making it a split second out of sync. Hmmm, maybe that small delay sounded like distortion or something. Maybe it was a problem elsewhere and when you reinstalled it you fixed it without knowing what it was.

PoweredByDodge

if one sub was out of phase with the other it would mac... espeically if they share air space.

if it was a PERFECTLY sealed box, then you'd get just "0" music output... but if it was a leaky **** of a box, it would play - like dog ****.

i usally low ball subs at about 75 to 85, so i agree with Thom on that. i think just about everybody x's subs no higher than the 80's ... they usually just get sloppy after that (any brand). my truck is a different story - the 10's and 12's overlap only a bit and the 10's are actually bandpassed. that's only because i'm using them as a sort of hybrid speaker... breaching what i perceived as a gap in my listening... but they're still under 150 hz.

MacLeod

PoweredByDodge wrote:

if one sub was out of phase with the other it would mac... espeically if they share air space.

Good point. I didnt think about that. 2 subs sharing the same air space firing at different times could cause distortion in the air inside the enclosure and transfer to the sub.

erobinson

MacLeod wrote:

That shouldnt cause distortion. Wiring the sub out of phase would only make it fire behind the speakers making it a split second out of sync. Hmmm, maybe that small delay sounded like distortion or something. Maybe it was a problem elsewhere and when you reinstalled it you fixed it without knowing what it was.

While agree something else fixed it, and that it wouldn't cause distortion, by saying wiring out of phase causes a small delay gives him the wrong impression. Swapping leads to cause a speaker to be out of phase will cause it to be exactly 180 degrees out of phase, and the speaker does not lag (nor would it at any phase angle). It simply moves in when the other in-phase speakers move out. It plays notes at the same time as all the other speakers, and does everything else the same. The only negative effect is cancellation as you probably know, I just want to clear it up for the thread poster. Some people purposely wire their subs out of phase (often called reverse phase) to actually improve sound quality in certain situations.

erobinson

PoweredByDodge wrote:

if one sub was out of phase with the other it would mac... espeically if they share air space.

if it was a PERFECTLY sealed box, then you'd get just "0" music output... but if it was a leaky **** of a box, it would play - like dog ****.

i usally low ball subs at about 75 to 85, so i agree with Thom on that. i think just about everybody x's subs no higher than the 80's ... they usually just get sloppy after that (any brand). my truck is a different story - the 10's and 12's overlap only a bit and the 10's are actually bandpassed. that's only because i'm using them as a sort of hybrid speaker... breaching what i perceived as a gap in my listening... but they're still under 150 hz.

Not ALL subwoofers get sloppy above the magical 80Hz point. If they did you better have some infinite slope XO on that sub. I mean, most people using 12dB slopes would only realize a halving of volume by 160Hz. Some subwoofers are designed to be able to be crossed over in the 1xx region.

PoweredByDodge

many subwoofers can play nicely into the 100's and beyond. most people are dumping a 40 hertz boost onto an already 100 hertz boosted deck signal, and then pushing a "loudness" button, and in the end they are lucky that the speaker sounds good up to 80 or 90 hertz. once you go past that, the overlap with front speakers that are not crossed over properly to blend with the subwoofers (or vice versa) results in ghost sounds that move the sound stage into places not imagined possible. while high frequencies may be what some consider the indicators of a sound stage, you can easily - inadvertantly - pull a sound stage out of wack with mid-bass as well. for the average do-it-your-self-er 80 - 85 hertz is what they should use for a crossover points for both highs and lows. if someone knows enough about audio to go playing with it, then they should know enough to adjust their highs, if necessary, to compensate and blend in a manner than reinforces the music and brings out the best overall sound. they should also be aware that you cannot drive the living hell out of a subwoofer when reaching the upper limit of its frequency range. i'm running 500 watt subwoofers in the 350 - 400 watt range and i still think they're taking a beating. a high mass piece of material is simply not meant to move that fast. the faster you move it, the more stress is placed upon the structure. heavy cones (relative to say a cone from a 6.5" round or even a 12" midbass woofer as opposed to a subwoofer) latched onto heavy spiders and heavy rubber surrounds being whipped back and forth at frequencies that they should either not be played at or played at only by people that can do so with an understand of what is actually happening to the driver, take that into account and leave 'room for error', and generally play the driver in a manner that does not damage it. the original poster, nothing against him/her, is amongst those 90% of car audio owners who do not fully grasp this concept. he / she i'm sure has gotten something out of this whole exercise, but that still leaves us with the vast majority of people who use a subwoofer having to keep it around 85, less their driver sounds like **** and acts like slop.

erobinson

PoweredByDodge wrote:

many subwoofers can play nicely into the 100's and beyond. most people are dumping a 40 hertz boost onto an already 100 hertz boosted deck signal, and then pushing a "loudness" button, and in the end they are lucky that the speaker sounds good up to 80 or 90 hertz. once you go past that, the overlap with front speakers that are not crossed over properly to blend with the subwoofers (or vice versa) results in ghost sounds that move the sound stage into places not imagined possible. while high frequencies may be what some consider the indicators of a sound stage, you can easily - inadvertantly - pull a sound stage out of wack with mid-bass as well. for the average do-it-your-self-er 80 - 85 hertz is what they should use for a crossover points for both highs and lows. if someone knows enough about audio to go playing with it, then they should know enough to adjust their highs, if necessary, to compensate and blend in a manner than reinforces the music and brings out the best overall sound. they should also be aware that you cannot drive the living hell out of a subwoofer when reaching the upper limit of its frequency range. i'm running 500 watt subwoofers in the 350 - 400 watt range and i still think they're taking a beating. a high mass piece of material is simply not meant to move that fast. the faster you move it, the more stress is placed upon the structure. heavy cones (relative to say a cone from a 6.5" round or even a 12" midbass woofer as opposed to a subwoofer) latched onto heavy spiders and heavy rubber surrounds being whipped back and forth at frequencies that they should either not be played at or played at only by people that can do so with an understand of what is actually happening to the driver, take that into account and leave 'room for error', and generally play the driver in a manner that does not damage it. the original poster, nothing against him/her, is amongst those 90% of car audio owners who do not fully grasp this concept. he / she i'm sure has gotten something out of this whole exercise, but that still leaves us with the vast majority of people who use a subwoofer having to keep it around 85, less their driver sounds like **** and acts like slop.

I agree. The only problem being that most people don't run mid-ranges that have a 3dB cut-off point at 80Hz, so then they complain of mid-bass problems if you set the XO there. I'd say up to 100Hz isn't going to hurt too bad, but certainly 80Hz is safer. It's definitely not localizable, which is something else you were getting at. Too many people run their subs so that you can hear even female voices coming out of them,

PoweredByDodge

well if you take a look at the really el'cheapo amps, i mean the horribly cheap ones like Boss and what not, the flea market stuff, it doesn't come with a crossover let alone an instruction manual. I wish when i got into audio somebody actually explained all this stuff to me instead of letting me spend money, break things, spend more money and time and effort, just to get what i could have gotten to begin with if a sales guy was being straight with me.

1996blackmax

PoweredByDodge wrote:

I wish when i got into audio somebody actually explained all this stuff to me instead of letting me spend money, break things, spend more money and time and effort, just to get what i could have gotten to begin with if a sales guy was being straight with me.

I love doing this in front of the sales person who is trying to ripp off someone who is not very knowledgable . I ususally just stay quiet up until the sales person starts spitting out bull, and then I just kind of butt in . I have made wrong decision based upon these guys and their "recommendations", and if I can help a young kid whose worked and saved for a while to get some audio gear, I will.

I was at a Tweeter a while back, and the guys started talking about how such brand was the best and this and that. I then said, "You guys are funny, you say something is the best when you guys carry the product, but last year when you did not it was almost crap according to you, and now the product you used to carry , the best one before this one, is not even mentioned by you. You guys totally confuse people."

Another time I told the guy, were you not the guy who told me that this brand was a Lamborghini and the one you are trying to push on me on me now was a Honda Accord? What changed between then and now that transformed the Accord into a Lambo?

A lot of guys are very helpful on the sales floor, just not all. One of my best friends was actually a sales guy at the Good Guys as well as Inredible Universe (before it became Fry's). He actually used to get into arguments with the manager at Incredible Universe because they would want him to pass refurbished stuff off as new. My friend would still tell people the truth. He eventually went back to the Good Guys. I wished all of the people were like him. He would find out what the person was after and help them out, not take advantage of them.