PostGrungeJunky

i've had my IDQ v2 10" 2 ohm dvc sub for several months now. they're sealed in a .66^" box. they're getting 150w wired in a series.

i noticed in recent days, they're starting to "bleat" thats the only word i can think of to describe it. kinda like "brbrbrbrbr" that makes your fronts sound as if a fan is blowin in front of it, when solid bass notes hit. er that helicopter noise effect...haha whatever.

at first i only listed to my fav rock records so there weren't any solid synthesized bass lines to stress it, just kick drums/percussion, and stuff, so the bass was really nice and tight, accurate. recently, i finally got around to bumpin' some of my rap/pop records and they're somewhat vibrat-y.

is this a gain thing? is this just a phenomena of a sealed box? did i fry my voice coils? i've had it crossed at around 65~ hz for a while and that x-over pt seems ideal so...

thanx!

NS98GSR

could be signal clipping (not enough power going to the sub from the amp so the ends of the signal get cut off -- very bad for your sub) or the sub itself could be damaged.

Pimpin Olds

Doesnt that happen when you blow your sub or damage it?

97teg

is each one getting 150w or are both together only getting 150w? Clipping happens when you drive the amp too hard and the signal going to the speaker is no longer "clean".

PostGrungeJunky

well, it's a 2ohm rated dvc sub, and it's wired in a series to channels 3/4 of my 4 ch amp bridged putting out 150 watts at 4 ohms. yeah 150's the total rms. the subs are rated to receive 250 rms.

**so is this clipping permanent? or can i just lower the gain and make it go away? i had no idea it was clipping cuz most of the music i played on this just had kick drums, no bass notes really consistent/clean like pop/hip hop/ r&b etc

97teg

Basically its just that you don't have enough power to run the subs and you are pushing them too hard. If they are 2 ohm dvc's then you should only be able to get a 2 ohm or 8 ohm or .5 ohm load. I don't think you are able to get a 4 ohm final load. You have two speakers right? Do you have all terminals on the speakers hooked up?
this shows they dvc subs can be hooked up. I think there is one more way to get an 8 ohm final load they dont' show.
http://www.jlaudio.com/tutorials/wiring/index.html

To keep it form clipping you can just turn the gain down on the sub channel and should be fine.

Mish

First off, clipping is not your problem.

Here's a quick lesson on clipping:
Clipping occurs when you try to drive your subs with more power than the amp can deliver. The amp has a set voltage peak (called the rail), The output voltage cannot be greater than this rail. The output of a normal signal is a sine wave (remember physics class??). As the volume of the hu is turned up, the voltage from the amp increases, which in turn increases the peak value of the sine wave. Once the hu is turned up high enough, the amp will no longer be able to push the voltage up any further because it's at it's rail. If you turn the hu up some more, then the amp will try to put out more voltage, but since it's at the rail, it can't. So it cuts the top of the wave off. This is clipping. The clipping iteslf is not bad (contrary to a common belief). What's bad is the power that is delivered in a clipped signal. Remember in calculus class, taking the area under the curve? Well if you look at it that way, you have more area under the curve with a clipped signal than you do with a normal sine wave (/\/\/\/\ <--- like that) because a clipped signal begins to look like a square wave (--_--_--_ <---Like that). This is what kills the subs. It's the over powering of them. NOT sending in distortion.

What is distortion? First lets look at what a clean signal is (sine wave). An ideal sine wave is a fundamental frequency. Void of any distortion. Just a clean signal. This is what your subs "play". The THD spec of an amp tells how well the amp will reproduce that signal without distortion. The distortion is added "harmonics" or "related" frequencies of the fundamental that the amp "adds" to the signal. Therefore, an amp with a lower THD value is a "cleaner" amp. Got that? Sorry for the physics and calculus lesson here, but there is a lot of mis information in this thread that I feel compelled to correct

So, back to the clipping. When a signal clips, the signal starts to turn into a square wave. --_--_--_--_ (<------ Like that). The square wave is made up of the fundamental AND all of the harmonics. Each of the harmonics carries a little bit of power with it. When you add this all up, you get tons of power from this signal. THIS IS WHAT KILLS THE SUBS!! It's the POWER, NOT the distortion.

Now about the 2 ohm DVC. I read your post and you say that you have 2 subs. You also state that they are in series. So you have 2 subs wired to be a 4 ohm load each? Then what happens to the subs? Are they then wired together in series to give an 8 ohm load to the amp? If so, you're fine. If you ran the subs in parallel here, you'd have a 2 ohm load. If the amp can handle this in mono mode, AND the rated output of the amp is less than the rated power of the subs, then your still good. The best thing to do is put a DMM on box and find out what the actual load to the amp is. Do that and let us know. I think you may be ok since the amp does not go into protect mode. If the amp is only rated at 4 ohms mono and you're runnning it at 2 ohms mono, I'd expect it to over heat and shut down at some point. Does this ever happen?

So what is your problem? I believe the "brbrbrbr" sound you describe is probably the voice coil of the sub smacking the magnet structure. This is due to over excursion. Not clipping. So what could cause this? Well over powering the sub may make it do this, but I think your problem is even more basic than that. I think you have a leak in your sub box! Damn all this typing just for that??? Here's how to check to see if this is the problem. CAREFULLY push the cone of the sub straight down. How long does it take to come back to rest? It should take about 5 seconds or so (maybe more) to come back. If the sub comes back pretty quickly, that is a good indicator that you have a leak somewhere.

Have you taken the subs out a lot? Sometimes the seal between the subs and box can go bad with a lot of removing of the subs. Is the foam gasket on the subs in good shape? Do the subs share the same air space? Somethings to take a look at over the long weekend.

Hope this helped

Mish

97teg

Yeah i guess i shouldn't have used the word "distortion" its no longer a sine wave balh balh but yeah your right . If not enough power would blow subs, they would blow every time you turn it down I read somewhere that when your clipping its like sending twice the power to the speaker. But if the speaker can take twice the power and still be ok it won't be a problem ie clipping a 100 watt amp to a 200 watt speaker youll still be ok. If hes running 8 ohms then isn't that only like 65 watts to BOTH speakers or 32 watts each? That seems like the subs are severly underpowered. As you go pass the rated power the thd goes up very quickly and eventually its enough to begin to hear it. When it hits on the back plate isn't it more of a "whack" sound thats what happenens? When i bottomed out my rf sub it was a really loud "crack". He says its more of a helicopter sound but hard to tell without actaully hearing it.

Mish

Good observation!!

Depends on the amount of clipping. A slightly clipped signal will not have twice the power. A severly clipped signal could. Thus the (man I hate to use the word) calculus speal in the last post. The area under the curve would tell you how much extra power is being delivered. But who the hell wants to do calculus anyway!! Just know that it is possible to send large amounts of power to a speaker when an amp goes into clipping.

Yup :thumbup:

Prolly. But we don't know what amp he's running or anything. He could be running a 2 ohm load and doubling the power he thinks he has. We don't know. He needs to use a DMM or ohm meter to tell us exactly what the load is to the amp and what amp he has. Then we can help more.

I'm not 100% on this so I could be wrong. But I believe that since the Fundamental is something like 60% of the power in a badly distorted signal, the speaker will only play the fundamental frequency. I believe that when the THD gets so high you are not actually hearing the THD, but the speaker's loss of control due to too much power. Again, I could be wrong.

If you bottom out on one note, you'll hear the "WHACK" like you heard. If you bottom out on a sustained note, then you'll hear the helicopter sound. I had a box with 2 solobaric 12's (old school ones) in a box that had a seperate chamber for each sub. I had an air leak on the back panel and it caused both subs to just "brbrbrbrbrbrb" like hell. Did it only when the volume was up high. That's the only reason why I thought that may be his problem.

Mish

PostGrungeJunky

mish...thanx sooo much for being so thorough. however, this doesn't change too much of what u said but i am running ONE sub to the bridged ch 3/4 of my amp. in other words, it's a SINGLE 2 ohm rated dvc sub wired in a series to those 2 channels making 4 omhs at 150w. haha i accidentily plurified my wording in my original post, kinda like how ppl say "headerS" instead of header for our 4 bangers. haha.

i'll check for leaks right away, in fact, come to think of it, my IDQ came with 4 qtr pieces of foamy gasket? stuff...it's still in the box!!! should i goto my installer and tell him to stick thoses pieces on? how crucial is that gasket?

** oh i almost forgot, i have a 4ch amp so i have 2 separate gain pots for each pair of channels. when setting my gain, they both need to be the same? er? my deck 4v preouts...approx where should my gain be set at? or does it all depend?