# Lots of distortion what to do???



## Guest (Jan 27, 2007)

so i have my measurements in my thread my first real measurements... so i was watching the movie pulse which i was getting a ton of distortion from the sub... sounded so horrible it was like puttering i guess not exactly sure how to discribe it... but almost like instead of hitting the sub was just not holding the note... 

the sub is in the corner of the room and its a nht 12 inch... i have the boundary eq set to 0 and the phase set to zero... i had the db knob up to about 3/4 or 2/3 and even when i lowered it to about half it was still doing it... I order a FBQ 2496 so i don't know if this will fix it or what exactly is causing this awful bass... thanks...


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## Sonnie (Apr 11, 2006)

I think this might fit better in Home Audio Subwoofers.

Have you noticed the distortion before now and have you tried another DVD?


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## Guest (Jan 27, 2007)

no i haven't noticed the distortion before but i just moved the sub into the corner before it was closer to the center of the front wall... i did play a movie just earlier that sounded fine...

pulse was an hd dvd playing true hd out of a XA2 toshiba through the analog outs... i read somewhere that the pulse hd dvd has some good LFE at 25-30hz so that really shouldn't make the sub flap like that... while the other movie that sounded fine was employee of the month playing out of the coaxial output from the toshiba...

is this maybe the flapping woofer problem where it moves in and out a lot but doesn't produce any usable sound output???

i have a nht 12inch sub and was just wondering if maybe itz trying to reproduce 20hz or lower and can't do that so it flaps... i order a FBQ 2496 so i'm wondering if i can filter out those low basses or what else could i do???

also what is a bass trap??? where would u find one???
also what does it sound like when ur sub is clipping???


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## brucek (Apr 11, 2006)

> is this maybe the flapping woofer problem where it moves in and out a lot but doesn't produce any usable sound output???


If your sub doesn't produce any output down low then it's unlikely it is making a distorted sound from receiving those low frequencies. 

If I look at your subs response (had to go to the other section to get it), I see your sub drops off fairly quick below 25Hz. 

So I don't really think any very low frequencies <25Hz are causing distortion. You can use REW to produce sine waves at any frequency and you can move the frequencies around and see if you can reproduce the problem.












brucek


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## Guest (Jan 27, 2007)

i think itz making the flapping distortion during a low frequency moment in the movie because they are walking into a room and itz like a pulsing sound and it starts doing it...


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## Guest (Jan 27, 2007)

I played around with batman begins also in true hd and really cranked it up in scenes where there was loud explosions which may not be as low a frequency but the sub sounded fine... I don't know if itz the disk or what i also tried playing pulse instead of through the analogs, i played it through the coaxial and it still was doing the flapping distorting thing... so i'm not sure but maybe it is just the pulse hd-dvd...

is there any dvds u could recomend me that have very low bass???


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## Otto (May 18, 2006)

You can push some tones through it using REW. Just start with the volume low and increase it slowly. That way you will be able to control the frequency and amplitude till you recreate the problem.


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## Guest (Jan 27, 2007)

i posted over on avsforum and got some responses from people having the same problem... and this is what one guy said is probably happening...

its probably the sub playing below tunning frequency and unloading and then bottoming out on my sub it plays perfectly fine i jsut tried it with optical and it plays fine also.

so i'm assume that my sub just cant' handle the lfe itz getting... so i was wandering if the only way to fix it would be get a sub that extends lower HZ like low 20s and below ... 

what type of subs can handle that... it just sucks cause i get a real good deal on nht subs...


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## Otto (May 18, 2006)

frockc said:


> so i was wandering if the only way to fix it would be get a sub that extends lower HZ like low 20s and below


DIY, SVS, HSU, Velodyne. I'm sure there are others, but I'd start my research there...


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## srckkmack (Feb 10, 2007)

You may also be overdriving the sub. Many of us like to hear more bass so we boost the receiver's level for the bass output and may also set the back of the subwoofer so it runs a few dB hot. Do you also do this? This combination may cause your sub to distort as it gets to or exceeds its limits.


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## Guest (Feb 12, 2007)

I run my sub at the same level as my speakers 75db... i think itz because my room is just way to big for the sub... itz only a 250 watt amp 12inch sub... and my room is probalby 4500 cubic feet becaues the living room is open to the dinning room and kitchen...


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## srckkmack (Feb 10, 2007)

My room is probably about the same size as yours (20x20 with cathedral ceiling and open to the dining area of the kitchen) and I have a 125W 12" sub too (M&K V125). Last month my sub sounded horrible after I felt I was not getting enough bass. I turned up the bass level in the receiver; this increases the signal on the sub-out to the sub. The bass did not seem to get any louder. So I turned up the gain on the back of the sub. The bass still did not sound good. I ended up recalibrating my system using my receiver's auto-calibration (Ypao) and set it for a flat response. This made a big difference.

I think I may have tried to drive the sub too hard and either the input signal was too high (receiver setting) causing the sub-out signal to be distorted or clipped on the sub input, or the combination of input signal and sub gain was driving the sub's speaker to its limits and distorting. I thought this may also be happening to you.


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## salvasol (Oct 31, 2006)

srckkmack said:


> ...my sub sounded horrible after I felt I was not getting enough bass. I turned up the bass level in the receiver; this increases the signal on the sub-out to the sub. The bass did not seem to get any louder. So I turned up the gain on the back of the sub....I think I may have tried to drive the sub too hard and either the input signal was too high (receiver setting) causing the sub-out signal to be distorted or clipped on the sub input, or the combination of input signal and sub gain was driving the sub's speaker to its limits and distorting. I thought this may also be happening to you.


Quick question: Did you have the distortion, horrible sound, etc. all the time or just during some passages in the movies????  

Sometimes I have noticed this in my sub ... I'm not sure if I'm making the same mistake (bass level, gain response, etc. to high) .... in my case it happens during some movies, not all the time.:yes: :yes: :yes: 

(I know, that I need to get the REW and a BFD raying: ....to solve this problems , in the meantime I'm looking for temporary solutions .....)


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## bobgpsr (Apr 20, 2006)

salvasol said:


> Sometimes I have noticed this in my sub ... I'm not sure if I'm making the same mistake (bass level, gain response, etc. to high) .... in my case it happens during some movies, not all the time. (I know, that I need to get the REW and a BFD raying: ....to solve this problems , in the meantime I'm looking for temporary solutions .....)


Sorry there really aren't any -- other than turning down your sub's gain or adding more subwoofers. 

A 25 Hz or so high pass filter (bit of a bother to gen up) can help prevent bottoming. This type of (selectable freq) high pass filter is built into SVS subs and are selected by the various tuning options switch (e.g. 16, 20, 25 Hz) on the SVS plate amps to be used along with the port plugs.


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## srckkmack (Feb 10, 2007)

salvasol said:


> Quick question: Did you have the distortion, horrible sound, etc. all the time or just during some passages in the movies????


It didn't make horrible noises... it was more like the bass was set low (ie, quiet) and the sub was not making the normal rhythmic beats you'd expect to hear. I thought the sub or the receiver's sub output was not working. After auto-recalibrating, all was better. When I checked the receiver's subwoofer level setting, I noticed it was set well below the mid setting (about the 25% point). That's when I realized I may have been over-driving the sub because I had it previously set to about the 75% point.


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## Guest (Feb 19, 2007)

well i decided to buy a fathom 113... after all the amazing reviews and listening to a 112 at the store i had to purchase it... yes my sub was bottoming out due to it only being a 12inch one port 250 watt amp in such a large room... many other people have the same bottoming out with other subs on that pulse movie... its flapping and chuffing sounds awful...


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