Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 Which Army personnel doesn't? ;D ;D ;D Heheheh... got... some of e boys in CMPB lor. Used to work with some... Phil
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 If Phil relocates his sub, he might go deaf ;D Phil, We still don't know exactly what happened i.e., why was your sub bottoming out so much without the BFD and what did you do to prevent it from bottoming out ??? My understanding… The BO was caused by high gain on the SVS, high volume at the processor & very aggressive response by the SVS. We tune down the gain to 12 o’clock & use the BFD to scale down the aggressiveness of the SVS. I did a quick check on “The incredilbles” & found out that it only comes with DD so the DTS track is most probably a bootleg version or boasted DD track. That’s why I BO the SVS again after all the tuning. Nevertheless, I think its about time to tune down my volume.. never expect myself listening at 80dB & above most of the time. Too damn loud & not healthy for my ears. Phil
wind30 Posted January 11, 2005 Posted January 11, 2005 isn't such frequent BO bad for the sub? I set my sub at 9 o'clock :) The SPL meter cannot tell distortion but I think if you don't calibrate at insane levels, it should be pretty ok. Unless you have a faulty SVS to begin with. Can room modes introduce distortion?? Cannot right? it can only amplify the harmonics... mmm... that makes it a little more complicated.... if you have a peak of 10 db at 40 hertz, although you killed it using the BFD, it will still manifest itself as harmonics of maybe 20 hertz... Jag do you know from experience which is the strongest harmonic? 2nd, 3rd ?? now it makes me curious on my distortion levels on my SVS sub. We should organise a "time share" scheme for a calibration setup :) :) which can measure freq response.
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 isn't such frequent BO bad for the sub? I set my sub at 9 o'clock :) The SPL meter cannot tell distortion but I think if you don't calibrate at insane levels, it should be pretty ok. Unless you have a faulty SVS to begin with. Can room modes introduce distortion?? Cannot right? it can only amplify the harmonics... mmm... that makes it a little more complicated.... if you have a peak of 10 db at 40 hertz, although you killed it using the BFD, it will still manifest itself as harmonics of maybe 20 hertz... Jag do you know from experience which is the strongest harmonic? 2nd, 3rd ?? now it makes me curious on my distortion levels on my SVS sub. We should organise a "time share" scheme for a calibration setup :) :) which can measure freq response. Yup.. its definitely unhealthy for the sub. The gain on the sub is not a definite indication of the volume you are pumping out. It also depends on the gain from the processor/receiver. What I have learnt yesterday is our ears are less sensitive to low end frequency & we will need to boast up the lower end to equalised the response for a “virtual” flat response for our ears. “Virtual” because it sounds flat but actually sloping from the frequency analyser. I actually prefer the aggressive curve when listening to a couple of songs. I got a feeling your response is either flatter or not even out at the low end. For all you know, you could be measuring other harmonics (or distortion as defined by Jag) of the intended test tone. This is where the limitation of the SPL meter comes into the picture. Phil
Jag Posted January 11, 2005 Posted January 11, 2005 Yes frequenct BOs are bad for sub. But luckily, the guys at SVS designed the driver to be reliable despite multiple BOs. Thats the sort of attention to details that SVS puts into the design of their subs. Of course, its not a ticket to bottom-out the sub frequently. Room modes do not introduce distortion. However, when things start rattling in the room, those rattles contribute to noise and distortion. Room modes can amplify and well as attenuate distortion. if you have a peak of 10 db at 40 hertz, although you killed it using the BFD, it will still manifest itself as harmonics of maybe 20 hertz... If the sub is distorting so badly in the first place, no amount of room acoustic panels or EQing will help. No point correcting a hopelessly distorted sub. From my experience, the 2nd harmonic is always the strongest. However, the room can affect the harmonic's power. Eg, a sub distorting 20hz will produce 40hz, 60hz, 80hz etc tone. But since some rooms modes amplify 60hz more than 40hz, the 60hz can be stronger than the 40hz. Its very room depedant that decides which harmonic will be stronger and which is weaker. Ok,almost ready to post phil's calibrating session.
wind30 Posted January 11, 2005 Posted January 11, 2005 considering my room mode as a 13 db peak at 45 hertz. It will make a 5% harmonic at that frequency sound like a 100% harmonic right? my room mode is the strongest at 45 hertz. second is the 64 hertz. 45 hertz is not so problematic as it will only manifest itself at 22.5 hertz and 15 hertz. Maybe that is why I have a huge bump at around 20-22 hertz. This problem cannot be solved by EQ right? So basically I am stuck with a heavily distorted 20-22 hertz. :( and I think most people are stuck with that right?
Jag Posted January 11, 2005 Posted January 11, 2005 45 hertz is not so problematic as it will only manifest itself at 22.5 hertz and 15 hertz. Maybe that is why I have a huge bump at around 20-22 hertz. This problem cannot be solved by EQ right? So basically I am stuck with a heavily distorted 20-22 hertz. :( and I think most people are stuck with that right? Well, without a detailed analysis, there is no way of really making sure that your 20-22hz is as heavily distorted as you make it out to be.
wind30 Posted January 11, 2005 Posted January 11, 2005 Jag, how you do your measurements? I assume you have a band limited test tone at different freq to use as source. Then you measure the gain at the test tone freq and ignore the contributions from the harmonics? but I see the limitations of the BFD. It cannot do anything about distortion. Basically if you position has a huge peak to begin with, like +15db, the tone for the that freq/2 is probably screwed up badly due to the first harmonic being amplified. SO I guess placement and treatment is always better than EQ.
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 Not jag but since he is not around.. maybe I can share with you what he did. He uses his test CD to generate a wideband test tone, which covers the whole frequency spectrum. He uses TrueRTA to monitor on his notebook the real time response from the sub and/or speaker. Then uses the graph on screen to setup the BFD to smoothen the curve & integrate with the rest of the channel. He good thing about this is he is looking at the collective response at real time instead of individual test tone. In another words he is looking at the big picture all the time. E.g. if the harmonics is causing a peak or dip, he will use the BFD to compensate accordingly. Phil
tsammyc Posted January 11, 2005 Posted January 11, 2005 Phil are you saying then that you actually had to reduce the output at 16-20Hz with the BFD to prevent BO? One thought is that if you listen at normal and not ear drum shattering volumes that having the SVS go close to BO may sound better. Just never push the volume that hard....
Jag Posted January 11, 2005 Posted January 11, 2005 On the contrary, his aggressiveness of the slope was not altered much. Its the calibration effort from the source to the speaker that improved things. After my calibration, SVS gain knob went from 1pm to 12o'clock. Processor sub level increased 12dB :o. (Phil, can confirm? Combine both the DD bass menu increments and speaker level menu increments.) Of course, his initial curve was way way too aggressive for his good. Phil will remember how I explain the proper slope should be.
Jag Posted January 11, 2005 Posted January 11, 2005 Not jag but since he is not around.. maybe I can share with you what he did. He uses his test CD to generate a wideband test tone, which covers the whole frequency spectrum. He uses TrueRTA to monitor on his notebook the real time response from the sub and/or speaker. Then uses the graph on screen to setup the BFD to smoothen the curve & integrate with the rest of the channel. He good thing about this is he is looking at the collective response at real time instead of individual test tone. In another words he is looking at the big picture all the time. E.g. if the harmonics is causing a peak or dip, he will use the BFD to compensate accordingly. Phil And I also can see if the sub is distorting on not just by looking at the real-time updating freq response.
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 After my calibration, SVS gain knob went from 1pm to 12o'clock. Processor sub level increased 12dB :o. (Phil, can confirm? Combine both the DD bass menu increments and speaker level menu increments.) No lar.. only 6dB lar. I do remember u up the sub gain to max at the channel balance menu but after u left.. I went in & take a peek & its set to 0. Phil
wind30 Posted January 11, 2005 Posted January 11, 2005 I think I figured a way on how to measure my distortion :) put in a pure sine wave at 20 hertz. measure the SPL. Then put in a filter that kill ALL signal at 40, 60, 80 hertz then measure SPL again :) any comments on this poor man's way of measuring distortion? :)
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 Hi Jag Can you post the response curve of the front? I remember they look better & does not have that nasty peak from the center. BTW, now I got an idea... maybe I can use the right channel to EQ the center!! How about that?? Then I can use another setting for REL & center... then maybe 1 with dual sub! hahahaa... Input 1 LFE Output 1 a. 1/4 phono -> SVS b Balance -> REL Input2 Center Output2 Center Phil
Jag Posted January 11, 2005 Posted January 11, 2005 Hi Jag Can you post the response curve of the front? I remember they look better & does not have that nasty peak from the center. BTW, now I got an idea... maybe I can use the right channel to EQ the center!! How about that?? Then I can use another setting for REL & center... then maybe 1 with dual sub! hahahaa... Input 1 LFE Output 1 a. 1/4 phono -> SVS b Balance -> REL Input2 Center Output2 Center Phil Nah lah. Don't use the DSP1124 to equalise any mains. If you want to EQ the mains, use the DEQ2496. The BFD ADC/DAC samples at 46Khz. Its just a bit better than CD, but worse than Dolby digital. If want to EQ mains, the DEQ2496 is a much better alternative. It samples at 96Khz 24bits, far far superior than the DSP1124.
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 Nah lah. Don't use the DSP1124 to equalise any mains. If you want to EQ the mains, use the DEQ2496. The BFD ADC/DAC samples at 46Khz. Its just a bit better than CD, but worse than Dolby digital. If want to EQ mains, the DEQ2496 is a much better alternative. It samples at 96Khz 24bits, far far superior than the DSP1124. DUH! Phil
Phil1624705739 Posted January 11, 2005 Posted January 11, 2005 SO you wanna sell the extra BFD? ;) Nope.. don't think I wanna go to that kind of extend! Phil
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