Velodyne HGS-15 vs. any other sub?

[Sheep]

Actually, if test tones were used to output 100db at all frequencies (with an 80 hz crossover point) and a 12 db/oct slope is used the signal would still be at 94db at 120hz.

If a 24db oct slope is used (@80hz) it is still only -12db below the fundamental signal or 88db at 120hz.

If distortion is at an audible 10% it could probably still be heard at 120hz.

Thank you.

SheepStar

 

[edonsmith]

I had a HGS15 and WOW what a huge pounding sub that was. You will not be sorry with it

Don

 

[dobyblue]

If distortion is at an audible 10% it could probably still be heard at 120hz.

Distortion on the Sig is at 3.5% at 100dB with no crossover as shown by the graph that SheepStar posted.

 

[annunaki]

The 100db number I used was for example. Because crossovers are not brick wall filters, the distortion could still be audible if the input signal (at said frequency) was loud enough (would depend on crossover setting and slope). For this sub I would reccommend a crossover point of 60hz with a 24db/oct. low pass filter to make sure nothing carries over.

 

[annunaki]

In any case, the distortion on that woofer system is high, even at 100-105 db. Based on the way the distortion curve looks, I would say they should re-do the driver itself. It seems to be behaving the way a typical 'run of the mill' driver behaves. With linear motor designs so prevalent now, I am shocked one was not used, especially at that price point. I would think using a servo design with a linear motor system should result in thd under 3% over the entire usable range.

Look at the distortion figures on SVS woofers in that price range and they do not use a servo.

 

[dobyblue]

Servo - 40HZ/100dB = 1%
PB12+2 - 40HZ/100dB = 1%
DD15 - 40Hz/100dB = 1.5%

Servo - 30HZ/100dB = 3%
PB12+2 - 30HZ/100dB = 4%
DD15 - 30Hz/100dB = 2.5%

Servo - 20HZ/100dB = 5.5%
PB12+2 - 20HZ/100dB = 14.5%
DD15 - 20Hz/100dB = 9.5%

Servo - 40HZ/105dB = 1.5%
PB12+2 - 40HZ/105dB = 1.5%
DD15 - 40Hz/105dB = 2.25%

Servo - 30HZ/105dB = 3%
PB12+2 - 30HZ/105dB = 7.5%
DD15 - 30Hz/105dB = 3%

Servo - 20HZ/105dB = 7%
PB12+2 - 20HZ/105dB = 30%
DD15 - 20Hz/105dB = 13.5%

I understand what you're saying for the distortion in the higher end and your crossever recommendation is a good one, but all in all the Servo is definitely impressive in the lower end. I'd love to see the charts for the PB Ultra2.

 

[Sheep]

You have to consider the fact that the SVS was in 25Hs tuning, and will have lower THD ratings then that in 20Hz and 16hz tunings.

SheepStar

 

[annunaki]

Sheep is quite right. When a subwoofer (or any woofer for that matter) plays below the tuning frequency of the enclosure, distortion increases very rapidly. The woofer begins to lose control as the enclosure loses compliance and can begin non-linear behavior.

 

[xcjago]

Actually, if test tones were used to output 100db at all frequencies (with an 80 hz crossover point) and a 12 db/oct slope is used the signal would still be at 94db at 120hz.

If a 24db oct slope is used (@80hz) it is still only -12db below the fundamental signal or 88db at 120hz.

If distortion is at an audible 10% it could probably still be heard at 120hz.

Well let's see. If a sub outputs 100db at all fequencies, then yes, it's output at 120hz will be 94dB. If THD is 10%, that means the sum of the harmonics is approximately 20dB below the fundamental. So that means the sum of the harmonics is a total of 26dB below the fundamental. Not to mention that your main speakers will have an output of 100dB at 120hz which will increase the difference even more. You are probably looking at around 30dB difference between total output and THD at 120hz.

Now looking at the two graphs again, we see that the original servo maxes out at about 95dB across the board. That is fairly low output. At 120hz, it does have a nice 1% THD.

Looking at the newer servo, it actually hits 95dB at 120hz with about 2% THD. At 97dB it's at 3% THD. Even at 100dB, THD is still less than 5% THD. Remember, the original servo cannot even hit 100dB at any frequency.

Now, 5% THD means the THD is about 25dB below the fundamental. Therefore we are talking about a total difference of close to 35dB between the fundamental and the harmonic at 120hz. Since every 10dB increase is perceived as double the volume, the fundamental is around eight times louder than the THD. Trust me, it will not be audible.

 

[annunaki]

Very good points. A different angle than I was thinking of.