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[Gordon Brinton]

I've been reading threads on other forums about protection from over excursion due to low end rumble and pops. Now it's got me biting my nails about my own subs.

I have a new pair of Yamaha DSR118W that I use for small to medium club rock and variety bands. I usually baby them, but on occasion, I hit them pretty hard. The built-in DSP is fairly decent. It crosses them over at 120Hz and protects them with general limiting, but I can't find anything in the literature about subsonic filtering.

I do make use of the high-pass filters (3rd order BW) on the input channels of my digital mixer, but there are none on the output channels and I don't have any racked speaker processing. I currently have every input channel manually set at 40Hz, but I don't know if that is enough protection throughout the entire system. Doesn't the system electronics generate a bit of lower harmonic noise?

I guess my question is...
Should I rely on the input filters alone or invest in a drive rack just for the HPF feature? I've recently read about other guys doing just that.  (BTW, I do have a show coming up next month providing a DJ rig for a wedding reception. I'll use a tiny analog mixer that only has HPF at 80Hz. Yikes!)

[David Morison]

I've been reading threads on other forums about protection from over excursion due to low end rumble and pops. Now it's got me biting my nails about my own subs.

I have a new pair of Yamaha DSR118W that I use for small to medium club rock and variety bands. I usually baby them, but on occasion, I hit them pretty hard. The built-in DSP is fairly decent. It crosses them over at 120Hz and protects them with general limiting, but I can't find anything in the literature about subsonic filtering.

It would be monumentally incompetent of Yamaha not to include an HPF in this day & age, so I'd be 99% sure it has one and they just haven't been explicit about it in the manual.

The frequency response graph suggests it drops from about -8dB @ 40Hz to about -22dB at 30 Hz, which is far steeper than the 24dB/Octave you'd expect from a normal vented box, so that's broadly consistent with it having an HPF already as well.

In short, don't sweat it.

Cheers,
David.

[Mike Caldwell]

I would hope/think that Yamaha includes a HPF in the DSP processing!

As for the mixers inputs channel HPF, having them all set
in the 30 to 40 range is not bad but many channels can benefit from having a higher HPF filter setting, vocals, hi hat, overheads, maybe a rack tom or two, acoustic and electric guitar, maybe even sometimes the bass guitar!

[Samuel Rees]

This surely is done in the DSP - that's what it is for. If it wasn't users would be breaking these things at an unusual rate and someone would notice, I imagine.

[John Rutirasiri]

(BTW, I do have a show coming up next month providing a DJ rig for a wedding reception. I'll use a tiny analog mixer that only has HPF at 80Hz. Yikes!)

That 80Hz HPF is the "low cut" for the mic input.  You don't want that engaged for the playback channels on the mixer -- it will just eat up all the low freq.

For me, the reason to have an external speaker processor/DSP, rather than relying on the powered sub's built-in crossover/DSP,  is so I can adjust the LPF and HPF freq. It's nice that Yamaha picked 120Hz -- a good number, but depending on my top cabinets (e.g. a double 15), I may not need the subs to punch all the way to 120Hz or 150Hz range.  100Hz may be more appropriate. 

I almost always run aux-fed subs to be able to control the subwoofer level independent, but in the case where I'm not doing aux-fed sub, a driverack gives me the ability to adjust the sub level without going to the back of the subwoofer.

As you said regarding subsonic/infrasonic filter, you may not need your sub to work down to 30Hz or whatever the DSR118 uses.  Maybe 50Hz is all you need for a particular show.  I like to be able to brickwall my subs with 48dB/octave HPF to help protect over-excursion, in addition to limiting in the amp.  Brick-walling like that could cause significant phase shift, but hell it's EDM, not Yanni.

Not sure what you mean by "Doesn't the system electronics generate a bit of lower harmonic noise?"  Maybe you meant A/D and D/A conversion noise if you went into an external processor first?  Sure -- unless you keep it all in the digital domain (the DSR118 doesn't have digital input), adding anything that does A/D and D/A conversion will add noise.  And delay.  Delay in this case is (a subwoofer) is insignificant.

I would only get a DSP that has 48dB/octave slopes (most these days do) and runs 96Khz (not getting into that "you can't hear the difference between 48KHz and 96KHz" debate.)  In the Driverack family, that used to only be the 4800/4820, but maybe the new Venu360 runs natively at 96KHz, I'm not sure.

Best,
John R.

[Gordon Brinton]

Just to be sure about whether or not there is a built-in high-pass filter, I took it upon myself to do some experimenting. I hooked up my studio computer to one of my Yamaha DSR118W subs and played some low frequency tones. The S/PDIF output from the computer goes through a Benchmark DAC1 which has very stable frequency response. That is, I can usually hear the studio sub fairly well at 20Hz. BTW, this took place in a very well treated studio control room. Luckily, modes and nulls have been minimal here.

I started with a baseline tone of 80Hz just to set the level. I turned up the DAC output so that the Yamaha sub was loud enough to vibrate the whole building, but not really breaking any windows. I would guess that it was probably around 90 to 100dB. I didn't change the level from that point on. (I do have a dB meter, but I've read that they are not accurate below about 200 Hz. So, I didn't bother using it.)

I then set the tone frequency to 60Hz and the volume went down a bit, but was still fairly prominent.
At 50Hz, I could notice a more significant drop in level. (I would guess maybe 80dB or less)
At 40Hz, it was low enough to talk over, but could still be heard.
At 35Hz, it was becoming closer to being inaudible. It was still there, but not very loud even with my head in front of the speaker cone.
At 30 Hz and below, I was not sure if I was actually hearing the tone or if it was my imagination. I couldn't see much, if any, cone movement even with a flashlight shining down along the cone from the surround to the cap.

I continued to lower the tones to 25, 20, 10, and then 5 Hz. Again, there was no noticeable cone movement for any of them.

Furthermore, just to rule out the possibility that the DAC was the cause of the level drop; I pulled the XLR cable out of the sub and plugged it straight into channel 1 of my QU-24 mixer. I turned on PFL, (and disabled HPF,) and watched the meters while I went through the tones again. They stayed at full meter all the way down to 2 Hz. Ok, it did finally lose about 6 dB at 1 Hz. Not bad at all. My conclusion was that the low tones were reaching the sub.

I also swept upward with the same frequency test back on the sub again. As expected, it gradually lost level between 120 and 500hz.

[Art Welter]

I would guess that it was probably around 90 to 100dB. I didn't change the level from that point on. (I do have a dB meter, but I've read that they are not accurate below about 200 Hz. So, I didn't bother using it.)

I then set the tone frequency to 60Hz and the volume went down a bit, but was still fairly prominent.
At 50Hz, I could notice a more significant drop in level. (I would guess maybe 80dB or less)
At 40Hz, it was low enough to talk over, but could still be heard.
At 35Hz, it was becoming closer to being inaudible. It was still there, but not very loud even with my head in front of the speaker cone.
At 30 Hz and below, I was not sure if I was actually hearing the tone or if it was my imagination. I couldn't see much, if any, cone movement even with a flashlight shining down along the cone from the surround to the cap.

I continued to lower the tones to 25, 20, 10, and then 5 Hz. Again, there was no noticeable cone movement for any of them.

I also swept upward with the same frequency test back on the sub again. As expected, it gradually lost level between 120 and 500hz.

The DSR118W is rated at -3 at 50 Hz and 110 Hz, -10 at 40 and 130 Hz. The upper range drop off is consistent with a 24 dB per octave filter, and since you saw little cone movement below 50 Hz, your test confirmed the low filter is also likely 24 dB per octave at around 50 Hz.

The tuning frequency (Fb) can be determined by watching for the minimum cone  excursion, likely also to be right around 50 Hz. With the existing filter and Fb, the maximum excursion will probably be around 60 Hz.

[Gordon Brinton]

Right. The audible drop at 60 Hz could have merely been from a room null where I was standing. After all, it's a big sub in a small room.

Anyway, the test was indeed consistent with the amp having a HPF. Otherwise, if the lowest tones had been passing through the amp and actually reaching the driver, I think we would have seen at least some radical cone movement and waffling about as it tried to reproduce some of it. I saw none of that.

Thanks, guys, for the advice. I have learned to trust Yamaha's DSP from now on.

[Gordon Brinton]

I went back and did the tests again using the dB meter. I held it at about 2 feet in front of the speaker to try to eliminate as much of the room as possible. Not scientific, but here it is.

100 Hz = 105 dB
95 Hz
90 Hz = 107 dB
85 Hz
80 Hz = 107 dB
75 Hz
70 Hz = 104 dB
65 Hz = 103 dB
60 Hz = 104 dB
55 Hz = 105 dB
50 Hz = 101 dB
45 Hz = 97 dB
40 Hz = 93 dB
35 Hz = 87 dB
30 Hz = 77 dB
25 Hz = 64 dB
20 Hz = <60 dB (Out of range)

[Kyle Marriott]

Not to disparage your efforts and experimenting but they actually published a response plot for the DSR118W - it seems to be less easy to find now, so maybe they took it down due to people listening with their eyes before their ears and dismissing what works as an excellent sub in practice but plots not so great.




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[David Morison]

Not to disparage your efforts and experimenting but they actually published a response plot for the DSR118W - it seems to be less easy to find now, so maybe they took it down due to people listening with their eyes before their ears and dismissing what works as an excellent sub in practice but plots not so great.




Sent from my iPhone using Tapatalk

That's exactly what I was basing my comment off earlier, and it's still around.
http://www.yamahaproaudio.com/global/en/products/speakers/dsr_series/downloads.jsp then select the "DSR Series Frequency Response" pdf.
Like you say, not quite as easy to find as if they'd just chucked the graphs in the spec sheets or manuals like any sensible manufacturer...

[Gordon Brinton]

That's exactly what I was basing my comment off earlier, and it's still around.
http://www.yamahaproaudio.com/global/en/products/speakers/dsr_series/downloads.jsp then select the "DSR Series Frequency Response" pdf.
Like you say, not quite as easy to find as if they'd just chucked the graphs in the spec sheets or manuals like any sensible manufacturer...

Thanks. I hadn't seen that chart until you posted it. The graphs in the manual and brochures are for the top boxes.

I suppose that that chart is fairly close to what I got, (given they were each entirely different testing environments). The upper frequency roll-off doesn't look right though. The crossover point is 120 Hz. I don't know much about the FIR-X filtering, but if that were a Butterworth filter, the slope would only be -3 dB at the actual crossoxer point itself, (and -6 for a LR filter).

Oh well, either way, I did find what I wanted to know.

These little subs do sound great. Like Kyle said, they don't get the respect they deserve due to their lower wattage specs. Man, they are plenty loud and tight though, apparently because they have high driver sensitivity. I've used mine (2 single 18's) for several rock bands in small to medium size clubs and in every case so far, I've had more low end than I knew what to do with, (and I like to feel that kickdrum punching in the chest). They keep up with the DSR112 tops just fine. I may buy two more someday just for larger rooms.

[David Morison]

I suppose that that chart is fairly close to what I got, (given they were each entirely different testing environments). The upper frequency roll-off doesn't look right though. The crossover point is 120 Hz. I don't know much about the FIR-X filtering, but if that were a Butterworth filter, the slope would only be -3 dB at the actual crossoxer point itself, (and -6 for a LR filter).

Those would indeed be the corner points for the filter types, if you were just looking at the filter response on its own, or if the filter were applied to a perfectly flat speaker. Thing is though, we can clearly see there's a bit of a hump in the speaker's response that's going to skew everything, so I wouldn't worry about trying to second guess exactly how they've arraived at that nominal figure.

If they work for you with a nice smooth transition to your tops then you're all set - carry on enjoying them 

[Art Welter]

I don't know much about the FIR-X filtering, but if that were a Butterworth filter, the slope would only be -3 dB at the actual crossoxer point itself, (and -6 for a LR filter).

The DSR series top cabinets use FIR filters, but the sub uses analog filters.

FIR filters can flatten phase response, but the latency (time delay) required to flatten phase down to 50 Hz would be too much for live use.

[ProSoundWeb Community]