The software does not limit the response to 40Hz. There is a high-pass filter at 15Hz to protect the driver, but that doesn't limit bass in any meaningful way.
Let me explain a bit. What a low-pass filter does is reduce the output of the sub *above* a certain knee frequency, with a certain slope. So, for a low-pass filter of 40Hz with a 12db per octave slope, that means that frequencies at 40Hz and *below* will be passed at full output, but *above* 40Hz the output will be reduced such that by 80Hz the output is down 12db relative to 40Hz.
A high-pass filter does the converse. A high-pass filter at 40Hz with a 12db per octave slope means that frequencies *above* 40Hz are passed at full output, but frequencies below 40Hz are reduced such that by 20Hz the output is down by 12db relative to 40Hz.
Frankly, I think the person looking to set his low-pass filter to 40Hz is being silly. The advantage of using a Velodyne sub is the sophisticated equalization available to smooth the bass response, and the ability to place the sub for optimum bass response in the bottom four octaves, allowing you to place the mains for best imaging without regard for bass. By limiting the sub to bottom-most octave you'll hardly ever get any advantage from it, unless you use it only for home theater and watch action movies. For music, and depending on the system and room, an 80-120Hz low-pass filter, with proper equalization (meaning cuts) to lop off peaks, makes much more sense. I have Revel Salon 2s and use a 120Hz low-pass filter at 12db/octave. The sub really fills in a suck-out my room causes centered at about 100Hz.
I know that many disagree, but IMHO, Irv got it 100% right. To get the maximum benefit, the sub should be crossed in high enough to address room issues. IME, that usually means somewhere north (often well north, depending on the room) of 70hz.
I have other issues with the Velo software but the low pass range isn't among them. As to the confusion re: low pass filters....
It may be easier to think of them as "high cut" filters, cutting the high frequency end of the sub's output.
I agree with previous posters. I don't know why someone would buy a sub that is good to 15 Hz, and then set its low pass filter to the lower 3 dB cutoff frequency of 15 Hz. That makes no sense. Its like buying an amplifier good for 20 Hz to 20 KHz, then feeding it through a low pass filter at 20 Hz. You are using the product well out of its intended design range.
The implication is that the full range speakers go down to 15 Hz already, so why do you need a sub? If you need reinforcement well below 15 hz, you don't buy a product that is good only to 15 Hz.
I think Velodyne's design criteria are fine. A minimum low pass crossover point within a octave or so of the lower cutoff frequency of 15 Hz is sufficient.
You guys are totally missing the point. The flexibility of high-end Full-range speakers that go down to 17hz is totally useless if in order to use the sub, you have to cross it at 40hz. What if I want my speakers to take it to 30 hz and then let the sub kick in? Can no longer do that with this software. I would much rather listen to the higher-quality of my main speakers than the sub in 2-channel; movies are a different story.
I would never want to set the sub's low-cross at 15hz - that's totally ridiculous. But 25-35hz would not be out of the question, depending upon the music. I am also aware of the many ways the software can balance the room, etc. That's not, and never was my point. The limit of 40hz low pass was my point. I have since figured out a work-around with the help of a Velo senior VP. End of angst. Life is good. :-)
No, Fplanner2010, you're misread my post.
The 15Hz filter under discussion was not, as you say, the "low-cross" point. I was discussing the 15Hz high-pass filter that Velodyne makes mandatory in the DD+ line. Below 15Hz you get a roll-off whether you want it or not. You can only choose the slope. No one was discussing a low-pass filter at 15Hz.
And the OP misunderstood your post, on some other thread apparently, thinking that your complaint about a 40Hz lower limit on the low-pass knee frequency was really a complaint that the sub would not have output below 40Hz. I was just attempting to explain that wasn't the case.
As for your thinking that a 25-25Hz low-pass frequency is a good thing, well, every room is different, but I still think that is probably a poor choice. On the hand, it's your system and you can do as you please, and if a 35Hz low pass frequency makes you happy, who am I to question it?
You DID call me silly, so I responded. Its not that 25-35hz low pass is necessarily a good thing. As you point out, it is totally system, room, music and preference dependent. When I had this flexibility, I used it. With my newer and improved DD+, I am unable to. That didn't seem like "progress" to me, although from talking to the higher-ups I now understand why they HAD to do this. turns out it wasn't as arbitrary as it originally seemed.
Yes, I did call you silly. I think using a sub for less than an octave is very likely not using it to best advantage. Have you measured your room's bass response at your listening position?
Yes I have, as have others.
A very big THANK YOU to all of you that have posted to this thread. Your responses really cleared up my understanding as to how subs work in a 2-channel system.
Just a question re: measurements at the listening position:
Did you not get superior measurements with the sub crossed higher?
I've measured a dozen plus systems in a half dozen rooms and - with the subs crossed above 70hz - have gotten MUCH better measured results 100% of the time. Obvious exclusion: if there's full range room EQ (Audyssey, etc), the comparison is moot.
I completely understand if you prefer the sound of the system that produced worse measurements (personal preference trumps measurements, IMO), but I'm really shocked that you've gotten relatively decent results when the subs are crossed too low to address the bottom 2 octaves. I have never seen anything like that.
So are other people when they come into my room, including Albert VS several years ago. The room is 19x20, has sloping ceilings left to right from 13' down to 8', and many openings on 1 side, so its impossible to pressurize properly.
I have Audyssey'd (new word?) the room, wrote down the numbers and am close to where I want to be. There are a number of room limitations, as it is my living room, complete with big dogs, etc. The results, all-in-all, are pretty good. The numbers are really pretty meaningless in my situation, since the open side leads into the rest of the house. So, I do the best I can and adjust the crossover to where it works the best for my room.
I trust my ears - I've had them a long time... :-) thanks for your input.
In the immortal words of Daniel von Recklinghausen, if it measures good and sounds bad, it is bad.
If it measures bad and sounds good, you've measured the wrong things. Just a thought... :-)
being a current dd12 owner, glad i didn't wait for the plus line release. i use my mains full range and only let the sub do some "back fill". a little added punch is all i was looking for and this set up does exactly that.
from what it sounds like, the new plus line wouldn't let me do that. after spending over a month tinkering with the dd12's settings, going full range with my mains sounded best. too bad velodyne doesn't agree with me (and they've never even heard it ! =) )