Classical music, 2-channel, and sub-woofers?

[jerryt]

thanks for the zapper tip, I'll check it out.

 

[wgscott]

I ordered one. I heard nothing for a couple of weeks. Not even an acknowlegement of the order. I was about to figure out how to cancel orders with Ebay when it appeared. It works fine, doesn't interfere with the sound quality on my Class D Audio amp, and I programmed it to use the same on/off button on remote as my Nova.

 

 

[crisnee]

Although in general I agree with the attitude of "no DSP," I think there is one (common) instance in which it works fairly to extremely well, depending on the user's circumstances; for taming resonances (narrow strong bumps in bass frequency response) that won't go away no matter where you move your sub(s). A severe or strong resonance or two can play absolute havoc with your sound and getting rid of it is definitely worth the price. It worked wonders for me.

 

On the other hand suckouts are no big deal (at least compared to resonances) and if that's the only problem you have in the bass you're in luck. Besides, they're not curable by eq. Missing a narrow frequency range in the bass is much less annoying than its opposite, IMO.

 

-Chris

 

[crisnee]

might want to read this.

 

It's part one of three of a very in depth look at setting up subs with your system (and why it's a good idea to do so, and do so meticulously). The other parts have not yet been published, but it will probably take anyone new to this game quite some time to become completely familiar with part 1.

 

-Chris

 

[wgscott]

I've come up with a few more questions:

 

1. Is the low-frequency limited by the diameter of the woofer speaker cone?

 

2. For speaker-level input, I have seen various options. One option, as with the BW PV1, is very thin wires that go from the amp to the sub. Another, as with some of the Velodyne subs, is both speaker-level input and speaker-level output, such that you go from the amp, to the sub, and then to the main speakers, and there is (presumably digital) crossover circuitry that takes out the lowest-frequency signal going into the main speakers. In the case of the former, is it also possible to attach the thin wires to the main speaker terminals, and thus have a signal that goes from the amp to the main speakers and then to the sub? In the case of the latter, is it better to avoid using the crossover, and have parallel connections to the speakers and the sub?

 

3. Are Class D (main) amps inherently incompatible with speaker-level wiring to a sub?

 

4. My main speakers are reported to have a response curve like that shown in green below:

 

 

If this is accurate, I'm not getting significant bass below 90Hz. The reported dip at 2kHz, however, isn't very significant in my own measurements, so I am not certain how worried to be... it seems to have a more gradual high-frequency rolloff, fwiw.

 

Maybe I need a few inverse-subs as well.

 

 

 

 

 

[Guest Caner]

First of all let me say that this is my first post despite being an avid follower of this forum for at least the past 2 years and by no means I am an expert or claim to have "golden ears". Please take my advice with a grain of salt.

 

With regards to OP though, till very recently I had a system that only included 2 Dali tower speakers (Helicon 400 MkII) a Cambridge Audio DacMagic, a NAD M3 and a squeezebox touch connected wirelessly to a NAS. I added 2 active Dynaudio Sub 250's to NAD M3's Pre Out2 terminals a year ago and the improvement was more than impressive. It needed some experimentation with the placement to get them in phase/insync with the Helicons and an SPL meter (cheap, bought from Radio Shack) and adjustments of Gain and Low Pass filter also helped with the process, but the end result was all worth it.

 

I think dual subwoofers, if well integrated to the main speakers, gives you more "bang for the buck" than most other investments in the chain. I would wholeheartedly reccomend this set up ("Dual" seems to be the magic word here and my experience is it makes the speaker placement and he integration process much more easier). But as I mentioned above I am no expert.

 

Best

Caner

 

 

 

[crisnee]

Yes the cone size definitely affects the depth of the bass, but it isn't the only thing. For instance cone sizes act differently in closed versus open (vented) systems. And more power will also allow a given size cone go deeper (particularly in closed systems), albeit usually with more distortion.

 

As to the last part, if you're system goes down to only about 85hz, you're missing alot. The fundamentals of the bottom octave (plus) of a double bass or bass guitar for instance. The whole foundation of a symphony orchestra.

 

I think a system needs to go to at least 40 hz. I don't really care about the extremely low stuff (below 30 hz) so I would aim for good response to 35 hz--if your funds are limited, lower if not.

 

For some reason I like the idea of smaller cones. 10" seems like a good size (all else being equal), but I then I'm not concerned with the extreme bass.

 

-Chris

 

[wgscott]

This would be for our living room, so if I get two of these things and they are close to the speakers, they by necessity will be "on display," so I don't want to trash the place. The speakers set me back $2K, which I know is chump change compared to most of what people here have, but hey, for me, that's a lotta money. (Oddly, I wouldn't think twice about spending that on a bicycle, and we have several that cost more than that, each.)

 

Keeping in mind this is still at the speculative stage, I started doing some background checks.

 

 

The Velodyne minivee seems to have a reasonable frequency response. The good: I could afford two at $527 each, i.e.,

http://www.garrett-smarthome.com/proddetail.php?prod=MINIVEE8

Less than 12" cube.

Class D amp is energy-efficient.

The bad: Ugly black boxes that will ensure my heterosexual interior design credentials are never called into question.

 

 

 

The B&W PV1 definitely looks cool, but there are mixed reports on how it sounds. At $1600 each, it seems excessive for something with half the Class D amp power of the ugly little black boxes. I think they are being discontinued.

 

 

The Rel Serie R are comparatively new Class D sub-bass systems. There are 3 in this series, ranging from $1200 to $2200 each, so getting two again will be a bit of a squeeze. Their website says to get one first, and then get a second if you really think you need it. But I kind of like the idea of stereo subs. This one seems to come off as the most conceptually rigorous sub for audio, and looks almost as cool as the PV1.

 

 

[wgscott]

One R-218 or two T-5s?

 

[Part-Time Audiophile]

I meant to throw this out there when I first saw this thread, but just plumb forgot:

 

http://www.soundoctor.com/whitepapers/subs.htm

 

Barry has done a lot of work with JL Audio on their home audio sub line up and has a lot of things to say about subs in general. I got referred to him by someone who was swearing up and down about how awesome his Magnepans sounded when crossed over around 80Hz into dual subs. Anyway, long story short -- there is a problem when using most subs, and that's delay.

 

Even when you set the phase to zero and put the subs on a plane with the speakers, the subs are still delayed -- and the more circuitry (EQ) on the sub, the worse that delay is. According to Barry, most commercial subs will add ~9ms of delay to any audio signal -- which is enough in most cases to completely throw the phase of the sub off, regardless of what it was actually set at. His solution? Set the phase to zero and use an off-board EQ setup to delay the mains by 9ms (to match the delay inherent in the subs) -- or move the subs 9 feet closer to the listener. And yes, sitting on them would be fine.

 

True? Who knows. Just more data to consider. The result, for me, was that as a result of all these conversations, I decided against adding an external crossover (which can only adds delay to the subs, worsening the problem).

 

And since I just wasn't interested in adding a unit that would only be capable of 24bit/96kHz A-D/D-A conversion (seems strange and silly to bother sending converted 192kHz -- or DSD, worse yet -- audio into yet a downstream device for another conversion at a lower resolution), I simply moved my subs closer. Works better than you'd think.

 

[wgscott]

I'm about 1/3 the way through reading the SoundDoctor essay. I picture this guy taking off his shoe and slamming it on the table while he screams at me.

 

[Part-Time Audiophile]

Group delay is info that's terrifically hard to find for most speakers. Don't tend to see it in the specs. Anyway, I've learned that many (most?) speakers also have a group delay, but it's closer to 5ms or less. Which means that, if this is all true, then you'll only need to move your subs ~4' closer (rather than 9') in order to maintain/match phase.

 

[Part-Time Audiophile]

Barry is a bit of a talker. Not so much a screamer, but definitely a storyteller. Don't call him unless you have an hour. Or two.

 

[wgscott]

If I understood it correctly, what he is saying makes perfect sense. I made a figure that I think might help clarify it (a picture is worth a thousand rants):

 

 

 

[Bob Stern]

I'm not sure, but I think Room EQ Wizard (free) can measure the difference in group delay between the subwoofer and the main speaker.

 

http://www.hometheatershack.com/roomeq/

 

[wgscott]

If I understood it correctly, what he is saying makes perfect sense. I made a figure that I think might help clarify it (a picture is worth a thousand rants):

 

 

You want what comes out of the sub to be in phase with the main speakers. I think what he is saying is that because of the circuitry in the sub, you will get a delay, so the signal will be out of phase (lagging) due to this delay. Figure 1 shows the hypothetical main signal in blue and the sub in red. Ideally, the red arrow should coincide with the blue arrow, but due to the delay, it doesn't line up.

 

Figure 2 shows what happens when you adjust the phase. You can move the red arrow only in one direction, because you cannot make the signal come out of the subwoofer any sooner than it normally does.

 

Figure 3 shows what happens when you adjust the phase more until you get near perfect phase alignment. The peaks now coincide (I staggered it slightly so you could see both sine waves). You cannot move the red arrow backward so that it aligns with the blue one, but you can move it further forward so it aligns with the purple one. When it aligns, the two signals are in phase, so you won't have any destructive interference. Unfortunately, there is a delay of once cycle relative to the main speaker's signal, and even if the waves are perfectly in phase, you cannot do anything about this, apart from putting in an equivalent delay for the main speakers, or move your subwoofer one wavelength closer to the listener.

 

[Bob Stern]

Bill:

 

Increasing the phase shift to 360 degrees only works at one frequency.

 

[wgscott]

I agree. I was just trying to make an illustration for what this guy was trying to say in his rant, and it is easier to show for one frequency. But of course the problem is you have the whole spectrum, so there is no easy way out of the problem. The only "proper" way to deal with it is to have the same delay for all the speakers.

 

[wgscott]

It looks as though the JL Audio subs don't have speaker-level inputs, and I wonder if using the pre-amp input and the crossover circuitry is the result of the delay?

 

[roark]

I have some basic questions about adding a sub and hoping to get some advice. I currently have a small Onkyo receiver and a pair of small bookshelf speakers alone. Would adding a small sub make a large difference in sound quality? Also, my receiver does have sub pre out but I am not sure if it works. If it did not or the receiver did not have one does it make a big difference if you connect a sub at speaker level? If you do it that way and adjust the crossover on the sub itself do you still lessen the load or impact on the receiver? I am not sure I am phrasing that right but I looked into adding a sub and one of the things mentioned was that besides more bass it would also help the bookshelf speakers perform at what they do best without having to deal with bass that the sub would handle. But even if I understand that roughly correctly I was not sure if you still get that benefit if connecting at speaker lever for sub.

 

Thanks.

 

[wgscott]

There are (at least) two options:

 

1. Hook up the sub via the sub pre-out or LFE out from your receiver, which is commonly done in HT setups. Then adjust the crossover circuitry in your receiver so that the main speakers don't get the lower frequencies, and route all that to the sub. This has the advantage of taking some load off the amp for those speakers, as the sub (normally) is active, i.e., it has its own amp. Adjusting the "crossover" for the main speakers may be as simple as setting them to "small", although many receivers allow you to pick a number. If you set it too high, you risk having a gap in the midrange and can spoil the stereo effect, and if you set it too low, you aren't doing much. So you have to optimize.

 

2. Hook up the sub via speaker level to the main amp speaker terminals. It has very high impedance, so the amp doesn't "feel" its presence. This is what Jim Smith and others in this thread recommend, and it is what Rel, for example, recommends, for the smoothest transition. In that case, you would not want to use crossover circuitry in the receiver. The variant we have also been discussing is to have stereo subs -- one sub hooked up to the left speaker terminals, and one hooked up to the right. Then you don't have to worry so much about ruining the stereo effect if your sub's crossover is set higher.

 

So no, you would not get the benefit in terms of conserving amp power, but the tradeoff is better sound quality (although I am taking that as a given -- I haven't personally got experience with testing the various options). I would advise experimenting with both types of setups if you are inclined to tinker.

 

[bikemig]

@wgscott: I have a question about 2. Nearly all 2 channel rigs lack bass management. So you either use the high level connections via speaker wire or the rca input on the sub (assuming your 2 channel amplifier/receiver has a sub out). My understanding is that the advantage of high level connections is that once you set the sub cross over, the signal is split so the sub plays the low end and the speakers the high end (I know these aren't the precise terms). But I don't know if that's always true. I believe that's the way REL sets up its speakers and I know that it true as well with NHT subs (I wrote to the manufacturer on this) but I have no idea how common this is. Most of the sub manuals I've read don't mention this and simply state that it's your choice whether to go with a line level signal or the high level connections.

 

[wgscott]

Some subs have high-level in and high-level out, so you can use the crossover in the sub to do exactly as you say. Sorry, I forgot about that.

 

[crisnee]

Hi Roark,

I would assume that the sub out on your receiver works. Why wouldn't it? Or do you know something you're not mentioning? You also don't mention how small your speakers are, or their bass cut off frequency.

 

A sub should make a large difference, if your speakers lack low end ability--depending on what kind of music you listen to. If you listen exclusively to chamber music and acoustic guitar it might actually be a detriment, but otherwise, it should (at least) add heft and substance to your overall sound--which I find makes a big difference. And more, depending on the quality of the sub and how well it's integrated into your current system.

 

I'll assume you're using your sub out. In that case, you will definitely put less stress on your bookshelf speakers (which should help them perform better), use the power of the powered subwoofer, get deeper bass, and here's the thing that I think really makes a big difference. You can now place all your speakers for best sound and imaging. Imaging and bass extension don't usually live in the same area of your listening room.

 

By the way, I think all the above also applies if you use the speaker outs, but I'm not 100% sure about the power usage. I think you're still activating the subwoofer power amp with the speaker signal and not using the power of the amp, but I'm not sure how that works exactly or if that is so. Would someone with the tech knowledge weigh in?

 

About the placement. You can place your speakers for best imaging, and your sub for best bass. Of course all this is kind of tricky, so it will take some experimenting, but in the end it should make quite a difference. I recommend you look into something like the Jim Smith book/dvd on setting up your system. Just search for him on CA or elsewhere for more info.

 

-Chris

 

[roark]

I know this is an older thread but I had some follow up questions:

 

Apart from the sound quality improvement of adding a sub or subs do just about all of you that have them live in a detached house? I ask because I have a townhouse and if I added a sub it would almost certainly have to go along the shared wall with the next unit due to the layout of the room. I am concerned because I don't know if I would be able to enjoy and get the benefit of the sub at even moderate volume without disturbing my neighbors. Have any of you ran into this issue in either townhouses or apartments as I would think it is common? In those environments even if in general terms you think sub(s) are better to use do think it is likely not worth it for practical reasons?

 

Thanks.