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Let me first credit Richard Bass Nut Greene as the primary inspiration for this exploration. I'm clear now that he's at least half right (haven't tested the second half) when he states repeatedly that: You can often get better results with EQ with a cheap sub than with an expensive sub without EQ (paraphrasing here, so forgive me, Richard!) I've now proven to my satisfaction that the first half of that sentence is clearly true.
Quick background: I've loved my low reaching VR1 monitors, but always found that extra depth I get from even my cheap KLH sub was needed and appreciated. However, it never sounded clean or "tight" by comparison to the monitors alone. So I did quite a bit of querying and Web exploring - with thanks to all the inmates who helped. I also did my best with finding the best placement and phase and X-over and volume settings I could within the limitations of my room and WAF. So the issue was: invest in a better sub (beyond my budgetary constraints) or build one, or remain somewhat dissatisfied.
Decided that I had nothing serious to lose by following RBNG's advice to get a RS SPL meter and a cheap Behringer Feedback Destroyer 1124P for EQ before investing in expensive subs. $50 for the SPL meter, $60 for a used BFD, = $110 vs. $500-1000 for a new and supposedly "better" sub. Hell, I could always return or resell the gadgets if they didn't work out!
The BFD isn't the world's most intuitive device to operate; it does take some head scratching even with "simplified" instructions from HomeTheaterShack.com and others. But once you get it, it's a matter of experimentation and then it gets dialed in. I don't believe for a minute that I'm done dialing in the EQ filters, but even at this crude level the difference is at least a substantial part of what I was hoping for (and didn't believe I was going to get from EQ).
As RBNG posited, there were at least 3-4 serious peaks in my sub's house curve that were interfering with good sonics, and his suggested ranges were surprisingly close to my own. Since I have the EQ only in the sub circuit, deliberately as nobody recommends this BFD unit for above that, I don't use it to smooth out the peaks due primarily to the mains, but smoothing the sub's region and the sub/mains overlap from 20-95Hz does quite a bit of good. Also, as recommended I have not tried it to boost a serious dip at 110Hz yet.
What I don't completely get yet (and that may be a matter of more experimentation, rather than real limitations) is the tightness my monitors can deliver when the sub is trying to reproduce very rapidly changing notes (think Grapelli on violin or Hendrix on guitar) of an acoustic double bass. It's much much better, but you can still detect some misalignment or hanging over of the notes. It's still a very good impression, just not "perfect". And I have to wonder if a better sub driver/amp combo might do the trick, but until I've exhaused the BFD, I'm not going there quite yet.
So in summary, EQing subs works as predicted IME. And those better sub amps with single range EQ alone would not have worked as well for my setup (nor the average if RBNG is correct).
What I get now is much tighter bass, more realistic sound from bass instruments without any boominess. That's a good deal for so little investment. I'd recommend to others that they try this route.
Follow Ups:
I agree. I am using a Symetrix 551E analog parametric equalizer for both the subwoofer on my main stereo (a Hartley 24" woofer in a open baffle) and my HT setup and the bass is MUCH smoother. Aside from one room related dip my main stereo measures +1, -2 dB from 20 to 100 Hz using warble tones.I have no idea who thought of it first but I believe that Vandersteen and Infinity (Floyd Toole) were among early commercial promoters of equalized bass.
Edits: 01/03/09
I'm sure you must be aware of REW if you visited the Home Theater Shack's forum's.
On thing you may not be aware of is that the Behringer unit introduces a 1ms delay to the output.
This type of set up was originally meant for HT receivers and processors that have distance/time settings for the mains, center, and rears. This allows you to compensate for the time delay of the dsp unit.
I'm not saying that you can't get acceptable results without compensating for this delay, only that it would be better if you could.
I had planed to use a DEQ (strictly in the digital domain) for the amp driving main input of my Gallo Ref 3s which has a time delay feature.
Then use the BFD 11/24 for the amp driving the Gallo's woofers second voice coil. I never got around to it, as the aes/ebu input of the used DEQ 24/94 didn't work.
Please keep us posted on your results.
Julien
"There's someone in my head, but it's not me"
No one can hear a 1 millisecond delay from a subwoofer.There have been studies showing a 5 millisecond delay (subwoofer five feet further from ears than main speakers) is the minimum audible delay. Some experts suggest no more than three foot differences (3 ms) to be safe.
No one has ever presented any evidence that a one millisecond bass delay is audible by even one listener.
But ... most people CAN hear a room bass resonance that stays audible for roughly 200 milliseconds AFTER the sound from the subwoofer (or full-range speaker0 stops (-30dB attenuation assumed to be "inaudibility").
So if a one second delay bothers you, just move the subwoofer one foot closer to your ears to eliminate it!
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.Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Edits: 01/04/09
There are other places where you can introduce delays with a sub including the existing sub placement which is often (probably usually) further away than the speakers, and the filters and circuits already present in active subs.
A 1 ms delay may not be audible on its own but, added to existing delays which are also inaudible both individually and together, that additional 1 ms may be the difference between an inaudible and an audible total delay so it is possible that someone may notice a delay on introducing the BFD.
If you've got an existing delay which is very close to audibility, it needn't require much to push it all the way to audibility. There will be a point at which a mere 1 ms addition is enough to do just that and if you're unlucky enough to be at that point you will notice it.
David Aiken
With a subwoofer, typically located 8 to 12 feet away from your ears, the majority of bass energy that reaches your ears will bounce off one or more room surfaces first.
Most of the bass energy that reaches your ears IS ALREADY DELAYED by many milliseconds because of the time needed for reflections off walls, floor, and ceiling ... before reaching your ears.
Also, there is no test evidence that any human can hear a 3 millisecond delay, much less a 1 millisecond delay, in the subwoofer frequencies under 100Hz.
I'd say the use of a digital subwoofer parametric equalizer to eliminate 2 to 4 bass peaks of +3 to +6dB .... is FAR more important to the bassline than the added 1 millisecond delay (that could be immediately eliminated by moving the subwoofer 1 foot closer to one's ears).
The probability that a subwoofer is currently located in a position where a mere 1ms of additional delay makes the "time gap" between the subwoofer and main speakers audible ... seems like a low probability event.
Let's say a specific listener with really good hearing can hear a 5ms subwoofer-satellite speaker time delay.
For an additional 1ms delay to make an audible difference, his subwoofer would have to be located where it had at least a 4ms delay (which would need an additional 1ms delay to become audible) ... but had no more than a 5ms delay (which would already be audible).
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
I could swear he said the human ear/brain combo was capable of discrimination on the order of a few femtoseconds. Is that wrong???
The direct sound always arrives first and is always higher in level than the first reflections.
What you say about most bass being reflections and delayed is true of all frequencies, not just bass frequencies. That doesn't make the direct sound unimportant. Some parts of our perception are drawn from the direct sound and some from the reflected. The direct sound usually gives us our timing for a sound since it arrives first. Exceptions can occur when a later arrival is louder, which doesn't occur with individual reflections, or arrives after an exceptionally long delay which won't occur in a room. The fact that, in some cases, the reflected sound field can, in total, be louder than the direct sound is usually irrelevant in small room situations like ours because it simply isn't sufficiently louder than the direct sound for the direct sound to lose precedence and, in any case, the brain is taking information from individual reflections, especially the first ones which arrive as separate events with clear intervals between them.
And you said: "Also, there is no test evidence that any human can hear a 3 millisecond delay, much less a 1 millisecond delay, in the subwoofer frequencies under 100Hz."
That still misses my point. There can be other factors delaying the direct sound and they may not delay it enough to make the delay audible so we have an inaudible delay. Add another delay and you can end up with a total delay that is audible. An additional delay of 1 ms will, in the right circumstances, be enough to make the total delay audible so it is possible to notice the addition of a 1 ms delay. I never said it will happen every time but it can happen in some cases.
David Aiken
Such a large percentage of the bass energy under 80Hz. is reflected energy that it's almost irrelevant to discuss direct versus reflected sound at those frequencies.
If subwoofers are set up properly, placed near other speakeres and located approximately the same distance from one's ears, then adding a 1ms subwoofer timing delay by using a digital parametric EQ is very unlikely to be audible.
But if the subwoofers were located far behind the main speakers, perhaps in the room corners where they produce the most uneven frequency response possible in a rectangular room, then it's possible adding just 1ms additional delay could create an audible deterioration of the bass note quality. (Moving the subwoofers 1 foot closer to one's ears would regain 1ms.)
One could also buy an analog parametric equalizer, which is more expensive, and much harder to set precisely, compared with a digital parametric equalizer ... but an analog EQ would avoid the 1ms time delay caused by A to D to A processing.
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
It's always relevant to consider direct vs reflected sound because they contribute different things to our perceptions.
And you keep missing the point that it's not the delay added by a particular device but the total delay introduced at all stages that can be the critical factor.
End of discussion.
David Aiken
The point seems to be whether an added 1ms delay for subwoofer frequencies would be audible, and not sound right.
I say that's very unlikely to be audible.
You had no point, other than pontificating that 1ms of additional delay might be the 'straw that broke the audio system's back'.
The benefit to the bassline frequency response from parametric EQ is so much more audible than a 1ms time delay, that I can't understand your theoretical problem with a +1ms delay.
An analog EQ would avoid the 1ms delay.
Or use a digital EQ, and move the subwoofer 1 foot closer.
Ho hum
Case closed.
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
I didn't know about that 1 ms delay injection. Now how to cure that other than more DSP or different positioning?
David Aiken had originally suggested time factors to me when I started this exploration. His solutions: change position to have sub significantly closer or use the full time domain processing of an HT receiver.
I was able to play a bit with positioning before the BFD experiments and did indeed realize some timing improvement, but may be out of luck on any close positiong -- WAF issues.
As to the HT processor, that's not somewhere I can either afford to go or want to go at this time. I don't want to introduce more complex circuitry for 2 channel music. This BFD may be quite enough DSP for my taste; I have it limited to the real LF regions, where it's less critical to the musical signal, rather than all across the spectrum, where its side effects might be more noticeable.
Thanks for the info, Julien. I will keep you guys posted. Don't expect quick changes, though, as I have to get my wife out of the house to do any serious experimentation, and that waits unitl next week when she goes back to teaching school.
I use a similar solution for the modest HT system. In that space where I have little ability to experiment with placement, I had 12 db peaks at 63 and 120 hz with smaller dips at 80 and 100 hz. Since it is a ported design, a tad of boost near its low end cut off of 30 hz helped as well. Measured and audible results are far better. I did, however, have to run the EQ off a cheater plug because it introduced a ground loop.
Because the upper peak is beyond the *usual* range where subs are added (say 60-80hz), I got the best results by moving the high pass for the mains and the low pass on the subs upward to 120 hz so that they can be part of the equalized solution.
rw
Did you turn your sub's x-over to 120 Hz? I never tried experimenting in the opposite direction by going up, rather than down, the spectrun. All advice I'd seen suggested to keep the x-over as low as possible, which is where I ended up.
My cheap KLH sub does facilitate better integration by permitting output viat the sub's x-over to the main speakers. Thus, cutting off the bottom of the mains at the x-over point and the top of the subs, with some overlapping range. But that would mean pumping the mains through the cheap sub plate amp with all its distortion, and that made no sense to me under the circumstances. If the sub had a really good amp, then maybe I would have done that, but that's not the case at all.
FYI, I am dedicated to 2 channel music only and not at all interested in nor seeking future HT setup. Not snobbish, just not my cup of tea, and at the current market prices make that hemlock tea! LOL
Where the subs still have some response above that cutoff. After MUCH experimentation, I found that approach ended up with the flattest overall measured response. I too, began with a far lower setting and could never get the third octave smooth. Which also has the benefit of balancing the power burden more towards the 120 watt subs vs. the 100 watt mains. The mains still clip first.
...that would mean pumping the mains through the cheap sub plate amp with all its distortion...
I hear you. In my case, the NAD T755 receiver has its own variable high pass filter for the mains. I run the subs directly from the LFE outs. Which meant I had four sets of variables: mains high pass frequency, subs low pass frequency, subs level and LFE level. I balanced the results with the LFE level set very low for the flattest response so that I could always crank it with the remote if needed.
I'm now convinced that having at least a bi-amplified arrangement using equalized subs is a great way to go. At least when one does not have great placement latitude and a forest of bass traps as I do in the music system. :)
rw
My NAD C740 receiver does not have any X-over built in. It's strictly classic 2 channel music. In fact, it doesn't have a sub out line level either, so I use silver Ys between pre and amp to do that duty.
Not sure your approach would work at all in my situation, unfortunately.
The NAD does a fine job with the VR1s; the KLH plate amp even publishes its specs as having 10% THD at 120 W and only about 1% THD at best down at 100W, so I'm not impressed with the idea of using its circuitry on the mains.
Also - and here's where my theoretical approach may be way off base -- I figure that the sub is the weak link in my speakers, being an el cheapo. By comparison, the VR1s are very well made and voiced and reach accurately (at least to my ear) down into the 40Hz range without stress. So I wouldn't want to swap the upper bass and mids of the great VR1s for the probably crappy ones of the KLH. That makes your solution improbable for me.
Given the factors you mentioned, it seems the subs are used to extend the bottom octave. The value to me for running an equalizer is to address room modes. Such usually requires correction out to 120 hz or so.
rw
What we're all fighting with EQ is both the characteristics of the speakers AND the room nodes. Just depends on which is your main emphasis.
Obviously some of my original and remaining problems aren't simply the repro characteristics on the freq spectrum of the sub or mains. Some of them must be room issues in the bass quadrant, and Richard's general postulation of about 3-4 characteristic freq problems for most folks in the sub range is really the room issue generalized.
That suckout at 110 Hz in my room is undoubtedly a room issue remaining, though I haven't tested to see if it improves outside of my chosen seating position.
In some ways I've been fortunate with my room, which isn't technically even a classic rectangle (due to open hall system it feeds into on one side, 2 levels of height, half wall, etc.). It appears from some room calculators that my seating position, my reverse placement (I have my speakers on the short axis across from me), room dimensions overall, actually aren't too bad compared to many standard rectangular situations. And in practice, I'd say it's workable so far using acoustical tricks and working within limited placement. So I'm not concentrating in the direction you are at this point.
I just want to hear the initial pluck of a bass mated to the follow on twang of the strings, the resonance of the wooden box, and the decay as realisticaly as possible. Same for percussion, with which I'm highly familiar. A drum doesn't simply THUMP. And it doesn't hurt to hear the human voice with its depth correctly protrayed either!
Ah well, the drive to perfection will drive you nuts, and in my impoverished case, nuts all the way to the poorhouse... LOL
Richard Vandersteen for incorporating bass EQ in his two (and now 3?) top of his line of speakers, first with the Model 5 ten years ago.
Cheers
While quite a few sub and sub amp maunfacturers are now copying that move (though not all), they seem to include only single range EQ. What RBNG posited that was true for my room was that there are several ranges requiring EQ in sub territory, and single EQ isn't going to cut it.
I have seen some sub amps - standalones, not plate amps - that have multiple EQ ranges and bass boosts. There don't seem many of these. And they still can't beat the 12 filters/channel that the BFD offers.
I'm not selling BFD or anything here. Just reporting the results of my explorations, however primitive and limited...
Thanks for the complement ...
... but I think you have taken "cheap sub" to a level well below what I had in mind.
To me a $500 list price subwoofer is a cheap subwoofer.
When you go below $500 list price, your risk of buying a ported subwoofer whose port tuning is deliberately set too high to produce a bass peak that makes the bass sounds louder (but not better) begins to increase.
Inexpensive sealed subwoofers wouldn't have that problem, but inexpensive drivers with small excursions (XMAX) mean you don't get a lot of displacement for your money (and without a port, bass from one inexpensive driver in a sealed enclosure is likely to decline 12dB/octave below 30 or 35Hz.)
However, in most rooms an inexpensive subwoofer combined with a $100 digital parametric EQ can produce a much more accurate bassline at any ONE seat, than any unequalized sub at any price.
Limited maximum SPL, and little audible output under 30Hz., are the risk when using a cheap subwoofer, even when it is designed well.
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Richard,
I'm laughing about your concept (held by most inmates here it seems) and mine of "cheap". As another inmate once put it, he dubbed me the "cost IS an object" guy. I'll take the compliment. Half the fun for a guy with champagne ears and a lite beer budget is proving that the cost benefit curve goes much lower than many believe....
Anyway, my el cheapo KLH 120W 10" ported sub is about as low as they go. But it does put out appreciable sound down to 20 Hz and from 25Hz that I can hear, and the SPL meter confirms. It picks up sharply about about 28-29 Hz and definitely first peaks in the early 30s. So while its port may be another issue I haven't played with yet, it does the SPL trick well. It just doesn't do articulation well. I don't hear the dreaded chuffing.
As I've said, I'm quite sure I can do better for subs, once I get to the $500-1000 level. Hell, if you believe some of the reviews of Hsu, Outlaw, Onix, a Dayton kit, etc., I can do better as low as $300-500 than I've got currently. I was attracted for years to the VRS-1, which was $1500 and can be had for about $1000, but I suspect that it's now superceded in quality for less by some of the newer models from other manufacturers. It did mate very very well with VR1s, was surprisingly compact and looked great, sigh...
What had me buffaloed was the bewildering array of claims and disputes over config, and features, and sizes, etc. related to subs at any cost, including DIYs. All of which were NOT usefully auditionable in showrooms even were I able to locate them (and you usually can't). Buying on spec and paying the cost of shipping back and forth seemed not just daunting, but counterproductive.
So your interim step of the EQ made a lot of sense, and as I credit you fully, it was right! We'll see how far this goes for benefit now, while I continue to research and mull over better subs.
It would be easy to pass this off as my being just damned lucky. But I really do spend an inordinate amount of time researching and contemplating every move, due to budget constraints and pure orneriness, so I've made very few bad moves in my purchases so far. Most of my tweaks and purchases work very well and even better together. Until I hit the lottery... then watch out!
There are many 8" and 6.5" non-ported "subwoofers" that are "lower"My first "real" speakers were KLH 17's many many decades ago, but I suspect some Chinese company bought the KLH logo used today.
A real audible improvement would be from using two (Left and Right) KLH subwoofers.
Adding another identical subwoofer increases maximum output +3 to +5dB (+6dB if both are stacked in one place) ... and left-right subs prevent a standing wave between the side walls that causes a bass null halfway between those walls (where most two-channel audiophiles sit) ... because left and right subwoofers (or left and right full-range speakers) would be out of polarity for that room mode = so no standing wave will occur!
(565 / distance between side walls in feet = center frequency of standing wave null in Hz.
(This is the important side-wall-to-side-wall first-order axial room mode, that will cause a partial null roughly 5Hz. wide measured by the -3dB points, and up to -20dB to -30dB deep at the minimum SPL point exactly halfway between the walls if both walls are equal bass reflectors = way more than anyone needs to know).
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Edits: 01/02/09
Yes, there are lower freq subs, of course. Yet it does pump out SPLs quite reasonably low for my use, which is exclusively 2 channel music.
My next exploration might be a cheap try at a second sub, maybe a slave if not a matched box. I really wouldn't want another KLH in my room as my wife would go bananas, and given their size and looks, I wouldn't be too pleased myself.
But a couple of smaller slaved subs as an experiment, if I can find them, would be interesting next.
Buy it and tell her you won it in a football pool.
If there's a high pass filter in the KLH sub amplifier, it's probably a single inexpensive capacitor for each channel = 6dB per octave high pass filter.
6dB/octave won't do much, but if you ever play your main speakers really loud, some high pass filtering is useful to protect speakers with small diameter ported bass drivers.
I prefer a 24dB/octave high-pass filter with small satellite speakers, but that's rarely built in to commercial subwoofers, and usually requires an external active crossover.
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
As she knows I don't pay any attention to sports, much less bet on them! She's more likely to do that than I.
The sub's specs list the 24db/octave for the X-over, but do not list the high pass specs for the mains outputs, so I have no idea what that would be.
See my response above for info as to why I truly don't believe running mains through the crappy sub is of any benefit to me, while improving the less demanding bottom end with EQed sub does make sense (and it sounds good in practice too!)
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