The pursuit of bass...

Legacy Focus 20/20's

them some great speakers:)

Bob - Since it's in this month's TAS you'd have to be a subscriber to the online edition to read the article. I am not. I just got the issue in the mail yesterday, so it should be on newsstands and in libraries shortly. I imagine in a month or two it might be available at no cost online - I'm not sure how that works. Obviously it is copyright protected material so don't think they'd appreciate anyone posting it at this point in time.

Hi Jax, is there a link to the article? Or is this an article you can post a copy of?

Bob

Just as a follow-up to my own question, I just received the latest issue of TAS which has a review on a DSP device for subs called the DSPeaker. Based on similar technology being used in subs that have integrated DSP feedback devices, like Velodyne, it is a $350 black box for use with subwoofers without that option. Anyway, the article directly addresses the common problem I'm having of a suckout caused my room modes in the lower regions below 100hz, and then between 100-200hz. The concept of electronic mode correction is suggested as having potential benefit to this problem. The author does report major success with this particular device (not applicable to my particular arrangement as my subs are integral and not standalone), as with the more expensive PARC device. Duke, the author, Robert E. Greene, does mention in passing how effective the potential of your Swarm system might be, towards the end of that article.

On a further note and query, I've just borrowed a better mic to do a bit more in-depth analysis on my laptop (otherwise was relying on the mic in my iPhone and StudioSix software). Can anyone recommend good RTA FFT software for Mac that is freeware or that doesn't cost an arm and a leg?

Many thanks for the 411 on Pink vs White db!!

Jax2 asked: What is the difference between pink noise and white noise (noticed the recommendation for white noise in the Geddes reference)?

IIRC, white noise has equal SPL/Hz across the spectrum, whereas pink noise has equal SPL in each octave band. Pink noise is thought to be more relevant to the perception of sound. It's been nearly 50 years since I've had to know such stuff, so my recollection may be faulty, but the distinction is something along those lines. I'd be inclined to use pink noise unless Geddes has a well reasoned rationale for his preference, though white noise generators that meet specs may be easier to find in products aimed at the consumer market.

db

Jax2, can you borrow a sub? Perferably one with a phase reversal switch. It can be a small sub that doesn't go very deep. Try it along the wall behind the speakers, with the phase reversed. I'm hoping that its response will "zig" where your main speakers "zag". Also try it along the wall behind the listening position, starting out with normal polarity. Having powered subs in your main speakers is a big advantage here, because in either of these cases you will probably need to adjust their level.

You said that your speakers were "solid", with "no boxes" - could you elaborate?

Thanks for the sub suggestion - Again I have such limited space that it becomes a real estate issue. I have had a sub in here several times before, though not with these speakers as no one would ever listen to these and think they need anything more in the low end. I can reverse phase on my preamp, but of course that would address both sub modules and do nothing like you suggest. I can also separately attenuate the sub sections (as well as the tweeter) on the speakers. I have tried that and the suckout remains unchanged, hovering around -10db while other regions do change. The point I was trying to make is that it's not the specific speakers, but the room that's causing it. Elviukai - there is indeed a peak just below the suckout dip, right at 50hz. Again, a consistent theme no matter what speakers are in place. So it sounds like the only real way to to address this is to alter the position of the system in the room, as Duke suggested from the start?

Duke, the current speakers are AudioMachina Pure System MkII. The body is solid aircraft aluminum (no box - just enough space for the drivers including the sub driver). The online information has not been updated to the Mk. II version, which has changed from Karl's dated website (I'm working with him on an updated site with new images). They are extraordinary speakers...quite unique...sound amazing; basically a full range driver with a subwoofer and supertweeter. If you have not heard them, check them out and introduce yourself to Karl at RMAF. You'd probably enjoy each other. They have attenuators on the sub and on the supertweeter.

The room's been a thorn in my side from the time I had to move my system there from my studio (which I gave up five years ago). I'll include it in this discussion only because it certainly does play a big roll in the pursuit of a full range sound. It is about 11+ feet wide by 24 feet long and the furthest 10 feet of that length opens up to about 16 feet wide with a cathedral ceiling and a 14 foot peak. The system is on the long wall at one end of this space furthest away from where it opens up larger. A big sacrifice I had to make is that the system had to go under the the higher part of the sloped ceiling (ideally I would have it the opposite way). So at the listening position the ceiling is 8 feet, and at the system/speaker it is 11 feet. Speakers are about 30inches off the back wall and listener about 7 feet from the speakers. It's a very challenging room. Hardwood floors with area rugs and lots of hard surfaces which make it very lively. Plants and room treatments are all I have going for me. That and being nearfield does obviate some of the room issues, while making bass a more challenging issue, as I understand it. The overall volume of the space is probably around 2000cf. Any WAF suggestions would be appreciated. Duke, if I do get the chance to borrow a small sub I will try what you suggest, but you're asking me to put it where the bass traps are (directly behind the speakers).

My pursuit of a little more bass has me using equalizer. While using my music server I started to play around with iTunes and the equalizer in the program. The adjustments are made on the fly from my listening chair. I have to tell you I am really enjoying it.

You need space for bass most loudspeaker designs are highly compromised in performance as to pas WAF allow hi profits ease of manufacturer shipment etc. Good sound while not the last thing most loudspeaker designs strive for but not near the top either profits are. Many have also been sold the line for years that little monitors with wee subs or slim towers are the better performing designs when its the complete opposite thats true. So you end up with most loudspeakers producing little to no infra bass. Or bloated subwoofer adding there drone. Bass response dynamic range and lack of thermo compression are critical to great sound but conventional designs mostly over look this.

I would be more concerned about peak somewhere ocatve of half below or above that dip. i have instaled nearly half hundred rooms and in rooms with clear resosonse mode there is always (mostly in theese areas ) peak at 58-65Hz and dip either 80-100hz or (more common) 35-42hz. there is nothing can be done for preventing main room resonanse mode. even if it can be atenuated by digital eq corection ,its level just maches main spl level but resonanse stays(its just much lower in level)its very audible on recording where music piece exactly maches peak..

Jax2, can you borrow a sub? Perferably one with a phase reversal switch. It can be a small sub that doesn't go very deep. Try it along the wall behind the speakers, with the phase reversed. I'm hoping that its response will "zig" where your main speakers "zag". Also try it along the wall behind the listening position, starting out with normal polarity. Having powered subs in your main speakers is a big advantage here, because in either of these cases you will probably need to adjust their level.

You said that your speakers were "solid", with "no boxes" - could you elaborate?

Thanks,

Duke

Duke - My current speakers have no ports, (no boxes either, for that matter - they are solid). They do have powered subs. The speakers they replaced did have ports, as did the speakers I had previous to those. You could look at the in-room graphs for all three and there would be the same 80hz (+ or - 10hz) suckout on every one. Also on a pair of ported monitors before that - same suckout. All but the current speakers have been ported. Various room treatments also did not change this. My current speakers have a relatively flat response down to 20hz in room so they aren't otherwise suffering in the low end. There's another dubious dip at around 200hz that keeps showing up as well that I suspect is a room thing, but it's not nearly as steep as the suckout at 80hz, which is usually around 10db.

Jax2, the reason I asked about what speakers you have is to see whether the port tuning could be changed (lowered) which would allow a small subwoofer to be added, preferably along the rear wall or in a rear corner.

Duke

Jax2, can you tell me what your main speakers are? That might help me come up with suggestions.

One possibility is to rotate the speaker-listener-speaker triangle perhaps 15 or 20 degrees clockwise or counter-clockwise, as seen from above. This will introduce asymmetry in the horizontal plane, and may reduce the depth of the 80 Hz dip.

What happens to the 80 Hz dip when doors are left open or closed? An open door can be a very effective bass trap, for better or for worse. Does the room have a closet? Try that as well.

I couldn't tell you why Earl favors white noise over pink noise; the latter is what I'd be inclined to use but Earl is one very, very smart guy so he probably has a good reason.

Hey Duke, thanks for the response. It doesn't matter which speakers I use, the suckout always seems to occur at the same point. Looking at in-room response curves the dip is there whether full-range or monitor or? No closets. One single door, and I WILL try closing it and see what happens when I next have a chance. It is immediately next to my right speaker and I usually leave it open with diffusors in front of the open door (first reflection point). The opposite side first reflection has no wall at all. The triangle-rotation is a great suggestion, but WAF prevents that option without major domestic disruption.

Thanks, Duke!

I pretty much agree with Tim916 I am using 3 subs now in my 2 channel. I have built all 3 subs. 1 is an 18" Maelstrom X in a sealed 6.2 cu ft enclosure, the second is a 15" Dayton in a 6.7 cu ft sealed enclosure, the 3rd is a 12" ported 3 cu ft enclosure Peerless XXLS. My Geddes Abbey 12As arrive in 3 days. This system will be set up as Tim 916 describes. I am following Dr Geddes philosophy on subs (multiple randomly located) room frequency measurements will follow when I get the speakers. Up to this point using my Definitive Technology speakers with the 3 subs. The bass in my system is the best it has ever been by a large margin.

Jax2, can you tell me what your main speakers are? That might help me come up with suggestions.

One possibility is to rotate the speaker-listener-speaker triangle perhaps 15 or 20 degrees clockwise or counter-clockwise, as seen from above. This will introduce asymmetry in the horizontal plane, and may reduce the depth of the 80 Hz dip.

What happens to the 80 Hz dip when doors are left open or closed? An open door can be a very effective bass trap, for better or for worse. Does the room have a closet? Try that as well.

I couldn't tell you why Earl favors white noise over pink noise; the latter is what I'd be inclined to use but Earl is one very, very smart guy so he probably has a good reason.

Hey Duke - Can one correct (or compensate to any degree) for a room-generated suckout? My room has a consistent suckout with every speaker I've measured, at around 80hz , from the listening position. I understand that a low-end suckout is very common with most rooms and varies in terms of where it occurs within the range - correct me if I'm off base. Alas, I must listen nearfield (7-8 feet ears to speakers) so am locked into a rather narrow latitude of movement of both listener and speakers. There is some, but it is rather small. I'm currently using some treatments but wondered what, if anything, might be most effective with dealing with a room suckout like that? I'm guessing it may be limited to changing the listener position or the structure of the room itself. Current treatments include bass traps, diffusion at first reflection, and absorption on back wall, and between the speakers.

A brief follow-up question - I've been using pink noise to gauge such things. What is the difference between pink noise and white noise (noticed the recommendation for white noise in the Geddes reference)?

Plato, the equal loudness curves illustrate that the ear itself is not "flat"; I wouldn't consider them to be any sort of "target curve" for loudspeaker frequency response, but they do show where a designer needs to be careful; in my opinion you correctly identified 3-4 kHz as a particularly critical region. A dip in this region does make a speaker more forgiving, but it also results in the overtones of many instruments being under-represented, which detracts from a realistic presentation.

As to why a "flat" speaker usually sounds bright, I think that has to do with microphone placement during the recording process and the acoustic differences between our listening rooms and concert halls. Some of it may have to do with loudspeaker radiation patterns as well (many speakers have an off-axis flare in the 3-4 kHz region because the tweeter's pattern is quite wide there).

Tim916, the effects of small room acoustics in the bass region is indeed a significant issue. Since the room-interaction peak-and-dip pattern can change dramatically with a small change in listener location, the improvements from equalization are usually limited to a small area, and the response may actually be a lot worse in other locations because of applied EQ. Of course, this may not matter much if listening is confined to the sweet spot. Now I noticed you said "subwoofer(s)", leaving the door open for more than one. A distributed multisub system will reduce the amplitude variance (smoothe the frequency response) as well as the spatial variance (less change in frequency response from one location to another). As a result, not only is equalization less likely to be needed, but if so it is more likely to be an improvement over a wide area.

It is possible to spread out the in-room bass sources somewhat even in a conventional pair of speaker boxes (no sub), by using multiple woofers spread apart or locating the port in a different plane from the woofer. The improvement is not as dramatic as with scattered multiple subs, but it is still worthwhile in my opinion.

Duke
dealer/manufacturer

Building full-range speakers is pretty much a waste of woofers and wood due to the realities of small room acoustics. A speaker should be designed to play down to 70-80hz with little distortion at high volumes. The equalized subwoofer(s) take over below this point. Even massive speakers like the Wilson X-2 and Rockport Arrakis will benefit from this configuration.

Hi Duke,

Thanks for posting the "Equal Loudness Curves". This must give the speaker designer something to think about in that if you build a speaker with measured flat response between 3kz and 4kHz it will be perceived as "bright" by the average person.

I would also say that because of anticipated room gain you would not need as much boost in the low bass as the curves would imply but correct me if I'm wrong on that.

So what this means is that a speaker that measures perfectly flat will sound bright to the average person. Also anemic in the bass if there is inadequate room gain.

This makes sense to me as I use an EQ in my large-room system to boost low bass slightly, cut the response a dB or two at 2k, and 3 - 4dB at 4k, and I add couple dB's of boost at 16kHz.

Putting my designer's hat on, bass is largely a matter of juggling tradeoffs. It's not that difficult to get good bass if you start out with a big enough box. If box size is severely constrained, we must make some hard choices between bass extension and efficiency (and it's not quite so simple as it looks at first glance).

On the other hand, the midrange and lower treble are much more difficult to get right. That's where I may spend hundreds of hours during the design phase.

A set of equal-loudness curves will graphically illustrate what the ear's sensitivity is at different frequencies across the spectrum. This is a good roadmap for telling us where the ear is especially critical and where it is relatively forgiving.

equal loudness curves

There is a great deal of useful information in these curves.

Now the curves still don't tell us how much each portion the spectrum contributes to overall subjective enjoyment. In my opinion bass in particular needs to be balanced relative to the rest of the spectrum. This means different things for different speakers, and the behavior we want from a given speaker may change depending on the room acoustic situation.

In my opinion if one places high priority on really good bass reproduction, the mini-monitor format is too inherently compromised to really deliver. Make the aesthetic tradeoff to a floorstander, taking into account your savings on speaker stands, and you will be well ahead of the game. Or add a good subwoofer system to those mini-monitors.

Duke
dealer/manufacturer

Agreed with all that has been said hear regarding getting all frequencies as close to 'right' as possible and the difficulties of getting midrange right as the alternative is often hard on the ears and intolerable. Full spectrum bass adds so much to the enjoyment of listening regardless of type of material; finding a speaker that has as much put into achieving the speed, accuracy, tonality, decay etc....for bass and deep bass frequencies is a very hard task. As others have said, if a speaker gets the bass right for jazz it often produces too much or sloppy bass for other types of music. I'm currently enjoying Focus SEs from Legacy in so many ways; they have excellent price to value/performance and most notably they are incredibly musical and do a great job across the entire spectrum of frequencies. I enjoy very much hearing the subtleties in the all the frequency ranges especially the subtleties of a double bass note in a jazz ensemble or any percussion instrument head being struck at low-mid (i.e. real-world) listening levels. I've heard a number of speakers that get these things right; they often cost much more than the SEs that will be in my system for years to come.

The sense of space and ambience one perceives from well made live recordings is more dependend on full, accurate reproduction of bass frequencies than other parts of the spectrum.

First off,I completely agree with your assessment re: bass and the degree of difficulty in getting it right. IMO. getting the bass right is the biggest and (for the most part) most expensive technical challenge a full range speaker designer faces..

OTOH, you note that speakers face room problems, but that you mostly blame the speakers. I disagree. After screwing around with this problem since I first started the hobby in the '70s, I have concluded that few, if any, speakers can offer smooth behavior below about 120hz. It's the room. I went the DRC route (subwoofers), got great results and called it a day. If you want to try and beat the room problem in the bass without DRC, I wish you the best of luck. I couldn't do it.

Marty

I agree that bass is challenging to get right, and integrate well. I've certainly heard speakers that integrate the full range from top to bottom very well indeed, so it is not by any means impossible. I do agree that the room will play a very significant roll in how successful it all comes off to the ears. Where subwoofers are concerned, multiples definitely help. Taking the bass demands off of the midrange drivers also helps midrange.

Just looked at your system. Very nice (I have a Bryston B100) which should be the next thing I replace. Add a Rel sub AND replace the stock 30' cable. The cable will make a huge difference and make the sub blend in with the Dyns. I replaced mine with a nordost baseline and finally got the bass that sounds more natural (kind of like the C4's).

I agree with Rtn1. I have the Dyn C1's and a Rel B3 sub. Once dialed in they sound like much bigger speakers.

I used to think that bass was most difficult to achieve. Now I appreciate that every frequency is difficult to achieve.

I have heard large and very expensive speakers go boom-boom, but most do not provide that sense of mass, scale, and weight. Even fewer have proper integration with the midrange and tweeter to give the lower frequencies a sense of direction and the proper speed within a given recording venue.

The midrange is also very difficult to achieve. The goal of transparent, open, clear, deep, and beautiful midrange has proven the most elusive to put together within a single system. Some speakers do a couple of these, but it is unusual to hear all.

The treble, likewise, can be elusive. I am speaking about sparkle, shimmer, detail, openness, bite, and beauty. Plus, this has to be perfectly balanced as not to go too far into hyperdetail, harshness, and glare. It is a very, very fine line.

When you have it dialed in, the reaction is both visceral and emotional. Does the hair stand-up on the back of your neck, do you get a lump in your throat, does your heart flutter and melt, do your eyes tear-up?

I find midrange problems affect the sound much more than bass, speakers which get the midrange wrong can be intolerable. There is a lot more music in the midrange than in the bass area. I am quite use to listening to various amounts of bass as I have speakers with considerable bass and ones with moderate bass as well as 9 subs, some of which go below 20Hz. I am a great believer in the value of bass even in music that does not contain a great deal of low frequency energy but it is the midrange that makes or breaks the sound.