Project 582   Rockport Altairs, JL Audio Gothams, and the promise of killer rock n roll


This is a complicated and fascinating one. The customer had a home theater system, which he sold. He wanted to "go back" to the 2-channel audiophile route.

So he started visiting stores in Massachusetts, Rhode Island, Connecticut, New York, and New Jersey... he went in and said, "Let me hear your...$100k room..." And then they would play a lovely acoustic guitar solo at 70 dB. Then they'd play a lovely Chopin Etude at 80 dB. Then he said, OK, I wanna hear some damn rock n roll at 110 dB+ — put this Marilyn Manson CD on!" And so they did. And so he went from dealer to dealer to dealer — after all, this is a compelling hobby.

He then wrote carefully crafted letters (which were snail mailed...) to famous editors of famous magazines saying, "What the heck is WRONG with this industry? I go in these places and they are running ported speakers full range with the ports open and subwoofers in the corner with a lowpass on and nothing is aligned and there is no imaging and the bass is oatmeal and the kick drum is behind me and I can't understand the vocal..."

And he called me at JL Audio Tech Support and described these situations. Why is it like this? Why can't I go in to these supposedly high-end stores and hear a stunning, fulfilling system that reproduces all the impact I think I know is on the CD or other source?

And that's how this started.


So he was going to buy a head end system: CD Player and other sources, a preamp, a pair of monoblocks, a pair of main speakers, and a pair of Subs. He simply had his heart set on the brands he bought. And the premise was I would come and set them up -- as per the recommendation of these famous magazine editors: "...with your situation there's only one person who can set all this up for you the way you want with the patience necessary and that's Barry at Soundoctor..."

So he bought some rather interesting equipment. He has an Ypsilon pst 100 mk2 preamp; Ypsilon Aelius II Monoblocks, Rockport Altairs, (but no longer on the main Rockport website) a JL audio CR1 Crossover, and a pair of JL Audio Gotham Subs.

Just the overall left side !

I spent a full DAY discussing acoustics and showing him, with individual sine waves, all the places in his unusually shaped room where the subs SHOULDN'T go. Because he wanted the mains to go in an approximate area, it just turned out that if the subs were near the mains (to either side) there was unacceptably uneven low freq response at the listening position; we HAD to put the subs where they are, because he has essentially NO bass traps or other useful acoustic treatment in the room. The two half-rounds behind the power amps look cute but have virtually nothing to do with correcting or assisting anything acoustic.


Certainly the Rockports are gorgeous and the Gothams are magnificent. But because of the lack of appropriate acoustics, he did have, as many do, a distinct WAF issue in this oddly shaped room, and it wasn't going to help the audio results, either.

So first I/we listened to the Altairs by themselves, full range, to learn them. Kudos on the MAGNIFICENT phase alignment of the 3 drivers on the curved SLOPING FRONT: absolutely coherent out in space. This is no small feat. Playing my white noise tests were absolutely butter smooth. The white noise is almost a physical apparition out in space in front of the mains, and when you move your head, it is rock steady.

However, the inclusion of the 15" side-firing low freq driver (a "woofer", in their terminology...) might be OK for mere humans playing light jazz as their servants feed then wine and crackers, but killer rock n roll with stunning dynamics? Not a chance. In fact I don't see how there could be a power amp on this planet capable of reproducing that scenario with the speaker as it is. That LF driver is ported (so THAT'S wrong) and it rings, (partially because it's ported) so that puts out a back EMF voltage signal that MUST be soaked up by the power amp. This is called damping factor, and numerically is the ratio of the SOURCE IMPEDANCE of the amp's ouitput and the SPEAKER impedance.

Playing these things with delicate source material was glorious. Playing the variations of complex rock at anywhere near the levels that the customer wanted was a further exercise in disappointment, which he already had by visiting these many dealers who were fairly incompetent about real audio.

And therein lies the rub. Here's the ugly part... as I often put it when people ask: when you go to your Ferrari dealer, don't think for a millisecond that sales person is a Formula I driver. In the audio store, certainly with terrific exceptions, these sales people are not recording engineers, they are not mixing engineers, they are not mastering engineers, they are not film mixers, they MAY be musicians, but most likely have relatively little experience with real acoustic instruments and real music, and, as has been put forth by so many editorialists, know how to compare to the absolute sound of real 'stuff'.


So this requires a real explanation. Why do we NEED a subwoofer? Why don't any of these manufacturers ever give us what we WANT???

The published sensitivity of the Altairs is 91dB /w/m. Let's extrapolate to the real world and see what's wrong with pretty much ALL CONSUMER SPEAKERS WHEN USED LIKE THIS.

watts power vs spl and distance
watts level
at 3'
6 feet 12 feet
   1   91 dB   85   79
   2   94   88   82
   4   97   91   85
   8  100   94   88
  16  103   97   91
  32  106  100   94
  63  109  103   97
 125  112  106  100
 250  115  109  103
 500  118  112  106
 1 kw  121  115  109

Notice 1kw is greyed out because you're going to melt your speakers anyway... but just for educational reference...

So... if you are expecting to hear real world levels in your room at 12+ feet or so with just about ANY consumer/audiophile speaker you are simply not going to be satisfied. If we try and play that speaker full range by the time we get 103+ dB at our listening position for any length of time we are either going to clip the amp or cook a driver or burn out the crossover, etc.

Be aware that a real snare drum in your living room is about 115 dB average with at least 125 dB transients; therefore if we are to have HIGH FIDELITY we need to cleanly reproduce that transient. That is the real meaning of hifi.

Also be aware that many descriptions in audio are sadly misleading: EQ or "equalization" does NOT make everything "equal"; and the term "peaks" is very messy. There are real transient peaks, as in the snare drum example above, that may hit 145 dB for a few milliseconds, and there are "averaged out MUSICAL peaks", which may be 110-115 dB or so - it depends on the timing and weighting of the measurement tool.

In theory, you must also if you are going to push everything to the limit, take into account each drivers' sensitivity AND power handling capability...AND there's short term capability (transients) and long term RMS HEATING, like when you are having a Saturday night dance party and are playing your system at 105 dB for 7 HOURS and you heat up the voice coils so much you cook the drivers or the crossover circuitry or both.

I will review in gruesome detail this whole topic in my book, out 'soon'...


My general procedure is to place the sub at the listening position (you can push a Gotham around with one finger with the appropriate carpet furniture sliders) and both play music and sine waves. After doing this for some 40 years let's just say I'm used to it by now. I also do Ethan Winers' really cool test where you play a sine wave at any freq (70 Hz, for example) and you walk across the room in front of your chair from full left to full right. WITHOUT acoustic treatments you will hear probably a huge null at one or more places - sometimes that hole is 40-50 dB down.

So your room is this insanely complicated 5n dimensional calculus problem: Height and Width and Depth and Frequency and Time and the reflections and reverberations of all of that. In order to get the desired bass AT YOUR LISTENING position typically you MUST bass trap the corners. The more bass trapping you have in the corners — and most importantly, how low in frequency it is useful to — the more and cleaner and tighter bass you will have AT YOUR LISTENING POSITION. Why? because the more bass you soak up before it gets reflected the less there will be to either cancel (uneven frequency response) or reverberate (indistinct mush).

Imagine you are playing a dance track (your Saturday night party, remember?) and it is at 120 BPM. That means there is a bass hit twice a second. If the reverberation time (Rt60) in your room is HALF A SECOND, that means the first hit is not going to die out before the second hit comes along and so on, so your room is going to be muddy and indistinct.

So in some instances, (yeah, it's theatrical effect) I place the sub AT THE LISTENING POSITION and play every sine wave 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 (through the sub only) and walk /crawl around the room and put down colored dots on the floor at each place where you SHOULDN'T put a sub. This may seem trivial but once you actually start learning the room your brain will correlate the information quite well.

In this particular situation, especially because of the unusual shape, sitting distances, and asymmetric layout of the room it was something of a challenge.


We use my white noise test and very often I discover that many of these speaker companies splay the high frequencies over the listeners' heads when the listeners are in the sitting position. Maybe the manufacturers think this new generation of attention-span challenged millenials is going to stand up and wander around the room, so they want to average out the high freq splay. I dunno. But in most instances, we wind up lowering or even removing the front feet while raising the back feet, to angle or tilt the speaker further forward and downward until the white noise focus is in focus AT YOUR FACE, where it belongs. This further helps because now you don't have to play the tweeters (or the entire crossed over main speaker) so loud any more.

My white noise test has an accuracy of tighter than half a wavelength at (for example) 10k or 12k, (see my chart here: www.soundoctor.com/freq.htm ) so that's 1/2 inch or 1/4" PER left side and right side speaker. The larger the speakers are, the more critical not only the toe-in becomes but the tilt as well. A tall panel (Sound Lab A1, Magnepan, etc) type flat panel needs to be adjusted to better than 1/4" to get the holographic imaging you deserve.

You do all this with no subs. You should follow the instructions flawlessly! First you aim either speaker, say the Left. Then the Right. Then you do the out-of-phase test track and you will get a null in space where the white noise cancels. The more time you spend with this the more amazing your results will be. You can START with tape measures but once you get close THROW THEM AWAY - they are useless at these fine frequency adjustments. I have spent upwards of 2 full days aiming mains; once you learn the precision of my unique test you will wonder how anyone would not use it.

Now a word about that bugaboo, feet, rubber feet, spikes, platforms, etc. The real reason to use spikes is so your speakers don't move (or worse, fall over) on your carpeted floor if a kid or large dog hits them. IF you have wood or other solid floors please don't use spikes - especially if the speaker comes with good rubber feet.

Don't for a minute fall into the trap of thinking you are going to "isolate" your sub with "spikes" or anything else. There IS NO "ISOLATING". The sound comes out the driver and goes everywhere in the room. (Duh...) The only way you can "isolate" it is to turn it off. If something in the room is going to resonate (or piss your neighbor off) it is going to do that if the sub is on the floor, on spikes, on its correct rubberized feet, on a felt slab, or on your lap. And further, don't think that's going to help your cabinets from "vibrating". (a) modern sub cabinets don't vibrate; (b) even if they did, it would be 70-80 or more dB BELOW the actual desired sound, therefore it doesn't matter. PLEASE don't waste your money. If you have a real desire to spend some money hire me and I will set things up correctly for you. I guarantee it.


In this instance, knowing how essentially useless the low freq driver in the mains was, (especially at the desired killer levels) I decided to XO at 90. You ALWAYS want the HIGHEST XO freq you can get away with, NOT the lowest as some people incorrectly think. Just because you THINK your mains go down to 40 Hz DOES NOT MEAN you should run the mains full range and then XO the sub at 40. SO WRONG! But be aware, the higher up you go, the more the mechanism of your hearing can localize the sub in the room, IF the phase is NOT set correctly. If the phase IS correct you can even put the subs behind you and you will still perceive the musical bass to be in front of you because you are feeling the lowest notes from the sub but are localizing on the harmonic structure, which is coming out of the mains. The long wavelength bass waves cannot be localized because the wavelength is so large compared to your head... You start getting pristine localization at above about 880 Hz, which has a wavelength of 15".

I HAVE TO insert this audio mistake here... some people think "bass is non directional." WRONG! What they mean to say is "bass is non LOCALIZABLE by the mechanism of your hearing."

So we feed a 90 Hz sine wave into the system. This is the ONE PLACE you CAN use an SPL meter: measure the Left main separately and the Left sub separately and set the result level at 1 foot away to be the same. Now hide your SPL meter - it's now useless.

Reverse the wiring to the main speaker, so you think it's "out of phase" WRONG AGAIN! It's actually OUT OF POLARITY. (Read my subs white paper carefully...) Now we slowly adjust the phase knob on the Gotham to null the audio AT THE LISTENING POSITION. Clearly, this takes two people who are both prepared to be insane for some length of time. "...Up, up, up, up, no stop, down, down, no up, up, no down, no stop right there... no, wait, up, up..." Unfortunately JL Audio does not YET have a nice phone app to do this, so it takes 2 people since you really must listen AT YOU LISTENING POSITION.

In SOME instances where the sub happens to be right next to the main speaker, yes, you can position your body right in front between the sub and the main and the knob (fortunately) is in the front of the sub; some other brands have the phase knob in the back, so it's really difficult. Be aware that the phase null is ABOUT AS SHARP AS THE WIDTH OF THE POINTER ON THE KNOB.

You have to do one full test with the sub's POLARITY SWITCH at 0 and another full test with it at 180. You finally choose whichever switch position gives you the LOWER NUMERICAL reading on the phase knob.

Once you are done with the Left side, you put the speaker wiring back where it belongs and then turn the entire left side Off. On the CR1 crossover I have placed MUTE switches to make this very easy. These mute switches are also VERY USEFUL if you have something vibrating in your room: you simply mute the mains it makes it easier to hear some anomaly. See the pix.

CR1 mute switches for convenience


So after some 3 DAYS of setting up and tweaking, we were finally ready to really play some full music on the full system.

When setting up, I usually use the Techmaster PEB tracks for the subs, the super clean and SEPARATED Holly Cole for female voices, and Boz Scaggs Thanks To You and Skylark for male vocal and presentation. I've been using Holly Cole for 27 YEARS - I think I know it by now, and once you know something that well it becomes easy to pick out any difficulty, even if very subtle. So the customer put on one of his references: the Marilyn Manson Pale Emporer. Well, it was BONKERS. It was STUNNING. It was kick you in the stomach with sharp steel-toed boots focused. The customer was overjoyed, and he kept saying, "So why can't I go into a stereo store and hear this?"

And once again, I am very proud that my focused efforts gave the customer exactly what he had been seeking for YEARS.

There is no plug-in for experience...
SOUNDOCTOR                  BARRY OBER                 336 347 7002                  EMAIL: barry@soundoctor.com