The Mighty Magico with the Equally Mighty JL Audio Subwoofers

Posted by Tan

 This home visit stands out as one of the most memorable in my experience at 3 different levels – the sheer size and quality of the system, the meticulous care and attention the owner, Mr. Soo, put into setting it up, especially in the bass region, and its final sonic performance.

When I first saw this system, the question that came to my mind, which would also be the question many audiophiles have, was whether full-range high-end loudspeakers like the Magico M6 need to be augmented with subwoofers, and whether they can integrate successfully, Furthermore, it was with not one but two subwoofers, both being the massive JL Audio G213.

The system owner, Mr. Soo, had done a tremendous job. Before I get into the subwoofer matter, let me first say that the sound performance of this system was beautiful, and I meant this quite literally. The sound was refined, from the first song on, I could detect no graininess anywhere at all. The highs were silky with a smidgen of sweetness, the midrange was pure, together they rendered female vocals rather intoxicating and seductive. Transparency was top notch, the sound was wide open with clarity and high definition details. The soundstage was well formed both in width and depth, aided by  the room size and skillful speaker positioning. There were lots of air and ambiance, likely enhanced by the subs. Image focus and definition were excellent, the kind that you can “look” at and pinpoint.

As a testament to the match between the CH Precision amplifier and the Magico M6 loudspeakers, the delivery was always well in control and well defined. There was a gentle touch and civility in the presentation throughout, letting the listeners enjoy a cultured and relaxing experience.

Now, about the subwoofers: The integration was so seamless that it was impossible for us to tell where the Magico ended and the JL Audio subs began, such was the seamless integration between the two. The subs were working for sure, providing a firm anchor on the bottom end, with good body on the sound and no thinness.

Bass boom is one of the if not the biggest bane for a HiFi system. It diminishes our system’s ability to deliver music enjoyment, limits the kind of music that can be played, and in the worst case makes some audiophiles give up the hobby altogether. Bass boom is difficult to treat, so some find peace with the situation by narrowing their music selection, playing music that won’t excite the room; some switch to smaller loudspeakers with less extended bass to avoid the frequency that causes the boom problem; some may just resign themselves to live with the boom issue; some even take boom as impactful and thunderous bass performance.

Still, many decide to take the problem head-on, taking the route of acoustic room treatment, or go the electronic way by resorting to DSP, or a combination of methods.  

Mr. Soo did face the bass boom issue with his listening space, so he devised his innovative approach to solve the problem, which he generously shared.

Here is where the subs come in. The first point is that the two big JL Audio subwoofers were not there to add more or to extend the bass from his Magico M6 loudspeakers. The Magico M6’s positioning was the best for every aspect of stereo performance already, so loudspeaker positioning could not be used to further address the boom issue. Mr. Soo’s method was to split away the frequency range that caused problem from the main speakers and used the subwoofers to recover it. An active crossover from JL Audio, the CR-1, was used for this, the crossover point was set at around the 40Hz region, with the high pass going to the power amp driving the main speakers, and the low pass going to the 2 active subwoofers.

Once that was done, he had all the freedom to deal with the offending frequency range via subwoofer positioning and tweaking the volume and the phase setting (the crossovers on the subs were not in the signal path, they were set to max). Using two subs, instead of one, allowed him the freedom to find the best position for each channel. Indeed, we saw that the final positions for the subs were not symmetrical. The subs’ phase and volume setting also ensured that they were integrated seamlessly by avoiding cancellation or addition of sound wave.

The 2 subs placed close to the left and right walls with different distance from the loudspeakers and listening position

Mr. Soo did not do all this with only his ears, he did a lot of measurement on REW of his subwoofer setting effort over many months.

This is the most extensive and innovative way of using subwoofers that I ever came across, and the owner’s effort paid off handsomely. The sound was full range with rock solid bass extension, the dreaded bass boom issue was totally banished, and the subwoofers just ‘disappeared’. Bravo to the owner for a job well done!

Experiencing the Designer’s System – Frank AB2 Tower Sub

 Posted by Tan

It’s rare to have a chance to listen to a HiFi designer’s own system, but if one ever comes along, we should seize it, as it offers us an insight into the designer’s personal listening preference and, not least, how far the designer’s own product could be pushed.

So when Frank Voon, the owner and designer of Frank Acoustics invited me to listen to his system in his new home, I jumped at it. Frank’s system was set up in a dedicated rectangular listening room, with the main focus on his Frank AB2 Tower Sub.

The Frank AB-2 is essentially a passive subwoofer in tower form, mated to a bookshelf loudspeaker of your choice. There is a 'cutout' in the middle of the tower to accommodate the bookshelf speakers (you can get more information on the Frank AB2 Tower Sub here and here).

Frank’s system was straightforward, consisting of a TEAC streamer, a Marantz disc player, a preamp and a power amp. Of course, he also had a few Frank Powerbanks installed, though they were placed close to the distribution box rather than in the listening room. From the photos, you can see that getting the room acoustic right was also important to him, thus the absorbers and diffusers that were placed at various strategic positions.

The loudspeakers were placed well apart from each other and well into the room, slightly more than halfway of the room’s length. This created one of the most memorable characteristics of this system, which was its soundstage. The soundstage was detached from the loudspeakers, wide and deep (with more sensation of depth). Centre imaging and solo voices were placed far into the stage with their positions almost right at the front wall, and the ambient details extending beyond the front and side walls. This would be an uncanny sensation for those who are unfamiliar with such an experience, especially among the non-audiophiles.

Image focus was well defined, and imaging was well delineated, and with excellent depth perception, layering was very well done too. The sound was not voluptuous or fat despite the bass and volume capabilities of the towers.

Overall, the music delivery was, well, musical, with a grain-free treble region and an articulate midrange. It could do sultry vocal and dynamic attack. The bottom end created a solid foundation for the rest of the spectrum to play on. I appreciated this balanced approach Frank applied to his system, avoiding the temptation to boosting the bottom end just to showcase the AB-2’s bass prowess.

The power amp Frank made for his own use. Unfortunately, Frank has no plan to commercialize it yet.

Indeed, I believe these Frank AB-2 bass towers could extend the performance envelope of any bookshelf loudspeakers they are paired with (you can also request for Frank’s custom made bookshelf speakers to mate with the AB-2, which was how I heard them during this visit). If you want floorstander performance but loath to give up your favourite bookshelf speakers, consider the novel Frank AB-2 Sub Tower perhaps. You may be pleasantly surprised!

Contact Frank Voon for enquiries, +60122981011.

Multi channel calibration

On the topic of multi channel calibration is mainly focus on Home Theater although there are multi channel audio as well for hifi audio. In my post will be focusing on Home Theater and will be doing the 11 channels plus subs for calibration. That will be 7.1.4 configuration in the standard Home Theater setup. Picture as below to illustrate the Dolby or DTS recommendation of setup. The good thing about this standard is the flexibility to reduce the number of channels or speakers based on space available and also room configuration. Although most modern receivers or processors for Home Theater can easily compensate on the placement of speakers and subwoofers but is still recommended to follow the guide line as per picture to maximized the result of the audio. Distance, angle, height, etc for any speakers or subwoofer will impact the end result. 

For the calibration there are some basic tools needed. Most receivers and processors do come with some microphone for calibration but are not too accurate unless the processors are some high end brands. The microphone use in this calibration is the umik-1 from a company in Hong Kong (Minidsp). Very affordable and accurate as the company of Minidsp calibrate each microphone individually before it is send out to the customer. So a calibration file will be included for individual microphone. This will be use with the calibration software during measurement. 

Next piece will be the software I am using is the REW or Room EQ Wizard, is a very powerful tool and is a freeware but you can purchase it with some advance additional features. For basic calibration it is good enough to be use. REW can be use to measure or calibrate audio for home or even car. It can 2 channels or as many channels as 13. Versatile software and easy to be learn. 

Will be recommended for some microphone stand which is easier to swing around the microphone especially for multi seating calibration. Some will just use camera tripod which will work as well. As long as it can hold the microphone 90 degrees pointing up upward. This is important as surround sounds comes from multi direction and having a microphone pointing up will have the best possible receiving of the signals for accuracy in measurement. Umik-1 microphone has 2 different calibration files provided by the manufacturer for 90 degrees and 0 degrees angle measurement. 

For the start and most important basic to get right is the volume or SPL output. Each speaker and subwoofer in most standard receivers or processors will be able to dial in to the right volume. The simple reason why this is critical , when multiple audio sources playing together or one after another will be pretty noisy simply. More over, different sizes of audio devices will produce different output. It can overwhelm one another. To avoid all this, the balancing act of all channels with the right volume is crucial. The typical example of conversation in a movie can be very soft and explosive scene become too loud.

To perform this step, simply turning on the test tone for the receiver or processor. Measure the test tone in term of SPL. The guidance from Dolby will be using 0 db master volume as the reference level for testing out the SPL. To measure the SPL , it can be done with the Umik-1 and the REW software which provided the SPL tool. Another way is using third party SPL meter. Picture as below

Dolby or DTS reference is 75db reading on the SPL with master volume set at 0db. Simply, this is the guideline use for sound engineers in the movie industry in their mix and recording of the movie. This reading will be across all channels including the subwoofer. This important point to take note of will be LFE (Low Frequency Extension ) or bass on the low frequency are boosted by 10db according to Dolby and DTS standard. So to achieved same 75db level , the subwoofer need to be 65db at 0db on master volume. This is the only exception for all multi channel calibration.

Once levelling is done, the next step will be setting the cross over from low frequency to high frequency. In Home Theater context, it will be 0hz to 250hz as low and above 300hz to 20khz will be high frequency. To work on this Dolby and DTS has determine to be best at 80hz to cross between the high and low frequency. This is a general guide line as the dependency will be on the speaker and subwoofer capability to reproduce the certain range of frequency. Typically a subwoofer will be able to handle 20hz to 100hz. For speaker generally 50hz to 15khz range. Taking the upper limit of the subwoofer and the lower limit of speaker, therefore 80hz is the ideal point to crossover. 

The next critical step will be bass management. This is referring how to smooth out the bass in the Home Theater setup. In any Home Theater setup, bass is very important aspect after the vocal of the movie. In any audio setup, bass is something cannot be miss. Using the REW and Umik-1 the measurement of the subwoofer from 0hz to 200hz frequency range will help to determine the ideal output. Again the reference here will be 75db. The basic idea is to get frequency range of 0hz to 200hz as close as possible to 75db. This is the flat response ideally to get the audio frequency spectrum not to be miss out. Below graph to illustrate on trying to stay close to the flat line.

The placement of the subwoofer is important to get the best out of this. There is no scientific way of placement but will have to move around the subwoofer and each placement take a measurement to understand what is the result. The average will be to avoid peak and dip in the result. Peak can create boominess and dip will be totally not hearing the sound. Other than placement of the subwoofer, the tuning on the delay or distance of the subwoofer in the receiver or processor will also help in getting the flat measurement. In real world scenario, is impossible to get to the ideal respond but will be as close as possible. Multiple subwoofers in a room will also flat out the response as each subwoofer will be able to compensate each other. The basic steps are something very doable for most home users. Spending some time for this will definitely bring out the potential of the setup. After this final step is done, you are all ready for enjoying the movie.