Intimus 522D-PT Design and Setup

The top section of the Intimus tower was comprised of a paper poly treated 5 ¼" midrange driver and 1" soft dome tweeter. The 8" long throw subwoofer appears to be of rugged design with its 1.05kG magnet.

The 1" soft dome tweeter contains a neodymium magnet structure. While I am normally not a fan of these tweeter designs because they often suffer from thermal compression, I took close note of the heat sink strapped to the back of the magnet assembly. Obviously the engineers at Aperion Audio were quite knowledgeable about this issue and attempted to address it.

In fact, I seemed to recall reviewing a similarly priced British loudspeaker a few years back that utilized a lesser designed neodymium tweeter with no heat sink, and received rave reviews like "just buy them" from other magazines. I also recalled how compressed and boxy that speaker sounded, especially at higher volume levels.

I was unable to pull out the 8" side firing subwoofer for a closer look, since it didn't have readily accessible screws and I didn't want to risk damaging it with my prying hands. However, using the midrange and tweeter as an indication to the quality of the drivers Aperion Audio utilized, I wasn't too concerned with examining the motor structure of the subwoofer.

When I pinged Aperion Audio for some design specifics for these powered towers, I was promptly showered with technical info from their designer.

Crossovers (All slopes are the actual measured slope of driver's outputs. This involves drawing in the asymptote by hand and measuring it. So these slope #s will give you the phase but not power transfer functions)

Active LP slope on 8" sub is 12dB/oct

Passive HP slope of 5.25" driver is also 12dB/oct

Crossover freq is 110 Hz and is the -10dB point of both drivers

LP slope on the 5.25" is 8dB/oct

HP slope on the 1" tweeter is 12dB/oct

Crossover freq is 2000 Hz and is the -9dB point of both drivers

The 5"-to-tweet crossover is a series type it is also "DiAural", which simply means that the series C to the tweeter is replaced by a resistor.

My initial concern here is that most series crossover designs featuring the DiAural crossover dump too much power across the tweeter which can lead to dynamic compression and distortion - the exact opposite goal of the circuit intent. When the resonant mode of the tweeter is near the crossover point, this problem can be amplified. In this case however, the tweeters resonance frequency is at 1kHz. Since the high pass (HP) filter of the tweeter is not the typical shallow 6dB/Oct slope common in most series crossover designs, the tweeter's power response is nearly 20dB down at its resonance mode. This consideration, combined with the properly heat sinked magnet and ferrofluid cooling of the tweeter, should alleviate most of these concerns.

For more information on crossover types and detailed simulation comparisons between series and parallel crossover networks, you may wish to review the following articles:

Crossover Types

Series vs. Parallel Crossovers

It's not often I review loudspeakers with integrated powered subwoofers; and I often do so carefully realizing there are advantages and disadvantages to this design approach. The advantages can be convenience, space saving, and cost effectiveness to the consumer. The disadvantages are that you have now limited your placement of the subs to where the mid woofer/tweeter sections reside. This can be problematic for those who have nasty room modes that can only be cured by relocation of the subwoofers, listener or some type of parametric low frequency room correction. Usually the most effective option is relocation of the subwoofer(s) to a null position in the room or moving them ¼ wavelength from the coupling surfaces of the primary room modal frequency. Another consideration of multiple subwoofers is the potential problem of path differences between the subs and the primary listening position. These are all issues we must address with any large bass capable speakers, but they become even more involving with powered towers such as these when used in conjunction with other subwoofers in a system.

In my review application, I focused on two-channel playback with no additional subwoofers in my system. In reality, I suspect most buyers of a system like this will rely on the Intimus system to serve as the LFE channel (and rightfully so, as you can see in my low frequency measurements in Figure 3.) by simply rerouting the bass management of the receiver/processor as tabulated below.

Note that the Intimus towers have no line level connections for the side firing subwoofers, thus it is not possible to route line level subwoofer connections from your receiver/processor to the speakers which is one of the reasons why I recommend the connection method and bass management configuration I suggested.

I found the best sound in my listening room for these speakers was placing them about 3 feet from the side walls 2 feet from the back walls with a slight toe-in. I did some comparative listening with the grills on/off and heard little difference so I opted to leave them on. At times I actually preferred the grills on which I suspected was mostly psychological since I thought the speaker system looked more elegant.

I was a bit disappointed that there was no variable phase adjustment on the powered subs, but I was equally thrilled that I did not run into bass integration problems when I set this system up. After a few times of going behind the speakers for bass level tweaking, and re-measuring their bass response at my listening position, I was done (see Figures 1-3 ).