Infinity Alpha Series Review

The Infinity Alpha series may take a significant portion of your home theater budget but it is well worth it...
The Infinity Alpha series may take a significant portion of your home theater budget but it is well worth it...
The Infinity Alpha series may take a significant portion of your home theater budget but it is well worth it...


  • Excellent sound reproduction


  • Rear speakers are lacking at lower volumes


The Alpha series from Infinity represents the middle of their product line and provides a nice compromise between price and functionality.  The models provided for review include the Alpha 40 mid tower loudspeakers, Alpha 25es for the surround sound speakers, the Alpha 37c center channel and, Alpha 1200s powered subwoofer. The front speakers are about $800 each, the center abut $400, the surrounds about $350 each and the subwoofer about $800. So the reviewed setup would cost approximately $3500 at most retail stores. These speakers are not really intended for the smaller room but if you have the space and the budget to go with individual pieces rather than an all together set this should be at the top of your list.


Infinity Acoustics is part of A Harmon International and is known for both home and car audio. The Alpha series reviewed here occupies the middle part of their home audio product line and provides both an esthetically and acoustically pleasing array of home theater speakers. The design philosophy behind the Alpha series is to make sure their speakers are a neutral part of your home theater, neither adding to nor subtracting from the audio information contained in the source.

While many people, especially those new to home theater, will prefer the complete set of six speakers as one set, the advantage to buying the individual components is you can build up over time and still stay within a reasonable budget. The Infinity Alpha series may take a significant portion of your home theater budget but it is well worth it for the performance you will receive.

Design and General Features

The Alpha models I reviewed were all black veneer, they are also available in Beech or Cherry finishes. My first impression after getting them out of the six huge boxes that dominated my home was ‘they look great’. They are sleek and will satisfy those in your family who consider how well a piece of equipment fits into your room. I know this is very subjective but they had the heft of a good quality speaker, they just feel well made, they will last for a very long time in your home. You will most likely have to rearrange a lot of furniture to accommodate them but the effort will pay off when you fire up the amplifier and sit back to listen.

All Infinity Alpha speakers employ patented Ceramic Metal Matrix Diaphragms (CMMDâ„¢). This provides a clean, clear sound with almost no alterations from the audio source material. This is accomplished by minimizing the strong resonances found in some speakers that can adversely affect the timbre of the reproduced sound. The use of a ceramic cone instead of the industrial standard metal gives a stiffer material that better resists alteration of the sound and permits the individual speaker to reproduce only the sound in its targeted set of frequencies, high for the tweeters, mid range or low for the woofers. The sum affect of all this is the speakers provided a sound that never seemed muddy or overly bright. I noticed the difference immediately when I switched to the Alphas from my trusted set of JBL speakers. I’ve used JBLs for decades and have always considered them my preference, I guess I have to change that long held opinion after all this time. Of course, all the speakers in this series are magnetically shielded. While many will think this is only important for the center and front speakers that often come the closest to your television set, adding the shielding to the rear and subwoofer makes sure if you place them a little too close to your VHS collection (yes I know many of you have tapes of favorite films not out on DVDs) the tapes will not be degraded. This is just typical of the attention to details that Infinity incorporates into their designs.

The main front speakers, the Alpha 40 model, are configured as floor standing towers. Each contains a one inch dome tweeter, a 5 ¼” mid range and dual 6 ½” woofers. All four speakers employ the CMMD technology. The edges of the cabinet are curved providing a nice, modern look to the speakers. They are ported at the bottom of the cabinet. The first thing most of you will notice when setting up these speakers is they are configured for ‘bi-wire’ or ‘bi-amp’ connections. There are two sets of connection binding posts, one marked high frequency, and the other low. This permits you to use different connections for the upper and low frequency speakers or if you have them, different amplifiers for the low and upper ranges. In case you just want to use one set of wires to make the connection the gold plated posts come with a little flat metal connector to pass the signal to both sets of posts with one connection. The speakers are rated for 10-150 watts and provide 45 Hz up to 22 kHz.

The rear/surround speakers are the Alpha 25es. They are mountable on the wall or can easily fit in a bookshelf or stand. The first thing you will notice about them is they are angled; the four speakers contained in the cabinet are set at about a 45 degree angle for maximum dispersion of the sound. The lower frequencies are handed by two 5 ¼” CMMD drivers, one on each side of the angle, while the higher frequencies are processed by two 1″ CMMD drivers. One nice little design touch is the speakers on the left side have the larger driver on top, the ones on the right have the larger driver on the bottom. Supposedly this is to help make sure all frequencies are equally mixed for the listeners. For optimum performance in any level home theater you can use these speakers in one of three modes: bipole, monopole or dipole. The provided recommendations are as follows. If you are mounting the speakers more than 14″ from the listening position or they are mounted near a corner use the monopole setting. For those systems with THX certification and the THX surround mode is selected or with older Prologic only receivers, use the dipole mode. For most other installation situations the bipole mode is recommended.  Bipole is also recommended if you use these speakers for the rear center speakers in a Dolby EX or DTS ES system. These speakers can handle power from 10 to 125 watts from 60 Hz to 22 kHz.

Features Continued…

Holding its place in center stage of your home theater is the Alpha 37c. This center speaker is a full frequency three way unit capable of reproducing not only the dialogue but every sound pushed into it. There are dual 6 ½” CMMD woofers, a 4″ CMMD mid range and a 1″ CMMD tweeter. Rated for 10 to 150 watts this speaker will handle most home theater systems. The audio frequency for this unit is a respectable 45 Hz to 22 kHz. Although the speaker weighs in at 32 pound it can be wall mounted.  With most configurations of your system you will find placing the speaker directly on top of or in front of your television set the best.

Now for the big gun of the system, the Alpha 1200s sub woofer. This 45 pound unit is as big as a typical end table. It contains a single 12″ CMMD sub woofer speaker. What sets this sub woofer apart from so many of the others out there is the plethora of options available to customize the sound to the acoustics of your room and the particulars of your receiver and speaker setup. Even though ultra low audio frequencies are difficult to locate with your ear the instruction manual provides a little tutorial on how to properly place the sub woofer in relation to your other speakers. As with other Infinity manuals, ample diagrams are provided. Most of you are going to be impressed with the back of this sub woofer. While most sub woofers have a simple plug for the connection and a dial for the crossover frequency this model is packed with switches, dials and connection terminals. If you do not have a discrete six channel receiver you can connect the sub woofer in line with your front speakers. For this you use the set of eight binding posts. You run the wires from the front speaker outputs of your receiver to the sub woofer ‘IN’ posts and then from the ‘OUT’ posts to the respective speakers. This method permits the sub woofer to intercept the very low frequencies from the signals to the main speakers, based on the setting of the crossover, and process them with the sub woofer. This method of connection will mostly be used by those out there that are building their system and have not yet moved up to a full 5.1 sound system. For those systems with a LFE sub woofer channel you can run a cable terminated with an RCA jack to the two RCA connectors on the sub woofer. You will need a ‘Y’ connector since most receivers only provide a single LFE sub woofer output. Now the fun begins for those of you that enjoy playing with switches and dials. There are three switches to contend with, a phase switch for 0 or 180 degrees, a low pass filter set to either On or Off and a power standby switch. There is also a main unit power switch. For systems using DTS the receiver will control the low pass range and the switch should be set to Off. You can also avoid the need for the ‘Y’ connector with the RCA plugs for DTS systems and connect the single LFE cable to either the right or left input. The crossover frequency, the frequency where the sub woofer takes over processing, can be set from 50 to 100 Hz for most systems or between 120 – 150 Hz with systems using smaller rear speakers that do not contain a woofer. The gain control sets the volume for the sub woofer and the width control sets how wide a sound field is created. These are typically “Set once functions”, but the initial set up should keep you entertained for a couple of hours.

Running them through the Gauntlet

Many reviewers like to use testing equipment to gauge how well a set of speakers perform. I prefer to trust the most sophisticated test equipment possible and the one most important to everyday use, the human ear. Rather than trusting graphs and wave forms I would rather judge a speaker by how it actually reproduces sound for me. To this end I have a set of DVDs, CDs and cable stations I use to test the performance of speakers. To test the crossover frequency of the sub woofer I chose a music video station. The pumping bass lines of much of modern music were well handled by the sub woofer as well as the woofers in the main speakers. When I tried the speakers out on some music CDs the response was crisp and clean. The highs were brilliant and the bass lines booming without over powering the rest of the audio spectrum. Another way I tested the full frequency of the main speakers independent of the sub woofer was with the first episode of the first season of the Sopranos. It opens with a full version of Frank Sinatra singing ‘It was a Very Good Year’. Since this song features a full string section and some woodwinds it was perfect to hear the whole spectrum. The bass was clear; I could hear the individual strings. The violins where not muddied by the lower frequency, they remained distinct. With all tests I put the front speakers through, they performed better than the usual three way JBLs I have in my home system. They delivered true highs, a strong mid range and a steady bass line. Each sound reproduced was done so without any noticeable coloration. It did seem that the ceramic design made a notable difference. Each range of audio was audible and remained individual

The center speaker was among the best I have ever tested. The dialogue appeared to naturally come from the characters on the screen. The addition of a set of woofers and a tweeter provided a more natural timbre to the voices. I did have to dial down the volume to the center speaker during calibration with Ultimate DVD Platinum (a DVD used to make sure your home theater is performing at its best). Without careful calibration the center speaker had the tendency to be a bit overpowering, resulting in too much coming from the center rather than giving the feeling of a smooth, integrated part of the sound stage. To test this I tried several films where there was a lot of dialogue over a background of a good deal of action. The Lethal Weapons flicks were great for this. When properly set the dialogue was clean over the background action.


Next let’s take a look at the surround speakers. With discrete sources like DTS and Dolby 5.1 the rear surround speakers added to a full, crisp audio field. All frequencies where well reproduced. For these tests I went not only to the typical high end action flicks like The Matrix, Gladiator and ID4 but also films where the musical sound track employed the rear speakers. Here I choose Red Dragon and the up coming release of Chicago. In all cases the sound from the rear was full. With DTS titles the rear portion of the sound stage was very well blended. The only down side of these speakers was at low power. Because of a crazy work schedule I work at very odd hours and because I want to keep on good terms with the neighbors I have to keep the volume low. At these lower settings, the rear speakers almost disappeared. Although rated to go as low as 10 watts I had to push considerable higher to get the speakers to really work. This was also the case with matrixed surround sources like Prologic and the various emulation modes. Other rear speakers were loud enough to contribute to the overall sound field but here the rear speakers where all but mute.  Once again proper calibration was able to help but if you watch a lot of Prologic discs or television the gain will have to be pushed on the rear to really enjoy the set.

The sub woofer is a monster. You will realistically need a good size room to place this speaker properly. To test this I used sources like Pink Floyd’s The Wall. The sub woofer is active almost throughout the film and pumps out very low frequency. Unlike some sub woofers this one did not distort at all. The lows where booming without causing the speaker to rattle at all. This CMMD idea of theirs really paid off here. The stiffer speaker was able to take all that I could dish out without any break up to the sound. The room shook during battle scenes like Star Wars and Gladiator. This sub woofer did its job and provided a visceral experience that pounded in the chest. Try the blast off from Apollo 13. I had a friend listen, one that actually watched a few lift offs and he said it was the closest to the real experience he ever felt. With a maximum power of 500 watts you will most likely never stress this speaker; objects will fly off the shelves before you even approach the max here. There is a downside, a price to pay for this perfect combination of sound and tactile experience. All the switches and dials have to be perfectly set to get the most out of this massive sub woofer. For those of you out there that just want to plug in the AC power, connect the audio cable and turn the speaker on, you might get a bit frustrated. It took me about an hour with a calibration DVD and the manual to get the unit to the point of being able to hear any realistic sound. Since some of the recommended settings for Dolby 5.1 and DTS where different I had to work at some compromises in order to avoid having to open the front panel of the speaker and changing the settings when I switched from one audio format to another.


Except for the few noted points, the overall performance of these speakers was incredibly good. If your primary source of audio is from discrete DVDs then this is the way to go if you can afford the set. While the surround speakers where not great for Prologic sources these speakers more than did the job on DVDs. Get a calibration disc to make sure you have your speakers properly set for your room’s acoustics. They look good with the black finish and will fit into any room’s décor, a major point for some of our significant others.