PSB Alpha System Setup

Next I tried them on the outside of my speakers which put them closer to the absorption panels but kept them quite far apart. Finally I placed the T1's in front of mine and even took it one step further. I put an absorption panel on the floor right next to the speakers to absorb all early reflections. I did this because the lower mid-bass driver would have reflected sound while the upper one would be absorbed which you can see from the picture. I tried all of these different positions to ensure that these speakers were heard in the best possible sound field. It was very time consuming but in the end I wanted them to sound their best. When owning a pair of speakers even more care should be taken to find their best position. The lack of fatigue will be well worth it. You'll also notice that I placed them on a piece of wood. The T1's come with both spikes and rubber feet but with the thickness of my carpet the spikes were not long enough to make it to the concrete so I put on the rubber feet and placed them atop the wood.

This position had them still a little far apart and I was concerned with the affects on the sound stage and imaging but this turned out alright which I will discuss in more detail in the Listening section of this article. When I needed to listen to my own speakers I just left the pieces of wood and moved the T1s out of the way. It worked out well because of the speakers - light weight. If these were a real heavy floor standing speaker I probably would not have played around with the positioning as much. I'll chalk this up to an advantage of having a lighter speaker.Next up was the Alpha C1 center channel speaker. This one was obviously a lot easier to set up. It went in the center but how far back was the question. For music it is best to have all five speakers set up in a circle around the main listening position but that is rarely possible. That is why receivers and processors have speaker distance settings, so that the proper delays are created. I set the C1 center speaker up directly in front of my center speaker on a stand which was further back from the right and left channel speakers and it stayed in the appropriate circle. I placed it on a stand with the towel to keep it from getting scratched.

The surround speakers were placed on a shelf in place of my existing surround speakers. Surrounds are usually not able to be kept in a circular arrangement without having a very unusual or circular room. For movies the sound of the surround speakers should be diffused or indirect. For multi-channel music the sound from these speakers should be direct but also at ear level and approximately 110º behind the listener. It is nearly impossible to have an ideal set up for both movies and multi-channel music using the same speakers, though some systems allow DSP modes (think THX' ASA) or bipole/dipole functions to help. Typically, though, a compromise must be made and you should lean toward what you listen to more, movies or music. I simply pointed the B1s at 45º toward the back wall to create a somewhat diffused sound for movies.

As I have recently learned and now experimented with, subwoofer placement is probably the most important speaker placement. I was pleased to see that the folks at PSB know this and print it in the Owner's Manual for the subwoofer. The manual shows that if you want maximum bass output to place the sub in the corner of the room. However, this placement excites all the room modes to their maximum output which creates large peaks and nulls. So while you may hear some loud bass at some frequencies you will hear nothing at others. It also states that with the nulls, no matter how much you turn up the gain you won't hear frequencies in the null because it is a product of the room and the seating position. The manual even talks about the 180º phase switch helping in certain situations. An important point to make here is that if the crossovers in the system are set up properly with no overlap in frequencies, the phase switch only helps at the crossover frequency, usually 80 Hz. In other words a cancellation can occur between the main speakers and the subwoofer at the crossover frequency and the phase switch will eliminate that cancellation. Without measurement equipment you can probably hear that difference with a test tone at the crossover frequency. The manual goes on to show that to smooth the bass, moving the sub along the front wall toward the center of the room will give a moderate output but more even. To make the response more even the manual shows moving the sub away from the front wall and into the room. The funny thing is that the picture in the manual is very close to where my bass placement tool puts the sub which I will show shortly. I am not sure why the sub would ever be kept in the corner (although I naively did it for years) for maximum bass response when getting an even bass response (much more important) can be achieved and then the gain controls can be used to boost the output.

PSB only sent one subwoofer to begin with and I did not follow the manual's method for finding the best position so I can neither confirm nor deny that it works. The manual follows our recommendations in our "Crawling for Bass" article and says to put the sub in your seat, crawl around on the floor to find where the bass sounds best and then place the sub at that position. Instead I went straight to the sub placement tool that I received from HAA. Here is a snapshot of the result.

The tool shows axial modes of two dimensions relative to the seat position. Why two and not three? Well, if you think about it how many people place the sub off of the floor?! You can see in the picture the pink box represents the sub and it is 53" from the front wall and 156" from the right wall. Take special notice to the "Seating Relative Mode Level" curve; those are the peaks and nulls and that's as smooth as I could get it with one subwoofer. This position is not an aesthetic one and everyone would be tripping over it.

PSB eventually sent another subwoofer (they even recommend using two in the Owner's Manual). The manual states that two subs not only give an increased output but also smoothes the response better than one sub. Now look at the response for 2 subs. Remember that above 80 Hz the response doesn't matter because that is where the cutoff frequency is of the subs. You can see how much smoother the response is for 2 subwoofers and that they are now both against a wall. These positions should not change no matter what subwoofers are used, but to really tweak it, Real Time Analyzer measurements should be taken. I did not use the subwoofer crossover; instead I let my processor do the work via the subwoofer output. Finally, I set all speaker levels using a Radio Shack SPL meter and all distances accordingly.