[audioferret]

This is the post I placed on AV123's forum helping people use RDES in their system.

 In this combo, I used the HT2's I recently reviewed on loan from Al along with a Kenwood 150W subwoofer that I have (Better subwoofer under construction). 

[audioferret]

It took a while, but I slowly got the hang of tweaking the RDES in my basement theater.

I am using a $150 Kenwood Sub I got about 6 years ago. 10", 150W. Room is about 13x11x8 (pretty small).

I have the receiver set at -20 below ref and the mains are powered by a separate, integrated amp. This allow level matching to be done on the sub and mains separately, with a third master volume to manage the whole setup once correct.

The bass is sooooo much better this way.... (see below)

Sub Only (After hours of positioning)



- Yes, it is hard to call it a subwoofer, but I have a certain 12" servo sub kit in my dreams that goes down to 10Hz in-room...

HT2 Mains (After hours of positioning)



Sub and Mains with EQ (75dB crossover, 12dB slope)



As you will note, except for the null (phase related, I think) I have +/- 4db from 100dB down to 30dB.  I can get this to improve, but I stopped due to spousal constraints.  ("Ok hon, this is getting annoying...")

I keep tweaking, and it gets flatter, and flatter...

[audioferret]

Optimizing the frequency response is an art form.

Step 1 - Get the Room right.
I have room treatments at the side and rear reflection points for my mains and a pair of corner traps in the front right corners. I made them using the method described in:

http://www.audioholics.com/techtips...rsacoustics.php

They worked very well at improving the sound of the room. Images are much clearer now.

Step 2 - Get the Mains Set Up
I used the Rives Audio Test Disk and an RS Meter to adjust the placement of my mains so the response from 70-20k was as smooth as I can get it. This involved an entire Saturday of making 1-2" adjustments and trying different angles of speaker toe-in. Be sure to try slightly asymmetric placement of speakers by having one a few inches closer to a side wall then another. You will see dramatic differences in bass response. The same thing goes for how far they are from the back wall.

Then, adjust with the EQ that your receiver has. My receiver only has bass and treble controls at 70 and 10k, so I am quite limited there. In my case, +4dB at 70dB and +2dB at 10k produced a solid response for the mains.

Step 3 - Subwoofer.
Turn off the mains and run only the subwoofer. You will spend another day running bass sweeps with the RDES disk in bypass mode. Try different positions until you find a placement you are satisfied with. In my situation, 12" from the back all and 12" from the left wall (corner placement) worked best, with the driver facing my seating position.


Step 4. RDES
Now, you start the EQ process. I used the four pre-sets to create identical adjustment graphs using the RDES setup method. Here, I focused on taming peaks. If you have a null, like my 70dB and 63DB nulls, EQ will not help. If your subwoofer only goes down to 30 Hz, no 20Hz boost in the world can help you. Focus on taming the peaks. A small boost in a non-null range is also fine.
Once I had the basic adjustments dialed in, I made minor adjustments to curves 2, 3, and 4 so I could run comparison sweeps. This way, I hade the original adjustment on curve 1 and could choose which adjustment worked best. I first focused on crossover adn slope. You will see major differences even by changin from a 12dB to a 24dB slope. Play around and keep running those sweeps.
Next, I focused on tweaking the dips and nulls based on the results of crossover tweaking. Overall, you want a roll-off at the high and low crossover points that approximates a 12 dB or 24dB slope (depending on your setup - ported=24dB sealed=12dB)

Step 5. Level match
Turn the mains back on. Run a compined sweep and see how they blend together. Here, play with the loudness settings on your receiver (and dvd player if using 6-channel outputs) to get your levels to blend and maintain a +/- 3db response (if you can - right now, I am pretty happy with my +/- 5dB.

Voila!

[audioferret]

One more note - one of the great benefits of using a sub that many people forget is that you will have a different acoustic response pattern for the mains than you will for the sub. My mains null at 70dB and the sub nulls at 63dB.

By playing with the crossover and other adjustments, I was able to minimize the summed nulls to 85dB at 55hZ. As you can see from the sub and mains graphs, it is probably possible to get rid of that null, I just need to find the combination that achieves that.  This is where delicate phase matching will come into play.  My next sub will have a continuously variable phase and this is key to reducing mains - sub interference from phase differences.

If the sub was located identically with the mains, I don't think this would be possible without some very serious amplification and eq capabilities.

[audioferret]

Well, I know this is a lot to digest, but I hope this answers some questions from people about the HT2's performance.  Many are concerned that the HT2 is not enough for their mains, but I sure think it is.  What counts is how well integrated the Mains and Subwoofer are.  The pairing of the two is really advantageous in a home theater environment.  The RDES tool really helped me understand how my mains and sub were affecting each other and I was able to develop a much better frequency response with it.  The effect on movies like The Matrix, Blackhawk Down, and The lord of the Rings was stunning. 

If you haven't seen my review of the HT2, it is here:

http://www.audiocircle.com/index.php?topic=35084.0

After learning how to properly use this equipment, I am truly an advocate of "not more bass - BETTER BASS".

Again, I hope this helps.