LOL, I just looked at your setup. No wonder you don't think it will sound good with a standard sub setup. You have a frigging movie theater/recording studio in your basement! I'm thinking your standards are quite a bit higher than mine. Thanks for the input. I cannot really do dual subs. I will be placing the one sub just left of the fronts though, almost underneath one of them. It is forward firing. I think setup like that, even if there is some slight localization of sound, it will not be noticeable. Can you explain to me about 2nd, 3rd and 4th order crosovers? I have no clue what you are talking about.
Actually, I graduated out of the basement with this system and have windows with great views!
I will try and welcome you with explanations as simple as I can make them.
People new to this hobby, often think that crossovers are like a brick wall. They are not, and at a crossover point there is a slope. A filter that lets through bass and not the higher frequencies is called a low pass filter. A filter that lets through higher frequencies and cuts out lower ones is called a high pass filter. A filter that cuts both high and lows at spaced points is called a band pass filter.
Now the rate of slope at the cut points, or turnover frequencies, have slopes that have orders. Loudspeakers and their drivers also have slopes. These are the acoustic slopes. The slopes introduced by the electronic components in the crossover are the electrical slopes. The acoustic slopes of the drivers and the crossover slopes sum to a composite slope.
Now these slopes have orders. A first order slope is one that rolls off by 6db per octave. So a first order slope at 100 Hz will be 6 db down at 50 Hz.
A second order slope rolls off at 12 db per octave and so would be 12 db down at 50 Hz.
A third order filter rolls off at 18 db per octave and would be 18 db down at 50 Hz.
A fourth order slope rolls off at 24 db per octave and would be 24 db down at 50 Hz.
Now the high and low pass sides of a crossover have to sum to produce a flat response over the overlap region. For second and fourth order slopes a flat amplitude response is produced if the slopes intersect at the point where both filters are 6 db down.
Take a look at the first graph in this
crossover design, and you will get the idea. The slopes of the drivers and electrical slopes sum to make composite fourth order filters 6 db down were the slopes intersect.
Now with most sub set ups, the crossover is taking place where the ear is not unduly sensitive.
However in your case your main speakers are starting to roll off at 120 Hz. This is an area where the ear is very sensitive. This region between 90 and 150 Hz is were the brain perceives most of the bass. A system with a hole between 90 and 120 Hz will always sound bass deficient, and will not be entirely masked by driving a sub "hot".
Since your speakers are sealed, the acoustic slope will be 12 db per octave. I have worked out that the 6 db point of the your speakers to be 90 Hz.
So if you set your speakers to full range the 6 db point will be 90 Hz with a second order slope.
Now most crossovers in receivers and processors have second order slopes.
So if you set the receiver crossover to 90 Hz with your Milleniums playing full range you should get a very good amplitude response.
Now if you set your speakers to small, the acoustic and electrical slopes will sum to fourth order. The 6 db point will now be around 105 Hz. To make a flat amplitude response you would need to roll your sub off fourth order at 105 Hz to get a flat amplitude response across the crossover region.
Now without using an external electronic crossover between your LFE channel and sub you will not be able to avoid a peak at crossover, although it may sound reasonable if you set your speakers to small and your crossover to 100 Hz.
Although your speakers have 4.5" drivers, the power is distributed between four voice coils, so I think they could be set to large. I assume you are playing the speakers full range now. Do you notice any distress in them, and how bass shy do they seem? Answering those two questions would help me advise you further.
So I would first try setting you speakers to large (full range), and setting your receiver crossover to 90 Hz.
You could try setting your speakers to small and setting the receiver crossover to 100 Hz and see which sounds best.
When you get your sub, please post back here.
