Eric and George,
Do you perform correction on the midrange and treble also when you use the Tact?
I understand the best benefits are made in correcting the lower midrange down through the bass. I also understand that if you try to flatten out upper frequencies you end up with a not very nice sound. Are you better off leaving that part of the spectrum alone?
I don't suppose you can only correct parts of the response (lower mids and below) if you don't want to mess up other parts (upper mids through treble)?
Thanks,
Bill
Bill,
You can use correction over whatever portion of the frequency range you want. The "target curves" can be edited, and by making them follow the measured curve over a particular frequency range you basically eliminate correction over that band. Essentially all of the "stock" curves provided by TacT give a small boost of 1-2dB on the bottom end (below 100hz or so) and a slightly larger progressive cut on the high end (above 10khz or so). This seems to follow measurements of most good speakers. While a "flat" response can be achieved by a TacT this will not sound good, as it basically will give a bit of cut to the bass and boost the high treble thus producing too bright a sound.
I believe that correction from 300hz and up is at least as important as 300hz and below. The way I see it, there are three major benefits of correction...
1. Bass. You can easily compensate for the room modes. At first listen this seems to reduce bass impact, because the powerful +10dB or higher spikes to which you are accustomed are no longer. Bass nulls are present in real rooms also and are more tricky to correct but with careful placement of speakers and listening position, and proper manipulation of the target curve, they can also be overcome. At first, overall bass level seems reduced because of the absence of the room nodes. Upon further listening, however, all the bass notes are just "there". Without correction many are obscured by the big peaks or lost in nulls. For me solo piano demonstrates this the best -- on good recordings the instrument sounds like it is in the room. Having played piano for most of my life this was a most welcome change!
Meridian's correction works only on the bass. I believe DEQX in its basic mode focuses primarily on the bass also. The TacT automatically attacks both the bass (of the main speaker and also subwoofers with the 2.2X) and the midrange and treble...
2. Frequency response. Although speakers are typically rated +/- 3dB from their specified bass cutoff to 20khz or so, few specify how these measurements are actually obtained. Unless that information is provided the specification is rather meaningless. Typically in a real room you will see swings much larger than 3dB throughout the frequency range up to 20khz. Causes include driver distortion, cancellation effects around the crossover frequencies, cabinet resonances, and poor speaker design.
The TacT RCS can correct these errors but only at the listening position. DEQX and more recent products from TacT (Millenium mk3 and TDA2200) have more sophisticated ways of correcting these errors which work throughout the room. There is also add on software for the TacT amps that can do this now. TacT has promised an upgrade for the 2150 amps which will provide much of the Millenium mk3 & TDA2200 functionality, but don't expect to see it anytime soon.
3. Imaging. If your speakers are capable of throwing a convincing soundstage (like the Dali Megaline I heard last week) AND your room is perfectly symmetric AND speakers are positioned exact distances from front and side walls AND there is a single listening position located exactly in the middle between the two speakers -- you are lucky and probably have great imaging without any correction. More than likely, your setup will fail to meet one or more of these criteria in which case the listening position will be located at a different angle off axis from each speaker or the speakers will be different distances from the side and front walls or listening position. The result is variation in amplitude and phase of the sound from each speaker reaching the listening positiong that is frequency dependent. This can be heard as a shifting of the soundstage depending on frequency and location of your head. The TacT will create perfect channel balance at a given listening position by adding delay to the closer channel (so sound arrives at the same time for both) and normalizing amplitude/volume at ALL frequencies between both speakers. The net result is a stunning with a rock solid center image and placement of instruments across a wide soundstage that extends well beyond the actual loudspeakers. Even big speakers like the RM/X totally disappear in the room. I had thought my speakers imaged quite well until I heard this in action and it is quite striking. For me this was the "point of no return".
