The less "processing" of the signal, the more accurate. My preamp has an option to bypass the tone controls altogether and after listening carefully both ways it was a no brainer to tune the room instead of using an electronic device to correct problemns caused by the speakers interface with the real world listening room in order to make the sound full and coherent. And this was no cheap Preamp either. It's a $3000 plus Audio Research tube hybrid preamp dedicated to the line stage alone.
If Audio Research designed this preamp/line stage at that price point using the best quality tone controls they could put together and ultimately decided to have an option to bypass the controls altogether in order for their customers to recreate truly accurate sound, what does that say about the effect of a cheaply built device that will supply each channel with tone controls for each octave or half octave? By carefully a-bing the sound with and without tone controls in the signal path I concluded (as did virtually every other person who similarly a-b'ed the effeect with material they knew well) that tone contro;ls even of this quality subtracted more than they gave.
What can you realsitically expect from a cheap box which not only "alters" or "adjusts" the signal it bloody well bludgeons it into oblivion? How much does a "pro" equalizer cost these days? I haven't been in the market since the late 70s and early 80s when I thought the more watts the better and the most important thing about an amp was its THD and ID distortion ratings---how low it could go.., but whatever they sell for I'll bet it's less than a grand and probably closer to $500. And whatever the price it will still be bassed on 1970s, (or 80s technology if it's parametric) technology andengineering created by that same 70s thinking or mentality. (E.g., pots are all about the same, a turntable is a passive device with no sonic signature, wire is wire-- lamp cord is as good as anything else,bits is bits. caps is caps, resistors is resistors, ad naseum.)(
The coloration and degradation you'll get from running your signal through all those cheap pots with cheap gain controls will cause the ultimate sound to plunge into "mid-fi land" sounding close to Sharp, Bose or Kenwood quality. It will sound very similar to every other mediocre system you've heard. By using an equalizer you are in effect, sending it to "the rack" where it will be squeezed, stretched, shrunk, blown up like a bloated bubble and otherwise have it's original integrity chopped into tiny pieces by the "band" of electronic hit men who are lying in wait for it to enter they're dark domain...Your poor signal is sentenced to literally run through a guantlet as it passes through the equalizers inputs and is subjected to rapid fire aggravated multiple assault and batterys until it reaches the processors outputs. As it passes through the processor, it is being constantly buffeted on all sides by the cheap electronics; its original integrated essence is literally pounced upon, pummeled and pounded from all sides with machine gunned surprise sucker puches by a gang of ten, twelve, eightenn or even thirty six "thugs". Mugged to death before it becomes trhe sound of youre system, but well "equalized", of course.
Better to buy the likes of room tunes and echo busters to get the bass to sound right and integrate with the rest of the signal as it was decoded from the source itself.
Or do it the cheapskate's way. Get a bunch of pillows, houseplants, even fake houseplants and place them around the room to break up reflected sound as well as standing waves. Plants do a superb job of this.
You can make your own "echo busters" for a fraction of the cost of the ones sold on the audiophile market by buying some Sakrete 8" and 12" carboard form tubes and some wood end pieces from your local building supply (Home Depot has them on the west coast) put a bunch of sand in plastic bags at both ends and fill the middle with a combination of pink wall insulation (insulation side out towards the listener, aluminum side in towards the center of the form tube), miscelleneous sponges, and rubber or synthetic plastic rubber place mats from the Dollar Store with golf club tubes from your golf bag down the middle (three works best) which will be also filled with sand. You can fill in the gaps to make it solid and firm by throwing in "peanuts" from packeges and more sand Take rubber bath mats and glue them with the side with the little circular pods which hold it on the floor glued to the inner side of 8 or 12 inch form tube covering it completely. Glue the bath mats on with highly elastic caulk that is synthetic plastic which is rubbery, highly elastic and a good bonder. Use the same type of caulk to bond all the materials in the project together. Cover the outside of the form tube with the same old used rubber bath mats (the Dollar Store again if you don't have a old ones) with the smooth side in and the non-slip side out which makes it very absorptive, much like the eggshells material used on the walls of anechoic chambers and sold in sheets on the high end market. Cover the outside of the tube and bath mat with a thin cheap plastic table cover like the throw awy ones used by families on picnics, then cover the plastic with some cheap drap, curtain or similar type material you can find in the odd lot section of your local fabric store. After you've sealed it with the wood ends (if you can find a hunk of cork for the bottom so much the better) you'll have an echo buster that will out perform the multi-hundred dollar version. And it will look surprising good as well.
Place them in the corners of the room, at the midpioints of each wall, behind your listenihng chair, and infront of the equipment rack. Get creative and experiment. You won't be sorry!
