Quoted from Av_Phile1 at audio lies and myths thread. (I believe this INDIRECTLY answers your question. It depends on what you already have)
That's the easiest and safest way to go for a multichanel set-up. Have them all from the same model series meant for multichannel gears. You are virtually assured of NEARLY the same timbral qualities across all speakers. I'll discuss why NEARLY later.
Having said that, I must admit I have come across multichannel set-ups that have different brands for fronts, center and surrounds. That is possible because a good speaker is supposed to be timber-independent. Timber is the same as sonic coloration. A neutral speaker does not have coloration. So if your speakers are neutral, they can be from different brands and timber matching is never a problem. But they cost a lot.
The reality is that mass brands of speakers have their distinct coloration, hence timber. It can range from subtle to pronounced. For them to be within reasonable price tags, many compromises in their manufacture come to play so that they never really can provide the flat frequency response that characterize a neutral speaker.
So if our budget confines us to stay within commercially mass produced gears, to be safe and sure, get your multichannel speakers from the same model series. I say, model series. Because even the different speaker models within a brand do have different sonic coloration.
So let me go back on why I said NEARLY. You see, almost all multichannel speaker models out there use the D'Apollito speaker driver arrays on their center speakers - mid/woof-tweet-mid/woof horizontal arrangement. The problem is that this configuration provides an entirely different spectral dispersion trait that will surely affect its timbral qualities. And their smaller enclosure dimension will also alter their timbre from the larger L and R enclosures. In fact any difference in box dimension and driver array configuration with that of the front L and R driver config will impact on its timbral uniformity across the front. D'Apollito arrays are known to suffer severe lobing dispersion patterns that may not be present in your L and R speakers. The mid location of the tweets is the culprit. That is why if you noticed, the B&W 800 series have center channel speakers with tweet-woof arrays common with their L and R speakers. The tweeter location at the top shares the same driver configuration with their L and R speakers.
The ideal really is for the center speaker to be IDENTICAL in every way to the L and R speakers. But for production cost considerations in mass brands, the center speaker need not be perfectly matched because it is meant to reproduce mostly voice frequencies. And provided the timbre mismatch is not severe, mid frequencies for the voice can easily be timber matched by just using the same driver type and crossover points as with the L and R speakers. The D'Apollito array is really not necessary or ideal for this purpose. Its dispersion trait is just meant to allow listeners who are not centered on the screen to perceive a center dialog localization. But it will not perfectly timber match your fronts, unless their drivers are similarly arrayed along the horizontal axis.
Regarding the surrounds, spectral timbre may not be critical as some dispersion traits different from the fronts are sometimes desired. Like using dipoles and bipoles to achieve a more enveloping ambient sound. This is fine IF and only IF the ambient information does not spill over to the fronts. So if you have chirping birds or just echoes confined in the surround chanels ONLY, slight timbre disparities between front and back won't matter. But if you have a jetplane, car engine or galloping horses PANNING from the surrounds to the front or vice-versa, you have a problem. You certainly don't want a 747 jet plane to sound like a Cessna when the sound moves to the back. Or a Ferrari going to the back channels sounding like Toyota. The illusion of realism is diminished. So, again, the best is to have the identical speakers ALL AROUND. Especially when you are into multichannel music using DVD-A or SACD or even some DVD concerts where the back channels can have full range audio signals as much as the fronts.
But this is ideal. And more often than not, budget will dictate what we can get. And that's not to say you won't enjoy multichannel materials if your speakers are not perfectly timber-matched. Even the movement and distinct separation of signals between channels can be a joy to hear. With many multichannel speaker sets out there, the mismatch is often slight. Nothing to lose sleep over. Grin
