Hi Abhi, Iaudio,
This was adviced considering that Abhi has no opportunity to audition the bookshelf-sub combo. Many people have this problem. So under these circumstances its better to go for "safe" / "established" combinations preferred by users OR voice-matched combinations designed by the manufacturers, than to gamble on combinations derived from written specs.
Further comments on this issue:
1. It is quite well accepted that in a 5.1 speaker set, the center speaker MUST be from the same series as the front speaker. The reason being that both speakers have overlapping freq-spectrum, so sonic-pattern of CS must match the FS, identically the way it matches when we join our left hand palm with right palm. See the case for sub and FS match below...
2. In case of Sub and FS match, it is not case of freq-spectrum overlap being identical, but it is a case where a limited freq-spectrum of FS and Sub around the cross-over freq is overlapping
(there is also a factor of loudness slope... but we will skip that to focus on the KEY-factor of overlapping freq). Just because in this case the overlap happens in a limited band doesn't mean that voice matching matters less than the CS vs FS match. Well to a discerning audiophile it does matters, and to a explosive fx lover it doesn't. Why? see below...
3. There is no such thing as genuine sound of explosion, but there is such thing as genuine sound of Cello
(well there are many types of cellos also... but lets not get into that. You know the point I am making
). So we have some people choosing a different sub than the same series as FS, because it's better bang for buck, or it simply delivers better bang fx than the sub of same series. Wait, there are more reasons below...
4. Generally speaking, a sub belonging to budget-range of 5.1 series will not be as fast and musically linear as the FS of same range.
(This is why many audiophiles suggest going for a floorstander instead of BS + sub combo) Hence a person may buy Sub from different series /make that is as fast and musical as the FS. This is a case when even a discerning audiophile will choose a sub from different series.
(But these are rare cases... how many people have BS + REL /Velodyne premium-sub combos? not even 5% of audiophile crowd.)
Most likely a BS will be paired with VFM-sub. And in that scenario same series voice-matching is the "safe bet"... Even this combo is pretty rare, but is shouldn't be, once people agree to its merits. IMHO in a 10 feet x 15 feet room, the bass-management is very important and only BS-Sub combo can offer good flexibility. In such rooms if you put a Bass-rich bookself or floorstander, then one of the speaker gets pushed to the corner due to furniture layout restrictions, leading to unequal boomy sound. BS-Sub bass management will definately give "comparatively" flatter freq-response in such room.
Well, there can be exceptions to the all the generalisations above, my advice to Abhi is to play safe, since he can't audition the combos.
Regds,
Sonosphere
P.S: Abhi, Iaudio... wake-up the post is over

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