Band-pass sub eq-ing (RCF 705ASII)

[pointfive]

Looking for some input on eq-ing a bandpass sub design.

I'm seriously considering getting an RCF 705 ASII sub to go with my 312a's. Although our band doesn't have bass or drums, I'm hoping to improve sound when I'm asked to also provide access to the PA for playlists at the functions we do. Also it would be nice when using both octave pedal and stomp box (future) during some tunes. Another reason is to help out the tops when we're playing the bigger rooms.

Looking at the freq response, and reading some comments about this type of sub being a 'one-note wonder', I wondering if anyone has had success getting a smooth LF response by using the eq of a digital mixer (I have an XR18), so that we can get an (apparent) flat response down to the lower extents to allow bass lines to sound even. The response obviously works to give low end for bass drum beat, but I was hoping it could be used as a reasonably convincing low freq extension to a speaker system that sounds rather good. Could be that it's easy, but until I have one, I'll not know how easy. Could be that I'm imagining a problem that doesn't exist.

Note that I understand that you can't have both compact size and great bass response, and I'm not considering anything too heavy for me to reasonably carry, so bigger subs with an even reponse are not an option. (Also not considering other brands, only other possibility would be a the 12" version, but RCF say that only suits the 8" and 10" tops.)

Any wisdom from the hive?

Martin

[Sam Spoons]

I tried a 12" sub for a short while (EV ZXA1) and sold it, one dimensional and a bit weak (even though on paper it virtually matched my 15" sub). My old school EV sBA75 15" sub OTOH is fantastic, but we do have drums and bass in the band. Do you have comments about a lack of bass when playlists are playing? If not I would save yourself the extra effort of carting a large heavy box around.

But, I have used the sub for acoustic music gigs where a Melodion or upright bass has been present and it is effective so your octave pedal and stomp box will definitely benefit in bigger rooms.

[pointfive]

...

Sam, thanks your input. It's funny that the specs for the 12 and 15 RCF subs look almost identical, but I find it hard to believe that the 15 doesn't go lower in real life.

There's the two different use cases, and for the playlist one, no-ones ever commented on lack of bass. There was a recent one where the client really wanted it LOUD (I actually had to leave the room to escape) and I felt that a bit of bottom end would have been nice to have, and also save my tops from working so hard.

The other case of us playing a a band, where we've played festivals and folk clubs with installed PA, and the low end coming out was lush (keys mostly), has always attracted me to picking up a sub for our own PA. Just remembered that our keys player has an amazing standup bass midi module, which we talked about incorporating, I'd love to hear that with a sub.

Could be that it's gear acquisition syndrome kicking in. Carrying it round, you're right, I can imagine is a pain. Maybe I should just limit myself to hiring one as needed, depending on the gig.

m.

[Sam Spoons]

IME my single, old school 15" sub is much nicer sounding than the new 12" sub I tried but, unless you have significant energy going on below around 100 Hz, you won't be helping the tops much with either of them. My usual approach is to use the crossover in the subs to feed the tops (QSC K12s in my case) and do minimal eq. If the crossover is right then you shouldn't need anything on the sub alone. Modern active PA speakers require much less overall eq than the passives I used to use and sound much better too. Buy the right sub (go and listen to a few but the one that 'matches' your tops is probably favourite) and leave the rest alone is my advice.

Hiring is a good option for stuff you only need a few times a year though.

[Wonks]

With subs, I think it's probably even more important to go and listen to them, compared to tops, than take other people's opinions (who generally haven't really listened to many subs in detail). Some band-pass designs can be rather 'one note', but so can an awful lot of ported designs. It is the implementation, rather than the basic design, that is important. Both types of sub can sound bad, and a bigger speaker doesn't necessarily mean better.

The unfiltered web is a bad place to pick up information, and so much 'knowledge' is simply the result of one uninformed person passing on the opinions of another uninformed person so many times that it then somehow becomes 'true'. You then get shouted down because you've actually listened to or even own the kit in question and know what it's really like and dare to contradict the percieved wisdom of the herd.

40Hz to 80Hz is one octave. Take a phone with a sine wave generator app along to test the sub. If you can hear 5Hz step differences in that range, then it's certainly not a 'one note' sub. It may disappoint in other ways, or equally excel in its sound, but at least you know because you've heard it, and not because you've taken some 16 year-old's uninformed comment as gospel.

[Sam Spoons]

[pointfive]

Thanks guys.

Just got to wait until a reasonably priced local one comes up that I can test out.

m.