Stereo Sub Power Requirements Question

I'm going to build a set of MTM bookshelf speakers that will start to tail off at about 70 Hz.

I want to build a pair of subwoofers to run in stereo as the third part of this design to fill in the bottom end.

I am thinking of using the Vifa MA26WR09-04 10" Aluminum Cone Subwoofer shown here.

The relevent specs are that it is 83.3 db at 2.83V/1m and power handling of 300W (I'm presuming that's max and not RMS). It supposedly has an F3 of 33 Hz in 1.5 ft3 sealed.

My question is this:

If I build two of them and run them in stereo, how much amplification do I really need? Should I go with a full 250W plate amp or could I get by with 100W?

The difference in cost is a semi-non-paltry $60.

The top part of this is an MTM design that is ~90 db 1W/1m efficient.

Opinions and suggestions are most welcome.
 
I should have specified that this is for a dedicated two channel rig. The pre-amp is a Bottlehead Foreplay and the amps are monoblock gainclones.

The "how low and how loud?" is a function of the kind of music I listen to. This rig is used for 90% small ensemble acoustic jazz, 5% classical and 5% evenly distributed between classic rock and world music. I want it to blend in seamlessly so I only want the low bass to be as loud as it is supposed to be relative to the music.

The reason I want two is because I was thinking in terms of stereo all the way up and down the frequency range. Am I not thinking right?

I was also thinking of two subs for the coolness factor as well as that they could be used as stands for the MTMs.

I have a most excellent sub for the 5.1 rig; an Adire Audio Rava, which is basically a sealed Shiva. Very sweet.

I have not wanted to use that sub because I would have to adjust it every time I switch from the home theater rig to the music rig and back, and then there's the issue of running two separate inputs into it at the same time and the liklihood of that damaging the plate amp.

Open to suggestions at this point.

It occurred to me in a free moment this afternoon that the 100W plate amp probably wouldn't work because of the sensitivity of the Vifa sub compared to the MTMs. The sub is 83.3 and the MTMs are ~90. Hence I think I would need the 250W plate amp and that driver still might not be optimal.

Comments?
 

SpeakerBob

Member
2002-08-15 6:21 pm
UK
The driver you've chosen seems to have a small x-max for a sub. (11.6mm peak) . Also in the pdf for it they show the freq response from 300Hz upwards :confused: A sub is generally used from ~100Hz downwards.

Personally I'd be looking at different drivers. The peerless xls 10" seems a good choice, but there are plenty of others.

Cheers,

Rob.
 
cytokine said:
I should have specified that this is for a dedicated two channel rig. The pre-amp is a Bottlehead Foreplay and the amps are monoblock gainclones.

Nice

The reason I want two is because I was thinking in terms of stereo all the way up and down the frequency range. Am I not thinking right?[/B]


Not necessary as the lower you go, the less "stereo" there is.

I was also thinking of two subs for the coolness factor as well as that they could be used as stands for the MTMs.[/B]


As you wish. Cool hasn't entered into my designs before. (mind you some do turn out pretty cool)

I have not wanted to use that sub because I would have to adjust it every time I switch from the home theater rig to the music rig and back, and then there's the issue of running two separate inputs into it at the same time and the liklihood of that damaging the plate amp.[/B]


I agree, different woofers for different systems

It occurred to me in a free moment this afternoon that the 100W plate amp probably wouldn't work because of the sensitivity of the Vifa sub compared to the MTMs. The sub is 83.3 and the MTMs are ~90. Hence I think I would need the 250W plate amp and that driver still might not be optimal.

Unless you're room is small, 250 is the way to go, if not more.

Comments? [/B]


I have had much less trouble integrating a single sub into systems than I have two. That's not to say you can't do it and do it well, just to say that my experience says go buy one nice big woofer and one good plate amp.

My main system is two 15" coax and one 15" woofer.

Cal
 
Chris;

That seems like an interesting choice but perhaps not the most economical. That's a handsome driver though. I like the concept but it's not where I'm heading.

Simon;

I think the gainclones do 56 W but I know nothing. It's just something I think I might have read somewhere. Yeah, 100W with that driver won't get me there.

Rob;

Yeah, perhaps it's not the best choice. I'm taking the reference for this from Zaph, whose MTMs I am going to build. I respect his opinions but am open to those of others since I know nothing myself.

Cal;

OK, I'm convinced. A single big *** subwoofer.

Which one?

Or perhaps I should build something to replace the Rava for the home theater rig and move the Rava over for music duty.

More opinions? You guys are really helping me focus my thinking on this. I appreciate your time and efforts.
 

SpeakerBob

Member
2002-08-15 6:21 pm
UK
Hi cytokine,

I have no listening experience of your vifa driver - I was just a bit wary of the x-max. My maths puts each of the sub's excursions at x-max (at 30Hz in a sealed box) when your mains hit ~8W.. However, I have been known to make fundamental errors when doing quick calculations.:D

If my maths is correct then a 100W amp will be plenty, but make sure its a 100W into 4 ohm amp.

If Zaph says they'll work fine then I'm sure they will.:cool:

Rob.
 
Ha!

I spend a heck of a lot of time browsing the PartsExpress catalog and website looking at their different drivers including the Daytons.

I wonder how they sound?

Anybody want to comment about my idea of moving the Rava over for the music side and building something really big for the HT rig?

Here's what Zaph said about those Vifa subwoofer drivers:

Other future ideas might be to build the floorstanding version, but sealed with each bottom chamber housing a powered, side mounted sub. Or if you already have the PE boxes like me, a pair of subs could double as matching stands. The new Vifa MA26WR09-04 aluminum cone certainly has my attention for possible usage in a stereo pair of amplified 10" subs.

Maybe if they were side mounted as he suggests and pointing away from each other the interference might not be so bad.
 
BassAwdyO said:


Shouldnt make any difference in an omnipole(which is what a sub is)

If you like the rava musically, then go for it....

new HT sub gets my vote(much funner making something BIG with LOTS of excursion)


What driver?

Something really big and really tight for a sealed configuration.

I have some enthusiasm for something that would shake the house even more than the Rava.

Just to see the wife roll her eyes.

I live for that.
 
How did we go from a 10" each side to 5 - 12" woofers a side? :D

A single 15" and a 500w amp will probably meet your needs unless you just can't control yourself.

If it's just for music you can use a PA woofer. Something like this Selenium

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=264-436

That with a 1000w amp would do more than make her eyes roll. It's good for about 125 dB

Cal
 
RobWells said:
HT only sub - I'd be looking at ported 'EBS' type subs with 15" or 18" driver/s (Big driver/s, big ports, big box/es and big amp/s :D )

Of course it depends on the space you have available, and budget.


Cheers,

Rob

You mean like El-Pipe-O? I really want to keep it small (ish) and sealed. Budget is slightly less of an issue than space at the moment. WAF is a high priority.


justinc said:
somethign really big? how about two tower arrays with 5 atlas 12" each. Then power each tower with a behringer EP2500 and a linkwitz transform?

Umm.... No.:D


Cal Weldon said:
How did we go from a 10" each side to 5 - 12" woofers a side? :D

A single 15" and a 500w amp will probably meet your needs unless you just can't control yourself.

If it's just for music you can use a PA woofer. Something like this Selenium

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=264-436

That with a 1000w amp would do more than make her eyes roll. It's good for about 125 dB

Cal

Why that one? Have you heard it in this kind of configuration?

I don't need massive dbs just for the sake of massive dbs. I have a pair of Shivas in my car that get 300W each. If I need to break something loose (like fillings) I can just go for a drive.

No, gentlemen, my goal here is sound quality.

If I can build something really outstanding that will integrate better with my two channel rig than the Rava, I want to build it.

But what driver and why?

I guess I haven't given a budget for the sub side of things because I was still dwelling on the one vs. two issue.

That might make this discussion a little more productive.

Let's say $200 for the driver and we'll plan on a 250W plate amp from PartsExpress for about $130. The rest would be for wood and glue and paint. That's about $400. I can go higher if need be but let's start there.

What's the "best" $200 10" or 12" driver out there that plays low and tight in a sealed configuration?

I know, I know. That's not a fair question. Still, I'm looking for really good sound with db a distant second. It just has to integrate really well with the MTMs.

Anybody else like Simon5's suggestion of the Acoustic Elegance 12 or 15? I haven't heard them.