Two woofers or one?

[Godzilla]

I've been enjoying 15" Alphas on open baffle for the past few months. They are mounted close to the floor. But i was wondering if anyone can tell me how adding a second woofer per side enhances the overall sound? I have seen systems where one 15 is on bottom and another is on top. I am concerned adding a top woofer will create problems sonically because it will be closer to ear height. Can anyone describe what they have heard when doing this?

Thanks,
Godzilla

[planet10]

Jeff,

If you keep them near the floor, you take advantage of the floor as an extension of your baffle...

dave

[Scottmoose]

Seems a bit of a waste to go MTM with drivers that size for the reason Dave mentioned, plus a few others. Still, one way to find out if it works for you...

[rjbond3rd]

Hi Jeff,

Speaking strictly as a newb, a second woofer in general would get you a higher max SPL, and more sensitivity. In MTM (or I guess, it's WFW), not only do you lose the boundary reinforcement for the upper woofer, but you'd also probablly have to worry about getting a null from its floor bounce? On the other hand, there might be a slight benefit to the diversity of woofer placement for froom modes, but I (newbily) speculate that it's a wash, and you don't gain any lower bass (just the upper part of the top woofer's contribution).

Personally, if I were doing it, I'd just get an 18" woofer with a lower Fs. A second (or fourth!) Alpha doesn't really get you more extension, right? Just sensitivity, but why not go for (a) a driver with an even lower Fs and (b) larger displacement (perhaps even equivalent to two Alphas?) I recall that MJK said the Goldwood 18" GW-1858 got him 20-something Hz in his room. One Goldwood is pretty cheap too ($90 last time I checked).

[freddi]

for me, GW-1858 did about "this" in H-baffle - subjectively phat bass

[rjbond3rd]

Hi freddi, sorry for the OT but:

1. Obviously those two measurements weren't in the same room, right?

2. I'm thinking of getting TrueRTA. May I ask what mic and mic pre you're using, and whether it's necessary to have it calibrated? I want a setup just like yours

3. It's pretty cool that you paste in the cabs and label everything -- you are the most prolific builder, I think.

[pforeman]

I built 3 sets of open baffle (Audio Nirvana 10" and Audio Nirvana 12") with both one alpha 15" in H frame and one Goldwood 18" in H frame in the last year.
All times I used a plate amplifier (B & K ) for the bass unit. Integration between the units was easy in all cases.
When plugged into my Moscode 600 amp, they could play so loud I had to leave the room and didn't sound strained.
When hooked up to a SET unit, the speakers would play very loud, but the max spl was limited to the SET not the choice of bass driver.
Both the 15" and 18" had similar bass in that with the correct setting ( for my taste) on the plate amplifier, they both had a rising bass response ~8 dB at 80 Hz which fell quickly so that relative to mid and highs, it was again flat at about 50 Hz, and -3dB at 40 Hz.
On both of the alpha 15 and, Goldwood 18 the plate amplifier was set at about 2/3 full to get my favourite settings. In my opinion, if you are going to use a plate amplifier, you don't need a second alpha 15, and not much reason to go 18"...
I made all of these for other people, and my Acoustats are mounted kind of permanantly, and therefore in the way for best listening spot for the open baffles I made. The room is 14' X 25' X 8 with cement floor and set up in the middle of the room.
Paul


x

[InclinedPlane]

Originally Posted by pforeman

When plugged into my Moscode 600 amp, they could play so loud I had to leave the room and didn't sound strained.

I'm skeptical...
I haven't found a fullrange driver that sounds nice at high volume on all program material. There's too much cone breakup in the 1-4 khz area, more so with larger drivers.

And I use 2 15"s per side. One handles 60-200hz and the other is a sub on its own amp. I claim excellent results.

[aquapiranha]

I have 2 alphas per side, plus a visaton B200 on each baffle. I 'did' have an issue with a lack of bass (!) but that seems to be sorted now. In fact, I am having to turn down the gain on the Rane or the bass is a bit too strong to maintain a normal relationship with the neighbours...

I would recommend at least trying it, even if you dont like it you could offload a pair of alphas easily without making a great loss.

Steve

[rjbond3rd]

Hi aquapiranha, what turned out to be the culprit with your bass problem?