A12P F.A.S.T

[jimbro]

Thank you!

 

[Quard]

+1 on thanks to everyone who contributed to a great thread,
in my case most specifically to Bob Brines for post #18

Follow-up question to Mr. Brines (or anyone else who's been there, done that):
can a smooth, musically coherent handoff be achieved
by pairing a metal-coned, sealed subwoofer
with an OB mid/upper (say, for example, an A12p), as opposed to a BR mid/upper?
or will the differences in tone color/timbre just be too apparent to ignore?

maybe I'm just dreaming like the fairly cheap noob I am
for an unrealistically simple solution--

Linkwitz' choice of drivers/enclosures,
putting metal-coned OB woofer between OB mid and sealed sub,
(cf. Orion, and I think, the LX521) seems to imply that it didn't work for him.

Ed Schilling is quite happy with his paper-coned bucket sub + BLH,
but even that design puts the horn's bass output
between the mid/upper (enclosed in this case) and the sub.

Many thanks in advance for any and all thoughts!

 

[Bob Brines]

I personally don't understand the OB craze. I realize that a lot of guys like the sound of an OB. Euphonic, comes from everywhere sound. To be done right, and OB requires a huge amount of real estate that I don't have and I presume that my customers do not have. A decent OB requires the same degree of engineering that a decent BLH requires. You can't simply slap a driver on a board, sit back and enjoy audio nirvana (small letters, not caps). Anyway, been there, done that.

Now to your question: I don't have any difficulty integrating a metal woofer with a paper
mid-tweet. I think (IMO) that the difference between paper and metal do not manifest themselves until higher up in frequency. As far as enclosure type, as long as you have sufficient overlap, at least an octave, enclosure type is pretty much irrelevant. I am running a BR on top because I had a pair laying around. A sealed box would work just as well. I need to look at the cosmetics, as these will be going to Dallas in May.

Last year I had metal tops (A7.3) on a small OB over paper H-baffle bottoms (GW-1858). They had their problems, but no one mentioned integration problems.

Bob

 

[Quard]

THANKS! (caps intended)

Great help in getting my noob imagineering dept. under control.

 

[RonVinyl]

The whole reason for going FAST is to relieve the A12P's of bass duties. That requires an XO. 4w will be plenty of power for the A12P XO'd above 200Hz or so. If you run the A12P's wide open, 4w is iffy, particularly if you listen to any rock, classic or otherwise. You will then want to XO the woofer at something like 40Hz (MLTL) or 60Hz BR. A Q=.7 sealed box would cross at ~100Hz. I suppose at those low frequencies timing errors would be moot.

One thing that often gets lost is just because a speaker is not producing any sound at low frequencies, doesn't mean that the driver is not trying its best to use that low frequency power. You need the XO to remove unwanted frequencies from the driver.

Bob

Bob,

One last question...

If I plan on adding helper woofers to my Super Pensil A12p's, would you say XO the A12s at 150 Hz, then send up to 150 Hz to the sub (using the amp's XO)? I like the Dayton APA150 that you are using, I would send the signal to the AMP via the pre-outs from my Decware Mini Torii.

As long as that is good, would it be an OK decision to go the sealed woofer route?

Thanks!

Ron

 

[RonVinyl]

Thinking about going sealed with both routes, 8 liter sealed for the MA, and sealed woofers. Might give this a stab.

R

 

[RonVinyl]

Thinking about going sealed with both routes, 8 liter sealed for the MA, and sealed woofers. Might give this a stab.

R

Amp: Dayton Audio APA150 150W Power Amplifier | 300-812

Woofer Option 1: Dayton Audio RSS315HF-4 12" Reference HF Subwoofer 4 Ohm High Fidelity Reference Series 295-464
Woofer Option 2: Eminence LAB 12 Professional 12" Subwoofer Speaker | 290-570
Woofer Option 3: Peerless 835017 12" Aluminum Cone XXLS Subwoofer | 264-1114

 

[Bob Brines]

A couple of thing for you to ponder:

1. You cannot cross the A12P passively in a sealed box @ 150Hz. That is too close to the impedance resonant peak. You will have to do it active, then the peak is irrelevant.

2. The Lab12 is an old school subwoofer that shouldn't be run over 100Hz. I have not modeled the 835017. The FR trace looks very good, but I suspect that it needs to be run in a BR. That might be too big for your application.

3. The APA-150 is a very nice amp, but limited in power -- 75w x 2@4Ω, 150w x 1@8Ω. I find that to be enough, but you might not.

3. If you want to get it right, you will need to measure your results. The cheap out is a UMM-6 mic and REW.

4. The miniDSP or any other digital XO+EQ box is your friend. As stated above, you probably won't be able to make the XO work active on the A12P, so you might as well cross both active.

5. Hint: When doing the XO/EQ, crank both amps up to max and do the volume control in your preamp or music player. Otherwise, you will have to measure the balance at every volume setting. Log pots usually aren't. But, the, remember that is is amps on last, off first.

Bob