Just wait till you see what I did...... Mesa surprise

[drbassman]

The passive 12" radiating speaker faces down in the bottom of the cab.   The cab is also ported in the back.

[Dave W]

I'm familiar with the concept from seeing and hearing some stereo speakers with  passive radiators in the 1970s. Never tried a bass cab with one. No one design is perfect, I'm sure they have their pluses and minuses like every other design. It's all about whether the sound works for you.

[Psycho Bass Guy]

Well, thus far, I'm happy with the low end from this rig.

Your amp is made the way I wish mine was. I forget that not all the folks here automatically know what type of output tubes are in their amps.

As nice and as versatile as my Bass 400+ is tonally, it's not real big on punch, and that's even after I've tweaked the preamp and power section a bit. It's a great amp, but big iron and big output tubes= big sound and my Mesa is just kinda "medium" in both departments; yours is a whole 'nother ballgame. The Prodigy is basically the 400+ redesigned exactly the way I was suggesting the 400+ be improved, and most likely for the same reason. They're both 225-250 watt tube amps, but the 400+ uses twelve 6L6GC's to your Prodigy's four KT88's. Even with that ghastly amount of power tubes in the 400+, the supply and drive section never really push them to their full potential. (I'm just like an old gearhead boring out engine blocks.)

With most of my big amps in storage for the divorce, I only have my Mesa 400+ on a Trace 1153 1x15 for practice at home and my Trace Elliot VR350/Acme Low B Series I 4x10 which stays at church. The Trace on its Acme cabinet will rearrange your insides if I ask it to, but mostly I play pedal tones on my 95 Fender AmStd Jazz V and have it dialed to bring the mids more up front the more I dig in. If I get really into it, it gets into downright Geddy territory- while rearranging your insides. My Mesa is sweet, but it just ain't got that grunt. Yours, OTOH, should, though the crazed idiot in me wants the bigger model for myself, because, well, because I do. Maybe after me and the missus finish parting company...

[drbassman]

Your amp is made the way I wish mine was. I forget that not all the folks here automatically know what type of output tubes are in their amps.

As nice and as versatile as my Bass 400+ is tonally, it's not real big on punch, and that's even after I've tweaked the preamp and power section a bit. It's a great amp, but big iron and big output tubes= big sound and my Mesa is just kinda "medium" in both departments; yours is a whole 'nother ballgame. The Prodigy is basically the 400+ redesigned exactly the way I was suggesting the 400+ be improved, and most likely for the same reason. They're both 225-250 watt tube amps, but the 400+ uses twelve 6L6GC's to your Prodigy's four KT88's. Even with that ghastly amount of power tubes in the 400+, the supply and drive section never really push them to their full potential. (I'm just like an old gearhead boring out engine blocks.)

With most of my big amps in storage for the divorce, I only have my Mesa 400+ on a Trace 1153 1x15 for practice at home and my Trace Elliot VR350/Acme Low B Series I 4x10 which stays at church. The Trace on its Acme cabinet will rearrange your insides if I ask it to, but mostly I play pedal tones on my 95 Fender AmStd Jazz V and have it dialed to bring the mids more up front the more I dig in. If I get really into it, it's get into downright Geddy territory- while rearranging your insides. My Mesa is sweet, but it just ain't got that grunt. Yours, OTOH, should, though the crazed idiot in me wants the bigger model for myself, because, well, because I do. Maybe after me and the missus finish parting company...

Yeah, I think the 88's are really doing the job for me.  Our little club seats about 175-200 people and the Prodigy has tons of power left over for the venue.  There's something really deep and smooth about the Scout cabs with the 15 and 12" speakers.  I sold the one I had to get the Powerhouses and wished I didn't.  So, now I'm back to where I wanted to be with two of the nicest cabs I've ever used.  I'm happy!   

[Granny Gremlin]

The passive 12" radiating speaker faces down in the bottom of the cab.   The cab is also ported in the back.

That's weird and interesting to me.  It's just like some cabs have 2 ports (or 2 PRs for that matter - there's a bunch of home theatre subwoofers like that) instead of one.  As long as they adjusted the port size and PR cone weight accordingly, there's no reason for that not to be a valid approach.

I do wonder why they did that, like what would be the advantage.

I've been running my old Marshall 4x12 with just the 2 replacement 75w speakers running, leaving the old remaining Celestion pair in place but not powered... put out a lovely sound until the head died...

Yeah that's the idea.  It likely could have been optimized by adding some weight to the Celestions (and box size, or internal volume, was likely not ideal, but could be tweaked somewhat, dfepending), but I find them slightly more forgiving than ports (especially if the PRs have frames and spiders vs the cheap ones that are just a disc of weighted foamcore attached to a surround - they distort more, especially if not tuned properly, because there's no mechanism to ensure linear in-out travel).  .... I am kinda surprised that nobody's actually made a production cab like this yet actually.  I think it would be huge with punk and _core players.

[drbassman]

That's weird and interesting to me.  It's just like some cabs have 2 ports (or 2 PRs for that matter - there's a bunch of home theatre subwoofers like that) instead of one.  As long as they adjusted the port size and PR cone weight accordingly, there's no reason for that not to be a valid approach.

I do wonder why they did that, like what would be the advantage.

Not sure, outside my area of expertise.  They do talk about the design a little on their web site.  Not sure it's much detail though.

[godofthunder]

Very cool rig ! I have been running 15s and 12s for years.

[Psycho Bass Guy]

Mackie brought 'back' the idea of a passive radiator coupled to a tuned cabinet to augment lows with their first series of powered studio monitors (and Mesa also used them to great effect in the old Walkabout combos). The Mackies sounded REALLY good, which is why I don't like them for studio monitors. They're almost hi-fi stereophile in their exaggeration of critical areas where in the studio, you need accuracy, not beauty. I'd track with them, but not mix or master using

A passive radiator is basically a driver with no magnet or voice coil tuned to react at port frequencies and below. If you've ever been playing and something in the room would vibrate sympathetically, it's the same principle. Since there's no coil mass (because there is no voice coil at all in purpose-built radiators), the suspension can be tuned as tight or as loose as needed to get really huge lows out of smaller diameter speakers. The downside is that unless the port is carefully physically designed, those extended lows can be out of phase to the rest of the other bass frequencies and it becomes progressively worse below the port corner frequency. Since bass wavelengths are so long (around 27 FEET for low E depending on temperature and altitude 767mph/ 41.2 Hz) it can be hard to hear, but when it's a problem, it's a MAJOR problem, which is why passive radiators are not more common. They make perfect sense for an instrument amp being powered from a single source, but when you start adding multiple cabs from multiple amps, things can get weird in a hurry.

Part of the irony of speaker science is that we are still in the second generation of driver development for most bass speakers, and the exact same principles that modern drivers use were first employed in the first permanent magnet drivers of the 1930's. There have been forays into pushing the state of the art: servo-driven subwoofers, ribbon tweeters, and a few other esoteric designs, but by and large, what little gains in speaker efficiency have been made in the past 80 years have been in the refinement of materials and cabinet reflex designs. Even the BEST subwoofers are barely 20% efficient; everything else put into them is lost as heat. If we could make drivers with an efficiency of 60% or better, high powered bass amps could literally be used as sonic weapons. That's also why it's always going to be easier to get more volume with more drivers instead of more power.

[drummer5359]

That is just beautiful, congrats! 

[4stringer77]

If we could make drivers with an efficiency of 60% or better, high powered bass amps could literally be used as sonic weapons.

Someday bass players will rule the world like Kyle MacLachlan in Dune!

[4stringer77]

Is it possible to tune the passive radiator on the Walkabout? I think it is meant to stay in the factory setting. I'd like to try the head in my combo out with a different cab sometime to see what the difference is. Sometimes it feels hard to gauge my tone from what I'm hearing immediately in front of my amp compared to what's being heard in the rest of the room. Not sure if it's room acoustics or the effect of the walkabout's cabinet design. 

[Granny Gremlin]

Mackie brought 'back' the idea of a passive radiator coupled to a tuned cabinet to augment lows with their first series of powered studio monitors (and Mesa also used them to great effect in the old Walkabout combos). The Mackies sounded REALLY good, which is why I don't like them for studio monitors. They're almost hi-fi stereophile in their exaggeration of critical areas where in the studio, you need accuracy, not beauty. I'd track with them, but not mix or master using

Yeah, I had use of a pair of the MKI HR824s for a while.  They were nice, but as you say too nice.  Very generous in the bass/low mid area even despite proper use of the room mode switch.  I just couldn't trust them.  Good quality drive units in that box though (Vifa), and they can be found used for very cheap.  I could have probably gotten used to them eventually, but they weren't mine and now I have something I really like.

I was under the impression that (the MkI versions at least) were just straight up PR cabs.  Don't recall seeing a port on them (the PR was under the amp on the back).  Never used the MkII versions and those might haye been different (they looked different at least).

Even the BEST subwoofers are barely 20% efficient; everything else put into them is lost as heat.

Yes, but the idea was (at least in Hifi purposed speakers) that manufacturers are sacrificing efficiency for flatter response (in the intended usable range of the driver) and extension at the extremes - though this applies more to mids and woofers than subs.  PA and instrument speakers on the other hand, tend to be significantly more efficient, at the cost of a much more volatile and shorter response curve.... but yeah, that's still not very efficient.

Is it possible to tune the passive radiator on the Walkabout? I think it is meant to stay in the factory setting. I'd like to try the head in my combo out with a different cab sometime to see what the difference is. Sometimes it feels hard to gauge my tone from what I'm hearing immediately in front of my amp compared to what's being heard in the rest of the room. Not sure if it's room acoustics or the effect of the walkabout's cabinet design. 

It's the room and also what Psycho said about the wavelengths of low frequencies being so long.  ... also if bass is going through the PA as well as live off stage you are, to a degree at least, at the mercy of the sound guy as to whether he changes your tone much or not.

You can tune any PR, but depending on the design of the PR unit, it may be easier or harder to do so.  Adding weight is generally easier then removing weight.  Like I said before, often there's a bolt on the back of the thing you can throw washers onto, otherwise you can glue them on.  Sometimes, to save costs, the PR has no frame and is just a disc (usually foam core or foam/rubber covered cardboard) glued to a surround which is in turn glued to the cabinet - stay away from those and don't try to tune them because they're finicky.

That said I would trust that Mesa has tuned these well, and not play too much with it, especially since I don't think it's got anything to do with your issue.

[drbassman]

Well, Psycho is correct, the tone and sound of the Scouts over the Powerhouse cabs is noticeably deeper and richer.  The incredible thing I noticed at practice the other night is the cab is as loud from behind as it is in front!  Sound just "radiates" all around it.  The cabs do sound better out in the audience, too.  As I walked out to the end of my 20 foot cord, the bass response was more perceivable, due to the wave length Psycho mentioned, and design.  I didn't perceive that much of an improved sound with the PH cabs out in front at 20 feet.

In the end, it's a better set of speakers than the PHs for my purposes and ears.

[Highlander]

Someday bass players will rule the world like Kyle MacLachlan in Dune!

Ari... the Bass Player, has awakened...!

www.youtube.com/watch?v=gC6WJVQvkDE

Ari-Dib... Ari-Dib... Ari-Dib...

[drbassman]

Truth is stranger than fiction.