subwoofers and panels don't mix

Although it's not really a subwoofer/ribbon combi, I feel that Apogee has managed to combine a cone/ribbon succesfully around the '90's. I'm not saying my Apoge Centaur Major is perfect - it just isn't. But the transition between woofer and ribbon is flawless, even considering they're crossed at a remarkably high 350 Hz. Apogee has done several things to achieve this. The woofer is placed in a closed enclosure, which helps transients. The centre of the woofer is on the same height as the centre of the ribbon, so the woofer is not, like for instance Martin Logan, placed under the ribbon, but beside the ribbon. That also means the woofer is placed about one metre above the floor.
So all I'm trying to point out is that it is possible to succesfully combine a cone woofer and a ribbon/planar. It's just a lot of hard work.

I became really frustrated with trying to integrate subs with Maggie 3.5R's. About 6 months of trying with Carver true subs (they were poor, slow and had horrible overhang).
I spun them off for a brutal loss and moved on.
They literally had a delay before playing and 1-2 seconds of overhang afterwards. I guess when they glued a 4 pound hunk of steel to a passive radiator to calm it down that's what you should expect.

So I went on to smaller Velodynes (can't remember the model). Mass loading and spikes helped, but still seemed far too dissimilar to be acceptable. In either case with the Carvers or Velodynes, I tried every possible combination of electronics, internal XO and external Bryston XO, low pass/high cut frequencies, running the panels high passed and full range, different cabling, etc. None were acceptable to me.

I've heard REL subs in a few situations with Maggies and they were better, but still not great. I can say that I prefer 2 subs far more than one, regardless of location and implementation. Also, generally, that smaller the sub driver, the better luck you'll have.

I really can't believe that Harry Pearson in Absound recommended 3.6's and Carvers- shockingly bad IMHO. That would have been the point I stopped listening to reviewers as any reference other than anecdotal.

RFG

Just a thought - having never experimented - but could the issue be related to dynamics? A panel is not known for punchy dynamics (typically they compress audio signals and are preferred for classical listening)

...yet most subs are evaluated on their dynamic impact.

My suggestion would be to use an adjustable audio compressor on the sub signal so the sub can work in a "balanced" way with the rest of the audio frequencies from the panel....limit the dynamic range of the sub to match the panel.

A balanced sound will be correct at a variety of listening levels/dynamic ranges rather than over a very limited range or sweetspot.

This works if we assume that the panels bass roll-off remains consistent at different volume levels (like cone speakers generally do)....if the panel roll-off is also level dependent then I can't see a way to ever achieve a proper match.

i owned the centaur minor. as soon as i heard the first note, it sounded like two different speakers.

the problem is a lack of coherence. a ribbon midrange and cone bass create a discontinuity. i have always been able to distinguish the difference between cones and panels.

i believe i can identify a cone driver when it is combined with dissimilar driver.

it may be possible to disguise the presence of a cone if the main speaker is not crossed over to the sub. if the sub rolls off with a steep slope at say 45 hz, you may be able to blend the two driver types creating a a seamless blend for most listeners. however, an experienced listener will probably detect the presence of a cone.

personally, i will wait for magnepan to design a panel driver capable of producing frequencies below 40 hz.

Shadorne has a great point. Another thing I found during the Maggie subwoofer debacle is that Maggies seem to be very linear in output power (or sound pressure) relative to input power from the amplifier.

Subs (and most dynamic speakers in my experience), tend to
be more logrithmic, which happens to be more like the way we hear. Not that the comparison between panels and dynamic speakers is bad, just that they are different.

That difference seems to lead to an imbalance between
panel level and sub level with different source material
and differences in recording levels and different levels in individual songs. I found myself getting driven crazy adjusting the sub volume versus panel level even within
1 song or when I changed albums. That level problem even more than the dissimilar speaker mating problem led me to give up on the process and just listen to the panels full range.

Best of luck, I hope you have better results in your quest.
An electronic crossover is helpful, but has other issues that seem to go along with it (phas and staging issues mostly).

RFG