[mjosef]

Today I reversed the passive radiator slot (to fire at rear), on my RM1s, and the bass became thunderous, the upper frequencies became more prominant, so much so that I had to cut the mid pot to 11:30 and the hi pot to 1:00. I have the speakers close to the wall, about 12".
I also noticed that the twin woofer cones were moving than before.
What is/are the explanation for these obvious changes??? And if I decide to keep it this way, should I be adding or subtracting putty to firm up the bass some?
My room is about 11x14x9.5. No real acoustic treatments, bare wood floor.
CA Azur540c>Bottlehead foreplay>ResponseAudio3205(EL34s)>RM1s
RM1s has the blackhole mods, soundcoat+woven carbon fiber woofers.

[John Casler]

Today I reversed the passive radiator slot (to fire at rear), on my RM1s, and the bass became thunderous, the upper frequencies became more prominant, so much so that I had to cut the mid pot to 11:30 and the hi pot to 1:00. I have the speakers close to the wall, about 12".
I also noticed that the twin woofer cones were moving than before.
What is/are the explanation for these obvious changes??? And if I decide to keep it this way, should I be adding or subtracting putty to firm up the bass some?
My room is about 11x14x9.5. No real acoustic treatments, bare wood floor.
CA Azur540c>Bottlehead foreplay>ResponseAudio3205(EL34s)>RM1s
RM1s has the blackhole mods, soundcoat+woven carbon fiber woofers.

All Passive Radiators Move "out of phase" to the drivers they passively "react" to.  That is, as the actives move out, the PR(s) move in.

Low bass actually creates air movement "spherically".  That is, even though the woofer or slot is facing a certain direction, all the air around the speaker is set in motion to that frequency(s).

That said, changing the "plane" from which that wave is launched, and creates that movement, can cause changes in the sound.  In the forward facing slot, the phase relationship of the lower PR wave (to the active woofs) will be different, than in the rearward facing launch.

The interaction of the wave with the room will also differ, in that launching to the front wall, behind the speaker, will also affect the overall bass perception.

Many find their bass seems "deeper" or more "spatial" with the rear launch, but each room and placement will be different, based on room boundaries, and dimensions.

I have no idea why the active woofers might become more active, since actually the PR's load/impedance from the slot opening is exactly the same.

As far as the putty, I would start by adding a "pea" size.  I think most people have a tendency to always "subtract" putty, and run too lean.

[mjosef]

Thanks for the response John. Any idea why the mid-upper frequencies became more "in your face" or stronger? Could it be from some upper bass cancellation as a result of the reversal?
I can see how the bass increased from firing to the rear and be reinforced by the wall and cavity of the windows which is right behind each speaker.
In fact, I usually hear a bigger bass response from my bathroom which is adjacent halfway down the left side wall. Now that bigger bass can be heard right in the room itself.

[James Romeyn]

Discerning more excursion of the 8s w/ a naked eye would seem to require a huge difference. 

Inverting the PR slot to the rear should invert the PR phase & also improve its coupling to the room boundary intersections.  The intersection points (corners) contribute the greatest quantity of boundary effects.  This could increase PR excursion, which in turn could increase the excursion of the active 8s.  This may exactly mimic the effect of changing the PR mass, & could cause two other simultaneous effects: Lower bass cutoff & leaner midbass output.  Less midbass can easily be interpreted as a more prominent midrange &/or upper midrange, consistent w/ your observation. 

Along these lines, 2 identical systems can be compared, the only difference being one system digs a half octave deeper in the bass.  Half the test subjects might say the one w/ deeper bass has "more bass", the other half test subjects might describe that system as having "less treble".  Two different ways of interpreting & personalizing the spectral difference.   

[mjosef]

Well, I would be in the group that feels there are more bass. 
I was just a moment ago comparing the sound from the bathroom vs the sound in my listening chair, and there is definitely more bass now from the chair than in the bathroom. I am very surprised by the change, just reversing the slot, and keeping everything else the same. I would say the bass output has almost doubled and reaches much deeper.  I added a little putty as per John's, and the bass is a little more solid...sounds like I am running a sub woofer.
I will add more putty and see how what gives.
Thanks for all the great info.

[John Casler]

Thanks for the response John. Any idea why the mid-upper frequencies became more "in your face" or stronger? Could it be from some upper bass cancellation as a result of the reversal?
I can see how the bass increased from firing to the rear and be reinforced by the wall and cavity of the windows which is right behind each speaker.
In fact, I usually hear a bigger bass response from my bathroom which is adjacent halfway down the left side wall. Now that bigger bass can be heard right in the room itself.

Well as Brian always says, and Jim has alluded to, adjusting bass sets the foundation, and it will affect the "whole" of the frequency spectrum.

Now if you had RM30's I might suggest that the 6.5" woofs running up to and slightly over 280Hz, might have something to do with it, but your RM1's likely have a 155Hz or 166Hz hinge.

Sounds like you are enjoying the change, and now you get to start the series of clicks and pinches to dial it all in.

As far as the putty, add just enough to get the bass a little soft and then "subtract" sesame seeds, until you like it.

Are you nearfield?  or farfield?

To reduce the mids a pinch without dialing them down on the L-pads, try listening with a "tighter" convergence.  That is aim them to converge 2 feet in front of you instead of 1-1.5 feet.

Or for "grins and giggles" widen the convergence so they shoot "outside" your ears by a foot.

That may allow you to run the L-pads higher without the mids being too hot.

[mjosef]

Speakers are approx 5' apart(narrow free space), sitting about 9' from each speaker, with convergence is about 2' in front of me.
I just pulled the speakers about 2" further into the room, so now I have about 16 inches behind there, seems to tame the bass some, added a 2mm ball of putty, dialed up the mid a couple clicks...sounds cleaner to me.
Its after midnite here now, so have to listen softly(68-72dB).
Have to say, I like the depth of the bass now, its kind of scary to hear how deep it stretches compared to the slot being fired forward into the room. The former sound was much leaner, and had its charm, but this is like a whole new speaker. 
Tomorrow I will experiment with your convergence suggestions.

[James Romeyn]

Most if not all RM1's were alnico magnet BG ribbon mids with a 450 Hz xo pole.  I'd bet lunch money all RM1s were gone by the time the neo mids appeared.  Even RM1's w/ the neo mids, if any exist, I think are x'd pretty high, 280 Hz or so, maybe higher.

If the 8s are x'd at 450 Hz (about A above middle C), they sign off way higher, because the xo slope is first order (only down about 9 dB at 900 Hz!).

[mjosef]

I though the panel was of the current model...but I could be wrong. It says: "level 9 Sound Design"
Here is a pic of the RM1s, dont have a close up of mid panels at this time.