[Redbone]

First let me get up to speed on where I’m at.  The RM40s are breaking in nicely, better sound, richer, fuller, and better projection and imaging.  The room is approximately 25’ wide by 30’ long, the speakers are a little over 17’ apart in the 25’ dimension and toed in about 15 to 20 degrees to focus about 15’ out.  I have raised the front of the bases 1” with wooden shims to project upwards to 5’ at a 15’ distance.  This provides excellent sound staging and gives me a 5’ x 5’ sweet spot with a 10’ x 10’ area of general listenability.  The sound is blended very well am I am happy with this setup.  I will pour some concrete bases to replace the shims, later.

The QSC RMX 1850HD pro amp came in yesterday.  I went to Radio Shack and found a pair of ¼” TRS to RCA adapters so I plugged the Tjoeb 4000 CD player directly into the amp.  The Tjoeb has a volume control and the amp has gain controls so I am fine.  Hooked up the speakers, triple checking polarity, and played.  

Guess what ?  Less bass.  The midrange is super loud.  I liked the old amp better.  Okay, I’m not going freak out, I’m getting used to these paradoxes.  Time to think.  The overall sound quality is very good, with much better projection and imaging.  The bass is good, tight, and I can turn up the volume without distortion, but it doesn’t have the impact that I was expecting.  Now what ?

Sit down and think.  Aha !  There are two things that have changed.  First, I have no tone controls or loudness, second this amp is way powerful.  I remember an old tube color TV I had 20 years ago.  It served as a TV and a heater in the winter.  When you turned it on, your lights dimmed, the neighbor’s lights dimmed, and the whole block went dim.  It took about 20 minutes to stabilize at normal operating temperature but it was a good TV.  This amp is like that.  My old Harmon Kardon 6250 amp struggled to power these speakers, this one does it effortlessly.  Too effortlessly, it overdrives the ribbons.  I remember someone on this forum saying that they thought people ran the 40s too hot, and recommended turning the pots down below 12 o’ clock.  Now I see why, it depends on the amp.

So I turn the pots way down, still don’t like it.  What to do ?  I’ve still got the old HK amp, and it’s integrated, maybe I could use it as a preamp to get tone controls.  Nope, the only output is tape-out and that bypasses the tone controls.  Well, why not bi-amp ?  I’ve got a new 100’ spool of 10 gauge speaker wire, let’s go for it.  

What a nightmare !  I can see why people don’t like to bi-amp.  I’ve got four sets of speaker wires and two wildly different amps.  Oh what the hell.  I quadruple check all of the polarities, and run the Tjoeb into the integrated HK amp.  I run a tape out to the RMX amp.  Play.  Sounds really bad, yikes.  I’m going backwards guys.  Time to think.  Aha !  Stop and think, what did I screw up ?

Yup, I’ve got the channels reversed for the bass and treble.  Think about it, what a nightmare.  So I hook up one channel from the CD to the integrated HK amp and verify that the left speaker is playing.  I then feed the left channel tape-out to the RMX amp channel one and verify that it also drives the left speaker.  Bingo, great sound.  

Now I set the pots back to the factory recommendations.  I can adjust each amp’s volume  independently to control the tonal balance.  I set the volume on the CD for 3 (out of 20).  I adjust the gain on the RMX amp and finally set the volume on the HK amp.  Wonderful sound, rich balanced, with powerful bass.  I play Dire Straits, Sultans of Swing and Everlast, Eat at Whiteys.  Great bass.  I will describe it like this:  If you’ve ever been swimming in the ocean, dense water, and heard a motorboat, not through your ears but through your neck, that is the kind of bass.  The bass is so good I can even enjoy listening to rap.  Eat at Whiteys has some if you're familar with the CD.  

Each different CD has a completely different recording mix and style.  I can very easily and quickly adjust to it by adjusting the volume of the ribbons up or down, and then resetting the master volume (on the CD player) to taste.  I am getting there.  The bass is rich, powerful and controlled.  The mid bass still has some work to do, a bit loose and kinda rattles on occasion, probably need to adjust the PW.  The treble is strong and clean, but not overwhelming.  The last traces of ssshhhing on the very high frequencies are almost gone.  Each little cymbal tap and snare strike are excruciatingly detailed.  A good new amp and speaker wires for the ribbons should clean that up.  I will get into a detailed sound description on another thread when I get a new amp/pre-amp.

Conclusions:  Bi-amping is a double edged sword.  It introduces a whole bunch of problems like polarity inversions and timing issues, but it adds a tremendous amount of dynamics.  I will not live without it.  When running with one amp, the ribbons are just too hot compared to the bass IMO, unless you have an under powered amp.  Also, the recording mixes from CD to CD vary wildly and you need to be able to quickly and easily adjust for this, adjusting the pots on the back of the spekers for each CD is not an option.

Questions:

1)   Is there any way to directly measure the polarity
                    of the speaker output, with say a voltmeter ?

2)   Are there any good balanced pre-amps that have

   a)   Dual balanced XLR outputs
   b)   One volume control for both channels, tone controls
                    (optional), balance control (optional)

3)   Is there a good, high quality ss amp that has gain controls
                    on it, or should I go with an integrated amp for the
                    ribbons ?

4)                 There are two pots on the back of the RM40.  The right one
                    adjusts the tweeter only and the left one the four ribbons.  
                    Is that correct ?  Exactly what do these pots adjust ?  Do
                    either of them directly affect the Mid Woofer ?

5)                 Is there a crossover between the Mega Woofer and the Mid
                    Woofer ? Is there a crossover between the tweeter and the
                    four ribbons ?  Are these the only two crossovers ?

[Andrikos]

The answer to 1) is:
use a 9V battery (its terminals fit nicely to speakers' terminals).
Put it one way: positive of battery to positive of speaker, the cone should move OUT. Positive of battery to negative of speaker, the speaker should move IN.

[zybar]

I did the same thing with my bi-amp setup.

Every other speaker, the bass outputs have been the bottom pair, not here!

I am still not getting the bass you are talking about, but it has significantly improved.

Now I have to start playing with the pr and the putty  

So far I have only taken about half a pea's worth.  I know I am supposed to take more off, but I actually need to bass to tighten as well as get deeper.  

How much putty have you taken off?

So what do you have your pots at now?

GW

[Redbone]

Okay, my writing skills must need work because nobody's understanding me.  

Andrikos - What I am trying to measure is the polarity of the amp output, not the speaker (which is well marked).  I am concerned that one of my amps may reverse the polarity of the speaker output leaving me with an out of phase set up.  I have tried reversing the polarity of the speaker leads on one amp, and it sounded much worse, so I am confident that I have it correct, but I would like to get an undisputable reading on this.

zybar - I didn't hook the powerful (RMX) amp up to the ribbons and the weak (HK) amp up to the woofers.  What I did was to get the left channel of the RMX playing together with the right channel of the HK, on the same speaker !  Terrible sound.  Think about, it's easy to do especially when the HK is marked left and right, the RMX one and two.

In order to get really outstanding bass you have to be able to independently adjust the gain (volume) of each amp, one powering the ribbons and the other powering the woofers.  If you leave it entirely to adjusting the pots and PR, disappointment awaits.  I can turn up the gain on my RMX until the RM40s are booming like some teenager's car playing rap, or I can adjust it down to an old man's concerto playing Beethoven, my call.

Currently I have the factory recs on the pots.  The right one is at 1 o'clock, the left one at 12 o'clock.  I have removed four fingernail scapings of mortite from each passive woofer, it is volume wise the size of 1/2 a pea from each speaker.

Update, I just checked the amount of mortite.  It is just larger than a BB removed from each speaker.

[randog]

The answer to 1) is:
use a 9V battery (its terminals fit nicely to speakers' terminals).
Put it one way: positive of battery to positive of speaker, the cone should move OUT. Positive of battery to negative of speaker, the speaker should move IN.

Great tip! Andrikos, is that safe to do on any speaker? You are talking about the little rectangular 9V batteries, right?

Randog

[jgubman]

I'm just running my RM-40s w/ a single amp, a Earthquake Cinenova 3-channel, 600w / channel @ 4ohms, which has sounded very grainy ever since I hooked up the RM-40s.

Anyway, I wound up tuning my pots down to about 11 (mid) and 11:15 (treble) and took out a BUNCH of mortite, wound up being about a 1/2 marble sized chunk for each speaker.

It's tricky business tuning these.

[Redbone]

I'm just running my RM-40s w/ a single amp, a Earthquake Cinenova 3-channel, 600w / channel @ 4ohms, which has sounded very grainy ever since I hooked up the RM-40s.

Anyway, I wound up tuning my pots down to about 11 (mid) and 11:15 (treble) and took out a BUNCH of mortite, wound up being about a 1/2 marble sized chunk for each speaker.

It's tricky business tuning these.

I am thinking that the more powerful the amp, the more mortite that needs to be removed.  My reasoning is that a more powerful amp causes the cones to move more.  The greater movement shifts the resonance mass towards less mass because too much slows or dampens the movement.  A weaker amp doesn't move the cones as much.  But if this were true, then the resonance mass should change with the amp volume as well.  

It may have more to do with a powerful amp being able to generate lower frequency waves.  Let's see, frequency is inversely proportional to wavelength, a lower (smaller) frequency means a longer (greater) wavelength.  Okay, now I'm confused.  Bring in the rocket scientists.  

A tricky business indeed.

[Tyson]

I think it has more to do w/the amps' damping ability - an amp w/more damping will require more putty removal, an amp with less damping will require less.  Either way, it's a fairly involved process to get it right.  After you've done it a few times (you have to re-do it everytime you change anything in your system, including interconnects and speaker wire), you get pretty good at zero-ing on what needs to be done as far as removal/addition.

[Redbone]

I think it has more to do w/the amps' damping ability - an amp w/more damping will require more putty removal, an amp with less damping will require less.  Either way, it's a fairly involved process to get it right.  After you've done it a few times (you have to re-do it everytime you change anything in your system, including interconnects and speaker wire), you get pretty good at zero-ing on what needs to be done as far as removal/addition.

Okay, I'll buy that.  Now what exactly is damping ?

[zybar]

Tyson,

Do you know what is good figure for dampening ability?

The Adcom I am using is listed as greater than 800.  I think this is good.

I just took a little more putty off and it is getting better  

The tuning continues...

GW

[Tyson]

Every amp has a spec called damping factor.  Generally the higher this number the better bass control it has, the lower the number, the less control.  Since amps with high damping can lead to bass that is overdamped, a bit more putty has to be removed to get the bass to a natural balance.  Likewise, amps with too low damping can have fuzzy boomy bass, which means that more putty should be left on.  And of course a lot of this will come down to personal taste.  I've tuned my speakers to be a bit bigger in the bass than what would be considered perfectly flat.  Still tight, but a little but more prominent than my headphones bass presentation (which are flat to 15 hz).  Tuning it like making chili, you have flavor to taste. . .

[Redbone]

From http://pssaudio.com/english/1art010.htm

It should be obvious at this point that the quoted damping factor of an amplifier is important only if the figure lies somewhere below 20 or so. Changing the damping factor from 2 to 20 does change the performance of the loudspeaker system (for better or for worse, depending upon the speaker). But trying to prove that a damping factor of 200 or even more is somehow better than one of 20 is pretty unconvincing because the effective difference in the practical case cited is only that between 1,25 and 1.32.

But someone is bound to insist that exhaustive tests have been made with such and such amplifier and that a very high damping factor is better than one down around 10 or 15. “The bass is just a little cleaner, just a little more natural and open”, is the way the argument usually runs.

In a given situation, this may very well be true. Rs is a byproduct of negative feedback. The more such feedback that is thrown into a power amplifier circuit, the lower the generator impedance and the higher the damping factor. The point is simply that if a lot of feedback has to be used to lick the distortion in a particular circuit, fine – use it. But don’t believe that the reason it sounds good because of some astronomically high damping factor.

[warnerwh]

Being as you guys are new to this how about trying this. Take your time and keep removing putty until the bass is getting boomy or the mids become fuzzy, then add some back to make it right again. If you move your speakers more than an inch or two during this time then you need to start over again.  After awhile you'll learn how good the speakers can be but I think it takes time for most of us to get a good handle on it.  The speakers can sound quite good right out of the box but with a little work can sound much better, or much worse so take your time and just enjoy the process.

[rkapadia@ROOP]

I think warnerwh has a good start on the subject.  The beautiful thing about the putty is you can just stick it back on if you've gone too far - there's zero liability to messing up here (other than starting over).

I'd like to add on a little bit to those setup tips - depending on the amplifier/system, the amount of putty that can make the "Ah ha!" change can be anywhere from a fingernail to a small pea.  Unfortunately, if you take off too much, you may not be able to hear the difference between "too much putty" and "too little putty".

I'd recommend that if this is the case, try progressively smaller increments every time you start over.  Even if it takes four or 5 times of going through fully, this method will probably be a lot quicker than removing a finger nail at a time.  Also, you probably want to put a track on repeat with a lot of low bass and sub bass energy - tympani, piano recordings work well for me. Alternately, techno tracks work well because the fundamental beat never changes in sound, so you can guage how the sound of the beat adjusts as you remove more putty.

Regards,

[Redbone]

I think warnerwh has a good start on the subject.  The beautiful thing about the putty is you can just stick it back on if you've gone too far - there's zero liability to messing up here (other than starting over).

I'd like to add on a little bit to those setup tips - depending on the amplifier/system, the amount of putty that can make the "Ah ha!" change can be anywhere from a fingernail to a small pea.  Unfortunately, if you take off too much, you may not be able to hear the difference between "too muc ...

Thanks, good advice.  My technique evolved into removing some putty, adding it to the total chunk removed so far from the speaker, and then alternately replacing and removing the whole chunk.  Until I got to a substantial amount of putty, I really couldn't hear any difference.

[Andrikos]

The answer to 1) is:
use a 9V battery (its terminals fit nicely to speakers' terminals).
Put it one way: positive of battery to positive of speaker, the cone should move OUT. Positive of battery to negative of speaker, the speaker should move IN.

Great tip! Andrikos, is that safe to do on any speaker? You are talking about the little rectangular 9V batteries, right?

Randog

Randog,
It's perfectly safe, in an 8ohm DC load, you'll get a little over an amp from the battery into the speaker (9V / 8ohms). However, the battery doesn't really have the current capability to do this. Even if it did, it'd be perfectly safe.

[warnerwh]

Redbone: Try listening to the midrange for smoothness and richness, this area can definitely become fuzzy if too much is removed and may be easier for you to hear the difference.   I suspect after a while you will become more attuned to the subtle changes.  The difference between excellence and not near as smooth is only a few fingernails full.  Cheers

[Redbone]

Redbone: Try listening to the midrange for smoothness and richness, this area can definitely become fuzzy if too much is removed and may be easier for you to hear the difference.   I suspect after a while you will become more attuned to the subtle changes.  The difference between excellence and not near as smooth is only a few fingernails full.  Cheers

Thanks.  So far I am having trouble noticing the changes when removing putty but I can definately hear that the midrange is kinda grainy like an old 78 record.  I will experiment some more when I get a free day.    Thanks again.

[zybar]

Redbone,

Don't forget the pots as well.  I turned the pots up a little bit and this helped get rid of some of the grain.  After changing the pots I went back and had to adjust the pr again.

I am having some friends over this weekend for the first listen to the 40's.  I am sure there were be lots of adjustments...

GW

[John Casler]

I'm just running my RM-40s w/ a single amp, a Earthquake Cinenova 3-channel, 600w / channel @ 4ohms, which has sounded very grainy ever since I hooked up the RM-40s.

Hi Jon,

That is strange.  I run the CineNova 3 channel too and while it isn't the AMPzilla, it is "very" detailed and clean.

Aren't you running the Lexicon? for the front end?

I have the a Bryston Pre and just tried the Eastern Electric MiniMax and both are sounding sweet and real.

What CDP are you using?