[brj]

I just had the chance to listen to an RM40 with spiral ribbon tweeters and TRT upgrade tonight.  (And might I offer a huge "thank you" to Xi-Trum for the opportunity!)  It was a thoroughly fun time and I was very impressed with the speakers.  Imaging like that is an absolute treat!

I do have a few questions, however.

1) Does the upgrade to the FST improve the width and/or height of the sweetspot significantly?  (I'm guessing perhaps the width, but probably not the height.)

2) Does the narrower baffle on the RM30M improve the width of the sweetspot significantly?

3) How sensitive are the RM30s in terms of room placement when compared to the RM40s?  I've read that they aren't as picky regarding the back wall, but what about the side walls and spread between speakers/listener?

All of my questions are aimed at trying to determine just how big a sweet spot I could get in my acoustically imperfect room with similarly imperfect placement.  Considering the distance between speaker baffles to be the base of a triangle and the distance from the driver plane to the sitting area the height of the triangle, I have the option of a speaker/listener triangle of roughly 7'x11' or 10'x15'.  In either case, I would have an isosceles triangle rather than equilateral.

Any speakers I finally purchase could be placed along a short or long wall in a large living room - 18'4" x 14'9" x 12' - that then connects to an open dining area and kitchen on one side and foyer on the other.  The short wall is much more convenient, but the long wall has the adjoining rooms off to either side and a more symmetrical "view" of the listening room itself.

Responses to any of the above questions would be appreciated!

[Redbone]

Most any new VMPS speaker you get will come with the FST Tweeter.  I have found that when new, the vertical focal range of this driver is very narrow, but that it widens over time.  My speakers are coming up on 4 months now, and the difference in sound quality between the sitting and standing positions has dwindled to very little.

Speaker placement is a bit more difficult.  There are just too many variables for me to give you any specific advice.  But I can give you some general advice.  First and foremost, these speakers are like women, they do not like to be stuck out of the way in the corner.  They like to be standing out in the room, away from the corners.  You can use a wall for bass reinforcement, but a corner will give you imaging trouble.  

Do not place the speakers too far apart, 8 feet seems to be about the max, I have no idea what the min is.  Do not toe them in more than about 20 degrees.  They do not have to be symetrically aligned, and may even sound better if they aren't, especially if the room is not symetrical.  Let them break in for 3 to 4 months before doing any final tuning.

[John Casler]

I do have a few questions, however.

1) Does the upgrade to the FST improve the width and/or height of the sweetspot significantly? (I'm guessing perhaps the width, but probably not the height.)

The FST tweeter "slightly" increases both horizontal and vertical dsipersion, but not enought to degrade the imaging.

2) Does the narrower baffle on the RM30M improve the width of the sweetspot significantly?

A narrower baffle will reduce what is called "baffle gain" or refraction.  The effect of reflected/refracted sonic energy from the VMPS speakers is generally much smaller than conventional drivers because ribbons tend to have "less" dispersion and subsequently a more focused image.

All speakers have dispersion, but the characteristics are what set them apart.  The reduction of "baffle gain" is one of the properties that actually "reduces" sonic spread or dispersion.  What it does is "improve" the "blackness" between instruments and performers, by not "fuzzing out" the sonic image.

Increasing the "sweet spot" on the other hand can only be accomplished by "increasing" the dilution of the signal.  But doing so will also "reduce" the precision of the image.  That is, a more dispersed (diluted) signal will have less blackness, and less definition.

To achieve a wider sweet spot with the RM40s or RM30s you need to set them up to be "forward cross firing".  That is they are converged 1-3 feet in front of your listening position.

This convergence will put you "off axis" and will require a slightly higher pot setting (up to 1-2 hours more)

What this does, is set up a listening signal balance so that as you move to the left you get further away from the right speaker, but more "off axis" to the left speaker.  This maintains the "balanced volume" of both more equally and creates a slightly wider sweet spot.  Same thing happens when moving to the right.

3) How sensitive are the RM30s in terms of room placement when compared to the RM40s? I've read that they aren't as picky regarding the back wall, but what about the side walls and spread between speakers/listener?

There are two main differences between the two as far as room interaction.

1) The baffle width
2) The woofer arrangement

Due to depth of both speakers, they both are well away from the front wall even with small offsets (1-2 feet)

The side wall interaction might be more of a concern depending on toe in (convergence angle) and distance from the side wall.

The side firing woofer of the RM30 will likely be augmented with a closer sidewall placement, but I have not had any reports of negative affects of closer placement.  

The woofer arrangement of the RM40 can work well with close sidewall set up but each room and set up will very.

what about the side walls and spread between speakers/listener?

With proper convergence angle, the width placement flexibility of both speakers is quite large.  With a well treated front wall, you can have a "very" flat triangle and still have a very deep and well formed soundstage.

In fact it is very much like wearing headphones...except you have the soundstage in front of you, not between your ears.

Any speakers I finally purchase could be placed along a short or long wall in a large living room - 18'4" x 14'9" x 12' - that then connects to an open dining area and kitchen on one side and foyer on the other. The short wall is much more convenient, but the long wall has the adjoining rooms off to either side and a more symmetrical "view" of the listening room itself.

I am a "Long wall" (no sidewall first reflections) advocate, with nearfield listening, but my listening preferences include, "soundstage, imaging, and depth" at the top of the list.

[ekovalsky]

Any speakers I finally purchase could be placed along a short or long wall in a large living room - 18'4" x 14'9" x 12' - that then connects to an open dining area and kitchen on one side and foyer on the other. The short wall is much more convenient, but the long wall has the adjoining rooms off to either side and a more symmetrical "view" of the listening room itself.

brj,

My room is similarly shaped and slightly smaller than yours at 14.5' x 17' x 10'.  The dimensions you have are actually pretty decent and you should get very good sound from the RM-30 or RM-40.

I would highly suggest trying the long wall placement, even though it may be less convenient.  You won't be able to get enough separation for best imaging on the short wall.  And I found symmetry in the room absolutely necessary for precise imaging.  My listening position is symmetric with the speakers on the long wall, and asymmetric on the short wall (one of the long walls has sliding wood and beveled glass doors over an 8' section -- so either a very reflective surface if closed or a perfectly absorptive surface if open).  The long wall placement for me is also somewhat inconvenient, my most of my dedicated outlets are on the short wall and the room is prewired for home theeater and best furniture arrangement with a short wall setup  

Also, don't make the mistake of pulling the speakers too far out from the wall behind them.  Better to keep them closer and treat the wall.  This should help with your decorating too, since it will double as a living room.  I got some attractive fabric covered absorbing panels from http://www.acousticsfirst.com for a pretty reasonable price.

Depending on your budget I'd hit the VMPS line card in the following order:  

1.  RM/X with TRT
2.  RM-40's with TRT & FST (still an option or now standard?) and internal bracing (i.e. Dorne's piano black or upcoming Chinese veneered wood cabinets)
3.  RM-30's with TRT.  If Jim's intiguing idea about biamping with an active crossover/EQ on the subs is viable, these may end being better than the RM-40's !!!

The Analysis-Plus silver woofer wire upgrade should also be considered.  I haven't been able to compare the same model with and without it, but the bass on my RM/X (which have the upgrade) is simply amazing!

This link has John Dunlavy's setup advice which I found very helpful.  I used it and to locate ideal positions pretty quickly

http://web.archive.org/web/20021005073746/www.dunlavyaudio.com/audio_files/listening.html

[brj]

Most any new VMPS speaker you get will come with the FST Tweeter. I have found that when new, the vertical focal range of this driver is very narrow, but that it widens over time. My speakers are coming up on 4 months now, and the difference in sound quality between the sitting and standing positions has dwindled to very little.

Which speakers do you have?  I believe that the RM40's (with spiral ribbon tweeters) that I listened too were over a year old and presumably well broken in.  They sounded fantastic in the sweet spot, but I noticed a definite change when transitioning from a sitting position to a standing, or when moving too far to the left or right.

The change wasn't so much the quality of the sound, but rather an apparent change in the volume balance between the lows and highs.  The lows appeared to remain at constant volume, while the highs appeared to diminish.  I think I could handle the vertical shift, but I would be comforted to hear that the upgrade to the FST reduces the volume shift due to lateral position changes.

Speaker placement is a bit more difficult. There are just too many variables for me to give you any specific advice. But I can give you some general advice. First and foremost, these speakers are like women, they do not like to be stuck out of the way in the corner.

 Somehow, I don't think I'll go out of my way to compare women to speakers... no matter how much I might love either one!

They like to be standing out in the room, away from the corners. You can use a wall for bass reinforcement, but a corner will give you imaging trouble.

In my case, a long wall placement would eliminate any real corners, as there are open entryways to either side (after 8 inch angled stub walls).  However, this is compromised by the fact that any real distance from the wall would put them in the main walkway of the room.  My short wall placement option has more freedom in placing the speakers further from the wall, but more sidewall problems.  Toss up!

Do not place the speakers too far apart, 8 feet seems to be about the max, I have no idea what the min is. Do not toe them in more than about 20 degrees. They do not have to be symetrically aligned, and may even sound better if they aren't, especially if the room is not symetrical. Let them break in for 3 to 4 months before doing any final tuning.

Do you still consider the 8 foot limit absolute when the listening position is quite a bit further out?

Thanks again for your insights, Redbone!

[brj]

Thanks for the response, John!

The FST tweeter "slightly" increases both horizontal and vertical dsipersion, but not enought to degrade the imaging.

Anything helps!

A narrower baffle will reduce what is called "baffle gain" or refraction. The effect of reflected/refracted sonic energy from the VMPS speakers is generally much smaller than conventional drivers because ribbons tend to have "less" dispersion and subsequently a more focused image.

All speakers have dispersion, but the characteristics are what set them apart. The reduction of "baffle gain" is one of the properties that actually "reduces" sonic spread or dispersion. What it does is "improve" the "blackness" between instruments and performers, by not "fuzzing out" the sonic image.

Increasing the "sweet spot" on the other hand can only be accomplished by "increasing" the dilution of the signal. But doing so will also "reduce" the precision of the image. That is, a more dispersed (diluted) signal will have less blackness, and less definition.

I can understand why you want to eliminate "baffle gain", as that dispersion is not part of the driver created signal and is a indeed a warping of that signal.

However, I would think that, for two drivers that radiate signals of equal quality, the driver that radiates the signal over a wider area (or perhaps arc) would create the wider sweet spot.  (Of course, to generate the same SPL at any given point, the "wide area/arc" driver would require more power.)

To achieve a wider sweet spot with the RM40s or RM30s you need to set them up to be "forward cross firing". That is they are converged 1-3 feet in front of your listening position.

This convergence will put you "off axis" and will require a slightly higher pot setting (up to 1-2 hours more)

What this does, is set up a listening signal balance so that as you move to the left you get further away from the right speaker, but more "off axis" to the left speaker. This maintains the "balanced volume" of both more equally and creates a slightly wider sweet spot. Same thing happens when moving to the right.

Ahhhh.... this sounds like an interesting technique to try.  The question is, why the pot adjustment?

My reasoning: The bass drivers spread signal over a wider area than the mids/tweeters.  Thus, when converging 1-3 feet in front of the listener, the listener is still within the primary arc of the bass output, but just outside that of the primary  mid/tweeter output - which will now appear too soft in volume as a result.  Increasing the mid/tweeter pots restores the balance between the on-axis bass output and the slightly off-axis mid/tweeter output.  The catch, however, is that as you move outside the (now slightly enlarged) sweetspot, you will enter a region where the mid/tweeters actually appear more prominant that the bass.

This concept doesn't seem like it would be particularly unique to VMPS speakers, or even ribbon speakers.  Is there a catch somewhere that I haven't seen that would explain why it isn't more commonly discussed?  (Of course, I could just be reading the wrong sources...)

3) How sensitive are the RM30s in terms of room placement when compared to the RM40s? I've read that they aren't as picky regarding the back wall, but what about the side walls and spread between speakers/listener?

There are two main differences between the two as far as room interaction.

1) The baffle width
2) The woofer arrangement

Due to depth of both speakers, they both are well away from the front wall even with small offsets (1-2 feet)

The side wall interaction might be more of a concern depending on toe in (convergence angle) and distance from the side wall.

The side firing woofer of the RM30 will likely be augmented with a closer sidewall placement, but I have not had any reports of negative affects of closer placement.

The woofer arrangement of the RM40 can work well with close sidewall set up but each room and set up will very.

It sounds like I wouldn't have to worry about rear wall spacing.  As for side wall spacing, it would only be a concern on the short wall configuration, and then only for the right speaker.

what about the side walls and spread between speakers/listener?

With proper convergence angle, the width placement flexibility of both speakers is quite large. With a well treated front wall, you can have a "very" flat triangle and still have a very deep and well formed soundstage.

In fact it is very much like wearing headphones...except you have the soundstage in front of you, not between your ears.

By "flat" do you mean a triangle with the long distance between left and right speakers, or the long distance between the speaker plane and the listener?

Any speakers I finally purchase could be placed along a short or long wall in a large living room - 18'4" x 14'9" x 12' - that then connects to an open dining area and kitchen on one side and foyer on the other. The short wall is much more convenient, but the long wall has the adjoining rooms off to either side and a more symmetrical "view" of the listening room itself.

I am a "Long wall" (no sidewall first reflections) advocate, with nearfield listening, but my listening preferences include, "soundstage, imaging, and depth" at the top of the list.

I have to admit that I am starting to find my preferences heading that way.  However, I want my guests to experience the same thing without having to give up my own seat in the sweetspot!

I may have a long wall option, but it won't really provide nearfield listening (15+ foot separation between speaker plane and listeners).  Consequently, I guess this will make room treatment more important.

Thanks again!


(ekovalsky, I'll have to get to your response tomorrow! )

[John Casler]

However, I would think that, for two drivers that radiate signals of equal quality, the driver that radiates the signal over a wider area (or perhaps arc) would create the wider sweet spot. (Of course, to generate the same SPL at any given point, the "wide area/arc" driver would require more power.)

Hi Brj,

Thus is the "cunundrum".  

"Equal quality" (IMHO) cannot be had with wide vs focused drivers when one is talking about "precision development" of a sonic image.

Wider dispersion means just that.  The sound is dispersed.  Diluted. Fogged out.  Less focused.

Much like the nozzle on a garden hose can be made to shoot in a stream or in a spray.

And in the dispersion comparisons, I have never heard a "higher dispersion" driver form a realistic soundstage in any position except in the sweet spot.

The only exceptions were the Bose 901s set up correctly, and then we all know that most of that soundstage was reflected sound, and the Gallo Nucleus Reference 360 degree radiating speakers in a totally acoustically treated room.

If we keep in mind that the ear brain relationship is such that "only" the balance of the left and right signals of the same amplitude will "project" the soundstage and its images, then moving laterally will degrade that balance (creating imbalance) and collapse the image to the dominant speaker.

Ahhhh.... this sounds like an interesting technique to try. The question is, why the pot adjustment?

My reasoning: The bass drivers spread signal over a wider area than the mids/tweeters. Thus, when converging 1-3 feet in front of the listener, the listener is still within the primary arc of the bass output, but just outside that of the primary mid/tweeter output - which will now appear too soft in volume as a result. Increasing the mid/tweeter pots restores the balance between the on-axis bass output and the slightly off-axis mid/tweeter output. The catch, however, is that as you move outside the (now slightly enlarged) sweetspot, you will enter a region where the mid/tweeters actually appear more prominant that the bass.

This concept doesn't seem like it would be particularly unique to VMPS speakers, or even ribbon speakers. Is there a catch somewhere that I haven't seen that would explain why it isn't more commonly discussed? (Of course, I could just be reading the wrong sources...)

You are correct and even my explaination is somewhat simplistic.  All sound disperses.  The lower the frequency, the more it sonically affects space around it.  The Higher frequencies can have a more focused or directed energy, but still disperse.  I am not aware of any real "laser focused" sound.

The increased pot setting suggestion is to compensate for the off axis position as you mentioned.  All my suggestions for system set up, are for one goal.. Sweet spot sound reproduction.

As far as the radiation/dispersion patterns being "discussed", I think that most conventional drivers offer radiation patterns wide enough to not make this an issue.

By "flat" do you mean a triangle with the long distance between left and right speakers, or the long distance between the speaker plane and the listener?

Yes, I meant a greater distance between the speakers and a shorter distance from the listener to the "center point" between the speakers.

For this to work however, the front wall (the one in front of you) "must" be totally treated acoustically.

John Casler wrote:
I am a "Long wall" (no sidewall first reflections) advocate, with nearfield listening, but my listening preferences include, "soundstage, imaging, and depth" at the top of the list.

brj wrote:
I have to admit that I am starting to find my preferences heading that way. However, I want my guests to experience the same thing without having to give up my own seat in the sweetspot!  

Such is the quandry of "audiophile listening".  The fact is, that there is only "one primary" sweet spot.  

While higher dispersion might "soften the edges" of that area and make OOS (out of spot) listening acceptable to some, it will, "never the less" be a lesser performance than "In The Spot".

In this hobby, where 99% of all serious listening is done "solo", and hundreds if not thousands of dollars are spent for the "absolute sound", I would suggest that the sacrifice in performance to get a wider lateral image 1-2% of the time might not be worth it.  Especially since it involves certain compromises.

While rather unconventional, my listening room has 3 seating positions (one in front of the other), that all offer a better quality of Soundstage and Imaging than any type of lateral seating arrangement.

Since ribbons are growing in popularity, this is an area that will be in contention more and more.

As a final point, it should be noted that larger rooms and farfield listening will offer a slightly broader sweet spot, by virtue of a larger angular dispersion due to distance and side wall reflection.

But again the sacrifice in perfromance includes reduced highs and increased room reflections.

Audio is getting tough

[zybar]

John,

I had the Gallo Nucleus Reference speakers for almost 5 years and I can say that thye did disappear like no other speaker I have owned...they had a few significant faults:

1.  The tweeter and the conventional woofers didn't blend seemlessly.
2.  The speakers although punchy, couldn't really move enough air.
3.  Much more sensitive to room placement than the 40's.

I loved these speakers and haven't owned another pair of speakers for as long a period of time, but I wouldn't go back to them (the 40's really are pretty darn good).

George

[John Casler]

John,

I had the Gallo Nucleus Reference speakers for almost 5 years and I can say that thye did disappear like no other speaker I have owned...they had a few significant faults:

1.  The tweeter and the conventional woofers didn't blend seemlessly.
2.  The speakers although punchy, couldn't really move enough air.
3.  Much more sensitive to room placement than the 40's.

I loved these speakers and haven't owned another pair of speakers for as long a period of time, but I wouldn't go back to them (the 40's really are pretty darn good).

George

Hi George,

That sounds about right.  Beleive it or not, I was a Dealer for those speakers too (never sold a single pair).

The only reason I mentioned them, was not their "overall" sound, but since they had a 360 degree dispersion, moving laterally didn't collapse the sound stage as quickly as a "point source" or "line source", system.

I met an AC and LA Audio Society member "Rustafarian" a week or two ago and I beleive he has some Gallo.

[PeteG]

I have a pair of Gallo Nucleus Reference speakers, and they didn't move
a lot of air but from the mid's up I really enjoy them. I put a pair of stereo
subs with the Gallos and they sound a lot better. As far as being sensitive to room placement, I always have to use lots of room treatment to take care of that and it works great with them.
I still can't get myself to sell them yet, one day I will.  I've had them for
7 years, longest I've owned any audio gear.