[GeorgeAb]

I adore my RM-V60 the harmonics (where the music is at) that ribbons convey and enough drivers not to break up at high SPLs. Additionally, the depth the di-pole V-60 midrange achieve make them quite different from the other speakers in the RM line. I did have an issue with the soundstage in the vertical bass section sounding compressed. It is all there, it just seems the layers are squashed. I kept looking at the bass drivers being 5.5” from center of driver to floor as being the likely culprit. There is also the side drivers in the V going to the sides. For imaging it is difficult enough controlling reflections from one direction. It was good enough for me to be happy, but it seemed I could milk some more performance out in this area. Raising them up would likely improve the issue, but in my mind was a compromise. So I kept coming back to changing the bass section. Greg user @G E reached out asking about differences of the RM-30 and RM-V60 and it motivated me to readdress this area as this was not an issue with RM-30’s or RM-40’s. The audio sage @oldhvymech has a pair of Elixer’s; I reached out to Scotty as I had remember he had modified by replacing the bass section among other things (see here: https://systems.audiogon.com/systems/8764). Thanks Scotty @oldhvymech for leading the way.

So I resolved to doing an experiment of changing out the bass section. Design constraints were working in same range of 70Hz to 230Hz with same passive XO or active XO (which I use), and not take a large footprint as there is limited space with the V-60 and two large subs. I looked at open baffle U designs as they should pair well with the di-pole midrange. The problems encountered is to get to 70Hz you need larger drivers (footprint gets big fast) and getting the SPL to match the midrange would be a challenge. So a more conventional design was chosen.  So I started sketching out a design, but saw a pair of speakers for sale locally that where pretty much already what I was thinking. The Definitive Audio BP-10B was a 8”X12’X43”, with 1” front and rear MDF and ¾” on sides, a little over 60 pounds and the 6.5” Misco drivers we use would drop in. Since it bi-polar design it has MDF separating the front and back running through the middle of speaker so nice and tight cabinet. $200 for an experiment was all I needed as I could always gift them to somebody. Plan was to try them out before cutting them up, if positive results add a couple 6.5” holes for drivers.

So onward with the experiment. Removed XO threw the Misco drivers in front and rear wired in bi-pole (both speakers in phase as opposed to di-pole (out of phase)).  Was able to get close to comparable SPL’s from stock bass section with only two drivers by adjusting gain on active XO. It was clear and obvious that this solved the issue I was trying to resolve. This is a big upgrade IMO.

I am in the next phase of plugging tweeter holes, and adding two more 6.5” holes spaced 9” from centers.  Analysis hook up wire is on order and will configure same as stock bass section of one driver in parallel with two series drivers. I am not going to plug the rear speaker hole, but will have a plate. I am going to try adding a rear speaker and configuring in di-pole and bi-pole configuration to hear what happens as I think that would pair well with the di-pole midrange. On cosmetics, not sure if I will cover with sock, or have drivers exposed, or veneer with Macassar ebony…. all things down the line. 

I will keep you posted on my progress. RM-V60 owners this is a significant upgrade, and the Definitive Audio’s BP-10 are readily available and a good choice for a fairly easy, cheap, decent looking conversion.   

[John Casler]

 

Don't tell Shaukat, Paul and Dave. . . . .LOL

[Stimpy]

The BP-10s do put the 6.5' Misco driver at roughly ear height.  That has to have an impact on sound quality.  Probably why double stacked woofer cabinets were an upgrade.

Also, I wouldn't do any mods to the RM-V60 woofer cabinet, as that would hurt resale value, it that was ever a future need.  But, dropping the woofers into a taller separate cabinet, raises no issues.  Heck, you could even add passive radiators, to tune the bass on your new mid-bass towers.

Keep us updated!  Well done.   

[GeorgeAb]

Thanks Stimpy.

Completed modifying the cabinets. Woodworking is not really my forte, but they came out nice. Those four tweeter plugs took some time. It would of been fine leaving the tweeters in disconnected to fill the holes, but knowing me seeing them would likely have driven me to madness over time. Definitely resolved a design challenge for this particular speaker that bothered me. Really pleased I was able to correct.   

Have not plugged the rear 6.5" driver hole, just have a driver stuck in there. Drivers are configured as the speakers were designed. Plan to experiment by adding rear facing driver and configure as di-pole and bi-pole to see how it pairs with the di-pole mid range. From there either plug hole or keep rear firing driver. For now just want to enjoy the fruits of the past few days of work. 

[GeorgeAb]

Epilogue:

So after experimenting with four misco drivers in various configurations, I found the best configuration was as Brian designed three drivers; one driver in parallel with two series drivers. That gave me the most SPL and allowed me to keep within the design constraints of using passive XO and still be integrated with mids/tweets.

Hiccups. After committing to configuration and wiring up with Analysis Plus hookup wire, I found a channel was 4 dB down. After checking the configuration, driver polarity and SPL of individual drivers determined nothing was wrong with speakers. Troubleshot issue to active XO which had a defective Op amp. That issue really got me chasing my tail as it seemed it had to be the speakers. Not sure how long it has been that way nor how we got by before Room EQ Wizard (REW).   

Bass speakers do not need to be close to ear level like tweeters, but just not on the floor. Understood Brian had only so much room with six ribbon panels per speaker. This is a worthwhile modification as it resolves a design compromise as the soundstage in the vertical is no longer compressed. More work than I thought, but real happy with outcome.

[Housteau]

Don't tell Shaukat, Paul and Dave. . . . .LOL

Too late for that John, for here I be .  This looks to be a very interesting and fun project.  I understand where you are coming from in doing this.  However, I took a different approach and worked with what I had to correct things.  First off I think it is important for me to state that I feel all well put together systems are functions of the room, listener and speaker interface.  Meaning that they are all different and what may work in one situation may not work as well for another.

I do have a very good listening room with near ideal ratios and a tall ceiling.  The brain determines what we finally hear.  The ears gather acoustic information, but also often mixes that with what our eyes see.  I have been in narrow listening rooms with low ceilings and what I heard was pretty much what I saw.  Yes, I am sure that the acoustic cues also cried out low, narrow and compressed, but had I been blindfolded it may not have felt so extreme.  On the opposite side a larger room with a cathedral ceiling properly treated lends itself to the potential of hearing the more majestic by both the visual and auditory cues.  The system can simply breath better in all directions and the scattering of the higher frequencies by the ceiling treatments help to allow the height information in the recordings to come through.

Originally, I did see a dip in the upper bass response when charting the system to the room. My fix was to deviate from the recommended crossover points for my active crossover.  First, my upper bass pedestal is set to roll off naturally on the bottom and at 250Hz @ 18dB on top.  Then, the upper range section rolls in at 266Hz @ 6dB.  Finally, I run the bass towers a bit higher to 100Hz and roll them off @ 24dB.  This allows my system to speak with a single voice to a near flat frequency response of +- 2-3dB from 22Hz to 120Hz and then mostly the same up to 600Hz with the occasional narrow notch of +- 4db.  My crossover is the Xilica XP-4080.  It does allow very fine manual and precise DSP corrections.  I am using several to achieve those numbers, but they are mostly all below 3dB here and there.

I do not run any kind of a house curve and find that a flat response in the bass to most realistically portray acoustic instruments such as a stand-up bass.  Being triamped I do have the ability to vary the levels between each to taste, but more often than not they stay right at close to flat from 20Hz to 20K.  However, I am using what is sometimes called the BBC dip.  This is a broad dip (Q of 1) around 2100Hz by 2-3dB.  Many manufacturers build this into their crossovers.  Brian had suggested it for active crossovers because he felt the midrange drivers to have a bit too much presence.  What this dip does is help to create more depth of field.  Images such as voices once even with, or slightly in front of the speakers are now further back behind them.  This creates separation front to back with some remaining even the speakers while others are clearly out in front.  On systems displaying good width these out in front images can often extend beyond the width of the room to coming back along the side walls towards the listener.  It is not unusual for all properly set up systems to be able to do these things to a point, but that BBC dip can enhance them, in height as well.

The elephant in the room is very often the room itself.  But, it can also be the source component.  If the speakers are not being given the correct spatial information, then how can they be expected to present it?  This information needs to come from a high quality source.  Not all dacs can produce this same magic.  I recently upgraded to a Holo Audio May dac and to their Serene preamp.  The combination is truly holographic as I have never experienced.  They simply sound real.

If my listening chair was at a different height, or if the speakers had a slight tilt I could see how an image could be subject to a different placement.  But, in having my system and room set up the way I do now, I do not find anything lacking in presentation.  Not long ago I spent a few days in Houston and New Orleans listening to different MBL systems from the 101E to the Extremes.  I was very impressed.  I also listened to a well set up pair of GR Research's NX-Treme's.  In truth I thought that they did not sound far off from the MBL's in general presentation at all.  I think they are true giant killers.  Coming home I thought would be a most humbling experience as it often was from events such as those.  But, not this time.  As I started to listen I found myself in very good company.  All of the systems had a very similar open holographic signature.

   

[Rob Babcock]

Man, those are beautiful!

[Housteau]

Man, those are beautiful!

The V60 had started out as a secret development project.  As images were slowly posted over time, I was taken with them right away.  Then when it was let out that matching bass columns were planned, well that was it and I had to have them.  I became one of the first to order them and the second to receive them.  I was able to catch the bass towers early in their development and was able to suggest a design thought that Brian went through with.  Originally they were to made similar to previous older tower designs with a single large grill cover on the front.  I had suggested that they should have individual driver covers to match the bass pedestal on the V60.  I became the first to receive those towers and just love how they match the V60.

This system was such a high value for that time.  I can't imagine trying to replace it in todays market.  Costs were crazy back then, but today they are just insane.

[GeorgeAb]

I do not run any kind of a house curve and find that a flat response in the bass to most realistically portray acoustic instruments such as a stand-up bass.   

I recently upgraded to a Holo Audio May dac and to their Serene preamp.  The combination is truly holographic as I have never experienced.  They simply sound real.

Concur with running a perceived flat response. Just want to provide input on the house curve being perceived as bass boost as it is not. A house curve is a perceived flat response at the listening position. Understand how it can look like bass boost when you look at the house curve, but the slope starting at 20Hz is a -3dB/octave low pass filter. The graph you provided for your setup shows a house curve. The reason it appears flat is you likely used pink noise as the signal input and pink noise uses an approximate -1 to -3 dB/octave low pass filter (equal energy per octave). So we are talking the same thing. My bad, engineers like to use fancy language; should have stated “I DSP to a flat perceived response at the listening position”.

On a related note. I have measured RM-30, RM-40, and RM-V60 using Room EQ Wizard and little DSP is required to get a perceived flat response other than the neo-panel's 1.9K Hz bump (per Brian 2.9dB at 1.9K Hz, Q of 2.6) and the peaks and troughs from the lower frequency range reacting to room dimensions. Quite a testament to Brian’s skills of getting drivers to integrate with each other using only nine components in the crossover. 

Congrats on the D/A converter and preamp. Just checked them out on Holo Audio's website. They make beautiful looking gear. If they sound half as good as they look it should be amazing.

Happy listening,
George

[Housteau]

A house curve is a perceived flat response at the listening position. Understand how it can look like bass boost when you look at the house curve, but the slope starting at 20Hz is a -3dB/octave low pass filter. The graph you provided for your setup shows a house curve. The reason it appears flat is you likely used pink noise as the signal input and pink noise uses an approximate -1 to -3 dB/octave low pass filter (equal energy per octave). So we are talking the same thing. My bad, engineers like to use fancy language; should have stated “I DSP to a flat perceived response at the listening position”.

Congrats on the D/A converter and preamp. Just checked them out on Holo Audio's website. They make beautiful looking gear. If they sound half as good as they look it should be amazing.

I consider the pink noise flat response as the accepted norm and may have incorrectly used the phrase of House Curve to describe a deviation from that norm for different custom created response curves.  They almost always involve a rising low end to suit individual tastes.

That Holo Audio May dac received an A+ from Stereophile, but if you get the chance check out the different YouTube video reviews.  Those are what really pointed me in that direction.

[shauk786]

George and Dave

Well done on your upgrades.   

Since coming back from the US in March, I am in the process of upgrading my apt. Work is in progress. Then need to make some re-arrangement of my speakers. I did get some new gear from USA such as a pair of nuprime evolution amps and the evolution dac as well as a Marchand crossover. I have yet to install them.

Coming soon.
Shaukat

[mresseguie]

George and Dave

Well done on your upgrades.   

Since coming back from the US in March, I am in the process of upgrading my apt. Work is in progress. Then need to make some re-arrangement of my speakers. I did get some new gear from USA such as a pair of nuprime evolution amps and the evolution dac as well as a Marchand crossover. I have yet to install them.

Coming soon.
Shaukat

Shaukat,

Hello. Congratulations on your recent move.

For the past 3 or 4 months, I have been enjoying my Evolution STA (dual mono) amp. It is a wonderful sounding amp - warm yet revealing. From all I have read, my Evo STA is but a 'little brother' to your Evolution One amps. Based on the beautiful music emanating from my speakers, I suspect you'll very much enjoy your new Evolution One amps. Enjoy!

I have not heard the Evolution DAC, but it is one of three DACs that have my attention. Could I trouble you to post your impressions of your new Evolution DAC once you've settled into your new residence?

Apologies as this is off topic.

Regards,

Michael   

[shauk786]

Michael, I surely will

Regards,
Shaukat