AudioCircle
Audio/Video Gear and Systems => Owner's Circles => VMPS Speakers => Topic started by: smoothrog on 7 Aug 2013, 08:02 pm
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VMPS Super Towers/R For Sale - Built in 1989 and still in very good condition with all paperwork. Morel tweeters and ribbon supertweeter. Detroit, MI. metro area only pick-up or drop off. $200
(http://www.audiocircle.com/image.php?id=84813)
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try posting those here:
http://www.audiocircle.com/index.php?board=104.0
they should go quickly at that price! Good luck with sale
gab
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Hello,
If your VMPS Tower/R are still available I would love them. I'm in Redford Twp/Livonia area.
Please call to talk at 313 937-8989
Sincerely, Doug
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Good luck Doug! And hopefully, nice score! That's a lot of speaker. I just wish they were near me, as I'd love to have a pair like that. Heck, pretty much any VMPS speaker would be worth it...!
Hello,
If your VMPS Tower/R are still available I would love them. I'm in Redford Twp/Livonia area.
Please call to talk at 313 937-8989
Sincerely, Doug
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Hey Stimpy,
How did those 4 graphite woofers work out for you ??? I am hopefull to take a listen to them Super Tower Rs Sunday.
DW
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Hello,
If your VMPS Tower/R are still available I would love them. I'm in Redford Twp/Livonia area.
Please call to talk at 313 937-8989
Sincerely, Doug
Doug, you're stealing those! Tip him accordingly! Those appear to be Brian's own mid range design, probably the best of all the cone mids he used, including the WCF.
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Hey James,
I wish I could enlarge the pics on this site. What did Brian do different with these midrange drivers ??? Glad to hear you liked this design knowing you worked side by side with Brian for many years. It means a lot. I'm eager to view/listen to them.
Sincerely, DW
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Hey James,
I wish I could enlarge the pics on this site. What did Brian do different with these midrange drivers ??? Glad to hear you liked this design knowing you worked side by side with Brian for many years. It means a lot. I'm eager to view/listen to them.
Sincerely, DW
Every other cone mid was some other OEM product: Audax HIF13JCAV...(forgot remainder of the model designation), Peerless, Versa Tronics. The only cone mid that came after Brian's own mid in this image (built by GEFCO) is the Versa Tronics WCF, which was an extra cost option sold concurrently with Brian's poly cone/stamped basket/gauze dust cap per the image.
The fact is WCF's best quality is its worst quality, being maximum self damping. Self damping eliminates extraneous noise and distortion. It sounds extremely natural. But it also overly damps dynamics. Brian's cone mid sounds snappier and more dynamic. If I had to choose among every mid Brian ever used (even the pleated "Dyna" and heaven forbid even both planar mids) I'd pick his Strathearn TRUE ribbon with transformer (.5 Ohm), then his own cone mid. The Neo panel is OK but only with its 1kHz peak fixed. Even then the Strathearn true ribbon kills the Neo panel but the Strathearn true ribbon is long gone.
There's nothing really "wrong" with the Morel domes but they just never rocked my world, even the MDT30. One of Brian's fetishes was to never employ LP on his mids till he finally reneged on the last planar Neo. If I had those speakers I'd listen to a small coil on the mids...they might benefit. It would be ideal to put a slightly larger coil on the lower cone but those are two 4 Ohm in series so they share crossover. This would require a lower tweeter pole. But I think it would audibly improve performance, especially with such great bass performance.
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For those following this tread, the VMPS Supertower/Rs have been SOLD. The speakers have found a new home hopefully for another 25 years. Thank you for all your input and comments.
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The Neo panel is OK but only with its 1kHz peak fixed...
Can you expand on this a bit please? Was this "fixed" on any production models, and/or are there a bunch of VMPS RM's out there with sub-optimal Neopanels? If so, what is the fix?
Thank you!
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Thanks to Smoothrog and his wife for their hospitality on Sunday. It was indeed a road trip way across town but well worth it. Never have been on the island so kind of fun with the ferry ride and the beautiful waterfront views etc. I could retire there very easily too. Very nice home and setting.
Roger the ST/Rs are in good hands, have found a good home with my other VMPS playmates, my 626 stand mount monitors, and my RM-1s. How did all this occur ??? I suppose mainly because I just dig the VMPS signature in tone and robust detail. Brian was a genius pure and simple. How he was able to put Hi-End loudspeakers into the homes of the common man/women at a price point well below his competitors sometimes 3-4 fold is beyond me. Brian is a legend in this industry and is sorely missed. His legacy will surely continue in coming years.
I contacted another loudspeaker legend this morning, Bill at Millerspkr.com to re-foam my ST/R drivers. Rest assured they will be done perfectly and balanced for another 20 some years. As always, thanks MR. Bill for your magic fingers and hands. Going to get both 15" woofers and passives done now, the 12" Mid-couplers are probably on their last legs and will need help soon also. These are in super condition other than the foam .... age takes its toll. Very pleased to be their caretaker for now, eager to get them back up and running.
Shear Bliss > DW
(http://www.audiocircle.com/image.php?id=85287)
(http://www.audiocircle.com/image.php?id=85288)
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Wow, they look just about factory fresh, congrats.
Spray the L pads with Caig Pro Gold, but listen to it first before you do it. You'll fall out of your chair.
Also clean every single contact you can access in your entire system.
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Thanks James, will do. Also do you recall the putty loading on these ??? I'm thinking maybe a 8 inch coil, don't recall Brian ever using more. Perhaps I"ll get a better idea once I pull the passives.
Thanks again James,
Shear Bliss > DW
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Of all the VMPS supertweeters, only two were better than that Asian clone of the original JVC planar: the original JVC planar was slightly better (earlier) and the large Philips planar (later) was better (at least equal to the original JVC). We must have went through a thousand of those clones. He crossed them right, 2nd order about 12 kHz.
PR mass changed more often than Brian's shirts (almost). During that era, IIRC, PR mass is 1oz fishing weight (glued to PR cone center) plus about 4" length of single strand gray rope putty.
Check how close I am. BTW, I may certainly have assembled that pair, which is early-mid 90s IIRC. Brian tended to insert driver screws at hard angle, me more vertical. Check the screw angles.
I talked with another great speaker designer and we agree it's ideal to stagger (not match) PR mass between channels. As ST/R owners know, they go super deep, low 20s for sure, if in decent condition.
I don't know the owner's age and I don't know if the following is possible, likely not: no matter how good the foam it rots faster than rubber. If your guy can approximate the foam surround compliance with rubber, consider rubber depending on cost of course.
VMPS fans will love this: when I owned that model (heck that might be my old speakers!) I lived in a townhouse connected on two sides. The guy W of me was a drug dealer, but he was really nice, never any crazy parties, very low key, no craziness, just a mellow guy who rode bikes like I did my whole life and liked beer. His clients were quiet and friendly enough. Just dope AFAIK, nothing heavier than that I suspect.
Even though the floor was slab, you can imagine how those flex sheet rock walls.
One night I cranked the towers with a Sota TT (they don't feed back). He later told me, very casually, he had guests over and his painting on his wall fell off its hook! He wasn't even mad. That's why I liked that guy.
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Doug,
Not just a nice score, that's an awesome score! I'm glad that everything worked out for you. Also, once the woofers have fresh surrounds (good choice using Millersound), and the speakers are up and running, I'd love to hear how they compare to your RM-1's and 626's. Curious how the cone mids hold up to the Neo's?
Now, if I could get my butt in gear, and do something with your woofers, I'd be happy! There just never seems to be enough hours in a day... May be a winter project; no grass to cut then...
Oh yea, vitrify the passive radiator's before reinstalling them. That's supposed to improve the bass response.
Take care,
Stimpy
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Hi,
Great score on these speakers. I've read that Millersound does great work and you should be able to get these speakers back into really good working order.
Cheers Rod
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Is it possible to maintain driver parameters while changing from foam to rubber surround? Does Miller offer such an option?
In case you didn't know, the biwire/biamp split is between the mid/treble vs. the typical bass/mid split. This makes it virtually impossible to biamp with different amps.
Overall I don't think RM1 or 626 hold a candle to proper running ST/R, regardless of any perceived midrange advantage of the two former models.
Sorry, I can't remember if the xo has electrolytic capacitors. If it does, it seems prudent to replace them for shelf life. What is manufacture date on the documentation near the terminal boards? Electrolytic shelf life is as little as 15 years. There are three capacitor banks, all series: mid, treble, planar. He normally wrote, with Sharpie black pen, the proper cap value on one of the caps per bank. You could cut open one end of each cap bank and measure the value, comparing the value to the pen mark and/or compare channels one to another. This would tell you whether/how much the value strayed. This definitely affects performance and reliability (power handling if pole is lower than spec.)
Forget about the coils, they're all fine.
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Hey James,
Not really concerned with converting the surrounds over, they were designed as foam, will stay that way. These made it 23 years so in my basement cave should do just great. Bill will do them correct and properly balanced, not some backyard hack job.
Pretty bummed to hear I can not Bi-Amp these with different amps thou. My RM-1s fit my room and sound just fantastic running a Crown K1 on the bottom with a 30 watt Antique Sound Labs tube amp on top. Quite a power disparity top to bottom, but I use the K1s attenuators to balance everything out.
James do you think Vitrifing the passives on the ST/R is worthwhile or just leave alone ??? Pretty funny on the loading with 1oz weight and 4" of putty.
As always thanks for your insight on Brians VMPS designs.
Sincerely, DW
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yeah, I don't know about you, but I've not met anyone over 100 so middle age is a memory. It's not like I need woofers to last another 40 years, so I get your feeling about the foam. It was more just a curiosity. One would presume big change in driver parameters upon changing the surround material.
The pole of the biwire/biamp split is a result of Brian's so-called "QSO" quasi-2nd order crossover, with two parallel woofers in series with two series 4 Ohm mids. So your biwire/biamp split is way too high for disparate amps, between the mid/treble. Brian NEVER added a LP pole to any cone mid, so that pole is about 4k-5k Hz. (In fact he never added a LP pole to any mid till he was practically coerced into it on the last Neo planar mid...which did improve performance BTW.)
You can imagine how strange it would sound with two completely amplifier technologies split below and above such a high pole frequency.
I later wondered if Brian's primary goal in his implementation of QSO was to save money on crossover parts. His implementation requires far less capacitor series value for a given midrange HP pole. I thought performance would improve, though cost would also go up, if he implemented the QSO between the mid/treble. This would move the biwire/biamp split where it normally is between the bass/mid.
The thing is, though, that Brian's bass LP pole frequency is so high that it would still probably be too high to employ different amps. Put your ear close to the 2710 mid bass and you'll hear a LOT of midrange output, probably more than any other speaker I've heard.
Brian got away with it because tere is so much powerful deep bass to go along with the mid bass extending up so high. That ST/R goes lower than just about any VMPS full range model lacking 15s. The only possible exception is the largest towers with multiple 12s, but if you test them next to each other the ST/R makes more power in the low 20s I'm almost positive. I'd bet lunch money absolutely no version of any 10 he ever sold goes that low with that much clean power. How could it?
Like Bert Whyte said in the late 70s, "It's not whether VMPS is ready for the digital age, but whether the digital age is ready for VMPS."
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Yes, changing surrounds will affect the woofers parameters, but so does the normal aging of the driver itself, including the surround and the spider. In fact all foam surrounds are not remotely identical. Most replacement foam surrounds will be different than what was originally used and may also slightly change parameters.
And no one should ever think that rubber surrounds are somehow superior to foam surrounds, because most rubber surrounds will dry out, stiffen up and crack. I own a basement full of vintage speakers, and while the foam does eventually need replacing due to foam rot, many of the woofers in my collection that are 25 years old or older almost all need re-surrounding as well because the rubber is no longer as pliant as it used to be. In that respect it may be better that older high end speakers did use foam because it is pretty to see when surrounds need replaced while the rubber surrounds will merely change the speakers performance over time and most people won’t even think there is a problem.
Most modern foam surrounds are treated with anti-fungal agents and will probably last as long, or longer than most rubber surrounds.
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Those are very interesting and helpful observations. How might you compare the quality of the rubber used in modern surrounds vs. the rubber used circa mid 80s?
A lot more potential speaker owners live nearer the equator rather than farther. I presume any longevity advantage of rubber vs. foam is far greater in such environment, where foam might visibly degrade very quickly.
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Well you're correct about the affect of climate on any mechanical device, and that includes all of the soft parts of a speaker. I would suspect that humid environments would be more damaging to even the newer foam surrounds, but I would also suspect that anyone who is an audio nut will probably have pretty good climate control in their homes. Most of my collection is in my basement, but my basement is quite dry and I also use 2 dehumidifiers to help keep the humidity in the range of 55-70% in Summer, and a humidifier to raise the humidity in Winter.
I'm sure the newer rubber surrounds will last better than most of the older ones, but I have a number of older woofers where the rubber surrounds have aged extremely well. Most people forget that the spider is also a major component that can age, and they usually do. They sometimes become brittle, but they can also remain quite pliant and even become more flexible with use, which would lower the Fs.
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Hi James and everyone else following this : The ST/R are FINALLY downstairs!!! Between the constant rain were stuck in the garage, then another two days in my enclosed deck awaiting a proper dolly my neighbor has and his help. These Bastards are HEAVY plain and simple. Self Medicating now throwing back a few cold-ones (Cone-head style)
Pretty sure these will never see sunlight ever again, I am now of the opinion every home needs at least a dumbwaiter or escalator with reverse!!!
James you mentioned the passive loading changed as much as Brians shirts. These earlier designs just don't allow for a hand to putty pinch as the later designs do with their larger slot opening, like my RM-1s allow. How did you guys adjust the putty loading without laying the speaker on its side and pulling its bottom base off ???????? The slot just don't fit a mans hand. My earlier Tower II and later the Tower II special edition with the rounded cabinet were both similar with the small slot opening.
Also James is there any benefit to throwing the bi-amp switch and running bi-wire through one amp ???
Thanks for letting me pick your thoughts/memories of this Iconic Brand of Loudspeaker, VMPS, there never will be another like it period, nobody has the balls!
Sincerely,
DW
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My hands are XXL and I don't recall them not fitting for adjusting PR mass....strange. OTOH I didn't mess with it much on that model because Brian visited once and tuned it in pretty darn well.
No idea any difference associated with bi-wiring but you'll surely try it and report to class, right?
I worked a lot of shows with Brian, using some of the world's most costly cables. For over 15 years now I continuously used Stan Warren's original recipe, quad twist 12AWG THHN 19-strand copper house wire. I love the Audience wire, which is very costly.
I have no personal history or opinion about coating the PR cone with white glue, but I'd definitely try it. As Brian later found out, after my continual prompting, the PR performs better on the side panel near the base (RM50, his last model).
I'm anxious to hear results of comparison with RM1 and 626 (betting on the former....almost impossible to overcome 2x 15s and a 12 midbass).
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Hi James and everyone else following this : The ST/R are FINALLY downstairs!!! Between the constant rain were stuck in the garage, then another two days in my enclosed deck awaiting a proper dolly my neighbor has and his help. These Bastards are HEAVY plain and simple. Self Medicating now throwing back a few cold-ones (Cone-head style)
Pretty sure these will never see sunlight ever again, I am now of the opinion every home needs at least a dumbwaiter or escalator with reverse!!!
James you mentioned the passive loading changed as much as Brians shirts. These earlier designs just don't allow for a hand to putty pinch as the later designs do with their larger slot opening, like my RM-1s allow. How did you guys adjust the putty loading without laying the speaker on its side and pulling its bottom base off ???????? The slot just don't fit a mans hand. My earlier Tower II and later the Tower II special edition with the rounded cabinet were both similar with the small slot opening.
Also James is there any benefit to throwing the bi-amp switch and running bi-wire through one amp ???
Thanks for letting me pick your thoughts/memories of this Iconic Brand of Loudspeaker, VMPS, there never will be another like it period, nobody has the balls!
Sincerely,
DW
Shear B,
Regarding the BiWire Switch: Most found years ago that moving the switch to bi-wire and simply running "jumpers" between the binding posts gave a better sound, by-passing the switch and circuitry. That is why all the later models eliminated the switch. You don't even have to biwire to hear the difference, just the jumpers will make it evident.
Regarding Vitrifying the PR: You will get a clearer and cleaner bass response with a stiffer PR, and you will simply use less putty to make up for the small mass of the glue. Brian too began vitrifying years ago on both FloorStanders and Subs when possible. His PRs used a Paper Cone (except for the RM30s) and he liked the stiffness and the sonic result.
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I honestly don't know if it matters, but Brian seemed to think the yellow carpenter's glue was best, when vitrifying a passive radiator:
http://www.audiocircle.com/index.php?topic=10390.0
Good Luck!
And I too look forward to a review, and a model comparison!
In the original post Big B said yellow carpenter's glue. So probably this is the wood glue, not the ubiquitous "Elmer's Glue-All". I think this is the product he refers to:
http://www.elmers.com/product/product_page.asp?pCode=E700 (http://www.elmers.com/product/product_page.asp?pCode=E700)
Big B will you confirm?
Wood glue does make sense since this is a paper woofer and paper is obviously a derivative of wood.
I'll head to HD later and pick some up along with a 2" paintbrush. Most of the job for me will be moving the RM/X to the ground and then particularly back upright (about the only time I wear the old hernia belt :lol:) so I'll probably remove the passive drivers completely and paint them on both sides like Big B did.
The yellow carpenter's glue is the stuff you want.
You're right, this is the wrong time for a cheap tweak like the Elmer's paintjob. Forget I said anything.
Some years ago John Bau coated the paper cones of his TC50 with Elmer's glue to stiffen them.
Unfortunately it also rendered the diaphragms noiser, negating any benefit. However, since the noise is mostly high frequency I always wondered whether Elmer's (yellow carpenter's) would stiffen woofer cones to good effect.
Since our Passive Radiators are very low mass (less than 20g) paper cones I decided to paint them (both sides) with Elmer's, let them dry, and reinstall (being careful not to let glue drip onto the spider).
The results are most efficacious. In other words, try it and be amazed. You may or may not want to remove a little putty from the PR to compensate for the residual mass of the glue solids.
If you don't care to take out the PR just paint the side of the cone facing you. You will have to unscrew the base to access the PR. Works well with all floorstanders and subwoofers we make.
Enjoy!!
A thin coat is fine, apply with a 2" brush and don't allow drips or puddles to accumulate. Allow to dry 6 hrs before playing. Lots of fun, big rewards.
Keep the glue away from the foam surrounds.
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I have the drivers back from re-foaming at Millersound and installed. Bill did a fantastic job on these, even put Dynamat-Extreme on the 15" active bass. Bill does excellent work and is who I turn to for speaker repair of any kind.
Very happy with these but not so much in my Crown K1 to run these full range as I'm forced to do at present, as I cant bi-amp like I was doing with my RM-1s. Am searching now for a more suitable power amp. The Crown does bass though, and these really kick some booty on the bottom end!
I did not Vitrify these yet either wanting more to hear them first without. The 1oz fishing weight glued worked out fantastic, flattened then glued with 3 1/2 inch on one and 4 inches of putty on the other.
All drivers up an sounding fine, just cant comment much further until a more suitable amp comes my way. Roger any suggestions on a 100-150 watt amp to do justice on these ??? Going to dig out my Stereophile issue and see what AHC was driving them with when he reviewed these, of course any suggestions always helpful.
So that's about it for now, a little late but I did come to class.
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I have the drivers back from re-foaming at Millersound and installed. Bill did a fantastic job on these, even put Dynamat-Extreme on the 15" active bass. Bill does excellent work and is who I turn to for speaker repair of any kind.
Very happy with these but not so much in my Crown K1 to run these full range as I'm forced to do at present, as I cant bi-amp like I was doing with my RM-1s. Am searching now for a more suitable power amp. The Crown does bass though, and these really kick some booty on the bottom end!
As you state, the Crown is likely great up to about 80 Hz, where I cross my system, but certainly not full range and not even for your mid-treble biamp/biwire pole circa 4-5k Hz. (This high pole + multiple tweeters explains Brian's wide dynamic range).
I did not Vitrify these yet either wanting more to hear them first without. The 1oz fishing weight glued worked out fantastic, flattened then glued with 3 1/2 inch on one and 4 inches of putty on the other.
If 1 oz fishing weights are unchanged from that era, no need to flatten...they fit fine in the 15"-12" PR cone exterior center. Brian did not, but I preferred to bend the wire fastener up about 30-40 degrees to better center the weight (I'm surprised I remember that).
It is almost certainly always better for each channel to have offset PR mass. IOW, PR mass should never match between channels and should rather always be different. The degree of difference is less critical, as long as they don't match.
The only potential application where performance might improve with symmetrical PR mass is with dramatic non-symmetrical boundaries for L and R speakers (i.e., L speaker severe corner loading, R speaker 8' feet boundary clearance).
For readers with ported speakers, the equivalent is to slightly offset the port lengths between channels.
All drivers up an sounding fine, just cant comment much further until a more suitable amp comes my way. Roger any suggestions on a 100-150 watt amp to do justice on these ??? Going to dig out my Stereophile issue and see what AHC was driving them with when he reviewed these, of course any suggestions always helpful.
So that's about it for now, a little late but I did come to class.
Any amp of that era requires full replacement of all electrolytic caps by now. Such effort makes it likely far more cost effective to shop for something newer (unless you find a used amp with proof of the service...but even then, replacement transistors likely don't exist...also, sometimes no PS caps exist with proper size and value).
Tony's preferred affordable amp in that era was the Adcom GFA-555.
Stop reading now except to read shameful plug: I charge $155 for "Build Service" (http://jamesromeyn.com/#/home-audio-gear/hypex-ncore-nc400-build-service-on-time-or-free-build) with guaranteed two-day turnaround after I receive all necessary parts from two vendors, for Hypex Ncore NC400 power amp: 200/400/600W @ 8/4/2 Ohms, rated safe to 1 Ohm (1/3rd duty cycle), 1200W SMPS, about 8 lbs, cooling vents on top, XLR input, great binding posts, draws about 8W @ idle. Stereo version total cost is just under $1500 + final destination shipping from Utah. There are decent amps for lower cost, but for this application requiring power and finesse, the closest upgrade is Bongiorno's $7500/pr Ampzilla II mono blocs, about 65 lbs each.
I have four amps in queue now, turnaround is slightly longer than the so-called guaranteed two days.
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If your looking for a mid priced 5 channel amp for biamping. There are two cinenova Grande 5 amps on eBay now. I use them to run my 40s with very good results.
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DW -
As you asked for Bi-Amping, I used my Carver Receiver 2000 (200 watts/channel) for the highs and the Carver TFM-35 (250 watts/channel) for the mids/bass for 23 years with excellent results for the speakers I sold you. Any reasonably power amplifier would also provide excellent results due to the simplicity of Brian’s OX design not affording a difficult load to drive. There is plenty of Carver used equipment on E-Bay and AudiogoN and you would able to join a new Carver blog at http://www.carveraudio.com/phpBB3/index.php. Roger
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I highly recommend any Sunfire power amp as long as the price reflects its age relative to cost to replace electrolytic caps for shelf life (estimate 15-20 years). Any Carver branded piece is way too old unless accompanied by documentation proving new caps or price reflects cost for new caps, if available.
The problem with Sunfire power amps is that their cost continuously increased over time. Last I checked early '12, clean moderate age Sunfire amps regularly sell for only a few hundred less than my brand new $1500 Hypex Ncore NC400 stereo amp build.
Yes, older Sunfire amps cost under $1k. Now we're back to gambling with cap shelf life.
Cap symptom is 60 Hz hum. Ask about 60 Hz hum level with no input to the amp. The higher the speaker sensitivity the louder the hum.
I can't remember all my notes, but one or two vintages have service weakness (PS IIRC) other than normal shelf life for the caps.
Shelf life is longer for so-called "wet" caps (power applied), shorter for "dry" caps (no power applied). For this reason, when inquiring about any component, it's always good to innocently ask how much of it's life was spent in use (powered up) vs. not in use (powered down).
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James, I just discovered one of the top Piezo tweeters is out, do you recall the type or maker to pick up a replacement ??? Probably would just replace both.
Still enjoying these BBs (Big Bastards) very much, even though my power amp option at present sucks. So do you think the Hypex Class D amps would sound great on these ST/R ??? Keeping my options open. Thanks for the "Shameless Link" a interesting read.
Thanks, DW
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Wow, kind of shocked the piezo blew. They are generally indestructible in normal use (Brian used to say you could plug them into a wall outlet, which I can't confirm and don't advise). Maybe shelf life intrudes? Don't know. Look around, they are generic and likely still available. Try Apex Jr. in Texas first for lowest cost. If necessary post here in speaker box circle or at DIYaudio.com. Somebody's got them. Decades ago they were less than $1. Forward comments Re. current price to Ben Bernanke. Tell him I said, "Hi!"
Any VMPS, especially the older series with active 15" like yours, is ideally suited for Hypex Ncore NC400. I and most who audition NC400 believe it is the lowest possible cost for the combined level of blissful refinement and pure brute power from below to above audibility.
As mentioned, the next known step up is the late Bongiorno's $7500/pr SSI Ampzilla II mono blocs (positively avoid Series I IMO). I might also prefer the stereo Son of Ampzilla I or II, but new Series II is about $4k MSRP. Each mono or stereo is about 60 lbs and burns a ton more current than NC400. For context: last shipment was two NC400 to MI, about $45, $2200 insured value. Stereo or mono Ampzilla estimate $150ea with replacement insurance.
I also love the Aesthetix amp line and of course Dave's ModWright amps sounded totally righteous a couple years ago at CES.
Short version: if you can stretch to $1500 the Hypex stereo NC400 is king for this application. I'll post images at my site for the stereo amp by Friday. It's about 10 lbs.
Remember with the 3.5k Hz biwire/biamp split, biamp requires identical amps only. The split range is so critical I'd not even consider identical amp architecture of different power, i.e. same maker/same design, 200W bass/mid, 100W on treble. 3.5 kHz is in the human ear's range of maximum sensitivity to phase and timing errors. In fact I presume single amp of adequate power might be audibly better than many identical biamp applications.
Again, my $1500 Hypex Ncore NC400 stereo build is 200/400/600W @ 8/4/2 Ohms, rated safe down to 1 Ohm (1/3rd duty cycle).
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DW -
As you asked for Bi-Amping, I used my Carver Receiver 2000 (200 watts/channel) for the highs and the Carver TFM-35 (250 watts/channel) for the mids/bass for 23 years with excellent results for the speakers I sold you. Any reasonably power amplifier would also provide excellent results due to the simplicity of Brian’s OX design not affording a difficult load to drive. There is plenty of Carver used equipment on E-Bay and AudiogoN and you would able to join a new Carver blog at http://www.carveraudio.com/phpBB3/index.php. Roger
With all due respect, there's more to a speaker's current needs than xo simplicity. All or most of Brian's line including these older series, the more current and voltage, generally the better. The series QSO xo (QSO in this model wires bass and mids in quasi-series) is difficult enough so that Brian, in visit to Ed Long with me present (discussing the orginal SOTA speaker SOTA had contracted Brian to design), mis-sketched the QSO schematic. QSO is strangely simple yet deceptively strange. Only other known devotees are Remier and of course Bud Fried. Eventually even Brian dropped it when he switched to planar mids.
Re. the original SOTA speaker, cabinets were either tossed or stored, or? Unfortunately the cabinet builder who will remain un-named, undersized the cabinets about 1/2 Brian's spec. That system otherwise had superb mini monitor potential, well timed just after Wilson's WATT series I arrived. I'm one of a tiny number of person who ever heard the prototypes. Never saw production, too bad. Awesome cabinet design, sloped front, flush drivers, all corners huge 1+ inch radius, laminated panels, down-firing slotted 8" passive, Brian's dimpled poly-carbon 8in, Focal 1" T120 inverted dome fiberglass (not Wilson's grotesque sounding Kevlar dome, ugh!), QSO xo, etc.
The deficit in internal cabinet volume was related to the extreme oversize panel thickness, unheard of in that era,and the sloped baffle. Estimate about 1.25+" inch panels on a (specified) 1cf speaker. Builder's prototype was only about .5cf IV.
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DW –
Sorry to hear your piezo stopped working. It is possible that a lead came off in transfer to your house. If not, new inexpensive examples of replacement speakers that will fit can be had at parts-express @ http://www.partsexpress.com/term/piezos?srch=PIEZOS. Hope this helps.
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Congrats on some really nice ST/R's! You got a super deal, nice folks who let them go, no doubt about that!
That piezo should be easy enough to source. The problem that you may have is that the cabs interior (on mine) are covered in, what appears to be a spray insulation of some type. I'm sure James could comment on what was used. If yours are similar, you'll have to cut/scrape that out in order to replace it. Which would be easier said than done, considering you'll have to access it from the 12" or from the bottom. I wish you luck!
This post has me wanting to pull mine out of storage. I got mine a few years back, refurbed them cosmetically and re-foamed the 12's and 15s, vitrified the passives, but I just could never get them dialed in correctly, I had issues with one of the 15s. Then kids came, new house, more work and they've stayed in storage since I moved.
Something was amiss with them, never got the bass I was expecting and never had the time to devote to snooping out the issue.
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Hey Roger, Its quite possible it did, have not opened up to view the underside yet. Sure is"nt coming out the top, I"ve tried that. Also finding this Piezo is so far turned up nothing, sent Apex Jr. a picture found online, per James. When pulled-up online its in a foreign language though. Hopefully Steve at Apex Jr. can find a match. Glad to report the 12" Bass Coupler is still intact, has not turned to dust ...... yet.
Roger I am enjoying these very much, just running my Crown K1 on them full range does them no justice at all except the bottom end of course! Looking into Class D amplification at present.
DW
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To Venkman,
Bust them ST/R speakers out of storage man!!! Ha-Ha. As James has stated in this tread, Brian used 1oz fishing weight, glued to the passive. Then about 4" of putty. I did the same with pretty good results, my weights were (line through) which I flattened round. If your passives have tons of putty on them you really need to do this for correct loading. At the least a great starting point. I will further dial them in once I change my Crown out. Pretty darn good now thou.
DW
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To Shear Bliss and James,
My ST/R passives are a few years old, are vitrified and came with (per Brian) a lead slug in the center with a small amount of putty on top of the slug. The putty is a disk about the size of a half-dollar or so. The talk about adding a 1 oz fishing weight and 4" of putty, with what I now have do my passives need the added weight and putty before tuning? I have been under the impression the passives were shipped overdamped and the idea was to remove putty bit by bit until it gets dialed in. I tried tuning but it was difficult because as mentioned every removal (or addition) of putty required putting the cabinet on its back and unscrewing the base, which is a pain and slows down the process. I really could not hear much difference with the limited amount of times I tried.
To Venkman,
I concur with Shear Bliss. Get those ST/R's out of storage and start enjoying them!
Thanks,
Ed
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To Shear Bliss and James,
My ST/R passives are a few years old, are vitrified and came with (per Brian) a lead slug in the center with a small amount of putty on top of the slug. The putty is a disk about the size of a half-dollar or so. The talk about adding a 1 oz fishing weight and 4" of putty, with what I now have do my passives need the added weight and putty before tuning? I have been under the impression the passives were shipped overdamped and the idea was to remove putty bit by bit until it gets dialed in. I tried tuning but it was difficult because as mentioned every removal (or addition) of putty required putting the cabinet on its back and unscrewing the base, which is a pain and slows down the process. I really could not hear much difference with the limited amount of times I tried.
To Venkman,
I concur with Shear Bliss. Get those ST/R's out of storage and start enjoying them!
Thanks,
Ed
Ed,
From your information above it seems like your passives are properly weighted.
I owned ST/R and am still a bit puzzled that the slot is too narrow to fit one's hand to alter the PR mass. I don't remember this being an issue. OTOH, Brian visited my place and by the time he left they sounded so good that I never had reason to alter them.
Later sold them to Paul Chavez, Assistant Director, In The Heat Of The Night TV series starring Carrol O'Connor.
The PR mass is quite critical. From my current knowledge, unknown at the time, I'm convinced the advantage of tuning the PR mass is to tune around the modal effects in the bass range.
One of many suggestions I made to Brian that finally made their way into production (unfortunately not till his last model, the RM50) was the side firing PR. Brian wrongly placed RM50 PRs on symmetrical mirror image panels, L vs. R ch. IOW, users could fire the PR's either both in or both out. I say wrong because below the Schroeder Frequency, the more chaos and less symmetry the better.
The other consideration is PR radiating surface area. DB Keele's and early PR design criteria specified PR radiating area about 2x active driver radiating area. In this case instead of PA (passive area) = 2AR (active area) we have only about .7AR (15PA for 15 active + 10 active. The 10 has moderate value series resistor, minimizing its effectiveness, but we're still a long way from the classic PR spec.
I bet two 15s would be ideal and an audible upgrade. I'm sure no one would do it, but I'd strongly consider cutting a hole on the lower side panel for a second 15" PR. On both speakers fire the PR either L or R (does not matter, the goal is increased chaos in the bass range, which diminishes modal effects).
It would take time and effort to settle on a fixed PR mass for the down-firing PR. Then it's easy to adjust mass on the side firing PR. I'd probably start with no mass on either PR, then add mass to the side firing PR. If it appears that more than about 1oz of weight is required on the side firing 15, swap the 15s then continue adding mass to the new side firing PR which starts with no weight.
Listen to Sandy Gross' GolenEar line. Every model has two PRs and in every case PR area is about 2x the active driver area or more. Sandy could have saved real money with only one PR. Sandy only used two PR for the performance advantage. The less is PR area the greater is excursion. Shine a light on the PR or feel it with your finger during loud bass passage, and check the excursion of the PR cone.
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To ST86
Finally somebody who gets my plight!!! Early versions have too narrow of a slot to adjust mass without laying down. Seriously been thinking about adding three 2" slats on both sub bases, glued an screwed in place. Just buy longer screws and paint.
Not cutting my boxes up but willing to modify them sub bases. Also trying to source the top firing Piezo Tweeters here in the US has gone nowhere. Did find a match online but in a foreign language and could go no further, see pic.
(http://www.audiocircle.com/image.php?id=87295)
DW
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Yes, I have thought about making a base with a larger slot but figured altering the dimensions of the slot would affect how the passive works. I suppose I could just make a taller base and listen to find out. So many projects, so little time....
Still have the build instructions and schematic for my ST/R, will check if there is any model info about the particular piezo in mine. Been a long time but the one in the picture doesn't look familiar. I seem to remember Brian saying the piezo in the Supertowers was discontinued. Mine are attached to the cabinet with super glue, I would probably destroy them if I was to try removing them to replace them. It is unusual for a piezo to go bad. Did you check to make sure the problem isn't related to connections or wiring? The L-pad in one of the rear terminal cups connects to the piezo, that would be a good place to start.
Ed
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I agree, piezo's generally don't fail. The piezo is parallel with the (non) ribbon (it's a planar) tweeter, so if the L-pad is at fault the planar is also dead.
The piezo is parallel with the planar.
Description of top piezo mechanical coupling: A short (about 1-2") long black PVC pipe is loose. The cabinet shop wraps speaker cloth around one open end, then stuffs the PVC into the hole in the cabinet from the inside. It's a simple press fit, no adhesive. This is the state when we received the cabinets oh so many years ago.
I epoxy passives, clean up, or assemble required drivers while Brian and I banter about the state of the audio universe and other subjects while Brian solders a crossover together. When the xo is done he walks over and I start stuffing the box with xo and drivers.
When we get to the piezo, we squirt considerable hot melt around the coupling surface (face near the outer circumference) of the piezo, I say bad words while hot melt dissolves considerable skin on my fingers, hands, and forearm, and while the glue is hot I simply push the piezo onto the edge of the PVC inside the cabinet.
To check or replace the piezo, simply get like-diameter piece of PVC. You could use a piece of soft wood, but this will more likely crease the speaker cloth so I don't recommend that.
Cut a round piece of cardboard (or similar) same diameter as the PVC to save the piezo speaker cloth. Place the cardboard between the piezo spkr cloth and the like diameter loose PVC piece. Lightly hammer the top end of the loose PVC with a rubber mallet. Eventually the PVC/piezo piece falls into the cabinet cavity. You might want to prevent the piezo from stressing the piezo leads. Remember, it's a simple press fit, but some are tighter than others depending on hole diameter, wood swell, plus PVC is not exactly a precision piece of plastic.
Unsolder the leads from the piezo, connect amp to treble posts only, turn up planar/piezo L-pad to max, turn dome L-pads to zero, connect a known working tweeter to the piezo leads, and you should hear music from the test tweeter and the planar too.
Listen carefully with the tweeter stuck in your ear because this xo is very high, not much energy, around 10kHz. If it works, but the piezo does not, you have the first known blown piezo except for one customer whose entire xo flamed in most dramatic fashion (a VMPS museum piece if such museum existed). We had a few rare open piezo but this was known from the start, not like they worked then stopped working.
The planar and piezo share exact same xo and the planar and piezo are wired in parallel. Even if the piezo is blown the planar can still work (unless it's blown too).
If the piezo is blown, melt the glue with a heat gun and pry away the piezo and watch out the glue melts skin like nothing. Take an image of the piezo and place wanted ads. There might be a production number, I sure can't remember. Somebody's got a couple of those stupid things in their basement or closet. To test them requires an 8 ohm parallel resistor. They won't work without it. In the ST/R case the resistor is the planar tweeter in series (error earlier where I typed parallel, the planar and piezo are in series).
Actually, now that I realize the series connection, if the piezo does not work, the planar can not work, regardless the cause. One fails, both fail.
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Checked my build instructions. The parts list only says "one piezo supertweeter" (the list is per speaker). No manufacturer or part number listed.
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ALL SPEAKERS ON MY ST/R ARE UP AND RUNNING!!! The problem was centered on my jumper cables, I had made these jumpers a while back for my RM-1s out of extra Tara Labs speaker cables. The negative spade was sheared off making no top to bottom contact, a real easy fix.
Thanks everyone for all your help, suggestions on the piezo and JVC tweeter. I was getting ready to check the L-pad when I discovered the problem. James was correct, both tweeters were down but sprang to life, switch down, single wired.
Thanks again,
DW
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Cool!
I doubt anyone saw my edits, at least I hope not. Several times I went back and forth, each time convinced the planar and piezo were wired either series or parallel. Finally settled on the latter. Series would require an 8 Ohm parallel resistor on the piezo, unnecessary in parallel wiring.
A similar vintage model, the Tower II, came standard with two piezo supertweeters, one firing forward the other firing up same as ST/R (the only two VMPS with up-firing drivers).
Piezo has virtually infinite series resistance, which I suppose is why B said you could plug them into the wall outlet (don't try this). The infinite series resistance caused standard TII with dual piezo to need a parallel 8 Ohm resistor, otherwise no sound. Some TII owners (about half or more) upgraded to planar front firing supertweeter (replaced piezo in this position...we had to cut out the baffle). On such models the planar driver's series resistance replaced the 8 Ohm resistor. This supertweeter circuit (planar + piezo) is identical in both TII/R and ST/R, the only change between slightly different series capacitor values (same .2mH parallel choke in every planar-supertweeter equipped speaker B ever built of which I'm aware).
All supertweeter poles are 2nd order electrical.
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Ok mr. Bliss. How about some current listening impressions of the rebuilt Tower/R.
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This is a follow up on my ST/R speakers bought last year. These are in excellent condition only needing new foam surrounds on the 15" and 12" woofers. Millersounds Bill LeGall did the work, thanks Bill. I had started a follow up after the 15" woofers settled in then the 12" bass couplers went, so back to Bill they went.
I did modify the passive bass slot opening, adding 1 1/2" of height to it. Plus installing casters for easy movement, no more laying these down to make a putty adjustment is just ideal to me. I did vitrify the passives with yellow glue on the outer side only. I have the passives loaded per James recollection of Brian using 1 oz of fishing weight glued as a starting point tweak. Mine was hollow line thru type so was easy to flatten into a quarters size. I find using 6 to 6 1/2" of putty works best in my room.
Comparing these ST/R to my RM-1s not really fair, maybe the RM-2 a better fight! The RM-1 places better in my room but cant match the bass output or the midrange warmth I prefer in the ST/R ..... again apples and oranges. I do like the JVC clone up top over the spiral tweeter on the RMs, more reach and presence there. These portray a much more laid back manner through the midrange that just sucks you into the recording, in that sense James may be correct in that the Neo panels need help around 1Khz.
I chucked my Crown K1 for a Digital Amplifier Co. Cherry Ultra and there is no comparison, it is a sweetheart on the ST/R while not breaking a sweat. Works very well with my Classe 50 preamp thou I long to go back to a tube pre.
All this for a outlay of $200.00 ...... minus repairs! It just does"nt get any better than this.
Doug
(http://www.audiocircle.com/image.php?id=99295)
(http://www.audiocircle.com/image.php?id=99296)
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Exactly what I would have predicted. No replacement for displacement. I'd not mind owning that pair of speaker at all! The casters look cool on that model.
I gotta leave for an appt. Remind me and later I'll post brief story of that model speaker causing neighbor's pictures to fall off his wall.
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Hi Doug,
I am very interested in your opinion of the effects of the extra 1 1/2" of slot opening on the bass. I have foregone the putty pinching because of the need to lay the ST/R down every time I want to change the amount of putty. Using the default amount on the passives I bought from Brian a few years ago.
Just occured to me if the extra 1 1/2" has an adverse effect I suppose one could use the extra space to reach the putty, then add sheets of MDF or plywood to the slot to reduce it to the original height.
Anyway, even with the default amount the bass is quite impressive. Would be nice to conveniently dial it in though.
Thanks,
Ed
Edit: Here's another question. How do the castors affect speaker-to-floor coupling/decoupling?
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As I posted prior, over the years Brian employed some of my suggestions. Some more quickly (Scan Speak D2900) than others.
I made two matched custom woofer enclosures each comprising Brian's active poly (pale blue) 15" loaded by paper 15" PR (same as ST/R) with Brian's 4197 carbon loaded poly active 10" in its own sealed sub-enclosure.
The two active drivers fired forward, 10" above the 15". The PR mounted vertical on one side panel near the base, no slot, and IMO performed better than Brian's invention (slot-loaded down-firing) employed continuously from his first floor-standing Tower. Over the years I prodded Brian try this PR loading. No dice till his very last and best ever speaker, the RM50.
Brian eventually preferred my PR loading suggestion after he tried it. Apparently, efficiency of coupling to the room via open side firing outweighs the slot's capacity to filter alleged HF noise from the PR. PR mass is many multiples greater than air in a port. Gravity must minimize symmetry in the horizontal PR's in/out stroke (down/out minimum resistance, upward back into the cabinet maximum resistance) vs. any vertical loading (symmetrical stroke in/out), especially PR of such high mass. Further, I suspect the pedestal in close proximity to the PR causes PR output to reflect back into the cone, further minimizing its efficiency and disturbing its phase.
ST/R owners could cut their cabinet to move the PR to the side, but this obviously results in permanent cosmetic alteration. Returning the cabinet to OEM requires a big piece of matching veneer. For cosmetic PR cover on the RM50, Brian chose to make the RM50 cabinet panel thick enough (where the PR mounted) to inset the PR to allow approximately 3/4" thick cloth covered grill frame to press fit over the PR. When installed, the grill and side panel were flush.
If you cut, do NOT, I repeat, do NOT cut L/R holes to make a mirror image speaker pair, as Brian did in the RM50 (IOW, both L/R PR's fire either in or out). You want the PR in both L and R speakers to fire either L or R (direction does not matter as long as they both fire the same direction). The less is L/R bass symmetry the less excited are bass modes, the smoother is bass FR, and less are bass timing errors caused by modes. (Shameless plug: Above summarizes the philosophy of state of the art bass reproduction systems such as THIS (http://jamesromeyn.com/#/home-audio-gear/dsa-1-0-distributed-subwoofer-array-5-pieces-4k-usd/), providing unheard of 6 dB FR window and virtually perfect time response in the bass range with no EQ, no acoustic treatment, and even in rooms with awful bass modes.)
To maximize non-symmetry, mount one PR as close to the floor as possible, mount the other PR as close to the top panel as possible (vertical non-symmetry). Vertical non-symmetry provides less non-symmetry vs. horizontal non-symmetry, hence the latter is more beneficial. Make sure the PR mounted high clears everything inside the cabinet (drivers, braces, etc.)
PS: Suppose all other items identical except one ST/R OEM slot height, the other has +1.5" slot height. I predict no one could reliably identify audible difference. I further bet $100 if one could reliably hear difference they'd prefer the latter, which would emit more PR energy and have less PR energy reflected back into the PR from the pedestal.
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Hi ST86
When I decided to open the passive slot I was somewhat concerned it might screw things up a little, but not being able to make putty adjustments on the fly over ruled any other concerns. These sound just as good now as they did before I opened the slot height. I can now change bass tone via putty in mere seconds without moving my ST/R.
Read below for James take on opening the passive slot if you still have any concerns .....
At 150 lbs each I had no problem with going with casters. I can roll these BBs ...... (Big Bastards) out of the room and have my RM-1s running in minuets if I wanted to now!
Always refer to James, he knows the early VMPS speakers better than anyone out there!
Doug
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The size of the slot, and the size of the opening, provide a resistance to the Passive radiator, that Brian felt worked well.
If the volume and size of the opening are increased that resistance drops.
To compensate, simply "add" putty which will provide additional mechanical resistance to the PR, then fine tune from there.
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Doug, John,
Thanks. This is good news. I will put "make extended height tray for Supertower/R" on my list of projects. Tuning the pasives will be much easier with the extra room.
Any verdict on castors effects on speaker-to-floor coupling? I remember Brian was against using spikes. My floor is carpet over cement (Basement Home Theater Man Cave). I don't have the castors (great idea by the way), the cabinets do rock front-to-back rather easily.
Cheers,
Ed
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I'd like a ST/R owner to lay one speaker on its side, firing forward, PR away from adjacent wall. Listen to only that one speaker, program with deep bass, first with pedestal attached, then remove the pedestal and re-listen. Curious what might be the deep bass difference if any.
I don't think Brian realized it at the time (if he did he never said so), but I'm virtually positive most or all the perceived difference in tuning the PR is simply its effect relative to bass modes. Even differences between amplifier output impedance specs interact with modal effects.
Early Wilson WATT included two ports lengths for different amplifier output impedance specs (SS/tube).
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Ed,
Brian's idea on beards and no spikes was based on the propagation of the 360 degree pressures of bass waves.
They travel in a 360 spherical radiation, contained only by solid boundaries.
as the bass wave leaves the slot, it then radiates in that pattern. it will travel down the solid surface of the slot to the solid boundary of the floor.
The break in the boundary between the bottom of the slot and the floor allows some of that pressure to go into that opening, and "in theory" would slightly reduce the pressure that would come to you.
I say "in theory" because I tend to think that you wouldn't notice too much difference, or that the advantages of mobility might outweigh them.
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Ed,
Brian's idea on beards and no spikes was based on the propagation of the 360 degree pressures of bass waves.
They travel in a 360 spherical radiation, contained only by solid boundaries.
as the bass wave leaves the slot, it then radiates in that pattern. it will travel down the solid surface of the slot to the solid boundary of the floor.
The break in the boundary between the bottom of the slot and the floor allows some of that pressure to go into that opening, and "in theory" would slightly reduce the pressure that would come to you.
I say "in theory" because I tend to think that you wouldn't notice too much difference, or that the advantages of mobility might outweigh them.
I think that opening is audible. I'd plug the opening with any acoustically opaque material, even a piece of thick cardboard should work. Just cut it to fit the opening and lay it against the vertical front of the pedestal, resting on the floor. You are just making a very short beard.
Again, though, I'm not sure. Brian changed to the vertical open PR after I prodded him to do it, and I think it works better than the slot, but I'm not sure why. Brian agreed with me after he built the RM50.
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Interesting stuff. Thanks!
Ed
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James/John,
Not laying my ST/R down no more ...... well worth the pedestal adjustment. I'm surprised the slot opening has"nt been more of a issue with owners over the years. The RM - 1 and 2s allow this extra room to make easy putty adjustments, I'm finally at peace. To me adding the casters was just a no-brainer for sure! Adding a little extra putty than the norm is a small price to pay to make the bottom end sound like it did prior to this mod.
I should have mentioned John also when referring to James knowledge of things VMPS, my bad, sorry John.
The putty loading still works its charm ... I pulled all putty off leaving the 1 oz lead in place and listened. As expected the bass thinned out with leaner bass impact, adding 8" of putty gave a thicker woolier muddier presentation. (In MY ROOM) 20 x 13 ..... 6-6 1/2" works very nice.
DW
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The room's dimensions are one parameter in a long list of almost infinite relationships affecting perceived bass quality. Other parameters are location of two speakers, listener location, boundary surface rigidity, etc. Change one item and the entire formula (and perceived bass quality) changes.
Note how perceived bass quality changes as you walk slowly around the room. As bad as are peaks and dips (15 dB windows are common), much worse is the negative effect on bass timing, as wrong bass notes ("synthesized" by the room, a product of bass waves interacting with room dimensions) continue playing even after a new bass note appears. This is, to me, the unforgivable error of bass mode effects on the listening experience.
A speaker engineer who deciphers and reviews loudspeaker patents for a trade publication agreed with me that bass mode effects comprise THD over 100%, just to provide a context of the scale and show how egregious are the errors involved.
After listening for the past several years with almost no bass mode effects, I'd quit the hobby if I had to go back.
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For those interested, the "putty" mass damping is to adjust the MASS of the Passive Radiator and its response to the internal cabinet pressures.
A greater mass slows response, and a lighter mass allows for a faster response.
If it is lighter then the response frequency will rise, if it is heavier the response is slightly delayed and the frequency is lower.
The pinching or adding is a process that "synchronizes" the PR with the active woofers so they respond at a lower frequency, but in a phase relationship that enhances the lower bass. When the mass is "just right" that synchronization will produce the lowest distortion and the system (all the woofers and the PR) works much like a single driver.
If the mass is too light, the system will sound "thin" and not very deep or rich. If the mass is too great then the bass will get flabby, wooly, sluggish, and rubbery.
When perfect the drivers are also in a synchronized phase relationship.
There you have the physics of Brian's PR system, and why it works to offer the cleanest, lowest distortion, harmonically accurate bass of most any multiple driver bass system.
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Comparing phase relationships perceived from any box speaker vs. phase/modal effects perceived from room modes, the latter are about 100-200x more audible. When persons describe bass response in a room, their perception depends many times more on infinitely variable relationships secondary in nature to the box than it does on the box and its contents. The reason is that bass wavelengths exceed the dimension of any two walls in a domestic sound room. Bass waves must "bounce" between two walls before they are audible. By definition, this means the walls make a permanent indelible "finger print" prior to anyone perceiving the bass note. You can't undo this finger print no matter how much you spend on EQ, acoustic treatment, and no matter how many hours anyone spends fiddling with PR mass. It's a permanent indelible artifact. This is why I said the modal effect is much more highly perceived than any gobbledygook Brian or anyone else promoted. Speaker tuning can work for or against any one modal effect, but it can't undo any of them.
Brian talked a good game and built some good speakers. The net effect of changing PR damping is identical to simply altering port volume. This is not to say PR and port loading are identical, but rather saying the net effect of altering PR mass is the same as altering port volume, no more, no less.
Again: modal effects present over 100% THD in the bass range. Considering this context, one might recommend caution regarding distortion claims for certain loudspeakers. Persons have a hard time understanding that THD is the least of their problems regarding bass. Modes synthesize their own bass notes directly unrelated in pitch to the original bass notes, and these notes resonate long after the original note stops. Imagine two bass players, one playing with his bass mis-tuned 1/4 tone low or high, plus he plays out of time. This is so much more audible than THD it can hardly be described.
The problem is persons who have not listened to a room with modal effects solved don't have a reference. They are not necessarily great authorities on the subject, having no experience with the issues described (modal effects) solved.