[7x57]

 I have spent my spare time in the last couple of days looking for replacement woofers for my RM-1 speakers. The best deal seems to be the HiVi M8a and M8N available at Parts Express, if you prefer to spend less than $50 each woofer. Both have aluminum-magnesium cones that are gold anodized. HiVi is the owner of Swans Speakers and they are used in some Swans models.

Many 8" speakers actually measure 9" (225mm) in outside diameter, but you will have trouble with anything over 8.75" diameter in the RM-1 unless you want to do some modifications. Madisound also carries HiVi in the USA. The Dayton Audio Reference 8" woofer at Parts Express also looks nice if you want to spend a bit more than HiVi 8". If you are into something like SEAS Excel or ScanSpeak Revelator or Accuton ceramic cone at prices from $200 to $1000 for each driver, Madisound has those as well.

Just one Erse 5.6mH inductor cost $25 at Parts Express, so I figure Brian paid as much for that woofer inductor in my RM-1 as he paid for the cheap standard 8" woofer with small magnet and graphite filled polycone. Almost every reviewer at P-E praised the HiVi woofers and said they punched far beyond their price point. The low crossover point in the RM-1 should not excite the metal cone as it would tend to do in a typical 2-way speaker that crosses over around 2 kHz to 3 kHz.

I can't see the point in going with high cost SEAS or ScanSpeak woofers with no more Neopanels available for the RM-1. I looked up the cost of Infinity Emit-R tweeters and for pairs they were $199 NOS or $165 in matched pairs in used working shape. So when the tweeters go, you would be better off replacing with something more modern at a lower price. As good as the Infinity Emit-R was in its day, when I bought my RM-1 speakers in 2001, it would be considered the end of the Emit-R reign as a standout mid-priced tweeter.

Those who are Infinity Kappa buffs say the Emit-R has a high failure rate in extended hard use. One of mine failed, but I got a new diaphragm from Brian in 2012 at a fraction of those used Emit-R tweeter prices on eBay. Some people repair the Emit tweeters with Loctite rear heated window repair paint that restores the conductive trace. I'll just move on to a more modern tweeter when the time comes for a repair. I would probably go with a HiVi RT1C-A tweeter at this time, for about $45 delivered. The specs seem to indicate it would match well with the VMPS tweeter crossover and I like the wide horizontal dispersion and controlled vertical dispersion. I believe this was the goal of the CDWG that Brian used on later VMPS models. The Emit-R tweeter is obsolete unless replacing a single tweeter in a pair of speakers with multiple tweeters. A the HiVi tweeter price, I might order a couple just to try them someday. I could probably pay for them by selling my Emit-R tweeters to somebody who wanted exact replacements.

Also beware of those graphite coned midwoofers that have an Xmax of 1.5mm or so. They do not go low in bass and were designed to be used with a subwoofer. You need an Xmax of at least 5mm for the RM-1 woofer unless you plan of crossing over to a subwoofer to prevent large woofer excursion. I spotted several 8" woofers with exotic cones and huge magnets and short Xmax that are often used as widerange drivers. Think Lowther. Think high efficiency. Their high Fs is another giveaway as to their intended purpose. Would work in an amp for acoustic guitar, not an RM-1.

I looked at the suggested replacement drivers on this forum, but  feel I can do better for my purposes with the HiVi M8N for less money. One important consideration is the hole diameter, as most 8" woofers will requirement enlargement of the mounting holes, and I do not have the tooling to do it properly. It is mainly cast frame drivers that cause this problem. Cork damping material can help reduce steel basket ringing, and if you go to the new PHY-HP website, you will see that they use a cork damping ring on their new ferrite magnet fullrange driver that has a steel basket frame. Cork sheets and contact cement will get you much the same effect as cast woofer baskets. The HiVi M8N has sufficient mounting holes to reduce basket deformation and is actually quite a bit better in that regard than the original standard 4-hole VMPS woofers.

I'm glad to see that PHY-HP was saved from extinction as they stood apart in the loudspeaker driver world. One would hope VMPS will go on as well someday. However, PHY-HP was a driver manufacturer that several manufacturers depended on for existence as it was the sole source of drivers for their designs. Srajan Ebaen of 6Moons said that when he was given a demonstration by Bernard Salabert in his listening room, a single pair of the PHY-HP drivers was shaking the concrete block floor of the LARGE listening room at 30 Hz, direct radiation, no back loaded horn like Lowther fullrange drivers. Bernard Salabert should be credited for saving "old technology" that worked very well from untimely extinction, as well as bringing to attention the bad effects of MDI interference caused by synthetic materials.

The synthetic material interactions is no small matter. For instance, in clothing, research has shown that simply changing from synthetic underwear to natural silk, wool or cotton underwear will reduce some forms of cancer in women by 1/6 compared to synthetics loaded with hormone disrupters. I no longer wear Thermax long johns and have converted to 100% Merino wool. It is NOT a subtle difference (besides the price tag), and my sister bought the same exact LL Bean  Merino wool underwear and said she will NEVER go back to Patagonia synthetic.

If a person doubts that MDI interference is of no importance due to its extreme HF content, consider that some people are now wearing silk skullcaps while sleeping at night as it reduces microwave cellphone noise and they sleep better. There is also the current surge in Orgone Generators to put in bedrooms, etc., where much time is spent. A German scientist proved that the 2 GHz range of cellphone frequency was extremely injurious to human health. It bears to good reason that Bernard Salabert used silk insulated wiring in his PHY-HP drivers. Microwave radiation removes humans from the 7.83 Hz Schumann Cavity Resonance of the Earth. Many people preach the positive aspects of "grounding" to the Earth on a regular basis. The Great Pyramid at Giza is tuned to the Schumann Cavity Resonance, and it is no coincidence, as pyramids were originally invented as power sources and not burial places for dead pharoahs, and for attracting lightning and Earth energy and converting it to a useful purpose, such as ball lightning. The exact shape of the Great Pyramid is exactly the same as a natural quartz crystal, which are the active element in orgone generators....no mere coincidence.

Just to say that Bernard Salabert was a true loudspeaker driver genius. I have lusted after a pair of his 15" coaxial drivers for some time now. To be driven by an OTL vacuum tube amp of modest power. Brian Cheney did some of the best crtossover design, but any passive crossover sucks in comparison to no passover as far as transparency goes. He chose the Neopanel to get the upper and lower crossover frequencies as far away from the midrange heart of music as possible.

[Stimpy]

While I'm not 100% sure on this, I 'think' Brian used these MCM woofers in the RM-1:

These use a cast basket, and had a 6 hole mounting pattern.

http://www.mcmelectronics.com/product/55-3550

These used a stamped basket, and had a 5 hole mounting pattern. 
 
http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-1551-/55-1551

I've seen pictures of RM-1's using both style of woofers.  These have been used stock, and also modified, with the dust cap removed and a phase plug added.

Also, I've seen pictures of RM-1's that used woofers based on the Infinity RS-625 speaker:

http://www.ebay.com/sch/i.html?_odkw=infinity+626&_sop=10&_osacat=293&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xinfinity+625&_nkw=infinity+625&_sacat=293

Maybe email or call Infinity, to see if they still have these woofers in stock

parts@harman.com

877-871-6755

Good Luck!

[Stimpy]

After rereading your original post, I believe that I somewhat misinterpreted your meaning.  I originally thought that you needed new woofers, as in replacements.  Now, I think that you're looking to upgrade to something better, than your original graphite woofers?!?

As such, the two MCM woofers, that I referenced, were an upgrade woofer that Brian sold.  There's even a RM-1 pictured, in my "For Sale" thread, showing RM-1's with the 6 holed MCM woofers:



As to other alternate woofers and tweeters, that's going to be difficult to determent.  With no knowledge of the RM-1 crossover (1st order in phase?, like most VMPS models), it's hard to suggest replacements.  But, I like your HiVi suggestions, due to their 'symmetrically driven motor structure' design.   Also, I guess you can't go wrong with either the Beston and Aurum Cantus tweeters, since Brian used those.  Maybe even the BG Neo 3?  It would probably work, since Brian used such a high crossover high pass frequency, for his tweeters.

While I'm not 100% sure on this, I 'think' Brian used these MCM woofers in the RM-1:

These use a cast basket, and had a 6 hole mounting pattern.

http://www.mcmelectronics.com/product/55-3550

These used a stamped basket, and had a 5 hole mounting pattern. 
 
http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-1551-/55-1551

I've seen pictures of RM-1's using both style of woofers.  These have been used stock, and also modified, with the dust cap removed and a phase plug added.

Also, I've seen pictures of RM-1's that used woofers based on the Infinity RS-625 speaker:

http://www.ebay.com/sch/i.html?_odkw=infinity+626&_sop=10&_osacat=293&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xinfinity+625&_nkw=infinity+625&_sacat=293

Maybe email or call Infinity, to see if they still have these woofers in stock

parts@harman.com

877-871-6755

Good Luck!

[John Casler]

 I looked up the cost of Infinity Emit-R tweeters and for pairs they were $199 NOS or $165 in matched pairs in used working shape. So when the tweeters go, you would be better off replacing with something more modern at a lower price. As good as the Infinity Emit-R was in its day, when I bought my RM-1 speakers in 2001, it would be considered the end of the Emit-R reign as a standout mid-priced tweeter.

No reason to look for alternative Spiral Ribbons yet, since we have a few NOS available.

[PMAT]

I had my RM-1's modified by another speaker builder. We put in 4 8" peerless bass drivers at $85 each. The passive hole was covered and ported with the port facing down. We then braced the cabinet and replaced the stuffing. The speakers have an incredibly tight low end now. The midrange now can shine without the interference from distortion harmonics from the bass drivers. There still seemes to be some problem with mid to tweet integration. This summer I want to install BG tweeters and move the tweeters closer to the mid panels. My woodworking skills are good enough now to do that. It will look cool as well. I now listen to my Carver AL-IIIs a lot. They are VERY coherent and made me notice the mid-tweet integration problem with the RM-1. It is quite poss that the crossover is the problem as well. We shall see.

[DFaulds]

Well if you replaced the woofers without doing anything to the crossover, then yes the crossover is now a major problem.  You'll make even more of a problem if you replace the tweeter without any crossover changes, but if you like the results more power to you.

I'm always amazed when people start replacing drivers in their speakers without corresponding crossover mods.  Of course, I'm also not surprised when the same people say that their mods made a big improvement.

[PMAT]

The bass drivers were chosen and integrated with great care. The crossovers were measured for accuracy and one was modified to match the other as they were not the same measured values. This was not a drop in mod. We changed the whole bass design as I mentioned. The mid/tweet issues could be many things. Part of which is the distance between drivers which favors farfield listening. Fun to play with.

[7x57]

While the exact 8" woofers that Brian used are not listed on the Misco website, I did find one that looked eminently suitable as a replacement, the Misco MC8W-4A or MC8W-8A, whether you want to use two of the former in series for 8-ohm setup or two of the latter in parallel for 4-ohm setup.  I would use two of the MC8W-4A in series because of the greater Xmax capability and you will come in close to the specification of 89 dB sensitivity. It would also make an easier drive for most tube amps.

Except for the use of a polypropylene cone, this was probably the Megawoofer that Brian used as an upgrade or option to the RM-1.

The standard RM-1 woofer was probably based on the cheapest 4-ohm 8" Misco woofer that is listed on the website. It has the same 12 oz. magnet and 1" aluminum voice coil and similar resonance frequency and the same polyether foam surround. Add a trim ring, phase plug, and some putty like on the original standard woofer, and I think you have the same exact woofer, and the trim ring and phase plug can be supplied from your old woofer. Just cut off the center cap and install the old phase plug then add some putty near the center of the cone. Glue on the old plastic trim ring and you should be back to original.

However, I would buy the MC8W-4A if it were me and run them in series. Two of the MC8W-8A in parallel will be below 4 ohms in impedance and may surpass the midrange and tweeter in loudness even with the L-pads turned all the way up. Also, you get more linear Xmax with the 4-ohm drivers and my amp will put out all the power they can handle safely even as an 8-ohm load.

At the low crossover used in the RM-1, I don't see the need for a graphite coned woofer, but if you need one, then Parts-Express or Madisound carries an 8", 8-ohm Audax woofer with graphite cone for $149 that will fit with some baffle and grill woodwork. Madisound also carries a couple of SEAS Discovery 8" models that will work with fiberglass cones, cast baskets, and very smooth response, in 8-ohm or 4-ohm, and for around $80 each. There is no shortage of good woofer replacements for the RM-1.

If using a metal cone woofer, then breakup around 2-3 kHz may be a problem due to the 6 dB first order network. The crossover can be modified to QSO specs by using about 10 uf in parallel for 8-ohm duty and 20 uF in parallel for 4-ohm duty. That will place you close to 2 octaves away from the series inductor crossover point, but the capacitor will kick in well below cone resonance. Tweak to your particular woofer, of course. Those are ballpark figures. Dayton Audio and SEAS have metal cone woofers that could work. ScanSpeak can be considered as well.

But to use the woofer cutouts that came standard on the RM-1, the Misco woofers listed on the website all had the same steel basket.

Before I got rid of the passive radiator and went with a standard bass reflex port, I would look into using a resistive flow port to make an aperiodic vented enclosure. I stuffed a rolled-up cotton towel into the slot radiator port opening (being careful not to restrict PR movement) and got increased output at 32 Hz and lower, but a bit less output above 40 Hz. Sounded different, not really better or worse, so it's a personal thing. An acoustic suspension tuning would probably work best if used in a small room. A piece of closed cell foam cut slightly bigger than the slot radiator port and completely sealing the port would let you check out that possibility. Acoustic suspension produces some of the best bass in many rooms because of the slow rolloff that begins sooner but extends further into the deep bass.

[Stimpy]

While I appreciate your investigations, does Misco sale to the general public?  In small quantities?  I was under the impression, that Misco sold at minimum, a complete production run?  If this isn't fact, I'd love to know the purchasing details for buying Misco product, as I'd like to buy their drivers too!

Thanks!

While the exact 8" woofers that Brian used are not listed on the Misco website, I did find one that looked eminently suitable as a replacement, the Misco MC8W-4A or MC8W-8A, whether you want to use two of the former in series for 8-ohm setup or two of the latter in parallel for 4-ohm setup.  I would use two of the MC8W-4A in series because of the greater Xmax capability and you will come in close to the specification of 89 dB sensitivity. It would also make an easier drive for most tube amps.

Except for the use of a polypropylene cone, this was probably the Megawoofer that Brian used as an upgrade or option to the RM-1.

The standard RM-1 woofer was probably based on the cheapest 4-ohm 8" Misco woofer that is listed on the website. It has the same 12 oz. magnet and 1" aluminum voice coil and similar resonance frequency and the same polyether foam surround. Add a trim ring, phase plug, and some putty like on the original standard woofer, and I think you have the same exact woofer, and the trim ring and phase plug can be supplied from your old woofer. Just cut off the center cap and install the old phase plug then add some putty near the center of the cone. Glue on the old plastic trim ring and you should be back to original.

However, I would buy the MC8W-4A if it were me and run them in series. Two of the MC8W-8A in parallel will be below 4 ohms in impedance and may surpass the midrange and tweeter in loudness even with the L-pads turned all the way up. Also, you get more linear Xmax with the 4-ohm drivers and my amp will put out all the power they can handle safely even as an 8-ohm load.

At the low crossover used in the RM-1, I don't see the need for a graphite coned woofer, but if you need one, then Parts-Express or Madisound carries an 8", 8-ohm Audax woofer with graphite cone for $149 that will fit with some baffle and grill woodwork. Madisound also carries a couple of SEAS Discovery 8" models that will work with fiberglass cones, cast baskets, and very smooth response, in 8-ohm or 4-ohm, and for around $80 each. There is no shortage of good woofer replacements for the RM-1.

If using a metal cone woofer, then breakup around 2-3 kHz may be a problem due to the 6 dB first order network. The crossover can be modified to QSO specs by using about 10 uf in parallel for 8-ohm duty and 20 uF in parallel for 4-ohm duty. That will place you close to 2 octaves away from the series inductor crossover point, but the capacitor will kick in well below cone resonance. Tweak to your particular woofer, of course. Those are ballpark figures. Dayton Audio and SEAS have metal cone woofers that could work. ScanSpeak can be considered as well.

But to use the woofer cutouts that came standard on the RM-1, the Misco woofers listed on the website all had the same steel basket.

Before I got rid of the passive radiator and went with a standard bass reflex port, I would look into using a resistive flow port to make an aperiodic vented enclosure. I stuffed a rolled-up cotton towel into the slot radiator port opening (being careful not to restrict PR movement) and got increased output at 32 Hz and lower, but a bit less output above 40 Hz. Sounded different, not really better or worse, so it's a personal thing. An acoustic suspension tuning would probably work best if used in a small room. A piece of closed cell foam cut slightly bigger than the slot radiator port and completely sealing the port would let you check out that possibility. Acoustic suspension produces some of the best bass in many rooms because of the slow rolloff that begins sooner but extends further into the deep bass.

[John Casler]

No Misco has minimum orders depending on the model and I would suggest that it is not a good idea to encourage people to contact Misco inquiring about purchasing a pair here and there.  They are a manufacturer and not a retailer.

Madisound, and Parts Express do sell single drivers and small quantities, so those are the best bets.

 

Add a trim ring, phase plug, and some putty like on the original standard woofer, and I think you have the same exact woofer, and the trim ring and phase plug can be supplied from your old woofer. Just cut off the center cap and install the old phase plug then add some putty near the center of the cone. Glue on the old plastic trim ring and you should be back to original.

Not sure what is being suggested here, but ONLY the Passive Radiators had putty on them NEVER an active driver

[7x57]

John, the standard 8" woofer on the RM-1 is the Misco 8"4-ohm version with 12 oz. magnets, a 1" aluminum voice coil, polypropylene cone, with the dust cap removed and a wooden phase plug attached to the pole piece. Also added is a plastic trim ring that the standard woofer listed on the Misco website does not have. The trim ring is glued on, can be popped off, and added to a standard Misco 8" woofer. On two woofers in my kit was attached one coil of putty near the voice coil former, and on two woofers was attached two coils of putty near the voice coil former. I called Brian and discussed the differences in the woofers. The woofer with one coil of putty went on top near the Neopanel and the woofer with two coils of putty was placed in the bottom position.

The putty lowered the resonance frequency of both woofers, and it also caused two slightly different resonant frequencies to occur, thus spreading out the resonances and extending the response lower, just as the passive radiator could be tuned to a lower resonance still yet. Brain chose a frequency range far below what Misco intended these woofers to cover, and the putty gives a faster rolloff of high frequencies than the Misco website shows and it also reduces any high frequency resonances in the cone, which is important with a first order network and eliminates the need for second order filtering to get rid of it.

Hopefully, Misco will inform me of any dealers that carry the standard Misco woofers. Madisound carries some of them, but not the 8" woofers. They DO carry 6.5" Misco midwoofers that might work in some VMPS speakers such as the 626R. A call to Madisound with an interest in continual purchases of the 8" MC8W-4A and MC8W-8A might get them to stock the woofers.

[John Casler]

While I do not doubt that your particular RM-1 woofers may have had some putty, that was not the norm at all.

None of the 25 pair I owned or placed had putty except to the PR, and nor did any of the other RM or Sub models have putty on the active drivers, so it is possible that there were some that had out of spec active drivers, and Brian used a mechanical remedy, but it was not normal and it is important that other owners don't get confused.

There are many examples of a "one off" or a handful of speakers that had different design elements.

I have been, when possible, assembling enough owners to place volume orders for the 6.5" drivers and send the proceeds to the widow, but you can certainly suggest that owners go to Madisound as an alternative.

This is also true with a small stock of NOS Spiral Ribbon Tweeters, Neopanels, and DynaRibbons.

[Stimpy]

I just found this thread, on the Parts Express "Tech Talk" Forum.  Member 'DanHine' mentions emailing and visiting Misco, with the desire to purchase Misco drivers for DIY use.  Misco responded with this follow-up email:

"We do sell to individuals but the individual would need to specify the speaker and they are not returnable."

"The only minimum we have is $ 100.00"

http://techtalk.parts-express.com/showthread.php?235572-Minneapolis-Speaker-Company-anyone-have-questions&s=d22ea0821e9042c008552d561fdb9420&p=1881315#post1881315

As such, I just sent an email to Misco customer service, asking for purchasing guidelines, and confirmation of their minimum order requirements?  When I receive a response, I'll post the details here.

Hopefully, Misco will inform me of any dealers that carry the standard Misco woofers. Madisound carries some of them, but not the 8" woofers. They DO carry 6.5" Misco midwoofers that might work in some VMPS speakers such as the 626R. A call to Madisound with an interest in continual purchases of the 8" MC8W-4A and MC8W-8A might get them to stock the woofers.

As to RM-1 active woofers, with added putty, I can confirm 7X57 experiences.  I have 4 sets of older RM-1 woofers, several of which have 1 or 2 layers of a hard putty applied to the center of the cone, where the dust cap used to be mounted.  The woofers have an added wooden phase plug too.  The woofers I have weren't from Misco, but Infinity.  They're Infinity IMG  8" woofers, with trim rings, Infinity part number 902-6774.  I hope to one day complete a line array system, with these, and about 14 Neo planar drivers, and several sets of ribbon tweeters, that I'm currently sitting on.  I need to finalize driver lay out and the crossover.  I hope to use a Brian inspired crossover design, with 1st order series crossovers.  Should be fun, at least!

John, the standard 8" woofer on the RM-1 is the Misco 8"4-ohm version with 12 oz. magnets, a 1" aluminum voice coil, polypropylene cone, with the dust cap removed and a wooden phase plug attached to the pole piece. Also added is a plastic trim ring that the standard woofer listed on the Misco website does not have. The trim ring is glued on, can be popped off, and added to a standard Misco 8" woofer. On two woofers in my kit was attached one coil of putty near the voice coil former, and on two woofers was attached two coils of putty near the voice coil former. I called Brian and discussed the differences in the woofers. The woofer with one coil of putty went on top near the Neopanel and the woofer with two coils of putty was placed in the bottom position.

The putty lowered the resonance frequency of both woofers, and it also caused two slightly different resonant frequencies to occur, thus spreading out the resonances and extending the response lower, just as the passive radiator could be tuned to a lower resonance still yet. Brain chose a frequency range far below what Misco intended these woofers to cover, and the putty gives a faster rolloff of high frequencies than the Misco website shows and it also reduces any high frequency resonances in the cone, which is important with a first order network and eliminates the need for second order filtering to get rid of it.

[7x57]

Stimpy, is there any chance that the Infinity IMG woofer was also manufactured by Misco? Misco does not sell finished loudspeaker systems, so the only way they make money is by selling drivers to people who do. Maybe the IMG cone was the only thing that Infinity produced, patented to them, that Misco assembled  for them, or Infinity used their cones in a Misco basket/magnet assembly? Who knows.

Even loudspeaker manufacturers who "make" their own drivers are often assembling components they get from somebody else. There are manufacturers that mainly just make cones, such as hemp cones for guitar amp drivers. Many loudspeaker manufacturers that make their own drivers are thus actually just assemblers that get their component parts from various sources. An exception would be Ohm that makes the Walsh driver that is used in no other loudspeaker.

RCA 5881 tubes were made by Tung-Sol, just the labeling is different. Same for some snow skis. A ski sold as Atomic may be a Fischer ski with a different graphic topsheet or a different waxless base pattern. It's cheaper to use somebody else's existiing tooling if they have excess manufacturing capability than to set up new tooling for what a limited manufacturer would be able to sell. The specs, resonant frequency, voice coil former, frequency response, foam surround are what I see in the Misco 4-ohm 1" voice coil woofer. Brian may have ordered the Infinity version from Infinity. Who knows? But the specs say the Misco woofer would work just fine.

I also sent an email to Misco yesterday, but they have yet to respond to me. I also sent an email to Madisound to see if they could procure the Misco drivers to sell to VMPS owners. If direct orders to Misco are $100 minimum, then I have no trouble with that and will probably just give them a call soon.  I want the upgrade woofer with 1.5" voice coil and big 38 oz. magnet. The specs say it will also correct for a slight depression in the lower midrange just above crossover.

[7x57]

I have been at www.audioheuristics.org and looking at charts of various tested 8" woofers. They include the Vifa P21 (Vandersteen Model 2), Seas W21, HiVi M8N, Dayton Audio RS250, ScanSpeak 8555, and Silver Flute 4-ohm 8".

The Dayton Audio RS250 was the winner, beating out the ScanSpeak 8554 and Seas W21 at low frequencies.

The two worst speakers were the Vifa P21 and Silver Flute 8". It is very obvious that the SF8 was patterned on the Vifa P21, differing mainly in the unique wool cone and costing half as much. In spite of the poor measurements at low frequencies, both can beat more expensive drivers at mid and high frequencies. Richard Vandersteen fights the low frequency distortion in the P21 by doing a mod to the driver and also handing off duty to the Active Coupler below about 55 Hz. I would order a Silver Flute 8" 8-ohm as a low cost replacement in an old Vandersteen Model 2 loudspeaker at less than $40 delivered from Madisound. The SF8 is available in 4-ohm and 8-ohm, and since it is patterened on the P21, obviously, it has a huge replacement market as the Vifa P21 is one of the most used high end woofers of all time, still being manufactured by ScanSpeak.

The HiVi M8a and M8N were low priced champs, soundly beating the SF8 and P21 at very low frequencies, but having metal cone breakup at 2KHz which renders them questionable in a 2-way design. Since the RM-1 crosses low and you are not a slave to the first order network that Brian chose, the HiVi M8a and M8N are very viable candidates if you switch from an 8-ohm to 4-ohm network that my RM-1 possesses.

The five-tone burst test is the one that really describes how a woofer is going to sound playing a lot of frequencies at once. In this regard, the P21 and SF8 do quite well. There are lots of reviews of the SF8 where owners say it performs very well against the expensive Scandinavian drivers. The only real downfall of the P21 and SF8 are the high levels of 2nd and 3rd harmonic distortion at a steady 60 Hz test tone. If you listen to loud rock music, the bass guitar amp may very well have far more distortion than that in the bass cab. It would matter more to acoustic bass fans.

Since the SF8 comes in 4-ohm with very similar data to the Misco 8" 4-ohm, then it is a drop-in fit for a Misco 8" I have. Madisound recommended the SF8 to me as being the most appropriate and he had done simulations and found them similart. Madisound said they would not be stocking the Misco 8 as the Silver Flute is so similar. So there you have it, IF YOU WANT A DROP-IN REPLACEMENT, then get one of the Silver Flute woofers in the impedance that matches your old woofer. The cost is so low that it makes refoaming a lost cause. An old woofer has a tired suspension as well, which a refoam will not solve.

If you are not afraid of some crossover network changes, then the HiVi M8N is a a very good performer, and the M8N will need some woodwork. The HiVi woofers are the best looking, if you run sans grills.

For a bit more than HiVi you get a Dayton Audio metal cone driver that beats the high priced Scandinavians in the low frequencies, which is mainly what the RM-1 woofer reproduces.

I listen mainly to electric bass music, so I see the SF8 4-ohm as the best alternative for me and the crossover should need no change. Total cost for 4 woofers from Madisound is well under $160. The Silver Flute woofers have been around a while and people are loving them in general.

I am probably going to order a couple of Silver Flute 8" 8-ohm drivers and put them in the Vandersteen 2Ci. People will probably not pay me a penny more whether the speakers have Vifa P21 or SF8 woofers installed. After 23 years, the 2Ci woofers are getting tired and rattling and the surrounds are deteriorated. Vandersteen wants far more than new SF8 drivers for a rebuild, and when you count postage both ways to Vandersteen, new Vifa P21 woofers are even less costly. People have replaced the Vandersteen modded P21 with a standard P21 woofer and were pleased with the results. Rated sensitivity is higher for the standard P21 than the typical 86 dB that my 2Ci woofer produces. The standard 2Ci woofer gave me less than -3dB at 32 Hz sitting in the same place as my RM-1, so the RM-1 meets its specs and the 2Ci did not, although rated -3 dB at 29 Hz.