Polk Audio Monitor 4 / LF 14 System

Stev187

Hello. I am new to this forum, but not new to Polk Audio speakers. I'm posting to share about a milestone in my use of the Monitor 4 / LF 14 system.

I purchased my Polk M4s back in 1983 with money I made mowing lawns in the neighborhood back when I was 15 years old. I still have the receipt! I later added the LF14, and I loved that combination in my bedroom, which was too small for floorstanding speakers. While the LF 14 has spent a number of years in the basement (or pulling double duty as an end table without being plugged in), it's not an exaggeration to say that I have listened to these Monitor 4s nearly every day of my life since I purchased them. While the LF14 often stayed home, the M4s were with me in every dorm room, apartment, and house I've lived in. For about 14 years they were wired into the bookshelves of our living room. Now they live with me in my office.

The poor LF14 has really been out of use since my childhood bedroom days. As Polk fans will know, this isn't a "subwoofer" by today's home theatre standards. It's more like a "low frequency" unit (which is where that "LF" comes from in its name). This thing won't rattle the windows; it's designed for what I used it for in my childhood room: expanding the low frequency response of a pair of nice bookshelf speakers.

My only disappointment over the years with the M4/LF14 system has been the passive nature of the hookup with a single amp. The LF14 has a sophisticated and switchable (not selectable) crossover on board, and it's designed to be used as a mono unit or in stereo pairs. I always dreamed of getting a separate power amp and/or crossover for the LF14 to really tweak the sound and get a little more low end from the unit.

If you're not familiar with the LF14, its enclosure has two of the Polk MW6500 drivers (just like the M4) and one of the passive radiators you find in the SDA series from the same era. I also have a pair of SDA 2A floorstanding speakers that I inherited from my parents (they bought them at my suggestion back in the day).

Years ago, when I was trolling eBay for interesting stuff, I picked up the plate amp from a Polk PSW450 subwoofer. "This might come in handy for that LF14 some day," I thought. Then I tucked it away. Well, today, I finally hooked that thing up, and boy am I happy about it.

First, I wanted to leave the LF14 as-is so I could reverse everything if needed. While it did occur to me to cut a big hole in the cabinet and mount the plate amp inside the LF14, I simply bypassed the crossover and ran wires into the cabinet, hooking the MW6500 drivers in parallel. This is a mono setup; note that the LF14 is designed to take both a Left and Right signal from a conventional amp so that the signal coming from the enclosure is a blending of both channels.

It turns out that the PSW450 plate amp was the perfect choice to drive the LF14 in this "quasi bi-amp" configuration. I can select the volume of the LF14, and the "Low Pass" pot allows for a selectable crossover. There's even a nifty option of running the entire system in a bi-amp mode with the crossover inside the plate amp. While that is cool to experiment with, I am simply running the M4s full range and supplementing the low frequencies with the LF14. Quite honestly, it's the only thing that has improved on the setup in the 30+ years I've used it (and these speakers have been connected to a multitude of amplifiers over the years).

The setup at the moment:

• PC/Internet music source
• DAC
• NAD 310 integrated amp
• Polk Audio PSW450 plate amp
• Polk Audio Monitor 4s
• Polk Audio LF14

Thanks for letting me share. My SDA 2A speakers are currently not being used, so when I get a good listening room set up for them I will probably post again. Those are great speakers.

I'll conclude with the text of a review of the M4/LF14 combo I found recently; this was published about the time I purchased my speakers at Absolute Sound in Royal Oak, Michigan.

Steve

One of the best examples of this is the Polk Monitor Four speaker. Though small in size, the Monitor Four's sound remarkably like the larger, more expensive Polk speakers. The Polk Monitor Four's can also be an excellent choice for a second set of speakers. You can put music into another part of your home without the expense of all new equipment. Best of all, by adding the Polk LF-1 4 Deep Bass Subwoofer, the Polk Monitor Four's can be quickly, easily, and inexpensively converted into a high performance system comparable to the finest speakers anywhere. Imagine how convenient it can be to carefully position the small sized Monitor Four's in the place that best fits your listening room . . .on a shelf. . . in a bookcase. ..on a stand. ..then add the power and deep bass performance of the LF-14 which can be placed almost anywhere, even out of view and still deliver a remarkable inspiring performance.

Cincinnati Enquirer
January 1, 1983

Note 1: The rubber surrounds in all of these Polk speakers are in great shape. My son has a pair of the later generation M4s in his room at home. While they are nice, the tweeters are different and they don't sound nearly as clean and tight as my beloved pair of M4s.

Note 2: The NAD 310 is a great little office amp. It's tiny in terms of power (20w+20w) but it has a unique design that makes it a very musical amp. Now that the LF14 is getting help from the PSW450 and doing its job, I can engage the tone defeat and get a very transparent, clean sound.

dromunds

Yeah man, I picked up some Monitor 4's with Peerless tweets awhile back and I enjoy them mucho. Remarkable is a good word to describe them. Nice write-up you did here. Thanks.

Stev187

Thanks. I thought I'd post some quick photos. These little M4s have given me so many hours of listening pleasure over the years; adding some juice to the LF14 is really nice. This system sounds great.

Steve

dromunds

If I may offer a suggestion, you may get even better sound with an upgrade to some nice speaker cables that jive. BTW, I sometimes do a similar thing with my Monitor 4's, I can use a pair of vintage 15" JBL 2235 LF drivers for an excellent low end compliment to the Monitor 4's. The JBL's are driven by a modded Carver M500t from a separate preamp output channel with an active crossover. I can run the Monitor 4's full and expand the LOW frequencies with the JBL's. Fun.

Nightfall

I have the same M4's too, nice little speakers for sure.

Stev187

Thanks, everyone. Yes, this rig will be getting decent wire and banana plugs; that's just what I had in a drawer in the office.

I must say, adding the juice to that LF14 gave this setup new life. Nice listening today at work: I played a bunch of Bach organ works and motets, some bass-guitar-heavy post punk, and The Arrival of Victor Feldman (1958). On that Vic Fedlman record, it sounded like Scotty's bass was right there in the room!

Question: I realize these LF14 units aren't museum pieces or very valuable. Would you consider mounting the plate amp in the sub? I can see this both ways. On the one hand, it seems like the perfect place for it; gets it out of the way. On the other hand, it really kind of messes it up for future use at it was designed. I doubt it's worth very much, so probably no reason NOT to do the modification. Thoughts?

Hofy

Try building a small box for the plate amp. Poultrygeist over at Audiokarma did this with his plate amp for his bucketsubs.

dromunds

+1

Hofy

BTW I have a pair of Monitor 4 speakers that I have been enjoying since spring. They are Goodwill finds that are a bit rough, but will get restored this winter.

Faustin

I had a pair of the early 4's that I paid less than $20 for the pair. I rebuilt the c/o's and reveneered then and then gave them away to a family friend as a college graduation gift. I still keep my eyes open for another pair.

Stev187

Great looking refinish job! I've thought of doing that with mine, but they're actually in decent shape.

Q. Do you think the crossovers have deteriorated? I've owned them since September of 1983.

There's a reasonably-priced pair with the old tweeters on eBay right now.

Also, great tip about the wooden enclosure. I had considered something like that, and I think it would be much better that mounting inside the enclosure.

Thank you all.

SR

Hofy

Faustin, do you remember the year of the Monitor 4s that you rebuilt? The cross overs are completely different from mine. I have just the 2 inductors and a single 5.8uF cap. Mine are from Dec 1982.

Hofy

Stev187 wrote: »

Great looking refinish job! I've thought of doing that with mine, but they're actually in decent shape.

Q. Do you think the crossovers have deteriorated? I've owned them since September of 1983.

There's a reasonably-priced pair with the old tweeters on eBay right now.

Also, great tip about the wooden enclosure. I had considered something like that, and I think it would be much better that mounting inside the enclosure.

Thank you all.

SR

Yes it would be best to freshen up the crossovers. I posted a pic of one of mine above. It is a fairly simple crossover and you would have to replace just a single capacitor in each one. I ordered the Dayton 1% 5.6uF from Parts Express for $4.64 each. If your crossovers look like Faustin's do then you will have 2 caps and 1 or 2 resistors to replace.

Nightfall

@Hofy do yours have the Polk emblem on the bottom front with the grill stopping short of the bottom where the emblem is or is your emblem on the grill itself?

Hofy

Nightfall wrote: »

@Hofy do yours have the Polk emblem on the bottom front with the grill stopping short of the bottom where the emblem is or is your emblem on the grill itself?

My have the emblem, or had it, on the cabinet itself. You can kind of see where it was before someone so lovingly painted painted the cabinets with black latex paint.

Faustin

Hofy wrote: »

Faustin, do you remember the year of the Monitor 4s that you rebuilt? The cross overs are completely different from mine. I have just the 2 inductors and a single 5.8uF cap. Mine are from Dec 1982.

My c/o's were dated 3-19-82. If I remember correctly they had the same value caps and resistors as Monitor 10's. I contacted Polk to try to determine if these came from the factory with those c/o's or if someone possible switched them after the fact. All Polk said was that they were original c/o's. Did not address the question of Could they have left the factory with these c/o's. I would be curious to know
if anyone else has a pair with c/o's like mine.

Hofy

@Faustin interesting! With the exception of the extra cap between the resistors that looks like the crossovers from my 1982 Monitor5A.

mhardy6647

I have nothing useful to add to this thead, but I will waste some bandwidth here and say: Very cool to have a pair of the early Monitor 4s and an LF14!

Stev187

mhardy6647 wrote: »

I have nothing useful to add to this thead, but I will waste some bandwidth here and say: Very cool to have a pair of the early Monitor 4s and an LF14!

Thanks to everyone who has weighed in on this thread.

I really can't overstate how important these little speakers have been to me over the years. I dug out my receipt today: I paid $218 for them in September of 1983. That's $528 in 2016 dollars. I'm also pinching myself at how perfect the PSW450 plate amp is for this system. It just works perfectly.

Some day in the future, I want to set up my late father's SDA 2A in the same listening room and compare the two systems. (I have the connector cable for the SDA 2A set, also). Honestly, I think that with the LF14 properly amplified, these M4s could give the SDA 2As a major run for their money.

I'll look into the re-cap on the crossovers. My SDA 2As also have the same drivers, so perhaps I would do those as well.

Side note: when I was in grad school, one of the peerless tweeters failed. I called Polk, and they sold me a new one. This would have been in the very early 90s. It looks the same, but it's silver like the ones in this photo:



Those aren't my speakers, but that's what the 90s replacement tweeter looks like. Is it still a peerless?

Thanks again to all of you for talking about this stuff with me.

Steve

Hofy

Not Peerless. Those are Polk SL1000 that are closer to the SL2000 silver domes. Vintage Peerless show up on eBay all the time.

Nightfall

Yuck, replace that SL1000 with a Peerless tweeter.

dromunds

Yes pick up one of the Peerless in the for sale FM. Also, i think the 2a is quite expensive to upgrade because of the set up of the crossovers check out old discussions of that on the forum. Others can chime in, I had some a long time ago and if I remember the crossovers are twice as expensive to upgrade as the 2b for example. Talk to Westmassguy or others about crossover parts for the Monitor 4's. If you prefer I'm sure he or others could upgrade the crossovers for you. I need to upgrade my crossovers also one of these days. . Good luck.

westmassguy

The replacement tweeter for the SL1000, is the RDO-194-1, not the Peerless.

Hofy

westmassguy wrote: »

The replacement tweeter for the SL1000, is the RDO-194-1, not the Peerless.

Stev187 stated his Monitor4s came with Peerless and when one went bad Polk replaced it with an SL1000. As you know there is no way the RDO-194 will fit the opening for the Peerless.

westmassguy

Hofy wrote: »

westmassguy wrote: »

The replacement tweeter for the SL1000, is the RDO-194-1, not the Peerless.

Stev187 stated his Monitor4s came with Peerless and when one went bad Polk replaced it with an SL1000. As you know there is no way the RDO-194 will fit the opening for the Peerless.

That's because Peerless stopped making that model, after the molds broke. Polk had already developed the SL1000, which they sent out as replacements.

Hofy

westmassguy wrote: »

That's because Peerless stopped making that model, after the molds broke. Polk had already developed the SL1000, which they sent out as replacements.

OK. I know you are a fountain of Polk knowledge, can you tell us if the SL1000 is the same size for the cut out as the Peerless or is it the same size as the RDO-194. I ask as I have never seen the SL1000 but have both the Peerless and the RDO-194. I just hope to get Stev187 one the path to the best replacement for his mismatched tweeters.

Faustin

The Peerless and SL-1000 cutout are the same. If I remember correctly, the c/o component values are different for revisions that went from Peerless to SL-1000. Probably best to check the actual speaker crossover component values and also the schematics listed under the Vintage forum.

machone

My SDA-1As had SL1000s before I replaced them with RDO-194s. The 194s require a larger cutout.

Stev187

Just checking in to say I am still loving my Polk M4/LF14 combo with the plate amp. It's such a nice system. Again, I have loved these speakers since I purchased them, but having more power to the LF14 is such a game changer.

Today, I purchased a copy of the 1984 Audio Magazine annual equipment issue. There is a very long center section on the Polk line for that year. It looks like they changed away from the Peerless tweeter that year (mine had them). The opening shot is this funny full-page photo of a technician checking out an LF-14. The Polk marketing of the time played up the whole "white lab coat" image.

Cool photo. I'm glad I've kept this LF-14 all these years.

Steve

xschop

Those LF-14 are really neat. What is the freq. range on them?

xsmi

Stev187 wrote: »

Just checking in to say I am still loving my Polk M4/LF14 combo with the plate amp. It's such a nice system. Again, I have loved these speakers since I purchased them, but having more power to the LF14 is such a game changer.

Today, I purchased a copy of the 1984 Audio Magazine annual equipment issue. There is a very long center section on the Polk line for that year. It looks like they changed away from the Peerless tweeter that year (mine had them). The opening shot is this funny full-page photo of a technician checking out an LF-14. The Polk marketing of the time played up the whole "white lab coat" image.

Cool photo. I'm glad I've kept this LF-14 all these years.

Steve

I had always remembered this picture in my mind incorrectly as Monitor 10's. I'm glad I ran across this thread.