Polk Audio Monitor 4 / LF 14 System

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.