Fun but not a looker: Klipsch KP-301
Klipsch KP-301s are part of the Klipsch Professional line- the speakers Klipsch makes for professional sound reinforcement. You’ve seen them mounted on poles by DJs, hung from rafters of skating rinks, concert venues, churches, and the like, and hefted by roadies in and out of vans for touring bands. In some cases they are very similar to their civilian counterparts from the Klipsch Heritage line (i.e. Heresy, Cornwall, La Scala, etc), save different outer coverings, handles, or grilles modified to handle more abuse.
The KP-301s I have here are closely related to the Klipsch Chorus I, a large 3-way speaker with a 15″ woofer, massive midrange horn, and horn tweeter. The woofer is upgraded over the garden variety Chorus and is rated for 400 watts at 4ohms and will allow the entire speaker take an equal amount of wattage for extended periods. Overall, this speaker has an efficiency of 101db/watt at one meter and can play at 125db-plus for extended periods of time. It’s made out of 3/4″ birdch ply and with its speckled black outer coating, hefty plastic bumpers and handles, and heavy-duty plywood and fabric grille weighs over 80lb, makes for quite a presence.
I bought my pair well-loved from an amateur rock musician getting out of the business. They were dented and scratched but complete. Upon hooking them up, I realized that neither one was outputting from the tweeters, and when I took off the grilles, one of the speakers had a replacement JBL 2226H woofer. That’s an awesome driver but not original and at 8ohms, not a match for the crossover. So these would need some work. And that’s when I got to thinking….
I’ve said before that Klipsch heritage speakers are a lot like American muscle cars – lots of people love them, they’re simple and easy to work on, and enthusiasts go beyond restoration to modify them to taste. That’s what I was going to do here.
First I pulled all of the com
ponents out, which lightened the boxes down to about 45 pounds apiece. The 15″ woofers themselves weigh 15lb. I used 1×1″ wood plank to make internal bracing to link all of the opposing cabinet panels to one another, and to reinforce each panel lengthwise. The additional bracing, well glued and secured, should eliminate all resonance from the massive panels. True to form, these massive boxes now have almost no resonance when subjected to the knock test. I added 6″ tubes to the open 4″ diameter dual holes in each cabinet, which, according to my calculations, should tune the box down and provide more oomph in the 40-50hz range. This is important given I am making these into home-use speakers where additional low-end emphasis will be important – commercial speakers usually eschew the lowest bass notes for clarity, durability and massive power handling.
I then ran through a number of sheets of sandpaper pulling off the years of accumulated gunk over the hardy speckled outer covering, getting down to the bare plywood. Multiple careful applications of wood putty helped smooth out the battle scars, but making these look new and blameless was beyond my abilities. I mitigated this by applying a smooth primer sealant and following up with a fine fiber roller application of black gloss house paint. This provided its own texture which created an even, glossy mottled surface. The end result is somewhere in between a home speaker and a professional. It’s got a semi-industrial vibe to it. As an exercise in finishing, it was an interesting approach. My wife wanted to add red racing stripes, and we may still do that if the mood strikes.
I rebuilt the crossover using new Mills resistors and Dayton 1% poly capacitors. This was straightforward and with the large wood slab crossover, there was plenty of room to work. The only challenge was to confirm the values for all of the components on the crossover as there is some debate as to the final crossover specs – the KP301 and subsequent KP301 II have different horns, sensitivities, and crossover points. I learned the KP-301 is very close to the Chorus I in construction.
The dead tweeters were brought back to life with new titanium tweeter diaphragms from Bob Crites. These are an easy swap and dealing with the Crites family is always a delight.
After finishing I put everything back together, threading drivers and horns back into the cabinets around the new bracing. After putting it all back together I demoed the speakers with my Fisher 500C tube amp, recently put back into service to test some KEF LS50s.
What’s the verdict?
Well, I’ve had a ton of Klipsch speakers – Klipschorns, Heresys, Tangents, Quartets, Cornwalls, Fortes (I and IIs), and these KP-301s. I have a pair of Klipsch CF4 Series 1 that I will never part with. And I have to say that out of all of that horn goodness these are the most fun. This is the muscle car to have. They are lightning quick, razor sharp, alive. The Fisher on Volume 1.5 is pushing more liquid tube watts than these need to blow you out of the water. The bass is not menacing, it is not blowing the doors off, but it is accurate, round, and full down the octaves.
For messy massive cabinets with drivers screwed into thick plywood and little time alignment, these image exquisitely. Maybe it’s a function of their sensitivity but stereo sweeps like the drum lines in Rush’s YYZ are stronger and more accurate than they should be. Getting this type of performance out of a dedicated and lauded monitor like the LS50 takes exponentially more watts and 10x the money in high-quality playback and amplification componentry.
These. Are. So. Much. Fun.
If you can get past the size and you can get past the looks these are an amazing set of speakers. And Klipsch professionals go for cheaper than their Heritage counterparts with sturdier components – it’s a no-brainer.
I love the sound and the amazing result of this restoration has really motivated me to take on a crossover refresh and bracing for my CF-4s, which I absolutely love as-is. I know that as much as they are great now, the types of mods I put into the KP-301s will take them into the stratosphere.
Info on the Klipsch KP-301 from the manufacturer (courtesy of the Klipsch Forums):
The Klipsch Professional KP-301 is a compact, full-range loudspeaker system that is exceptionally accurate. Its high output, high power handling, low distortion and smooth frequency response make it an excellent choice for music playback, such as in DJ or karaoke applications, as well as for live sound applications as a touring or fixed install speaker.
This three-way system features a 15-inch (380 mm) bass driver with a rigid, lacquer-dipped, rib-reinforced cone for extreme power handling. The midrange is handled by a 60° x 40° Tractrix® Horn coupled to a two-inch (50mm) titanium dome compression driver, with the high frequencies provided by a similar horn matched with a ferrofluid cooled, one-inch (25mm) polyetherimide dome compression driver. The KP-301 is equipped with a proprietary limiter device that automatically protects the high frequency driver from being overdriven.
The KP-301 is built from selected furniture-grade, 3/4-inch (19mm) void-free birch plywood with a 1-inch plywood motorboard. The finish is black textured paint with a black, powder-coated perforated metal grille. This is a portable model fitted with side positioned handles at the balance points and corner and edge protection.
MSRP: $976 each
KP-301
FREQUENCY RESPONSE: 50Hz – 20kHz±4dB (-10dB @ 39Hz) @ 3 meters, 1/2 space anechoic
SENSITIVITY: 101dB @ 2.83V, 1 meter, 1/2 space anechoic
POWER HANDLING: 400 watts (44.7V)
CALC MAX CONTINUOUS OUTPUT: 125dB
COVERAGE ANGLE: 60° Horizontal x 40° Vertical
DIRECTIVITY INDEX (DI): 9dB ±2dB
NOMINAL IMPEDANCE: 8 ohms, 5 ohms minimum @ 230Hz
TRANSDUCERS: One K-792-KP compression driver, one KP-66-E titanium compression driver and one 15″ K-48-KP woofer
CROSSOVER FREQUENCY: 800Hz and 6kHz
INPUT CONNECTIONS: Dual red/black five-way binding posts and dual locking Neutrik® D-shell 0.25″ phone plugs
DIMENSIONS (H x W x D): 32.625″ (82.9cm) x 20.825″ (53cm) x 16.825″ (42.9cm)
WEIGHT: 82 lbs. (37.2kg)
silverfacestereo 
Veneer isn’t all that expensive, but cutting it can be. If I were to veneer a pair of fine vintage speakers I’d talk tot he the local High School wood shop teacher. They are usually trophy grade cabinet maker and have the equipment at school and some pretty bright students that could use the experience making veneer or applying it. I have so AR 58s speakers that have that dreaded vinyl wood grain on them. My plan is to heat gun that stuff off and get some 1/8″ or 1/4 walnut and walnut wood tape and make those guys look as good as they sound.
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Cool! Look for my write up of my Polk Monitor 7 restoration on this site. I removed vinyl wood grain and applied cherry veneer. Good luck!
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I recently aquired a set of 301s used .. what do you recommend I do to them..
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Use my post as a guide for the full spectrum of what you can do. If you like how they sound now enjoy them for what they are. If not, here’s my prioritized list: Start with crossovers. Consider titanium replacement diaphragms for the horns. Then seal and brace cabinets. Next, consider port tubes. And then do whatever you want with the finish and color. Good luck.
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What are the fuse values of the KP301II used on the HF and LF sides?
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Don’t know. These were 301 series 1, and I unfortunately don’t have them anymore…
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Questions,
I have the same 301lls.
Did you open up the bass ports to 6″? Where did you get the new bass tubes?
Do you recommend Crites upgraded crossovers?
Both tweeter’s need new diaphragms, but finding diaphragms not made in china is nearly impossible so who do you recommend buying replacement diaphragms from?
Finally what 15″ woofers do you recommend and who do your recommend purchasing woofers from?
Thanks for your time.
Sincerely
Mike Winkle
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Hi Mike! I used port tubes of 6″ length, but left the holes the same diameter. Tubes were bought at Parts Express, no mods needed. They fit right in. I have never used Crites crossovers myself but the component quality is high, and I’ve read lots of very satisfied reviews. If you have some experience soldering, you can replace components in the crossover yourself and save money but everyone’s comfort and interest in DIY is different. Crites is not expensive for the quality you get. I bought non-titanium diaphragms on Amazon (likely Chinese manufacture) and I was satisfied. I recommend you look on the components websites (parts-express, madisound, crites) and find replacement components with manufacture data and reviews that meet your needs. Once again, Crites carries its own diaphragms which are more expensive but they’re tested and proven to perform. On the woofers, since I had one already I found it was cheapest to order another identical Klipsch woofer from eBay. I found a post on the Klipsch Forum that had some recommendations on which replacement woofers would be the best match for the original Klipsch ones. If I remember correctly, the recommended replacement was the Eminence Kappa 15LFA. Pricey but excellent. Good luck!
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