Antone

John, Thanks! There is no subwoofer. That bass bump is largely a result of the listening position being a foot from the wall, which location emphasizes 40 Hz 6+ dB. The Heresy’s are around two feet from the wall behind them. The Dayton Audio PA310-8 Ohm woofers are at least 2 or 3 dB more sensitive than the original Klipsch K 22 E (Eminence) 11 Ohm woofers - and much more athletic. When measuring the speakers in the middle of the room from a yard away that bass hump goes away and the tweeters’ response tilts upward significantly. The 3” long by 3” I. D port tube flattens the bass, moving its peak down in frequency. Picture that wide hump moving to the right almost an octave without the port. Dean, a lot of it is the room. Especially below 700 Hz. You both are right; I need to smooth bass response. I listen at moderately low volumes, and do not mind a bit of “loudness” curve. Though the graph shows a lot.

John, Thanks! There is no subwoofer. That bass bump is largely a result of the listening position being a foot from the wall, which location emphasizes 40 Hz 6+ dB. The Heresy’s are around two feet from the wall behind them. The Dayton Audio PA310-8 Ohm woofers are at least 2 or 3 dB more sensitive than the original Klipsch K 22 E (Eminence) 11 Ohm woofers - and much more athletic. When measuring the speakers in the middle of the room from a yard away that bass hump goes away and the tweeters’ response tilts upward significantly. The 3” long by 3” I. D port tube flattens the bass, moving its peak down in frequency. Picture that wide hump moving to the right almost an octave without the port. Dean, a lot of it is the room. Especially below 700 Hz. You both are right; I need to smooth bass response. I listen at moderately low volumes, and do not mind a bit of “loudness” curve. Though the graph shows a lot.

Antone Posted yesterday at 01:07 AM 🙂 1/3 octave RTA of pink noise: Measured at ear level at listening position approximately 9 ft from motor board: Dayton UMM6 Calibrated measurement mic with REW software: Followingthis schematic: 3” by 3” reflex port

🙂 1/3 octave RTA of pink noise: Measured at ear level at listening position approximately 9 ft from motor board: Dayton UMM6 Calibrated measurement mic with REW software: Following this schematic: 3” by 3” reflex port

001, Thanks for the info!

Pcbiz, Thank you, Sir.

Thanks for your interest. 🙂 The resistors for the L-pad were $5 each, and all the brass machine screws (6-32 at 1/4” long and 1 1/2” long) were a few dollars from the big orange hardware store. I already had a bunch of small poly caps to make the tweeter shunt. The most expensive parts in this experiment were the 16 muF Solen poly caps ($10.50 each). Th e L-pad sounds much better than the autotransformer in the original xover. I will not be going back to using the T2A. I think I will pass on the Furutechs for now, thanks just the same, Westcoastdrums ; ) The L-pad mod alone is only about $21 per speaker, and can be reversibly applied in any otherwise stock Heresy 1 ,1.5,or 2. In the Heresy 1, the squawker polarity may have to be uninverted because of its first order woofer xover. (Inverted in 1.5 and 2) The tweeter conversion took some effort involving attaching a screw-on adapter plate, so, maybe, wait to commit to that mod. Leave the stock tweeter and its xover alone until you have tried the L-pad mod and the woofer replacement. The biggest bang/buck mod is replacing that wimpy stock Klipsch woofer with the (now $130) Dayton Audio PA 310-8 12” pro woofer. Mechanically it is a drop in replacement. It is 3 or 4 dB per watt more efficient and works perfectly in the Heresy cabinet, especially if you replace the 1/2” thick rear panel (8 screws) with a cheap mdf panel and hole-saw out a hole in the lower corner for a 3” long by 3” inside diameter piece of white schedule 40 pvc pipe to tune the cabinet to around 40 Hz. Even without a cabinet port the Dayton woofer sounds much better than the original. Just get even a cheap($12.56)18-gauge 3.0 mH iron core inductor and a dirt cheap($1.04) 100volt 22 muF non polarized electrolytic cap (those components’ quality was good enough for Klipsch) to go with the Dayton woofer’s 8 ohm impedance when you install it, because the stock Klipsch woofer is around 11 ohms impedance, requiring too high an inductance and capacitance for the new woofer. The brass screws are not nearly as important as the drivers’ replacement, cabinet porting and crossover design, but cumulatively, this latest design is worth a try. You will definitely hear a large improvement. If you are handy, able to solder and can read my schematic (and a part$-expr3$$ catalog), why not try the L- pad first then the woofer then the tweeter and then air core inductors and poly caps last? The brass screws are cheap and can be done early on. With them alone you will not hear much difference. The woofer and porting mod you will definitely like. My earlier posts chronicle the mechanical aspects more. The later posts are circuit refinements via trial and error and extended listening tests. This latest mod with L-pad and brass screws is definitely the best sounding so far.

Thanks for the interest and the info, 001. 🙂 I saw “K-52H” actually stamped in ink on the squawker compression driver magnet structure. My Heresy’s were made in 1981. Does the K-55V work on the Heresy 700 Hz horn? I vaguely remember a discussion about another midrange horn lens going down to 600 Hz(?) Am I equivocating a K-55V with a larger (La Scala?) model’s squawker driver? Does BEC (Mr. Crites) sell these? Thanks again for actually reading my post. (It is a slog,I know;)

Watching Danny at GR Research has given me to want to try experimenting with replacing all ferrous components in the speaker signal signal path. I decided to replace with solid brass #6-32 machine screws all the original steel ones in the binding posts and internal barrier strip of each Heresy 1.5. I had replaced the iron cored woofer inductor with a Jantzen air core as of my last post. Although I had years before eliminated the need for the T2A autotransformer in the tweeter branch with a third-order, 7 kHz hi pass filter and a better (Eminence 1001 ASD) tweeter driver which was slightly less sensitive overall than the original K77, for the squawker I was still using the T2A for its 9-dB voltage reduction and eightfold impedance increase, thereby enabling the continued use of a 2-muF poly cap for the 16 ohm-squawker’s required 620-Hz hi-pass filter. Using high quality, low inductance 20-watt bifilar ceramic tube-core resistors I made a -9.8 dB L-pad (@15 ohms) to accomplish approximately the volume reduction that the T2A had yielded. Since an L pad (ideally) does not change the driver impedance it was necessary to increase the hi pass cap to 16 muF (@15ohms) for a 650 Hz squawker hi pass filter. My last post mentioned a 8.35 muF/ 9.1 ohm Zobel shunt across the squawker terminals to roll off (gently) its rising upper end. With the new L-pad I decided to omit the Zobel before measuring. Third-octave pink noise RTA measurements after all these circuit modifications showed a large improvement in overall midrange balance and in flatness from 600 Hz to 4000 Hz. Indeed the Zobel was no longer necessary. However, the tweeter now had a steeply rising high end above 13 kHz, and the L-pad’s lack of phase shift required inverting the squawker polarity, which in turn, required inverting the tweeter polarity, compared to my previous design. I bled off the tweeter rise (+5 dB at 20 kHz) with a 1.22 muF [16kHz] capacitance shunted across the tweeter terminals. This is by far the sweetest, best imaged and most transparent and neutral sound I have achieved with my Heresy’s.

So very sorry. I wasn’t following my thread. There is no elbow. Just a 3” long section of 3” ID schedule 40 PVC pipe. I just posted another tweak with a graph and pix today, November 10th, 2021.

20 Hz to 20 kHz Raw Room Measurement with Calibrated Measurement Mic of pink noise, third octave RTA. Horizontal graph lines are 5 dB apart. Mic at listening position 8.6 feet from speaker. Speaker cabinet 28” from rear wall, 22” from side wall. All upgrade parts available from an online speaker component supplier based near Dayton, Ohio.

Important Tweak to Worthwhile Heresy Tweak Less harshness at high volumes, sweeter clarity and more solid coherence achieved with reversing polarity of squawker to negative, resulting in 180 degrees relative to woofer and by reversing tweeter polarity to match woofer‘s (0 degrees) Small poly film and foil cap across tweeter flattens a spike at its upper end. Used to compensate for a small manufacturing discrepancy between left and right tweeters

In living this past year with the mods to my Heresy 1.5 for gravitas, scale and flat response (c.f. my last post), I discerned room for improvement. The lower treble still needed some smoothing, and the stereo image was unstable: moving my head quite slightly would sling the upper few octaves all over the place, and the left-right balance was never totally satisfying. (Bass was awesome, however.) The new drivers and cabinet porting had made huge improvements in the extremes of the audio band, but I wanted to try subtle changes to the crossover in order to fix smoothness and phase in the midrange and treble. I used the trial-and-error method with a real time analyzer, pink noise, and calibrated microphone while leaving the balancing network board external to the cabinet so as to see the results of crossover component value changes immediately in the response graph. Significant improvement was achieved by changing the tweeter section to a 7 kHz, 18 dB/octave high pass from last year’s 6kHz. This tipped up the response over 1.5 dB, contrasted to the previous x-over, from 15 kHz up to 20 kHz. This also made for less summing between the tweeter and squawker where their responses overlap. The squawker needed to have its top end slightly attenuated. I had been using the stock Klipsch configuration for the squawker, substituting a high quality poly film-and -foil capacitor of the stock 2 muF value for the original paper-in-oil can and continuing to use the number 2 tap on the T2A autotransformer. This works well to meld with the woofer but does nothing to calm the squawker’s upper end ( mortite on the horn has been tried by some on this forum for that), so I tried the easiest obvious thing, which was to shunt a capacitor across the squawker’s inputs. This is a way to knock highs off a driver’s upper end by essentially shorting only the highs to ground. The second order, low pass filter (which included a 33 muF cap added to the Heresy 1’s first order woofer crossover- i.e. just an inductor) that Klipsch used on the Heresy 1.5’s and 2’s woofer x-over is a handy case in point. Comparison of Klipsch’s schematics for the Heresy E and E2 crossovers indicates a phase difference introduced by the addition of the woofer cap, by way of the schematically notated inversion of polarity between the woofer and squawker in the Heresy 1’s E crossover (which inversion is absent in the Heresy 1.5’s and 2’s E2 crossover). Higher order phase difference will come into play later. The first value I tried in my squawker section was 18 muF, which sucked out too much low midrange. Trying successively smaller capacitor values, I arrived at near 5 muF in order to start attenuating high enough in the squawker’s range. RTA showed that the roll-off slope was a bit too steep, so I tried different audio grade resistors between the 5.1 muF cap and ground while watching the graph. Putting resistance between the 5.1 muF cap and the negative squawker input-i.e. signal ground-effectively reduces the overall amount of those particular highs allowed through the cap which get shorted to ground, shallowing the roll-off. Best results were obtained with the 9.1 ohm, 10W resistor I had in store. (A Mills non-inductive 12W resistor may be a better choice. ) Interestingly, the resistor’s insertion smoothed the bass response on the graph. The midrange response now is beautifully neutral, full and rich but never shrill; the treble is sweet, extended and clear. Another benefit of adding the cap to the squawker circuit is the phase shift (around 90 degrees ) that it contributes to the squawker, making it blend more coherently with the other drivers. The stereo image is solid, the soundstage stable, with instruments startlingly precisely located. Channel balance is now rock steady with no stereo wandering. Placed 2 feet from front wall, no subwoofers are necessary or wanted. Schematic for this latest and greatest mod is included. Drivers specified on this schematic and in my previous post are easily available online. Porting dimensions and woofer crossover values remain as per my previous post. These Heresy’s sound big, accurate and serious. Gravitas, exciting scale, powerful bass, beguiling mids, crystalline highs and imaging. Happy listening.

Yes , billybob, There are some major differences this time. I port -tuned the enclosure to 50 Hz, lowering F3 by around 20 Hz-no port previously. I chose this latest driver based on its compatibility with the Heresy cabinet, heeding T/S parameters. My previous woofer, Dayton series 2, was 4 dB less efficient and made for a much larger box. My graphs show flatness I could hardly achieve with a 31-band EQ before-no EQ needed now. Consider my posts from years ago superseded. This upgrade is based on much greater experience and measuring instrumentation I did not have before.

Still learning. 🥴 Telling the truth about the results and thought process, though. This upgrade is relatively cheap and easy, and the graphs are much better than stock. I wanted to share my modest success.

Thanks, glens,😁 I put that badly. I just wanted both crossovers as equal as possible. 😬😉

Thanks, carlthess40, I am no carpenter, just a professional symphony musician who likes to fix things and solder. The ports are not pretty, but they work fabulously. The xover I hardwired point to point with 18 gauge solid and stranded wires, keeping the lengths between the two xovers the same, so that both speakers’ signal paths were equal in length.

Hi, This last upgrade with the Dayton Audio PA 310-8 woofers is by far the best I have found. I just posted graphs and the xover schematic a few minutes ago under the same topic title. My previous upgrades were judged by ear with little knowledge of xover circuits, T/S parameters or proper test equipment. Take a look at this latest post from noon- ish July 27th.

Here are the RTA and Spectrum Analysis Graphs of the measurements resulting from the modifications described in the first post in this thread. Bear in mind that these readings were not taken in an anechoic chamber or outdoors, but in my listening room, well away from the walls.. All horizontal graph lines are 5 dB apart. These graphs have not been edited. These measurements were taken at less than a Watt of drive power. The Dayton Audio UMM 6 measurement mic and REW software were used on a Toshiba Windows 7 laptop computer. At 2.83 Volts of pink noise the result- not shown here- was 101 dB at 3 feet, 100.4 dB at 1 meter. The first two graphs are RTA of pink noise at 3 feet, with 1-octave smoothing on the first graph and with one third octave-smoothing on the second graph. The third graph is spectrum analysis of white noise, with psychoacoustic smoothing. The final graph shows pink noise RTA with one octave smoothing, locating the mic at the listening position. The crossover schematic responsible for these results is included.

I have discovered an easy formula for addressing the two largest problems with the sound of my beloved 1981 Heresy 1.5's (Heresy 1 drivers with the E2 balancing network). The K22-E woofer is not efficient enough to balance the squawker, even with the 9 dB attenuation via the T2A autotransformer. The enclosure contains only 1.6 cubic feet-before subtracting the drivers' and crossover's respective displacements. These limiting factors are familiar to most of you. I have achieved a vast improvement in frequency response, rhythmic drive, listenability and flexibility of room placement by changing-reversibly-only a few things. Bonus: 4dB increase in sensitivity over stock (96 dB/W @ 3 ft) to 100+ dB/W @ 1 m. I sought long and hard a 12" woofer with an efficiency of at least 96 dB/W (2 dB/W more than the Klipsch woofer) that possessed Thiele-Small parameters appropriate for a small, ported enclosure. (Running computer simulations for the Heresy's 1.5 cu.ft.of useable volume, I quickly discovered that physics will limit the extension of unported cabinets to a 3 dB down point (F3) around 70 Hz, regardless of any woofers I can fit.) I found two worthy candidates in the professional sound reinforcement category. The two readily and cheaply available candidates were the Peavey Sheffield Pro 1200+ and the Dayton Audio PA 310-8 12" woofers. My free speaker box calculator app showed that the Dayton woofer ($60 each) yielded the better maximum flat bass amplitude of these two 96 dB/W-candidates. Since I will not damage my one-owner vintage Klipsches (got them brand new in 1982), I bought a half-sheet of 1/2" thick MDF to make a new, port-friendly back panel for the Heresy cabinet and a short length of 3" diameter white PVC pipe along with a 3 1/2" hole saw at the hardware store. I just traced the original back panel and transferred the screw holes onto the MDF. Good measurements and at least a circular saw will give you better results. The box calculator app indicated that a 3" long tube of 3" inside diameter would tune the cabinet to 50 Hz to produce the lowest F3 possible with these woofers: 56.7 Hz. I know that does not seem great, but keep in mind that the simulator app showed the factory woofer's unported F3 at above 70 Hz, plus it was too quiet to balance the squawker and cannot play as loud as the 450 W- capable PA 310-8. You seeing where the "Scale and Gravitas" come in? I installed with hot glue the 3" I.D. by 3"long tubes in the lower outer corners of the MDF panel where the pipe would not foul anything (e.g. wooden cleats) inside the box. Since this new, much beefier woofer has a nominal 8 Ohm impedance instead of the Klipsch woofer's 11 Ohms, I modified the values of L2 and C2 in the Klipsch 'Balancing Network' (crossover) 12 dB/octave woofer low-pass section to achieve the smoothest transition to the squawker. Measurements with pink noise, a calibrated measurement microphone and RTA program led me to a standard second order 600 Hz low pass circuit for 8 Ohms,. That is, I merely changed the original woofer inductor L2 from 4 mH to 3.00 mH ( by unwinding some coils and measuring with an LC meter) and replaced C2, originally 33 muF, to 23.4 muF (a 22muF bipolar 100-Volt electrolytic in parallel with small value poly caps to sum to 23.4 muF). I left the squawker section totally stock, except for replacing the spam can 2 muF squawker capacitor (connected to T2A terminal 5) with a polypropylene Jantzen of the same value. The woofer now smoothly and powerfully balances that magic midrange horn. The speaker can now be placed a couple feet from the wall and still have much better bass than ever. With the Eminence ASD 1001 titanium tweeter driver screwed onto the factory tweeter horn [phase plug removed] with an adapter plate, described in my earlier posts, I measured very flat response from 50 Hz to 19 kHz +/- 2.8 dB ,with 1-octave smoothing; 101 dB SPL at 3 feet with 2.83 V pink noise in a medium sized, carpeted room. The room actually created a modest bass hump to make 40 Hz quite audible ( with the speakers over two feet from the back wall! ). I found that a third order 18 dB/octave high pass circuit at 6 kHz (8 Ohm), without going through the T2A at all, works wonderfully with the ASD 1001 and K52H squawker to prevent that deadly upper midrange hump, combined with the anemic bass, which made the stock Heresy's notorious, especially on denser sonic textures - and right hand piano notes should not honk. Only a narrow 1.5 dB hump at 1.2 kHz and a shallow 1.6 dB depression between 400 and 800 Hz and no spikes anywhere. This is the way I have always wished they had sounded. Bigger, smoother, sweeter.

Dear Fellow Klipsch Fans, It has been several years since my original post concerning my Heresy upgrade to achieve smooth midrange, better imaging, and low end slam. I have learned some things since then in living with the mods, researching circuits and, lately, measuring sound. For someone with, at that time, few measuring instruments and so little experience and training in speaker design, I succeeded in voicing my Heresy II's in the right direction for my listening room and the speakers' vertical placement (I had put them on 16" high stands about 16" from each wall in the corners, more later about why this placement was not a good idea). I still believe that polypropylene caps sound better (less harsh) than the original paper-in- oil Aerovox caps; I have yet to measure this however, so I will not be dogmatic, yet. And I am positive that I prefer a poly cap to the electrolytic (33muF woofer) ) that my Heresy's sported from the factory, but they were almost 30 years old (hmmm. . . ) when I replaced them. At the time of my OP I had just discovered poly caps and was quite enthusiastic about them. I mean-I did not think that I should stick each lead of a poly film- and- tin foil cap in either nostril while listening (Nichicon Fine Gold or Elna Silmic II electrolytic with negative lead in left nostril? Hm, probably should use a Nichicon Muse Bipolar. . . ), but better circuit design and speaker placement seem more important. I recently acquired a calibrated measurement microphone (modest, but more precise than my ears) and downloaded some free RTA and room simulation software and decided to experiment with my half-baked, cobbled-together, yet expensive (700W, $50 woofer low-pass coil?) crossover. I have found a cheaper, less invasive, and measurably better modification with remarkable results. The treble and upper midrange are sweet, smooth, and pleasing and blend together seamlessly. Those of you who use mortite on the squawker horns may have been trying for this. The speakers project more like stock , they are more efficient than my previous mod., now 93 dB 2.83 V at I yard @ 1 kHz. The stereo image has depth now as well as width. You can use the original spam can caps if they are still good, but for the woofers, at least buy two 33muF, 100 Volt, Non-Polarized (Bi-Polar) electrolytics if yours are over 20 years old; they are cheap: a buck or two each. Metallized poly propylene 30 muF, 250 Volt caps are available for around $10 each last time I looked. I still like the Eminence ASD 1001 [see my RTA room response of them below] titanium compression drivers I specified in my OP for the tweeters, the four-bolt horns of which need the screw-on adapter plates mentioned in my OP. I cut the phase plugs out of my tweeter horns, but I would try them un-cut.. The Dayton Series II 12" 8-Ohm woofers work well in reproducing down to 30 Hz and their 92 dB sensitivity works with the Klipsch factory squawkers (the best part of the Heresy, IMO); although the -12 dB terminal (#1) of theT2A autoformer needs to be used on the squawker positive instead of terminal #2 on T2A (-9dB) to match output volumes. I checked all three driver relative volumes with calibrated mic and RTA and pink noise source. Also the Eminence tweeter's 2 muF cap needs to be connected directly to the input, completely bypassing the autoformer, whose terminal #3 (-6 dB) originally went to the cap and then from there to tweeter negative, because with my second-order tweeter crossover's smoother transition to the squawker no attenuation is needed to match the squawker output. I leave the woofer crossover totally stock, move the squawker positive to T2A's terminal #1 from T2A's terminal #2, but otherwise leave the squawker crossover alone, bypass T2A entirely for the tweeter, add a 0.25 mH coil across the tweeter terminals to make a 12 dB per octave, 7 kHz high pass filter out of the factory 6 dB/ octave crossover. Also I connect the tweeter in phase with the other two drivers instead of the factory's reverse polarity. Look how flat that tweeter respose is; it goes to almost 19 kHz according to spectrum analysis on white noise, in this room. This curve is of the driver without crossover installed yet. The RTA on pink noise is at 1 octave resolution. Below is a schematic showing the schematic with changes. I put the speakers back on their angled plinths all the way in the corners to avoid midbass suckout at 250 Hz shown in RTA woofer response attached below. The stands I was using and speaker distance from the corners in my listening room dimensions are culprits, since the factory curve for these Dayton woofers shows no such suckout and the crossover does not affect frequencies below 500 Hz. As you can see they go down to 30 Hz very well with no porting necessary. On stands or on the floor, the very bottom octave was little affected. It was the mid bass third octave that was killed by being on the stands. The room simulation software predicted this for my room dimensions, by the way. My previous mod added much mid bass and had a couple large humps across the spectrum, making up perhaps for my misguided use of 16" high stands. More Later. Antone Heresy Crossover.pdf tweeter curve Woofer room response ST305-8_fr.pdf

INTRIGUING. THANKS

ClaudeJ1 wrote:"I think LaScalas with twin tapped horn sub(s) is a huge improvement over a Khorn. for over 30 years (I was still a "kid" when it began), I had 2 Khorns with a mono LaScala in the middle, just like PWK's setup at home, which I heard, and it sound any different from mine, even though he had a Belle. What I have now is way better. The Roy Delgado's K-402 Mid horn STOMPS everything I have ever owned and heard out there, and that has been quite a few things in the last 6 years." ClaudeJ1' What are twin-tapped subs? Are the K-402 squawkers too big for a Heresy motor board?

Sounds like a good idea, if you have the parts. Go for it.

Hello Again Fellow Klipsch Fans, It has been awhile, and I've learned a few things since my last post. I now understand what an autoformer is and how a capacitor across the inputs to a driver increases its upper-end roll-off. With a little more knowledge I've found some different mods to smooth and to refine the voicing of my beloved Heresy's. The most important one is to use the built-in flexibility of the original T2A autoformer to bring the squawker output down 3 dB overall from stock by unsoldering the lead from terminal 2 and moving it to terminal 1 of the T2A autoformer. I love the way the K-52 H driver and horn handle the midrange; there is just a little too much of it. This mod nicely remedies this. If you'll remember, for the tweeter driver I specified the Eminence ASD-1001S titanium-domed driver [8 Ohm, screw-on] with the Selenium screw-on to 3-bolt adapter plate {#ADF25-25}; you will need to mark and drill holes to match the original K-77M Horn's 4-hole bolt pattern and to buy long brass 8-32 bolts to attach it. Trim the plastic adapter plate's flange with a hacksaw ( after drilling and before attaching, of course), and the whole assembly will fit well. This driver has a much better frequency response curve (out to 20kHz), but it is a little less sensitive than the stock phenolic-domed driver, so it gets a 3 dB overall boost by unsoldering the lead from terminal 3 and moving it to terminal 4 of the T2A autoformer. In order to smooth the transition between the tweeter and and the squawker I recommend two things: to change the tweeter high-pass capacitor from 2 muF to 1.8 muF (this makes a huge difference in sibilants' harshness), and to add a roll-off cap across the squawker driver inputs of around 0.43 muF. Polypropylene film and foil sound best, but metallized polypropylenes are cheaper and pretty good (both of these types are more precisely tolerated and won't go bad in twenty years like electrolytics!) . Capacitances add in parallel, so you can achieve 0.43 muF with a 0.33 muF and a 0.1 muF poly film-and-foil cap in parallel. I still believe that a 2 muF polypropylene film-and-foil cap is best for the squawker high pass cap (between INPUT + and terminal 5 of the T2A autoformer) With lowering the squawker output by 3 dB as mentioned in the first paragraph, I do not need to be so dogmatic as before about the Direct Current Resistance of the woofer low-pass inductor. So, I can now recommend a (much cheaper) 16- gauge "Super Q" inductor with an inductance of 3.5 mH and DCR of 0.200 Ohm (parts-express #266-916). Of course, this inductor is for my recommended, MUCH-better Dayton Audio Series II ST 305-8 12" drop-in replacement woofers. BTW, they do reproduce 30 Hz QUITE well; I used a 30 Hz test tone to confirm this fact. I still like a 33 muF metallized polypropylene cap across the the woofer inputs to roll off its upper end; although, I believe there may be room to fiddle with that a bit for smooth transition between the replacement woofer and the squawker. Also, I wonder if 1.7 muF might be an even better value for the tweeter high-pass cap. Happy Listening!