4500Hz Network Builder

An independent builder's tool for 4500 Hz crossover work on classic Klipsch-style three-way horn-loaded speakers and compatible networks.

STEP 1

Factory Reference

Choose the speaker and factory network first. A network is enabled when it has its own verified reference or a documented shared reference; incomplete references stay disabled until their data is imported.
4500X CONVERSION
Use a capable replacement tweeter at 4500 Hz, pad it to match the midrange, and keep the squawker / HF branch arrival behavior from 250 Hz upward as close to factory as practical - especially in the critical 250-700 Hz woofer crossover region.
Factory elementsWoofer: K-22 familyMidrange: K-55-V / K-55 familyTweeter: K-77 / K-77-MSystem: 8 Ω nominalLower entry: 700 HzBasis: L1 2.5 mH / C2 2 µFVerified electrical reference: Heresy I Type E
Proposed changeNew tweeter: Celestion CDX1-1412Load: 8 ΩTarget: 4500 Hz handoffHF parts sized from the selected span loadWiring sheet generated from the selected build
STEP 2

Proposed 4500X Setup

Select only parts with complete impedance and span data. The app keeps one shared autoformer input span and disables incomplete candidates.
BUILD OPTIONS
Choose whether span selection protects the squawker SPL target first or lets the HF arrival score choose first. C2 is still scaled to preserve the factory squawker high-pass.
4500X uses the verified CDX1-1412 impedance curve, not a nominal 8 ohm load. That impedance behavior is why this is not a simple first-order 4500 Hz conversion.
SQ 0-5 to 0-2TW 0-5 to 0-2Common Tap 0R1 Tap 5 - Tap 0
T2A only has 3 dB output steps. The app lands on the nearest available tap when the requested target falls between taps.
TARGETS & VOICING
Set the midrange/HF arrival first. This is the factory behavior the app keeps close in the 250-700 Hz match window.
Then trim the replacement tweeter relative to the midrange. The app picks the tweeter tap separately; C2 remains a squawker high-pass match to the factory network.
SQ / HF arrivalFactory -10 dBTarget -10 dBat factory target
TW / midrangeFactory relationship -1 dBTarget -9 dB totalat factory target
BUILD ANSWER
What to build firstOpen the Wiring tab for the bench connection diagram.
Needs review
HF Arrival: Needs reviewC2 Load: OKVoicing: On target
Match Window: 250-700 HzFactory Match: 70%RMS Magnitude: 2.8 dBRMS Phase: 51.7°
Recommended next stepReview before building

Keep the squawker target as the anchor. Try the adjacent span or compare no R1 against the selected R1 in C2 view, then use the Wiring tab only after the graph and C2 load look intentional.

CONNECT
T2AInput 0-5, squawker 0-2, tweeter 0-2, common Tap 0
INSTALL
C2 2 µFNo R1; no Lx4500X SQ/TW parts in Wiring
CHECKFactory-like is close to the stored reference. Review means inspect the graph and values before building. Needs review means compare one alternate before treating the build as ready.
Needs reviewHF arrival Needs review; C2 / Load OKSQ 1.0 dB hot; TW on target. Main score: 250-700 Hz.
C2 / SPAN LOADC2 is the cap feeding the autoformer; its value follows the effective load at the selected input span.
Choose no R1 or an R1/shunt-Lx row, then compare the C2 load view before building.
App pick no R163.5 Ω reflected96.0 Ω at AF input1.87 µF C2 start2 µF closest2 µF next upNo LxR1 not installed2.00 µF factory C2
R1LoadCalculatedClosestNext upLx parallel
Span load optionsEach row is a complete load condition. No R1 uses C2 alone; an R1 row uses the listed C2 and shunt Lx together.
Driver impedance checkK55 curve + CDX1-1412 on new 77 lens at the 700 Hz factory-match window. This verifies that the proposed C2 preserves the factory squawker high-pass behavior; acoustic SPL still depends on driver sensitivity and measurements.
96.0 Ω impedance-curve load1.87 µF factory-equivalent C27% vs selected capimpedance check close
ONE AUTOFORMER INPUT SPANThe squawker and tweeter use different output taps, but they must share one physical input span.
The midrange and tweeter share one physical autoformer input span. The app changes span only to improve attenuation match: squawker first, tweeter second. If the span changes, both drivers move to the new span and each gets the nearest available output tap there. T2A only has 3 dB output steps. The app lands on the nearest available tap when the requested target falls between taps.
MIDRANGE OUTPUT TAP
Target -10 dB on shared span 0-5.
AttenOutputRef ZChoice
TWEETER OUTPUT TAP / C2
Target -9 dB on shared span 0-5. C2 follows the effective impedance at the autoformer input, so output tap changes matter through the load they reflect back to that input.
AttenOutputNo R110Ω15ΩChoice
STEP 3

Stud Finder Results

Review how the proposed taps, C2, and R1 compare with the factory electrical behavior before treating the build as ready.
FACTORY COMPARISON
Heresy I Type E HF Arrival Match: Needs reviewweighted from 250 Hz upward
The proposed HF arrival is materially different from the Type E reference in the 250-700 Hz region.
2.8 dB RMS mag51.7° RMS phase11 transfer samples
PRIMARY CHECKHF arrival is the level, slope, and phase relationship as the squawker reaches the woofer crossover region.
HF arrival Needs review
RMS magnitude2.8 dB
Max magnitude6.2 dB
RMS phase51.7°
Max phase120.4°
SUPPORTING CHECK
C2 / Load OK
Factory C2 load89.7 Ω
Selected load96.0 Ω
Factory delta+7%
Nearest C22 µF
VOICING CHECK
TW on target
SQ target-10 dB
SQ actual-9.0 dB
TW target-9 dB
TW actual-9.0 dB
R1C2 checkC2 loadFrom factoryC2Flag
FACTORY VS 4500X HF ARRIVAL — 250-700 HZ
Read this asorange is the factory squawker reference; blue is the proposed squawker path. Closer overlap means the HF branch is arriving more like factory in the woofer crossover region.
Needs review2.8 dB RMS shape, 51.7° RMS phase
4500 Hz takeoverThe replacement tweeter is judged at the 4500 Hz handoff against the squawker target. The factory-match score weights 250-700 Hz most, then uses lighter upper-squawker context toward 3000 Hz.
OVERLAY TRACE, LOG FREQUENCY / OCTAVE SPACING
Proposed trace: T2A, input 0-5, SQ 0-2, TW 0-2, No R1
3 dB0 dB-7 dB-16 dB250 Hz315 Hz400 Hz500 Hz630 Hz700 Hzuseful match windowmost important arrivalFactory 250 Hz: -6.5 dB vs 700 Hz arrivalFactory 315 Hz: -5.6 dB vs 700 Hz arrivalFactory 400 Hz: -1.7 dB vs 700 Hz arrivalFactory 500 Hz: -2.2 dB vs 700 Hz arrivalFactory 630 Hz: -1.1 dB vs 700 Hz arrivalFactory 700 Hz: 0.0 dB vs 700 Hz arrivalProposed 250 Hz: -12.7 dB vs 700 Hz arrivalProposed 315 Hz: -8.9 dB vs 700 Hz arrivalProposed 400 Hz: -2.2 dB vs 700 Hz arrivalProposed 500 Hz: -4.1 dB vs 700 Hz arrivalProposed 630 Hz: -1.8 dB vs 700 Hz arrivalProposed 700 Hz: 0.0 dB vs 700 Hz arrival
This check compares the stored Heresy I Type E squawker reference against the proposed 4500X squawker path. The primary matching region starts at 250 Hz; differences below 250 Hz are not used for the verdict. Both traces are anchored at 700 Hz to show how the HF branch arrives into the woofer crossover region.
Needs review means compare one alternate before treating the build as ready. Use the graph, C2 view, and bench measurements to decide whether the shift is acceptable.
HERESY I / TYPE E
verified driver data · 1967-1985, with late transition variants · K-22 family / K-55-V / K-55 family / K-77 / K-77-M
Source notes

The factory spec is an 8 ohm system with K-22/K-55/K-77 parts. The Type E Stud Finder model uses the in-cabinet K-22 reference curve, represented near the woofer crossover as about 11 ohms. Factory baseline is Heresy I Type E: C2 2uF before the autoformer, no woofer shunt cap C1, T2A 0-5 input, K55 path 0-5 -> 0-2, K77 path 0-5 -> 0-3. Proposed 4500X tweeter branch uses C4a 4uF / L4 0.16mH / C4b 6.8uF; proposed squawker shaping uses L2 0.510mH / L3 0.510mH / C3 1.5uF. C2 always feeds the autoformer and is chosen from the effective impedance seen at the autoformer input, not from the tweeter 4500Hz high-pass.

System 8 Ω nominalWoofer ref near XO 11 ΩVerified Heresy I Type E electrical referenceSQ target -10 dBTW target -9 dBLower XO 700 Hz2.00 µF factory C2T2A T2A 0-5K55 0-5 -> 0-2 / normal polarityK77 0-5 -> 0-34500X TW 4 µF / 0.16 mH / 6.8 µF4500X SQ 0.51 mH / 0.51 mH / 1.5 µFLoads W/SQ/TW 4/8 / 14.5 / 8 Ω
AMP & OUTPUT CHECK
These values do not choose the tap. They show expected voltage, power, and load once the taps are selected.
W
T2A — 0-5 SPAN, 3 DB STEPS
CONNECTIONTURNS RATIOATTEN (DB)Z MULTREFLECTED ZOUTPUT VOUTPUT WC2C2 + 10Ω R1C2 + 15Ω R1SPAN LDCR (Ω)R1 SPANNOTE
Tap 5 -> Tap 51.00000.0 dB1.000×8.0 Ω20.00 V50.00 W22.43 µF51.16 µF43.58 µF55.694 mH12.0800Tap 5 - Tap 0T2A 0-5 full input span
Tap 5 -> Tap 40.7079-3.0 dB1.995×16.0 Ω14.16 V25.06 W11.24 µF36.98 µF29.40 µF26.570 mH3.4470Tap 5 - Tap 0T2A 0-4 output span
Tap 5 -> Tap 30.5012-6.0 dB3.981×31.8 Ω10.02 V12.56 W5.63 µF29.88 µF22.30 µF14.620 mH2.4020Tap 5 - Tap 0T2A 0-3 output span
Tap 5 -> Tap 20.3548-9.0 dB7.943×63.5 Ω7.10 V6.29 W2.82 µF26.31 µF18.74 µF7.323 mH0.8895Tap 5 - Tap 0T2A 0-2 output span
Tap 5 -> Tap 10.2512-12.0 dB15.849×126.8 Ω5.02 V3.15 W1.41 µF24.53 µF16.95 µF3.520 mH0.3389Tap 5 - Tap 0T2A 0-1 output span
AMP VOLTAGE
20.0 V
50W into 8Ω
AMP POWER
50 W
8Ω load
TWEETER Z
8 Ω
selected HF load
C2 BASIS
700
Hz factory-match window