Crossover Starting Points by Speaker Size: A Quick-Reference Chart for Subs, Doors and Tweeters
Paul Galanos |
12 Volt Encyclopedia Volume VIII
Quick answer: start subs and door speakers at 80 Hz, then adjust by ear
For most systems, a high-pass of about 80 Hz on the door speakers and a low-pass of about 80 Hz on the subwoofer is a safe first setting. Smaller speakers need a higher high-pass, and tweeters should never be crossed lower than the manufacturer allows. Use this chart as a starting point, not a final tune.
1
Where each speaker plays
Every speaker has a range where it plays cleanly. A crossover keeps each driver inside that range, so bass goes to the sub, midbass to the doors and detail to the tweeters. The yellow lines show common starting crossover points.
Why 80 Hz?Around 80 Hz, bass is hard to locate by ear, so the sub can sit in the trunk while the sound still seems to come from the front. It also keeps heavy bass excursion away from door speakers.
2
Starting points by speaker size
These are first settings for typical aftermarket speakers on an amplifier, head unit or DSP crossover. Always check the speaker's spec sheet first.
Speaker
Typical location
Starting filter
Usable range
Notes
Subwoofer 8–15 in.
Trunk, cargo, under seat
Low-pass 80 Hz
60–100 Hz
Raise toward 100–120 Hz if your door speakers are small. Set the subsonic filter for your box type (see Box Buddy).
6.5 in. / 6.75 in. midbass or coaxial
Front or rear doors
High-pass 80 Hz
60–100 Hz
A well-sealed, deadened door may let you go a little lower.
6x9 in. coaxial
Rear deck, some doors
High-pass 80 Hz
60–100 Hz
There is no fixed rule; tune by ear for clean bass without distortion.
5.25 in.
Doors, kick panels
High-pass 100 Hz
80–150 Hz
Small cones run out of excursion quickly; go higher if you hear strain.
4 in. / 4x6 in.
Dash, rear doors
High-pass 120 Hz
100–150 Hz
Pair with a sub low-pass of about 100–120 Hz to close the gap.
3.5 in. dash speaker
Dash corners, center
High-pass 150 Hz
150 Hz and up
Check the spec sheet; many need 150 Hz or higher.
3–4 in. midrange (3-way)
Dash, A-pillar, door
Band-pass 500 Hz – 5 kHz
Per spec sheet
Used only in active 3-way setups.
Tweeter (active)
Sail panel, A-pillar, dash
High-pass 5 kHz
3.5 kHz and up
Never cross below the maker's minimum. A common rule of thumb is about twice the tweeter's resonance (Fs). Use 24 dB/oct.
Protect your tweetersOn an active tweeter channel, a missing or too-low high-pass filter can destroy the tweeter in seconds. Set the filter before you turn up the volume.
3
Pick your system type
Choose the setup closest to yours to see a full starting map. These settings assume speakers of at least 5.25 in.
Quick answer: test under load, with one lead at each end of the same wire
A voltage drop test shows the voltage being lost across a wire or connection while current flows. Put the red lead on one end of a wire and the black lead on the other, play loud bass, and read the meter. Aim for 0.5 V or less across the whole power side, 0.2 V or less across the ground side, and 0.1 V or less across any single connection.
1
Why a normal voltage check isn't enough
Measuring battery voltage at rest shows about 12.6 V even with a bad connection, because almost no current is flowing. Resistance only shows up as lost voltage when current flows, so test with the system playing loud bass or with a heavy load on.
Meter setupSet the meter to DC volts (a low range or auto-range). Use long test leads or a jumper so you can reach both ends of a power run.
2
Run the tests in this order
Test A, power side: red lead on the battery + post (on the post itself, not the clamp), black lead on the amp's +12 V terminal. Play loud bass and read.
Test B, ground side: red lead on the amp ground terminal, black lead on the battery − post. Play loud bass and read.
Split the bad side into sections. Measure across each connection one at a time: post to clamp, across the fuse holder, across the distribution block, lug to wire.
Test the charging path (Big 3) with the engine running and a load on: alternator B+ stud to battery + post, then engine block to battery − post.
Fix the worst reading first and retest. One corroded clamp or loose set screw can account for most of the loss.
Across a fuse holder: anything above about 0.1 V means a loose set screw, corrosion or an undersized holder.
3
What the readings mean
Test
Good
Acceptable
Fix it
Power wire: battery + post to amp +12 V terminal
≤ 0.3 V
0.3–0.5 V
Above 0.5 V
Ground: amp ground terminal to battery − post
≤ 0.1 V
0.1–0.2 V
Above 0.2 V
Across one fuse holder or one connection
≤ 0.05 V
0.05–0.1 V
Above 0.1 V
Alternator B+ stud to battery + post (engine running)
≤ 0.2 V
0.2–0.3 V
Above 0.3 V
Engine block to battery − post (engine running)
≤ 0.1 V
0.1–0.2 V
Above 0.2 V
Check your readings
Enter your readings in volts, taken with the system playing loud bass (or the engine running for the charging tests).
4
Common causes of high readings
Where the loss is
Usual cause
Fix
Battery post to clamp
Corrosion, loose clamp, stacked ring terminals
Clean the post, use a proper clamp or terminal block
Fuse holder
Loose set screws, oxidized fuse, undersized holder
Retighten, replace the fuse or upgrade to ANL or MANL
Along the wire
Undersized wire, copper-clad aluminum, long run
Upgrade gauge or switch to OFC copper
Amp ground
Paint under the lug, long ground, seat bolt
Sand to bare metal, shorten the run, match the power wire size
Charging path
Small factory alternator or ground cables
Big 3 upgrade
Disconnect before you fixDisconnect the battery negative before loosening power connections, and keep the main fuse within about 7 in. of the battery.
