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Multi-Way Conventional loudspeakers with crossovers

wiring parallel or series sensitivity rules?
wiring parallel or series sensitivity rules?
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Old 12th January 2018, 11:50 PM   #81
BlueWizard is offline BlueWizard  United States
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Quote:
Originally Posted by AllenB View Post
What are these limits?
You can cut out notches but you can't boost. Or to put it another way, you can notch out peaks, but you can't boost notches.

Steve/bluewizard
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Old 13th January 2018, 02:16 AM   #82
AllenB is offline AllenB  Australia
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I wouldn't agree, I often fill holes with passive networks.
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Old 13th January 2018, 10:54 PM   #83
Dryseals is offline Dryseals  United States
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Lots of info here but still not sure where I am.

Just purchased four 8" speakers (woofers), 4 ohm with a 92.9 DB sensitivity at 2.83/1M. Planned on doing two in series for each speaker for an 8 ohm load to the amp.

This is a three way design. The midrange is an 8 ohm with 89.4 DB sensitivity at 2.83/1M. The tweeter is 8 ohm 94 DB sensitivity at 2.83/1M, so I figured I would have to pad down the tweeter and I could equalize in the midrange as I suspect with two woofer in series for an 8 ohm load that I would be knocking 3 db off the sensitivity at 2.83/1M. leaving me with a combined 89.9 sensitivity.

Guess I'll find out soon enough, just purchased the latest version of Sound Easy as my older parallel port key version was not working right any more.

I'm just hoping I didn't screw up on the purchase.
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Old 14th January 2018, 05:12 AM   #84
ScottG is offline ScottG  United States
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Both the tweeter and the midrange will need "suppression" - assuming the need for baffle-step compensation and a reasonably typical design/baffle for the mid.. (..it's not a screw-up though, it just means a more complex filter design.)
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Last edited by ScottG; 14th January 2018 at 05:14 AM.
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Old 14th January 2018, 10:05 AM   #85
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Dryseals View Post
Lots of info here but still not sure where I am.

Just purchased four 8" speakers (woofers), 4 ohm with a 92.9 DB sensitivity at 2.83/1M. Planned on doing two in series for each speaker for an 8 ohm load to the amp.

This is a three way design. The midrange is an 8 ohm with 89.4 DB sensitivity at 2.83/1M. The tweeter is 8 ohm 94 DB sensitivity at 2.83/1M, so I figured I would have to pad down the tweeter and I could equalize in the midrange as I suspect with two woofer in series for an 8 ohm load that I would be knocking 3 db off the sensitivity at 2.83/1M. leaving me with a combined 89.9 sensitivity.

Guess I'll find out soon enough, just purchased the latest version of Sound Easy as my older parallel port key version was not working right any more.

I'm just hoping I didn't screw up on the purchase.
Your 4ohms bass speakers are rated as 92.9dB/2.83V @ 1m
That is equivalent to 92.9dB/2W @ 1m and that equals 89.9dB/W @ 1m
Now put them in series so that each receives 1/2W, then each will output 86.9dB/1/2W @ 1m
But you have two of them getting you back to 1W into the pair giving a total output of 89.9dB/W @ 1m
In addition, over the frequency range where they are considered to be coupled, you get upto 3dB more output. So at low frequencies you have 92.9dB/W @ 1m and above the coupled range you have 89.9dB/W @ 1m
Unfortunately the pair will have some beaming due to the null and peak of the interference patterns. That beam will also have the same +3dB when the two drivers are pointing directly at the listener, or measuring mic.
You may need somewhere between +3dB and +6dB to take account of the loss due to a small baffle (Pi/4 loading instead of Pi/2 loading that all manufacturers use).

Bass = 89.9dB/W ranging up to 92.9dB/W
Mid = 89.4dB/W
Treble = 94dB/W

The only speaker that will not need padding is the Mid.
The extra sensitivity of the Bass already makes up for some, or most of the baffle step loss. Get this tuned in and you may find the final Bass response/sensitivity equals the Mid driver.
Both the Treble and the Bass will need some padding down (or use dedicated amplifiers with adjustable sensitivity).
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Old 14th January 2018, 06:32 PM   #86
BlueWizard is offline BlueWizard  United States
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Quote:
Originally Posted by ScottG View Post
Both the tweeter and the midrange will need "suppression" - assuming the need for baffle-step compensation and a reasonably typical design/baffle for the mid.. (..it's not a screw-up though, it just means a more complex filter design.)

With smaller drivers (meaning not 10", not 12', not 15") and modern narrow cabinets, if the crossover is chosen wisely it can be below the baffle step.

For example, using 8" drivers and assuming a 10" Wide baffle, the step frequency will be 456hz (roughly). If you are using a Low/Mid crossover in the roughly 300hz range, Baffle Step is not really a problem for the low-bass.

Though a bit more complex than this, you can get an estimate by this formula -

F = 380 / Bw

Where -

F = the baffle step frequency
380 = a constant derived from solving a more complex equation
Bw = Baffle Width in FEET


An alternative to Crossover Baffle Step correction, which usually involve reducing the woofer above the Baffle Step, you can boost the bass output by using a Half-Way system.

Adding a second identical driver running in parallel with the main bass driver but only covering the range for the lowest frequency up to the Baffle Step.

Click the image to open in full size.

This image was created for another purpose, but in this case, we would assume the Baffle Step was around 200hz.

Steve/bluewizard
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