I installed an 8 ohm L-pad on the B&C DE-250/2226J left channel and couldn't find a setting that mated with the right. The L-pad channel sounded crisper and maybe 'brighter'. Figured the difference was the .33 cap so I clipped it. Now I could balance the sound of the left, L-pad and right 24ohm fixed speakers.

First confoosion: what accounts for the large discrepancy between the attenuation values of this guys chart: 5.47 R1 and 3.7 R2 and yours: 24ohm R1 and 16ohm R2 for 10dB attenuation with an 8 ohm driver?

Second confoosian: With the L-pad in place on the left channel and 24 ohms fixed on the right w/o a cap, the 2 channels seemed to match with the L-pad reading about 6 ohms for both R1 (terminals 2&3)and R2 (1&2).

Remind of you nude parallel resistors on the beach?

Where can I find the 4 Pi Pro crossover attenuation chart? My copy from, omigosh, 6 years ago(?) is among the missing.

Here's the chart for 1" compression drivers. It only works for crossovers designed for 8Ω and with (second-order and higher) crossover frequencies around 1.6kHz.
Attenuation ( < 5kHz ) R1 R2 C1
==============================================
6dB 12Ω 30Ω 0.47µF
8dB 12Ω 20Ω 0.47µF
10dB 16Ω 16Ω 0.47µF
12dB 25Ω 16Ω 0.47µF
14dB 30Ω 14Ω 0.33µF
16dB 40Ω 12Ω 0.33µF
18dB 50Ω 12Ω 0.22µF
20dB 75Ω 12Ω 0.22µF
==============================================

R2 is connected across the crossover tweeter output. R1 is connected after that, placed in series with the driver. C1 is connected in parallel across R1.

I've tried these values on 1.2kHz crossovers and they work well, but once you get much below that, the values change. That's because of the reactive values of the crossover. The chart is different for 1kHz and below. I've worked out values for 1kHz, 800Hz and 600Hz, so let me know if you need them and I'll post them. But frankly, I wouldn't use a PSD2002 below 1kHz, not even with flea-power. I don't know about the DE250.

Understand that the selection of these values isn't really so much about crossover frequency as it is about the inductances and capacitances in the tweeter circuit. I'm talking about it in terms of crossover frequency as a sort of shorthand, since the values required to make a 1.6kHz crossover for an 8Ω driver fall into a fairly narrow range of values. But if you were to range too far away from typical crossover values, the chart might have to be altered too.

16 and 16 ohms, R1 & R2 with a .47 cap gives much better integration of the drivers. I'm even more amazed now with the quality of the B&C DE-250.

Got in the last 3 Cheskys I needed to complete the set from Jason. His Moondog operation, BTW, is the class act in the biz as far as I'm concerned. I've gotten 5 LPs now, and each one is cleaned and placed in a new sleve before it ships. Condition is just as he represents and the prices, considering the quality, are reasonable.

The Sibelius 2nd Symph showed me the 10dB atten. wasn't enough so I went to 12. Oboes sounded like English Horn and Trumpets, strident. Much better now.

Maybe...just a tad more atten. is called for, have to listen some more. Kinda on the cusp. If so, don't know whether to go back to the .33uF cap with the 24ohms or keep the .47 and add a few more ohms.

I use Altec 902-16HF drivers in my front and center PI7 speakers, this is the normal 902 driver with a 16ohm voicecoil.

After playing around with Spice and measuring the driver with the crossover, I arrived with these values:

R1 = 33ohm
R2 = 12ohm
C1 = 0.22uF

This gives a load of about 9.5ohm on the crossover, where the normal lpad with the Eminence driver, gives a load of about 9.4ohm.

All good so far, but I really can´t seem to remember how to calculate how many db´s this lpad is damping.

Do you have another chart for 16ohm drivers on hand ?

I have another question regarding lpad with topend compensation.

After much consideration I have bought four Eminence Beta 8A drivers, and eight BMS4524 drivers with 18Sound XT120 horns for my bipole surround speaker project.

I will be running the BMS4524 drivers in series for a resistance of 14-16ohms.

Can I just use the same lpad as above (if the sound levels match), or are there a better way to do this ?

I was thinking of using a single coil on the woofer, and a third order crossover at about 2200hz on the hf drivers.

Btw, these drivers are excellent, they sound really nice and the horns are good too.

C1 = 0.47uF
C2 = 10uF
R1 = 11ohm
R2 = 33ohm

When I simulate them in Spice, it seems the f3 might have shifted down a bit.

The most flat is the one using the C2=8.2uF, but it does not look as much like the standard crossover, as the one using C2=10uF.

Is the reason for the peaking response around 1800hz, to compensate for the falling response of the midhorn ?

• Altec902 vs. Eminence PSD 2002