How to crossover to Sub at 50Hz?

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I have designed a 3 way + sub in a MTMWWSubSub speakers:

Tweeter: Dynaudio T330D: 2kHz (LR4) - 20kHz
Mid-woofers: Twin SS18W8531G00: 150Hz (LR4) - 2kHz (LR4)
Bass-woofers: Twin SS26W8861T00: 52Hz (BW2) - 150Hz (LR4)
Sub-woofers: Twin Peerless830500: 20Hz - 52Hz (XO slop to be decided)

The bass-woofers are in a sealed box with a F3=52Hz Q=0.68 with no electronic LP or HP. The lowest room mode is around 24Hz.

I think 0.68 is close enough to 0.707 so I could assume the roll-off response of the bass-woofers to be BW2. The question is how to cross the bass-woofers to the sealed subs?

(1) I initially planned for EQing the sub to be flat then LP at 52Hz with a BW2. Connected in reverse polarity, this would have a 3dB bump at 52Hz, which I could live with. But I am worried about 2 problems: (a) at 204Hz it is only 24dB down and at 406Hz only 36dB down. I don't want the subs to contribute to the sound above 200Hz. (b) I have just realised that because the bass-woofers are crossed at 150Hz with a LR4, there would be a substantial amount of phase shift around the area, so a BW2 with the sub would not work! Please let me know if this is a problem or not.

(2) Put an electronic BW2 HP at 52Hz for the bass-woofers to make it a LR4 HP. Use a LR4 LP for the sub. This would work but the group delay may be unacceptable! It was for this reason I initially choose the 3way+sub approach instead of 4way to avoid large group delay at low frequencies. This effectively converts it to a 4way.

Any solutions?

Many thanks

Thanks for your reply. Glad to have another forum member from Sydney.

I am rushing up to finish the speakers in a couple of weeks because the wife complained having loads of stuff all over the places and my friends will be coming over to stay with us over Easter. I tried using Speaker Workshop to measure the drivers, but after doing all the impedance measurements, the PC went south. I got a new motherboard for the PC but the new sound card did not have adequate resolution. I then used the M-Audio Transit and somehow burnt it. I then bought a Creative Sound soundcard but found it clips no matter what! just a bad quality soundcard. So I am temporarily giving it up and use simulations to complete the speakers.

By the way, do you have measurement equipment?

I use Synrta (free download) and a cheap electret mic (no calibration); This is useful for getting tweeter levels right & dealing with peaks, but not much use at the low end, too many room problems complicate the readings.
I must get off my **** some day and drag the gear outside and see how it goes there - but I'd rather be listening to music :)
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.