Passive woofer for 620 cabinet

[Fran604g]

Maybe this is a crazy (or just ignorant) question, but I've noticed that many of the folks here with 604-G's in the various cabinet configurations complain about the bass being a little light. I'm not sure I agree, I've always loved every nuance of my 604-8G's for over 20 years now. That being said, however, I've had friends comment on the same perceived lack of bass "punch." I wonder if instead of adding a subwoofer to the system, why couldn't a passive woofer be added to the enclosure? Would this increase bass?

[LICORNE]

Hi,

I don't recommend it. You need XO 80Hz active
Altec 3000 series in a Altec Sub Woof.Cabinet.

Then your friends won't criticize.

GPA has plans and models. You will need 400 watt amp to get the sound out.

[diemaker]

Hi,

I have built two sets of cabinets using the standard 15" Dayton passive radiator that Parts express sells. I'm running 604-8g's in one set and 604-8k's in another. One of the sets of cabinets has the same exact dimensions as the ones forum member billfort has previously posted many times here. His design is based on the 620 altec cabinet as far as internal volume goes. I mounted the passive on the baffel down low and the 604 at the same height as in the plans. The center braces were shifted to accomidate the two 15's. I have been listening to the first set for over a year now in my living room. There is no lack of bass. I am a bass player, I like tons of it. Give it a shot, I doubt you will be disappointed with the results. Maybe some of the more learned members of this forum can explain why this seems to work so well. I'm just a hack at speaker design. I had originally considered mounting the passive on the bottom of the cabinet and having it fire down towards the floor, but I liked the results of the first version and I didn't make any changes. The whole story of how I arrived at this involves a trip I made to Wally Heider recording in SF in 1975, and a visit to a friend and customer that is the operations head of a major musical instrument manufacturer in Petaluma, CA two years ago. If anyone is interested in any details about this I will provide more info.

[LICORNE]

Hi

What this design does is seperate the lows from the mids at a higher frequency. Not quite the real sub woofer pro that you hear at the theatre.

http://www.geocities.com/rafaleconve...?1139974510320

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[LICORNE]

I forgot to mention:

You have Sub, Bass ,Mid bass.

Your 604 8g can handle bass and nid bass verry well in the 620 cabinets. what you really need is
the frequency that these speakers cabinet cannot reproduce. I know I tested them all with signal generator in the 70's.You cannot hear them at 45hz
You can see the cone moving but they are silence.
Thats why the need for sub woofers is necessary to hear HEAR HEAR below 100 HZZZZZZZZZXZZ

[Fran604g]

Thanks for your replys to my post. The 620 cabinets that I'm using were made for the Model 18, but I don't see why that should make any difference in the sound and in 1985 I didn't know or care, since I lucked into them ($150 for both, with xovers) and was just happy to have something to house the drivers. I bought new old stock 604-8K crossovers from Bill at GPA a few years ago and replaced the ones that came with the cabs (1-N801 and 1-N809.) I blew the lo-end caps out of the xovers and replaced all of them with new ones. I like the idea of increasing the bass output of the cabs, maybe not so much the lo end of the freq response. I think I may try the down firing passive approach because I have had wheels mounted to the bases of the cabinets and they seem to transfer more of the bass feeling to the room than without them. I would rather have spikes on the cabinets, but I don't have a perfectly flat floor to set them on, since my house is 200+ years old.

[Fran604g]

On second thought.......

[GM]

Greets!

FYI, I calc a ~1 mm sag if bottom fired and not knowing how much excursion you're actually using, I calc a 3.91" spacing based on Xmax.

WRT an uneven floor, I use only three spikes.

GM

[Fran604g]

Greets!
FYI, I calc a ~1 mm sag if bottom fired and not knowing how much excursion you're actually using, I calc a 3.91" spacing based on Xmax.

WRT an uneven floor, I use only three spikes.

GM

Hi, thanks for the info... I hate to sound too ignorant, but I understand everything that you said except, "a ~1 mm sag" and "a 3.91" spacing based on Xmax." I see the three peg solution,(I should have thought of that!) Could you elaborate, please?

[GM]

Greets!

You're welcome!

In a downfiring position, gravity will cause the PR to sag approximately 1 mm, so its linear excursion will be reduced by this amount on a positive pulse and increased by ~1 mm on a negative pulse. IOW, it effectively has ~1 mm less usable excursion.

Xmax is the driver's ~10% excursion distortion point that most designer's work around, so I calc'd how much distance between the driver and floor is required to ensure it doesn't audibly compress the PR's output when the driver is driven to its Xmax at Fb (tuning frequency where the PR is operating at its peak).

GM