Far too lean 604-8Gs in 620 kabs

[amandarae]

Hi, I have 604-8g in 620 cabinet MDF copies.
I m not getting the bass and tonal richness i expect from the 604's in those cabs (I'm not at bass junky as I used lowther horns for a decade or more).
I thought this was an issue in my previous home, but now i have placed the Altecs in comers on an end wall in my new home, to no avail.

I'm using the Markwart Simplified 604-8H EQ Crossover with values for 604-8g.
I don't know the history of my Altecs i bought them used in Norway, but bass membrane and surround looks almost new (or too new for 30 year old speakers).
Due to a resonance from a cartridge arm mismatch (the cartridge suspension was also throwing in the towel due to high age) I heard that the Altecs where capable to produce an earth shattering low end.


But generally they are far to lean (they are not out of phase).
I'm using a very rich, meat and blood setup, i.e. VPI Classic, Denon DL103, Leben RS28CX, Quicksilver KT88s (with 6L6GCs).
I get the same leanness with digital - AIFF via a reasonable DAC.

The cabinets are probably somewhat over damped (damping material on all internal sides).
I'm using Mundorf MCap RXF Radial Polypropylene Caps ( I got them with the Altecs) they are probably somewhat bright but could probably not have this big an effect.

Any Ideas, I would really love to hear the Altecs at they're best
Best regards
Kjartan

Assuming that your drivers are fine, I mirror that same experienced of yours. I have the 604-8G's. I used the JM XO, the Altec 604-8G XO and many more variations of it and cannot find the 620 cabs to sound good to my taste. My 612C cabs sounds better to me. To me, the 620 cabs bass is bloated and undefined(could also mean less depending on room interactions) and something is amiss on the midrange compared to the 612C or Open Baffle using the 604-8G's. Just my experience.

Abe

[KBergsson]

Assuming that your drivers are fine, I mirror that same experienced of yours. I have the 604-8G's. I used the JM XO, the Altec 604-8G XO and many more variations of it and cannot find the 620 cabs to sound good to my taste. My 612C cabs sounds better to me. To me, the 620 cabs bass is bloated and undefined(could also mean less depending on room interactions) and something is amiss on the midrange compared to the 612C or Open Baffle using the 604-8G's. Just my experience.
Abe

Hi Abe, my problem is in reality the opposite of bloated, it sound more like it is overcontrolled (very dry) but reduced volume, compared to the middle and top.
Regards
Kjartan

[GM]

To me, the 620 cabs bass is bloated and undefined(could also mean less depending on room interactions) and something is amiss on the midrange compared to the 612C or Open Baffle using the 604-8G's.

Yeah, long, boring story about design cut short, moving the vent to the extreme bottom will cure these problems for most folks, though some [like me] need to additionally critically damp the vent to get a fast transients 'sealed with extra gain' response.

GM