Altec 604-8g's how to improve?

[Terp]

Hi all,

I have a pair of 604-8G's that I love. They are in original Altec 612C cabinets and have new GPA crossovers. I was thinking about maybe different cabinets? Maybe add a subwoofer? Any ideas would be welcome.

Thanks!

[Phil-G]

Hi Terp, kinda slow here sometimes.
there's a lot of people here that can give you a few really good pointers. best i can come up with is, depending how old the diaphragms in the tweeters are, you could replace them with newer GPA ones. having not heard the 612 cabinets, it would be difficult to have a suggestion as far as a sub goes.
i use a sub with my 828 cabinets. makes a nice difference with them.

[gearfreak]

- what do you like about them
- what do you want to improve?
- would you go to a bigger cabinet?

Seems bass response is on the list -

The 612C is spec'd as 6.8 ft3, I don't see a cabinet tuning listed.

You might first get an idea of what you are dealing with,
- by measuring the impedance response of the LF section.
- by measuring the 'free air' parameter impedance response of the 604 itself.
A bass reflex should exhibit 2 peaks in the LF. So comparing/contrasting the two, you get a picture of what the cab is doing to the driver response as a matter of now being a system.

Then you can block off the port and see (while hearing) what difference that makes.

Then infer whether enlarging (or otherwise tweaking) the port is what you might want to do, or might want not to do.

I have 604's in 3154's (spec'd: 6 ft3) and have a bit of a hole from 55-80hz, maybe ranging a bit higher, ...to sort out.

[Terp]

- what do you like about them
- what do you want to improve?
- would you go to a bigger cabinet?

Seems bass response is on the list -

The 612C is spec'd as 6.8 ft3, I don't see a cabinet tuning listed.

You might first get an idea of what you are dealing with,
- by measuring the impedance response of the LF section.
- by measuring the 'free air' parameter impedance response of the 604 itself.
A bass reflex should exhibit 2 peaks in the LF. So comparing/contrasting the two, you get a picture of what the cab is doing to the driver response as a matter of now being a system.

Then you can block off the port and see (while hearing) what difference that makes.

Then infer whether enlarging (or otherwise tweaking) the port is what you might want to do, or might want not to do.

I have 604's in 3154's (spec'd: 6 ft3) and have a bit of a hole from 55-80hz, maybe ranging a bit higher, ...to sort out.

I like the midrange and "live" soundstage.
I would like more bass and a more cohesive sound (compared to my other speakers, PSB Imagine T3's)
I also would like a nicer looking cabinet, taller (ear level) and possibly larger CU ft.

I dont know how to do those measurments, ie LF frequency response etc.

Thanks

[bowtie427ss]

9 ft3 minimum ~ 40hz tuning, with a broad/wide baffle to control step response

Markwart phase corrected network, or just go active and don't look back.

Where's 604man with those 20+ ft3 boxes?

[604man]

9 ft3 minimum ~ 40hz tuning, with a broad/wide baffle to control step response

Markwart phase corrected network, or just go active and don't look back.

Where's 604man with those 20+ ft3 boxes?

HI, Yes just search "604-8g big cabinets big sound".

the cabs work good I gave the dimensions in the post .


604-8G.jpg

[gearfreak]

I like the midrange and "live" soundstage.
I would like more bass and a more cohesive sound
...
I dont know how to do those measurments, ie LF frequency response etc.

Thanks

a) to avoid cabinetry work you could first try a "current-drive" / "transconductance" / "constant current" amp instead of a 'voltage drive' amp. Your work would be to determine what is one, and then finding one to build or buy. (we presume the latter).
For that however, you will then need to build a current-drive crossover.
I have a simple working example based on the info presented in: PassDiy

It would seem that in practice there can be a grey area, or transitional zone wherein voltage driven becomes (closer to?) current driven (perhaps a matter of 'added series resistance', perhaps not).
Others can comment on the veracity of those terms used. I am discerning the differences myself at the moment.


b) In olden days, you would plot this manually using a certain technique.
Nowadays Parts Express sells the 'DATS' unit for your computer. There may be others.
Pretty much: You hook up the driver, and press a button.
An example of the (free air) impedance plot I created for my 515's can be seen at: Altec / GPA measurements: 515 - diyAudio



ps. in other threads when 'Z' is discussed, it is nominally referring to 'impedance'

[604man]

I like the midrange and "live" soundstage.
I would like more bass and a more cohesive sound (compared to my other speakers, PSB Imagine T3's)
I also would like a nicer looking cabinet, taller (ear level) and possibly larger CU ft.

I dont know how to do those measurments, ie LF frequency response etc.

Thanks

What do you mean by a more cohesive sound ???

[Terp]

Well it seems that I have a pair of GPA 604-8HII's and Markwart Crossovers on the way so... Not sure how these things happen sometimes but. They are coming with plans for MLTL cabs so I may go that way. I will do some listening comparisons to the Altec 604-8Gs I have with the GPA crossovers etc and can compare the speakers and the crossovers. Should be fun!

[Earl K]

Hi all,

I have a pair of 604-8G's that I love. They are in original Altec 612C cabinets and have new GPA crossovers. I was thinking about maybe different cabinets? Maybe add a subwoofer? Any ideas would be welcome.

Thanks!

Look to the Urei 813 or Urei 813A for some inspiration ( for filling out the bass ).

Google will find you the details.