Modernising Altec Cabinets

[rolandr]

Efficient Altec drivers perform very well in vented MODERN looking cabinets. The need to copy older cabinet dimensions is largely unnecessary. Remember the older cabinet designs were pre Thiele and Small parameters derived thru trial and error using the "magical ratio" to further prevent standing waves. This resulted in bulky low WAF cabinets. You can build narrower cabinets with a frontal width of say 17" place the lets say coax 15" driver so that the horn is at ear level about 44" high. Then adjust the depth as needed to get the necessary about 10 cubic foot enclosure. The actual volume should actually be less than necessary and brought up as needed with fiberglass till speaker click is sharp. Remember your drivers T/S numbers will not be the same as per the tables so by ear fine adjustment is necessary. Generally the vented opening is about 19" square for the duplex series. You can cap your enclosure with
1 1/2" thick plate of solid or veneered wood after using a sleeve of acoustic cloth to surround the cabinet. Recycling the unequalled altec drivers in modern enclosures will assure continued use!!!

[Russellc]

Wouldn't This narrow front panel cause some sort of step response type problems from the bass wave being able to more easily "go around the cabinet" than with the wider stock altec dimendions? Remember, many of these systems had add-on panel wings to make the baffle even wider because of this problem. I think you might be underestimating the thought Altec put into this. Or, in the home listening situation, is it unnecessary to worry about this because of smaller room, generally closer listening position, and the unreal output of the speakers in question?! My A-& boxes take up a lot of living room realestate, but I don,t want to lose any bass. Have you noticed? (about the bass) I would be interested to know.

Russellc

[Russellc]

Oh, and one other question, being new to altec and all, what is meant by "speaker click"? Also, could you please describe what you mean about "After using a sleeve of accoustic cloth to surround cabinet"

Thanking you in advance for
answering my newbie queries.

Russellc

[rolandr]

This recommendation is a cosmetic improvement with no loss in sound quality. A frontal width increase of 17" to 32" should provide no significant increase in bass response yet would significantly detract from the cosmetic appearance of the cabinet. Placing the cabinet closer to rear wall or corner placement would affect bass response more significantly.

Speaker click refers to connecting the speaker to a small voltage like a 1.5 volt battery and clicking on and off. This is useful in assesing bass driver response in a properly tuned cabinet. You should start with less volume than needed and augment apparent volume with fiberglass till speaker click is sharp without going over. Going over is difficult to hear so therefore stop once click sound is sharp. You can also measure your drivers specific T/S parameters if you have the knowledge and equipment but even then the speaker click comes in handy to fine tune.

[rolandr]

A speaker sleeve=

Once you completed your cabinet you can cover it with modern acoustically transparent fabric by sewing the fabric into a sleeve like tube and sliding this over the cabinet. T

[Russellc]

I see, sort of like a vandersteen type of arrangement, your idea sure would open up some living room space.

Russellc

[billfort]

Putting Altec drivers in a more modern looking vented cabinet is what I tried to accomplish with my 604s but I personally think there IS some merit in trying to utilize some of the design elements used in the classic Altec boxes (the 620A in my case). For me, I felt sticking with the volume and tuning of the 620 was a good idea (9ft3/40hz) and this has proven to be valid ? my new cabinets sound better in the bass than the smaller cabinets they replaced, which also had fiberglass lining.

Getting the drivers higher as you suggested has worked out well ? I put them at 38? off the floor (ear level for me) ? this increased the soundstage height and maybe made images a little more focused, more lifelike size-wise. I also varied my cabinets pretty drastically from conventional rectangular boxes ? my 6 sided lumps are shaped to allow corner placement if desired and the vent location and placement is definitely NOT traditional.

Where I do not think it is a good idea to drastically change size however (and the 620A design) is the baffle width. Narrower baffles might be nice for ?audiophile? imaging tricks and keeping the wife happy but many feel they also lead to thin upper bass and lower midrange ? definitely NOT a price I wanted to pay to gain ascetic points. I never tried this out by making the potential mistake in the first place, but a few who have tried it, discouraged me in the planning stages. I liked the full upper bass/lower mid sound of the 604s in the old 25? wide baffle boxes and love the sound of them in the new 26? wide boxes ? I?m glad I stuck with tradition here.

I?d like to hear a narrow baffle/604 some day but I?m pretty happy with the mix of the old and the new I ended up with and hey, my wife loves them!


Sort of traditional cabinets

[rolandr]

Billfort:

Hard to explain how a frontal width change from 17" to 25" could make a big difference as long as all other parameters are kept constant.

Dr. Olson did demonstrate diffraction changes having to do with shape of cabinets and rounded corners but do not believe it would make any difference here.

Changing the magical ratio of cabinet dimensions may produce more standing waves but fiberglass should help. But if you think about it all you are really doing is placing the side of the cabinet frontward that is 18" front 24" depth and 48" high= about 10 cubic feet volume

The important point is for these great drivers to get common use we need to lose the idea that vented cabinets need to be clunky. I see too many people selling off these drivers and enclosures simply because they are too "large bulky and old looking". Horn enclosures are a different matter altogether they are the simply the price you need to pay for extreme efficiency.