Altec 604 D Enclosures

[charly1944]

Hi GM,
You replies are as dense as they are interesting!
Could you please clarify few points for me:
1.What WRT stands for?
2.When you refer to" offset driver from the top",are you measuring this distance from the center of the driver(as opposed to from the top of it) to the top of the front baffle minus the thickness of the wood used?
3.Baffle thickness reflex vent of 4'' (min) to 12'' (max):Are you refering to a vent which depth is just the thickness of the wood(3/4 inch)?

Enough for the clarifications.Let me now report what we have done with my friend's enclosures yesterday ( i don't know wether you read that i made a mistake when communicating the volume of his enclosures.They are actually,8.3 cub.ft and not 11.3 .Quite a subtantial difference):
I made two small panels of wood,5 mm thick fitting in the inside of the box, in which i cut two different vents (respectively A: 11.8'x7.8 ' for the first one and B:8.9'x5.9' for the second one) of much smaller size than the present bottom vent.Using the (B) panel just laid on the on bottom, and therefore reducing the substantially the present vent resulted in a dull and flatsound.The music was gone!We then try the A solution:The results were close to the one obtained with the original vent with may be a slightly better bass,but no substantial improvement.This mean that for a given height of the feet(2'') the results are not very sensitive to the size of this type of vent unless you change it drastically.We also tried the smallest vent(B) with higher stands but it was not better.Further increasing the feet height(from 2 to 4'') while keeping the original vent gave a brighter and more open sound but at the expense of a lack of precision in the mid and high freq.The only thing we did not try was to shorten the feet (to 1.5 inch for instance) in order to get a deeper bass while keeping or improving the overall balance and quality of sound .So the original set up and the set up with vent reduction A were about the best one in terms of outcome with small differences not justifiyng a change.I dont know wether the conditions of experiment were good enough to draw these conclusions but it is indeed disappointing and tells me that we could not improve what the gourou, who inspired this design more than 20 years, did at this time.
So i am stuck with a present enclosure giving a pretty decent result (although not enough bass),that i could assemble in a day,with speakers the centers of which are probably to low for my ear level (25.2')
As as said i dont see myself going for an OB solution if it requires additional amplifiers,speakers and and crossover.I am not sure i understand the principle of an MLTL and what i read in French was pretty obscure about it although i understand it is a pretty efficient approach interms of bass extension.I never listened to MLTL loudspeakers,at least to my knowledge, but if you think a well designed MLTL will give additional bass extension while preserving the musicality of those vintage design i am ready to go for it and to get equipped so that i can measure the Fs of the drivers(as well as the other TS parameters).Panomaniac indicated to me an easy way to do so with Dayton WT3 (or 2) ,apparently pretty simple to use,but after a check these tools would not allow me to measure the freq.response and i believe if i go for this project i should have the necessary measuring equipment and capabitities to assess what i do by measuring as well as by listening.Could you give me a link where i can see plans of the type of MLTL you are considering so that i have a good feel about the construction of it.
I like the idea of a removable vent baffle so that one can easily adjust the vent until one reaches the desired results.I guess that would be the back panel since i tend to favour rear mounting speaker and removable back panel is the only solution to easily access the speakers(By the way, I have no clue about the pros and cons of vent on the back versus the front vs the bottom).Should i understand that then,, you move to a permanent panel with a circular vent of the same surface as the square or rectangular one previously selected?
In terms of external dimensions, 25.6 ' width is clearly a maximum that i can accomodate.Sligthly less is better.When it comes to depth ,around 18 ' is a max as it would put the back the enclosure about 20 ' away from the bass trap in the corner.i am pretty free with the height which could go as far as 51.2 inch including feet.
I guess it is getting late here and it is about time for me to get some sleep and to let you go for a nap!Thanks a lot for sharing your precious knowledge.
Charles.

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