Hi, GM
I didn't have any idea that Fisher had shared your design and PMs without permission, otherwise I never would have referred the OP to the sites. That really wasn't kosher for those boys to do that, and I hope it hasn't discouraged you from sharing your ideas with us DIY folk.
Best wishes,
David
Greets!
No biggie, it's old news and no, for the most part it hasn't, though I now limit most help to on-line Qs.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Charles, interesting to hear you are from France, are the enclosures based on Jean Marie-Piels speakers? I only have the following small picture from Revue Du Son No. 225 Dec. '98, but from what you describe they could be very similar. Unfortunately I do not have the article but would love to see a scan if you can locate a copy.
No apologies needed, it happens sooner or later to all of us.Originally Posted by charly1944
No, I didn’t know you were French [or I forgot, a real problem for me now] as like so many Europeans, your English is as good or better than way too many public school educated locals, at least around me.
Correct, I’m really disappointed GPA doesn’t include as standard, or at least offer, the T/S specs for a reasonable price upon request. Actually, since they know the various specs of the sub assemblies [Mms, Cms, Re, etc.], they could easily calculate them in an Excel or similar spreadsheet ‘close enough’ for cab design.
The only real variable would be how well they drained, re-magnetized the magnets, but in a cab large enough to allow some tuning flexibility, this hopefully won’t be an issue, though again, there’s been some re-cones where the re-charge didn’t go well, which results in an unacceptably high Qts. Since yours sound good, odds are that they are fine.
Anyway, try to get them from GPA and if you can’t, then experimenting with vent tuning is easier than learning, doing T/S measurements if you have no one local to do it for you.
WRT tuning, the math is fairly intensive for other than a simple reflex, but I can sim different vent lengths close enough using MJK’s software and if you choose to use a bottom loading vent, calculate a minimum stand height.
Again, the cab would be taller with height typically based on seated ear height for an offset driver layout that requires the least amount of internal damping, so for ~38” it would be around 62” i.d. [inside dimension] for 11.3 ft^3 using 19 mm thick construction and assuming setting on the floor with the vent on one of the sides near/at the bottom. Width x depth would normally be an acoustic or golden ratio to minimize internal damping. Using the golden ratio, this would be ~22.58” x 13.95” i.d..
Anyway, just an example...........
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Hi GM,
I dont know where you are located in the US but it seems to me that you are on the site either very early in the morning or very late at night!
Actually GPA told me that they are not used to measure the speakers as a standard service .Since i insisted to get my 604 measured after the reconing(i was advised by Jeff Markwart that it would be useful for cabinet and crossover design)they accepted to do it but then had no time to actually perform the measurements.I guess they had other priorities and actually i was not ready to wait for weeks.
For now and without measured elements to guide me ,i guess i have multiple options
1.To copy my friend's enclosure and to change(reduce) the dimensions of the vent and assess the results by listening.
2.To keep the same design (bottom vent boxes)but change the dimensions of the boxes and of the vent while keeping the total volume.In this option i noticed that for the width vs depth they are a lot of acoustic ratios published and none of them correspond to the golden ratio.So i am a little bit at loss when it comes to select one of those.Any recommendation?Regarding the height, my ear are at about 3 feet from the floor.So what could be the ideal dimensions of the boxes(without the stands).And what distance should i keep between the upper part of the speakers(rear mounted)and the upper part of the front baffle?Last but not least ,what should be in this set up, the dimensions of the bottom vent to get to an around 40 hz tuning?By the way,Altec Best suggested to go for circular vent rather than rectangular one.
3. to change the design and go for an MLTL( or a OB if the dimensions are reasonable in this relatively small room -12x16 feet).
What would you advise me to do .
GM,if i take too much of your time,let me know,i will understand.
Thanks,
Charles
Charles,
Are you able to take advantage of the room corners? In other words, might you be able to "build-in" large floor to ceiling corner IB boxes canted approx. 30 degrees towards the listening position? If so, this would be my first choice and you could add eq or series resistance to balance the system. This layout also gives you maximum boundary reinforcement while minimizing diffraction and creating a pseudo early-reflection-free zone, not to mention using the minimum floor space. Also, if your corner walls are sufficiently rigid, you may be able to get by with building just a well reinforced front baffle screwed and sealed to wall, floor and ceiling furring strips -- it doesn't get much easier than this. A 4' wide (standard for plywood in the USA) baffle set at 30 degrees will yield about 25 cubic feet.
Building a large enough closed box will also mean that you can stop agonizing over your speakers' TS measurements -- they are what they are, and as long as the pair are more or less the same, you will be in business.
Best wishes,
David
Last edited by David Yost; January 19th, 2012 at 09:33 AM.
As for Open Baffle, here is a pair of 605As that I showed at the Lone Star show. The helper woofer is an 18" pro model with its own amp and active crossover.
Lone Star Audio Fest 2010, Dallas Texas | Hifi Zine
David,
The only corners i could use are covered from floor to ceiling by bass traps(minichunks) made of rockwool and covered by 5 thin panels of wood of 2'x2' for each corner not to deaden the room.I would have to remove 3 of them in each corner to allow enough space for the two 604 and enough air around the drivers.I will then have in each corner one covered bass trap of 2'x2' at floor level and another one at ceiling level ,leaving enough space in between for a baffle about 3.5' wide 6.0' high ;I dont know wether this is enough to do the trick. If i get rid of the 2 bass trap together,i dont know what kind of impact it will have on the acoustic of the room which i spent months to treat acoustically with decent results for a relatively small room. By the way,when you refer to" Eq or series resistance to balance the system" ,how do you achieve that?
Any way we have got a potential option that i could work on with some additional guidance.
Regarding closed boxes not to have to worry about measures of the speakers,how big is "large enough"?I have to tell you that the 11.3 cb feet of my friend 's speakers are the maximum size i can accomodate .Actually i would prefer taller but not as wide boxes.
Thanks again for your input David.
Charly.
Hi Charly ! I had a similar experience with my re-cones. I needed them measured as well.So I asked Bill and he said it was really something they didn't want to do.But I paid him for the service and they came back with the T/S parameters.What was more important to me was that the recones were matched since my project is a dual woofer (416B) Corner box.
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