my new 604 cabinets I'm building.

[cradeldorf]

I'm still quite confused on this, especially after reading my Radio Shack "Advanced Speaker Design" book three times and doing all of the math long hand. Isn't the only frequency coming out of the port the box/port resonance and at Fb the speaker is motionless and all of the air motion is in the port and in faze with the woofer? Doesn't aiming the port out the rear, bouncing off of the wall make it out of faze with the woofer?

This is where I got my info from Volvo, otherwise I probably know less about understanding this stuff than you do.
TA Speaker Topics: Vent FAQ's

[voice of the theater]

I would wait to cut the ports until you hear from GM and others here as far as their recommended size and location of the ports. I don't know much about building cabinets, but I think there's a reason that all of the Altecs I've ever seen had ports in the front of the cabinets, not in the back. Also, the page you're referencing (in your post number 30 of this thread) shows a picture of an 846A Valencia. Again, I'm far from an expert on DIY cabinets, but if that picture is any indication of the date/year of the "Altec bulletin" you're using as a reference then it's a very old reference (from the 60's) and I know that the cabinets Altec used back then were tuned much higher than later Altec cabinets like the Model 19 cabinets. I think by the later 70's Altec had a much better "handle" on cabinet tuning as far as how to get really deep bass out of a cabinet. I wouldn't use the port size that Altec recommended in the 60's if you want to get deep bass (more modern "hi fi" tuning) out of those cabinets. As I mentioned before, I'd wait and get recommendations from GM and others here (regarding port size/location) based on your exact cabinet dimensions and 604's that you're using (or in lieu of that, find a much more modern source/reference to achieve a more appropriate/modern cabinet tuning that will allow significantly deeper bass)......

Wow--those are beautiful cabinets--nice job!! Have you/how are you going to determine the port size/location/cabinet tuning?

That's why I asked you this question earlier in this thread. I suspect the problem you're having with the AS 101 cabinets is that they're not tuned for 604's (and someone apparently also failed in their attempt at DBR tuning with the "shelves" they installed in the cabs). I think these new cabinets will be much better for your 604's IF "appropriately" tuned/ported. You're at a crucial step right now that will "make or break" the success of this project IMHO.....

[cradeldorf]

That's why I asked you this question earlier in this thread. I suspect the problem you're having with the AS 101 cabinets is that they're not tuned for 604's (and someone apparently also failed in their attempt at DBR tuning with the "shelves" they installed in the cabs). I think these new cabinets will be much better for your 604's IF "appropriately" tuned/ported. You're at a crucial step right now that will "make or break" the success of this project IMHO.....

I think you would be astonished at how much bass my as101's make Vott. they literally shake the fillings in my teeth. :; <---see one tooth fell out already. . I wish Greg hung out here more....but I guess he's doing his own thing and I can respect that. I think I'm gonna split the back board so I can just replace the bottom half with a different one with a different port size in it.

[voice of the theater]

I think you would be astonished at how much bass my as101's make Vott. they literally shake the fillings in my teeth. :; <---see one tooth fell out already. . I wish Greg hung out here more....but I guess he's doing his own thing and I can respect that. I think I'm gonna split the back board so I can just replace the bottom half with a different one with a different port size in it.

I understand you're getting a lot of bass out of your current cabs and that you have some real issues with the sound quality you're currently getting with them--not just bass issues. I would wait a little longer to see who chimes in on this thread (hopefully GM) before you move forward--you may learn that a port in the back of the cabinet is not the way to go. I think you may learn that "out of phase" issues are a valid concern and if that is the case, that will really be bad for overall sound quality, not just bass. You may find out that the port "should" be in the front of the cab. As far as cabinet tuning/port size/location, keep in mind that this will effect the whole ratio of lower bass to mid-bass and midrange. Nothing to lose by waiting a couple of days for assistance here and in the meantime you could do a little more online research as well (i.e. possibly finding a more modern source for port/tuning calculations)......

Not to get too philosophical here, but I've learned the hard way that in life in general it's a very easy mistake/pattern for people to fall into (myself included) to rush when they should move slowly, and to move slowly when they should be getting their @ss in gear......

[cradeldorf]

I just don't know how he calculated the 41 hz box tuning frequency? I just used this online one and came up with 29.4836? Not sure If I'm doing it right, but it looks right. Did you read the link I posted in post #32 by
John L. Murphy Physicist/Audio Engineer?

[voice of the theater]

I think you would be astonished at how much bass my as101's make Vott. they literally shake the fillings in my teeth. :; <---see one tooth fell out already. ......

I'm not saying that the current tuning of your AS 101 cabs with regard to being used with 604's isn't resulting in enough bass. Quite the contrary, from this post and some of your other posts in other threads, I think the fact that those cabs were not tuned with 604's in mind may be giving you way too much mid-bass response which is throwing off the ratio of midrange to midbass to the "lowest" bass your speakers can produce and resulting in a "mess" (yes, I know, a very technical term) and the "shelf" that someone added in a failed attempt to implement DBR tuning may be reeking havoc with the tuning/sound quality as well in ways I can only imagine since I haven't heard them. Hopefully these new cabs, once tuned/ported/insulated/etc. "properly", will sound great!

[GM]

I think you would be astonished at how much bass my as101's make Vott.

I wish Greg hung out here more....

I think I'm gonna split the back board so I can just replace the bottom half with a different one with a different port size in it.

Bass or mid-bass? Vintage tunings typically were mostly mid-bass, same as most prosound still are, not to mention most recorded music peters out quickly below ~40 Hz or higher in older recordings.

Regardless, without response measurements at the listening position [LP], need to know how much series resistance there is as well as room acoustics to zero in on what you?re hearing, so mostly a rhetorical question unless you have perfect pitch.

Circumstances has forced me into a ~ one [more like half] man ?crew? doing a whole property rehab on a shoestring budget, so at best probably won?t have much quality time for at least another year to spend much time on the forums, PMs, etc.. The rain has stalled me till probably tomorrow and should be doing indoor stuff, but you know how it is with hobbies??..

Good plan, I typically recommend a removable/gasketed vent panel to allow easy tuning changes. That, or use heavy cardboard or PVC pipe vents left extended enough to easily swap them out, using blu-tac or similar to temporarily seal them to the baffle.

GM