my new 604 cabinets I'm building.

**VolvoHeretic** · October 12th, 2011, 03:27 AM

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?

**cradeldorf** · October 12th, 2011, 05:35 AM

Originally Posted by VolvoHeretic

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** · October 12th, 2011, 11:17 AM

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)......

Originally Posted by voice of the theater

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** · October 12th, 2011, 12:53 PM

Originally Posted by voice of the theater

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** · October 12th, 2011, 01:19 PM

Originally Posted by cradeldorf

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** · October 12th, 2011, 01:39 PM

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?

**Altec Best** · October 12th, 2011, 02:56 PM

You need to be exact with the numbers to be accurate with the results. I think you said 12.44 cubic feet in an earlier post.But from that .jpg looks like you put in 12 cubic ft.IIRC you have 2 different 604's that you had GPA recone correct ? If so what did they recone them as 604 g,h, ???

He came up with the 41 Hz from your port dimensions I think.You may need to add length to the port to lower it some. 25-30 Hz port tuning is more in line for HiFi/HT I think GM was getting at.

**cradeldorf** · October 12th, 2011, 04:56 PM

Originally Posted by Altec Best

You need to be exact with the numbers to be accurate with the results. I think you said 12.44 cubic feet in an earlier post.But from that .jpg looks like you put in 12 cubic ft.IIRC you have 2 different 604's that you had GPA recone correct ? If so what did they recone them as 604 g,h, ???

He came up with the 41 Hz from your port dimensions I think.You may need to add length to the port to lower it some. 25-30 Hz port tuning is more in line for HiFi/HT I think GM was getting at.

Thank's AB I calculated my box dimensions then deducted what I calculated for all the braces plus 432 CuIn (.25 CuFt) for the speaker displacement and came up with a grand total of 12.184 CuFt of volume. so now I'll recalculate the box frequency using those numbers.

I would be more inclined to change the size of the port per GM's recommendations as opposed to lengthening it.

I'm mulling over filling all the voids between the braces with 2" egg crate foam. I hope the 2" is the total height of the foam plus the eggs and not just the foam itself.

With those dimensions I come up with a box freq of 29.3448, there seems to be a conflict because Altec list's the cone freq. at 25 where T/s parameters put it at 27.1...... : /

**Altec Best** · October 12th, 2011, 06:39 PM

I'm not sure foam is a good dampening material internally in the cabs.Good old Fiberglass insulation performs better IMO.YMMV

Maybe someone else could help out with this decision and chime in.I only ever use insulation.

**cradeldorf** · October 12th, 2011, 08:13 PM

Originally Posted by Altec Best

I'm not sure foam is a good dampening material internally in the cabs.Good old Fiberglass insulation performs better IMO.YMMV

Maybe someone else could help out with this decision and chime in.I only ever use insulation.

I don't think I need dampening, That's only for small boxes that you want to make sound larger than they are. What I want is to break up the standing waves and keep the mid frequency waves from bounding all around the inside of the cabinet and coming out through the port or cone. Actually I think I'll try it as an sealed box first because it's just over the size where Altec reccomends an infinite baffle. I can always port them afterwards.