I'm attempting my first cabinet build....be gentle.

[cradeldorf]

Ok this is what I came up with, I went to page 22 of the 1974 altec enclosure design booklet, I calculated the volume of the square cabinet on that page in square inches and then I divided it by the square inches of the port which gave me 523 square inches of box volume for every square inch of port, I Then calculated the volume of my cabinet in square inches and divided it by 523 which gave me around 21 which is how many square inches of port I need. So either a 2 inch by 10.5 inch slot or a 5.25 dia circle would be the right size for the port...Right?

[Altec Best]

. They even published some of his private correspondence without his knowledge/consent.

Now that's a real idiot !!!! Private means (PRIVATE) !!

The main reason I built them was to get the speakers off the ground and at ear level when sitting on the couch.

If this was your problem why didn't you just raise those cabs you already had (Built Stands) to get them off the floor ?

As I have found out over the past 4-5 months if it isn't a published design a lot of work has to go into it.Measurements,Knowledge,etc...

If it wasn't for the gracious support of some of the gurus here mainly GM,Panomaniac, I would have never attempted a build from scratch without it,way beyond my skill level.It's nice to get an assurance of support before any finances are commited to your project.Otherwise I would have been looking for another pair of 19's maybe 2

[GM]

Thanks for Chiming in Greg.......

Is there anything I can do to salvage these cabs or are you saying there's nothing I can do to get them to deliver serious bass?? Should I just make them sealed? or leave the stuffing out?

You're welcome!

I guess you have to first define what you mean by serious bass since until fairly recently this actually meant serious upper bass (80-160 Hz) and still does in the vast majority of prosound apps, though with the advent of the tapped horn (TH) and especially all its DIY clone rip-offs/TL variants, this is changing to a greater or lesser extent in some areas of the world.

Then there's the semantics problem of serious bass being labeled sub bass these days due to the impact home theater (HT) system marketers has had on the public's awareness.

Anyway, bass has historically been the 20-40 Hz BW, so no serious bass thanks to Hoffman's Iron Law, though again, the 6th order alignment TH has shown a way to realize very close to the theoretical limits of a given net box volume (Vb) by utilizing both the front and rear of the driver's output instead of just its rear's in traditional vented alignments: TA Speaker Topics: Loudspeaker Design Tradeoffs

Room modes, speaker low distortion power handling at the lowest frequency signal source it's likely to 'feel' the need to reproduce at whatever peak SPL you're likely to listen at and especially personal preference WRT the system's tonal balance, dictates the cab's tuning in a HIFI/HT app, so while one can scale vents to find a different cab tuning (Fb), only finding it empirically will get you the best overall trade-off.

Then there's the issue of the impact any series resistance due to amp output impedance, XO inductors or other resistive components will have on the driver's effective Qts, ergo the amount of increase of the cab's net Vb required for flattest in-room response.

Last, but not least, having two different series of drivers and probably different enough specs to require individual tuning which with so little net Vb available for any realistic tuning flexibility (and why I typically spec 10-20+ ft^3 cabs for vintage 15" Altecs), sealed or at least ~aperiodic (leaky sealed, i.e. stuffed vented) may very well be the best solution overall to keep any perceived channel tonal imbalances to a minimum and use a sub system to fill in the mid bass on down to however low you want to go and/or afford to WRT bulk, placement, WAF, etc., issues.

Or you can ignore all the above and take the stance that the late Altec knew what was best as some folks do and tune it to between 36-42 Hz and drive them with a high output impedance tube amp, preferably with variable DF (bass tone control) to dial in the amount of in-room bass 'warmth'. Not a very 'tight'/'fast'/'accurate' bass line, but euphonically pleasing to many, especially if the source is vinyl and/or RTR tape.

That's the real 'beauty' of DIY, you CAN have it your way (or at least as close as practical WRT budget, etc.) once you understand how to best achieve it.

GM

[cradeldorf]

Now that's a real idiot !!!! Private means (PRIVATE) !!



If this was your problem why didn't you just raise those cabs you already had (Built Stands) to get them off the floor ?

As I have found out over the past 4-5 months if it isn't a published design a lot of work has to go into it.Measurements,Knowledge,etc...

If it wasn't for the gracious support of some of the gurus here mainly GM,Panomaniac, I would have never attempted a build from scratch without it,way beyond my skill level.It's nice to get an assurance of support before any finances are commited to your project.Otherwise I would have been looking for another pair of 19's maybe 2

I think the original cabs I had looked like old zenith tv's and to lift them the amount I had to they would have looked really awkward, plus I don't have a very big room 11x 22 so they were really too wide for that to be practical.

[cradeldorf]

You're welcome!



Or you can ignore all the above and take the stance that the late Altec knew what was best as some folks do and tune it to between 36-42 Hz and drive them with a high output impedance tube amp, preferably with variable DF (bass tone control) to dial in the amount of in-room bass 'warmth'. Not a very 'tight'/'fast'/'accurate' bass line, but euphonically pleasing to many, especially if the source is vinyl and/or RTR tape.

That's the real 'beauty' of DIY, you CAN have it your way (or at least as close as practical WRT budget, etc.) once you understand how to best achieve it.

GM

I would never ignore the words of one of the greatest cabinet guru's known to man It'll just take me a few readings to get the jist of what your saying. I'm coming up on 50 and things don't sink in a easy as they used to. Plus I need my glasses on I'm straining to see the screen. When I said serious bass I was referring to the original one you mentioned, the 20 - 40 Hz one. My main thing I use these for is Home theater and all I can remember is how awesome they sounded in the cabinets they came in even though the E had a problem. Thanks for spending your time helping me buddy.

[cradeldorf]

Maybe I should just build a new wall 1 foot in front of the existing wall and mount the speakers into it? I would have the ability to make the cabinets up to 44 cu ft. would that be too big?

[GM]

Thanks for the 'attaboy', but that's laying it on a little thick, don't you think? The pioneers of audio up to the latter day inventors take up all but the seats up in the nosebleed section. Doesn't leave much room for me and all the other advanced DIYers around the world, so we 'stand on their shoulders'.

Understood, there's a lot to know if you're serious about speaker system design, otherwise just build as big a cab as you can tolerate, tune the vents in-room and call it good enough. Worked well enough for me and for the friends, relatives I built for until I got serious.

I hear ya! Pushing 65 and this 'old dog' is really having a hard time remembering all the old tricks, much less learning new ones, though I don't believe it's the age so much as the ultra high mileage with too little routine maintenance. At least you don't have to wear contacts and glasses to read.

None of the duplexes can do justice down to 20 Hz in a HT app except possibly in a well sealed broom closet or one converted into a 20 Hz BLH, so a sub system is called for with the 604s tuned flat to around 40 Hz for an 80 Hz XO point. It's a pretty good tuning for spinning vinyl without the sub also if desired.

Using several relatively small subs positioned around the room to cope with its modes will go a long ways towards smoothing out the bass line: http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf

With that in mind, you cab's net Vb is about right for this tuning if you drive its woofer with SS or PP tubes as long as the driver's specs fall within the range of all the various ones I've accumulated for the 604. SETs will have too much output impedance, though damping the vent or maybe even sealed might make the combo work well enough depending on how high its impedance. A 4.5" diameter vent (or its equivalent area if square or rectangular) will be close enough if the baffle's 3/4" thick.

GM

[cradeldorf]

Thanks for the 'attaboy', but that's laying it on a little thick, don't you think? The pioneers of audio up to the latter day inventors take up all but the seats up in the nosebleed section. Doesn't leave much room for me and all the other advanced DIYers around the world, so we 'stand on their shoulders'.

Understood, there's a lot to know if you're serious about speaker system design, otherwise just build as big a cab as you can tolerate, tune the vents in-room and call it good enough. Worked well enough for me and for the friends, relatives I built for until I got serious.

I hear ya! Pushing 65 and this 'old dog' is really having a hard time remembering all the old tricks, much less learning new ones, though I don't believe it's the age so much as the ultra high mileage with too little routine maintenance. At least you don't have to wear contacts and glasses to read.

None of the duplexes can do justice down to 20 Hz in a HT app except possibly in a well sealed broom closet or one converted into a 20 Hz BLH, so a sub system is called for with the 604s tuned flat to around 40 Hz for an 80 Hz XO point. It's a pretty good tuning for spinning vinyl without the sub also if desired.

Using several relatively small subs positioned around the room to cope with its modes will go a long ways towards smoothing out the bass line: http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf

With that in mind, you cab's net Vb is about right for this tuning if you drive its woofer with SS or PP tubes as long as the driver's specs fall within the range of all the various ones I've accumulated for the 604. SETs will have too much output impedance, though damping the vent or maybe even sealed might make the combo work well enough depending on how high its impedance. A 4.5" diameter vent (or its equivalent area if square or rectangular) will be close enough if the baffle's 3/4" thick.

GM

I just feel as though you deserve more of an attaboy because you actually share your knowledge with the common folks. I just bought this Marantz receiver but now I'm thinking I should have went with something more designed for HT use with subwoofer outputs. I just redid the ports to 5.25 dia. in a 3/4 thick board. Not sure what the specs will be but bill has them at GPA so I'm betting they'll be in pretty good shape when I get them back. I'm also using their crossovers because That is my extent of knowledge at this point in time. Thanks again Greg.

[GM]

So either a 2 inch by 10.5 inch slot or a 5.25 dia circle would be the right size for the port...Right?

Not quite, box/vent scaling isn't quite so simple plus you apparently didn't factor in the Vb loss due to a rather large driver that further disproportions the vent scaling, i.e. you needed a smaller vent area to get the same tuning.

GM

[cradeldorf]

Not quite, box/vent scaling isn't quite so simple plus you apparently didn't factor in the Vb loss due to a rather large driver that further disproportions the vent scaling, i.e. you needed a smaller vent area to get the same tuning.

GM

I wish I hadn't gone all hacking holes before you replied last time. I think you said 4 1/2 and I had already made it 5 1/4. I tried plating (3/4 ply) the hole off completely but it sounded horrible and I'm pretty sure that's what makes surrounds destruct. At this point my only option would be to plate them over and put a 4 1/2 hole in the plate.