my new 604 cabinets I'm building.

[GM]

I love how you force us to learn, it kinda feels like your a professor and were your pupils. It truly is a good feeling and as my dad used to say nothing worth earning is free. I have the winIsd at home on my puter so I'll fire it up and see if I can remember from the last time I tried using it. As always Thanks Greg.

That's what the Altec bulletin suggested for the 604? I haven't cut the ports yet, if you got a better suggestion.

You?re welcome!

Hmm, they say you can?t force a willing victim, but yeah, the longer I?ve been on-line the more I?ve made it my desire to expose folks to enough information for them to make a relatively informed decision about something that either is counterintuitive and/or has been subverted by the ?misinformation? distribution types, be they amateur or professional to [rightly or wrongly depending on your POV] protect their intellectual property, or worse, just plain mean spirited.

Please use the Pro alpha version at least for now as it has proven more accurate [assuming there?s been no recent updates to the basic version] and I haven?t taken the time to scope out /use V7.

This is a ?60s era modified version of a chart that dates back at least to the early ?50s when according to a RCA recording/broadcasting studio and control room design specs manual, the reference for a ?full range? studio or cinema sound mixing monitor was a 50-11,000 cps [Hz] ~flat BW; so a ~40 Hz tuning in a large cab driven with at least this low an Fs driver was a SOTA HIFI alignment for its time and a 75-7,000 cps response being considered adequate for orchestra and vocal groups, ergo up to a ~65 Hz alignment was what most consumer sound system designs were based on.

This is borne out if you do the math, as cone resonance increases, so does the chart?s recommended tuning [no high Q drivers tuned below Fs as T/S dictates] and by 65 Hz its tuning is ~65 Hz since back then the drivers couldn?t handle much power near its Fs due to having little usable linear cone excursion and presented a poor electrical power transfer to the high output impedance amps of the day.

Not too surprisingly, the HF design limit has been extended in step with recording advances since it?s not expensive to do and doesn?t increase the speaker?s bulk like lowering its useful LF BW does for a given system efficiency, so sadly, a ~40 Hz alignment still covers most mainstream recordings, but for SOTA HIFI it needs to extend to cover a few pipe organ symphonic recording?s 16 Hz or at least 20 Hz for a movie soundtrack and/or at least a concert grand piano?s 27.5 Hz lowest note.

With this in mind, the highest measured Fs duplexes need a separate sub system just to cover the piano and the lowest is marginal at best if not in an I.B. sealed alignment and due to their strong [low Qt], low linear excursion [Xmax] motors they typically need EQ plus some room gain to get them ~flat to this low a frequency at the listening position [LP].

So between you having mismatched drivers and not knowing their actual Fs, sealed + EQ may be your best choice overall.

For experimenting with vented though, you can easily choose a starting point using any program that ~accurately calculates the vent?s air speed with changing electrical power and choose a vent area that doesn?t exceed ~5 % vent mach [~17.2 m/s (56.5 ft/s)], then at least with WinISD Pro, select ?flanged both ends? to get the closest match-up to most of my real world results or use the ?two free ends? setting to probably ensure enough to cut off if doing measured fine tuning.

GM