my new 604 cabinets I'm building.

[cradeldorf]

I’m no fan of foam, but would only use open cell, otherwise the closed cell will reduce net Vb somewhat, but no clue how much. Also, it’s my understanding that it works best when spaced away from the walls, though don’t know how far, and any braces must be covered also; so hanging a full length ‘blanket’ of it diagonally across the cab seems the best solution overall.

Your cab’s internal dims falls within the acceptable room ratios, so I normally recommend using Altec’s, i.e. lining one wall, back and end opposite the vent with 1” acoustic fiberglass insulation or if polyfil stuffing [AKA damping] is preferred, starting with ~1.67x the fiberglass’s calculated lbs/ft^3 stuffing density and adjust more/less to ‘taste’. My SWAG is that this equates to a ~0.25 lbs/ft^3 polyfil stuffing density using MJK’s software.

GM

Hmmm since you say that I'm picturing a half circle of foam starting on the left side against the baffle and then making a giant u shape to the back of the cab and back to the right side of the baffle. Or I could do some 1" thick 2 x 4 acousical ceiling tiles mounted to the braces. Unfortunately I spent my allotted cabbage on those EV speakers for this paycheck. If I didn't have the car insurance man with his hand out I'd have an additional $250 to spend this paycheck but I don't. Might be another 2 weeks till I have any spare cash unless my refinancing loan goes through soon.

[GM]

Well, you could do it that way, though it's not what I meant. Visualize the top is off the cab, now lay a 'curtain' rod diagonally across two corners and hang a weighted floor length 'drape' from it...... In theory, my way won't damp quite as well, but then the object is to make a design that works well with minimal internal damping.

Acoustical ceiling tiles will reduce net Vb, but is a good way to both quell any eigenmodes and mass load the cab somewhat......

I see I forgot to include damping the inside of the top also if doing the 'blanket'......

Glad you have a paycheck, they're getting scarce in my locale......

GM

[cradeldorf]

Well, you could do it that way, though it's not what I meant. Visualize the top is off the cab, now lay a 'curtain' rod diagonally across two corners and hang a weighted floor length 'drape' from it...... In theory, my way won't damp quite as well, but then the object is to make a design that works well with minimal internal damping.

Acoustical ceiling tiles will reduce net Vb, but is a good way to both quell any eigenmodes and mass load the cab somewhat......

I see I forgot to include damping the inside of the top also if doing the 'blanket'......

Glad you have a paycheck, they're getting scarce in my locale......

GM

Thank's Greg, I knew what you were saying....I thought about it some more and thought maybe an upside down U might be more practical so the wave could reach the port on the back panel. It's not like it's permanent, lots of different things I can try.
Paychecks are getting scarecer and smaller here too. : ( Those rapist bastards. >: (

[cradeldorf]

Ok this is where I'm at with WinIsd.....Is there a way to change the white line to the shape I want? or is this just what I'm gonna get from my cabinet?

EDIT: If I change the box freq. I got the line to look more like I think it's supposed to.
The first pic and the last pic are the new 37.5 box freq. the second is the first one the program spit out 27.11 Is changing the box frequency what I'm supposed to do to work the program correctly?
Do I want to keep the white line between the 0 and -3db line for as long as I can without it going outside of either one? because if so then 37.5 was the magic number.

[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

[Altec Best]

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.

+1 This is what puts you a cut above IMO ! Always kind and generous with your time for some of us Folk's who are just looking to build a once in a lifteime "Stellar Speaker Project" !

[cradeldorf]

I agree, Greg you are the best defense in an all learning community. I'd hug you but your too far away...and being that your a dude...yeah it'd be kinda weird. I'll take your knowledge and use it to the best of my ability for my own personal use.
Thanks Bro.

[cradeldorf]

They're in the new cabs, Even though I don't have backs on them because I'm broke again I'm totally liking what I'm hearing. I have them shoved up against the wall but because there's a base molding along the floor they're actually about a half inch off the wall. The bass is very deep and strong. Just the way I like it. and it's like they have mid-range now before it was totally lacking compared to the lows and highs. I do have some scrap wood I could make some backs out of but they would be pieced together.

[mah]

Patience. Do it right when you can. Enjoy in the meantime.

[cradeldorf]

Thank's Mah, well it's about 6 am and I'm getting tired. I shot a little video of them with some zoolander on. My camera doesn't really capture the sound as good as it is live but it's the best I got. Someday they'll have backs on em.

Zoolander on Altec 604's with new 12Ft cab's.wmv - YouTube