I'm looking for help modeling a bass reflex cabinet an Altec 421-8H? I want to build a pair of high efficiecy 2 way cabinets for my outdoor deck. I will paint the cabinets in deck paint and waterproof the cones. I know it's not good to spray old Altecs but I got these drivers years ago for very little money so I'm ok realizing they will have a limited life outdoors. I will also cover with waterproof covers when not in use. The cabinets need to vent to front.
Thank you,
Milkduds
Thank you,
Milkduds
What's your performance goal, i.e. being a MI driver (tiny Xmax/linear cone travel) it's best suited to be tuned somewhat higher than Fs (typically 1.56x) for high power apps.
Waterproof with what?
Waterproof with what?
Thanks GM. I was hoping you responded!
As far as a goal, this is for an outdoor system. Looks like about 48 hz based on your formula. Would see occasional party volumes so I may need to use a different woofer? I just have the 421s sitting idle. Don't want to use sub outdoors. One goal is relative high efficiency so I have option of using one of my low powered amps (10-20 watts).
As far as water proofing I I was just going to spray with a clear coat or I have ability to spray a CAB lacquer.
As far as a goal, this is for an outdoor system. Looks like about 48 hz based on your formula. Would see occasional party volumes so I may need to use a different woofer? I just have the 421s sitting idle. Don't want to use sub outdoors. One goal is relative high efficiency so I have option of using one of my low powered amps (10-20 watts).
As far as water proofing I I was just going to spray with a clear coat or I have ability to spray a CAB lacquer.
You're welcome! Kind of weary and already made a couple of errors elsewhere this evening, so don't hesitate to question if something's missing or doesn't 'ring true'.............
OK, then prosound alignment it is for max power handling* with box net volume (Vb) = measured Vas/1.44, so if using Altec's specs (~8.64 ft^3, though FWIW I always used Altec's 'jack o' trades' 8 ft^3) it will probably be misaligned somewhat after sitting idle for any extended time and it's specs may not go back to OEM, i.e. will have a lower Vas, making the cab under damped ('rings'), so if audible then critically damp the vent:
Click Test:
All that said, found my old measured specs, so in an attitude of 'don't fix what ain't broke', FWIW/YMMV my builds were ~8 ft ^3 net, ~49 Hz Fb with an 8" i.d. diameter ** x 0.75"/1.8-9 mm baffle thickness vent.
*simmed 15 W max below ~100 Hz = 110 dB/m ground plane and 30 W max above ~120 Hz = > ~116 dB/m ground plane, so can add up to 30/60 W if up against a house foundation, all in theory of course (don't remember what was measured way back when other than typical for small amatuer bands they were pushed well into guitar 'twang' mode to the point of 'spitting' the VCs out on occasion thanks to Phase Linear 400s!, so had metal screens to protect both driver and crowd 🙁)
**or 50.27" square or modestly rectangular (1:1.273) that the pioneers deemed = in performance
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......and all that said, for a lot smaller cab (SWAG = ~3 ft ^3 complete) tuned a little higher (~52 Hz) and handles up to 125 W > ~110 dB/42 Hz ramping up to 125 dB/200 Hz ground plane; a T/S max flat alignment is your mini neighborhood block party speakers and if folks want more (mid) bass they can bring the 'sub' systems! 😉
6" dia. x ~7.8" long vent
OK, then prosound alignment it is for max power handling* with box net volume (Vb) = measured Vas/1.44, so if using Altec's specs (~8.64 ft^3, though FWIW I always used Altec's 'jack o' trades' 8 ft^3) it will probably be misaligned somewhat after sitting idle for any extended time and it's specs may not go back to OEM, i.e. will have a lower Vas, making the cab under damped ('rings'), so if audible then critically damp the vent:
Click Test:
All that said, found my old measured specs, so in an attitude of 'don't fix what ain't broke', FWIW/YMMV my builds were ~8 ft ^3 net, ~49 Hz Fb with an 8" i.d. diameter ** x 0.75"/1.8-9 mm baffle thickness vent.
*simmed 15 W max below ~100 Hz = 110 dB/m ground plane and 30 W max above ~120 Hz = > ~116 dB/m ground plane, so can add up to 30/60 W if up against a house foundation, all in theory of course (don't remember what was measured way back when other than typical for small amatuer bands they were pushed well into guitar 'twang' mode to the point of 'spitting' the VCs out on occasion thanks to Phase Linear 400s!, so had metal screens to protect both driver and crowd 🙁)
**or 50.27" square or modestly rectangular (1:1.273) that the pioneers deemed = in performance
=========================
......and all that said, for a lot smaller cab (SWAG = ~3 ft ^3 complete) tuned a little higher (~52 Hz) and handles up to 125 W > ~110 dB/42 Hz ramping up to 125 dB/200 Hz ground plane; a T/S max flat alignment is your mini neighborhood block party speakers and if folks want more (mid) bass they can bring the 'sub' systems! 😉
6" dia. x ~7.8" long vent
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Coming back to this, something didn't 'ring true', i.e. in my haste I used the wrong HR Altec 421 master file (dual) to modify, though the cab alignments are correct from using original build notes or calculations for a single, so ignore all the power specs and I'll post the correct ones as time/mental alertness permits or just subtract 6 dB from each.
Very good. I do have a couple questions.
When I model 8 cu ft, I get a 2.3 dB peak at 53 hz and an F3 of 43 hz with port tuned to 49 hz like you said. I assume this small "bass hump" is what the old Altec users liked? Or this is a compromise to not needing a sub? I see the peak diminishes as you decrease box volume, if the Unibox Excel spreadsheet I found on the web is accurate of course.
Also, what drives installing such a large vent? It's considerably more than the min size.
I'm not questioning your knowledge..... just trying to learn. I remember the box you designed for me for a pair of 515-8Gs years ago worked very well but I have since converted to a true front loaded horns for my mid bass cabinets (main house system). The "click test" is something I have not seen! Thanks.
When I model 8 cu ft, I get a 2.3 dB peak at 53 hz and an F3 of 43 hz with port tuned to 49 hz like you said. I assume this small "bass hump" is what the old Altec users liked? Or this is a compromise to not needing a sub? I see the peak diminishes as you decrease box volume, if the Unibox Excel spreadsheet I found on the web is accurate of course.
Also, what drives installing such a large vent? It's considerably more than the min size.
I'm not questioning your knowledge..... just trying to learn. I remember the box you designed for me for a pair of 515-8Gs years ago worked very well but I have since converted to a true front loaded horns for my mid bass cabinets (main house system). The "click test" is something I have not seen! Thanks.
Also, the 421s I have were reconed years ago by some shop in Atlanta, so the seller told me. One speaker cone is stiff and the other loose but they voice coils measure fine so I'm sure there may be some T/S issues. They have been sitting for a few years. In fact I've never used them! One thing I don't like is the ribs on the back of the white basket flange. I assume these speakers must have been made for rear mounting which is a PITA. I may try and use a very thick gasket and front mount.
You're welcome!
Traditional Altec alignments boost the mid-bass same as prosound, so technically a bit under-damped due to Les Paul's original guitar amp monitor being the original Lansing Iconic that prosound is based on and lived on for many decades as the Lansing/Altec 612, 846 Valencia.
It's due to the large vent's greater acoustic efficiency and ideally s/b Av = Sd for max efficiency that the pioneer's demanded due to having so little power available plus driver protection down around/at the mandated Fb = Fs. If wanting to smooth it, then this is what 'critical damping' is for. 😉
Excel is an excellent program within its limitations, but ideally need to use Hornresp or similar all - in - one design programs once you move past basic alignments.
Sorry, don't remember, but glad you found them suited your performance needs for the intended app.
Pretty cool poor man's impulse response test by RCA's Harry Olson, or so I've been told.
Hmm, during my time the distributor sent them to Altec's S.E. repair shop in Andersonville, S.C. IIRC (have to dig out a receipt, though moot as the owner closed shop when Altec was sold).
In more recent years I'm only familiar with a long gone Marietta (Smyrna?) High End boutique where a local DIYer did repairs part time and if still active probably still holds 'court' on the JBL, Klipsch?, Tannoy? forum(s) though like just about every other name/place/date I no longer remember his name or TTBOMK have any surviving notes with it. 🙁
Yeah, the early ones used the old rear mount frames presumably because the soon to be 416-8B frame was prone to cracking (been there, done that 🙁), but a bastard wood rasp made short work of adding notches. 😉 Never tried a thick gasket because it needs to have a wood/whatever adapter ring, standard gasket for a proper solid mounting plus prefer to use a removable front baffle for its superior bracing/damping, relative ease of moving the driver with less potential for a 'tragic accident' moving such an unwieldy object, especially now in my weakened dotage. Can't see them, but the vent baffle is screwed on also for relatively quick experimentation.
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Very good. I think I have what I need to design the cabinet. I will make the cabinet as large as possible to fit my deck decor and get back to you. I've used Horn Response in the past but I'm by no means savvy with the program.
FWIW, I also own a pair of Altec Flamencos. I bought from the original purchaser who painted the cabinets white! I stripped the cabinets back to the orginal oak finish. The drivers are in perfect working order...... but I'd never drag those babies outside unless it was a very nice sunny Florida day!
FWIW, I also own a pair of Altec Flamencos. I bought from the original purchaser who painted the cabinets white! I stripped the cabinets back to the orginal oak finish. The drivers are in perfect working order...... but I'd never drag those babies outside unless it was a very nice sunny Florida day!
Copy that! Speaking of which, got any storm damage? For all the arm waving, etc., originally forecast'd impact on metro Hotlanta, still having the best weather this year!
GM - Looks like the largest I'd like to go is 5.5 cu ft in effective internal volume. Can you recommend a tuning freq and port dimensions for this volume?
Very good! I can live with that.
How critical is port location beyond normal clearances? I need to use a front port as I will need to locate cabinet close to wall (1.5") on some occasions. I also want the flexibility to move around on deck so I plan to use low profile casters.
How critical is port location beyond normal clearances? I need to use a front port as I will need to locate cabinet close to wall (1.5") on some occasions. I also want the flexibility to move around on deck so I plan to use low profile casters.
Vent/pipe end corrections based on location. Default program sims are k = 0.732, so if in one of the other locations, then easiest for me to start over, that or just accept a lower tuning.