Hi All (GM
),
My hopes and dreams (drama sells!) are to use GPA products to build a Stonehenge-ish/620 cab for the 604-8H III Rev. 2. My concerns are two-fold. I read more than one thread where someone beautifully and painstakingly built 9+ cu. ft. cabs for the 604's only to be wanting for more bottom end. For something of that size and scope, I really don't want to be left wanting more (I'm no bass-head). The other is the WAF. Ideally, i want to stick with the hardware but get the cab as small as possible to keep my other half in smiles too. I keep running into dead-ends, can someone refer me to the (arguably) best designed cab plans going at the moment for my plan? They will need to be thorough and complete enough so that any and all construction issues (suggestions)would be addressed within the plans. TIA
),My hopes and dreams (drama sells!) are to use GPA products to build a Stonehenge-ish/620 cab for the 604-8H III Rev. 2. My concerns are two-fold. I read more than one thread where someone beautifully and painstakingly built 9+ cu. ft. cabs for the 604's only to be wanting for more bottom end. For something of that size and scope, I really don't want to be left wanting more (I'm no bass-head). The other is the WAF. Ideally, i want to stick with the hardware but get the cab as small as possible to keep my other half in smiles too. I keep running into dead-ends, can someone refer me to the (arguably) best designed cab plans going at the moment for my plan? They will need to be thorough and complete enough so that any and all construction issues (suggestions)would be addressed within the plans. TIA
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Greets!
Well, these 'old tech' drivers had to be very efficient due to having only a few watts available to fill a cinema, but it comes at a high price in cab size to allow these very loosely suspended drivers 'to be all they can be' with the optimal size Vs power handling Vs peak SPL in today's T/S specs centric society is Vb [net volume] = Vas [compliance/Cms]/1.44, so based on published specs is ~329.63 L [11.65 ft^3]/1.44 = ~229.1 L [8 ft^3] tuned to actual in-cab Fs [not necessarily the same as free air Fs spec, which BTW is the same alignment Lansing/Altec has used for the 604 since inception, so nothing if not consistent over the decades, ie. 'if it ain't broke, don't fix it'.
The thing is though that it started out with a ~60 Hz Fs, which was below the bandwidth [BW] of all recording media of the day, so has crept downward to ~33 Hz in its current incarnation to at least cover the majority of recordings available in our now single digit Hz infrasonic society, consequently the cab is too small acoustically to make much bass down low at any appreciable SPL relative to the mid-bass on up.
In speaker cab alignments we're always trading driver reference efficiency for increased LF BW as shown in this basic vented alignment formula [Vb = 20*Vas*Qts'^3.3] that effective motor strength [Qts'] ~totally dominates Vb until Vas becomes very high, so as a simple frame of reference to find any driver's T/S max flat alignment, i.e. Fb [box tuning] = Fs, then Qts' = ~0.403 and Vb = Vas.
Qts' = Qts + any added series resistance [Rs]: mh-audio.nl - Home
From this we see that any lower Qts' will have a Vb = <Vas, tuned >Fs and any higher Qts' will be >Vas tuned <Fs [TTBOMK 27.5 ft^3 tuned to 27 Hz is largest built to date] and some form of EQ will be required to max out bass output with low Qts' systems such as the 604.
All this is 2pi space though, i.e. setting alone out in a billiard table flat, acoustically large field, so as we add some rigid/massive vertical boundaries to it the [mid] bass becomes more concentrated until it's max'd out in a corner, which in turn allows us to shrink the cab while maintaining the same tuning to get ~the same [mid]bass output.
So [I ask all this almost rhetorically], do you have two room corners and can do any room layout changes required to put custom fitted, triangular shaped cabs that preferably are at least 60" tall with 30" wide [diagonal] baffles?
Also, what will be the system's output impedance, i.e. how much series resistance [Rs] will there be to raise Qts as even this could wipe out all of the cab's size reduction and conceivably increase it to >Vas like happened with the 27.5 ft^3 'double wide' if driven with a matching impedance tube amp w/variable DF tone controls + tiny single strand wire like some folks prefer?
WRT complete shop drawings, not going to happen from me, I just provide the basic critical dimensions, suggested bracing, damping, though hopefully may change a bit over time and of course can ask questions/whatever here.
GM
Well, these 'old tech' drivers had to be very efficient due to having only a few watts available to fill a cinema, but it comes at a high price in cab size to allow these very loosely suspended drivers 'to be all they can be' with the optimal size Vs power handling Vs peak SPL in today's T/S specs centric society is Vb [net volume] = Vas [compliance/Cms]/1.44, so based on published specs is ~329.63 L [11.65 ft^3]/1.44 = ~229.1 L [8 ft^3] tuned to actual in-cab Fs [not necessarily the same as free air Fs spec, which BTW is the same alignment Lansing/Altec has used for the 604 since inception, so nothing if not consistent over the decades, ie. 'if it ain't broke, don't fix it'.
The thing is though that it started out with a ~60 Hz Fs, which was below the bandwidth [BW] of all recording media of the day, so has crept downward to ~33 Hz in its current incarnation to at least cover the majority of recordings available in our now single digit Hz infrasonic society, consequently the cab is too small acoustically to make much bass down low at any appreciable SPL relative to the mid-bass on up.
In speaker cab alignments we're always trading driver reference efficiency for increased LF BW as shown in this basic vented alignment formula [Vb = 20*Vas*Qts'^3.3] that effective motor strength [Qts'] ~totally dominates Vb until Vas becomes very high, so as a simple frame of reference to find any driver's T/S max flat alignment, i.e. Fb [box tuning] = Fs, then Qts' = ~0.403 and Vb = Vas.
Qts' = Qts + any added series resistance [Rs]: mh-audio.nl - Home
From this we see that any lower Qts' will have a Vb = <Vas, tuned >Fs and any higher Qts' will be >Vas tuned <Fs [TTBOMK 27.5 ft^3 tuned to 27 Hz is largest built to date] and some form of EQ will be required to max out bass output with low Qts' systems such as the 604.
All this is 2pi space though, i.e. setting alone out in a billiard table flat, acoustically large field, so as we add some rigid/massive vertical boundaries to it the [mid] bass becomes more concentrated until it's max'd out in a corner, which in turn allows us to shrink the cab while maintaining the same tuning to get ~the same [mid]bass output.
So [I ask all this almost rhetorically], do you have two room corners and can do any room layout changes required to put custom fitted, triangular shaped cabs that preferably are at least 60" tall with 30" wide [diagonal] baffles?
Also, what will be the system's output impedance, i.e. how much series resistance [Rs] will there be to raise Qts as even this could wipe out all of the cab's size reduction and conceivably increase it to >Vas like happened with the 27.5 ft^3 'double wide' if driven with a matching impedance tube amp w/variable DF tone controls + tiny single strand wire like some folks prefer?
WRT complete shop drawings, not going to happen from me, I just provide the basic critical dimensions, suggested bracing, damping, though hopefully may change a bit over time and of course can ask questions/whatever here.
GM
Attached a picture comparing common 604 cabinets, including an 11cuft MLTL (H59.5", W25.5", D18.5") with a port tuned to 28Hz. A wider / shallower cabinet (H=59.5", W=26.6" D=15.8") with the same cross section should have similar sound.
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Probably OT ..... but the sealed Altec-604 + ported JBL 2235H ...seems hard not to love....
The Altec 604-8H in a ported 5cuft volume has limited air-dampening, and can generate unnecessary large Xmax cone movement.
The Altec 604-8H in a sealed 5cuft volume (with absorption fiberglass lining the walls) models to -3db at 80Hz with a Qtc ~0.6, which often sounds dynamic(just right), but not as loose (for a 15" cone covering up to 1500Hz) as Qtc of 0.7 or above. From my big box room sims, baffle step droop peaks ~100Hz, so a clever crossover ~100Hz should allow a "simple and clean" drive signal for the Altec 604 cone - which also has 1500Hz responsibility.
The JBL 2235H has a low'ish Qts of 0.25, and in a 5cuft ported cabinet tuned to 33Hz produces excellent bass at 93db/watt. So, to avoid throttling down the Altec 604-8H dynamics, bi-amping is necessary. When placed around walls, a complex bass equalization is required for a flat response, so a bass amp with an INPUT equalizer(active is better than passive) is required so the amp directly drives the 2235H.
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Probably OT ..... but the sealed Altec-604 + ported JBL 2235H ...seems hard not to love....
The Altec 604-8H in a ported 5cuft volume has limited air-dampening, and can generate unnecessary large Xmax cone movement.
The Altec 604-8H in a sealed 5cuft volume (with absorption fiberglass lining the walls) models to -3db at 80Hz with a Qtc ~0.6, which often sounds dynamic(just right), but not as loose (for a 15" cone covering up to 1500Hz) as Qtc of 0.7 or above. From my big box room sims, baffle step droop peaks ~100Hz, so a clever crossover ~100Hz should allow a "simple and clean" drive signal for the Altec 604 cone - which also has 1500Hz responsibility.
The JBL 2235H has a low'ish Qts of 0.25, and in a 5cuft ported cabinet tuned to 33Hz produces excellent bass at 93db/watt. So, to avoid throttling down the Altec 604-8H dynamics, bi-amping is necessary. When placed around walls, a complex bass equalization is required for a flat response, so a bass amp with an INPUT equalizer(active is better than passive) is required so the amp directly drives the 2235H.
Attachments
Indeed! All docs unfortunately long gone along with the speakers, but my first online DIY Altec design back in '97 was a pair of [sealed] 604E MLTL with three 2235H tuned to ~27 Hz. With a TD corrected XO it was by all accounts the overall best speaker system anyone had auditioned.
For sure, with today's super wide range recordings/movie soundtracks, no way would I run one full range below ~80 Hz. This covers all music but the handful of men and pipe organs that can go below this point, so combined with our poor hearing acuity down low, just don't see the point unless in a severely limited SPL app where the bass needs to be rolled off to appease neighbors/whatever.
GM
Thanks you both so much for taking the time and weighing in. I'm new to the 'boards' so forgive much of this. I do feel like i'm a sophomore in HS listening to college professors at this point but, and correct me if I'm wrong, that you are both to one degree or another suggesting that the single driver, in a more confined design is a bit of a waste? Instead of attempting to squeeze more range out of the 604 with what really amounts to needing 10+cuft that I should consider x over to a sub in lieu of stuffing the 604 into a smaller box? Additionally, if i'm comprehending things, it sounds like perhaps I need to consider introducing something like what these fellas are using, the "dbx DriveRack PA2 loudspeaker management system" Altec Lansing Valencia: Improving a Classic - Great Plains Audio
Amp-wise I'm running a McIntosh MC275 MkV.
I'm really only wanting to keep it 2 ch so is my takeaway accurate, bark up a different tree?
Thanks so much again for your input.
Jay
Amp-wise I'm running a McIntosh MC275 MkV.
I'm really only wanting to keep it 2 ch so is my takeaway accurate, bark up a different tree?
Thanks so much again for your input.
Jay
Maybe the question is: Are you doing the build or having someone do it?
If the latter, GPA links to a vintage enclosure vendor in GA (iirc). We presume their experience would allow you to bypass the need for construction issues etc.
If you already have the drivers( I don't think you do), you might look for a defunct refrigerator or better: freezer to try them out in. For anything less than a (~35lb) 604, you might well get away with just the box (or washer/dryer/water heater box)... but a 604 would bring it crashing down without additional support.
IIRC historical cabinet drawings/plans can be found via the libraries of:
gpa site
lansing heritage site
altec users board
Perhaps part of the problem is that the very latest III from GPA doesn't seem to have a spec sheed available yet for it's t/s params. You might get close modelling with the II, but that's conjecure on my part. (A call to them might yield some details)
There are thousands of Altec 604 ported box speakers producing great sound to happy listeners. With a large cabinet, you will get good musical bass, but not the deep scary lows which a large Xmax subwoofer can push out with a large amplifier.
You can use a single amplifier driving both the Altec 604 in a sealed volume, and a musical woofer like the Altec 635 in a ported volume. You can build one shared box, or two separate boxes. You can find crossover schematics for 3-way monitors like the Urei 813.
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Google Troels Gravensen "the Loudspeaker" for an example of a modern 3-way design with classic appearance.
You can use a single amplifier driving both the Altec 604 in a sealed volume, and a musical woofer like the Altec 635 in a ported volume. You can build one shared box, or two separate boxes. You can find crossover schematics for 3-way monitors like the Urei 813.
----
Google Troels Gravensen "the Loudspeaker" for an example of a modern 3-way design with classic appearance.
Attachments
...unable to edit my previous as +30 min, but continuing:
...I have 8k's at present.
*The K's are seemingly maligned, so perhaps not representative.
These came in M600 cabs, which seem about 4.2 cuft. 'Small' and highest WAF thus.
You can probably find some for sale if you look hard enough.
'Soffit' mounted, (otherwise hemmed in by other big and massive square things, bookshelves, etc) they might do very well. I had them on the floor, against a wall but not tightly, and I EQ'd them.
They are presently in a different room, and in ~6 cuft 8154 cabinets, (tuned to ~37hz afaik).
This was surely an improvement in the new room, allowing to relax the LF EQ curve a bit.
* I digress for detail: However the 8154 are as-yet un-damped.
There is clearly a ~50hz null - which may be solved with damping or may just be a room mode to be dealt with.
Point is - K's (and thus GPA units, if length remained the same) will fit in 8000 series cabinets - which are more readily available, esp. towards your neck of the woods IME.
For 8000 series pics, look for the late 80's early 90's Altec PRO catalog. Lansing Heritage has one up - but it is missing about half the pages. I will scan mine someday and offer them.
** The 8154 and 8156 also happen to fit the width (perfectly) and depth (off by 1/8") of my fairly standard sized LP cubbies.
Due to the shallow baffle (FLH), they will not readilly fit in A7/A5 cabs without consternation at least, and almost certainly requiring modification to the rear panel.
...I have 8k's at present.
*The K's are seemingly maligned, so perhaps not representative.
These came in M600 cabs, which seem about 4.2 cuft. 'Small' and highest WAF thus.
You can probably find some for sale if you look hard enough.
'Soffit' mounted, (otherwise hemmed in by other big and massive square things, bookshelves, etc) they might do very well. I had them on the floor, against a wall but not tightly, and I EQ'd them.
They are presently in a different room, and in ~6 cuft 8154 cabinets, (tuned to ~37hz afaik).
This was surely an improvement in the new room, allowing to relax the LF EQ curve a bit.
* I digress for detail: However the 8154 are as-yet un-damped.
There is clearly a ~50hz null - which may be solved with damping or may just be a room mode to be dealt with.
Point is - K's (and thus GPA units, if length remained the same) will fit in 8000 series cabinets - which are more readily available, esp. towards your neck of the woods IME.
For 8000 series pics, look for the late 80's early 90's Altec PRO catalog. Lansing Heritage has one up - but it is missing about half the pages. I will scan mine someday and offer them.
** The 8154 and 8156 also happen to fit the width (perfectly) and depth (off by 1/8") of my fairly standard sized LP cubbies.
Due to the shallow baffle (FLH), they will not readilly fit in A7/A5 cabs without consternation at least, and almost certainly requiring modification to the rear panel.
You're welcome!
Well, yes, but like any machine/whatever design, you make it to best suit the needs of the app and based on your multiple seemingly conflicting goals from my POV, I opted for corner loaded to get the size down as much as practical while maintaining as much bass as practical, but like any compromise, there's trade-offs.
Not many 'free lunches' in audio system design, so you lose some of the 604's 'effortless' bass, micro details in the mids-up BW of the woofer due primarily to its huge Vas, low Mms, careful doping, the main things that sets the pioneer's woofers apart, i.e. they can't 'breathe'/'speak' freely in acoustically small cabs anymore than we can wearing very constricting clothing and no amount of digital dithering will change it, just at minimum increase thermal power distortion due to all the boosting down low.
Sweet! I had an original 275 for awhile, but switched to SS bi-amping and have never looked back, though IMNSHO should only use passives with PIO caps for tubes, though for most folk's hearing acuity, motor start caps comes closer to what the pioneers voiced speakers with than $$$ boutique PIOs.
The only other way to come close to your multiple seemingly conflicting goals from my POV is 604 on OB with separate 'sub' system that theoretically should be SS driven w/dbx XO, TD, etc., to get high damping with no real loss of the 604's critical phone BW's micro detail.
Unfortunately, this doesn't reduce system size much, if any and might make it larger since the 'sub' system ideally needs to be at least the same reference efficiency and maybe more if the room doesn't boost it enough to handle baffle step compensation [BSC]. Normally it would be multiple drivers/channel in one huge 'sub' centrally located or in singles and/or doubles strategically placed around the room with some up high at an odd harmonic to blend to the room's vertical eigenmodes [after Dr. Geddes].
GM
Right, a huge Altec aficionado, he's lived within a long walk from me for all the decades I've been here, but only learned about him recently and if all goes well will add all my designs I can remember to his catalog in the not too distant future.
Hmm, I've been led to believe the current specs listed are for the III series.
GM
Here's the GPA 604-8H-III specs:
http://greatplainsaudio.com/wp-content/uploads/2016/06/604_8H_III.pdf
There doesn't seem to be specs anywhere yet for the new Alnico 6048E on their page:
Alnico 6048E - Great Plains Audio
Home - Great Plains Audio
http://greatplainsaudio.com/wp-content/uploads/2016/06/604_8H_III.pdf
There doesn't seem to be specs anywhere yet for the new Alnico 6048E on their page:
Alnico 6048E - Great Plains Audio
Home - Great Plains Audio
a great analogy to refresh my perspective. thanks.
Is that: The 604 sealed and the 2235 as MLTL?
and: TD: time domain/aligned ?
...how far might my 2 GPA 416-8C get me in place of the 3 2235H?
I was hoping to KISS with the 604-8A XO's (maybe make copies with upgraded parts), but if it's suitable to fake it (get 16ohm phragm, then 416 and 604 LF in series to make 16) ...the system/amp might like the higher impedances. I tend to chase my tail playing with XO's so disinclined towards anything terribly complex. (this ultimately why the 828 system came down in favor of playing with the 604s)
OP (Jay) - if I am crowding your thread please do let me know and I'll bugger off and start anew. Don't want to drag this OT on you.
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You're welcome!
Correct, yes.
WRT peak SPL/'slam', not very since it has 2x + Xmax, power handling + a third driver. That said, dual 515B/channel has more than enough in the mid-bass and bass, corner loaded, and don't recall anyone walking away muttering anything about lack of 'slam'/'grunt'/'thump',/'rumble', etc., so dual 416s will come close plus have more bottom end.
"(get 16ohm phragm, then 416 and 604 LF in series to make 16)" ???
Actually, it's not Jay's, but 'theboogeydown' thread.
GM
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Good question! My SWAG is it started life as the 617-8A high end PA ceiling driver w/70V line transformer option, except now with a much better, larger HF horn, though still lacks enough HF extension for HIFI/HT apps due to its 1.4" exit throat, which combined with a 1.5 kHz XO point [actually a ~ 'on the money' point for best overall polar matching to a 12"] allows a very high power rating.
Consequently, a dedicated sub system is required for [deep] bass and a super tweeter compression horn [ST] to add top end 'air', which of course the full size vintage systems also ideally require; but with an HF horn that overly much shrouds/destructively interacts with the woofer, apparently causing its rather ragged HF response that ideally requires XOing the ST as low as practical, combined with a very pricey total system cost for the main 'privilege' of not taking up much room space, this puts it in a very competitive market where based on published specs, others observations, I'm convinced one can get as good or better an overall performance for less.
In short, in concept: most definitely! With the caveat that for the avid DIYer or even 3rd party customs, there's lots of other, [much] less expensive options, such as 'enhancing' over time as budget permits, an Eminence, Fane, etc., co-ax or even its new 15" 'full range' [FR] driver in whatever cab alignment that long term best overall meets the needs of the intended app.
GM
Thanks GM!
I think he signed it 'Jay' above.
The XO comment explained: I was proposing that if I match the HF and LF impedances by wiring the LF in series (16 ohm), and replacing the HF 8 ohm diaphram with a 16 ohm, that the XO points for the N604-8A would remain the same (as with the existing factory 8/8 arrangement). Perhaps that simplistic approach only applies to low order XO's (or specific types of low order XO's). I realize it would also not account for disparity presented by the sealed vs MLTL sections.
I'm putting the cart ahead of the horse though. I should first start a separate thread about the cabs themselves.
Of course if I had the 604 sealed,
I think he signed it 'Jay' above.
The XO comment explained: I was proposing that if I match the HF and LF impedances by wiring the LF in series (16 ohm), and replacing the HF 8 ohm diaphram with a 16 ohm, that the XO points for the N604-8A would remain the same (as with the existing factory 8/8 arrangement). Perhaps that simplistic approach only applies to low order XO's (or specific types of low order XO's). I realize it would also not account for disparity presented by the sealed vs MLTL sections.
I'm putting the cart ahead of the horse though. I should first start a separate thread about the cabs themselves.
Of course if I had the 604 sealed,
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