Great Plains Audio Stonehenge V build
In years past I owned a pair of Altec A5, and despite their shortcomings the things they did very well were dynamics, efficiency, and the way they loaded a room with sound. Having read about Great Plains Audio (GPA) of Oklahoma city making new Altec Lansing 604-8H-III two way I ordered a pair and built a Stonehenge V enclosure, decided to post my build for those who are interested. By the way if you have any questions about GPA and their products give them a call, excellent people to deal with a true American company.
In years past I owned a pair of Altec A5, and despite their shortcomings the things they did very well were dynamics, efficiency, and the way they loaded a room with sound. Having read about Great Plains Audio (GPA) of Oklahoma city making new Altec Lansing 604-8H-III two way I ordered a pair and built a Stonehenge V enclosure, decided to post my build for those who are interested. By the way if you have any questions about GPA and their products give them a call, excellent people to deal with a true American company.
Thanks for looking, over the years I have owned and built about every kind of speaker, of which my wife say’s is an obsession, but I call it my passion. So my comments on results of the 604-8H will be compared to my current reference Magnepan 1.7. The Maggies are very good at imaging if set up properly which takes room tuning, and after they break in are smooth almost to the point of obscuring detail but overall they are a very good speaker. How does the GPA 604 compare, first the dynamics of live music which so many of the modern speakers do not do, second detail if you want to hear and understand the backup singers get a pair of monitors like the 604. The midrange where the music lives is very good the bass is solid down into the 40hz, I am currently also using my sub, but I can live without it. I do not notice a problem with baffle step which is probably due to size of speaker baffle. Imaging very good but there is a sweet spot which can be narrow probably due to the 15in running up into the 1200 hz, but is no worse than a lot of dynamic speakers. The image is in front of the speakers but that is most likely due to room placement of which I have not played around with yet. Yes sometimes they have a horn signature but less than a set of horn speakers I built using BMS drivers. I have not played with crossover settings, set them at recommended settings and will play around with the crossover after a couple hundred hours on the speakers. These are fairly expensive drivers, and are a real beast at 38 pounds each, and very well built, so be careful when you handle them. At this point these are one of the best speakers I have owned and if you can build your enclosures and have the room, because they are big, you are not going to be disappointed. I am currently running them with Benchmark Dac and amp, will drag out my Primaluna tube gear this week, they work very well with the SS gear, and will see how they do with the tubes, I expect them to reflect the electronics signature.
'Preaching to the choir' 😉, though lifelong DIYer, so have limited my knowledge of consumer speakers to just [sometimes long] auditions and prefer my own cab alignments to the various necessarily compromised Altec's.
Re the 604-3, 'we' for the most part was disappointed that Bill didn't go back to a modern version of the early optimal ~1200 Hz XO horn, so still has the small horn 604's major flaw.
GM
Re the 604-3, 'we' for the most part was disappointed that Bill didn't go back to a modern version of the early optimal ~1200 Hz XO horn, so still has the small horn 604's major flaw.
GM
Great thread! Your speakers are beautiful!
I am planning to build a similar pair using a set of 604e with N-1500 A crossovers. In my case the 604e are 15" rather than 16" and I'm considering setting them on a double-front so they are flush to the front panel and screwed into the inner piece of the two fronts.
Now that you have finished yours and lived with them for a while; do you have any suggestions? Anything you realized that is important not to compromise, or maybe something you would do different? Nothing beats experience. It is my intent to use 3/4" Baltic Birch and I think I will try my hand at veneering them.
I see you have a "real" crossover; it looks completely different from the N-1500A.
I am planning to build a similar pair using a set of 604e with N-1500 A crossovers. In my case the 604e are 15" rather than 16" and I'm considering setting them on a double-front so they are flush to the front panel and screwed into the inner piece of the two fronts.
Now that you have finished yours and lived with them for a while; do you have any suggestions? Anything you realized that is important not to compromise, or maybe something you would do different? Nothing beats experience. It is my intent to use 3/4" Baltic Birch and I think I will try my hand at veneering them.
I see you have a "real" crossover; it looks completely different from the N-1500A.
Attached a picture comparing common 604 cabinets, including an 11cuft MLTL (H59.5", W25.5", D18.5") with a port tuned to 28Hz.
=====Sealed Altec 604 + ported JBL 2235H woofer========
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 sounds dynamic and tight for the 14" cone covering up to 1500Hz. From my big box room sims, baffle step droop peaks ~100Hz, so a crossover ~100Hz should allow a simple and clean drive signal for the sealed Altec 604H.
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 is required so the amp directly drives the 2235H.
=====Sealed Altec 604 + ported JBL 2235H woofer========
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 sounds dynamic and tight for the 14" cone covering up to 1500Hz. From my big box room sims, baffle step droop peaks ~100Hz, so a crossover ~100Hz should allow a simple and clean drive signal for the sealed Altec 604H.
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 is required so the amp directly drives the 2235H.
Attachments
Smooth bass in a modest volume(6.7cuft) cabinet: Higara 604-Alnico cabinet uses an MLTL alignment with a bottom port which exhausts into large Onken-style bottom slot vents. Higara 604-Alnico measures similar to an extended bass shelf alignment.
Attachments
JBL used less extended 2215H for UREI 813C (604 variant) which supposed to be soffit on the wall, and my 813C sitting on the floor requiring some bass EQ.
I recently replaced 2215H with vintage alnico woofer, and I'm pretty surprised to hear very positive effect which I didn't really expect. I bought those woofers for another project, but decided to use them for 813C. The problem is, those alnico woofers have less bottom end than 2215H, so I'm now seriously thinking adding subwoofers to those 2x15" monsters...
Baffle dimension.
Regarding the sealed five cu ft box for an Altec 604, what are the baffle dimensions overall, and where is the 604 mounted? Is this a box you have built and used as described?
Regarding the sealed five cu ft box for an Altec 604, what are the baffle dimensions overall, and where is the 604 mounted? Is this a box you have built and used as described?
In response to a diyAudio thread, I noted that the Altec 604-8H models to -F3=40Hz in a ported 5cuft volume, and if the port was later plugged it models to -F3=80Hz with Qtc~0.6 ---- desirable for a large area cone. This comment was meant to show the flexibility of a 5cuft cabinet which the OP was considering.
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The Altec StoneHedge-III and Hiraga 605-Alnico cabinets have about 5cuft of free internal volume after speaker+bracing+port have been figured in. There are detailed plans(too large to post) for the Altec StoneHenge-III . Visit Jeff Markwart's Corner website for this pdf plus more Atec knowledge.
Altec Stonehenge III (3577A) Cabinet plans
Altec StoneHenge-III
H44"+ legs,W18.75",D17.25“
Hiraga 605-Alnico
H41”,W20.1”,D18.1”
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The Altec StoneHedge-III and Hiraga 605-Alnico cabinets have about 5cuft of free internal volume after speaker+bracing+port have been figured in. There are detailed plans(too large to post) for the Altec StoneHenge-III . Visit Jeff Markwart's Corner website for this pdf plus more Atec knowledge.
Altec Stonehenge III (3577A) Cabinet plans
Altec StoneHenge-III
H44"+ legs,W18.75",D17.25“
Hiraga 605-Alnico
H41”,W20.1”,D18.1”
Note too that some folks refer to the SH-V as a MLTL, but it's actually a BR since the 1/4 WL action only generates a reflection to the vent causing a broadband notch in the response, so to make it a MLTL, relocate the vent centered down at 37" [i.d.] or lower from the top.
GM
GM
StoneHenge V build update, some of the things I have done since the original build. The cabinets were very live particularly on the sides, most likely due to the cheap plywood I could find at where I live. So I lined the inside between the braces with 1/2in plywood in a constrained layer type of construction and have lined the inside with foam acoustic tile. This has cleaned up the upper bass and midrange, but the lower bass (80hz down) is not as lively as before, but so far It has been a good trade off. If I were building a new cabinet with the same available plywood, I would still use two ¾ plywood glued up for front and recess the speaker as shown on original plans. But use ¾in plywood and glue ½ in or ¾ in plywood to all side and back panels, these are big enclosures so weight plays a factor. And also add additional and heavier bracing the other thing I would do is support the back of the drivers, I talked to GPA and they didn’t feel it was necessary but these are a beast of a driver at 38 pounds each. This is something I think I will go back in and do once I determine how to maintain a solid mount. I would like to try a MLTL cabinet but haven’t found any one that has built one and the results, plus I’m getting lazy. As to the double wall and bracing my speakers are at around 8 to 10 feet to listening position and if you are seated further away the panel resonance may not be a problem. Also the drivers require more break in than what I expected, so give them time to come on to song. If any one has any experience on MLTL for the altec’s please let me know.
MLTL Cab Plans For GPA 604-8H-III
This man swaps baffles for 604 or 'bad to the bone' multiway. Vents are down at the bottom sides IIRC: GM-416-8B MLTL Corner Cabinet
This one isn't quite long enough to be a proper MLTL AFAIK, but has the motor brace I recommend[ed], bottom firing vent IIRC: 6moons audio reviews: Stephæn's Altec 604 Dream Speaker
There's others from earlier times, but no longer have links and/or were posted on long gone forums not in the web archive.
GM
This man swaps baffles for 604 or 'bad to the bone' multiway. Vents are down at the bottom sides IIRC: GM-416-8B MLTL Corner Cabinet
This one isn't quite long enough to be a proper MLTL AFAIK, but has the motor brace I recommend[ed], bottom firing vent IIRC: 6moons audio reviews: Stephæn's Altec 604 Dream Speaker
There's others from earlier times, but no longer have links and/or were posted on long gone forums not in the web archive.
GM
I was in touch with Stephaen and Pete about buying their planset a couple of years ago, until I realized that my current living situation couldn't possibly fit them. Still tempted to buy the plans, as I do have a place in the country and hopes/dreams for a barn where they would be just right.
How do Stephaen's differ acoustically from the Stonehenge's?
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Life-like bass response is a function of cab size/loading, so the 'V' digs deeper, 'fuller'. They are also wider, so will sound a bit 'fuller' in the critical lower mids speech BW, so less acoustic efficiency is traded to get them tonally balanced to the HF [AKA baffle step compensation/BSC], which I assume was done, so actual difference would be the 'V' playing louder/deeper for a given input power.
These are referenced as being the same. Sound horrible [they sing like they're tone deaf to me], but I only have whatever sound-card is in a basic HP Workbook + cheap BestBuy headphones on sale and likely just a poorly done video since some youtube sound quite nice and indicative of the systems I'm familiar with: YouTube
Hmm, I can't comment about Pete's design, though led to believe it's basically Jay's, the one I did. Regardless, FWIW: Another 604 MLTL build (ping GM)
This is Jay's, which appears to be smaller, but between all my sims, correspondence in a damaged HD combined with failing memory, just not sure what's what anymore: B]https://www.flickr.com/photos/515b/4380274553[/B]
Bottom line with drivers with vintage specs designed for high output impedance and/or horn loaded systems is that there's no such thing as too large [Vb] or too wide [baffle], just a point of diminishing returns like any modern driver, i.e. Vb = Vas, Qts' = ~0.403, Fb [tuning] = Fs, ~38" wide baffle.
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
In short, for a basic stereo system I always recommend the largest cab one can tolerate/afford and it is what it is.
GM
These are referenced as being the same. Sound horrible [they sing like they're tone deaf to me], but I only have whatever sound-card is in a basic HP Workbook + cheap BestBuy headphones on sale and likely just a poorly done video since some youtube sound quite nice and indicative of the systems I'm familiar with: YouTube
Hmm, I can't comment about Pete's design, though led to believe it's basically Jay's, the one I did. Regardless, FWIW: Another 604 MLTL build (ping GM)
This is Jay's, which appears to be smaller, but between all my sims, correspondence in a damaged HD combined with failing memory, just not sure what's what anymore: B]https://www.flickr.com/photos/515b/4380274553[/B]
Bottom line with drivers with vintage specs designed for high output impedance and/or horn loaded systems is that there's no such thing as too large [Vb] or too wide [baffle], just a point of diminishing returns like any modern driver, i.e. Vb = Vas, Qts' = ~0.403, Fb [tuning] = Fs, ~38" wide baffle.
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
In short, for a basic stereo system I always recommend the largest cab one can tolerate/afford and it is what it is.
GM
Thanks for the MLTL information, after looking it over I think will stay with the S.H. V or what I’ve got. The front of my speakers are typically around 3 feet from back wall and image very good, but as I have mentioned they have a fairly small sweet spot. The resonant frequency (fb) of both cabinets are 35 hz as measured with woofer tester 3 with good peaks on either side so I get good solid response to 40hz without any problem. I am going to get off my duff and build a rear support brace.
JM
JM
