Nice work JonJin
I'm possibly embarking on something similar , also a bit inspired by Lynn's thread.
I've also ordered AH-425 from Martin, but am intending ( fingers crossed they don't go up in price any more ...) to get a pair of GPA 288-H , and prob use T90A tweeters after a quailified thumbs-up from Romy .
I have Supravox 285GMF at my disposal currently ( loaned ) and may do an Onken/Jensen for them if appropriate .
I intend to bi-amp bass though - run mids and uppers from 2A3 or 45 SE , but use Gain clone or Pass ss amp for bass, guidance there provided by a friend Jono Noble in S.A.
Interested to see how you get on .
Mark
I'm possibly embarking on something similar , also a bit inspired by Lynn's thread.
I've also ordered AH-425 from Martin, but am intending ( fingers crossed they don't go up in price any more ...) to get a pair of GPA 288-H , and prob use T90A tweeters after a quailified thumbs-up from Romy .
I have Supravox 285GMF at my disposal currently ( loaned ) and may do an Onken/Jensen for them if appropriate .
I intend to bi-amp bass though - run mids and uppers from 2A3 or 45 SE , but use Gain clone or Pass ss amp for bass, guidance there provided by a friend Jono Noble in S.A.
Interested to see how you get on .
Mark
Very interesting and close to what I've done. Maybe we can compare notes?
Anyways, been busy with the woodworking the last few days and some progress report.
Side vents glued on.
Bottom, back and sides now stuck on. Top has not been fixed yet. Will have to leave overnight now. Decided to glue and screw in the end. Using wood polyurethane glue which is really useful as it also makes a seal. The screws are self-tapping but the way I did was to make the holes first which then acts to align the pieces together.
Cleats put in and batten at the rear corners as per the plan. Also some sealant added to some areas where there were gaps. Build wise, they are not millimetre perfect but the dimensions are correct and the joints are sturdy so I am quite happy.
Almost there... front fits like a glove. Bolts screwed in with pronged nuts on the batten.
Altec 414Z Bass (Alnico)
Just need to wait for the lambswool wadding now.
JJ
Anyways, been busy with the woodworking the last few days and some progress report.
Side vents glued on.
Bottom, back and sides now stuck on. Top has not been fixed yet. Will have to leave overnight now. Decided to glue and screw in the end. Using wood polyurethane glue which is really useful as it also makes a seal. The screws are self-tapping but the way I did was to make the holes first which then acts to align the pieces together.
Cleats put in and batten at the rear corners as per the plan. Also some sealant added to some areas where there were gaps. Build wise, they are not millimetre perfect but the dimensions are correct and the joints are sturdy so I am quite happy.
Almost there... front fits like a glove. Bolts screwed in with pronged nuts on the batten.
Altec 414Z Bass (Alnico)
Just need to wait for the lambswool wadding now.
JJ
Ahh, thats very cool, with Azure waveguides
Those are the AH-550, right...its what I will use too, so Im happy to hear you like them
😎
Those are the AH-550, right...its what I will use too, so Im happy to hear you like them
😎
Azurahorn 425 actually. They sound sublime and throw the music into the room ever so gracefully. No honkiness that I can detect anyways.
JJ
JJ
jonjin said:
Strange, I dont see AH-425 anywhere on Martins site...is it a modified or new model 😕
New model commissioned especially for the Altec/GPA 288, incorporating the 8-degree internal flare of the 288 as an integral part of the overall horn profile. Unlike the larger Azurahorns, the AH-425 (and AH-550) fits in an Australian Post box, so shipping is much less expensive than UPS or FedEx International.
Lynn Olson said:
Ahh, thanks, thats a really nice information...had to read your post twice before realising you were answering my question about AH-425/550
I take it the Altec/GPA 288 is a GPA renovated vintage Altec...ahh, yes, found it 🙂
tinitus said:
To my understanding, the GPA drivers are newly manufactured using the original Altec tooling, not renovated vintage. Great Plains Audio doesn't use the Altec name on their products, though, because that name is now owned by Plantronics, Inc.
Gary Dahl
Not only the original tooling, but some of the original assemblers as well. The Altec plant and repair facility was moved to Oklahoma after the Los Angeles plant was damaged in an earthquake and it was not cost-effective to rebuild it. When the Altec name was sold to a Taiwanese car-radio company (Sparkomatic), a group of employees decided to start up Great Plains Audio in the same city they'd been working in for several decades. Since there were more than 10,000 A2, A4, A5, and A7 theater speakers in the field by the mid-Seventies, there has been plenty of repair and rebuilding business to keep them busy. (JBL took over the theater speaker business in the mid-Eighties as a result of Altec failing to submit a set of sample speakers to the THX group of Lucasfilm, thus no THX certification for Altec.)
The difference between GPA and a number of latter-day "audio-revival" products is the unbroken continuity of employees, build sequences, suppliers, and unwritten know-how. I've worked in manufacturing myself, and much of the detailed how-to-build-it is never written down, or documented by the engineering staff. This is the part that is very hard to duplicate after the original staff has retired and scattered to the four winds.
The difference between GPA and a number of latter-day "audio-revival" products is the unbroken continuity of employees, build sequences, suppliers, and unwritten know-how. I've worked in manufacturing myself, and much of the detailed how-to-build-it is never written down, or documented by the engineering staff. This is the part that is very hard to duplicate after the original staff has retired and scattered to the four winds.
Hey JJ
Nice to see that coming together .
Looks like we're going down a very similar road here. I have the AH-425's on order from Martin . Just getting the funds together to put in an order for 288-H and 414-8C from GPA . I was pricing up wood yesterday . 'Birch throughout' 25mm for 92 quid a sheet, 2 sheets required .....aaarg !
Did you go with the petit Onken design as per SP (1993 ) or did you try some tweaks ?
I've been debating a number of options for bass but have decided to cut losses and get going with something, and the Onken has got to be worth hearing !
I need to do some homework regarding Lynn's advice on alignments on the other thread . It's borderline as to whether I can get all the wood from 2x 8'x4' sheets .
I have a friend who's ready to get going on the construction for me - he has a proper workshop with pro-quality saws , routers etc and did a great job on the Ariel Mk.6's about 5 years ago .
So you already have the drivers and horns - what do you think of the tonal qualities ?
What kind of music do you listen to ?
Cheers
Mark
Nice to see that coming together .
Looks like we're going down a very similar road here. I have the AH-425's on order from Martin . Just getting the funds together to put in an order for 288-H and 414-8C from GPA . I was pricing up wood yesterday . 'Birch throughout' 25mm for 92 quid a sheet, 2 sheets required .....aaarg !
Did you go with the petit Onken design as per SP (1993 ) or did you try some tweaks ?
I've been debating a number of options for bass but have decided to cut losses and get going with something, and the Onken has got to be worth hearing !
I need to do some homework regarding Lynn's advice on alignments on the other thread . It's borderline as to whether I can get all the wood from 2x 8'x4' sheets .
I have a friend who's ready to get going on the construction for me - he has a proper workshop with pro-quality saws , routers etc and did a great job on the Ariel Mk.6's about 5 years ago .
So you already have the drivers and horns - what do you think of the tonal qualities ?
What kind of music do you listen to ?
Cheers
Mark
Seems a whole new world is opening in front of me, very exciting
I hope its ok to ask a small ot question
If I found a 288 driver, in good working condition, should I keep it in its original state, or would it in any case be better to have it renovated by GPA
If renovation would be needed it could become quite costly with postage and all
I hope its ok to ask a small ot question
If I found a 288 driver, in good working condition, should I keep it in its original state, or would it in any case be better to have it renovated by GPA
If renovation would be needed it could become quite costly with postage and all
414 odds
Tinnutus , I don't think I can help on your question , except that I'm sure GPA would do an excellent job . It's your call really, I don't know how the drivers look .
JonJin :
I'm getting very different numbers on the T/S data for original 414-8C and 414-8B :
http://www.rdrop.com/~billmc/speakers
I also found an excel Onken calculator from reVintage ( Lars ) somewhere , and using the data I got from GPA on the 414-8C gives me a very strange box with about 88L and 60cm vent lengths , which doesn't sound practical . It certainly looks nothing like the Petit Onken suggested in SP .
The data for Supravox 285GMF when calced in Lars' spreadsheet look a lot more like the Supravox-Jensen plans, that's for sure .
What params did you use for your 414-Z's ?
Mark
Tinnutus , I don't think I can help on your question , except that I'm sure GPA would do an excellent job . It's your call really, I don't know how the drivers look .
JonJin :
I'm getting very different numbers on the T/S data for original 414-8C and 414-8B :
http://www.rdrop.com/~billmc/speakers
I also found an excel Onken calculator from reVintage ( Lars ) somewhere , and using the data I got from GPA on the 414-8C gives me a very strange box with about 88L and 60cm vent lengths , which doesn't sound practical . It certainly looks nothing like the Petit Onken suggested in SP .
The data for Supravox 285GMF when calced in Lars' spreadsheet look a lot more like the Supravox-Jensen plans, that's for sure .
What params did you use for your 414-Z's ?
Mark
Ok, there are many links to spreadsheets , almost all of which are dead . I did find one courtesy of Lars (reVintage ) from last year , which I think I understand.
Now , as I understand it, the typical Onken is 4th-order Butterworth , and this corresponds to the n=6.34 parameter , right ?
And Lynn is suggesting on his Ariel thread to go for 4th-order Bessel/Gaussian, which Lars suggests in a thread elsewhere ( AA Hi-eff-speak) is just a case of replacing 6.34 by 4.5 ?
Unfortunately this does screw up the box dimensions and vent length relationship which becomes impractical, plus it takes about 9Hz off the bass extension . Hmmm...
MJ
Now , as I understand it, the typical Onken is 4th-order Butterworth , and this corresponds to the n=6.34 parameter , right ?
And Lynn is suggesting on his Ariel thread to go for 4th-order Bessel/Gaussian, which Lars suggests in a thread elsewhere ( AA Hi-eff-speak) is just a case of replacing 6.34 by 4.5 ?
Unfortunately this does screw up the box dimensions and vent length relationship which becomes impractical, plus it takes about 9Hz off the bass extension . Hmmm...
MJ
The large format drivers were almost exclusively used for prosound apps, so If it's a later ferrite motor, then normally all that's needed is a new diaphragm, so best to just assume it needs one, which you can either install yourself or get a local prosound re-coner to do. If you get the older AlNiCo units, then best to assume it needs both a diaphragm and a de-magging, re-zapping, which you may/may not be able to get done relatively close to home anymore. All things considered then, unless you get lucky it seems to me the best bang/buck is buying new GPA.
All that said, my first and only pair of large format drivers were Altec refurbished 288Bs on tar filled 805 multi-cells. Absolutely front row center, 'you are there' mids/lower treble driven with a Mac 275 (tube) in the ultra large room I was fortunate enough to have in my youth, but higher up, no amount of acoustic and electronic EQ I tried worked well enough for mine or wife's then keen hearing, so a number of DIY super tweeter horns were tried, but I finally gave up since I couldn't quite get them to blend completely, so worked a trade with the local prosound retailer for a pair of new 511B/808-8A and two aluminum diaphragms to turn the latter into 'HIFI' 802Ds.
Now I had a much more extended, coherent BW once EQ'd, but some of the critical mids 'body' was gone which at the time we thought an acceptable trade-off, though like a low level headache it ate away at me. To paraphrase the late Dr. King, once you've been to the 'mountain', there's no accepting less if there's another way, so later when I wound up with another pair of 511/808s in a trade, I mounted them on top and once rolled off and all the impedance mismatches were accounted for in the XO I now had all the low end sonic advantages of the 805 with all the high end of the smaller horn/driver plus an even better in-room response due the its changed polar response.
If I had access to today's relatively inexpensive adjustable digital XO/EQ/TD controllers 35-40 yrs ago, maybe I could have dialed in the 805s and/or the super tweeters and never bothered to try the stacked 511s, but for folks who only have access to the generally much less expensive Altec/whatever small format components and/or want to DIY the horns, it's for sure my choice if I were to ever again build a multiple separate horn system, though with today's electronics, a true super tweeter to improve the HF power response can be seamlessly blended in for those that feel the need.
GM
All that said, my first and only pair of large format drivers were Altec refurbished 288Bs on tar filled 805 multi-cells. Absolutely front row center, 'you are there' mids/lower treble driven with a Mac 275 (tube) in the ultra large room I was fortunate enough to have in my youth, but higher up, no amount of acoustic and electronic EQ I tried worked well enough for mine or wife's then keen hearing, so a number of DIY super tweeter horns were tried, but I finally gave up since I couldn't quite get them to blend completely, so worked a trade with the local prosound retailer for a pair of new 511B/808-8A and two aluminum diaphragms to turn the latter into 'HIFI' 802Ds.
Now I had a much more extended, coherent BW once EQ'd, but some of the critical mids 'body' was gone which at the time we thought an acceptable trade-off, though like a low level headache it ate away at me. To paraphrase the late Dr. King, once you've been to the 'mountain', there's no accepting less if there's another way, so later when I wound up with another pair of 511/808s in a trade, I mounted them on top and once rolled off and all the impedance mismatches were accounted for in the XO I now had all the low end sonic advantages of the 805 with all the high end of the smaller horn/driver plus an even better in-room response due the its changed polar response.
If I had access to today's relatively inexpensive adjustable digital XO/EQ/TD controllers 35-40 yrs ago, maybe I could have dialed in the 805s and/or the super tweeters and never bothered to try the stacked 511s, but for folks who only have access to the generally much less expensive Altec/whatever small format components and/or want to DIY the horns, it's for sure my choice if I were to ever again build a multiple separate horn system, though with today's electronics, a true super tweeter to improve the HF power response can be seamlessly blended in for those that feel the need.
GM
Thank you, even more to think about...I guess hifi never gets easy that way, and probably one reason why we do it 🙂
IslandPink said:
I'm using the 414Z and just used the Petite Onken. I'm not really technical minded so just went ahead and built according to the diagram. Very difficult to give listening impressions as I've only got one side built and no wadding. I was tempted enough to give it a listen but to be honest it sounded pretty awful so I don't really want to pass judgement yet before it's finished. My wadding should arrive sometime during the week so hopefully I should be able to post some constructive thoughts after that.
FWIW, I couldn't get the Petite Onkens to fit onto 2 8*4 sheets. I actually gave the measurements to AvonPlywood and they did a great job cutting it for me... down to the milimeter. I can wholeheatedly recommend them. I think they would be rather surprised if another person came along asking for the same thing! I did get some funny looks when I told them what it was for 🙂
JJ
Re: 414 odds
It's designed based on either being driven by a high output impedance amp and/or considerable series resistance which is true for many HE drivers and all low Vas units I've simmed, so if a SS or low PP amp is used, then some BSC is required to tonally balance it over a wide BW. Also, the vents generate considerable pipe harmonic distortion well into the mids which apparently many folks find euphonic to some extent, so they may require some damping to fine tune them to get a more accurate/'dry' presentation. Anyone preferring the latter type of response is better off with a single large vent MLTL, ML-horn, or ML-TQWT IMO and if it's the industrial chic 'look' of the Onken you want, vent it out the back or bottom and put fake vents on the baffle (been there, done that. 🙂).
GM
IslandPink said:
It's designed based on either being driven by a high output impedance amp and/or considerable series resistance which is true for many HE drivers and all low Vas units I've simmed, so if a SS or low PP amp is used, then some BSC is required to tonally balance it over a wide BW. Also, the vents generate considerable pipe harmonic distortion well into the mids which apparently many folks find euphonic to some extent, so they may require some damping to fine tune them to get a more accurate/'dry' presentation. Anyone preferring the latter type of response is better off with a single large vent MLTL, ML-horn, or ML-TQWT IMO and if it's the industrial chic 'look' of the Onken you want, vent it out the back or bottom and put fake vents on the baffle (been there, done that. 🙂).
GM
Hmmm
Ok, thanks for the advice chaps. Feels like a bit of procrastination is in order . Maybe I need to get Martin King's software and start playing around a bit more with options.
GM, I will say that the 414-8B from old data works out well in the suggested Petit Onken box.
On output impedance, what sort of amps can you have in mind as having a lot of series resistance ? Worst case ( aside from current source SS amps ) would have typically been SE tube amps which would be between 1 and 2 ohms output Z . Are you thinking of other contributions to series resistance that were used in Onken crossovers somewhere ?
Jonjin , keep us posted on how it goes when you have a better idea . Were the 414-Z's already well run-in ?
MJ
Ok, thanks for the advice chaps. Feels like a bit of procrastination is in order . Maybe I need to get Martin King's software and start playing around a bit more with options.
GM, I will say that the 414-8B from old data works out well in the suggested Petit Onken box.
On output impedance, what sort of amps can you have in mind as having a lot of series resistance ? Worst case ( aside from current source SS amps ) would have typically been SE tube amps which would be between 1 and 2 ohms output Z . Are you thinking of other contributions to series resistance that were used in Onken crossovers somewhere ?
Jonjin , keep us posted on how it goes when you have a better idea . Were the 414-Z's already well run-in ?
MJ
Yes, it looks better than -8C due to its higher Qts, but in the scheme of things all it really means is that it just needs less BSC to tonally balance it.
FWIW, the few SETs I've measured or calc'd its impedance when I had enough info were somewhat higher with a ~2.5 ohms average, but how it interacts with the speaker system's total impedance can make it seem as much as a matching impedance depending on cab tuning.
Regardless, I'm no fan of SETs for the LF, so if one looks at the type of amps Altec and others offered, ergo 'voiced' with, we see medium to low impedance amps with adjustable DF (tone controls) which might have up to 20 ohms of added output impedance. A contemporary variant would be the NP's First Watt series. Unfortunately, when this much simple resistance is used there's usually too big an efficiency loss, so a BSC (LCR tank ckt.) is used.
GM
FWIW, the few SETs I've measured or calc'd its impedance when I had enough info were somewhat higher with a ~2.5 ohms average, but how it interacts with the speaker system's total impedance can make it seem as much as a matching impedance depending on cab tuning.
Regardless, I'm no fan of SETs for the LF, so if one looks at the type of amps Altec and others offered, ergo 'voiced' with, we see medium to low impedance amps with adjustable DF (tone controls) which might have up to 20 ohms of added output impedance. A contemporary variant would be the NP's First Watt series. Unfortunately, when this much simple resistance is used there's usually too big an efficiency loss, so a BSC (LCR tank ckt.) is used.
GM
Sorry for the long absence but sometimes things get in the way (like work!). Also, I've managed to crack the frame on the 414Z when I screwed it on too tight... that put me off for a while until I found another pair. So been busying away, and now both speakers are complete. They have been lined with Visaton lambswool, roughly 1cm thick.
Lots of hard work, sweat (and swearing) been put into these...
Admittedly, they sound amazing. I know I was initially a little reserved but now that the wool lining has gone in and both speakers completed, the sound is simply sublime. The Altec 414 in Onken has to be commended. The mid has good tone and the bass is fast and taut. A well balance speaker, and actually more of a low mid/upper bass than a woofer. It does go low enough for me though. Coupled with the Onken compression driver and LeCleach, it gives excellent dynamics, hair-raising clarity and insight to the music. To say that I am impressed (and slightly surprised) is an understatement.
Will update a bit more later... enjoying music at the moment 😀
JJ
Lots of hard work, sweat (and swearing) been put into these...
Admittedly, they sound amazing. I know I was initially a little reserved but now that the wool lining has gone in and both speakers completed, the sound is simply sublime. The Altec 414 in Onken has to be commended. The mid has good tone and the bass is fast and taut. A well balance speaker, and actually more of a low mid/upper bass than a woofer. It does go low enough for me though. Coupled with the Onken compression driver and LeCleach, it gives excellent dynamics, hair-raising clarity and insight to the music. To say that I am impressed (and slightly surprised) is an understatement.
Will update a bit more later... enjoying music at the moment 😀
JJ
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