Altec 604 OB's

gortnipper · « **Reply #60 on:** 17 Jul 2008, 08:52 am »

Quote from: panomaniac on 17 Jul 2008, 04:00 am

What do you have in mind for a crossover?

This is my first foray into making speakers. Well, not really. My first recent foray.

When I was a Sr. at Roosevelt HS in 1980, I made a Speakerlab 6 kit. Speakerlab was right down the street. EV tweet and mid, with a killer 12" woofer that I think was their own. Their weakness was the crossover, which promptly blew. They blew over the years as they had been relagated to my garage system. I junked them when I moved to NZ. Dumb move. I should have kept the drivers. I didnt know any better.

So, for the start it will be the stock crossover in a JE Labs OB, maybe with a Yamamoto twist. aa

Then maybe a MLTL a la Staephan's. Or another OB with some extra woofs. Who knows....

David

gortnipper · « **Reply #61 on:** 17 Jul 2008, 08:54 am »

w/x-over is 950. I have seen Jeff's design, but the GPA Series III comes with a new crossover.

nullspace · « **Reply #62 on:** 17 Jul 2008, 11:45 am »

I hope someone, somewhere posts a picture soon -- now I'm really curious to curious to check out that horn. Coaxially mounted and will work down 950hz? That I've got to see.

Regards,
John

gortnipper · « **Reply #63 on:** 17 Jul 2008, 08:32 pm »

Quote from: nullspace on 17 Jul 2008, 11:45 am

Coaxially mounted and will work down 950hz? That I've got to see.

Sorry, I was answering a previous post about price - the price for them is $950 including crossover.

chrismercurio · « **Reply #64 on:** 10 Aug 2008, 02:50 pm »

Gortnipper,

I will post this at AA HE speakers too...

Did you receive your GPA 604 series III's? Can you post a picture of the driver? I want to see the horn....and if it is blue.

Chris

gortnipper · « **Reply #65 on:** 11 Aug 2008, 12:59 am »

Quote from: chrismercurio on 10 Aug 2008, 02:50 pm

Did you receive your GPA 604 series III's? Can you post a picture of the driver? I want to see the horn....and if it is blue.

Chris

Chris - I think the only thing that is blue is the horn. My biz trip was canceled at the last minute

I should get them next week when my co-workers travel down here instead of me going there this week.

I have seen BW pictures in a draft of the spec sheet (but was sworn to secrecy to not distribute) and they appear to be gray

I cant see why GPA would make them blue, that is just so ugly!

I will post images as soon as I get them, both here and on AA.

David

gortnipper · « **Reply #66 on:** 15 Aug 2008, 01:32 am »

Here are some pics of my new GPA 604-8H-III with the UREI horns. I took these with my camera phone, straight out of the box, so pardon the poor quality. I guess I should have blown off the dust and cardboard debris, but I was at work and it was going right back in the box to take it home.

Back view, still in box.

These are monster - and I thought my old 12" woofs were big!

The horn is not blue.

X-over fresh out of the box. The one zip tie at the top had been cut by the board it is mounted to.

So, now I have to get on the ball and get them into an OB - they arrived 3 days ahead of schedule from FedEx! I am going to hook them up and run them when I get home, but my tube amps are in storage because the house is being renovated right now. The painters are doing the living room as I write this, so I am bumming that all I can really do is let them run in with my sand amp. Most of the run in after this weekend will likely have to happen in the garage shed to keep them away from the painters.

David

stlblue · « **Reply #67 on:** 15 Aug 2008, 01:59 am »

Mmmmmm, those are beautiful.

I wonder if those horns would fit on my 604E's?

I still haven't had time to build my OB's. Enjoy...I look forward to hearing about your results.

markC · « **Reply #68 on:** 15 Aug 2008, 02:36 am »

Looks like one could improve a whole lot on the x-over. Those inductors have to be interfearing with each other to affect their values, (unless that was calculated; but I rather doubt it).
Also, what appear to be polyester caps, and cement resistor could be upgraded.

gortnipper · « **Reply #69 on:** 15 Aug 2008, 02:53 am »

It is a bit different from their Series II x-over, which I think was improved upon by Jeff Markwart.

http://www.greatplainsaudio.com/downloads/N1600.pdf

nullspace · « **Reply #70 on:** 11 Sep 2008, 10:04 pm »

Any updates for us David? Inquiring minds want to know...

Regards,
John

chrismercurio · « **Reply #71 on:** 15 Sep 2008, 01:46 am »

I received mine last week. They are still breaking in, still changing, and are world class. I will most likely have the xover reworked, and they are definitely going in boxes because they are huge. The bass is actually very impressive in light of it being a dipole.

Best,

Chris

gortnipper · « **Reply #72 on:** 2 Oct 2008, 09:29 pm »

Quote from: nullspace on 11 Sep 2008, 10:04 pm

Any updates for us David? Inquiring minds want to know...

Hi John - yes, I have been remiss in posting feedback, so here is a synopsis...

I have put them in a JE Labs style OB made from 22mm (7/8") thick 13 layer Gaboon ply. Gaboon is a fairly dense wood and the ply is heavy, but when I rap it with a knuckle it doenst sound too dead and it doesn’t ring. It has the appearance of what I know in the States as Philippine Mahogany. I routered all of the edges, to avoid them being sharp and finished them with a couple of wet sanded coats of Danish oil and paste wax.

About a week or so ago pulled my Cary gear out of storage after 6 months. Right before I put it away, i had a very good local tech fix a small ground hum in one channel of my SLP-98P. Then, after 3/4 of a CD ( I was playing Night in Tunisia real loud and it was sounding pretty good), it blew a choke in the power supply. Oil all over the inside. As my tech said, "guitar amps always sound great right before they blow". So, I am using my Creek 5350 SE's passive pre section.

Had some guys over the next day that saw my posts a while back and had congregated in town and wanted to give the GPAs a listen. We got together at one of the guys houses the night before who had a sweet set of Tannoy Monitor Gold 15" in a VERY nice and complicated Tannoy designed but never productized cabinet about the size of the Westministers. Man they sounded nice. They went to the local Avant Garde reps house before coming to my house, as well as to the guy that reps Horning and EAR. Had not nice things to say about the Horinings...."painful".

Another guy is the Shindo rep (also Emerald Physics, Devore and Coincident) here in Auckland and he brought over a Shindo Aurieges-L preamp so we could give the GPAs a good run, which was very nice. I lke the way the Shindo gear sounds. We had to run my Garrard through the Creek's cheap ass phono section to the Shindo, which sounded pretty bad - but the CDs were sounding really nice. The GPAs are starting to open up, but they still sound a bit stiff. It doesnt help that I didn't have my curtains up yet in my listening room. Only 200 hours left to go to get them really warmed up I guess

Going back to the Creek's pre section after that is a drag

The Creek is fine for running my small kitchen speakers and for general listening while doing something else, but the pre section is cheap and thin souding. Not nearly the depth or solidity of the Cary, and it really was appearant after the guys left with the Shindo. I saw the same degree of change when I took the Creek's power section out of play and ran my monobolocs. So, I think that colors my perception a bit of the GPAs too.

In general, I am super impressed with them and they sound more exciting to me than my old Mirage speakers ever did. The OBs do have a lot of depth to the presentation. It is kind of like when I was 17 and built my Speakerlab 6 kit (late 70's EV tweet/mid horns, v good 12" wooofer) - I just want to turn them up and listen all day. They have the same sense of dynamics that have been missing in my hi-fi life.

I am not really sure of the sound, however, mostly due to the lack of a solid frame of reference which is causing me not to be sure what the differences are. First off, my listening room is our living room and due to getting other things back on track in the house we have not got curtains back up yet, and the room is really hot sonically due to the three sets of glass french doors and a bunch of windows. But, my mate plays bass in in jazz and rock groups and after he heard them he ran to the truck and got his stand up bass out, and started playing along to Coltrane in a trance. He loved the imaging, as do I - but there is a fairly tight and distinct sweet spot.

I hear a mid-bass bump which I seem to have mitgated with some big cushions behind the baffles in the corner. I hear occasionally agressively forward vocals. Are these the state of the room, the fact that the Creek is there and not my normal pre, speaker placement, break-in? I dont know yet and probably wont know till I isolate the factors. I also hear a distinct roll off and occasional blur at the bottom end. Although I think this is more room factors + OB limitations.

I do know I want to build them into MLTL or similar cabs. At least, I think I know. I want that bottom end, and dont really have room for a sub. And the fiance HATES the "bigger than a washing machine" OBs.

I just got back from 10 days holiday, and am looking forward to getting my Cary back (have to call the tech...) and getting the rest of the curtains up...and a weekend of listening joy with a wad of 20 new/used LPs

David

nullspace · « **Reply #73 on:** 3 Oct 2008, 04:47 pm »

Hi David --

Thanks for the comments; I appreciate you taking the time to give us an update. I do hope you'll continue to do so as the drivers break-in.

Quote from: gortnipper on 2 Oct 2008, 09:29 pm

I hear occasionally aggressively forward vocals. Are these the state of the room, the fact that the Creek is there and not my normal pre, speaker placement, break-in? I dont know yet and probably wont know till I isolate the factors.

I'll throw out another possibility -- it might just be the recording. I've been dealing with the same issue on my latest speaker project, a 2xTone Tubby 12" on OB + Beyma CP380M w/ 1000hz conical horn. I have a couple of recordings where the singer seems to be giving me a lap dance. For a long, LONG time I assumed it was an issue with the new speakers, because I never heard that forward, aggressive sound from my previous setup, which were Fertin 20EX on JElabs. However, as of late, I'm coming to the conclusion that the 8" direct radiators weren't resolving enough to bring out that aspect of the recording and that the 12"ers plus compression drivers simply reveal the recording for what it is, warts and all.

I struggled with that for a long time because I don't think I have a strong 'reference'. I haven't heard a lot of setups and I haven't had much exposure to what the recordings might sound like on various gear. I'm travelling to RMAF next week, so hopefully that'll be rectified to some degree, as I get to hear some of those troublesome tracks on some pretty swanky equipment.

Regards,
John

gortnipper · « **Reply #74 on:** 4 Oct 2008, 07:02 am »

Talked to my tech today after he finished working on my preamp. It appears that not only was the power supply choke blown, but also the transformer. Both of these had to be refurbished. There was some fresh and nast green corrosion on the female din type plug on the preamp, which was not there when it was worked on before and when it went into storage. Culprit is likely a mouse or a rat pissing on my pre. I hope it is one of the ones that perished in the recent poisoning we did.

gortnipper · « **Reply #75 on:** 5 Oct 2008, 01:53 am »

Here are some pics...

panomaniac · « **Reply #76 on:** 5 Oct 2008, 02:21 am »

Cool drivers! Congrates!

You'll be a happy man.

Just remember - please. That crossover you got from GPA is NOT meant for open baffle. No, not at all.
It's meant for a bass reflex box. An open baffle will have far, far less low end with a low QTs driver like this.

What does that mean? It means that your 15" on a baffle that size will have a rising response, not a nearly flat one as it would in a box. So the crossover must be adjusted to match, or your tonal balance will be all wrong. On a baffle that size you will need a big iron core inductor, not that cute little aircore in the photo. Just a guess, you'll need to be at 24mH or more. And that means the 15s output will be pulled way down at the x-over point. So you will have to attenuate the horn even more - maybe as much as 10dB more.

So many builders don't grasp that the crossover for an OB is not the same as one for a box. Your OB crossover has to fight the big rising response of the woofer. Remember - it ain't a box - and that's why we like them. So it can't use a box crossover and have a proper tonal response.

I've heard (and built) too many OB rigs that have no bass, even if their owners claim they do. If you want to drop the box, you have to make up for it with power and crossover tricks. That's all there is to it.

Just FYI.

chrismercurio · « **Reply #77 on:** 6 Oct 2008, 04:48 pm »

All,

On Saturday evening I took my speakers over to a friends house and three of us all listened to them for about 3 hours. The system included a VPI TNT, VPI JMW tonearm, Koetsu RSP, Shelter 501 Mono (my first mono experience was a great one), Quad pre, Quad 15w monoblocks, EAR 834P modified phono stage + my speakers. It was absolutely the most dynamic, and simultaneously one of the most musical and amazing stereo systems I have ever heard. I was a little reserved but the other two just couldn't stop gushing about the sound. Quotes from the event by my friends who normally hear Quad 989's in the same system, "It's one of the best if not THE BEST sounds ever! Most natural, most musical, and the air!"

I agree with Panomaniac that the xover is not optimized for OB...it is optimized for a 24" wide box. There is also a slight hardness in the upper midrange (that I attribute to the crossover...perhaps it will go away after 300 hours as I think I have about 200 now) that almost went away in my friend's system but is much more pronounced in my cheaper system. I plan on listening to them in a few more of my friends systems before the crossover is redone and am weighing building a nice looking OB and keeping them in it after what I heard on Saturday. I am still in awe of what I experienced. Unfortunately it means to reorienting of my room 90 degrees, and new furniture...$$$. So to anyone interested in these drivers I honestly feel that there are few better deals if you want world class sound for such a small investment.

Best,

Chris

PaulFolbrecht · « **Reply #78 on:** 30 May 2011, 04:43 am »

Can I resurrect this old thread?

I just picked up a second-hand pair of the GPA 604 IIs. With the GPA xovers. I plan to try them, probably, in JE Labs baffles first and then probably eventually the Serious Stereo/6Moons (Staephen) 9 cu ft cabs.

(Had Supravox field coil drivers on OBs a few times and, boy, it's amazing how good that can get. Especially the simplest case of the 8" only on the JEL baffles.)

myaudioking · « **Reply #79 on:** 19 Jun 2011, 12:34 am »

love the natural finishing of the wood panel