Raising the While Flag on 604 Project

Hi gang,

Well, as many of you know, I’ve been working on a Great Plains 604 based project for over 2 years now. My progress slowed considerably 6 months ago, and over the last 6-8 weeks, it has stalled completely.

I’ve come to realize that life is just too busy now to finalize this project, so I’m getting ready to raise the white flag. I guess something like this is better done during retirement! I already sold my tube amplifier, so I now have two magnificent loudspeakers sitting quietly in my living room.

I’m embarrassed to admit how much I have invested in them. The cabinets were made by a craftsman that specializes in custom cabinetry for multi-million dollar homes. Most of his handiwork is in excess of $100K. I used a proven cabinet design, with input from a variety of kind and generous individuals. I had actually dreamed of turning this project into a very small, boutique commercial venture, custom building speakers for clients. The cabinet construction was heavily documented with photo’s, and I can obtain the drawings, which were done by hand, yet look like they were generated by a CAD program. The drawings themselves are magnificent, and were done so the system could be mass-produced if desired. I even used commercial parts, such as gold binding posts, polypropylene inserts for the ports, etc.

I have two sets of XO’s, the original Great Plains set, and a custom set that was built by a wonderful gentleman out of Chicago, who lives and breathes these types of drivers. They are built on Plexiglass boards, hand wired and soldered point-to-point. They're magnificent! He is certainly on the brink of a breakthrough with this XO.

I guess I’m looking for some advice on selling the speakers. I realize that is a very special speaker system, so an ad in my local newspaper won’t cut it. I don’t even know how to value them. Of course to me, they’re worth a million!

Any input or advice would be most appreciated!

Thanks!

Photos, lots of photos, please

all i can say is...see it through. sounds as if your almost there! if you go to any of the boutique shops, your pair will blows theirs away! you can do this. sell them?! no way, hook 'em up and play your favorite music through them

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Originally Posted by valhallax

all i can say is...see it through. sounds as if your almost there!

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Well, the reason I pursued this project to begin with, is because I went down the "high end" path many years ago, and could never find a system that recreated the magic that my Model 19's provided. I went through numerous systems, from Thiel, to Martin Logan, to Magnepan, to Von Schweikert, to......After visiting CES two years ago, I realized that none of the consumer products appealed to me, with the exception of systems like the Edgarhorn, which are hideously expensive.

Anway, I've been fighting with extreme midrange energy and weak bass output through the entire project, and I just don't have time to take measurements, and do what's necessary to finish this out. Right now it's a matter of tweaking the XO's, but I don't know how to do it. The gentleman that has been making the XO's for me has already built 3 pair, which is well beyond any expectations I had.

I've tried Stehpaen's 4th order, the Great Plains stock version, Jeff Markwart's 3rd order, and 3 custom XO's to no avail. While it seems as if I'm close, I'm in the same position I was the day I put the drivers in the cabinets.

I'm a little disillusioned at this point, and the excitement is slowly waning...

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Originally Posted by Panomaniac

Photos, lots of photos, please

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Here's a sampling...Hope it works...

http://www.hostboard.com/forums/hbmc...2007/10/19.jpg

http://www.hostboard.com/forums/hbmc...2010/02/14.jpg

http://www.hostboard.com/forums/hbmc...2010/02/15.jpg

http://www.hostboard.com/forums/hbmc...2010/02/16.jpg

Thanks, great photos. Very pretty.

I have to say, the box looks too small to me. Maybe that's why you're struggling with not enough bass - too much mid?

Can you post the inside dimensions? There are a number of skilled box guys here, perhaps they can help. And the port size and length is important.

edit:
Hmmm.. looking again a doing a rough estimate, the boxes are not small. Maybe 42Hx24Wx21D.

And a few more...The press-fit grills are a work of art...

http://www.hostboard.com/forums/hbmc...2007/10/13.jpg

http://www.hostboard.com/forums/hbmc.../2008/09/6.jpg

http://www.hostboard.com/forums/hbmc...2010/02/17.jpg

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Originally Posted by Seadweller

Anway, I've been fighting with extreme midrange energy and weak bass output through the entire project..........

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Hmm, something doesn't 'ring true' as the 'spread' through the XO BW should solve the 'hot' mids, but for sure the larger HF horn that allows a nominally 1 kHz XO I'm a 'broken record' about will solve it. Ditto woofer diaphragm treatment, but this typically requires significant experimentation with the real possibility of ruining some before getting it right.

As for weak bass, these drivers either must have a huge cab tuned to blend as well as practical to the room and/or a very high output impedance source combined with good room boundary loading, so with such an acoustically small cab you apparently don't have the latter and I assume the Fs tuning required.

GM

What I ended up with on the Mantaray orn 604s I have was nominally ~1600Hz, 3rd order crossover with a spread. I'll see if I can find my notes.

I found that the mantaray horn just would not play down lower and stay clean.

This is one story I don't like to read.I guess it's the part where you may Give Up.You seem to be so close.The 604 should be in a box 9cu. ft/620a for best bass performance I have a pair of 612C's that are 6.8 cu. while the bass is good the extra 2.2 cu. ft will produce much better bass response.

If anything felt like a million bucks to me I would keep them !!! And I would be looking for a new Amp :)

I'll be building a set of 620/modds soon as soon as this 3 ft. of snow melts :D I wish you the best and hope you can stick with it especially after putting 2 years into it.;)

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Originally Posted by Panomaniac

Can you post the inside dimensions? There are a number of skilled box guys here, perhaps they can help. And the port size and length is important.

edit:
Hmmm.. looking again a doing a rough estimate, the boxes are not small. Maybe 42Hx24Wx21D.

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The internal cabinet dimensions are 23.125"W x 18.4775"D x 42.5"H. The CSA is 426.3672. Internal volume is 10.486 cubic feet.

Port size is 6". The one thing I have not experimented with is port length. The port insert I have will allow a 3/4" to 6" port length (I'd have to trim it in increments).

The port fires downward, and is 10" from the floor.

edit: By the way, it's an MLTL design.

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Originally Posted by GM

As for weak bass, these drivers either must have a huge cab tuned to blend as well as practical to the room and/or a very high output impedance source combined with good room boundary loading, so with such an acoustically small cab you apparently don't have the latter and I assume the Fs tuning required.

GM

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Thanks GM...You've actually been very gracious with your time and input throughout this project, and I thank you for that. I actually moved to a tube amplifier to experiment with a high output impedance source to no avail. Funny thing is, I even thought my oldie but goodie Rotel CD player might be contributing to the excessive midrange and/or weak bass, but have yet to try another CD player to see if that might be the case.

The system is extremely shouty in the vocal range; so much so that listener fatigue is nearly immediate, making them unlistenable. I can only describe it as a "megaphone" effect in the frequency range where vocals appear. Any instrument in that frequency range is significantly "enhanced." It overwhelms the rest of the spectrum, and at times, is painful to listen to. It almost sounds like a giant clock radio, I'm sorry to say.

Other's that have listened to the system notice it immediately. It almost seems as if woofer beaming is the issue, and despite the inclusion of a notch filter in this range on my lastest round of XO's, the beaming persists.

Believe me, I hate to give up on this project, but I'm stuck, and my wife has been very nice about FedEx shipments, XO's lying on the floor, and a washer/dryer combination sitting in the living room! 8)

From what I'm seeing, I agree with the others - the boxes are too small.

My guess is you've been treating the symptom and not the cause - the box isn't big enough for the LF part of the 604 to do "it's thing", so the LF suffers and the mid-band, which doesn't care about all that, is doing it's thing, and the lack of balance is what you're hearing.

I can tell you from personal experience that the 604's LF response is IMPRESSIVE in the right sized box when properly tuned - the 50" Bass Drum in the soundtrack from "Star Trek - The Motion Picture", for example, will almost knock you down with only about 15 watts of audio power needed. I've demonstrated this for people and they just can't believe how fantastic the low end from these sound.

But they were in 9-cubic foot boxes...

My advice is -

1. Take a nap. :)
2. Step away for a few days, but not too long.
3. Come back and revisit the project thusly:

A. Build one 9-cubic foot box (I suggest the Stonehenge V - I drew up plans for it several years ago, and they really work well and aren't so ugly, ie, bulky, as the Altec 620 box).

B. Install the 604 in it.

C. Use the GPA crossover.

D. Set all of your electronics to flat.

E. Play some LIVE recordings of music you are familiar with and see what you think. This way, you avoid mistakes in mixing that often occur on studio's, and the resultant problems that studio recordings often have due to crummy speakers they're usually mixing everything down on.

F. Let us know what happens.

If you're close enough to Oklahoma City, I could arrange to loan you a Stonehenge V enclosure to try...

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Originally Posted by Todd W. White

From what I'm seeing, I agree with the others - the boxes are too small.

snip

But they were in 9-cubic foot boxes...

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Thanks Todd. My boxes actually measure over 10-cubic feet. This is what perplexes me. If you deduct for the insulation, they're still over 9-cubic feet.

edit: By the way, while bringing up the bass response might provide a better balance accross the spectrum, the "beaming," megaphone effect of the frequencies in the vocal range still remains, abeit better masked by the greater bass output. Funny thing is, I don't believe it's the drivers. Many folks have used my identical cabinet with excellent results. You can see why I'm puzzled and somewhat disillusioned.

9-10 feet is plenty. (good to know I was close on the dims). I'll try to run sims on the cabinet.

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Originally Posted by Panomaniac

9-10 feet is plenty. (good to know I was close on the dims). I'll try to run sims on the cabinet.

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Thanks Panomaniac! Actually, thanks to everyone!

I'd love to finish this project, but I'm out of airspeed and altitude with it. If there's a reasonably straightfoward fix, I'm all ears!!

First we gotta figure out the problem, then we can fix it!

Below are sims of the box as a bass reflex. GM may be able to simulated it as a MLTL.
3 plots. One is for the GPA 604-8H-II published specs with your box and the port at 3/4"
Another for the 604-8H drivers I have here.
The green for your drivers but with a 3" port length.

The sims don't look that bad. Not enough to give you shouty sound. I suspect crossover issues, maybe even just the horn level.

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Originally Posted by Seadweller

The system is extremely shouty in the vocal range; so much so that listener fatigue is nearly immediate, making them unlistenable. I can only describe it as a "megaphone" effect in the frequency range where vocals appear. Any instrument in that frequency range is significantly "enhanced." It overwhelms the rest of the spectrum, and at times, is painful to listen to. It almost sounds like a giant clock radio, I'm sorry to say.

Other's that have listened to the system notice it immediately. It almost seems as if woofer beaming is the issue, and despite the inclusion of a notch filter in this range on my lastest round of XO's, the beaming persists.

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The room appears to be overly "bright"...bare walls, no drapes, bare floor, etc. Have you tested them in any other rooms?

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Originally Posted by Panomaniac

First we gotta figure out the problem, then we can fix it!

The sims don't look that bad. Not enough to give you shouty sound. I suspect crossover issues, maybe even just the horn level.

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The midrange output was the most excessive with the stock GPA XO's. My latest set of XO's actually has a lift circuit for the bass, a notch filter around I believe the 1,500KHZ range, and L-Pads that allow for adjustment of the horn output. This is the third set of XO's in which we've tried to address the shoutiness.

Is it possible that the woofer could be beaming in this frequency range? Can that be addressed via the XO?

The driver was placed in a very specific location, evidently to ensure MLTL alignment. I also have a 3 ohm resistor in the woofer circuit as part of the alignment. The system has a tremendous amount of impact, but the bass is certainly lacking.

GM mentioned Fs tuning..How is this addressed? I'm still very wet behind the ears when it comes to this stuff.

Uh oh, looks like I'm starting over again!! :)

Seadweller, I would also encourage you to continue your project until you are satisfied. After quickly reading the thread, two thoughts occur...

1) Judging from the pictures your room acoustics may be really awful. I looks like you may have a fairly small room with all hard, reflective surfaces. Boxing the enclosures in tightly between the wall and center cabinet strikes me as a bad idea as the closely timed reflections will smear imaging and exaggerate the upper mids. Try pulling your enclosures well out into the room and putting something soft against the side walls and floor to catch the bounce. Mattresses work well for quick experiments. Hard, reflective rooms can really exaggerate the upper mids in a most unpleasant way, and too much mids sounds like too little bass. Better yet, if you can, try moving your speakers outside and away from any reflective surfaces so you can hear what they really sound like, and prepare to be surprised.

2) Use a well recorded female vocal to set your high frequency driver level. Thick and chesty = too little, and thin and screechy = too much. With practice you can get it within a dB or so by ear. The top couple of octaves will also diminish as you turn the high frequency driver down, but these can be restored with work on the crossover, bypass caps etc. It is most important to get the vocals right, the rest can follow.

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Originally Posted by sba2

The room appears to be overly "bright"...bare walls, no drapes, bare floor, etc. Have you tested them in any other rooms?

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Indeed, the room is somewhat bright...There's quite a bit of furniture in the room, and a carpet that covers a large portion of the floor, but there are no wall coverings. Unfortunately, I don't have another room in the house that's any better (or, where they'll fit :))

My prior speakers, in the same location, worked fine however. In some cases, the bass output was too high. I think the shoutiness is more XO or driver related than room related, because it's evident even at low listening levels, with a listening position closer to the speakers.

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Originally Posted by Steve Schell

The top couple of octaves will also diminish as you turn the high frequency driver down, but these can be restored with work on the crossover, bypass caps etc. It is most important to get the vocals right, the rest can follow.

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Thanks for the great input Steve...Unfortunately, this is where I fall flat on my face. I know nothing about crossover design, so I've been providing anecdotal data to the gentleman that's been working on them...I'm in Florida, and the crossover designer is in Chicago, so I provide comments, ship the XO to Chicago, he makes changes, ships them back, and the process has gone on for some time now.

I have a CD with incredible female vocals, and listening to it through this system will give you goosebumps. I've noticed when dialing down the horn, that the high frequencies suffer, and the "air" and "sparkle" is lost. I believe my latest XO was designed to allow the horn to be adjusted, while a lift circuit restored the highs, which is I believe what you suggested.

If I could make these XO adjustments myself, I'm sure I could tweak the system until it was right, but I wouldn't even know where to begin. Ultimately, this is a stumbling block I haven't figured how to circumvent.

Seadweller,

have looked at your speaker connections? Sounds maybe there "might " be a phase issue.

I had a similar problem with another set of speakers....

sorry if you have all ready went through the trouble.

I have 604-8k's and at very low volume the bass is a little anemic, but when I crank it up , I get bass. Plus it looks like I will have to do some acoustic panels to help tune the room. I have a bass nodes when I walk around. DO you notice an increase/decrease in the BW when you walk around while listening?

-chris

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Originally Posted by oface1

Seadweller,

have looked at your speaker connections? Sounds maybe there "might " be a phase issue.

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Hi Chris,

Yep, I've gone through the connections 100 times at least! :) I do notice that the bass improves in the very back of the room, but I'm sure that's normal. Some CD's have more bass than others, but in general, the bass output is much weaker than my previous pair of speakers.

It seems that the low bass output, and excessive midrange output have combined to create one heck of an issue to overcome..

Hmm...

Well, I can tell you that my 604's (in 620 A cabs, using the older GPA XO), do not have the slam/impact in the bass region that I was used too, but it is there....

And just like you, I got to the back of my room and there is the bass, just rattling the walls (music depending),

But when I go to my listening position, it is not as pronounced.....

when you say the bass is weaker, can you give a factor maybe?I know that he 604 isn't suppose the be the last thing in BW dynamics, & and there is a significant drop below ~40 Hz.....Have you tried using a Active XO or any other Eq to adjust to taste?


-chris

Good day:
You mentioned insulation-too much can hinder bass extension in my experience-typical thing is to line one opposing side of each pair of sides from what I've gleaned on this site over the years.
I didn't read if you were using new GPA drivers or 604-8K's, when I glanced back briefly. New drivers may have very stiff suspension, as I know from a 604C re-cone from GPA versus the springiness of the original cone. This may or may not affect LF response, and if so does it need time and use to improve? I don't know and have not been able to tell from a forum search. I have not used mine long enough to tell.
What about trying original Altec 604-8K crossovers, without the tweaks? I have -8K's in Stonehenge-style aftermarket enclosures, about 8 cu. ft., with orig. Xovers and they sound great- strong bass is there when the program calls for it, but no bass hints or boom ("undertones"?) when there is no bass info.
-Jon Archibald

Hi,
few months ago friend of mine bought GPA604-8hII. He built 10cu ft. boxes and decided to use Jeff Markwart's crossover design. To make a long story short - it was disaster.
Very bright (no bass), extremely colorated midrange - unlistenable. He asked me for a help.
Measurements revealed the situation I just described. So, after a bit of measureing, soldering and listening here is what I came up with. It measures pretty linear and sounds excellent. Anyway - I think it's worth a try if not satisfied with stock (GPA) or any other crossover. :)

Hey, maybe we've got you back on the horse! :2thumbsup:

If you really want to tweak, you should get a Behringer DCX2496 and an extra amp. You may already have the amp. You can always sell the DCX2496 after if you don't want to keep it.

I got a pretty nice sounding rig going with the 604-8K and the DCX crossover. No lack of bass, not shouty. Good imaging. Those drivers should be close enough to your 604-8H to be no problem. My crossover points were 1160Hz on the woofer, 1530Hz on the horn. 3rd order butterworth. Some shelving EQ on the woofer and the horn. 28mm delay on the woofer.

With the DCX2496 you can tweak to your heart's content and we could even help. Once you get what you like, a passive crossover could be built. I feel for your crossover guy. Doing it long distance like that is super hard.

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Originally Posted by oface1

when you say the bass is weaker, can you give a factor maybe?I know that he 604 isn't suppose the be the last thing in BW dynamics, & and there is a significant drop below ~40 Hz.....Have you tried using a Active XO or any other Eq to adjust to taste?

-chris

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Hi Chris,

I find the 604's to be much more dynamic than any of the other speakers I've owned, except of course for my Model 19's that I foolishly sold many years ago. What I like about these drivers is the liveliness of the presentation, which to me, provides greater dynamic swings than many other speakers.

I owned VonSchweikert VR-4's, and while they were an excellent system with incredible bass response, they were very subdued. If I gave the VR-4's a 10 for bass, my current 604 system would probably rank a 4 or 5 overall. I just can't figure out why I'm lacking bass using an enclosure of this size!

I went the "purist" route many years ago, buying stuff without tone controls, etc., but it has crossed my mind to try an active XO or equalizer. I've even considered one of the XO's that you set up the mic's in the room, and it automatically determines the proper settings, but I would suspect they're expensive, and I already have a small fortune invested in these speakers as it is.

I took the "money is no object" approach with the cabinets, because I thought this was the last speaker system I'd ever buy! :)

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Originally Posted by aeyb701

Good day:
You mentioned insulation-too much can hinder bass extension in my experience-typical thing is to line one opposing side of each pair of sides from what I've gleaned on this site over the years.

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Hi Jon,

Yep, that's correct...I have insulation only on the top, one side wall, and real wall of the cabinet...

The 604K's, almost without exception, have the wrong magnet on them - after EV bought Altec, they forced them to consolidate on some standard magnets EV was already using, and they made Altec use the DH-1A HF driver magnet, if memory serves, for the 604 and the 515.

The result in the 604-8K was the midband got too much energy. It wasn't that the bass was suffering - it was still there, just like always - but the midband was getting too much magnetic energy. Jerry Hubbard figured this out and fixed it - the GPA 604's don't have this problem.

I believe you're using GPA-built 604's, so this isn't an issue, but I thought I would mention it anyway.

Here's a really stupid question - have you tried taking them outside, weather permitting, and listening to them using the GPA crossovers, no eq, and a live recording? You might find they sound completely different, maybe actually really good!

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Originally Posted by Panomaniac

Hey, maybe we've got you back on the horse! :2thumbsup:

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Yeah, you guys are no help! It's obvious how dedictated/commited you guys are to this stuff. Not a single response to my question asking for guidance selling them. All you've done is get me excited again.

OK, darn it, I'm back on board....But, with one caveat, I really need to get these things right...

I'm wide open to recommendations...I sold my amp, so all I have now is a pair of gorgeous speakers, and a 20 year old CD player...

Let's do it! :)

I second Todd's advice about getting them outside & setup stock with the GPA XO's. There you remove a huge factor in this.... the room.

-chris

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Originally Posted by Todd W. White

Here's a really stupid question - have you tried taking them outside, weather permitting, and listening to them using the GPA crossovers, no eq, and a live recording?

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Hi Todd,

Yes, GPA 604's is what I'm using...Actually, I haven't thought of taking them outside...The neighbors might think I'm nuts, but hey, who cares?

I've got to find an amplifier now...

You located anywhere near central SC? I would gladly help out if so......


-chris

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Originally Posted by Panomaniac

If you really want to tweak, you should get a Behringer DCX2496 and an extra amp.

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So, does this device require 2 amplifiers?

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Originally Posted by oface1

You located anywhere near central SC? I would gladly help out if so......


-chris

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Thanks for the offer Chris...I'm actually in the Tampa Bay area...

Welcome Back !!! You just put a smile on my face for a week at least :) Do you have other set of drivers,stock Altec Xo's that you can swap out to see if you have the same result say a Altec 604-8G, or Altec Lansing 604-8H or another 604 if not can you borrow one with original Xo's if they sound the same then it would be your room acoustics or enclosure would it not.As others have said the room does look to be bare alot of hard flat surfaces.Moving them out to test outside or in another room is a good idea.Sending Xo's back and forth 1000 miles a half dozen times definately needs to end :( Your boxes definately have plenty of volume did you post the dims of the port size.I can imagine the look on your face when you eventually get to that sweet spot. (:D) Regards ~ John

I don't know anything about the Altec 604. Can it be connected to just the LF side of the speaker? And if so, would that help to determine if the 604 is working properly?
As Altec Best suggested trying some other drivers in those beautiful cabs might give you some clues? When you get it right you'll be more than satisfied you hung in there!

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Originally Posted by Seadweller

So, does this device require 2 amplifiers?

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Yes, with an active crossover you will need 4 channels of amplification for your speakers.
The amp to run the horns does not need much power, a watt or 2 will do, but more is of course OK.

I would suggest that you decide what type of amp you want to go with for the final system. Tube or solid state. It will make a difference to the tuning of the crossover. The amp used to run the horns in active mode will make less difference, at least for tonal balance. Neither of these need to be of superb quality right now, if you just want to tinker. A 5.1 channel home theater receiver with analog inputs would do the job if you want to go solid state.

But first thing to do is what Todd and others suggest. Take them outside. See what happens to the tonal balance. If you can, arrange it so that the crossovers are easy to swap. You'll want to listen to both. Start with the horns all the way down, then bring them in slowly.

And you're right, we aren't helpful at all in getting them sold. :p