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GPA 604-8H-III Build - Sneak Peak.

165.86.81.20

Posted on June 14, 2012 at 00:18:55
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002



Hi All,

I was going to wait until they were finished before posting this build, but I could not help myself. Attached is a progress pic of my first foray into high efficiency speakers.

After many clear coats, Ben (at Sound with Style over here is Aus) is doing a really nice job of bringing out the beauty of the Red Heart Eucalypt. There is (at least) one more coat to be applied, then cutting and buffing. In his words, the finish will be “like glass”. The rest of the speaker will be finished in 'piano' black.

Ben is doing a great job; I really like supporting local craftsmen...

Thanks for taking the time look. Cheers.

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

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RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 03:45:08
Verrry nice! The white stuff is pumice or rottenstone? Real hand-rubbed as of old, impressive!

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 04:33:44
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Thanks for the kind words Bill.

Not sure what the white stuff is though. I can say the Ben seems like a perfectionist of the helpful sort - he won't compromise quality. He tore-off the first veneer he tried, at his cost, because it did not finish the way he wanted it to.

It has taken several years (perhaps > decade?) to put myself in the postion to have these done. I am happy that I did. Now I need to get moving on my first amp build (well, my 1.5th, in a way)...

Cheers.

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 06:39:49
Frank Mena
Audiophile

Posts: 279
Location: S Western Ontario
Joined: May 28, 2006
Very , very nice indeed. Thanks for posting.

Cheers
FM

 

My Advice play them loud !!, posted on June 14, 2012 at 06:41:32
merdy
Audiophile

Posts: 1620
Location: New paltz,ny
Joined: July 25, 2001
lifes too short not to enjoy altecs
Silence is golden duct tape is silver

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 11:05:51
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
Hi RC,

In the photo the driver holes look like they are positioned asymmetrically on the horizontal axis?
If so, is this for sonic reasons or other?

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 13:34:00
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Yes, they are asymetrical - calculated to the Golden Ratio or some such. IIRC, there were two reasons for this, but the only one I can remember right now is that it provides some positioning flexibility in smaller rooms.

I'll dig up some old emails and post the other reason.

Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Nice catch!, posted on June 14, 2012 at 13:40:03
I didn't notice but it's really pretty obvious and, because I once built a pair of subs of Red Gum, I should have seen it.






Intended to help with imaging, maybe?

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 14:05:13
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
Being a 604 8H-III lover I would appreciate the info you mention especially if it does allow for greater flexibility or performance.
Thanks

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 18:18:36
Sidewinder
Audiophile

Posts: 254
Joined: April 13, 2001
Looks interesting. Could you post some drawings and dimensions of your cabinets?
Regards,
David

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 14, 2012 at 19:55:33
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi David,

I would if I could, but this is a bespoke design by Scott Lindgren & Co, who own the IP and drawings. Scott might release the drawings for a reasonable cost after I do some initial tuning and testing and provide him some feedback. You can contact Scott via his Woden Design site - he refers to the design as the Bison. He seems to be a straight shooter and a pleasure to work with.

The design is a ~290L MLTL, modelled using MJK MathCAD sheets (and Scott's experience!), specifically for use in a small to medium sized room, wall-loaded, and driven with an impedance in the general vicinity of 2.5 Ohms. As do most MLTLs, they have a small amount of tuning flexibility to allow room-specific optimisation. As I understand it though, the dimensions, bracing, materials and port-sizing are rather critical.

Cheers.

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

I'll try my best., posted on June 14, 2012 at 20:53:54
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
I will be breaking them in with a 50W SS amp initially - should be interesting for the neighbours!

Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 15, 2012 at 21:03:15
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi 'pond,

From the plans: "Offset drivers/mirror imaged pair will have diffraction effects spread-out and give more versatility in room positioning".

Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 20, 2012 at 13:57:08
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
RC-
Thanks for following up on finding that asymmetry info. Looking forward to hearing your impressions of the sound when you get your rig running.

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 21, 2012 at 20:56:22
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
Very sweet. I am just in the process of finishing mine, and tuning the xo's to the cab. Used dims passed to me from Jay Fisher based on GMs design. One inch Baltic Birch with American Walnut veneer, double thick tops/bottoms, no internal bracing (yet) or stuffing. The builder overlooked the line where I had asked for off-centre drivers.

I had had them stuffed, and then progressively removed the stuffing and found they sound best with none.

They sound much better now with ply under the cabs. The thick carpet and underlay really sucked the bass out.

Much better control and imaging than the having them in the JE Labs OB. Even the wife appreciates the sound. Just not the size.













 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 22, 2012 at 11:05:47
baja
Audiophile

Posts: 73
Location: west germany
Joined: January 2, 2007
series-II - however in 'action' - best,

 

RE: GPA 604-8H-III Build - Sneak Peak., posted on June 24, 2012 at 01:29:19
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi Gort',

Very nice looking cabs that I bet sound real nice; I really like the proportions of those beasties. Interesting and helpful information about the carpet and the comparo to the JE Labs OB design. Double-thickness top and bottom makes sense in MLTLs - IIRC, lots of pressure at the ends of the pipes... mine are about 40mm top and bottom and braced.

Please, would you mind litting us know how they settle in?

Cheers,
Raymond.


"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

Better and better..., posted on June 25, 2012 at 13:40:16
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
Each minor adjustment makes a significant improvement.

Over the weekend I removed the cheap variable resistor I had wired into the xo's woofer output to test-shelve it, and wired in a 3ohm fixed, moving the variable to the tweeter - and shelved that to about 1.5 ohm. Wow, the bass has snapped right in. So much richer and still very controlled.

But, that variable must be a real POS (Jaycar special) as the horn is quite a bit more veiled - a more balanced output, but not as transparent. It will be interesting to see whether or not that returns to previous when I replace it with a good fixed one.

 

RE: Better and better..., posted on June 26, 2012 at 09:34:36
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
Yo Gortnipper,
What crossover are you working with?

 

Love Em!!, posted on June 26, 2012 at 13:09:34
amandarae
Audiophile

Posts: 2591
Location: So.Cal
Joined: November 30, 2004
Very nice indeed! I too have been dreaming of finding the time to built cabs for my 604-8G's. I swapped them once in a while on my bass bins (612C's with 416 LF and 288 Le Cleach horn HF)and although it sounds great, I want to have a dedicated cabs for it. I tried the 620's but my room does not like it as well as my ears ;)

The pics you posted is inspiring to say the least. Thanks for taking the time to show us your project!

Abe

 

Rick Craig's, posted on June 26, 2012 at 16:16:13
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
From Selah Audio. See the thread here from a while back. Way better xo than the stock one, which I also have but is way more "shouty" and sits gathering dust.

 

RE: Rick Craig's, posted on June 27, 2012 at 10:42:19
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
Thanks,
I knew that you had used Rick's crossover in the past but your mention of a variable resistor threw me off. I see now that you mentioned that you added the variable resistor to the circuit.
I am still using Rick's xover too and remain super happy with it.

 

RE: Rick Craig's, posted on June 27, 2012 at 13:39:14
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
I just put the variable resistor in to try to get the most out of the cabs and was always going to replace them.

With Ricks xo in the big MLTL, the bass was a bit dry and thin, so I dialled in a 3R. Soldered that in and moved it to the HF section and am dialling that in now.

 

RE: Rick Craig's, posted on June 27, 2012 at 16:36:31
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
3 ohms series resistance applied between xover and woofer?
Also what maker caps and inductors did you install in your xover?

Thanks
Jay

 

RE: Rick Craig's, posted on June 27, 2012 at 19:13:28
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
Yes. 3R.

Rick just made me his "default" xo, with basic parts. Cost effective, and he strongly encouraged me to not to go after premium parts, as he thought the expense not worth the gain. And money was tight...

IIRC - Solens, Clarity MRs, different inductors including Solens and Madisound. I would have to look more closely when I got home.

What did you end up building with Rick?

 

MLTL is usually superior to generic BR, posted on June 27, 2012 at 20:35:03
scooter


 
I have been surprised by the improved bass and midbass clarity from a well designed MLTL cabinet over a generic dimension bass reflex ported cabinet. A 30% larger volume TL "could" have even superior sound, but that would be BIG-BIG for the Altec 604.

With a large volume (10 ft3) cabinet a bottom-floor port is very wasteful of potential cabinet volume. A large diameter lower front panel MLTL port is often a better alternative in terms of size and critical tweeter height requirements (~39").

B&W speakers has a white paper on bottom woofer ports which describes the need to use very large diameter radius ports on both sides, use an angled bottom board under the port to push the port air to the front-left-right, but block the rear exit. The bottom board also removes carpet effects. A few bottom port 604 BR cabinets owners use both height adjustable legs and bottom floor-boards for consistent bass and room tuning flexibility.

Most modern homes have open floor plans around the living (aks home theater). Older home floorplans had more favorable corner speaker placement.

The GPA 604 deserves freeware MLTL in-room and corner placement designs.

 

RE: MLTL is usually superior to generic BR, posted on June 27, 2012 at 21:41:02
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
"With a large volume (10 ft3) cabinet a bottom-floor port is very wasteful of potential cabinet volume."

Please explain what you mean?

"A large diameter lower front panel MLTL port is often a better alternative in terms of size and critical tweeter height requirements (~39")."

Yeah, I have also read that this should work well. In my cabs, the drivers are exactly ear height.

But, here is a quote from GM, in a previous post that I was tying to recall:

"In a tower (aka MLTL) speaker, the location of the driver relative to the top (closed end) of the cab affects its 1/4 WL loading, i.e. the closer to the top the driver is, the greater the pipe loading, so if the driver is at the top and vent at the bottom, then max loading on the vent is a function of the distance between the two. This also means that the most stuffing is required to damp the unwanted pipe harmonics. Since I prefer acoustic solutions to acoustic problems, I position the driver down the pipe somewhat to minimize stuffing density (increasing overall pipe length to get the HF up to ~seated ear height) while others prefer to position it at the top and adjust vent height, though this way creates secondary reflections that reduces pipe loading and may require even more stuffing density than if near/at the bottom and a longer vent for a given tuning, basically defeating the main purpose of using a MLTL if the vent is placed near the driver as Altec did.

This layout can be used to provide a bit of acoustic gain to offset baffle step loss though since as the vent moves closer to the driver it raises Fb, tilting up the speaker's low end response, ergo the Stonehenge V will require little/no BSC with the trade-off of potentially sounding 'boomy' if near/at a wall boundary while a MLTL will be the reverse with a rolled off bass if no BSC is used and tonally balanced without BSC if near/at a wall."

 

You are not building a MLTL, posted on June 27, 2012 at 22:36:05
scooter


 
""With a large volume (10 ft3) cabinet a bottom-floor port is very wasteful of potential cabinet volume."

Please explain what you mean?"


Hi gortnipper,

Several papers discuss how a cabinet with a bottom floor port must be raised 1x to 2x the diameter of the port for correct port bass wave summation into the room. So, bottom floor firing deep bass ports require cabinets with long legs. This height could be used for adding volume to the enclosure in order to optimize T/S requirements, or to select a cabinet width with superior edge diffraction or superior baffle step frequency, while maintaining a ~39" tweeter height. Antique furniture vs. sculptured modern furniture.

You are not building a MLTL for your GPA 604, so many of the equations which determine speaker height do not apply to your cabinet. It is often difficult in large volume Altec 604 MLTL cabinets to keep the tweeter height ~39" if a bottom-floor port is used because of the 4" - 8" leg height requirements.

A bottom front panel port offers larger cabinet volume with fewer compromises on tweeter height complications with a coaxial 604, and fewer cabinet complications for baffle-step or volume-wasting large edge roundover for diffraction reduction.

I know that a bottom-floor port can provide superior sound compared to a lower front panel port, but a bottom-floor port consumes potential cabinet volume that could be better used in a 10ft3 deep bass coaxial GPA 604 MLTL. Again, you are not building an MLTL, but others might select this option.

The GPA 604 deserves a freeware in-room MLTL and in-corner design.

 

RE: Rick Craig's, posted on June 28, 2012 at 03:18:30
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
FYI, I asked him for an almost cost-no-object design that would reduce / eliminate any residual impression of glare... and he still suggested reasonably priced parts, even though he could have made some $ using more expensive parts. Yes, they a a little more expensive, but not crazy exotic.

I trust his judgemnet and resistance to bump up prices... kudos to Rick. Folks with crossovers using the basic parts should not feel they have an inferior product - Rick uses what he thinks is most suitable for the job.

Cheers,
Ray
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Love Em!!, posted on June 28, 2012 at 03:38:20
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi mate,

It seems I have been absorbing your posts for a good long while - nice to see a respnse from you! Thanks for the props. The 604s are a compromise (are not they all), but one that suits me at the moment. Yes, I think they deserve a dedicated cabinet. We will see when I take delivery and run them with a suitable amp (eventually).

Those Le Cleach horns seem impressive... and probably nice for a smaller room due to their wide dispersion. I like to try them as my next build... if it takes me as long as these, it should be some time in the next 20 years ;^)

Amps will be my focus for a while though...

Cheers,
Raymond


"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: You are not building a MLTL, posted on June 28, 2012 at 04:33:47
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hey Scooter,

Thanks for the contribution.

What you say regarding big-big is should be considered, but it depends on what trade-offs you are willing accept when considered in context and detail. Big-big would not offer much if any benefit in my (or anything but a very large) room. As for the 30% in volume 'lost' to the bottom-firing port, in reality it is much less than this and other design factors also need to be considered.

I think your point regarding the volume 'lost' by using a bottom-firing port needs to be considered, but there are some benefits to botton-firing port in an MLTL such as mine. An experienced modeller that I trust ran simulations using my constraints and preferences. The design I decided on was most appropriate for my circumstances and little different to larger versions, which may have provided more tuning flexibility in a significantly larger room; in my room, the differences were marginal if relevant at all.

BTW, I can't link to your system - I am interested in what are you currently implementing / running and how you might help the rest of us. I'd like to be able to learn from your practical experiences next time 'round.

Cheers,
Raymond
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: You are not building a MLTL, posted on June 28, 2012 at 13:36:04
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002

I'd take GM's (and Scott Lindgren's) designs over most; GM had concerns about the bass response of the classic Altec cabinets and set about designing something provided improved bass depth and smoothness, when located against the wall.

It can be easy to become narrowly focussed on a few design elements and unwittingly allow these to dominate, often to the detriment of the end product. That said, your points should definitely be considered; I would bet GM and Scott have (actually it was given as an inferior option for my build)... their technical ability, experience, results, and thoroughness are enough for me.

Cheers,
Raymond

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: You are not building a MLTL, posted on June 28, 2012 at 15:02:36
GM
Audiophile

Posts: 590
Location: Georgia
Joined: April 26, 2000
There's definitely two discrete categories once the BR morphs into a MLTL, which is when the cab's acoustic path-length loading is great enough to either cause an increase in vent area [Av] and/or shortens the vent [Lp] for a given tuning [Fb].

I've never bothered to do any actual comparisons, but AFAIK there's no set minimum length before it happens judging by how the driver location moves based on both the path-length and cab averaged cross sectional area [CSA] the way I calculate it, though MJK in his Classic TL doc uses some percentage fixed locations based on taper.

They sim a bit differently, though not having done any real world comparisons, I’ve no clue if there's an audible difference.

GM

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 

RE: You are not building a MLTL, posted on June 28, 2012 at 15:41:02
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
"Several papers discuss how a cabinet with a bottom floor port must be raised 1x to 2x the diameter of the port for correct port bass wave summation into the room."

OK - so my legs are 1.375x port diameter.

"You are not building a MLTL for your GPA 604"

You have to forgive me, as I am a novice, but why do you say that? 10ft3 design, dims per GM/Jay with pipe length=42.5" x-section area = 422.04"^2, 6" port 2" long, driver center at 19.625" down from top of pipe.

I am sorry, but I am not quite sure what you mean by, "The GPA 604 deserves a freeware in-room MLTL and in-corner design"?


 

RE: You are not building a MLTL, posted on June 28, 2012 at 16:15:08
GM
Audiophile

Posts: 590
Location: Georgia
Joined: April 26, 2000
I currently don't have access to my correspondence with Jay, just recall that the MLTL designs I originally did were downsized quite a bit plus IIRC he had me relocate the driver to suit him, so the driver isn't where I would normally recommend either.

Regardless, with the specs you've posted, it's so close to a golden ratio cab that it's just a nice, smooth simming bottom vented BR.

I too would like to know what he means by "The GPA 604 deserves a freeware in-room MLTL and in-corner design" as I don't agree with the 'free' part per se, though I've posted some ~60-160" long ones on various forums for others over the last ~12 yrs.[no links currently available].

GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 

RE: You are not building a MLTL, posted on June 28, 2012 at 17:43:11
"Loud is Beautiful if it's Clean!"

Hey GM, you DO realize that that's a trademarked slogan of Cerwin-Vega, don't you?

:)

 

RE: You are not building a MLTL, posted on June 28, 2012 at 18:18:09
GM
Audiophile

Posts: 590
Location: Georgia
Joined: April 26, 2000
I know it was a '70s era CV marketing slogan as I have a pin on button with it that they were handing out to everyone they could at a large HIFI show and the few folks that's commented on it I've had to tell them I got it from the CV button, but you're the first to say it's trademarked. For sure the button doesn't.

GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 

Thanks for the correction and clarification., posted on June 28, 2012 at 19:45:09
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
I will edit my previous post so folks don't search and take it as fact.

As ever, I very much appreciate your contributions. They are informative lessons, even if I limit my learning to a general knowledge of concepts, not the specific methods etc. Without them, I would likely not have known where to start my search, what needed to be considered in the early stages... and perhaps even who to engage to do the design work for me. I owe you a debt of gratitude.

What forums do you mostly contribute to these days?

Cheers,
Raymond
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: You are not building a MLTL, posted on June 28, 2012 at 20:05:31
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
Where would you recommend the driver height in these type of 10ft3 designs?

 

RE: You are not building a MLTL, posted on June 28, 2012 at 20:21:59
GM
Audiophile

Posts: 590
Location: Georgia
Joined: April 26, 2000
Actually, the 19.625" distance you posted is correct [14.833" using MJK's math], so I must be getting this one confused with one of the others I did, possibly for Jay. Problem is, I've done so many 'variations on a theme' that with a memory that's been fading fast for awhile now and without my email/posting 'library' to refresh it, I probably shouldn't 'shoot from the hip' anymore.

GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 

Sweet, thanks., posted on June 28, 2012 at 20:31:00
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
Check your inbox, sent you mail.

 

RE: Thanks for the correction and clarification., posted on June 28, 2012 at 20:36:47
GM
Audiophile

Posts: 590
Location: Georgia
Joined: April 26, 2000
You're welcome! I don't follow the forums or post much these days, though I spend more time on the Altec and DIYaudio forums than any others.

GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 

RE: Rick Craig's, posted on June 29, 2012 at 20:09:45
smallpond


 
Solen caps for the resonance trap and Jantzen Superior Z Caps for the rest with Goertz air core inductors.

 

Mmm..., posted on June 29, 2012 at 21:23:23
gortnipper
Audiophile

Posts: 866
Location: Seattle expat in Auckland
Joined: November 28, 2003
trade ya ;-)

 

RE: Rick Craig's, posted on June 30, 2012 at 00:05:46
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi Jay,

Was that crossover built by Rick? I did not think he used Jantzen and Goertz?

I have plans for a rewire of the my crossovers, possibly using some copper film PIO and would also consider a change to the coils, but Rick said (I think) that a different DCR could impact the performance... Any thoughts?

Also, did the MLTLs sound dry with other crossovers? Interesting that Rick's crossovers might have contributed...

Cheers,
Raymond

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Rick Craig's, posted on June 30, 2012 at 11:34:17
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
Hi RC,
Yes Rick built my crossover and I requested the Jantzen and Goertz parts because I have had very good luck with them in the past.
I have used the Great Plains and Jeff Markwart crossovers and I prefer Rick's. It has the most balanced and non-fatiguing sound of the 3.

 

RE: Rick Craig's, posted on June 30, 2012 at 11:40:39
smallpond
Reviewer

Posts: 129
Location: So. Cal.
Joined: September 23, 2001
I wanted to understand your 3rd question re: parts and performance.
Are you asking if different brand caps and coils but of the same values specified for the xover would change the DCR and performance of the xover?

 

RE: Rick Craig's, posted on June 30, 2012 at 17:59:59
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Sorry Jay, I often don't communicate clearly.

I also have one of Ricks more expensive crossovers (different components to what you have used though) but was thinking that at some stage I might like to try different coils. But, I vaguely recall Rick saying that the DCR of the coils was important (though others think not, within reason). I guess I am seeking your experience and opinion to help me better understand the DCR issue...

However, as this is related specifically to Rick's design and and IP, it is probably not appropriate to discuss it here. Would you mind if I PMed you to discuss further?

Cheers,
Raymond.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Rick Craig's, posted on June 30, 2012 at 18:03:23
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Thanks Jay. I am very pleased to hear that Rick's crossovers have worked out well... non-fatiguing is essential for me!

Hopefully my speakers are too far away now...

CHeers,
Raymond
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RE: Rick Craig's, posted on June 30, 2012 at 18:56:07
smallpond


 
Ray,

Feel free to message me off thread re: 604s and crossovers any time.

Jay

 

A more typical tall, high driver MLTL, posted on June 30, 2012 at 21:05:19
scooter


 
"Where would you recommend the driver height in these type of 10ft3 designs? "
If the driver is offset at approximately 1/3 the length of the straight transmission line, the 3/4 wavelength standing wave can be totally suppressed, and in addition the impact from every other quarter wavelength mode (3/4, 7/4, 11/4, …) will also be essentially removed from the system SPL response. Using this 1::2 ratio, a 39” ear level driver position would require a ~58.5" line height with the driver center 19.5" down from the line top. Total internal line volume of 11 cu_Ft with a 419 sq_in line section area, short 6" port 7" above the line bottom. …. a normal tall MLTL.

' I am sorry, but I am not quite sure what you mean by, "The GPA 604 deserves a freeware in-room MLTL and in-corner design"? '
A custom speaker design uses the owner's actual room dimensions including proposed speaker positions and listener position, as well as the owners personal preferences like "I want BASS". The designer uses simulations which include: room modes; corner gain; rear wall gain; absorption from carpets, drapes, furniture; room absorber/diffuser panels; cabinet edge diffraction optimizations; custom crossover circuits; baffle step compensation circuits; custom T-Line stuffing options; etc... Design experts with CAD software required.

I used the term "freeware design" to mean complete design drawings not requiring additional expert CAD software help for a common up against the wall Big-speaker placement. The GPA 604 III has unique T/S parameters, SPL/frequency response, and polar horn response that would model a slightly different cabinet from the classic Altecs.

 

RE: A more typical tall, high driver MLTL, posted on July 1, 2012 at 01:50:33
RC Daniel
Audiophile

Posts: 1922
Location: Brisbane
Joined: November 3, 2002
Hi Scooter,

Thanks for taking the time to share. I agree, a (decent) custom design does take into account the factors you mention, plus the amplifier output impedance. I commissioned such a design and it was by far the least expensive part of the project... maybe 5% of the total cost, probably less. I would recommend people do the same.

That said, some of the mentioned factors do not change with a change of room and a design can have enough flexibility and scope for tuning built in so that it can work well in a variety of rooms, providing the positioning is similar and the room size does not change to a large degree. If this were not the case, the design you suggest be made available would be of little use.

Cheers.

"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki

 

RC ... what T/S parameters for GPA 604 III are you using?, posted on July 16, 2012 at 13:02:18
scooter


 
Hi RC Daniels,

Can you share what T/S parameters you are using for the GPA 604 III?

The Mms that simple T/S equations calculate from the GPA datasheet seems low. I hope to get my Akabak MLTL model to also provide gain for most of the floor bounce of a 39" - 42" high GPA 604 III MLTL location.


Thanks,


SIMPLE T/S CALCULATOR DATA using GPA datasheet
Re = 7.14
Sd^2 = 825.8 cm^2
Mms = 67.8 grams
Xmax = 4mm
Vd = 19.4 in^3 = 0.32 l = Sd*Xmax
Fs = 33.7 Hz
Vas = 329.9 l
Qts = 0.26
Qms = 11.8
Qes = 0.266
Vd = 0.24 ft^3
Sd = 825.8 cm^2
Piston Diameter 12.77 in
Bl= 19.6
Cns = 0.0002832 m/N
Sensitivity = 98.63 db/watt
n0 = 0.0440
Rms = 1.2160

 

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