I´m new here, will you show me around ? questions regarding G.A Briggs OB´s...

[runblader]

Hello,

This is my first post on the Lansing Heritage forum.

After doing so much research on net that my head started to spin I finally admitted to myself that I needed help from others that know more about these things than I do....

I have just recently bought myself a pair of Altec Lansing Duplex 604 E speakers.

Just for information: I´m on a tight bugdet at the moment.

I want to ask questions about the G.A Briggs OB solution + the matching tube amps in this thread.

THE OPEN BAFFLE CONSTRUCTION:

I want to build a G.A. Briggs OB solution for my Altec speakers.

You can see the drawing plan here :
http://jelabsarch.blogspot.no/2012/0...en-baffle.html

Somewhere on net I read that birch x-finer is a better than MDF for these OB constructions because MDF is a dead material, and the 3D effect in sound is present with birch and not present with MDF constructions.

1. Could someone out there please explain what this explanation of the 3D effect means ?

So I´m planning on building myself a Briggs birch open baffle construction . This is a good alternative to thicker constructions for me because the construction is based on 12 mm and 9 mm x-finer ; that is much cheaper where I live compared to 18 mm birch x-finer ; that is even quite difficult to come by.

This OB construction is also filled with sand. After what I have read on net the meaning by using sandfilled OB´s has something to do with friction and by using different materials I get less unwanted friction in the open baffle.

2. Is this understanding of it correct ?

Last question regarding the OB :

3. Has anyone out there experimented with 12 mm ( 2/4 inches ) vs. 18 mm ( 3/4 inches )plates on this type of OB´s ?

TUBE AMPLIFERS:

So I´m on a tight budget here... sorry for the repetition of things...

Today I own solid state and hybrid amplifers.

My best solution I´ve figured out so far is to buy myself a Bottlehead integrated tube amplifier kit: the Steromour with 2A3 tubes. I live in a open solution flat but the space around the speakers will be roughly 15 squaremeters. The whole room in itself is not bigger than 25 square meter.

Will a 2A3 tube amp work in a room of this size ?
The effect on this tubeamp is 3.5 WPC if I remember correctly.

All help will be really apprecited ....

[Mr. Widget]

Let's back up a minute. What type of music do you listen to? What systems have you heard at an audio show, a store, or a friend's home that you really liked?

Are you looking for "magic" or fact/science based answers... it appears you've been reading a bit in both camps.


Widget

[runblader]

OK. that´s probably a good idea.

I listen to a lot of different genres, but on this system I´m thinking of playing just records (LP´s.)
And in my record collection I mainly have jazz (50´s 60´s) , classical music ( not big orchestras , but rather smaller assembles , even just one solo player : like glenn gould ... ) , blues , classical rock ( neil young , beatles, rolling stones ) singer songwriter ( leonard cohen, nick drake .. )

That is my best description on what type of music I want to listen to on this hifi system.

I do like the sound of Quad ESL 57 ´s ....

[BeDome]

I have been listening to open baffle for about eight years. I have tried everything from hell to breakfast and found that one low resonance fifteen and one mid resonance fifteen both facing forward, and one eight inch fullranger angled up with dual super tweets (one forward facing and one back facing) seems to work the best.

I use this system for close field listening when I have absolute quiet.


NOW, When I want to shake the floor, another system works better.

Sorry to spoil your fun, but open box quality and seriously badass, rock the whole house are two different things

[runblader]

Hello BeDome:


Do you mean to say that my plans of installing one altec fullrange driver in a single open baffle solution is not good at all ?

No harm taken by what you said ... I will use this setup exactly like you do yourself....

[runblader]

Not much response here

I´ve tried to figure out some things on my own. did not work too well...

uhm.. can I start over again ?

I do love SCIFI movies : bladerunner - my "nick" : is one of my faves.
I started this thread by quoting gill scott heron: "I´m new here" - one of my favorite songs at the moment.

I´m a vintage hifi fanatic. an amateur ... but I´m still quite a bit over "normal" when it comes to my interest in vintage hifi equipment.

Today I own : Quad Esl 57´s and Goodmans Triaxioms ... latest addition : the Altec 604E´s....

I do like DIY stuff.


If I was to skip everything in my first post I would just ask :

1. The OB´s like the ones on this site : http://jelabsarch.blogspot.no/2012/06/open-baffle.html - will these work with a N1600-16 crossover from GPA ? - or will I need another type of crossover ?



- runblader

[Mr. Widget]

If I had something constructive to tell you I would... unfortunately I have never heard an open baffle dynamic speaker that I liked. Of course that is just one person's opinion.

Personally, I'd stick with the Quads... add a ribbon and a quality sub and be pretty happy.



Widget

[runblader]

Thanks for both of your comments Mr. Widget at least you tried to help !

I sent a email to someone that knows altec stuff : got a quick replay too !

so to answer my own question : if anyone´s wondering : this GPA N1600-16 crossover will work with OB´s.

I do NOT think I will post anything more on this site.


bye bye !

[BeDome]

Hello BeDome:


Do you mean to say that my plans of installing one altec fullrange driver in a single open baffle solution is not good at all ?

No harm taken by what you said ... I will use this setup exactly like you do yourself....

I would not say that it would not work! I have only heard 604s one time and they were quite impressive. The guy had reworked the crossovers some and added a subwoofer to get the bass he desired.

As I remember the Qts of these drivers are a little too low to work well in an open baffle without some EQ help on the bottom. Again, you have to carefully watch for over excursion. These are too nice of drivers to bang up by overdoing the EQ to get them to hit big lows in an OB set up.


That is precisely why my OBs are set up using a single eight inch driver for "full range" and I use dual 15" drivers per side for bass extension. Of course, my approach completely destroys the desired Point Source sound attainable by a single 604 pair or other nice co-axials.

Wood is cheap. Cut some and have fun!

One thing I would add that I have learned, though, is to place your drivers off center of the baffles. Otherwise you will have a specific dip in response (half wavelength from driver to edge of baffle where near perfect cancellation occurs). By placing it off center you have a much larger range of frequencies where cancellation can occur, thus "smoothing out" that one perfect dip in response.

[BeDome]

I have just barely been in touch with parameters, and understanding parameters on speakers.

1 .Now the Qts parameter you´re talking about: do you think GPA have this exact measurement ?
I mean since I´ve had both my 604E´s serviced by them...

2. Do you think if I had both these parameters and the layout of my crossover I would manage to figure this out ?

- runblader

Your questions are important and may be of interest to many more. If you do not mind, I will quote pertinent portions of your message and answer them, as well as I can in the general forum.

T/S parameters for your serviced drivers might be available at Great Plains Audio. It is worth searching. I think I remember 604s as being in the mid two range. There are a number of sites, including this one I think, that detail the measurement of parameters. It takes some time, but it is not hard at all.

Most generally successful open baffle drivers' Qts fall in the high .5 to (best) .707 or .8 range. Thus these are kind of rare in most JBL or Altec Lansing efforts due to their use of very strong magnets, extremely tight flux gaps and tightly formed voice coils (all of which design parameters happen to be great for higher power handling, lower distortion, and work great with well tuned enclosures, responding very well to typical solid state amplifiers).

So, your drivers used in an open baffle will require a bit of equalization on the lower range to sound flat. Fine, unless you are a minimalist who uses no such devices in the audio stream.

Just be very careful to observe excursion limits. Your drivers are far too rare and valuable to beat them up by trying to get big deep bass in an open baffle. Better to add a subwoofer for low bass and allow your prime drivers to just do upper and mid bass maintaining your best point source performance for 95 % of your program material.





I may have repeated the important points .... seemed important.

I have one of these on each side ....


http://www.parts-express.com/pe/show...number=295-455

... and another more expensive from Jamo with a resonance of 15Hz, with a more incredible excursion of an inch and one half, Qts of .69 - close to great for OB.

If I was able to allow the space, I would've doubled the driver compliment angling them front and back to help eliminate any non

-linearities the individual drivers alone can create.

But 4 15s in a small room is already pushing it, with WAF.

[BeDome]

I am sorry, but the guy who always re-worked crossovers to his own taste and helped me for several years, died four months ago, rather suddenly, and I will always will always wish that I had picked his brain more and tried to understand his processes more fully.

I only have a basic understanding of how to properly set up the "perfect" crossover, but I am still trying and learning with every mistake. I can only recommend a similar approach until you can find your own mentor ... then hang on his every word and make sure you get what he is saying!!

I will help all I can, but I am sure that others here have more to offer.

You are in the right place for your questions.


Do not say, "bye bye," just yet.

[runblader]

Hello all,

Thank you for all your information BeDome


I have done some research and written some emails: I think I got some information to share :

1. I´ve been told that I should consider an active high pass filter.

2. I am thinking initially to use a pair of 15 inch woofers in box. I do not think considering the WAF that I should make OB´s with two 15 inches each ... You are right in your conclusion about that BeDome ...

3. I have then also then the opportunity to search wider to find a subwoofer pair , right ?


- runblader

[BeDome]

Hello all,

Thank you for all your information BeDome


I have done some research and written some emails: I think I got some information to share :

1. I´ve been told that I should consider an active high pass filter.

2. I am thinking initially to use a pair of 15 inch woofers in box. I do not think considering the WAF that I should make OB´s with two 15 inches each ... You are right in your conclusion about that BeDome ...

3. I have then also then the opportunity to search wider to find a subwoofer pair , right ?


- runblader

An active High Pass Filter will further protect your "delicious" primary full range drivers, your Altec 604 pair from over-excursion, often choosing 24dB/Octave (or often more steep, digitally).

For my vote, a pair of subs is a capital YES. OB just seems to work better if everything from your sound source is symmetrical and controlled. NOW, If you can angle your "triangle" of speakers and sweet listening spot asymmetrically in your listening room, you are ahead of the game!

So, a dual sub set up makes perfect sense. Enhance your 604s with subs running up to 60Hz or 80Hz, depending on how much more low support you need in YOUR room.

Two sub sources will also be a bit more room filling and often room nodes may seem to be more manageable. (hopefully more usable enhancements than detrimental cancellations - hey, we can dream!)

If you are ready for some more involving/annoying stuff about listening to open back systems, I can share a secret that will strike you as obvious once seeing it in writing.

Open baffle or more accurately OPEN AIR listening is absolutely not possible to achieve inside a room. See how obvious that seems?

GO OUTSIDE! Have a listen to true unobstructed, Open AIR on axis sound in true quiet. You will not ever recover. (Almost impossible where I NOW live, but the original lesson remains a goal to achieve)


... or, adapt the rest of the room to the advantages you have created by unbinding the drivers from their enclosures. The idea being to make sure there are no "short" room reflections hitting you at all. Room acoustics, including carefully placed dispersion or absorption treatments to the front and back walls and a "trick" that I have also learned over the years all can add up to an amazingly open experience in listening, making your speakers truly disappear from your listening space.

Since you can not actually listen in purely unobstructed Open Air, since we live in rooms, use a SOLID, completely separate and movable/re-positionable reflector to help guide rear room reflections to help them cancel each other out as they enter your listening space.

Make a solid reflector that sits a few feet back from your speakers and some odd distance from your back wall. Distances to be determined by the interference, resonances and "room nodes" you can hear annoying you still.

I built a solid MDF stack, avoiding 90, 60 and 30 degree angles, all of which are factors of 90/180/ 360 room angles.

I chose 82 by 65 by 33 degrees as a solid stack of MDF (about ninety pounds of stuff, it must be only slightly reflective, more an air bender than a sound reflector, because you are mainly fighting against low frequency nodes, hence MDF - I covered two sides with absorbent - four feet high (just shorter than the driver compliment) to act as enhanced room improvements, directing any short distance reflections toward an absorbent surface, going along with what you have set as dispersion elements behind and around you. The idea is to ensure that you eliminate as many short reflection times between you, your walls and your speakers as possible.

Hope it makes sense in my simple words, Otherwise, digest some of Ethan Winer, Steve Deckert, Linkwitz papers on how your own room fights you in creating a high resolution reproduction system, which simply MUST include a room along with all of its shortcomings.

Hope some of that helps you. There is quite a bit to open air listening, as those early explorers (Even Edison) determined.

[runblader]

Hello,

Just wanted to inform that I´m stopping this project.


Many reasons: (sure thing, I can give you some reasons )

1. first time trying to understand T/S parameters. I´m a NEWBIE.
2. without having anything to measure frequency and all the rest (that I don´t understand much about ) I´ve been advised not to do this.
3. don´t have the money to buy a measuring system... CLIO and similar...


Thanks BeDome for cheering on this project...

[BeDome]

Hello,

Just wanted to inform that I´m stopping this project.


Many reasons: (sure thing, I can give you some reasons )

1. first time trying to understand T/S parameters. I´m a NEWBIE.
2. without having anything to measure frequency and all the rest (that I don´t understand much about ) I´ve been advised not to do this.
3. don´t have the money to buy a measuring system... CLIO and similar...


Thanks BeDome for cheering on this project...

You probably already have two of the most sensitive, highly performing detection devices and an analysis device that no thousand computers can even come close to.

Your best tools, no matter how many graphs you make using advanced measuring systems are still your two ears and your brain. It is your taste which has to be pleased in the long run.

Yes, the learning curve can be steep, figuring out what you are hearing, but the rewards are lifelong or, as some see it, a curse you may never survive.

I would not give up playing with your 604s just because you can not confirm how pleased you are with the results, using a scientific graph looking thing.