[MJK]

I have posted a new article on my site documenting an OB speaker design study I have been working on for the past six months. Basically it shows some of the trade-offs that need to be made to select an appropriate woofer driver, baffle size, and crossover to produce a balanced SPL system response. If interested, you can find it under the General Speaker Related Articles link.

[Scott F.]

Very nice job Martin 

I still haven't had the gumption to try a true open baffle (including the woofer). One of these days I may start playing around with it after I've had my fill of the BR bass. Your article will be a good guide for where I need to start 

[opnly bafld]

Very nice job Martin 

I still haven't had the gumption to try a true open baffle (including the woofer). One of these days I may start playing around with it after I've had my fill of the BR bass. Your article will be a good guide for where I need to start 

Have you had a chance to listen to Bob's system?
OB bass is 

Martin,
Thanks for taking the time to research and document the information.

Lin

[Scott F.]

Have you had a chance to listen to Bob's system?
OB bass is 

Yeah Bob, wheres the invite   

[Danny Richie]

Hey Martin,

I noticed a couple of things that I would like to point out to you.

1. There is no "T" in Danny Richie

2. Our OB-5 and OB-7 designs are completely passive. No active crossovers or EQ filters are needed.

[MJK]

Danny,

Sorry about the mistakes, I'll update the article tomorrow.

Martin

[Bob in St. Louis]

Have you had a chance to listen to Bob's system?
OB bass is 

Yeah Bob, wheres the invite   

Lin, Thanks for the complement man. 
Scott, Regarding the invite: I suppose "third times a charm" as they say. 
Martin, Thanks for the article. Skimmed so far. Will re-read when time allows.

Bob

[Bob in St. Louis]

Martin,
If I may, with all due respect, I'd like to make a correction regarding the Hawthorne Audio Duet.

Found in your first paragraph regarding Active XO'd OB's:
Each features active crossovers and EQ filters requiring at least two amplifiers.

And in comparison the passive XO'd OB's found in your second paragraph:
Being passive crossover designs, these speakers do not have requirements for sophisticated electronic filters and multiple amplifiers.

You are correct in that the Duets do not require "sophisticated electronic filters", but they do require two forms of amplification. The top driver is a coaxial design. A 'mid-woofer' with a compression tweeter in the rear. These are the two drivers that required the built-in (and included) XO network. The lower driver "Augie" (bass augmentation driver) is a stand alone driver. Meaning it is in no way "electrically associated" with the top driver(s). No XO exists between the Augie and upper Coaxial unit.
So minimun two channels of amplification are needed for a pair of Duets.

A factory build pair of Duets come equipped with three sets of inputs on the back panel. Minimum of two are required to power all of the drivers. However, some folks choose to eliminate the factory XO and utilize the third set of inputs jacks to effectively tri-amp. Powering the compression tweeter separately.
With this option, a third amplifier would be needed.

Duets can be very simple in implementation, or as complicated and complex as the user wishes.
Versatility, and adjustability at it's best. 

Thank you for your time Sir. Hopefully I've explained well enough.


Bob

[MJK]

Bob.

Thanks for the heads-up. I'll swap the reference to the Hawthorne Audio Solo.

I am taking lots of flack over this article, what a pain. I think this will be the last document I write on OB speakers for quite a while. I'll go back to TL's and horns.   

Martin

[Bob in St. Louis]

I think this will be the last document I write on OB speakers for quite a while. I'll go back to TL's and horns. 

No Sir... Don't you dare.   
In fact, I'd love to see what you could do with a bare pair of Hawthorne Audio Coaxials and complementing pair of Augie's.
I've been waiting patiently a very long time for this. 

Bob

[MJK]

In fact, I'd love to see what you could do with a bare pair of Hawthorne Audio Coaxials and complementing pair of Augie's.
I've been waiting patiently a very long time for this.

Bob,

I am sorry but I don't think that is going to happen. I have the rough design of the three way OB like the Jamo worked out, I probably will finish that design and then actually build it.

I also have a back loaded horn build started in the basement and plan to spend a lot of time on that set of speakers.

Too many things to do and not enough free time.

Martin

[Bob in St. Louis]

I am sorry but I don't think that is going to happen.

I understand Martin.  No really....  I'll be ok....

Maybe someday. I'm patient. 

What drivers do you have in mind for the three way (or is it a secret)?

Bob

[doorman]

There are a number of drivers and configurations to implement OB's OB's. Coaxial's being only one! The Visatons are worth a listen.
                                                                                    Don

[Bob in St. Louis]

???? What ???? 

[MJK]

What drivers do you have in mind for the three way (or is it a secret)?

Hi Bob,

For right now I am going to keep the limited details I have worked out to myself. This is a project in its early stages and I really don't want to start discussions of how or why I might make any decisions. Heck, even my wife does not know yet (actually, she does not care).

Martin

[Bob in St. Louis]

Martin, Understood. (especially the part about the wife)  Please keep us posted.

Don, Thank you. I've heard them. They do sound very nice, however what I've chosen is what sounded best in my opinion. I've made my decision and have zero desire to switch manufactures. My selfish (jovial) pleading to Martin was merely to see what a man of his calibre is capable of with the drivers I own. Call it, "an experts perspective that relates to me", if you will. I like his open baffle papers and have learned much from his writings.  But will never implement anything he does unless they are with the drivers I have.
(interesting how you were able to change your post without the 'edit' line showing as evidence. Neat trick, I'll have to learn that one.)

Bob

[el`Ol]

In fact, I'd love to see what you could do with a bare pair of Hawthorne Audio Coaxials and complementing pair of Augie's.
I've been waiting patiently a very long time for this. 
Bob

Do these two drivers really belong together?
In my eyes the Silver Iris is for people who have the space for huge OBs and the Augie is for people who can live with lower sensitivity or go active.

[scorpion]

Martin,

I am glad to have put you on this track, excellent paper as usual !
By chance I just got a pair of 15" from Germany for a similar design, A&D 1524, Fs 44, Qts .7 and Cast Frame Basket that will be paired with
Monacor 130X/8 fullrangers passively. All simulated with your Math Cad model and with on paper very similar results. We will see when they are finished. 

/Erling

[Bob in St. Louis]

Do these two drivers really belong together?
In my eyes the Silver Iris is for people who have the space for huge OBs and the Augie is for people who can live with lower sensitivity or go active.

Yes el`Ol, I do believe so. The high sensitivity and precision of a tube amp driven coaxial unit mixed with the large Augie run from a powerful sand amp for lower end, open baffle grunt seems a match made in Heaven. Multiple Augie's per channel help raise the effective sensitivity as well. I have no complaints el`Ol, and from the folks that have heard the system they didn't seem to have any concerns regarding the synergy of the two drivers.
Regarding the size of the drivers, yea they aren't small by driver standards, but when you look at the required baffle size of an 8 or 10" driver, in some cases the Hawthorne drivers can actually have a smaller footprint. I've run the Coaxials "baffleless" (mounted like a stop sign), crossed the Augie's over a little higher and had amazing imaging and crystal clear clarity. Something that in my opinion diminishes as the baffle size increases. My current 'baffle' consists of a 2" ring around the coaxial driver so my baffle width is 19" wide. The Augie baffles are 21" wide.

Bob

[el`Ol]

I just visited the Hawthorne Audio website and saw they now also have a 10" coaxial. Better than letting a 15" run into the midrange in principle. But what I don`t understand: Why do they sacrifice sensitivity due to an Fs of 40Hz (knowing almost nobody of their customers uses them in large baffles)?