[JohnR]

Just wait - the Geddes hordes will be gathering forces.

[SoCalWJS]

Just wait - the Geddes hordes will be gathering forces.

...... give 'em time. 

[SoCalWJS]

Can't believe no new replies this morning 

..... it's early.

I remember going to an audio show many years ago and one of the seminars was on speaker design. I can't remember all of the panelists, but Jim Theil and Richard Vandersteen were two of them as I recall. The person doing the introductions made a statement that there were many different philosophies regarding the basic design of speakers, and there was no one absolute correct way of accomplishing the goal of a high end speaker.

It became obvious very quickly that no 2 designers agreed on everything. Theil liked his 1st order crossovers and was getting into absolute phase coherence. Others said that the problems that were introduced by 1st order crossovers can't be overcome. It was an interersesting session, but all of these people were passionate in their ideas about speaker designs, and there were a few times that it fel like it was getting a little hot in there and curt answers were being given in response to another designer/manufacturer questioning another design.

Educational: yes.

Settling on a single design philosopy: absolutely not.

[J Fallows]

 The best thing is that there are lots of different ideas. Lots of things left to try.
If all of this was settled, then that would be real boring and we could all just go home.

Hey, if it's speakers, I'm really interested. 

[Danny Richie]

Can't believe no new replies this morning 

I've been in church all morning.    And your new post was made pretty late in the day last night.

[S Clark]

I know that we have supposedly moved on to drivers, but I got an offer yesterday that forces me to reopen cabinets.  A local custom wood furniture/display manufacturer offered me all of the high quality 1/2" maple plywood scrap that I want whenever I want it.  So I've been thinking... a layer of ply, a layer of linoleum tiles, a layer of1/2" hdf, a layer of tiles, and another layer of ply.  And what if the inner ply was a mosaic of pieces rather than a continous sheet...
Any suggestions on something better out of common materials???  Then we can get on the coming defense of Geddes as the be all and end all.

[Russell Dawkins]

..... it's early.

I remember going to an audio show many years ago and one of the seminars was on speaker design. I can't remember all of the panelists, but Jim Theil and Richard Vandersteen were two of them as I recall. The person doing the introductions made a statement that there were many different philosophies regarding the basic design of speakers, and there was no one absolute correct way of accomplishing the goal of a high end speaker.

It became obvious very quickly that no 2 designers agreed on everything. Theil liked his 1st order crossovers and was getting into absolute phase coherence. Others said that the problems that were introduced by 1st order crossovers can't be overcome. It was an interersesting session, but all of these people were passionate in their ideas about speaker designs, and there were a few times that it fel like it was getting a little hot in there and curt answers were being given in response to another designer/manufacturer questioning another design.

Educational: yes.

Settling on a single design philosopy: absolutely not.

I've never seen a degree program specifically on loudspeaker engineering.

I think this is one area where engineering meets art.

[SoCalWJS]

I've never seen a degree program specifically on loudspeaker engineering.

I think this is one area where engineering meets art.

This was mentioned repeatedly in the seminar and where the viewpoints of those involved diverged the most. One (and I can't remember who it was) said that the art of the design along with the designer's listening impressions were by far the most important factors. He came across as believing the engineering aspect was just not that important. 

[J Fallows]

Engineering may concern tuning much of what has already been tried.
The art part is probably about things that have not been tried. An artist tries something first, usually rough.
And then an engineer, using the tools of the trade, helps with the execution.
Sometimes the artist and the engineer are the same person. A renaissance man...or woman.

[konut]

And then theres the engineer who gets lucky and tries something that shouldn't really work that well, but does. Bob Smith uses a wave guide that should be way too shallow to control frequencies of the tweeter down to 800hz but the power response matches the woofer so well, at that frequency, that it doesn't seem to matter that much on the Timepiece Mini.

[Russell Dawkins]

I think luck, intuition, pattern recognition and observational skills are all on the "art" side of the design formula. Engineering skills help with the application of what is observed to the design in progress.

[Danny Richie]

Okay guys, I finally have a few minutes.

I had an audio interview last year that I recently posted a link to:

http://www.audiocircle.com/index.php?topic=102655.0

In the interview I was asked about first order crossovers. My response was very similar to much of what Turbo has just mentioned.

To further expand on that subject I will add a few thoughts.

In theory there are advantages but rarely is a designed executed in such a way that there are not other problems that negate all or part of the original design goals.

Here is a good example. This is a Spica TC-50.



See what the upgrade that I designed for it involved and how the crossover was changed. See before and after measured responses too.

And for what it's worth, my A/V-1 speaker (compared side by side) imaged much better despite the time alignment of the drivers in the Spica.

Typically I see a speaker using first order slopes and claiming to have time aligned drivers and all the befits that goes along with that.... but then the surface reflections of the front baffle create the same time delayed reflections that they think they got away from with the first order crossover.

At least the Spica did cover the front baffle with felt. 

Also note the example shown and its measurements regarding off axis response. The measurements really tell a tale.

Keep in mind that what we really hear is a combination of the speaker and the speakers interaction with the room. Some call it a room response or power response. This is typically where the first orders slopes cause problems.

The gradual roll offs of the woofer into the tweeter and tweeter into the woofer means a lot of overlap or both drivers covering the same areas. When this happens you can wind up being in phase on axis and have a smooth on axis response. But then just above the tweeter axis they may be very out of phase. This is especially true in the upper ranges.

Let's say that the crossover point is 2,500Hz and first order. The woofer is only 12db down (or less) at 5kHz. At 5kHz the wavelengths are much shorter and just a slight phase rotation (change in driver alignment) will cause cancellation.

So there is a hole in the vertical off axis up and down and that un-even response will be reflected in the floor and ceiling reflections, and especially in the ceiling reflections So the in room response may look rough even though the on axis is advertised as very smooth.

Now you can get away with using first order crossovers very effectively in the ranges below 200Hz. Down here the wavelengths are so long even extreme vertical changes only cause a very slight phase rotation.

I could cover a lot more on this but Turbo covered a lot of it very well already.

More to come...
 

[Danny Richie]

Another problem that I see a lot with any speaker using first order crossovers (especially a two way design) is that very few woofers out there can be used with only a first order crossover as most show some level of upper range break up that is not controlled by the crossover. So you get a bunch of ringing in the upper ranges.

I have measured responses of a lot of commercial speakers that include some that boost first order crossovers. Most of them have this problem.

Quite often companies bring in speakers for me to measure and test for them. I then give them evaluations and recommendations. All of the data is therefor private. So I can post measurements as examples but can't tell you what speakers they are.

[totoro]

Just wait - the Geddes hordes will be gathering forces.

Heh. All I could think of when reading your post was this:

“The greatest happiness is to vanquish your enemies, to chase them before you, to rob them of their wealth, to see those dear to them bathed in tears, to clasp to your bosom their wives and daughters.”

--Genghis Khan

[totoro]

Have any of you knowledgeable people played with or thought about the Beyma tpl-150h? Hopefully I don't come across as a member of the Geddes horde for mentioning a horn .

[Russell Dawkins]

Have any of you knowledgeable people played with or thought about the Beyma tpl-150h? Hopefully I don't come across as a member of the Geddes horde for mentioning a horn .

see second last paragraph in reply #150 above ^

[AJinFLA]

Keep in mind that what we really hear is a combination of the speaker and the speakers interaction with the room. Some call it a room response or power response.

Couldn't agree more Dan. But I'd go further and state that what you perceive at the listening position in a reverberant room, is the sum of all the parts+.
It's not just the overbuilt beyond audibly benign cabinet or the latest/greatest driver or connector, but everything. The whole kit and caboodle. I know many tend to obsess over the minutiae while missing the forest..and I'm not saying individual parts don't matter - they do, but nothing changes the fact that you hear the entire stereo soundfield (pardon the pun), not the individual pieces that go into a product. Perception at the LP includes everything in the speaker/room produced soundfield + all the "other" factors, such as aesthetics, expectations, etc, etc.

cheers,

AJ

[freerider]

Heh. All I could think of when reading your post was this:

“The greatest happiness is to vanquish your enemies, to chase them before you, to rob them of their wealth, to see those dear to them bathed in tears, to clasp to your bosom their wives and daughters.”

--Genghis Khan

"What is best in life?"
"To crush your enemies, see them driven before you, and to hear the lamentation of their women." - Conan

Sorry, couldn't help myself.

[Hank]

AJ wrote: 

Perception at the LP includes everything in the speaker/room produced soundfield

I am glad to see one of you gurus mention this, as I think it is overarchingly important.  I've seen poor room acoustics overshadow speaker/crossover designs and heard as large an improvement in the "soundfield" with proper room acoustic treatments as with speaker upgrades.  I tell people to include a figure for room treatments when they formulate a total equipment budget for a listening environment.  I have yet to find anyone who has included room treatments in their plans.  No, I don't sell room treatment products.   I'm just a believer.  Now back to you engineers/artists.

[nickd]

I am a little dissapointed that this thread got side tracked on wire connections, cable, room tretment etc.

Some of you had great input. I enjoyed Danny's last post regarding time alignment as the Spica TC50 and the Theil CS2 were some of the most enjoyable older designs I have owned and admired.

The driver tech-talk seems not to be too popular either I must say, Finding new drivers I like is a personal treasure hunt for me as they seem to make the most difference in any system when properly implemented.

The neo 3's and 8's have blown my mind a few times. The coax driver on the Super V is a find. I can't believe no one brought any new driver tech to the thread.

Regarding the Theil CS2, they spent the longest time in my room of any speaker so far, about 3-4 years I might still have them if the dynamics were not limited by the 1st order crossover.

What they had was a well ballanced tone, Beautiful soundstage and supprising transparency for three drivers in a nicely made box. They made music.

I think I will borrow the Totem Element Series monitors a friend of mine has and see what the latest tech sounds like. They don't use a crossover on the new "Torrent" woofer. I will post what I think after I spend some time with them. Think they will hang with the Super V? me either, but they will be fun to play with.