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Old 14th May 2007, 09:23 PM   #1
maghen is offline maghen  Sweden
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Default which loudspeaker design?

Hello,

After a couple of (imho) quite successful builds a few years back I am now planning a new loudspeaker build.
I hope for some help in deciding what kind of loudspeaker to choose.
Drivers and filters should not cost much more than $1000, and I find it much more exciting to try something new rather than a proven traditional design.

The speakers are going to be used in a fairly small room, and I appreciate tight "dry" bass before anything blurry. Quick response is more important than deep bass. I really like a clear, transparent sound.

Up until now i have preferred sealed boxes with two way systems, and very simple crossovers. I don't like small speakers that are made to "sound bigger than they are" since I believe it often leads to a blurry slow bass. Deep bass is of course not bad, as long as it is tight!

So, does anyone have any suggestions? Should I perhaps not give up the traditional vented box?
How about a "transmission line"?
Quarter wave pipes??
or perhaps an open baffle dipole? I am for instance very curious about the budget types suggested by S. linkwitz (cheaper variants of the "phoenix".)

thanks in advance,
Magnus
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Old 14th May 2007, 10:53 PM   #2
Zarathu is offline Zarathu  United States
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Line Array. Email me if you want pictures of my design.
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Old 15th May 2007, 11:08 AM   #3
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I designed this speaker using Aurum Cantus 8" woofer and 5 1/4 " drivers both carbon fiber. Tweeter is an Usher 9950-20.

My best sounding speaker so far, it achieves what you are looking for.

The cabinet is tapered front to rear and is canted 5 degrees rearward. I have a few construction pics along with crossover details and would be glad to help with any other info if you're interested.
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Old 15th May 2007, 11:33 AM   #4
OzMikeH is offline OzMikeH  Australia
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Fostex Fe206E in a Bruce? Look at spawn of Frugalhorn. Phase plugs are essential. No crossovers to mess with, amazing vocals, 95dB/W/m so not a lot of power required. Plenty of cheap tweaks around for the fostex drivers.
That will cost you about $500 with wood and some basic finishing paid for.

then spend the other $500 on a 12 inch Sealed Rythmik servo sub for 40Hz to 20Hz. ($450 for speaker and amp, $50 on an ugly cabinet shaped to hide under the couch.)

Is that different enough for you?
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Old 15th May 2007, 02:10 PM   #5
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What about... a non-standard alignment, such as: a centre tweeter surrounded by a circular array of 6 low-cost midranges? It would be like a co-axial design but with the option of using a decent tweeter, the speed and accuracy of small midrange units, and the imaging qualities of a large wave-front all rolled into one design

Edit: however, I am actually in the middle of writing up some plans for a traditional 3-way design. I plan on using 10" woofers in sealed boxes, as I think that the roll-off from that size would blend quite well with the room gain of a typical living room.

Anything larger and room nodes are accentuated or the room is unnaturally pressurized, whereas an 8" doesn't go low enough unless it's in a ported box.
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Old 15th May 2007, 05:36 PM   #6
tinitus is offline tinitus  Europe
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Tight bass ?? - I am sure this will

http://www.troelsgravesen.dk/TJL3W.htm
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Old 15th May 2007, 09:31 PM   #7
maghen is offline maghen  Sweden
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Quote:
Originally posted by Zarathu
Line Array. Email me if you want pictures of my design.
OK, those are interesting. What are the pros and cons with line arrays? I believe I have read somewhere that one shoud have enough distance to the line arrays to get the right sound. Could this be a problem in a small room?

Thanks for the input!
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Old 15th May 2007, 09:31 PM   #8
maghen is offline maghen  Sweden
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Quote:
Originally posted by OzMikeH
Fostex Fe206E in a Bruce? Look at spawn of Frugalhorn. Phase plugs are essential. No crossovers to mess with, amazing vocals, 95dB/W/m so not a lot of power required. Plenty of cheap tweaks around for the fostex drivers.
That will cost you about $500 with wood and some basic finishing paid for.

then spend the other $500 on a 12 inch Sealed Rythmik servo sub for 40Hz to 20Hz. ($450 for speaker and amp, $50 on an ugly cabinet shaped to hide under the couch.)

Is that different enough for you?
Hmm... English is clearly not my first language... What is a Bruce? "spawn of Frugalhorn"??? I guess you are talking about a broadband speaker? Could be interesting!

Thanks, please explain further
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Old 15th May 2007, 09:31 PM   #9
maghen is offline maghen  Sweden
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Quote:
Originally posted by CeramicMan
What about... a non-standard alignment, such as: a centre tweeter surrounded by a circular array of 6 low-cost midranges? It would be like a co-axial design but with the option of using a decent tweeter, the speed and accuracy of small midrange units, and the imaging qualities of a large wave-front all rolled into one design
Now this is interesting!! I really like that idea. I'm thinking cast concrete box, perhaps spherical... closed or vented?
What could I expect from such "fly eye" speakers? Could someone with better knowledge than me judge the qualities of the design? Theoretical pros and cons?
This one got me excited!

Thanks,
/Magnus
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Old 15th May 2007, 11:17 PM   #10
Zarathu is offline Zarathu  United States
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Default Practical Nearfield Line Arrays

I'm extremely biased to line arrays. Having gone to arrays, everything is JUST MINIATURE DANCING FROG MUSIC......to me.

Near Field Line Array
Dr. James Griffin has done much to advance the line array concept. His original white paper was the definitive line array theory resource. Jim has recently completed an updated, revised edition of his Design Guidelines for Practical Near Field Line Arrays white paper.

Those wishing to explore the inner workings of the line array concept in detail are encouraged to download Dr. Griffin's White Paper (306kb).

http://www.audiodiycentral.com/awpapers.shtml

No one currently even considers building line arrays for in house sound reproduction without following Dr. Griffin's paper.

I built one of these:

http://pub48.bravenet.com/photocente...31&album=48032

I'm extremely biased. Been to most other stuff. Wanted something that was as realistic to a real performance as possible.

Design Guidelines:

The Calipso Array has been developed on a model that includes the following essential characteristics:

Two 12 inch 15mm Xmax GoldSOund Woofers

34 Sammi 3.3mm X-max, Copper coils, composite paper/fab cone, mid woofers

60 Dayton ND20FA tweeters with flanges cut to a .9 inch Center-to-center distance

Rane Ac-23 Analog Electronic Crossovers, at 165 & 2600

Tri-amplification: 60 w/ch for tweeter array, 150 w/ch mid/woofer array, 350 w/ch woofers

1. Three-Way design.

In point source speaker systems, a two way design is often considered to be an inadequate compromise. Much of audio has gone to two way designs with a single sub woofer. Vance Dickason in his 6th Edition of The Loudspeaker Cookbook has indicated that the use of dual woofers that are capable of subwoofer frequencies produces a significantly better sound image than a subwoofer. In this design a large 12 inch, high mm Xmax woofer is used with each side, and it crosses to the mid ranges at about 165hz. While mine are not currently in the correct size box, the correct size is a 6-8 cu ft vented box.

2. No Crossover in the most sensitive areas of human hearing.

Rod Elliot at Southwest Audio( http://sound.westhost.com/bi-amp2.htm ) makes the case better than I:
“It is not at all uncommon to see systems where the crossover frequency is set right in the middle of what I call the "intelligence band". This is the range of frequencies from 300Hz to 3600Hz, and is extremely important from a psycho-acoustic point of view.
“It is no accident that this is the range of the telephone system (and has been for many years). If we are only to hear a limited range, then this band of frequencies is by far the most important. Just from this we can recognize a person's voice, which musical instrument is being played (even bass instruments!), and - more importantly - what is being said. It contains nearly all the "intelligence" of the sound, which is to say that if this band is "corrupted", intelligibility is greatly reduced.
“So why do speaker manufacturers insist on placing their crossover frequencies within this band of frequencies? The public address (PA) systems used by many rock bands are a case in point - how often does one find that the vocals are completely unintelligible? Mind you, it may also be the case that the band's lyrics just don't make sense, but that's another story altogether.
“Often this occurs because the system is so loud that the amplifiers are clipping badly, but even at lower levels it is quite common. Place a common-or-garden crossover filter right in the middle of the "intelligence band" and this is exactly what will (and does) happen. With phase aberrations and cancellations, this most important frequency range becomes muddied and indistinct causing loss of intelligibility - not only on voice, but instruments as well.
“The effect is also noticeable with some hi-fi speaker systems, except that it usually less pronounced, and it is far less likely that the amplifier will be driven to clipping. Reviewers will often say of a speaker that the vocals seem veiled, or that there is noticeable coloration of either male or female vocals. These effects are often caused by the effects of phase shift around the crossover frequency, coupled with the fact that the crossover frequency falls right in the middle of the intelligence band.”
This very hard to do with point source speakers, but with line arrays, the midrange speakers are often loafing along, and if they have the range, pulling the wagon as a group of horses, they can do the job admirably.

3. Use Electrical Crossovers.
Again, passive crossovers are, IMO, a DATED TECHNOLOGY. Passive’s introduce so much negative into the sound that they should not be there. And the cost of a top of the line passive cross(with the increased cost of copper) and a electronic is almost the same. Read Rod Elliot’s papers on Bi-Amplification and electronic crossovers at http://sound.westhost.com
The only reason for not using them is that you’ve spent years learning how to design them and you aren’t giving that up, or you are in the business of selling speakers and you aren’t willing to sell amps and crossovers too.

4. Separate the midrange speakers from all other influences.
Bad coloration of sound, in my opinion, is caused by other sound that the direct radiation coming through the speakers. This means that you have to eliminate ANYTHING that goes out the back of the speaker, and anything that might be in the box behind the speaker from coming forward through the speaker again and muddying the sound clarity. (Some people don’t believe that this is impactive.)
To do this, this design uses SEALED separate 4 inch PVC tubes for each of the 34 midrange/mid bass speakers. Each tube is physically separates from its peers by ¾ inch of open air space.
On page 35 of the Dickason 6th Edition Loudspeaker Cookbook, there is an empirical study on the efficiency of various stuffing materials. The greatest attenuation was determined to be at the 4 lb/cu ft density level. Frequencies within the range of the mid/midbass speaker are right within the range of attenuation. Only by using tubes can the appropriate density be achieved, since the insulation can be stuff tightly against the walls of the tube and not push up against the speaker itself. The part closest to the speaker is protected by a layer of sheet pillowfill from the fiberglass threads that might otherwise get into the voice coil.
A recent study by Rod Elliot showed that the smaller the diameter of the fiber the more effective the attenuation. Pillow fill= .01 in, regualr fiberglass=.005 in, Acoustical fiberglass= .001 inch
Additionally there are some benefits of the tube’s inability to make even ordered harmonics, or even ordered harmonic distortion, but that will not be addressed here.

This design is labor intense but it helps make the 3 inch midrange speaker process viable.

5. Keep the cost down below $1400 for the speakers, and the required electronics.

6. Keep Comb distortion in the mid and high frequency drivers below Griffin minimums, and use dome tweeter SOUND rather than ribbons or planars, for their flatter frequency response.
The only dome tweeters that I know which have a center to center distance small enough, and at the same time can be crossed low enough, are Dayton Neo ND20FA’s. These have their flanges cut so that the c-to-c is .9 inch, and the comb filter distortion doesn’t start until more than half way into the last octave, or more than 15,000Khz.

All statements except for referred to studies or references are my opinion.


Zarathu
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