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Multi-Way Conventional loudspeakers with crossovers

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Old 15th February 2008, 01:07 PM   #3101
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Brett that's a pretty strict standard. I don't think I've seen one speaker diy or commercial that can fit that requirement, except maybe Maggies or other electrostats. Do you think combing is a real problem? I always thought it was, but Lynn doesn't seem to bothered with it. This hobby is pretty new to me so I don't really know one way or the other.
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Old 15th February 2008, 01:34 PM   #3102
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Hi dobias,

You can use the second (lower) driver to increase bass and fill in for baffle step loss by driving it via a series connected choke.
If the choke is air-core and slightly lower in value than optimum, you can use a ferrite rod out of an AM radio to adjust its value for the most satisfactory reproduction this combination is capable of.

If you do this, then the comb/phasing problem, which Brett mentions because it becomes apparent in the vertical plane, will then not arise.

Cheers ......... Graham.
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Old 15th February 2008, 03:27 PM   #3103
dobias is offline dobias  United States
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Default parallel full range speakers

Graham,
I already have a 12" bass only below the 12" full range speaker,
plus an additional 12" bass facing the back. I'm using two 4.2mH air core inductors for the bass units. The front bass sees one coil & the back bass has both coils in series for a lower crossover.

My question was, aside from the reenforcing bass speakers, what advantages or problems would I encounter with two full range speakers (operating full range). They would be in a vertical stack & as close together as possible. Since they're identical units, I didn't think there would be any negative effects, but I'm not certain.
As Brett cautioned,"Once the centre-centre distances are > 0.25 wavelength, cancellation (combfiltering) will occur." I can only say, "Huh?". I admit I'm out of my league with this group's knowledge on the subject.
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Old 15th February 2008, 03:47 PM   #3104
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Post #3113
Hi Dobias,

This is something best understood through personal experience.

Set your FM tuner (if it does not mute) so that you can listen to interstation hiss.

If your front loudspeakers are connected in parallel full-range with a centre distance of say 13", where the wavelength frequency is 1kHz, you are going to hear considerable upper-mid and treble level changes as you move your head up and down about their common axis.

With sine driving, these amplitude peaks and troughs will be in different places at different frequencies as you move up and down (comb effect) and be closer together with increasing frequency.

(Or turn your LS on its side and listen to the effect as you walk past it.)

This is why larger loudspeakers are generally not used for mid frequencies - the output from both sides of the cone destructively interfere as soon as you go off axis, thus the HF/mids fall away quite notably. There can also be a central beaming effect unless countered by other aspects of design.

Cheers .......... Graham.
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Old 15th February 2008, 04:17 PM   #3105
dobias is offline dobias  United States
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Default parallel full range speakers

Graham,
Thanks for the excellent description that even I can understand.
OK, my executive decision is to forget about using two full range speakers together!
This group is great.
dobias
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Old 15th February 2008, 04:35 PM   #3106
dmason is offline dmason  United States
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I have had the Tone Tubby Alnico 12's on test baffles of 24"^2 for a couple days now, and am pleased to report that these drivers are stunningly musical for prerecorded music, completely captivating presentation, and I can vouch for them easily, as midbass drivers. In fact, with some form of treble augmentation, they would sound great pretty much just as they are. Magnetar reports great success with the rather inexpensive B&C DE-10 compression driver, and Eminence APT waveguide.

I am sorely tempted to cut dust caps and make for phase plugs, but, the Tubbys, STAY!
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Old 15th February 2008, 06:07 PM   #3107
bjorno is offline bjorno  Sweden
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Hi,

FYI, 2 crude theoretical point source simulations aligning with Grahams Post #3113:

b

1(2)
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Old 15th February 2008, 06:11 PM   #3108
bjorno is offline bjorno  Sweden
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2(2)
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File Type: gif 2x12in_dipole-stereo_arr.gif (97.5 KB, 821 views)
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Old 15th February 2008, 06:38 PM   #3109
KCHANG is offline KCHANG  United States
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Hi Doc,

How do the Tubbys compare to the Coral 12" drivers?

My most recent OB configuration uses the Fostex FE208Sigmas (got them for free from Nelson Pass at the "Burning Amp" event, thanks Nelson!), and has two 15" woofers (with active EQ and horizontally aligned) on each OB. This combination does a much better imitation of real concert sound than my other OB projects using smaller FR drivers. I just participated in two performances of Carmina Burana last week, with ~ 240 singers on the stage and a full orchestra. When I played the Ozawa 1965 recording of this music through the OB speakers, I was quite happy to discover that the OB speakers actually were able to give a decent hint of the real sound, including the weight of human voices and the impact of the bass and percussion.

Cheers,

Kurt
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Old 15th February 2008, 06:42 PM   #3110
riff.ca is offline riff.ca  Canada
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Magnetar: I appreciate the condolences! Sucks but in the end I got drivers that rock so it's all good. The Seleniums sound great to me! Adding them has taken the system to whole other place. I'm feeling quite privileged, the entire system sounds astonishingly good. I don't think many people ever get to hear recorded music presented at this level. Thanks for blazing a trail I could follow, for sure I owe you some beers.

Lynn: Thanks for the lengthy reply! I do realize time alignment and rapid decay are two different things, just one got me thinking about the other. Two thinks I suspected are, I believe, confirmed. 1) We have almost no idea how important time alignment is. 2) Any attempt at absolute time align is compromised at best.

The link to your site provided lots of interesting reading. I especially enjoyed the short history of hi-fi. Interesting how audio consumers have been lead around by the nose going exactly where the big money players want us. I've been in the same position you mention auditioning a SS amp with a group and being the only one who thought it was horrid! That was years ago and it was kind of lonely. I realized much later that a pair of La Scalas and a Crown DC-300A drove me away from listening to recorded music for several years. During the same time period there was a serious push to sell SS to guitarists. Thankfully I have no memory of a group of players raving over the latest SS turd.
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