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Old 24th June 2008, 09:27 PM   #4081
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Quote:
Originally posted by FlorianO


My thoughts exactly -- the 12'' I'm eyeing (as of now) is 12NDA520.

The challenge seems to be finding a CD + WG that would mate it below the onset of cone breakup (aprox 1.2k, guesstimating from the manufacturers graphs). Apparently:
- The XT120 is too small to go that low -- even 18Sound recomm XOing those above 2k
- Ditto for DDS screw-on w. BMS4540ND or mated w. B&C DE250. Not mentioning their recent abysmal quality (see John's report)
- The XT1464 (driven by ND1460A) -- too narrow radiation for home use ....

Maybe the RH horn you found or (yes...) gedlee's WG ? Any other combos you tested and would recommend XOing that low ?

The 1464 may be fine for you. I like a wider sound. There is another 1" 18 Sound horn that will load lower than the XT120 - If you can get it to work well below around 1500 with a 12 it should be fine.
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Old 24th June 2008, 09:49 PM   #4082
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Quote:
Originally posted by LineSource
Hi Magnetar,

On your new 3-way OB with the 21"-Pyle + 12" EV SRO.....
Have you experimented with lowering the bass-midrange Xover point from the current 120Hz to 100Hz and to 80Hz? I would appreciate any time you could put into this experiment and report your impressions. IM (doppler) distortion? Xmax limits? cone cry?

I think speakers are all about voice...80-1,500Hz... and I'm interested in understanding if one 10"-12" speaker can "optimally" accomplish this.

P.S. I would move the amp and Xover PCB from the back of your baffle to a bottom board to avoid any reflections... your EX SRO covers over 1Khz where rear cone reflections can be audible.

Lynn..sorry for the sideline notes.
The SRO mid is a very high energy guitar driver and I put a jensen flexair surround on it to get it to work lower on the baffle and to eliminate (almost all of it) breakup My baffle will not allow it to go below 100 so I don't want a hole in the response there - it is like dead flat now crossing at 120 4th order. So yes, the modified SRO (and most 12's) will go to 80 Hz and cover the voice (at lower power handling) but not on my baffle.

I like the amp hooked to the SRO with 6" of wire - please don't make me any mmore paranoid then I already em
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Old 24th June 2008, 10:05 PM   #4083
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Quote:
Originally posted by swak
If one goes with Magnetar's XO points, one could use a small Fostex above 1.8kHz. The fe108ez is said to have one of the best mid-highs of the bunch. Sensitivity is not up to Lynn's target.

Magnetar: What happened to your Lill Buddy? Is the EV so much better?

Another option could be the Tone Tubby 12" alnico.
The EV has the quality of the Lil Buddy but even better tone plus it is more efficient and will go lower, (and higher) with a nearly flat (like plus/minus 1db) from 120 to 2K. It is more 3D vivid (and more accurate!) in the midrange then the little super quads I have here - they are for sale too
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Old 24th June 2008, 10:26 PM   #4084
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Fostex Fe108EZ in 320Hz waveguide is pretty cool - get rid of dust cap and use a phase plug for best results. Comparable efficiency to PR170M0, more dynamic snap. Haven't cmpared to twin PR170M0 yet but liking the sound compared to single PR170M0/Beyma CP21f for now.

Cheers,
Mike
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Old 24th June 2008, 11:25 PM   #4085
Variac is offline Variac  United States
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Quote:
There is another 1" 18 Sound horn that will load lower than the XT120 - If you can get it to work well below around 1500 with a 12 it should be fine.
This metal one, XT1086, is a lot cooler looking in an open baffle too and goes lower than the smaller 18 sound, A bit more money but not excessive

http://www.loudspeakersplus.com/prod...?specific=1602
they claim to 1200hz


1500hz with constant vert dispersion
and 1400 with constant horiz. dispersion

http://www.eighteensound.com/index.a...roduct&pid=178
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Old 25th June 2008, 12:56 AM   #4086
agent.5 is offline agent.5  United States
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Ordered Altec 288-16H

Lynn,

I included the description that you wrote in my order:

"One pair GPA 288-16H compression drivers with low-power aluminum 16- ohm diaphragm, Tangerine phase plug, Alnico magnet, and no bug screens"

Is there anything else that I need to specify and let Bill of Great Plains know?
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Old 25th June 2008, 06:29 AM   #4087
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Quote:
Originally posted by agent.5

Lynn, I included the description that you wrote in my order:

"One pair GPA 288-16H compression drivers with low-power aluminum 16-ohm diaphragm, Tangerine phase plug, Alnico magnet, and no bug screens"

Is there anything else that I need to specify and let Bill of Great Plains know?
That is the complete description, and you will get the same drivers I'm getting. All you need after that are horns or waveguides that match the 1.4" exit and preferably also match the internal 8-degree, 207 Hz flare of the compression driver. At the bottom of the post, you'll see the mold that Martin is building for the AH-425. Nice autumn weather in Perth, I see.


Quote:
Originally posted by pdan

The one constant for most of this project has been the RAALs, so I assume that these have become the most important aspect of this project. But do they create more problems ( visually and sonically ) than they solve ?

Cilla
Not quite as arbitrary as that. I've never been a fan of the extreme HF of any horn or waveguide, and now that I've gone down the rabbit hole of horn/waveguide design, I have a better idea why. Once the wavelengths start to approach the size of the phase plug, many things go wrong:

1) The wavefront coming out of the phase-plug gets rough thanks to non-summation from the multiple exits - the same problem as line-sources on a much smaller scale.

2) Generation of HOM's gets more severe with higher frequencies (multipath bouncing around inside the horn), which is made worse by the non-coherent wavefront emerging from the phase plug.

3) Distortion from the diaphragm goes up due to ...

4) The gain from the horn/waveguide going down, so that at the highest frequencies there is effectively no horn-gain at all.

5) Diaphragm breakup makes its appearance. Even small-format compression drivers have significantly larger diaphragms than comparable direct-radiators, so diaphragm breakup appears at frequencies 1.5 to 3 times lower than equivalent 1" direct-radiator domes.

6) HF boost equalization in the same frequency range where all of the above effects are happening at once, making them even worse.

So there are things going in the extreme HF of horns and waveguides that don't happen with conventional direct-radiator domes or ribbons. True, these lower-efficiency devices have their own set of problems, mostly with power-handling and lack of headroom, but the impulse response and CSD (of the best examples) is generally superior to horns and waveguides.

Put another way, I'd take a ribbon over a TAD or JBL beryllium compression driver any day of the week - above 10 kHz, that is. The short-wavelength world of the top octave is completely different than the 1~3 kHz world in terms of the best solution for the problem. The power levels are far lower, so low-mass diaphragms with simple, unobstructed emission paths (no phase plugs) are more attractive. This is inherent in the technology.

It is possible to build high-performance horn supertweeters (with smooth response to 30~50 kHz), but I still prefer a ribbon to a Goto or Ale - I've heard them and thought the Japanese exotics were OK, but nothing all that special.

I prefer a driver-centric, bottom-up approach to designing speakers. Other folks take a top-down, an idealized-speaker-should-do-this approach. That's never worked for me, although it works for others. I look at the best available technology (by measurement and audition) for a given portion of the spectrum, and design around that. In terms of measurement and audition, I feel that direct-radiators are the best choice above 10 kHz.

In the 1~10 kHz region, compression drivers play to their strengths, although impulse response with rapid decay characteristics remains the biggest challenge. In the region from the bottom of the spectrum to 300 Hz, direct-radiator woofers are the best choice for anyone who isn't willing to build a garage-sized bass horn. In the 300 Hz to 3 kHz region, direct-radiators and horns are slugging it out, with tradeoffs between distortion, impulse response, headroom, and overall size.
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Old 25th June 2008, 02:00 PM   #4088
pdan is offline pdan  Europe
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Mr Olson,

Thank you for your post, it was very much appreciated.

I was under the impression though, that the RAAL was (is) the White Rabbit that lead you down into the horn labyrinth in the first place, as only compression driven horns are judged to be a suitable sonic match. So it seemed to me that the design has become a matter of the tail wagging the dog.

I must confess a strong prejudice - I can't stand the sound of compression driven horns. Well, at least if Advantgarde loudspeakers are anything to go by; even at low levels, driven by SETs, they sounded horrid. Later, when I found out how compression drivers worked I was mystified how anyone could take them seriously:

A sealed felt-lined back chamber that is supposed to absorb the back wave??

A metal dome diaphragm... ugh!

An area of high pressure coupled to radial slots or holes- coupled to a trumpet ???

I know that I've much to learn, in particular: prejudice is not a valid ground for aesthetic judgments. But ... ?

When the compression horn is up 'n' running, I'd be very interested in Mrs Olsons judgment. Who knows, perhaps she'll be your Ariadne ?



Cilla
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Old 25th June 2008, 02:17 PM   #4089
SunRa is offline SunRa  Romania
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Hello Mr Olson,

I'd like to point out something that looks to be a great 12" midrange driver. Look at the frequency graph!

12" midrange

I guess this 21 " neo driver would suit well bellow:

By the way how would you interpret the impedance curve of the 12 incher?

Thank you!
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Old 25th June 2008, 02:24 PM   #4090
SunRa is offline SunRa  Romania
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Some other aspect to be mentioned. The driver has a 2.5" voice coil. Probably if the cone would have been lighter, about 25-30 grams, instead of 50, it would have hit 103dB. Probably at the price of a not so well controlled breakup. It has a Bl of 22 T/m, that's something...

Maybe the motor of the Precision Devices driver, the cone of the 12NDA520 and AIC could make up THE MIDRANGE driver? Well.. you can't have everything...

The 21 also looks very well behaved.
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