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Old 15th December 2007, 08:25 AM   #2851
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Quote:
Originally posted by Andy Graddon
Lynn, please say you have come to some sort of conclusion on "what's next".

Its been one mighty long thread, and I would really like to see what comes of all the discussion.
Executive Summary:

Physical condition still precludes building - getting up and down from the floor is still a hassle, and carrying things downstairs is still a somewhat nervous and awkward business requiring a cane and a nearby railing. Upstairs is much easier. Will focus on physical training in the months to come - mobility still isn't 100% there yet. Snow and ice certainly make for extremely careful ventures outdoors - canes are a little weird on bad surfaces.

Actual construction start seems probable in the Jan, Feb, March timeframe. RAAL tweeters already in hand, MLSSA works fine, SoundEasy yet to be bought. New PC will host SoundEasy, and old PC will host MLSSA. ACO Pacific 1/2" calibrated condenser mike on low-diffraction stand will perform measurements.

System will be 3-way, active crossover in the 400~640 Hz range, and implemented with a prosound crossover/parametric EQ unit. Initial setup will use old transistor amp for the bass, and the Karna amplifier for mid and HF. Mid/HF crossover passive in the 3~5 kHz range.

Bass Module: 3 or 4 15-inch drivers, two or three Eminence Delta-15LFA's, and one Great Plains Audio 416 or 515, Alnico preferred.

Mid: Three choices mentioned previously. Will measure and listen to all three, no idea at present which will be the favorite. I do not expect them to sound the same at all.

HF: Double-high RAAL in hand. Magnetar's choice of HF compression driver and horn combo sound like a good, simple starting point for comparison.

If you're expecting a kit, uh, well, it ain't gonna be like that. What will appear will be progress reports, with a number of U-turns and revisions going on for several months. My usual rate of progress on a new speaker or amplifier is 6 to 18 months, which is pretty much the high-end industry average.
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Old 15th December 2007, 08:38 AM   #2852
Andy G is offline Andy G  Australia
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The Ariel was buildable by anyone with moderate carpentry skills.

This looks like it will be a major PITA for the average DIY guy !! More a personal thing , which I think is good, btw !

3-4 x15" drivers . ouch, my wallet hurts !!

It really does sound like some sort of PA speaker that you are aiming at, which is, I suppose, the outcome expected from the thread.

Hope you get to speaker building capability soon .... !! Its is a necessary part of life after all !
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Old 15th December 2007, 08:42 AM   #2853
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This is the speaker equivalent of the Amity and Karna, projects for the most advanced (and adventurous) builders only. There are no commercial equivalents of the Amity and Karna, and I don't expect any commercial equivalents of this speaker. I design products that fill empty niches in the audio-ecosphere.

It doesn't fall into a standard marketing demographic, and the Big Two magazines are not going to promote it. (You want promotion, demographics, and ultra-high WAF, build a Magico Mini.) The real money is in building speakers that are trivial variants of existing styles and market categories, with a strong emphasis on HT and decorator-friendly systems. What's a little amusing about the Ariel it was one of the very first tall and narrow MTM systems - now the format is so common it's become a cliche.

It would be nice to license this new system to a manufacturer, but that's for the future.
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Old 15th December 2007, 10:00 AM   #2854
el`Ol is offline el`Ol  Germany
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Lynn,

are you going to determine the ideal mid/high x-over point subjectively with an active x-over?
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Old 15th December 2007, 12:02 PM   #2855
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Quote:
Originally posted by Cappy
Regarding:

<<I think you'll have a hard side deciding between the raw immediacy of the phenolic compression driver compared to the wonderful tone and deep color saturation of a big motor low mass cone. -- I'm to the point where I crave both ->>

Why choose? Use a cone for 8 months and a compression driver for 4 months, or visa versa...

The concept of a wife AND a mistress has been around for thousands of years for a reason!
LOL - my thoughts exactly!


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Old 15th December 2007, 12:54 PM   #2856
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Quote:
Originally posted by Lynn Olson

There were several systems like this at the RMAF. They sounded thin, compressed, and had very poor dynamics. Spacious, yes, of course. But the dynamics were no better than electrostats, but without the see-through transparency, either. I can't see any way horn dynamics can be mimicked by small drivers with lots of EQ and amplifier power.

Lynn, I understand your position and objectives. However, I think you are missing my point. On several occasions you have indicated that the way you will approach the dipole roll off at low frequency is to add area. I agree that this will reduce the required excursion but it is unlikely a simple solution to the dipole roll off. Eq for the dipole roll off isn't a function of driver size. It's a function of baffle size/shape.

If I can express this in another way, it seems to me that you are thinking about dealing with the dipole roll off in a manner similar to dealing with the baffle step in a conventional box speaker by designing it as a 2 1/2 way system. That works because the additional 1/2 way driver(s) bring in an additional 6dB which compensated for the 2Pi to 4Pi transition. But with a dipole system we are dealing with a 6dB/octave roll off that continues to DC. Rolling in a second driver just places a zero and a pole in the dipole roll off that puts a kink in the roll off and shifts the dipole asymptote an octave lower (assuming the drivers are all identical)as shown below, where both drivers are assumed to be flat to DC. From left to right the second driver is bought in at higher and higher frequency.

Click the image to open in full size.

The red is one driver and the green is the same driver augmented by a second driver with a 1st order LP filter. This has noting to do with the type of drivers, system sensitivity or dynamics. It is only a function the dipole delay and where the second driver rolls in. This response ultimately needs tp be equalized to achieve flat (or desired) low frequency response.

If you start considering drivers with different T/S parameters, as you suggested some time ago, then as the frequency drops off the output form the lower Q drivers will fall off faster than the high Q drivers and the dipole asymptote will turn down again comming back towards the red trace.

I might also suggest that the thinness you are referring to may well have been due to the lack of, or improper equalization applied in the mid bass region. I don't think you would find my NaO system sounding thin. However, I am sure you would not be satisfied with the dynamics. NaO panels were designed for a max SPL of 110 dB@ 1M given appropriate amplifier power which would seem to fall short of your requirement.
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Old 15th December 2007, 01:56 PM   #2857
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Using the drivers he's been talking (low QTS 12's and 15's) about will surely require massive eq even with the low pass on some of them -

Using much lower cost high QTS mid sensitivity drivers (around 92 db/w) in multiple clusters low to the ground sounds very good and requires little to no eq (provided he has a subwoofer that will keep up below 50-60 cycles!) and will meet the high output criteria. It's really pretty simple - there are others out there that are building systems like this and I look forward to seeing their end results.

I think what's happening is people get caught up on perceived gains by the sensitivity ratings of the bass drivers and MOSTLY the illusion that cost equals quality. In this application it seems cost equals more cost. A 101 db sensitive 360 dollar .25 QTS woofer will be far less sensitive than six 92 db sensitive 60 dollar mid QTS (.6 up) woofers in a bass dipole - the multi driver high QTS system also will have higher output in the bass and require less to no eq and doesn't require the multiple low pass crossovers - I also feel the distortion per dollar will be far less with the 60 dollar woofers due to the lower excursion.

The savings alone in using this type of bass system (less complicated crossovers, amplifiers and driver costs) will free up more cash for a better mid (probably buy the mid horns or more) and will keep the design simple and more accessible to more people -
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Old 15th December 2007, 02:17 PM   #2858
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Quote:
Originally posted by john k...



Lynn, I understand your position and objectives. However, I think you are missing my point. On several occasions you have indicated that the way you will approach the dipole roll off at low frequency is to add area. I agree that this will reduce the required excursion but it is unlikely a simple solution to the dipole roll off. Eq for the dipole roll off isn't a function of driver size. It's a function of baffle size/shape.

If I can express this in another way, it seems to me that you are thinking about dealing with the dipole roll off in a manner similar to dealing with the baffle step in a conventional box speaker by designing it as a 2 1/2 way system. That works because the additional 1/2 way driver(s) bring in an additional 6dB which compensated for the 2Pi to 4Pi transition. But with a dipole system we are dealing with a 6dB/octave roll off that continues to DC. Rolling in a second driver just places a zero and a pole in the dipole roll off that puts a kink in the roll off and shifts the dipole asymptote an octave lower (assuming the drivers are all identical)as shown below, where both drivers are assumed to be flat to DC. From left to right the second driver is bought in at higher and higher frequency.

Click the image to open in full size.

The red is one driver and the green is the same driver augmented by a second driver with a 1st order LP filter. This has noting to do with the type of drivers, system sensitivity or dynamics. It is only a function the dipole delay and where the second driver rolls in. This response ultimately needs tp be equalized to achieve flat (or desired) low frequency response.

If you start considering drivers with different T/S parameters, as you suggested some time ago, then as the frequency drops off the output form the lower Q drivers will fall off faster than the high Q drivers and the dipole asymptote will turn down again comming back towards the red trace.

I might also suggest that the thinness you are referring to may well have been due to the lack of, or improper equalization applied in the mid bass region. I don't think you would find my NaO system sounding thin. However, I am sure you would not be satisfied with the dynamics. NaO panels were designed for a max SPL of 110 dB@ 1M given appropriate amplifier power which would seem to fall short of your requirement.

Now add in the insertion loss from the choke on the low pass and the fact the bass drivers are no longer in phase.........
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Old 15th December 2007, 03:44 PM   #2859
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Hi Mag,

The insertion loss isnít there but the phase shift is. I figure the insertion loss can be limited to a fraction of a dB, so no big deal.

The real bottom line is that once the baffle shape/size and driver compliment is set the system sensitivity at the low frequency cut off is fixed. What remains is to equalize the response to be flat (or match the target) above the system cut off in the dipole region and beyond. If you start with 4 identical drivers with 96dB/W 2Pi sensitivity then with a series/parallel configuration you end up with 102dB/W 2Pi sensitivity. Dipole would drop to the 4Pi sensitivity but near floor operation would restore 2Pi (102). Dipole roll off of 6dB an octave below the dipole = monopole point would drop that back to 96dB/W. Now assume four 12" drivers on a 1M x 1M baffle with a max excursion limitation of 5 mm. The dipole = monopole point will be at about 100 Hz so at 50 Hz the system sensitivity is pegged at 96dB/W. Max SPL with 5 mm is about 110dB requiring 25 watts. To get 120 dB would require an excursion of 15 mm+ and a power of 251 W. Pushing the cut off up to 72 Hz would limit the excursion to 5 mm and reduce the required power (about 3 dB) to 125w.

I'm assuming 500 cm^2 per driver here. So a total of 2000 cm^2 area. We can look for more sensitive drivers which would reduce the required power but the excursion requirements won't change. Four 15" drivers would reduce the excursion (at 50 Hz) to about 9 mm. I'm having a hard time finding prosound drivers which have these kinds of Xmax.

Now if you start mixing high Qts and low Qts drivers we also have to consider that the drivers won't be working together at low frequency. For example considering drivers with the same Fs but one pair with Qts = 0.33 and the other with Qts = 1 the low Qts driver would produce almost 10dB less output at fs, assuming the same midband sensitivity. So mixing Qts driver means we would basically have just the two high Qts drivers producing the low frequency output near Fs. so there goes another 6dB.


Going back to the sensitivity issue, if you want to target the system nominal sensitivity at sensitivity of the midbad drivers, around 102 dB, then you have to provide the low frequency eq at the line level. but the low frequency sensitivity will still be at 96dB. Placing the eq at the line level (passive or active) will maximize the potential of the amplifiers. If you use passive eq at the speaker side then the sensitivity is fixed at 96 dB and all the added midband driver sensitivity goes up in heat in the crossover and reduces the amplifiers potential to drive the system.


I guess the way I see it is that if the target is 120dB with a 25 watt SET amp or what ever the system sensitivity needs to be 106dB/W. That seems to be a pretty daunting task with any kind of dipole system with acceptable low frequency response (50 to 75 Hz cut off) assuming a conventional subwoofer is also present.
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Old 15th December 2007, 07:06 PM   #2860
mige0 is offline mige0  Austria
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Hi

For an "easy to play around a little" with Xmax and SPL max and Sd required :

http://www.linkwitzlab.com/spl_max1.xls


Maybe also worth to have a look at to see how simple things can work also :

Fast, fun, Inexpensive OB project




----------------------------


JohnK, couldn't you show us a simulation where you double Sd each octave downwards - lets say three times in an optimised way what would make 1 + 1 + 2 = 4 identical drivers in total ?
Or even four times doubling 1 + 1 + 2 + 4 = 8 identical drivers in total ?


Lets say the baffle peak is at 500 Hz let them come in at 300 Hz / 150 Hz / 75 Hz or so...



Greetings
Michael

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