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Old 16th October 2010, 12:25 PM   #111
DQ828 is offline DQ828  Australia
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Very nice, you've been a very busy boy, looks like lots of fun
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Old 16th October 2010, 12:38 PM   #112
Helmuth is offline Helmuth  Netherlands
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Very nice, you've been a very busy boy, looks like lots of fun
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Old 16th October 2010, 07:24 PM   #113
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I dont want to get involved in an active design at this early stage of speaker building hobbie.
Your choice, but my experience is sticking to passive makes things harder, not easier. Particularly in OB.

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High Qts drivers are popular for open baffle applications because the bump in response at FS helps to counter the open baffle rolloff and extends the low frequency response.
Takes a wide baffle to lower the dipole peak to the vicinity of most drivers' Fs. At least for me the sacrifice in directivity's not worth the avoidance of equalization.
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Old 16th October 2010, 08:06 PM   #114
jwmbro is offline jwmbro  United States
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I dont want to get involved in an active design at this early stage of speaker building hobbie. Also I aleady have the amp etc.
This may sound a bit odd, and it's taken me several years to realize this, but... in my opinion active design is a lot easier than passive design. Disadvantage being financially the fact that you need more amps, but a few low power amps for the highs are not too expensive.
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Old 16th October 2010, 09:02 PM   #115
6.283 is offline 6.283  Germany
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passive makes things harder, not easier. Particularly in OB.
exactly !

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This may sound a bit odd
not at all odd.

In the age of DSP, passive OB is pointless.
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Old 16th October 2010, 10:29 PM   #116
ScottG is offline ScottG  United States
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..but are also a long way from my goals, being, a hi efficiency, passive design, the tweeter is about 96dB & the mid is somewhere closer to 100dB, or so I have read.

I dont want to get involved in an active design at this early stage of speaker building hobbie. Also I aleady have the amp etc.

If you know of any hi efficieny, 12" drives with a Qts of about 0.7 & a xmax of 6+ let me know, all suggestions are welcome.


..well, that rather depends on the *priority* of your goals.

IF your priority is for truly low freq. response in a basic 12"x24" package for the bass drivers operating as dipoles - then this will do it. As far as it being active.. well that's only for the bass drivers, where it make the most sense (for a variety of factors). The rest of the design can be passive.

These are powered sub-woofers with relatively low mass for their fs and excursion.. plus the servo design will help the integration (both in cancellation loss and basic sound character). Their efficiency is largely irrelevant, BUT at 1 meter wired in parallel to the amplifier they are about 93 db "average". (..thought the "average" is meaningless for a nearly non-existent baffle.)

And yes, I know of plenty of "high" efficiency 12" drivers with a Qts of .7 or higher.. the trouble is - they have nearly no xmax and have high fs.

Basic driver design limitations will necessarily *exclude* an efficient driver with a high Qts, a low fs, and high excursion.

These drivers are about as close as you'll get (and remember that their dual voice coils are wire in parallel for an extra 3db, i.e. basically they are 87db drivers with an extra VC that when paralleled result in 90db):

http://www.aespeakers.com/drivers.php?driver_id=28

In a 2 driver config. you could parallel one coil with one driver, and the other coil with the other driver's coil. Power one of the paralleled coils in your passive design and the other paralleled coils actively. If you wired them all in parallel (all 4 VC's) you'd be looking at an average load of 2 ohms.. which is a bit much for most amplifiers (..though it would result in an average of about 96 db).
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Old 17th October 2010, 02:30 AM   #117
DQ828 is offline DQ828  Australia
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AE Speakers --- Superb Quality, Unforgettable Performance, Definitely.

In a 2 driver config. you could parallel one coil with one driver, and the other coil with the other driver's coil. Power one of the paralleled coils in your passive design and the other paralleled coils actively. If you wired them all in parallel (all 4 VC's) you'd be looking at an average load of 2 ohms.. which is a bit much for most amplifiers (..though it would result in an average of about 96 db).
I have looked at those drivers & they look very interesting, but they would really stress the budget, beyond breaking point I expect.

Your getting a bit complicated for this simple mind, there is more than one reason I like the KISS principal.
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Old 17th October 2010, 02:54 AM   #118
DQ828 is offline DQ828  Australia
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exactly !

not at all odd.

In the age of DSP, passive OB is pointless.
What setup would you recommend?

I assume I would need six amps?

Some sort of controller/equalizer thingy

Is that it?
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Old 17th October 2010, 03:21 AM   #119
jwmbro is offline jwmbro  United States
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What setup would you recommend?

I assume I would need six amps?

Some sort of controller/equalizer thingy

Is that it?
Yep, you'll need at least 6 channels of amplification, also an x-over / DSP unit, such as the Behringer DCX2496 or the MiniDSP 2x4. Or more correctly you'll need however many of these as is necessary to supply the necessary channels. ie for a stereo 3-way you need one Behringer, but two MiniDSPs. (if you wanted a stereo 2-way, you'd need one of either, for a stereo 4-way you'd need two of either). There are other options as well, such as crossing over in software via PC, using an external multi-channel sound interface.

There's not really a lot else you need, any other peripherals would be the same as in a passive system, depending on your wants.

I personally am going to build a 2-way open baffle system using a MiniDSP board and an amp I already have. Only thing left to do is buy a second stereo amp for the woofer channel. On the upside: no impedance measuremnts to do, no coils and caps to buy, (almost) no soldering, and as an added bonus I can do digital room correction, dipole roll-off equalisation, linkwitz transform, etc. With that amount of correction available, most TS-Parameters become "obsolete", pretty near all you need is Sd and Xmax for bass.
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Old 17th October 2010, 03:38 AM   #120
ScottG is offline ScottG  United States
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I have looked at those drivers & they look very interesting, but they would really stress the budget, beyond breaking point I expect.

Your getting a bit complicated for this simple mind, there is more than one reason I like the KISS principal.
wait a minute.. you never mentioned budget before..

The AE drivers shouldn't be more expensive than the BMS drivers you were looking at. (..which btw, others have reported as being considerably less efficient than stated on their website.)

If you want something simple.. well, you are looking at the wrong design. A good dipole design isn't going to be truly simple, and a passive implementation will significantly increase complexity.

Suggestion: Do what I did for one of my designs.. just get some midbass drivers that are suitable with a bit of resistance from a large cored inductor (in series with the two paralleled drivers), and don't worry about lower freq.s.. Here are some:

Dayton PA255-8 10" Pro Woofer | Parts-Express.com
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