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Old 19th February 2004, 11:08 PM   #1
Kjetil is offline Kjetil  Norway
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Question 7" Acutton ceramic drivers

Hi folks.

I am planning to design new floorstanding speakers for my home, a 3-way system, using *only* Accuton ceramic drivers. In the tweeter and midrange section there is no doubt in my mind, I will use the 1" C12-6 tweeter, crossed with the C79-6 midrange at somewhere around 4000Hz.

The C79-6 will work from 300Hz up to 4000Hz without problems, and that leaves me with the frequency range from ca. 30Hz to 300Hz wich is to be covered by the bass drivers.

I favor the use of two 7" bass drivers, but I do not know wich ones to choose. My initial thoughts is to use two C94-8 joined in a vented enclosure about 40-45 litre, but there might be better ways?

The reason i am thinking about the C94-8 is the fact that it has much lower distortion on the lowest bands than its "brothers" C92-6, C95-T6, and C92-2x6. However, it has a recommended range from 35Hz, wich is beaten by all of the other three, rated 30Hz, 32Hz, and 30Hz.

I am looking for suggestive input from other people with experience on the Acutton/Thiel ceramics... So the question is: How do I make the most out of two 7" Acutton drivers in the 30Hz-300Hz range??


Thanx in advance,
Kjetil



Driver details:
http://www.accuton.com/e/data/produc...c_drivers.html
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Old 9th March 2004, 03:57 PM   #2
Elias05 is offline Elias05  Netherlands
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Dear Kjetl,

It is not very logical to use the c2 94 for this purpose. It has a too strong drive system to be used for low frequencies.

The reason why the c2 94 shows less distortion at lower frequencies is because it has less excursion under the same measurement conditions. The strong drive is responsible for this. In reality, the cone of the 94 is identical to the 92 and 95.

So the best way to use the Accuton 7" drivers is:

C2 94 can be best used as a (low)midrange
c2 95 can be best used as a bass-mid for relative small enclosures 15 - 18 litre
c2 92 can be best used as a bass-mid for relative large enclosures between 20 and 30 litre

My advise in your case is to use the c2 92. You will get a -3dB of about 40 Hz in 45 litre.
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Old 9th March 2004, 06:46 PM   #3
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Default NEW ACCUTON DRIVERS

It is not on their webpage(www.accuton.com) yet, but here is some UNVERIFIED data I found on the web describing Accuton's new high efficiency drivers:

ACCUTON - C90-T6 - preserial data
- new 173 mm vented basket
- very high efficiency 93 dB
- 55 mm large Titanium voice coil former
- 14 mm underhung Neodymium magnet system
- extremely low distortion
- penetrated membrane for resonance damping
Rdc 6,50 Ohm. SD 145,00 cm
Qm 6,54. Qe 0,32
Qts 0,30. Fs 73 Hz
Vas 8,8 l. No 1,05%
Mms 15,75 g. Rms 1,21
Cms 0,30. BL 11,7
SPL 92,3 dB 1 Watt. SPL 93,15 dB 2,83 V

looking at the graph,(at 1 watt) the frequency is 90db at +/- 110hz, and at 7.5 khz.
92.3 db between 120hz and 7.0 khz. 90hz is at 85 db
Distortion is very very low. K2 and K3 <0.3% between 200hz and 4,5khz at 5 (!) watts, and 0,8% at 100hz. There is a high K2 distortion blip between 5khz and 7khz with a peak of 2,5% at 5 watts. The K3 stays under 0.5%
So it seems they are SET ready.

There is also a hi eff tweeter starting at 2khz and > 25khz :
ACCUTON - C13-6 - preliminary data

- 25 mm ceramic cone like C12-6
- frontplate fully compatible with C12
- high efficiency 92 dB / 2.83 Volt
- high energy distribution
- new 4 mm underhung Neodymium magnet system
- extremely low distortion even at high volume
- also 4 Ohm type available
- significantly reduced ferrofluid filling
and another tweeter

ACCUTON - C24-6 - preliminary data

- 30 mm ceramic cone like C23-6
- frontplate fully compatible with both - C12 or C23
- high efficiency 92 dB / 2.83 Volt
- high energy distribution
- new 6 mm underhung Neodymium magnet system
- extremely low distortion even at high volume
- also 4 Ohm type available
- significantly reduced ferrofluid filling
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Old 9th March 2004, 06:48 PM   #4
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Or:

http://www.clofis.nl/nl/thiel/C90-T6_voorlopig.pdf
http://www.clofis.nl/nl/thiel/C24-6_voorlopig.pdf
http://www.clofis.nl/nl/thiel/C13-6_voorlopig.pdf
__________________
Is that all there is?
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Old 10th March 2004, 08:19 PM   #5
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The T/S calculations are misleading because you can greatly improve the bass performance of the C94 by using an oversized box. By increasing the box size from 6.7L tuned to 51Hz (which is a very small box anyway) to 15L tuned to ~34-40Hz you can increase the bass response by over 7dB @ 40Hz. This tuning comes at the small cost of a few dB's drop in the midbass at around 80Hz to 120Hz.

With my previous pair of speakers I used the C94 (in a sealed configuration though), and I chose it because because it had a far superior step response compared to the C92 and C95. The high inductance of about 0.7mH can be problematic though if using a passive crossover and crossing over directly to a tweeter.

With a port the powerhandling would be around 17W @ 13Vrms before the cone excursion exceeds +-4mm below 32Hz. This isn't too bad I think, for a 7" speaker. Due to the resonant loading of a vented enclosure the excursion is smaller below about 60Hz compared with the huge infinite baffle in which the measurements are taken. This means that distortion would actually be significantly lower than the measurements indicate below 60Hz, but very similar above 60Hz.

The 300Hz crossover frequency means that there shouldn't be too many problems with high-frequency sounds escaping through the port, as is usually the case with 2-way vented enclosures.

The cone may well be identical to the C92 and C95, but the the voice coil sure isn't. The height of the coil influences the ultimate levels of distortion, as does the VAS. A low VAS means that the suspension is very hard and may introduce its own nonlinearities. A dedicated subwoofer is another solution as you already know.

CM
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Old 25th March 2004, 08:01 PM   #6
Kjetil is offline Kjetil  Norway
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Thanks for the replies folks.

I find especially the new C82 interresting.. Actually, it made me change my mind completely about this project. I've done some thinking, CAD'ing, etc. and revised my entire project, and the C82 is now the only Accuton driver left in my project. I'll explain why;

The C82 appears to go much deeper than my expectations. It will have no problems to take care of the bass dow to say 70-80Hz (actually it will reach 45Hz at -3dB in 11,6 liter), and thus the woofer will not have to be positioned in the front baffle. I can use down firing or side firing woofer to keep the front baffle slim and nice looking. While the accutons are great, they do not have particular deep response, and there is really no need for a ceramic membran pushing air from 80Hz and down, IMO it would be a waste of money, and not the right choice for my needs. The Ceramic membran of the C82 will take care of all voices etc. anywayz..

Due to the fact that I am not verry found of living with large boxes, I am concidering the somewhat inefficient Seas L22RN4X/P aluminium woofer, wich will suit a down-firing configuration and will give -3dB @ 31,5Hz in a 33,5 liter box, at an SPL of 86dB/w/m. I could use an active LR crossover to separate the woofer from the other drivers, and driving it with a digital power amp and some extra gain to avoid having to damp the other drivers, or I could do it the "easy way" and L-pad the other drivers with all passive crossovers and invest some extra money in a larger quality amp.. I am not sure yet, but if I'm to spend money on bass, I want bass...

Also; I'm not sure if this is such a wise thing, but I concider strongly to use the Hiquphon OW I tweeter, as I (don't beat me) tend to enjoy the smoothness of silk domes and prefer them over the more "sparkling" ones. I have not heard the C12 or C13, but the C24 sounded a bit.. what can I say... sparkling? Well, I think it's a matter of taste.. But the OW I has undoubtly a smooth response, X-traordinary dispersion, and the SPL is just right for this project.

To make a short summar, the preliminary setup I am concidering at this point is:
Hiquphon OW I (XO @ ca. 3.5KHz)
Accuton C82 Midbass (XO @ ca. 3.5KHz, 70-90Hz)
...and the Seas L22RN4X woofer in a down or side firing configuration...

My knowledge of the C82 are still somewhat limited, and I wish to extend it, so I would be grateful for any new info on this driver. Also, any comments and thoughts on the setup would be appreciated, including the issue of whether to side or down fire the woofer.

So much for an "all-accuton" system......
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Old 25th March 2004, 11:25 PM   #7
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Default Celestion System 6000 loudspeaker system

Kjetil,

Dipole and cardoid bass is becomming more popular as a way to minimize room interaction. With enough amplifier boost, the baffles can be reasonable in size even for 15" woofers.

Remember
Celestion System 6000 loudspeaker system

http://www.stereophile.com/loudspeakerreviews/892/

or Gradient speakers?

================================
A monopole is a zero order gradient.

Dipoles and cardioids are first order gradients.
A Dipole is two monopoles separated by a distance and operated out of phase.

A cardioid is two monopoles separated by a distance and operating out of phase, with one monopole delayed by an amount equivalent to the physical separation between the two monopoles. e.g. if the monopoles are 1 meter apart, the monopole aimed in the direction of reduced dispersion is delayed by 1/343th of a second.

A unidirectional second order gradient is constructed with two dipoles separated by a distance and operating out of phase with one dipole delayed by an amount equivalent to the physical separation between the two dipoles.

Dipoles and cardioids have directionality indices of 4.8db. The better directional control comes from 6db per octave of directed phase cancellation, requiring 6db per octave higher power input for a flat response.

Second order unidirectional gradients have a directionality index of 8.8dB. The even better directional control comes from 12db per octave of directed phase cancellation, requiring 12db per octave higher power input for a flat response.
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