Is a single 3886 powerful enough to drive SS 18w-4531 ? - diyAudio
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Old 10th October 2007, 07:04 AM   #1
100db is offline 100db  Thailand
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Default Is a single 3886 powerful enough to drive SS 18w-4531 ?

Hi All,

I've used a single chip LM-4780 with +/- 24v supply as 2 channel power amp to drive my 95db/4 Ohm speakers for a couple months and I'm very pleased with the result. same for Seas CB17RCY/P -- 91db/8 ohm.

But now I'm thinking to change the drivers to Scanspeak 18w-4531 which is 90db/4 ohm ... I don't know if my gainclone still able to handle this driver properly ?

I've a bad experience with my GC when try to drive 15w-8530 -- 85.5db/8Ohm. Result was much better when I drive the 8530 with a larger amp, image & sound stage including detail is much better. So, I'm a little bit worry about changing to the SS drivers.

Anybody experienced hooking a pair of LM 3886 or a single 4780 to SS 18w-4531 before ?

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Old 10th October 2007, 09:08 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
a drop from 95db/2.8V/m to 90db/2.8V/m requires three times as much power from the chipamp.
Changing to the lower sensitivity speaker will make a significant difference to dynamic overhead (it will clip more often) and to operating temperatures (it will run hotter, making it clip even more often).
I reckon the performance of the amp/speaker combination will deteriorate.
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Old 10th October 2007, 11:16 AM   #3
100db is offline 100db  Thailand
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Hi Andrew

Thanks for your reply, I didn't feel much different when I change from a car speakers - 95db to Seas CB17 which is only 91db. on both amp's temperature and sound quality ... actually sound quality is better on the Seas, image & staging still fine, just only feel less bass produced -- maybe because of CB17 drivers it self ?

I'm suspect if 95db car speakers was over rated or not.

Any idea about comparing Seas CB17-91db / 8 Ohm with SS 18w-4531 90db/ 4 Ohm ?

I don't know if there are any other factors that can cause the different on "how hard to drive" from 2 different drivers with same or similar rated sensitivity ?

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Old 10th October 2007, 11:54 AM   #4
AndrewT is offline AndrewT  Scotland
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hi,
but the SEAS is 91db/2.83/m and 8ohm, not 4ohm.
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Old 10th October 2007, 01:57 PM   #5
100db is offline 100db  Thailand
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Sorry, but I really don't know this.

I thought same sensitivity and lower impedance will be easier to drive because wattage from power amp will be doubled when load is only half ?

For example 50 watt @ 8Ohm and 100 watt at 4 Ohm ?

Surely the chip have to work harder but if heat sink is big enough ... is it still degrade sonic quality ?
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Old 10th October 2007, 05:44 PM   #6
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use three chips in parallel with a massive heatsink or use 4 chips to stil l be on the safer side and as well as good output current to drive the speakers that u have...
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Old 11th October 2007, 01:38 AM   #7
100db is offline 100db  Thailand
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Hi rhythmdiy,

The problem is my power supply is not big enough to supply more than 2 chips ( or a single 4780 in stereo mode ), I think I've to select the drivers to match with power of this amp.
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Old 11th October 2007, 04:51 AM   #8
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As always, a design's outcome is based on the precise matching of all components. Like a recipe, the exact combination of ingredients in precisely measured amounts are crucial.

With lower sensitivities, a speaker will require more power to get the same results of a more efficient speaker. More power will require a bigger powersupply and heatsinking considerations.
Do the math!

Your question was... Is a single 3886 powerful enough to drive SS 18w-4531 ?
The simple answer is yes. It will work.

The obvious next question is... how will it work?
The answer is... it depends upon how you configure THE PACKAGE.

Your recipe is based upon vinegar and oil ingredients, but you're expecting a lobster dinner out of salad dressing components. You can't make chocolate cake without chocolate, and pseudo chocolate is not chocolate, no matter what the label reads.

The basics demand different parameters for a successful outcome.

You need more power to match that speaker. More power will require a bigger powersupply, bigger heatsinks and a bigger output stage. This is why higher efficency speakers are rated HIGHER EFFICIENCY.
Unlike car stereos, this spec actually means something!

In the end, it matters more THAT you learn. It matters less HOW you learn.
Now go make some smoke.
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Old 12th October 2007, 09:32 AM   #9
100db is offline 100db  Thailand
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So...
Shall I conclude that the SS18w-4531 is simply not match with this amp ?

I actually want to learn this by try it out my self but the SS is too expensive for just a try and on top of that it's not locally available here. Will go for a higher efficiency one then.

Thanks for all the comments.
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Old 12th October 2007, 09:54 AM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
chipamps perform better with higher impedance loads, as do all amplifiers.
I recommend you look for a 90 to 96db/W/m 8ohm driver that gives sufficient low bass for your purpose. The lower frequency you push the design the less efficient/sensitive the driver due to the inherent parameters that allow reproduction of the lower frequencies.
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