[rmihai0]

Hi Dave,

and a Hapy New Year!

Question for you - what is, very exact, the lowest sensitivity of 1801b?

On your web-site is a bit confusing. Once you say "Sensitivity is between 84 and 85db." Other time you say "The 83db/watt sensitivity rating is a realistic average of the response curve". "My speakers are about 85db/watt". In driver measuring picture I can see 85.83 and 86.53...

And in top of that the drivers are rated @ 87db and 86.5db...

Please let me know, because I am in the process of designing my own power amplifier and I need to know for sure.

Thank you

[David Ellis]

Fair Question,

The senstivity follows your initial comment... 84-85db/2.83 volts.  It has an 8 ohm nominal sensitivity and a low dcr of 6 ohms.  HOWEVER, you should realize the commercial marketing departments commonly embelish their sensitivty ratings.

If you are plannining to build and amplifier, the fairly common @ 60wpc AKSA or ESP amps can use higher voltage rails with the 1801, and push another @ 40 watts.  Their "normal" design optimally accomodates 4 ohm speakers, but is not optimal for 8 ohm speakers.  Yes, SS amplifiers are built to accomodate loudspeaker impedance too.

As mentioned in my recommended amplifier string, I encourage @60wpc SS or @ 35wpc tubes.  The latter is commonly an EL34 push/pull tube amp.

Dave

[David Ellis]

And in top of that the drivers are rated @ 87db and 86.5db...

Some sensitivty is lost in the series inductor behind the woofer.

And... my sensitivty rating is slightly conservative.  

Dave

[David Ellis]

The 83db/watt sensitivity rating is a realistic average of the response curve.

Yikes, this is a typo my page! Thanks for noticing this.  I'll get it fixed when I return home.

[rmihai0]

Thank you Dave.

[Watson]

The senstivity follows your initial comment... 84-85db/2.83 volts.

Are you sure the sensitivity is that high?  The woofer is rated at 86.5dB, and you probably have 3dB of baffle step compensation (at least).  I don't see how the sensitivity could be more than 83.5dB.

The page on your site that says "the 83db/watt sensitivity rating is a realistic average of the response curve" sounds more realistic to me.

[David Ellis]

Are you sure the sensitivity is that high? The woofer is rated at 86.5dB, and you probably have 3dB of baffle step compensation (at least). I don't see how the sensitivity could be more than 83.5dB.

Good question.

Yes, I am sure.

It seems you understand a few concepts, but... well... I'll ask some pointed questions to clear the matter.

What is the 86.5 db sensitivity derived from and where (in the frequency response range) is this manifested?  Is this manifested in the bass range?

Where does baffle step come from?  Does it ADD or SUBTRACT from the output of the driver?

[Watson]

Yes, I am sure.

It seems you understand a few concepts, but... well... I'll ask some pointed questions to clear the matter.

What is the 86.5 db sensitivity derived from and where (in the frequency response range) is this manifested? Is this manifested in the bass range?

Where does baffle step come from? Does it ADD or SUBTRACT from the output of the driver?

If you're sure, why not explain your reasoning?  Why the questions?  Looking at the W18E001 datasheet, the driver's sensitivity at 200Hz is about 82.5dB.  That will be your baseline sensitivity after baffle step compensation.

I suspect your original thinking, when you wrote this page:
http://www.ellisaudio.com/dbsubject.htm
is accurate, not a typo.

[rmihai0]

Watson - I have the feeling that you are right. In this case (82.5db) still the AKSA 55 N+ will do a perfect job at my listening position (6 ft) and listenign levels (average 65-68db).

If my calculations are right, in my room I need exactly 55W.

But, if I would move into a larger room, then it looks to me that I will need no more no less then exactly 177W!!!

[David Ellis]

If you're sure, why not explain your reasoning? Why the questions?

Because the last time someone asked me a question of this nature, I spent about 4-5 hours at the keyboard across about 3 pages of online message strings concerning an active crossover debate... only to learn the gentlemen posing the initial question had some positive experience with 70s era drivers and active crossovers versus passive crossovers.  In retrospect, I blame myself for engaging in this very long exchange before isolating the variables initially.  Following this, I decided that any very potentially long session at the keyboard would be preceeded by a complete understanding of the questions, and the person's knowledge basis for asking these questions.

Your initial question is quite simple, but has the potential to "blossom"   .  I wish to avoid this if possible  

Are you uncertain of these issues?

Dave