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-   -   First project - office speakers (http://www.diyaudio.com/forums/multi-way/18246-first-project-office-speakers.html)

Dave Jones 27th July 2003 03:27 AM

First project - office speakers
 
I recently finished re-building a set of Lynn Olson's Ariel Mark II loudspeakers and crossovers. They are phenomenal. I want to thank everyone here who helped.

I fear the $150 I paid for the speakers was false economy. They were much better than my CD player and amp, so of course I had to replace those (cost: $1000 US, plus tax.) Worse yet, now I have the bug. I want to build a set of speakers for my office. Uh oh. Wanna help?

The office is about 14X14 feet with 10" ceilings. Three sides are all drywall. One side, which will face the speakers, has a large window with Venetian blinds. I want floor standing speakers with the tweeters near my seated ear level, which looks to be about 45 inches. The speakers will have to be placed fairly close to the wall. In order that the speakers not look out of place, they should not be very large - certainly smaller than the Ariels. Because I am so pleased with the Ariels, I would like to use a transmission line, or maybe a quarter wave pipe. A single full range driver appeals to me. Because of the size of the room, I don't want high efficiency or the capacity to play loud. (With the Ariels in the room, I can't turn the 40 watt amp past 9 o'clock.) However, I want the bass to go low. (Who doesn't?) Room lift should work for me there.

Summarizing...

1) Floor standing
2) Rather tall (high tweeter)
3) The smaller the better
4) transmission line or tube prefered
5) low efficiency
6) single driver?

Oh. One more thing. I don't know what I'm doing. As a cabinet maker, acoustic engineer, or a passive filter designer, I would make an excellent fry cook. But then, ignorance has never daunted me in the past.

What say you all?

Timn8ter 27th July 2003 04:06 AM

I've been eyeing the Jordan JX92S drivers. See them at EJJordan . The web site includes plans for a TL design using a single driver. While the cabinet may not be the easiest to build, the fact that a simple passive filter is optional may compensate. Looks promising.

Dave Jones 27th July 2003 05:28 AM

Quote:

Originally posted by Timn8ter
I've been eyeing the Jordan JX92S drivers. See them at EJJordan . The web site includes plans for a TL design using a single driver. While the cabinet may not be the easiest to build, the fact that a simple passive filter is optional may compensate. Looks promising.
WOW! That looks like the one.

http://www.ejjordan.co.uk/JX92.html

How did you find that? Fs of 45Hz, and you can put it in a box 4" deep. Woo.

I wonder about that box that can be either sealed, vented, or TL. How carefully could it be tuned for the TL configuration? Plus, it could be taller. But the driver looks like it may be the one.

Dave

phreeky82 27th July 2003 06:44 AM

low efficiency should most certainly not be a 'requirement' tho. just don't turn the volume up much.

unless you have a very 'noisy' amp or something - lots of background hiss, that doesn't seem to increase with volume.

Dave Jones 27th July 2003 06:57 AM

I've got an idea about making it taller.

The trick is to make it taller without lengthening the transmission line too much. So I had this idea: Add a skirt at the bottom. The transmission line would remain just as it is, but would open into a new wide, enclosed area at the bottom of the cabinet. Now then, put another board inside the skirt, running from the inside edge of the port to the bottom, turning bottom area into a horn pointed at the floor. The triangular void area could be used to house a baffle step filter or whatever.

Is that workable? Would it effectively lengthen the line too much? If so, I could leave off the "horn board", and even cut out the sides of the skirt if necessary. But I like the horn idea.

Dave Jones 27th July 2003 07:03 AM

Quote:

Originally posted by phreeky82
low efficiency should most certainly not be a 'requirement' tho. just don't turn the volume up much.

unless you have a very 'noisy' amp or something - lots of background hiss, that doesn't seem to increase with volume.

The amp is a very good one, by my standards anyway -- Rotel RA-02. It's rated at 40 W per channel. There's a slight problem with the Ariels in that it's a little difficult to adjust the volume, because I have to turn the knob such a small amount. If I just tap the volume button on the remote, it can move too far. I think I want to move the Ariels into my living room. Anyone in the market for a Polk home theater system?

phreeky82 27th July 2003 07:07 AM

i don't really know amp models and all............but is it a pure amp (ie. does all input come from externally)?

if so, just put a dual gang log pot at line level just before it goes into the amp. u could also use other methods of attenuating.

Dave Jones 27th July 2003 07:22 AM

Quote:

Originally posted by phreeky82
i don't really know amp models and all............but is it a pure amp (ie. does all input come from externally)?

if so, just put a dual gang log pot at line level just before it goes into the amp. u could also use other methods of attenuating.

It's an integrated preamp/amp. (It has a preamp out, but I'm not using it.)

Please forgive my ignurnce, but what is a dual gang log pot?

phreeky82 27th July 2003 07:30 AM

a pot is just a variable resistor. typically a pot is linear (resistance varies linearly with the position), but audio increases volume logorithmically. so they make log pots.

and a dual log pot just has a single control (a 'post' that can be turned) controlling two of these in one - for stereo.

Dave Jones 27th July 2003 07:39 AM

Quote:

Originally posted by phreeky82
a pot is just a variable resistor. typically a pot is linear (resistance varies linearly with the position), but audio increases volume logorithmically. so they make log pots.

and a dual log pot just has a single control (a 'post' that can be turned) controlling two of these in one - for stereo.

Duh. I knew that. A log (for logrithmic) pot is also called an "audio pot".


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