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Old 24th February 2004, 09:37 PM   #1
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Default Jordan monitors - pics and specs

I thought I'd share some pics of my latest project, a pair of Jordan JX92S-based monitors.

Vital statistics as follows:
Dimensions: 40h x 21w x 31d approx (cms)
Internal volume: 15l
Mass: 10kg each
Cost: 200/pair approx

Freq response & more details to follow...

Cheers
IH
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Old 24th February 2004, 09:44 PM   #2
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Here's the frequency response of the unit shown, measured on-axis 10cm from the centre of the driver cone, using a Behringer ECM8000 mic.
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File Type: gif unit 2 final response.gif (12.7 KB, 797 views)
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Old 24th February 2004, 09:49 PM   #3
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...and here's the impedance curve (apologies for chopping off the right-hand end of the picture, vBulletin doesn't like anything >800 pixels). Main resonance is around 75Hz.

Cheers
IH
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Old 24th February 2004, 09:57 PM   #4
Svante is offline Svante  Sweden
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Quote:
Originally posted by IanHarvey
Here's the frequency response of the unit shown, measured on-axis 10cm from the centre of the driver cone, using a Behringer ECM8000 mic.

Hmm... Are you aware of baffle step? Unless I miss something you will have to add about this to your close-field measurement to get the far-field response.
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Old 25th February 2004, 08:42 AM   #5
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Quote:
Originally posted by Svante



Hmm... Are you aware of baffle step?

Yes, I did some simulations when positioning the driver. It has both an x and y offset from the centre point; that plus rounding-off the baffle edge made it less wiggly overall than the plot you posted.

I'm undecided whether to (a) leave the speakers alone and fiddle with the room & positioning, (b) add a passive compensation network to the speaker or (c) put compensation between source and power amp. I'm also not sure how I'm going to measure the result, as my experiences to date suggest in-room response is so messy a little 6dB step is lost in the noise.

There's always (d), listen with speakers positioned 10cm from head...

Cheers
IH
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Old 25th February 2004, 10:03 AM   #6
Svante is offline Svante  Sweden
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Quote:
Originally posted by IanHarvey


Yes, I did some simulations when positioning the driver. It has both an x and y offset from the centre point; that plus rounding-off the baffle edge made it less wiggly overall than the plot you posted.
Ahh, nice, I just guesstimated a y offset from your picture, but as you say, it is likely that an x offset would dewhiggle the response a bit more. BTW, What *are* the measures?

Quote:
Originally posted by IanHarvey


I'm undecided whether to (a) leave the speakers alone and fiddle with the room & positioning, (b) add a passive compensation network to the speaker or (c) put compensation between source and power amp. I'm also not sure how I'm going to measure the result, as my experiences to date suggest in-room response is so messy a little 6dB step is lost in the noise.

There's always (d), listen with speakers positioned 10cm from head...

Cheers
IH
I think most people nowadays use a truncated impulse response to measure far-ish field. How did you go about to get your curves?

PS (d) is nice. You won't have to bother about room acoustics, then...
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Old 25th February 2004, 10:14 AM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by IanHarvey

a little 6dB step is lost in the noise.
Cheers
IH
A 6dB step, applied over a band makes a rather large difference,
and will allow postioning away from walls for good soundstaging
and optimum use of room gain in the bass.

I'd add it between pre and power amplifier, easily adjustable.

Its also possible to add by modifying the PA feedback loop for
6dB more gain at LF.

sreten.
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Old 25th February 2004, 10:41 AM   #8
Taco is offline Taco  Netherlands
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Quote:
Originally posted by Svante



Hmm... Are you aware of baffle step? Unless I miss something you will have to add about this to your close-field measurement to get the far-field response.

What program are you using? Looks very interessting .
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Old 25th February 2004, 11:33 AM   #9
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Quote:
Originally posted by Svante


Ahh, nice, I just guesstimated a y offset from your picture, but as you say, it is likely that an x offset would dewhiggle the response a bit more. BTW, What *are* the measures?
I don't have them to hand at the minute; the X offset is about 1.5cm if memory serves. I'll post some construction details when I'm back at home.

Quote:

I think most people nowadays use a truncated impulse response to measure far-ish field. How did you go about to get your curves?
I'm using AudioTester (http://www.audiotester.de/), using its frequency-sweep mode. It does have a waterfall-plot mode (which I've not really played with) - is this what you mean?

I didn't want to simply simulate the baffle diffraction results and then design its inverse as compensation; in the room where they will eventually live the baffles will be effectively flush with various bits of furniture. I'd like to actually measure the speaker+room together before fiddling with the frequency response.

Cheers
IH
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Old 25th February 2004, 11:55 AM   #10
Svante is offline Svante  Sweden
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Quote:
Originally posted by Taco



What program are you using? Looks very interessting .

Home brewed: http://www.tolvan.com/diffract.exe
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