3 way JORDAN

[chris ma]

Originally posted by Peter Daniel


Maybe it's time to invest in Radio Shack SPL meter?

Or, I could lend you mine. Accompanied by a Stereophile test CD, it allows to make pretty accurate in room response measurements.

Silly me, I did pay $80 for one from Radio Shack SPL with digital display 3 years ago and a good tripod from my camera days and I have a few test CD like the Denon Hi Fi Check CD and the Sheffield Lab -My Disc but I do not know how to utilise all these thingies, thanks for the offer Peter, I think I need to be told what to do with them rather, and what the reading/result really mean, how to interpet it I guess...

Chris

PS more importantly what to avoid while testing so as to not damaging any components...
I thought SPL meter only used for checking how loud the sound is not its frequency.

[Peter Daniel]

Here's the warble-tone tracks recorded on CD:

[Peter Daniel]

And here's short description how to use it. I'm not using Radio Shack meter, but Mitey Mike (from Speaker builder article) and Fluke true dB meter and just write down the readings for ea. frequency and this gives me a rough idea of the response. I use normal listening levels and never damaged the tweater in this way.

[chris ma]

Hi,

Active cross over dial set at 550 hz, bi-amp JX150 and JX53. The ribbon when in use is connected to a 2.6uf cap then a 3 ohm resistor in series to + terminal, then a 5.6 ohm resistor across the ribbon terminals.

Can someone explain the following numbers for me please.

Test with volumn control constant at pre-amp and the SPL meter set at C rating and fast response.

Frequency..........With ribbon..........No ribbon
4 hz ....................--..........................--
8 hz ....................--..........................--
16 hz...................--..........................--
32 hz...................55........................55
63 hz...................63........................63
125 hz.................72........................72
250 hz.................70........................71
500 hz.................64........................63
1 khz...................66........................66
2 khz...................77........................75
4 khz...................74........................75
8 khz...................76........................77
16 khz.................50........................--
20 khz.................--..........................--

What I should expect this kind of result for a pair of good speakers, please bear in mind this is my first DIY speaker.

Thanks in advance,
Chris

The reference track is the 1khz with 66 recorded.
The SPL meter is on a tripod at 12 feet away from each speaker pointing at the mid point of the two speakers about the same height as the ribbon from ground and the speakers are 9 feet apart, zero toe in.

[Colin]

Hi Chris

The JX53s are designed for a pretty severe toe in - about 30 degrees from the back wall. The axis should cross well in front of the listening position, to avoid the precedence effect (the sound seeming to come from the nearest speaker when you move off centre). There's an explanation of this on the Jordan site.

I find it works very well. The responce of the JX53 (and even more so, the JX92S) takes account of the toe in, so they can sound a little bright if you're on axis with the pair.

I'm not sure how the toe in would alter the sound when they are on an open baffle, or how the bass would be altered. I'll be interested to hear what you think.

Also, I don't know the ribbon driver, so having that in circuit may modify the toe in you want to use.In any event, your project is certainly keeping the rest of us on our toes ...

Colin

[Peter Daniel]

Here's, for comparison, what I measured on mine, in wall speakers, recently. (Raven2, fullrange triangle and PHL to fill bottom end)

Frequencies are on the left, some measurements for single drivers only, second from right column is the final reading.

[chris ma]

Originally posted by chris ma

Test with volumn control constant at pre-amp and the SPL meter set at C rating and fast response.

Frequency..........With ribbon..........No ribbon
4 hz ....................--..........................--
8 hz ....................--..........................--
16 hz...................--..........................--
32 hz...................55........................55
63 hz...................63........................63
125 hz.................72........................72
250 hz.................70........................71
500 hz.................64........................63
1 khz...................66........................66
2 khz...................77........................75
4 khz...................74........................75
8 khz...................76........................77
16 khz.................50........................--
20 khz.................--..........................--

The reference track is the 1khz with 66 recorded.

So what is the ideal in theory if for 1 khz I recorded 66dB as reference? Do I try to achieve 66dB for all other frequencies too. I notice there is a dip at 500 hz and 1 khz what can I do to push them up tp the seventies like the rest? or pull the rest down to 66 dB ?

Chris

[Peter Daniel]

You should try to get the numbers as close as possible. Some are easier to adjust than others, so you play with those

[chris ma]

I have reversed the polarity of the JX53 and it sound a lot better but for the SPL measurement it remains the same. And to confirm the question from Bartek, yes there is reasonable good sounding bass when I can feel the leather sofa massaged my behind when loud music like pipe organ and the double bass with loud jazz.

Back to the SPL dip between 500hz and 2khz, will the JX53 need to have a series, parallel notch or zobel filter? Not that it really matters but it already sound very good a big improvement over the Mirage speakers with 2 mono amps..not bi-amping I mean..also considering the basement is not finished, the walls are covered with vapour barrier, no ceiling, cement floor, 1/4 of the walls are just concrete(foundation), 3 large plan glass windows with no curtain, sheet metal air duct etc etc...and asking the inefficent speakers/amps to fill a 900 square foot of empty space..
I am happy.

Chris

[goliardo]

Chris,

I have build my speakers with the same Jordan drivers but used a closed box (actually aperiodic loading) for the JX150 and an open baffle for a pair of JX53 (connected in series) instead. I use a 1st order series Xover with a zobel on the JX150. Few comments on your project and measurements:
1. I think zygibajt is right. The 'car speaker etc." sound was probably caused by the 200 Hz Xover frequency (too low). I have no such problem with a Xover frequency of about 800Hz (nominal; actual frequency, who knows..I do not have the equipment to measure it)
2. the measurements would be typically carried out with the slow, not the fast setting of your SPL meter for stimuli such as the tones from the Stereophile CD
3. I have used the same CD and the analog RS SPL meter, for which one has to adjust the measurements at high and low frequencies; not sure whether this needs to be done for the digital meter too
4. I am a bit puzzled by your measurements, not so much by the 500 Hz hole (baffle diffraction effect of some sort? I have a 3-4 notch between 125 and 400 Hz possibly for the same reason), but by the large drop in level above 8 kHz with no ribbon. Even with the ribbon you seem to get a lot of attenuation at high frequencies My speakers show a drop of 3-4 dB above 8 kHz. Never felt the need I am missing HF energy (although a ribbon might provide an even cleaner sound on top)

Ciao,

Valter