pth1010 (newer) - 2435HPL Foam Plug
Norman Bates had opined that since there was little in the way of parallel walls in the waveguide, there would be little if any HOM's.
In order to see whether a foam plug, ala Geddes, was beneficial, I made one up, as pictured. One layer of the foam was the same thickness as the cylindrical bore in the PTH1010, and two additional layers were added that roughly follow the contour of the wave guide. Yes, I know my scissor skills could use some improvement.
I did a frequency response at about 100db, and a distortion plot, also attached. The distortion was plotted normalized to the fundamental, to get rid of the FR differences. The distortion plot was where I expected to see the difference in HOM's if they were reduced. Geddes said there would be about a DB db of FR difference, IIRC.
So in the charts, I see Geddes' prediction of FR difference is correct, and that distortion is very slightly reduced.
What do you think?
Norman Bates had opined that since there was little in the way of parallel walls in the waveguide, there would be little if any HOM's.
In order to see whether a foam plug, ala Geddes, was beneficial, I made one up, as pictured. One layer of the foam was the same thickness as the cylindrical bore in the PTH1010, and two additional layers were added that roughly follow the contour of the wave guide. Yes, I know my scissor skills could use some improvement.
I did a frequency response at about 100db, and a distortion plot, also attached. The distortion was plotted normalized to the fundamental, to get rid of the FR differences. The distortion plot was where I expected to see the difference in HOM's if they were reduced. Geddes said there would be about a DB db of FR difference, IIRC.
So in the charts, I see Geddes' prediction of FR difference is correct, and that distortion is very slightly reduced.
What do you think?
Attachments
Good looking graphs.
I have to get holes drilled to try the newer ones.
The new ones have 2 holes a side while the olders have 3.
I think it has taken me a month just to pull a horn from a working cab to compare depths.
I've been pretty happy with the setup.
12" 2 way seems to be a steady plateau for me.
Thanks for the graphs pblossom.
With or without foam, response looks real good.
I have to get holes drilled to try the newer ones.
The new ones have 2 holes a side while the olders have 3.
I think it has taken me a month just to pull a horn from a working cab to compare depths.
I've been pretty happy with the setup.
12" 2 way seems to be a steady plateau for me.
Thanks for the graphs pblossom.
With or without foam, response looks real good.
@mortron, I had the 3" 2432 in a JBL 2384 waveguide and did not like the sound or measurements. Could be different for the PTH1010...
I moved to a 4" 2453H-SL with the aquaplas coating. Much smoother frequency response and lower distortion response compared to 2432 on the 2384.
Pretty much agree with the synopsis here: Just purchased a pair of JBL 4722n speakers. - Page 129 - AVS Forum | Home Theater Discussions And Reviews
If you scroll back some pages on the AVS link, you can see the measurements for all of the drivers listed, but again maybe different on the PTH1010.
I moved to a 4" 2453H-SL with the aquaplas coating. Much smoother frequency response and lower distortion response compared to 2432 on the 2384.
Pretty much agree with the synopsis here: Just purchased a pair of JBL 4722n speakers. - Page 129 - AVS Forum | Home Theater Discussions And Reviews
If you scroll back some pages on the AVS link, you can see the measurements for all of the drivers listed, but again maybe different on the PTH1010.
That 2453SL is a good deal indeed if they are as good as most say. Tempting.
I will have to do more reading on these guides. I always was drawn to the 1.5" range because I figured it'd allow me to cross under 1000hz, and still be able to play higher than a 2". I guess that's where the M2 for the Poor's thread comes into play too tho.
Norman, is it the depth of the guide that makes the PTH1010HF preferable with passive networks? I presume with the 2384 presents a bit more of a time delay issue than the 1010 as well as other differences.
I will have to do more reading on these guides. I always was drawn to the 1.5" range because I figured it'd allow me to cross under 1000hz, and still be able to play higher than a 2". I guess that's where the M2 for the Poor's thread comes into play too tho.
Norman, is it the depth of the guide that makes the PTH1010HF preferable with passive networks? I presume with the 2384 presents a bit more of a time delay issue than the 1010 as well as other differences.
Pth1010hf-1
Reconingspeakers.com has them for $64 US dollars each plus shipping.
Comparing 750hz horn to 1.2khz horn seems unfair, but here we go.
I have lived with the 2384 with 2435hpl maybe 3 years, 24db @750hz or 1khz when going as loud as i dare.
It is impressive.
Now i have the pth with 2431, jbl sheet says 1.2khz passive, 12db.
More accurate.
More revealing.
Seeing the roundover and the slightly rounded over walls, it isn't doing much wrong.
Sitting near or far is good.
Maybe it is the combination of horn plus 1.2khz crossover point, i don't know.
Looking at post 663 on jbl m2 for the poors, graph is close to the m2.
JBL M2 for The Poors
Reconingspeakers.com has them for $64 US dollars each plus shipping.
Comparing 750hz horn to 1.2khz horn seems unfair, but here we go.
I have lived with the 2384 with 2435hpl maybe 3 years, 24db @750hz or 1khz when going as loud as i dare.
It is impressive.
Now i have the pth with 2431, jbl sheet says 1.2khz passive, 12db.
More accurate.
More revealing.
Seeing the roundover and the slightly rounded over walls, it isn't doing much wrong.
Sitting near or far is good.
Maybe it is the combination of horn plus 1.2khz crossover point, i don't know.
Looking at post 663 on jbl m2 for the poors, graph is close to the m2.
JBL M2 for The Poors
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Good question.
Now that the weather is changing this sounds like excellent indoor sport.
I will do some more testing.
Thanks DT
How will the sound will be affected?
Hello All,
Too much fun!
I have been listening to the D2 M2 driver waveguide for six months I do not want to take the driver and waveguide out of service to test it.
So instead I have been testing the JBL D2408H2 Compression Driver and JBL PT95 Waveguide in its place. The tests are done with the Quant Asylium Q401 Analyzer and QA460 amplifier and built in current sense resistor. Matt of QA has the software programed to calculate all the good speaker impedance stuff. I have the APx555 analyzer in the lab up the road.
I have the QA460 set up with flexiable fine stranded 12AWG test leads.
The first plot is done with a 4Ohm Mills non-inductive resistor in the place of a speaker driver to see what the QA401 and QA460 will do. There is a little capacitive influence in the impedance and phase plots, perhaps from the test leads.
The second plot is the D2408H2 Compression Driver and JBL PT95 combination results.
The third plot is the D2408H2 Compression Driver and JBL PT95 combination in series with a 4Ohm Mills non-inductive resistor.
The fourth plot is the D2408H2 Compression Driver and JBL PT95 combination in series with a 4Ohm Mills non-inductive resistor plus two 4Ohm Mills non-inductive resistors, a total of 8Ohms in parallel.
With the resistor network in place I am seeing attenuation plus reduced peak to peak impedance and reduced phase shift.
Any other observations or thoughts about how the sound will be affected?
Thanks DT
Hello All,
Too much fun!
I have been listening to the D2 M2 driver waveguide for six months I do not want to take the driver and waveguide out of service to test it.
So instead I have been testing the JBL D2408H2 Compression Driver and JBL PT95 Waveguide in its place. The tests are done with the Quant Asylium Q401 Analyzer and QA460 amplifier and built in current sense resistor. Matt of QA has the software programed to calculate all the good speaker impedance stuff. I have the APx555 analyzer in the lab up the road.
I have the QA460 set up with flexiable fine stranded 12AWG test leads.
The first plot is done with a 4Ohm Mills non-inductive resistor in the place of a speaker driver to see what the QA401 and QA460 will do. There is a little capacitive influence in the impedance and phase plots, perhaps from the test leads.
The second plot is the D2408H2 Compression Driver and JBL PT95 combination results.
The third plot is the D2408H2 Compression Driver and JBL PT95 combination in series with a 4Ohm Mills non-inductive resistor.
The fourth plot is the D2408H2 Compression Driver and JBL PT95 combination in series with a 4Ohm Mills non-inductive resistor plus two 4Ohm Mills non-inductive resistors, a total of 8Ohms in parallel.
With the resistor network in place I am seeing attenuation plus reduced peak to peak impedance and reduced phase shift.
Any other observations or thoughts about how the sound will be affected?
Thanks DT
Attachments
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