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Old 13th June 2013, 11:13 AM   #281
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally Posted by charly chile View Post
Thanks Ra7,
To be honest I am not very happy, It sounds more correct, more like a wall with all frecuencies there, but not sure, something missing, like it sucked life? sorry, not sure about how to describe it in technical terms since I am not sure what is going on. Could be too many things, so the only option is keep experimenting.
1) I am presumming that maybe I just like highs higher, so I can fell all the micro detail and bronzes, even if it's not flat...
2) other posibility is that I am equalizing too aggresively, since I am applying tons of dB EQ here and there. So I want to review all I have done and see If I can apply less EQ. I am thinking that maybe, move from a 10W amp to a 100W amp for the woofer may put the woofer beside the horn, so there will be less necesity to attenuate the horn. Also want to do as much attenuation as possible in analog.... I felt like, maybe, dynamics suffered a bit... but I am only GUESSING at this point. more work to do...

3) Pending is the work with the woofer, and it's crossover point is now at 500hz. This horn/driver is suppoused to go far lower so I expect to be measuring again and doing some comparisons.

4) I think I need to think and listen a lot about what is going on here...
A flat response doesn't mean it sounds good. It can be it is flat because there is a phase difference and the sum is good but further a way from the loudspeaker it isn't that flat any more.

Measure a meter for the speaker, and measure it on the listening position about 3 or 4 meter from the loudspeaker. And see where a drop or raise in the response is.

Your response seems to raise about 5dB from the mid section up, for what I have experienced it comes very close the level from low to mid and the level of the tweeter to the rest. you need to tune it very precise. Measure edit and listen until it sounds good.

To measure the low mid to high response you use a small time window of about 5 msec with low smoothing or no smoothing to see all details of the measurement.
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Last edited by Helmuth; 13th June 2013 at 11:38 AM.
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Old 13th June 2013, 04:33 PM   #282
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Thanks for all your valuable advice guys. I expect to resume measurements this week.
OT: Last night I went to listen to the system of a friend. He had a new preamplifier from Roger Modjeski, very good stuff in my opinion.
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Old 13th June 2013, 05:34 PM   #283
ra7 is offline ra7  United States
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Here's some reading you can do before taking the next measurements:
Crossover mods for the AR4x - Mods, Tweaks, and Upgrades to the Classics - The Classic Speaker Pages Discussion Forums

In the thread above, David Smith, who is a well regarded speaker designer, goes through a new crossover design for an old speaker. Pay close attention to the phase overlap that he talks about. Helmuth above also mentioned it. It is very important that the phase of the two drivers overlap in the crossover region.

Phase is nothing but the arrival time of frequencies relative to one another. For crossover design, the only thing that matters is the phase of one driver in relation to the other. In that linked thread, Dave shows how you can get that using Holm. Here's a quick summary of the procedure:
1. In the device and signal tab, check the box that keeps in/out stream active. This will keep time.
2. In data analysis tab, choose Causal impulse.
3. Make measurement of tweeter or woofer. Keep position of mic fixed for entire process. I like to position the mic at the vertical midpoint of the woofer and the horn. That way the vertical lobe will be symmetrical about the mic axis.
4. Then in data analysis tab, use the time locked feature. Click Use. This will lock the time at the previous measurement. The next measurement will be in relation to the previous measurement. This means, you will get correct phase relationship between drivers.
5. Measure next driver.

Now you can see the phase of the two drivers in relation to one another. When you start putting in the crossover, or every time you make a change to any driver, you will need to repeat the entire process again, because filter changes phase. When you are done, amplitude must sum to flat, and phase must overlap through the crossover, atleast until the individual drivers' outputs are down about 25-30db. This will give a smooth transition from one driver to the other.

Last edited by ra7; 13th June 2013 at 05:38 PM.
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Old 17th June 2013, 04:23 PM   #284
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Going back to pages 23 and 24, there was some speculation on how low the BMS mid range could go. The long answer seems to also be 300hz.

Here is a screen shot of two different horns with the BMS 4592 on them. One is a DDS horn, about 22"x22" in size. The other is a much larger horn, about 48" x 33", and about 5' long. (56cm x 56cm, and 122cm x 84cm x 153cm) The smaller horn is limited by its size, but the much larger horn shows the lower limits of the mid driver. Which is right at 300hz.

I am not sure why of the differences in sensitivity. I am wondering if it is mostly distance. As in, the larger horn, the mic is over one meter further from the driver. I would think that the volume would start dropping as the distance gets further from the horn mouth, not from the driver mouth. There is also the possibility that something else such as amp volume changed from one test to the other.
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Old 17th June 2013, 05:04 PM   #285
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Hi Jack,

On my end Ive been listening to my system with 300hz and 6.3khz croosever poitnts with BW18db/oct filters.
I am mating this with a 18inch woofer Eminence Omega 18a pro in a U-Frame (open baffle).
I am using three amps. Solid state for Woofers.


I think the horn sounds great: guitars, voices and up sound natural and alive.
I have lack of live and like a hole (that is hard to measure but I can listen to it) in the mid-low range, like Toms in a drum set. I am guessing it's Woofer behavior and Bass Integration.

I think the solution for this needs a 15in Woofer to have mids that perform better.
Some friend was suggesting a Sealed box with a Linkwitz transform.

Also some times I feel some distorsions, but my 2360A have some cavities inside where the fiber glass colapsed in the joint of the two sections of the horn, the damage is very noticeable when you look at it, and I guess it has to produce some damage to the sound. That is why this week I plan to fix those imperfections with some kind of epoxy, and then I am also painting the horns with a "wine" color.

Going back to woofers, I dont want to have more than 1 woofer, so the only option I see is going active. What do you think about a sealed box? Any suggestions for drivers? I was looking at the internet at JBL and TAD. Tad is too expensive. I am thinking if a JBL 15in woofer could to a fine work here. or maybe more modern drivers?

Regarding equalization, I discovered that too many filters kind of break the sound and suck life. So now I am just applying only one EQ filter with a smile shape to raise the extremes. Even when this didn't solve everything, I think result was much better.

Best
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Old 17th June 2013, 05:14 PM   #286
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Jack,
Maybe if you measure from the listening position, that will be better to compare sensitivity.
Best
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Old 17th June 2013, 05:55 PM   #287
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Quote:
Originally Posted by charly chile View Post
I was looking at the internet at JBL and TAD. Tad is too expensive. I am thinking if a JBL 15in woofer could to a fine work here. or maybe more modern drivers?
My thoughts are buy anything but a vintage JBL. There are so many speaker companies that offer better things than you can get from JBL. (All of their good speakers go into systems, not sold as components.) I can never believe how much my used JBL speakers go for on eBay. I get more than I paid for them 20 years ago, used. And now used much more. A new speaker from any other company will be a better purchase. If you get something cheap, it will not have the added cost of paying for the three letter logo, and if you buy something that costs as much as a JBL, you will get better quality.
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Old 17th June 2013, 07:48 PM   #288
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I was owing some pictures. Here there are a few shots from the weekend:

Click the image to open in full size.

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Old 17th June 2013, 09:20 PM   #289
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Quote:
Originally Posted by Jack Arnott View Post
Going back to pages 23 and 24, there was some speculation on how low the BMS mid range could go. The long answer seems to also be 300hz.

Here is a screen shot of two different horns with the BMS 4592 on them. One is a DDS horn, about 22"x22" in size. The other is a much larger horn, about 48" x 33", and about 5' long. (56cm x 56cm, and 122cm x 84cm x 153cm) The smaller horn is limited by its size, but the much larger horn shows the lower limits of the mid driver. Which is right at 300hz.

I am not sure why of the differences in sensitivity. I am wondering if it is mostly distance. As in, the larger horn, the mic is over one meter further from the driver. I would think that the volume would start dropping as the distance gets further from the horn mouth, not from the driver mouth. There is also the possibility that something else such as amp volume changed from one test to the other.
The inverse distance drop starts at the driver diaphragm itself and continues throughout the horn.
If you took measurements 1/2 meter and at the horn mouth, then inside the horn you will notice SPL will continue to increase at roughly 6 dB each halving of distance.

Horn low frequency cut off and sensitivity is a function of flare rate and other design features, I'd expect the 4592 could go lower than 300 Hz on some horns.

As an example, the response of an EVDH1AMT (3" diaphragm driver) on a 22.5" x 11.25" x (approximately) 17" deep horn is shown.
In spite of being a fraction of the size of either of the horns you tested, the LF cut off of this horn (a WS Paraline) is much lower, around 200 Hz compared to 300 and 500 Hz for your larger horns.

Art
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Old 18th June 2013, 12:20 AM   #290
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Quote:
Originally Posted by weltersys View Post
The inverse distance drop starts at the driver diaphragm itself and continues throughout the horn.
If you took measurements 1/2 meter and at the horn mouth, then inside the horn you will notice SPL will continue to increase at roughly 6 dB each halving of distance.
Art
This is wonderfully wacky for me. I had no reason to consider it before yesterday.
The reason its so fun, is that the spectrum is continually changing through out the horn. Not only is the SPL changing, but the makeup of that SPL. Because the lower frequencies will take longer, (more horn) to impedance couple, there will be less of the lower frequencies closer to the throat of the horn, and then, as the lower frequencies grow in SPL as they couple, the higher frequencies are already dropping in SPL.

So, does a frequency that has not been coupled yet, and therefore not reached its higher SPL from horn loading, still drop in inverse distance? I would think it would have to. So it would be getting quieter, and then louder.

Am I interpreting this all correctly?
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