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Old 11th July 2014, 12:21 PM   #1
djduck is offline djduck  Estonia
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Default Improving cheap PA speakers

Hello!

After cleaning out the A/V rooms I got a pile of free audio equipment.
Two pairs of very nice home audio speakers, a very nice soviet reel-to-reel player and a pair of cheap HQ Power PA speakers. We used to have these hanging from the ceiling, above the stage. However, they could not compete with the Phonic and JBL EON we also run and so they were taken down. That's pretty much the story of their lives
So I got them home, wired them to my amplifier and gave them a test. First impressions: meh. Muddy bass, one tweeter was not working, other one sounded crappy. And when I went to pick up one of them, one of the handles just crumbled into the box. For some reason, the plastic was literally as brittle as potato chips.
I took them apart, and was pleasantly surprised. Cabinets are particle board / MDF, but decent thickness, cabinets are cross-braced, they have crossovers, instead of just a cap in series with the tweeter, wiring is decent gauge copper, woofers are pretty good, too. tweeters are crappy piezo, though.
The non-working piezo had a broken wire, which I re-soldered. I also stuffed the boxes with acoustic damping or whatever it is (cotton?)
Broken handle got replaced by a piece of wood
Second test: Highs are now better, since both tweeters work, bass in much more controlled and powerful.
So, I have had them for a few few months now and used them for a few outdoor events, they play pretty loud
However, I'm still not entirely happy with them. I would like to change the tweeter crossover electrolytic for a film cap and replace the piezo with a proper horn.
I need a recommendation for a pair of good budget horns. They are 3"x7"
Also, I might replace the 10" woofers with something better. Current ones are 400W. They are nice, but could be better, so if anyone could recommend a good 10" woofer, go ahead.
Any other recommendations on how to make them better are welcome.
They are my first pair of PA speakers BTW, and I quite like PA. When the money comes in, I'm actually thinking of buying some better, used PA speakers.

Thanks in advance!
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Old 11th July 2014, 07:39 PM   #2
djduck is offline djduck  Estonia
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Well, today I polished these turds even further. I replaced the 4.7uF electrolytic (originals were miss-matched size and brand ) with film capacitors. This proved to be a huge improvement, the highs are cleaner, and the piezos no longer pierce your ears. High were really harsh and shrill and dirty, now much more subtle and clear and detailed, not too bad for cheap piezo horns.
Again, if anyone has any tips on what else to do, then please, let me hear them.
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Old 11th July 2014, 08:56 PM   #3
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I think if you take this too far you will spend more that what you would on a new set. The idea behind buying a used set can pay off in a big way.
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Old 11th July 2014, 09:08 PM   #4
djduck is offline djduck  Estonia
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Damping material and film caps were both free. I honestly have put 0$ into these, and maybe an hour of work tops.
Used good quality PA is honestly kind of expensive here. If I find any used PA ads, I will ask here if the price is good.
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Old 11th July 2014, 09:11 PM   #5
djduck is offline djduck  Estonia
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New set of these speakers is about 160-170$ actually, which is a good price in my opinion, if you want a pair of cheap and loud party speakers. They are not good enough for actual concert or live event use, but for a home party, they are very good for the price, and even better for me, considering the price I got them for
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Old 11th July 2014, 11:16 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

A proper peizo x/o and a proper dynamic tweeter x/o
are two very different things usually. Simply buying
used better PA speakers and selling them on is a far
better bet than buying new replacement drivers.

rgds, sreten.
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Old 11th July 2014, 11:34 PM   #7
JMFahey is offline JMFahey  Argentina
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Electrolytics?/film caps?
Piezos do not need or use "crossover capacitors" , much less such high value as 4.7uF
So I guess the "improvement" you hear is mostly placebo effect.

Quote:
I honestly have put 0$ into these, and maybe an hour of work tops.
Unless you are *incredibly* lucky you will NOT find better speakers at that price.
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Old 11th July 2014, 11:48 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

The approaches to piezo x/o's are myriad and there
are no hard and fast rules. In a simple case 4.7uF
might be acting as attenuator more than a x/o.

Some piezo's incorporate transformer coils,
(and / or other non-obvious components),
complicating the matter even further.

Its now a bit of a minefield without measuring.

rgds, sreten.
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Last edited by sreten; 11th July 2014 at 11:56 PM.
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Old 12th July 2014, 08:34 AM   #9
djduck is offline djduck  Estonia
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Cap change was not placebo. It did work. Honestly, tweeters were really harsh before and I could not stand near the speakers at high volumes, because of very sharp highs.
It looks as this Xover was designed for a compression tweeter and then used with a piezo. It has a 20ohm 20w resistor, then a 4.7 cap and then piezo. For bass, there is one inductor.
Maybe crossover can be improved? Remove the cap and resistor for piezo? And add something for the bass section?

Here are the specs: (translated from Estonian)
Woofer: 10"
Tweeter: 3" x 7" (76 x 178mm)
Power MAX/RMS: 400W/200W
Sensitivity: 90dB
Frequency response: 30-20000Hz
Impedance: 8 ohm
Magnet: 24oz (680g)
Size: 505 x 380 x 305mm
Weight: 10kg

Best wishes, Joel
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Old 12th July 2014, 01:00 PM   #10
Decode is offline Decode  China
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If i am right, a PA speaker means speaker with transformer and pro speaker means low impedance speaker or without any transformer.

As one PA speaker manufacturer, we are offering a wide range of speaker with transformer, so i want to ensure this is a correct definition, please help me if you know it well.

PA System,Public Address System,Conference System,IP Network Audio System, IP PA System, IP Intercom System, Digital Voice Evacuation System,wireless microphone,ceiling speaker,horn speaker
info@decodesecurity.com
Skype: publicaddress
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