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Old 8th June 2010, 09:08 PM   #601
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Maybe a stupid question, but here it goes:

I want to make something similar to the Boominator but with only 2x10" woofers. Is it possible to parallelle the piezo and the woofers to lower the impendance to 4 ohm?
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Old 8th June 2010, 09:23 PM   #602
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No paralleling a piezo and a woofer leaves you with the same impedance as just the woofer. Piezos aren't like other tweeters. Also with a crossover and a regular kind of tweeter, the impedance does really change either as each driver is covering it's own part of the spectrum and therefore there is not overlap (read: not really parallel)
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Old 10th June 2010, 08:45 AM   #603
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Hi!

I have a question regarding the Zomax HP100. I've just finished building a Boominator clone and tested it outside this past weekend. I actually don't think the Zomax piezos sound very good. The sound is quite "dull", so to speak: there is not very much to give around 8-10kHz and there is some really nasty sounds around 4kHz.

Now, Saturnus, you say that these piezos sound much better than anything else you've tried, so I'm beginning to think I've done something wrong. The polarity is correct, and I'm using carbon resistors in series. Any suggestions on what might be wrong? Or maybe I'm just being picky =)

I'm considering replacing the Zomax piezos with the Motorola KSN1005A (or Rila SA05) which I know has more "high end". Also, In addition to HP-filtering the AMP-6, I'll be building a simple 5-band EQ based on the Sanyo LA3600 circuit to compensate for the dips and peaks in the frequency response.

oh, and BTW here a link to my build-blog (sorry, it's in Swedish, but the pictures it not =)):
Malen 2010
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Old 10th June 2010, 10:24 AM   #604
ThokN is offline ThokN  Denmark
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That's interesting. I'm just going to order some the carbon resistors, but I've become in doubt since we opened our old boominator, discovering that we didn't have the resisters in that. And I remember now that we did actually try with the resistors, but ended up excluding them because we found the sound dull when they were installed.

I'm curious to your answer to this, Saturnus.
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Old 10th June 2010, 10:29 AM   #605
ThokN is offline ThokN  Denmark
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Another thing... I noticed that we connected the speakers out of phase in the old boominator, (so that one side push out, the other push in), and I don't know why we did that. Maybe an error. I've read a little about phase connection, but it's difficult to find anything where two speakers in a ported enclosure are mounted magnet to magnet.

I suppose that they should actually be connected in-phase, right? Meaning that they both 'suck' inwards at the same time, and push outwards at the same time?
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Old 10th June 2010, 03:11 PM   #606
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Hey guys, another question:

I have bought these two speakers
| IMG Stage Line 110540 |Piezohorn MPT-177 Hjttaler-enheder Piezo Diskanter
| Monacor 103990 |10'' hjttaler SP-252E Hjttaler-enheder Bass-enheder 10" Bass / 4 ohm

But I can't figure out, how to find the right filter for the base, and resistance for the piezo. Are there any program to
calculate these kind of things or what?

How do I do that?
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Old 10th June 2010, 08:58 PM   #607
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The answer is simple. It needs about 100 hours of playing time to "burn in" before the HP100s "open up". And I'd not call it "dull" to start with, just "unengaged". But that change completely after about 100 hours.

On another note though. The HP100s with the correct resistor as listed here will never sound like another piezo, simply because they are much better than any other piezo. When you really listen to them (after burn-in), you'll notice they play everything, even the highest notes without making them sharp or noticable in any way but simply be there, playing effortlessly, to be noticed or not.

And yes, definitely in-phase, otherwise there's no bass at all.

Last edited by Saturnus; 10th June 2010 at 09:06 PM.
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Old 10th June 2010, 09:18 PM   #608
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Quote:
Originally Posted by jimtegel View Post
I'm considering replacing the Zomax piezos with the Motorola KSN1005A (or Rila SA05) which I know has more "high end". Also, In addition to HP-filtering the AMP-6, I'll be building a simple 5-band EQ based on the Sanyo LA3600 circuit to compensate for the dips and peaks in the frequency response.

If you are switching to those inferior piezos I'll be most happy to take the HP100s of your hands as they're no longer in production, and no longer in stock with any European reseller.

I fear though that after you have had them burn in, and really listened to them, you'll know why I love them so much on the Boominator. It's all about musicality, the HP100s you can listen to and be amazed at their detail for hours and hours, where you get tired of most other piezos after 5-10 minutes.

Constructed like described here, and put on grass on the ground outside with at least 10-20 meters to the nearest wall, there are no serious dips and peaks in the frequency range. It's -+2dB from 102Hz to 17KHz.

Last edited by Saturnus; 10th June 2010 at 09:22 PM.
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Old 11th June 2010, 07:10 AM   #609
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Ok, that might explain it. I've actually never heard of burn-in for piezos: I know it makes a huge difference for speakers in general but it didn't cross my mind that it's important for piezos aswell =) Guess I'll just leave them with some noise on for a while then =)

But still I'm a bit concerned about the HF-response... but you're saying that it will improve drastically after the burn in period? Because right now it's quite depressing. We did some measurements in a professional echo-free chamber using Brel & Kjr mic @1m and the result is attached in this post.

As you see there are quite severe variations in the HF-response. Also there is some heavy distortion (3rd-5th) around 6kHz (not visible here though). Based on this maybe you understand my EQ cravings =)
Attached Images
File Type: jpg freq_response.jpg (42.2 KB, 571 views)
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Old 11th June 2010, 08:29 AM   #610
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Just want to add that that's exactly my goal: to have something that is "musical" and not "tiresome" as you mention. But at the same time I want something that can "reach out" outdoors, which I don't think my Boominator does in it's current state. It's all about finding the right compromise. That's also why I want an EQ: to do some manual "loudness" compensation, and to be able to compensate for different environments (and even song types).

But don't get me wrong, I belive you when you say that the HP100 is great!
Guess I'll just have to give it some time to get convinced =)

BTW: Anybody else going to Roskilde this year? Would be nice with a Boominator meetup =)
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