Using piezos with transformer

24.39.245.6

Posted on November 20, 2012 at 19:06:32

Evad.5150
Audiophile

Posts: 7
Joined: November 19, 2012

Hello everyone. I'm new here but need some advice on piezos. I recent bought 3 sets of klipsch heresies.... 2 way models without a tweeter. I had some 2x5 piezos so I decided to install these using the transformer circuit posted here. Now, it seems that using a 1uf crossover feeding the 8r 100uh zoebel (8 ohm load) would yield a xover frequency of 20khz sloped at 6 db per octave, am I correct on assuming this? I used the stock heresy e2 crossover (which as you probably know usually feeds the t35 tweeter from the autoformer tap that multiplies the 8 ohm tweeter by 4 (32ohms) and a total capacitance of 1uf. Now a first order xover of 1uf at 32 ohms equates to 5khz (I know the heresy e2 produces a 2nd order due to the auto former but I'm just trying to compare the use of a 1uf xover). 1uf at 8 ohms equates to 20khz as I stated above. Using this with my piezo/transformer/zoebel, did not produce much more volume than hooking the piezo up by itself. Now, when I placed a 2uf cap feeding the zoebel I got quite an increase in volume actually slightly louder than the k53k mid horn. Per my calculations. This should be a 10khz 6db crossover and to my ears sounded very good!!!! Am I at risk of overdriving the piezos using this setup? I should also mention that I did use a 56r 2 watt resistor in series as well. Any input on this would be greatly appreciated. The piezos I used were clones of the ksn1016 but actually did not sound bad. (Don't know how long they'll last). I recently bought 6 old stock motorola ksn1016's and I want to make 2 arrays of 3. What would be the ideal circuit using this coupling transformer/zoebel circuit. Thank you for all the great information on this forum!!

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RE: Using piezos with transformer

djk

16:39:08 11/22/12

RE: Using piezos with transformer

Evad.5150

10:26:44 12/27/12

RE: Using piezos with transformer

06:45:34 12/03/12

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RE: Using piezos with transformer

djk

16:39:08 11/22/12

RE: Using piezos with transformer

Evad.5150

10:26:44 12/27/12

RE: Using piezos with transformer

06:45:34 12/03/12

RE: Using piezos with transformer

freddyi

13:15:10 11/24/12

RE: Using piezos with transformer

djk

01:01:52 11/25/12

RE: Using piezos with transformer

freddyi

07:07:39 11/25/12

RE: Using piezos with transformer

djk

02:55:57 11/26/12

RE: Using piezos with transformer

19:14:00 11/26/12

RE: Using piezos with transformer

fstein

14:41:17 11/22/12

Off-Topic ?

djk

15:11:04 11/22/12

RE: Using piezos with transformer, posted on November 22, 2012 at 14:41:17
fstein Audiophile Posts: 2994 Location: fstein Joined: May 18, 2006	When one of the British mags reviewed this speaker (?last year) they added a SUBWOOFER!

Off-Topic ?, posted on November 22, 2012 at 15:11:04
djk Manufacturer Posts: 6135 Joined: June 17, 2000	" 2 way models without a tweeter." They did not review this model.

RE: Using piezos with transformer, posted on November 22, 2012 at 16:39:08

djk
Manufacturer

Posts: 6135
Joined: June 17, 2000

The KSN1016A behaves like a lossey 0.13�F capacitor, and the response actually rises above 16Khz or so.

Use a 75Ω resistor in series with each tweeter. This does several things. It damps the resonance of the tweeter by lowering the Q a bit. It rolls off the energy where the response of the tweeter starts to rise. It makes the load more amplifier friendly.

Three of the piezo and resistor combos in parallel will be about 50Ω around 16Khz, so hook them up to the 10W (62Ω) tap on the 25V line transformer.

I would try a zobel of around 6.8Ω and 100�H across the 8Ω tap of the transformer. The 6.8Ω and 75Ω are standard E24 (5%) resistor values.

This should get you close to an 8Ω load for your crossover network. If I need a 4Khz network I generally go 18dB, 3.3�F + 10�F + 0.25mH. If I need a 7Khz network I generally go 12dB, 2.2�F + 0.25mH.

A dual use network may be constructed with a SPDT switch and a 0.25mH + 1�F + 2.2�F + 10�F. The switch shorts out the 10�F or parallels the 2.2�F and the 1�F.

An RCA 'Ubangi' with a single KSN1016A crossed at 4Khz on the 2.5W tap. It plays flat beyond 16Khz and can keep up with the 16Ω 110dB/W RCA cabinets.

I have long used three and five tweeter concave arrays for PA use, only one need be used for home hi-fi.

RE: Using piezos with transformer, posted on November 24, 2012 at 13:15:10
freddyi Audiophile Posts: 3852 Joined: December 6, 2001	assume Zoebel goes across transformer primary (? - am sick w. usual vertigo - messes with everything) great setup Karlson Evangelist

RE: Using piezos with transformer, posted on November 25, 2012 at 01:01:52

djk
Manufacturer

Posts: 6135
Joined: June 17, 2000

"assume Zoebel goes across transformer primary?"

You got it in one Fred!

"great setup "

I thought it was a slick trick and kind of versatile too.

" am sick w. usual vertigo - messes with everything"

Been there, didn't like it, didn't get a tee-shirt either. Mine turned out to be infected glands on the underside of my jaw, a reaction to cigarette smoke! They had me on steroid inhalers for a while, worthless. Walked around like I was drunk, couldn't drive, etc.

RE: Using piezos with transformer, posted on November 25, 2012 at 07:07:39

freddyi
Audiophile

Posts: 3852
Joined: December 6, 2001

I've done nearly 40 years of vertigo - getting worse and stay queasy most of the year - can't figure out why maybe 10 days per year are pretty good - could probably ride a motorcycle on those days - constant gastric reflux into sinus cavities doesn't help. Once tried a neti pot -lost all balance, vomited for over an hour non-stop - lucky at that time to get a ride to ER where perceived as a drug addict having a fit.

what switches do you recommend? - looked at a cheap modern knife switch which has binding posts on Ebay but figure it would put too much steel in the path.
Karlson Evangelist

RE: Using piezos with transformer, posted on November 26, 2012 at 02:55:57
djk Manufacturer Posts: 6135 Joined: June 17, 2000	I actually use brass pins pounded into the board the network is built on. A jumper is soldered to the appropriate pins.

RE: Using piezos with transformer, posted on November 26, 2012 at 19:14:00

Evad5150

Thank you for all the great information!!!! When I used to tinker with building speakers years ago I bought many original motorola piezos from radio shack. I was blown away when i recently used the transformer circuit with a ksn1016 clone in 2 pairs of klipsch heresies!! I never knew piezos could sound so crisp and clear. Thank you all for the crossover tips. When I assemble my 3 piezo arrays I will definitely use the dual circuit. What a great idea. I have one more pair of 2 way heresies (1984 thsr models). I stripped off the factory black lacquer to reveal zebra wood veneer on one and oak on the other. The 4 I sold with the piezos were walnut. Now I can't decide if I want to install piezos in the pair I kept or get the crites ct125's. I just wish they were both zebra wood. Now I have to reveneer if I want them to match. Decisions decisions!!

RE: Using piezos with transformer, posted on December 3, 2012 at 06:45:34
Evad5150	eBay has some nos TRW 2 watt 75 ohm wire wound resistors for a good price. Should or can I use these instead of carbon or will they put some unwanted inductance in there??

RE: Using piezos with transformer, posted on December 27, 2012 at 10:26:44

Evad.5150
Audiophile

Posts: 7
Joined: November 19, 2012

DJK and freddyi: Using all your great info, I just finished building 2 - 3 ksn1016 arrays using your recommended zoebel values and the dual crossover setup. What an awesome setup !!!! I love the 4khz setting. It brings out vocals and clarity superbly!!!!~ not to mention that "CRACK" of the snare drum and cymbals ! I absolutely love it. I always needed to keep my treble setting all the way up, now I need to dial it back, a lot! should have installed an l-pad but i couldn't wait any longer to hear these. As you stated in a previous post, "all you need is one ksn1016 for home use" so true! I couldnt bring myself to cutting these 1016's to fit in my heresies. these are the ones with the nice beveled flanges, so I figured I would tinker around and build the arrays since I had 6 of them. I recently bought 4 more nos motorola ksn1016's with the flat flanges. I will use these to trim up and install in my heresies. Just out of curiosity, djk, what components did you use for your zoebel and crossover for the 1016 you used with the Ubangi?? I will probably end up selling these arrays because I wont need them so if anyone is interested, contact me. I have over $100 invested in the pair. I'm not looking to make any money, just want to try to break even. All 6 ksn1016's are brand new nos. they've only been slightly used during the building procees. I'll attatch some pictures. The enclosures are made from cedar. The zoebel consists of a 6.8 ohm 25w worewound resistor from radio shack and a Dale 100uh inductor (.090 dcr) the crossover components are from parts express (.25mh inductor, 10uf, 2.2uf and 1.0uf capacitors and spdt switches for crossover selection), 75ohm resistors are Allen Bradley 2watt carbon (not cheap) and the transformers from ebay : http://www.ebay.com/itm/25-Volt-10-Watt-Line-Matching-Transformer-LM25-10-/310289992031?pt=BI_Circuit_Breakers_Transformers&hash=item483eb9895f

Up until a few months ago I would have never believed that piezos could rival much more expensive compression drivers. Anyone who doesn't believe so is WRONG!! Using the proper components tames the harshness and lets the music through with power and clarity!!! after buliding these, I decided that I will use ksn1016s in my heresies instead of the "correct" replacement tweeter. I am that convinced of their ability!! Below are some links to photos and forums that I used to gain information to build these.

http://i268.photobucket.com/albums/jj27/evad5150/motorola%20ksn1016%20piezo%20arrays/iphone387.jpg

http://i268.photobucket.com/albums/jj27/evad5150/motorola%20ksn1016%20piezo%20arrays/iphone388.jpg

http://i268.photobucket.com/albums/jj27/evad5150/motorola%20ksn1016%20piezo%20arrays/iphone389.jpg

http://i268.photobucket.com/albums/jj27/evad5150/motorola%20ksn1016%20piezo%20arrays/iphone390.jpg

http://i268.photobucket.com/albums/jj27/evad5150/motorola%20ksn1016%20piezo%20arrays/iphone356.jpg

http://www.audioasylum.com/forums/hug/messages/16/164125.html

http://db.audioasylum.com/mhtml/m.html?forum=hug&n=29348&highlight=piezo+djk&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fauthor%3DTom%2520C%26user_id%3D7433%26forum%3DALL%26sortRank%3DNone%26sort%3Ddate%26sortOrder%3DDESC

http://db.audioasylum.com/mhtml/m.html?forum=hug&n=27886&highlight=piezo+djk&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fauthor%3DTom%2520C%26user_id%3D7433%26forum%3DALL%26sortRank%3DNone%26sort%3Ddate%26sortOrder%3DDESC

http://db.audioasylum.com/mhtml/m.html?forum=hug&n=164125&highlight=piezo+djk&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fauthor%3DTom%2520C%26user_id%3D7433%26forum%3DALL%26sortRank%3DNone%26sort%3Ddate%26sortOrder%3DDESC

DJK is absolutely the best source for "correct" information on the proper usage of piezo tweeters. I recommend looking up his posts. Thanks again DJK.

High Efficiency Speaker Asylum

Using piezos with transformer

24.39.245.6