I'm afraid it has happened?

[JKent]

14 minutes ago, Phxjohn said:

How does my 'PhxJohn' get put on some of these posts ? I never use profanity on audio forums. 

Apparently when you quoted potty-mouth Frank you put your reply within the quote box, then you were quoted.... it's a technicality. We won't hold it against you 

[RoyC]

On 11/15/2017 at 2:34 AM, harry398 said:

thanks for sharing your experience with that tweeter.

I have a question........how can someone determine how much coil is needed when swapping in a tweeter.

example....If someone wanted to drop in a AR9 tweeter into a ar3a cabinet.....how much coil is needed?      or is it trial and error with sound.

 

 

Fortunately we know the coil and cap values AR used with their later tweeters in various models, which can serve as starting points. For example, the AR-3a Limited crossover used the AR-11/9 type of tweeter with a 4uf cap and .16mh coil, along with 8 ohm L-pads. That is a valid starting point, beyond which (motivation and resource dependent) tweaking and response measurements could be conducted. Keep in mind, knowledge of how crossover components affect response is extremely helpful and saves lots of time.

Roy

[Phxjohn]

2 hours ago, JKent said:

Apparently when you quoted potty-mouth Frank you put your reply within the quote box, then you were quoted.... it's a technicality. We won't hold it against you 

Thanks. I have not been on here in a long time. I was involved and still am with the resurrection of the GE VR 1000 phono cartridges. I finally found some good styli for the cartridges and bought out all remaining stock. All 108 EVG from Russell Industries. 

[Pete B]

I measured an AR-11 tweeter back in 2005, it would be great to know Fs and the Q's for the 

new tweeter.

Some measurements on an AR-11 tweeter (200011-1) are given below. Measured with LAUD.

The input impedance curve showed a double bump which is common with chambered tweeters, has anyone had the dome off to see if the center pole is vented into the rear? The impedance peaks were heavily damped due to the ferro fluid. The lower frequency peak at 1360 Hz was 5.26 ohms, the minimum in between at 1865 Hz was 4.65 ohms, and the upper peak at 2427 Hz was 5.30 ohms. The tweeter was 4.0 ohms in the passband at 5 kHz.

Here are the basic measurements based on only the input impedance, and assuming that the upper peak is the fundamental resonance:

Fs = 2427 Hz

Re = 3.55

Qe = 2.76

Qm = 1.57

Qt = 1.00

[RoyC]

3 hours ago, Pete B said:

Some measurements on an AR-11 tweeter (200011-1) are given below. Measured with LAUD.

The input impedance curve showed a double bump which is common with chambered tweeters, has anyone had the dome off to see if the center pole is vented into the rear?

I have had a few of these apart over the years, Pete. The magnet is not vented. In fact there is a wooden dome glued to the pole piece under the fabric dome, leaving only a very small space behind it.

Roy

[tysontom]

Many of the new-style (cloth) AR-10/AR-11 3/4-inch tweeters used the same magnet assembly and top plate as the original AR-3a tweeter, thus having three slots around the pole piece that were used for the foam suspension in the 3a tweeter.  Since no foam was used in the AR-11 dome, air can escape from under the dome into the pole-piece/magnet cavity below the dome.  This would in essence increase the volume under the dome.

--Tom

[fedeleluigi]

On 11/28/2017 at 2:04 AM, tysontom said:

Many of the new-style (cloth) AR-10/AR-11 3/4-inch tweeters used the same magnet assembly and top plate as the original AR-3a tweeter, thus having three slots around the pole piece that were used for the foam suspension in the 3a tweeter.  Since no foam was used in the AR-11 dome, air can escape from under the dome into the pole-piece/magnet cavity below the dome.  This would in essence increase the volume under the dome.

--Tom

Hello Tom

 

Pete said the tweeter he tested had ferrofluid. If the ferrofluid was still in place in the magnet gap , it sealed it and consequently the space behind the dome. So, in the 200011-1  tweeters with ferrofluid the air behind the dome can't escape from under the dome into the pole-piece/magnet cavity. In other words the air is trapped under the dome and suspension.  On the contrary, as regards the early 200011-1 tweeters the air can move freely because they don't have ferrofluid sealing their magnet gap.

 

Luigi

[Pete B]

On 11/26/2017 at 10:02 PM, RoyC said:

I have had a few of these apart over the years, Pete. The magnet is not vented. In fact there is a wooden dome glued to the pole piece under the fabric dome, leaving only a very small space behind it.

Roy

Thanks Roy, yes I also had the other one of the pair apart some time after I made

those measurements and saw those features.

[Pete B]

On 11/27/2017 at 8:04 PM, tysontom said:

Many of the new-style (cloth) AR-10/AR-11 3/4-inch tweeters used the same magnet assembly and top plate as the original AR-3a tweeter, thus having three slots around the pole piece that were used for the foam suspension in the 3a tweeter.  Since no foam was used in the AR-11 dome, air can escape from under the dome into the pole-piece/magnet cavity below the dome.  This would in essence increase the volume under the dome.

--Tom

I agree Tom, the upper chamber under the dome is vented, through the three slots 

to the air chamber where the back of the voice coil is.

[tysontom]

On further thought, it occurs to me that the slots are on the outside of the dome/voice coil, and thus may not necessarily affect air movement inside the dome.  I also suspect that the early domes before Ferrofluid might be less affected by the space under dome than later ones with fluid.  The gap would allow a small amount of air to pass inside the voice coil past the pole piece.  With Ferrofluid (on both sides of the coil), air would be trapped under the dome. 

[ctjetta]

OK, so what are the chances the Midwest replacement AR tweeter in the 8 ohm version would be a suitable replacement for the AR5?

Larry/vintage-ar just said it was not an option and not carried by him. That already implies I'm swimming upstream here, but I'm hoping for a little enlightenment, if possible.

[RoyC]

18 hours ago, ctjetta said:

OK, so what are the chances the Midwest replacement AR tweeter in the 8 ohm version would be a suitable replacement for the AR5?

Larry/vintage-ar just said it was not an option and not carried by him. That already implies I'm swimming upstream here, but I'm hoping for a little enlightenment, if possible.

The Midwest tweeter is as viable as the HiVi replacement tweeter/coil combo sold by Larry if it is used with a parallel coil. Unfortunately, it is only available at a shipped retail price of around $80 each through Midwest, so there is no profit to be made for Larry to re-sell it. With that said, it is very well constructed, fits the cabinet hole perfectly, and it is worthy of experimentation if cost is not an issue.

I will be working in Larry's shop on Wednesday, and will take a look at his inventory. Last I looked he had very few AR-5 drivers.

Roy

[Pete B]

$69.95 4 or 8 ohm:   https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/

[ctjetta]

 I realize that it makes little financial sense (go figure), as opposed to the HiVi replacement tweeter/coil combo, but the Midwest tweeter really appeals to me for my AR5s. Is there any thought as to a ballpark value for the coil that would be required?

Now, if I understand correctly, the HiVi replacement tweeter/coil combo (different coil value?), will work in my AR4(x,xa) cabinets that also need new drivers. But, one project at a time.

[RoyC]

14 hours ago, Pete B said:

$69.95 4 or 8 ohm:   https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/

+ $11.75 shipping (to NY).

[RoyC]

5 hours ago, ctjetta said:

 I realize that it makes little financial sense (go figure), as opposed to the HiVi replacement tweeter/coil combo, but the Midwest tweeter really appeals to me for my AR5s. Is there any thought as to a ballpark value for the coil that would be required?

Now, if I understand correctly, the HiVi replacement tweeter/coil combo (different coil value?), will work in my AR4(x,xa) cabinets that also need new drivers. But, one project at a time.

The HiVi replacement is not used in the AR-4 series.

I agree, the Midwest tweeter is an attractive option.  Based on some experimentation with the similar AR-12 tweeter, a coil of around .07mh would be a reasonable starting place.

Roy

[ctjetta]

Thank you for the help, RoyC.

The AR4 tweeters search will need more thought.

[Pete B]

I started a thread here about mods for the AR-4 speakerdave a real pro did a crossover mod,

and Zilch found a Tang Band I suppose worked well.  Do those interest you?

[lARrybody]

A lot of people use these as AR4X replacement tweeters. Had a set with one bad tweeter so I bought these, but eventually found a original which I used instead. Don't know how they perform, but they have good reviews.

https://www.parts-express.com/grs-prt-8-phenolic-ring-tweeter-replacement-for-ar-4x-cts-marantz-and-more-8-ohm--270-252

 

I will eventually find a project to use them on.

[JKent]

I've used them. See this post: 

As described in the thread, I found them a bit harsh but Roy recommended reducing the cap value to 10uF. Easy to do in my case, since i had used paralleled 10uF caps to make the 20uF, so... snip snip. After the switch from 20 to 10uF the speakers sounded good to me.

-Kent

[Pete B]

Did anyone save .frd and .zma files for the AR-4 woofer from Zilch's thread?

[Glitch]

15 hours ago, larrybody said:

A lot of people use these as AR4X replacement tweeters. Had a set with one bad tweeter so I bought these, but eventually found a original which I used instead. Don't know how they perform, but they have good reviews.

I bought a pair of the GRS PRT-8 mentioned above as part of a restoration project of a 70's era pair of speakers.  One of the speakers had the factory original CTS tweeter.  The other had a slightly different CTS tweeter that was replaced under warranty.  There was enough of a mismatch between the two tweeters to motivate me to replace them with a new "matched pair".  Unfortunately, I was not happy with the sound quality of the PRT-8.  The original CTS phenolics tended to be a bit squawky.  The PRT-8 is much more so.  I found the PRT-8 to be harsher than every other of the vintage/original phenolic tweeters that I own.  I can see why the PRT-8 gets good reviews.  It is certainly a good match visually.  It also exhibits the sonic character that most people associate with the original CTS phenolic (perhaps to a fault).  I might have been happy with the PRT-8 if I had not done A/B testing against the originals.  I also tried the RT-6 phenolic that PE sells.  The PRT-8 is a better driver than the RT-6.

[JKent]

6 hours ago, Glitch said:

I also tried the RT-6 phenolic that PE sells.  The PRT-8 is a better driver than the RT-6.

In what way(s)? I have a pair of those RT-6's in my parts box but have not tried them. Reviews on the PE site seem positive.

The frequency response is 6,000-20,000 so not suitable for the AR-4x.

-Kent

[RoyC]

On 6/5/2018 at 2:53 PM, ctjetta said:

Thank you for the help, RoyC.

The AR4 tweeters search will need more thought.

ctjetta,

As of today, Larry may have one AR-5 mid with a broken faceplate. That seems to be it for the foreseeable future.

Reply to the PM I sent you a couple of days ago if you would like to discuss other options.

Roy

[Glitch]

22 hours ago, JKent said:

In what way(s)? I have a pair of those RT-6's in my parts box but have not tried them. Reviews on the PE site seem positive.

It has been some time since I did the phenolic tweeter comparisons.  My recollection of the RT-6 is that it didn't do anything particularly bad.  However, it didn't do anything remarkably good.  I recall that it didn't seem to reach the higher frequencies as well as the PRT-8.  Nor did it provide the classic CTS phenolic tweeter sound signature as well.  My basic assumption is that the reason that people are buying the reproduction phenolics is that they are trying to reproduce the sound signature of a particular classic speaker.  The PRT-8 also seemed to be built better with heavier metal for the basket and a bigger magnet.  I liked the integrated grill of the RT-6 since this mimics the style of the drivers I was trying to replace.  Unfortunately, the sound quality wasn't what I was looking for.  I ended up buying a used pair of vintage/original CTS phenolics to complete the project.