RoyC
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Posts posted by RoyC
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Hmmm, I'm sure it will be interesting, but it is hard to see how it will be relevant to the 4x. Impedance is only one parameter. You are proposing using it with a different woofer, different cabinet, different crossover...and conclusions reached based on your listening impressions?
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44 minutes ago, ReliaBill Engineer said:
Just got these in. Hopefully I’ll have time tonight to make a few changes. I bought 2. One will remain unmolested.
4 or 8 ohm. Are you installing them in 4x's? What kind of changes do you have in mind?
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5 hours ago, meta_noia_fot said:
Currently I have OK seals on the woofers. That’s after one layer of Roy’s sealant on the woofer dust cap and 2.5 layers on the surrounds (2 full coats and a touch up of spots that looked thin). When pushing in and releasing the woofer, I get a second or so before the woofer is back in its original position.
As for the midrange drivers, what’s the best way to tell they are sealed? Maybe they’re fine as is and I’m overthinking it.
Speaking of the midrange enclosures, those are held on with four screws on the front of the baffle, unfortunately right where each midrange needs to seal. So more than not, each of those screw holes ended up with a small channel into the enclosure.
George
Hi George,
Based on your post, I'm sure you have plenty of sealant on the woofer and mid surrounds. As long as your woofer cones are returning more slowly. There is such a thing as applying too much sealant.
The mids' surrounds only need one light application of sealant, which is much less necessary than the supplemental treatment of the woofer surrounds. It is more important to keep the mids' surrounds compliant. The most critical aspect of installing the mids is sealing their sub-enclosure from the rest of the cabinet.
The mids originally had white foam gaskets in the space you filled with putty. There should be some kind of gasket material under the entire mounting flanges of all the drivers.
Roy
PS Great photos, Kent.
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On 3/12/2024 at 10:28 AM, JKent said:
Not sure about the dust cap. How does the woofer do with a push test? If it springs back maybe try a little white glue around the cap. If it still springs back use some of Roy's goo on the surrounds.
Regarding the caps, I hope someone with more expertise chimes in but I don't see a problem. What are the implications for ESR? I dunno. I do know, from working on Snells, that Peter Snell was an advocate of "bundling" caps, so you're in good company.
Kent
The dust cap is original.
I agree with Kent. It all looks good from here, including that fancypants capacitor arrangement! 🙂 Not sure of an any upside, but I'm certain they will do the job very well.
Roy
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20 hours ago, DavidR said:
Attached is a picture of my AR91 woofer that shows the masonite ring.
Good photo...I don't believe I have ever seen an original AR-9 woofer without the masonite ring.
OP probably should post a photo if he is in doubt as to whether he has original or Tonegen replacements(s). It is important not to damage the ring if it is present.
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15 hours ago, ReliaBill Engineer said:
The 4X was not AR’s flagship model. Not by a long stretch.
The below tweeter, while not paper, is a very good design for a cone tweeter. It’s actually smooth and well behaved.
So you have experience using this tweeter in the 4x? What crossover and cabinet changes did you make to accommodate this tweeter?
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23 hours ago, ReliaBill Engineer said:
That’s why AR used dome tweeters in its upper line speakers, so the outer edge IS the driven part where the VC is mounted. The PRT has an outer edge restrained and a center free to move by the VC.
First of all, we are talking about subjective impressions of a 4x replacement tweeter based on feedback from users, not your opinion of the original AR tweeter. It should be noted that the replacement PRT type tweeter does not have the same construction as the original 4x tweeter...which has a more compliant suspension. The PRT replacement is not as capable in the mid frequencies primarily due to excursion differences. Despite this, a great many users are satisfied with it. It is the difference between this tweeter and the original AR-4x tweeter under discussion, not any flaws (or "distortion") associated with the overall use of this type of tweeter.
Secondly, your conjecture as to why AR used dome tweeters is not accurate. It is not uncommon for speaker manufacturers to successfully use cone tweeters in 2-way designs. AR used dome tweeters for the highest frequencies in 3-way models to enhance dispersion and power handling, not because their cone drivers were distorting. Dome tweeters were used only in their more robust 3-way designs, never in their 2-way models. The cone tweeter used in 2-way models such as the AR-6, 7, 8, and 18 is still highly regarded.
Obviously any driver used outside of its design parameters can "distort". In the end, we are probably talking about the same thing. We just have a different definition of "distortion".
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7 hours ago, ReliaBill Engineer said:
Inherent frequency response and behavior *is* the distortion, if it’s in the pass band. A crossover can limit distortion if it occurs below or above the XO frequencies.Even with the crossover, there shouldn’t be distortion. Rather, it should have a smooth roll off at both ends of the FR. And an inherently smooth pass band.
I disagree. No speaker system (or individual driver) has ruler flat frequency response...so are those departures considered to be "distortion"? The 4x replacement tweeter referred to as "harsh" by some people has been found to be satisfactory others. Earlier in this thread a forum member stated "I actually like the Parts Express replacements". Are you going to tell him he prefers "distortion"? If so, based on what?
"Distortion" is usually considered to be something that should not be present such as noise, static, rattles. clipping, etc. I think you are actually referring to frequency response and tonal balance, not distortion. The crossover integrates presumably properly functioning drivers to produce a desired response. There will always be variations and preferences on the part of the designer and the listener.
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7 hours ago, baffled_loudspeaker said:
The seller used M-3035 adhesive. Do you know what could dilute it?
Also, you're sure there's a masonite ring under the outer edge of the surround on the 12" AR-9 woofer? It's not just bonded to the metal basket?
Thanks again.
If it is Simply Speakers adhesive, the primary solvent is toluene.
12 inch woofers manufactured by Tonegen had a raised area stamped into the woofer basket instead of the masonite ring.
Roy
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8 hours ago, tourmax said:
Any recommendation on a min wattage for resistors in the tweeter path? 5W sound appropriate or can/should I got a bit lower?
5w would be the minimum. 10w or higher would be better.
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21 hours ago, tourmax said:
Hmmm, the tweeters I just ordered are 8 ohm but I’m reading various threads on the forum that 4x’s are anywhere between 4 and 6 ohms.
Did I order the wrong impedance tweeters and if I did, can I bring them closer to the proper values with some resitors?
As I mentioned above, the 4 ohm version is a better bet.
If the mid range seems too forward, you can experiment by placing parallel resistance with the higher impedance replacement tweeter, starting at 8 ohms.
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It's not unusual for some old "vintage" amps to send very destructive DC to speakers when failing (at any volume level). It can't hurt to use a basic 2 to 3 amp fast blow fuse in an inline fuse holder as some protection insurance with these systems. https://www.parts-express.com/In-line-AGC-Fuse-Holder-070-609?quantity=1
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3 hours ago, ReliaBill Engineer said:
Looking at the suggested wiring of the fuses, it doesn’t protect the tweeters by themselves. The fuse is seeing the total current fed to the loudspeaker. So is it going to protect the tweeter? Kind of doubtful. It’s a crapshoot whether enough current still passes to the tweeter to blow its VC before the fuse blows.
Agreed.
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1 hour ago, ReliaBill Engineer said:
I don’t think a fuse would have protected your tweeters from the sudden *thump* of a mic input.Interestingly, back in the shop we also saw more fried woofer voice coils than tweeter voice coils...which had been protected by its crossover components.
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1 hour ago, ReliaBill Engineer said:
Harshness comes from distortion.
Not necessarily. In this case it probably has more to do with its inherent frequency response and behavior with the existing crossover.
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2 hours ago, JKent said:
That's a standard phenolic ring tweeter (PRT). Parts Express also sells them, for a lower price.
the classic PRT to be the best, albeit not perfect replacement.
This tweeter is certainly not a perfect replacement, especially when used in a pair next to an original. Unfortunately, there are really no other "drop-in" options. There was some experimentation with crossover changes for this tweeter mentioned in the forum quite a few years ago, but I'm not aware of anyone who implemented any of the suggestions.
Midwest is selling a 4 ohm version as well as the 8 ohm version sold by PE and Vintage_AR, and I'm more inclined to recommend that one if given a choice. https://www.midwestspeakerrepair.com/product/mw-audio-mt-4107-phenolic-cone-tweeter-2/
(Btw, VAR's addition of the sealant is just an attempt to calm the harsher nature of this tweeter...with very limited success.)
Roy
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2 hours ago, Aadams said:
LST fuse condition is a big deal. The fuses degrade over time and can cause quirky behavior. You could temporarily bypass the fuses and gently test the system.
I strongly agree with Aadams.
Andre, You are over-thinking the possible issue at the moment. After verifying the problem is confined to the cabinet (which you have done), the very first thing to do is to simply place a jumper across the fuse. It will take you just a few minutes to do this. When the LST/LST-2 fuse becomes worn out it can pass a weak signal causing exactly what you describe. I have run across this several times. The issue is unique to these models.
Roy
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1 hour ago, powerglide said:
I could go over my notes from last time, but for the coils which would be best an 18 or 21 AWG?
18ga would be more consistent with the other AR coils, but if the smaller gauge is all you have on hand it won't hurt anything.
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27 minutes ago, powerglide said:
do I need the resistor? It was my understanding they were for the L-pads to function correctly (remember the improved has toggles)
Yup...I did mention it above. Remove the resistor regardless of your approach.
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8 hours ago, powerglide said:
Thanks Roy, but I think you misunderstood my question, could I put these tweeters into the AR3a improved as is or would I need to change the modification made for the ax2’s ?
I have been running these in my ax2’s for the past couple of years.
Oops, sorry...I had 2ax on the brain. 🙄
There is a .1mh coil for the tweeter in the Improved crossover, so...
-You could replace the coil on the back of your HiVi tweeter with a .1mh coil, which would place it in parallel with the existing crossover coil.
-or disconnect the internal tweeter coil and leave the one mounted on your tweeter as is.
In both cases remove the resistor.
The goal is to reduce the parallel coil value for use with the HiVi tweeter.
Roy
PS Perhaps an easy way to start would be to simply disconnect one of the coil leads (and resistor) from your HiVi tweeters just to see how it sounds with the original .1mh crossover coil.
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Install it as shown in your photo just as you would the 3a. Connect your tweeter's red lead to the crossover's yellow wire, and black to black. Some people have played around with polarity and/or have reduced the 2ax's original 4uf capacitor to 3uf, but don't change anything until you try it as is.
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Remove the metal screen and try it again, as a loose screen can sometimes cause this issue. Of course, also inspect the cone for any obvious problems.
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On 2/11/2024 at 7:52 AM, script56 said:
I am missing bolt that holds the coil onto back of cabinet. Does anyone have spare? It may be used in other ar products besides the ar3-st. It is screw with riveted flat back. Circled in red in attached pic.
If you haven't already done so, remove the clip and tap the rivet/shaft out from the inside. You can easily replace it with a brass or stainless steel screw, nut, and washer to replace the entire spring clip arrangement. (Use brass or stainless hardware because it is non-magnetic.)
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The higher impedance of the 3/4" dome 2ax tweeter makes it less sensitive than the 3a version. It will also behave differently with the AR-3a crossover.
Blown AR4x tweeters and a repair attempt…
in Acoustic Research
Posted
Suitable as a replacement in the 4x, not pair of Polks. No relevance.