AR 2ax Assessment

[Beltway]

Greetings all.

I recently picked up a pair of first gen. 2ax's (alnico magnet/linen surround woofer and dark red phenolic tweet) in beautiful condition. Many thanks to all the contributors on this site for (inadvertently) helping me select which model to get, as I am very pleased with the sound. After reading MANY posts on this and other sites, I felt confident enough to perform a minor recondition by recapping with Daytons and working on the pots. I am using somewhat modern but mellow gear (AES AE3 tube pre/Bedini 150/150 mkII amp) and love the laid back, lush sound. As I move forward with the never-ending quest for improvement, I have a few questions:

When I recapped, I also eliminated the tweet pots. No resistor was installed to attenuate the high frequencies; the tweets are running wide open. It sounds great, but I'd like to hear what the experts think about it.

I don't need to adjust the mid level and have been thinking about eliminating those pots as well. My plan would be to install Miller resistors in place of the pots, shunting about 1/2 an ohm to approximate the "sweet spot". Any thoughts on this? I'm a noob when it comes to this stuff, so any input is welcome.

I love the sound, but definitely see why people don't think these are great rock speakers. They simply refuse to be rude! We mostly listen to acoustic/vocals, so no big worry, but listening to rock for the first time made me wonder if the tweeters had degraded over time. Are the old phenolic tweets subject to degradation? If so, can anything be done to help them out?

Thanks very much for your input!

Cheers.

[Beltway]

Ok. Further research has yielded the following impressions:

The phenolic tweet does not have the dispersion or efficiency of the later 3/4" unit and is thus not so deeply loved. It does, however, have excellent transient response and seems to be more resistant to deterioration. While both tweets are suspended with urethane foam, the butyl coating on the older may help slow down decay. The two ways it most commonly fails is in the separation of the aluminum voice coil and by "popping" the dome due to the pressure of the compacted fiberglass dampening material. Barring that, it is pretty hard to hurt these units. Please correct me if I am wrong.

I can honestly say that they sound fantastic to my ears. Perhaps a bit rolled off, but that seems to be the price one pays for fatigue-free listening.

I haven't been able to find solid answers to my other questions re: pot elimination. Any input would be most appreciated, even if it is simply pointing me in the direction of a post that already covered my question. I'm still searching the archives.

Thanks again for any help y'all can offer.

Cheers.

[Carlspeak]

You'll most likely get some advice from onplane who's an advocate of pot bypassing and bi-amping. Those are indeed mods and probably, that discussion if held publically, should be moved to the mods and tweaks section.

[RoyC]

I can honestly say that they sound fantastic to my ears. Perhaps a bit rolled off, but that seems to be the price one pays for fatigue-free listening.

I haven't been able to find solid answers to my other questions re: pot elimination. Any input would be most appreciated, even if it is simply pointing me in the direction of a post that already covered my question. I'm still searching the archives.

Thanks again for any help y'all can offer.

Cheers.

You are already experiencing one of the primary attractions to the old ARs ("fatigue-free listening")...so the following is only offered in answer to your question about "by-passing" the pots.

If you are inclined to experiment, replacing the tweeter pot with a common 8 ohm l-pad will coax a bit more output from the driver and still give you the ability to adjust the level. Be aware, however, that a full on l-pad has the same effect as completely eliminating the old pot from the circuit, so care must be taken at high volume levels. Using these with just the tweeters will provide an adequate high frequency boost for many folks.

(It should be noted that AR parts suppliers, such as AB Tech and Vintage AR, are selling ordinary 8 ohm l-pads as AR level control replacements. AB Tech, inappropriately, shows a photo of an l-pad labeled as an AR "potentiometer". The same item is available from Parts Express or Madisound for less than half the price.)

If you simply want to permanently set a pot to the fully "increased" pot setting, cut the "B" terminal pot wire and attach it to the wire connected to the #1 pot terminal, so both are now connected to the #1 pot terminal...OR cut all pot wires and re-connect the + and - wires to each driver with a 15 to 16 ohm shunt resistor between them.

Carl, I posted this here because this question comes up so often, but a separate thread in the mods and tweaks section on various approaches to eliminating the dreaded pots is not a bad idea :-).

Roy

[Beltway]

Thanks very much for your replies, Carl and Roy.

I understand your point re: the "mods and tweaks" forum, but there has been so much discussion about caps and pots on this forum I feel it isn't totally out of place to continue. If the moderators feel otherwise I won't object, but there is so much more traffic here I'd prefer it stay here. Most importantly, I am only trying to get these speakers to sound as close to original as possible. I love their sound, but don't need to adjust the levels via pots or lpads so would like to eliminate them. I use a computer playing lossless music files with an outboard DAC as my source and can digitally tweak the levels all I want.

Anywho, I'm a bit confused by Roy's post. Why do I need a resistor or l-pad for the tweet? Won't running it straight from the capacitor give me maximum high frequency boost? Am I putting the tweets in danger by not having a resistor? They sound great to my ears at this point, but I don't want to damage anything.

As for the mid, I wanted to set the level permanently at a point just shy of full-on. my thought was to shunt only about .5 ohm. That is, I'd use: (20ohm)(68ohm) or (120ohm)(18ohm) to positive terminal, both values soldered together in parallel to equal 15.5 ohms.

AND

(.5ohm) (to negative)

That should bring me to a point very close to the "sweet spot" on the mid pots. I think.

Right?

Thanks again for the help!!

Cheers.

[Beltway]

Ooops.

I said the exact wrong thing re: the resistors.

15 ohm across from pos. to neg.

.5 ohm parallel with pos. to attenuate mid frequencies a tad.

Again, thanks in advance for your input.

[RoyC]

Anywho, I'm a bit confused by Roy's post. Why do I need a resistor or l-pad for the tweet? Won't running it straight from the capacitor give me maximum high frequency boost? Am I putting the tweets in danger by not having a resistor? They sound great to my ears at this point, but I don't want to damage anything.

I was just providing some options. The l-pad was suggested only if you still want a level control that could give you a completely "by-passed" (maximum boost) setting, as well as other settings. Yes, maximum high frequency boost is also provided by going "straight from the capacitor" with no control in the signal path.

An important thing to consider with this approach, however, is that the tweeters will see more power than they do with the old pots in the circuit. Eliminating the pots' shunt resistance will raise the impedance, therefore lowering the crossover point slightly, which means the tweeter sees more power at some lower frequencies as well. It can change the character of the sound somewhat, and endanger the tweeters to a higher degree at high volume levels. If the speakers really do sound great as they are, then maintaining 15 to 16 ohm shunt resistance (provided by a resistor OR a rewired pot) is a safer approach. This will maintain the original crossover point and fix the tweeter at the maximum pot setting, while still offering some protection.

Your plan for the mid sounds fine, but you may need to attenuate it a bit more if you completely by-pass the tweeter pots and eliminate the corresponding shunt resistance. You may find something like 2.5 ohms in series and 13 ohms in parallel to be more optimal. (As long as the series and parallel resistors add up to 15 to 16 ohms you will emulate a pot setting.) Remember, you would be lowering the tweeters' response further into the midrange if you completely by-pass their pots.

Roy

[Beltway]

Thank you VERY much, Roy, for that clear explanation.

It sounds like my best bet is to insert 15 ohms of resistance in parallel for the tweeter, as I really do not want to stress it by lowering the crossover.

With that done, do you think I'm ok going back to the .5 ohm resistor in series and 15 ohm in parallel for the mid? With the tweet crossover point set back to normal, I'd think lowering the attenuation in the mid from 2.5 to .5 would be best. FWIW, the .5 ohm reading was found by measuring the existing pot just shy of full-on.

Thanks again!

[RoyC]

With that done, do you think I'm ok going back to the .5 ohm resistor in series and 15 ohm in parallel for the mid?

Based on your information...a 16 ohm tweeter shunt resistor, and 1 ohm series resistor/15 ohm shunt resistor for the mid, would probably be my choice to begin with.

Keep us posted on your results.

Best of luck,

Roy

[Guest IReilly]

I've just joined the AR-2ax club myself with a purchase of a pair of them.

My verdict on the sound of the speakers, as-is: Bleech. Nasal.

However, from my experience with another old set of speakers, Fisher XP-7's, I know that it is very likely due to inadequate tweeter output, though I do get output from the tweeters - they're the orange-brown phenolic dome tweeters, BTW.

Of course, I have yet to refurbish the problem-prone tweeter/midrange pots, and one of the midrange pots is frozen in place. And I should consider replacing the crossover capacitors. A question on the crossovers - it looks like AR used a two-in-one capacitor block. Are these electrolytic capacitors?

I'm still not optimistic that refurbishing the pots and caps will be the cure, since crossover components it should affect the midrange, too, and those drivers seem to have plenty of output.

So, I'm considering replacing the tweeters even at this early date. Of course, the obvious would be to buy an AR replacement for my tweeters, but it looks like they're not cheap, at $60 each. You can buy a pretty good tweeter, new, for $60. As for new tweeters, from searching this forum, I see a few candidates:

Hi-Vi K1

Hi Vi T20-4

Hi-Vi X1R

Audax TW010F1

These are quite inexpensive, at about $10 each. But maybe I could spend some more and get a nicer tweeter. Some that I've seen

The Vifa DX25, DX25TG05 looks promising. Znom: 4 ohms would mean 4 ohms nominal impedance, which seems like the original AR tweeter impedance. It doesn't seem to be in stock anywhere, though, even though it appears to still be in production

Others:

Seas 22TAFG Impedance curve looks like it's 5 ohms from 3K to 10K Hz, climbs to 7 ohms at 20K

Seas 27TBFCG Nominal 6 ohms impedance.

Seas 27TDFC Nom. 6 ohms impedance.

Of course, there are also sensitivity questions. But I would think that the tweeter level pot would give me a lot of latitude in tweeter sensitivity/impedance, by just adjusting tweeter output to taste.

Has anyone considered these more-expensive tweeters? And reasons pro or con on their use? I haven't given a lot of thought to physically fitting them into the speaker, though I'm sure I could make modifications so they'd fit in the space where the current tweeter resides. There may even be some standardization - I noticed that an EPI inverted dome tweeter plate is almost the exact same size as the AR.

Right now, I've tried a jerry-rig cure of simply running a pair of speakers with a healthy top end in parallel with the AR-2ax's. The results are intriguing - the nasality is diminished, but the midrange carries substantial punch on vocals. If I could boost the treble on the AR-2ax's, the result might be a speaker that's very good on pop or even rock, except for the really loud and heavy stuff.

[RoyC]

Of course, I have yet to refurbish the problem-prone tweeter/midrange pots, and one of the midrange pots is frozen in place. And I should consider replacing the crossover capacitors. A question on the crossovers - it looks like AR used a two-in-one capacitor block. Are these electrolytic capacitors?

So, I'm considering replacing the tweeters even at this early date.

Yes, the caps are electrolytic, and likely need replacement.

I have been experimenting with replacement tweeters for the AR-2ax, 5, and 3a for a number of years now, and have come to the conclusion that many modern tweeters will function as satisfactory replacements for the increasingly compromised early AR dome tweeters. There are discussions and concerns about dispersion issues, but in practical use and experience, the new tweeters are often perceived as adequate, (even "improvements") over what existed before.

At least four things must be considered before going in this direction:

1) Are you looking to alter/improve the sound, or are you trying to approximate the originally intended sound?

2) Regardless of the goal, a crossover modification will be necessary with any modern tweeter.

3) Is ease of installation into the unusually large AR cabinet hole a difficult issue for you to deal with?

4) Always replace them in pairs.

I continue to return to Hi Vi Research tweeters because of their excellent price to performance ratio, and wide, (no adapter required) faceplates. They are also readily available from parts dealers, such as Madisound and Parts Express. The Hi Vi Research Q1R ($23/ea) is my current favorite, and was recently used to replace a pair of original AR-2ax 1" orange dome tweeters. The only crossover modifications were a parallel inductor and a series resistor added to the tweeter circuit, and the results were surprisingly pleasant. The sound is a bit more open and detailed, without compromising the warm character these speakers are known for.

see attached pics...

Roy

[JKent]

The Hi Vi Research Q1R ($23/ea) is my current favorite, and was recently used to replace a pair of original AR-2ax 1" orange dome tweeters. The only crossover modifications were a parallel inductor and a series resistor added to the tweeter circuit, and the results were surprisingly pleasant. The sound is a bit more open and detailed, without compromising the warm character these speakers are known for.

Valuable info (again) Roy!

What are the values of the inductor and resistor you use with the Q1R?

Is this an issue:

• Power handling: 15 watts RMS/30 watts max
  

Kent

[RoyC]

Valuable info (again) Roy!

What are the values of the inductor and resistor you use with the Q1R?

Is this an issue:

• Power handling: 15 watts RMS/30 watts max
  

Kent

Hey Kent,

The power handling rating is not an issue, as the inductor and very high crossover frequency offer much protection. Most decent modern tweeters will handle more power than the original AR tweeters regardless of the published ratings, which usually assume a lower crossover frequency. Further, the original tweeters are not protected by a shunt inductor.

The inductor was an off the shelf 18ga, .05mh air core, and the resistor was 1.5 ohms. The goal was to keep it simple by using the original cap values. The resistor is, in part, used to compensate for the very low circuit impedance caused by the inductor.

*I also reversed the polarity of the tweeter connections compared to the original, as the addition of the inductor changes the phase relationship. (AR did this to the AR-11, AR 12, and 10pi when the parallel .105mh inductor was added to the scheme of things.) BTW, the tweeter is mounted sideways because I did not want the new screw holes to interfere with the old cabinet T-nut holes. They are still there, filled with putty, in case an original tweeter faceplate is used again someday.

In the next month or so I will be working with Larry Lagace (aka "Vintage AR") to explore the possibility of assembling practical tweeter replacement kits for the 3a and 2ax. AB Tech has not been able to provide tweeters for some time now. Between the availability issue and the rather high price of the AB Tech tweeter, I guess the time has come to get more serious about other replacement options.

Roy

[soundminded]

The inductor was an off the shelf 18ga, .05mh air core, and the resistor was 1.5 ohms. The goal was to keep it simple by using the original cap values. The resistor is, in part, used to compensate for the very low circuit impedance caused by the inductor.

Roy

As an aside, the addition of the inductor shunted across the voice coil will convert the crossover network from a first order high pass filter to a second order filter. The correct values for this inductor depend on the series capacitor and the Voice coil impedence. Handy on line calculators for Butterworth alignments and Linquist-Riley alignments are available all over the internet. When properly aligned to a Butterworth configuration, both filter elements will have the same 3db down frequency. As the frequency goes up, the impedence of inductor goes up because X(L) = 2pi*f*L. As the frequency goes down the impedence of the capacitor will go up because X© = 1/2pi*f*C. This creates a 12 db per octave falloff below the cutoff frequency instead of 6 db. This further restricts power to the tweeter at frequencies of interest only which is the frequeny range above the crossover frequency. This reduces the risk of burnout by avoiding inadvertently overdriving the tweeter below its crossover frequency. Adding the resistor will alter the Q of the filter circuit I think increasing it. If L is too small, its effect will be minimal, even inaudible.

The problem with re-engineering these speakers with modern replacements is that the philosophy of modern speaker design has as its intent to restrict dispersion while in this era, AR's intent was to acheive the widest dispersion possible. This is why satisfactory replacements to restore the origional performance now seems next to impossible. Personally I have experimented with 3/8" polypropylene tweeters from Audax but not in this context. It has fairly wide dispersion for a modern tweeter. There may be ways to modify these tweeters to improve dispersion otherwise they may have to be installed in multidirectional arrays. I'm considering building one now myself.

[Guest IReilly]

Yes, the caps are electrolytic, and likely need replacement.

I have been experimenting with replacement tweeters for the AR-2ax, 5, and 3a for a number of years now, and have come to the conclusion that many modern tweeters will function as satisfactory replacements for the increasingly compromised early AR dome tweeters. There are discussions and concerns about dispersion issues, but in practical use and experience, the new tweeters are often perceived as adequate, (even "improvements") over what existed before.

At least four things must be considered before going in this direction:

1) Are you looking to alter/improve the sound, or are you trying to approximate the originally intended sound?

2) Regardless of the goal, a crossover modification will be necessary with any modern tweeter.

3) Is ease of installation into the unusually large AR cabinet hole a difficult issue for you to deal with?

4) Always replace them in pairs.

I continue to return to Hi Vi Research tweeters because of their excellent price to performance ratio, and wide, (no adapter required) faceplates. They are also readily available from parts dealers, such as Madisound and Parts Express. The Hi Vi Research Q1R ($23/ea) is my current favorite, and was recently used to replace a pair of original AR-2ax 1" orange dome tweeters. The only crossover modifications were a parallel inductor and a series resistor added to the tweeter circuit, and the results were surprisingly pleasant. The sound is a bit more open and detailed, without compromising the warm character these speakers are known for.

see attached pics...

Roy

Thank you for the detailed information - this is just what I need to get my AR2ax's sounding the way I want them to!

I'm not insistent on absolute sonic authenticity, just as long as the speaker is pleasing. I have to wonder sometimes if changes in tastes in speaker voicing didn't happen starting in the seventies. In a couple of my older speakers I've noticed the same tendency towards a nasal kind of sound. It may just be a coincidence due to the tweeters of the older speakers being worn out. Or maybe the old speakers were voiced for tube amps and I'm driving them with transistors.

Another crossover question. When you replaced the capacitors, did you use electrolytics, or polymer film-type capacitors? And, of course, if you used the latter did you add a resistor to compensate for any ESR changes?

Also, when you mention the inductor being put in parallel with the tweeter, I interpret that as the inductor being installed across the terminals of the tweeter, or its equivalent (I know enough not to solder directly to the tweeter terminals - I'd probably solder it across the relevant lugs of the crossover pot leading to the tweeter). Am I correct?

[RoyC]

Another crossover question. When you replaced the capacitors, did you use electrolytics, or polymer film-type capacitors? And, of course, if you used the latter did you add a resistor to compensate for any ESR changes?

Also, when you mention the inductor being put in parallel with the tweeter, I interpret that as the inductor being installed across the terminals of the tweeter, or its equivalent (I know enough not to solder directly to the tweeter terminals - I'd probably solder it across the relevant lugs of the crossover pot leading to the tweeter). Am I correct?

-I used film capacitors.

-I did not add any "ESR" resistors, just added one in the tweeter circuit for other reasons.

-You are correct regarding the inductor.

Roy

[Beltway]

Great info on the potential replacements for the original tweeter. While I may be headed in that direction eventually, it seems that my original drivers are all still running strong. I installed 15.7 ohm Mills resistors in parallel for the tweet and mid, with a 1/2 ohm in series for the mid in one speaker so far. A/B comparisons with the un-modded speaker suggest that the mids have opened up considerably with the elimination of the pot. Even at full-on position the pot seems to be choking the sound. Not really attenuating it, but just keeping it from sounding its best. I suspect the wiper/coil energy transfer in the pot isn't the best under ideal conditions, and 40 years hasn't done much to improve it. Then again, I am new to all this and could be totally wrong. Regardless, the modded speaker sounds fantastic to my ears and I can't wait to do the other.

Anyway, thanks to all for the great information!

[Guest IReilly]

-I used film capacitors.

-I did not add any "ESR" resistors, just added one in the tweeter circuit for other reasons.

-You are correct regarding the inductor.

Roy

Again, thanks for the information!

Still more questions, though. I took the plunge and ordered the HiVi Q1R tweeters. How did you connect them? The connecting lugs on them look like they're intended to be soldered, as they look a bit small and fragile for use with a slip-on type connector.

Also, it looks as if you drilled six new mounting holes for the tweeter. It looks like I could use three of the original holes for the AR tweter, but I'd have to knock out the T-nuts for the huge mounting bolts AR used. I'm leery of pounding on these speakers. Or, is knocking out the original T-nuts not such a traumatic experience as I fear?

The HiVi tweeters strike me as pretty substantial units, and I'm anticipating very nice results with them.

When I opened my AR-2ax up, I found that the previous owner had replaced the (wrecked) mid and tweeter rheostats with resistors, each rheostat replaced with a voltage divider network of two 5 watt 8 ohm resistors, with the lead to the driver connected between the two resistors.

(printed on the resistors is 5W 8.2R 5% 064H - I assume that means 8.2 ohms, 5 watts power rating, 5% tolerance, and a 0.064 henry inductance).

That'd seem to me to be the equivalent of a 16 ohm rheostat set at midpoint. If I'm right about the information printed on the resistors, they aren't non-inductive, but, come to think of it, those rheostats, with a coiled wire in them, must have a significant inductance themselves.

Is this correct?

If so, then it looks like there are distinct differences in the recommended type of voltage divider network to replace the original rheostats - 50:50 vs 15:1, etc. Maybe a 3 position switch to select the resistor configuration to your liking, with a 5 dB or so difference between settings? Even though you'd be jamming a heck of a lot of somewhat bulky resistors into each speaker.

[Guest IReilly]

...and another thing. Which wire should I connect to the + terminal of the HiVi tweeter (yellow or black)? The original AR tweeter has no polarity markings that I can see, so I can't work from that, nor does the schematic I've found on this forum.

Again, thanks for all the information.

The new capacitors and the crossover network modifications have been installed, waiting for the tweeters. All that remains is scraping off the black sealant goop on the woofer in preparation for re-mounting and I'll have one speaker done.

[RoyC]

Again, thanks for the information!

How did you connect them? The connecting lugs on them look like they're intended to be soldered, as they look a bit small and fragile for use with a slip-on type connector.

Also, it looks as if you drilled six new mounting holes for the tweeter.

... they aren't non-inductive, but, come to think of it, those rheostats, with a coiled wire in them, must have a significant inductance themselves.

Is this correct?

If so, then it looks like there are distinct differences in the recommended type of voltage divider network to replace the original rheostats - 50:50 vs 15:1, etc. Maybe a 3 position switch to select the resistor configuration to your liking, with a 5 dB or so difference between settings? Even though you'd be jamming a heck of a lot of some what bulky resistors into each speaker.

IReilly,

If the tweeter is turned sideways, the six holes will miss the cabinet holes. The tweeter can then be connected with (6) #6 deep thread screws without interference from the existing t-nut holes. (I used the black screws sold by Parts Express). Gasket putty can be used to fill the old holes, so you can easily go back to an original tweeter if you wish. If you want to eliminate the holes, the t-nuts are very easy to tap out. Fill the old holes with epoxy filler putty and proceed as above.

The tweeter lugs take common 3/16" connectors. The yellow wire goes to +, and black to -. (The polarity is reversed relative to the midrange and woofer.)

Level control issues have been discussed at length in many areas of this forum...resistor inductance is the least of your worries. BTW, a variable level control is a handy thing to have when experimenting with a new tweeter.

Since this thread entered the realm of "mods" or "tweaks" a long time ago, I'll send you a message through the forum and we can discuss more details privately.

Roy

[Guest IReilly]

IReilly,

If the tweeter is turned sideways, the six holes will miss the cabinet holes. The tweeter can then be connected with (6) #6 deep thread screws without interference from the existing t-nut holes. (I used the black screws sold by Parts Express). Gasket putty can be used to fill the old holes, so you can easily go back to an original tweeter if you wish. If you want to eliminate the holes, the t-nuts are very easy to tap out. Fill the old holes with epoxy filler putty and proceed as above.

The tweeter lugs take common 3/16" connectors. The yellow wire goes to +, and black to -. (The polarity is reversed relative to the midrange and woofer.)

Level control issues have been discussed at length in many areas of this forum...resistor inductance is the least of your worries. BTW, a variable level control is a handy thing to have when experimenting with a new tweeter.

Since this thread entered the realm of "mods" or "tweaks" a long time ago, I'll send you a message through the forum and we can discuss more details privately.

Roy

Sorry to be a PITA, but I did get enough information to get one of my AR-2ax's up and running. And it didn't blow up, no magic smoke or horrible noises. Instead, it sounded pretty good! Nice rounded tone to the treble. But I still don't have a stereo pair, so it's back to work on the second one.

[NickByte]

i m sorry .... after 10Y i follow this thread ... :)

i need to replace the Pot 16 ohm 25W with 15 ohm 15W .....  in your opinion, can i have problem ?

Only 15W it's dangerous ?

Thanks

[Aadams]

32 minutes ago, NickByte said:

Only 15W it's dangerous ?

From the restoration guide

[NickByte]

5 hours ago, Aadams said:

From the restoration guide

thank you ... but i dont have LPad ..... 

I prefer use new reostat but i find only a 15 W version instead 25W ....

i can use 15W in your opinion ? ... i risk of burning it ?

[Aadams]

I did not catch that at first.  Wait for RoyC or message him and you will get the correct answer.     There are some suppliers on EBAY who sell "boutique" Pots that get good marks but the move to LPADs has accelerated now that the correct pots are no longer easily found in new condition.  If you are in the US there are trustworthy suppliers of good used pots.

4 hours ago, NickByte said:

I prefer use new reostat but i find only a 15 W version instead 25W .