Drop-in replacement for RM1 tweeters

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7x57

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Drop-in replacement for RM1 tweeters
« on: 19 Feb 2015, 04:29 pm »
I was over at Parts Express looking at possible replacements for the spiral ribbon tweeter in the RM1.

It looks like the Dayton Audio AMT2-4 would be a drop in replacement. It is rated 4-ohm, is only 0.016" smaller in outside diameter, has a sealed chamber, and will fit in the existing cut-out.  91 dB @ 1W/1M is the listed efficiency, plenty of power handling. Based on the folded pleat Heil AMT design, which is supposed to be very good and similar to ribbons in sound. At $70 each they are not a cheap tweeter, but it is really the only round faceplate ribbon-like tweeter Parts Express lists that will drop in with no mods.

Anybody here have any experience with the Dayton Audio AMT2-4 tweeter?

Both of my tweeters are working in the RM1, but one measures a bit different in frequency response than the other. One of them seems to have a damaged trace that was bridged to make a repair. This is a sound level meter difference, as I haven't noticed any imaging problems. I just want to know what a good drop-in replacement would be when I need it.

I am of the understanding that the spiral ribbon EMIT tweeter used in the RM1 is far from state-of-the-art now as it is single ended drive, not push-pull. It seems a lot of Genesis owners ended up replacing this tweeter in their speakers. I'm thinking the AMT2-4 might be a worthy upgrade if I get better sound quality.

John Casler

Re: Drop-in replacement for RM1 tweeters
« Reply #1 on: 19 Feb 2015, 05:17 pm »
We actually have a box of NOS Spiral Ribbon tweeters for $39 each, so no need to switch unless you are able to find something better.

Also, if the specs do not match exactly, the XO network will have to be adjusted to the different specs.

Stimpy

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Re: Drop-in replacement for RM1 tweeters
« Reply #2 on: 19 Feb 2015, 05:17 pm »
I've never heard any of the ESS based tweeters.  But, I'd like to try some of the Parts Express variants.

But, Chinese manufacturer Hygeia, still lists Emit-R style tweeters on their web-site. I'd expect that they may be the OEM manufacturer? Maybe they can sell direct, or provide dealer contact info?

http://www.hg-audio.com.tw/product_tweeter.html

This Chinese company resales some nice stuff too.  That is, if you can find a deal with reasonable shipping!

http://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20150219091229&SearchText=ribbon+tweeter

Even Aurum Cantus!

http://www.aliexpress.com/item/All-New-Aurum-Cantus-G2Si-Ribbon-Tweeter-In-Black-Faceplate/32241909835.html

Good luck!

7x57

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Re: Drop-in replacement for RM1 tweeters
« Reply #3 on: 20 Feb 2015, 06:08 am »
Stimpy,

Aurum Cantus will probably need a crossover mod and is too pricey for me.

Hygeia ribbon tweeters are not the same. My tweeter has 4 screws holding the faceplate to the magnet assembly, and the Hygeia has 3 screws instead. It is obviously a copy and they didn't even try to keep the cosmetics the same.

That Chinese company charges more for the Dayton Audio tweeters than Parts Express does, and then you have high shipping cost to boot. There are guys who order RC model airplane gear straight out of China and the failure rate is high and the shipping is too much for warranty issues. I intend to not order direct out of China. It usually takes a USA distributor running interference when dealing with China to make it worthwhile.

The NOS EMIT-R tweeters from John at $39 each are probably the way to go, and the AMT2-4 from Dayton would probably be a reasonable upgrade at $30 more per each..

The EMIT tweeters are single ended planar magnetic and not really ribbons. EMIT means electromagnetic induction tweeter. Best I can figure from the info on my kit schematic, the RM1 crossover is about 10 kHz and it needs to be that high to make the EMIT tweeters reliable. My testing confirms the high crossover point. I have an early 2001 model, and later RM1 models had a series inductor rolling off the midrange so later tweeters may crossover lower.

Aurum Cantus would be the way to go if cost is no object and you don't mind the crossover tweaking it may require.

The Swans Hi-Vi tweeters are push-pull ribbons but they require cabinet mods, but get good reviews and are reasonably priced.

Dayton Audio also makes what looks like a drop-in 4-ohm and 8-ohm woofer for the RM1. I have the two 4-ohm Misco speakers wired in series for 8 ohms. Rather smallish magnets, but they sound better than you would expect by their looks.

7x57

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Re: Drop-in replacement for RM1 tweeters
« Reply #4 on: 20 Feb 2015, 08:19 pm »
UPDATE:  The original tests I did on my RM1 tweeters were soon after replacement of a bad tweeter. After two years of break-in, I decided to re-run the test this morning. Both tweeters were within 1dB of each other throughout the passband except at 12.5 kHz where they was a 1.5 dB difference. Since even the highest quality tweeters typically state plus or minus 1.0 dB linearity, up to a 2 dB difference is acceptable between two high-quality tweeters. In other words, a long break-in period brought my tweeters within specs. This rather surprises me as the EMIT-R tweeter has a "loose" mylar diaphragm and should not benefit from break-in like a dome tweeter that has a support diaphragm, often doped with damping material. I would also mention that the initial difference was more a measurement thing than an audible thing. I never heard an audible difference initially or during break-in. The midrange drivers also never changed much from new to break-in. This is very much unlike my old Vandersteen 2Ci speakers that improved dramatically during the first week of listening to them.

I also took a small soft bristle brush and removed some small specs of dirt off the original tweeter. May have helped a bit.

The Hygeia tweeters stated a plus or minus 2 dB linearity, so I don't think I would want to go there.

fredgarvin

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Re: Drop-in replacement for RM1 tweeters
« Reply #5 on: 21 Feb 2015, 01:54 am »
We actually have a box of NOS Spiral Ribbon tweeters for $39 each, so no need to switch unless you are able to find something better.

Also, if the specs do not match exactly, the XO network will have to be adjusted to the different specs.

That's good to know John. Although the only problem I ever had with any VMPS models was not speaker but x-over related, You never know.

Stimpy

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Re: Drop-in replacement for RM1 tweeters
« Reply #6 on: 21 Feb 2015, 05:44 pm »
The EMIT tweeters are single ended planar magnetic and not really ribbons. EMIT means electromagnetic induction tweeter.

Understood!  I've owned different Infinity EMIT based speakers for years.  So, I knew they were planar magnetic.  Planar magnetic, just like my Monsoon's too.



Dayton Audio also makes what looks like a drop-in 4-ohm and 8-ohm woofer for the RM1.

Which Parts Express woofer?

Also, MCM makes a nice carbon fiber, cast frame woofer, that Brian offered as an upgrade to the standard woofers, for RM-1 owners.  Don't leave it out as a possibility!



http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-3550-/55-3550

Otherwise, glad to see your efforts in maintaining your VMPS speakers.  They're worth the effort!   :rock:


7x57

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Re: Drop-in replacement for RM1 tweeters
« Reply #7 on: 21 Feb 2015, 10:48 pm »
Stimpy,

I looked at that MCM woofer and did not like it for the resonant frequency or something. The Parts Express woofer is the reference woofer and it is available in 4-ohm or 8-ohm version, RS225-4 and RS225-8. Therefore, it will work in the 4-ohm or 8-ohm version of the RM1. That means you do not have to change your series inductor.  An Erse Q inductor will probably run you over $20 from Parts express. Consider that cost when making an impedance change in your woofers, beside the installation time and trouble. The Parts Express woofer has a phase plug similar to the original Misco based woofers. The Dayton Audio 8" Reference woofer from Parts Express is USA built and probably of very high quality, and the price isn't cheap at $58 which means it probably is very high quality. Something out of Scandinavia, France or Germany of the same quality has to cost 50% to 100% more due to import tariff and distributor markups. Parts Express probably buys Dayton Audio drivers factory direct. That means the Dayton Audio Reference woofer would be about a $100 woofer if coming from the top makers in Europe. If I decide to change woofers, the Dayton Audio Reference woofer gets my nod. The resonant frequency, efficiency and cabinet volume requirements are near perfect too. I might also consider them for the Vandy 2Ci speakers I have that need woofer rebuilds. It is less than the Vifa woofer and far less than sending the old woofers to Vandersteen for a rebuild. They are a bit more efficient than the Vifa woofers.

The VMPS midranges were advertised as ribbons, but I view them as push-pull planar magnetics as well. There is only a slight difference between the two designations. The planar magnetic has a voice coil printed on a membrane while the ribbon has a conductive membrane. True ribbons need an impedance matching transformer in most cases while planar magnetics do not. The advantage of having the membrane as the conductor is offset by transformer parasitics. I believe the biggest difference is whether it is push-pull or single-ended, not whether it is planar magnetic or true ribbon.

Thus, the EMIT  tweeters should be outclassed by more modern push-pull ribbons or planar magnetics.
« Last Edit: 22 Feb 2015, 03:19 pm by 7x57 »