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Old 23rd July 2008, 07:58 PM   #1
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Default Morel voice coil replacements / new "CAT" tweeters...

I just got one each of the CAT 308 and CAT 298 tweeters at the PE tent sale. I'd never tried Morel tweeters and was curious to do so. They do seem a little expensive though. (overpriced?) I do like the solid aluminum face plate compared to the flimsy plastic face plates of some tweeters.

I was wondering how interchangeable the various replacement voice coil/diaphragm assemblies are on amongst the various Morel tweeters. For instance, might I be able to put this:
Click the image to open in full size.
On either my CAT 308 or 298 magnet assemblies?

I've seen various posts where people switch diaphragms, but so far, only w/Seas tweeters, such as the DXT (similar sized horn as the Morel).

My main desire for using the horn is time alignment.

EDIT: Oh ~ and, does anyone know what other cheaper brand of tweeter might be compatible with the Morel voice coil assemblies?

The one remarkable feature that most of the Morel tweeters seem to have is high power handling, if the published numbers are accurate? They claim very low compression at high power levels. Some individuals comments seem to reflect this.
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Old 7th October 2009, 06:22 PM   #2
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I got one of those "replacement voice coils" which comes with the waveguide faceplate and it does indeed fit on both of the different Morel magnet (motor) assemblies I have. And, it comes with the screws that you need to attach it, which is particularly nice since the screws for the other face plates aren't long enough.
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Old 7th October 2009, 08:11 PM   #3
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That looks like a DMS 37 semi horn loaded face plate. The DMS 37's are what I'm using (for time alignment reasons also) It was designed by the Morel Aust distributor (who uses their drivers exclusively in his own high end loudspeaker designs) so that when flush mounted it was time aligned with the 5" MW-144 if it was surface mounted (or so he told me).

I have yet to do any measurements to verify this. Whilst the magnet assemblies might be physically compatible, whether or not an old version tweeter such as the DMS 37 has the same magnet construction as a new tweeter is probably something you should consider... Not sure if the specs give info on the motors, but if they do and they don't sound the same it might not be a good idea to mix and match

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Old 8th October 2009, 02:05 PM   #4
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Quote:
Originally Posted by critofur View Post
I just got one each of the CAT 308 and CAT 298 tweeters at the PE tent sale. I'd never tried Morel tweeters and was curious to do so. They do seem a little expensive though. (overpriced?) I do like the solid aluminum face plate compared to the flimsy plastic face plates of some tweeters.

I was wondering how interchangeable the various replacement voice coil/diaphragm assemblies are on amongst the various Morel tweeters. For instance, might I be able to put this:
Click the image to open in full size.
On either my CAT 308 or 298 magnet assemblies?

I've seen various posts where people switch diaphragms, but so far, only w/Seas tweeters, such as the DXT (similar sized horn as the Morel).

My main desire for using the horn is time alignment.

EDIT: Oh ~ and, does anyone know what other cheaper brand of tweeter might be compatible with the Morel voice coil assemblies?

The one remarkable feature that most of the Morel tweeters seem to have is high power handling, if the published numbers are accurate? They claim very low compression at high power levels. Some individuals comments seem to reflect this.
I can answer some of your questions and make an educated guess on others, though as Tony says, one can't be sure about the newest labeled versions.

I bought a couple of these a while ago as replacement attempts on the original MDT-30 driver (motor should match the 30s). I had previously bought MDT-32 replacements. This required prying off the solder mounts that are attached to the faceplate. This can be done, but you must take care not to get any metal shavings in the gap. I found that using after prying up the cardboard-like sides that I could then finish prying it off with pliers.

The MDT-37 replacement then fits right on as Tony said. I measured it on a PE baffle that doesn't has a larger cutout than required, but with felt over it, the result is excellent. I'll measure it on my 2mx2m baffle, just don't know when. I may try this weekend.

It will also fit the Parts Express "Silkie", the original versions I, II and III. I have a page at my site that shows a number of hybrids, the MDT-32 attached to a PE motor that is effectively an MDT-32, only without a real chamber. The MDT-37 attached to one of these ought to be a good combo. This would make for an el-cheapo version the MDT-37. It does need the pole-piece stuffing (lamb's wool or cotton) and should have a felt or cotton ring on the pole-piece top, but it's doable and not expensive.

I don't know if it will fit the newer DC28F (aka Silkie Gen IV), but the motor looks like the earlier Silkies. The advantage of the Silkies is that there is no voice coil solder mount to remove as there is in the MDT-30. The MDT-32, of course, has none either, but in that case you have the cost of the Morel motor. With a PE motor and Morel diaphragm assembly, you get nearly the same driver at much less cost. Morel did not change the basic motor for years apparently. I haven't seen a CAT308, but I'd lay money on the motor being the same.

That's not unusual. Vifa used the same tweeter motor across their entire line for years. Many of the D25/D26/D27 tweeters all used the same basic motor. Seas does this as well from the few I've seen. There are no cross-fitting substitutes for these, though. No cheap motors accept their diaphragm assemblies that I've seen.

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Old 8th October 2009, 02:52 PM   #5
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Hey Dave, I'm not sure why I didn't try mounting it on the DC28F - I vaguely remember that I noticed some mounting issue with the stamped pattern on the front motor plate on the DC28F I have... The ones I have I bought about a year ago, I'll have to see if it [the Morel 37 rep. dome] fits when I get home. If it does, I'll have to pickup a couple more.

Too bad it doesn't fit the nicer motor assembly of the RS28.

If it does fit the DC28F motor I'll have to take some measurements, and, see what woofers I can get time alignment with that setup... A friend of mine at a speaker company refuses to sell any new speaker designs that aren't time aligned after they did some listening tests with time aligned vs non-time aligned speakers.
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Old 8th October 2009, 03:54 PM   #6
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Hey Dave, I'm not sure why I didn't try mounting it on the DC28F - I vaguely remember that I noticed some mounting issue with the stamped pattern on the front motor plate on the DC28F I have... The ones I have I bought about a year ago, I'll have to see if it [the Morel 37 rep. dome] fits when I get home. If it does, I'll have to pickup a couple more.

Too bad it doesn't fit the nicer motor assembly of the RS28.

If it does fit the DC28F motor I'll have to take some measurements, and, see what woofers I can get time alignment with that setup... A friend of mine at a speaker company refuses to sell any new speaker designs that aren't time aligned after they did some listening tests with time aligned vs non-time aligned speakers.
There are few drivers/diaphragms that can be used with mixed manufacturers. The only other one with which I've had success is a hybrid Scan-Speak D2010 and Hiquphon. That takes some real work due to both being hermetically sealed and with a very tiny dimension issue with the top plate. It takes destruction of one due to no supply for replacement diaphragms.

Is he actually referring to a time-aligned system that is also a transient-perfect one? My suspicion is that he's actually referring to (nearly) aligned acoustic centers that improves phase tracking and keeps the lobe forward if an L-R type. Being time-aligned doesn't really mean much for a non-T-P type system. Phase tracking and lobe axis are far more influential. Time-aligned without phase tracking is something of a win/lose situation.

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Old 8th October 2009, 04:33 PM   #7
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He uses an old oscilloscope like device with both impulse clicks and square waves. With both the woofer + tweeter wired in phase he moves the tweeter physically back & forth to align the impulse and also to try to get a decent but maybe not perfect, square wave. Sorry I can't disclose the type of crossover that he uses though.

It is a mystery what the factors are that make me dislike most speakers I've auditioned, so, I'm always thinking about things like time alignment, transient perfect, etc... Hoping to find a speaker that I find emotionally engaging again, that I find pleasant to listen to for more than a few minutes (without spending tons of money). I suppose it's ironic that I've bought so many different "buyout" and other various drivers that I've easily spent more than it would have cost to buy a couple pairs of high end woofers + tweeters.
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Old 8th October 2009, 04:49 PM   #8
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He uses an old oscilloscope like device with both impulse clicks and square waves. With both the woofer + tweeter wired in phase he moves the tweeter physically back & forth to align the impulse and also to try to get a decent but maybe not perfect, square wave. Sorry I can't disclose the type of crossover that he uses though.

It is a mystery what the factors are that make me dislike most speakers I've auditioned, so, I'm always thinking about things like time alignment, transient perfect, etc... Hoping to find a speaker that I find emotionally engaging again, that I find pleasant to listen to for more than a few minutes (without spending tons of money). I suppose it's ironic that I've bought so many different "buyout" and other various drivers that I've easily spent more than it would have cost to buy a couple pairs of high end woofers + tweeters.
If the measured response can actually approximate a square wave, it sounds like he may have some sort of T-P crossover. Could even be simple a first order Butterworth for that matter, the type Dunlavy used, but it also sounds like a 2-way and other than BW1 there aren't many other options for a T-P system. If it's not a T-P system, the phase alignment is the key issue. Adjusting with that method probably emphasizes phase. Time can be identical, but if the individual target responses aren't met due to driver issues at their extremes, response may actually suffer.

The adjustment he's making most likely is not a perfectly time-aligned system, but one that is a compromise between time and phase alignment. This would be the best practical system, since most drivers have issues at both ends that affect phase in their bandpass.
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Old 11th October 2009, 01:18 AM   #9
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The adjustment he's making most likely is not a perfectly time-aligned system, but one that is a compromise between time and phase alignment. This would be the best practical system, since most drivers have issues at both ends that affect phase in their bandpass.
Most DIYers seem to want to put the best of this with the best of that. They fail to realise that what they are doing is to try and marry this mid to this tweeter. How the individual drivers perform is a small part to consider. The larger question should be how will my drivers marry. If they marry perfectly then and only then will you get a top class system. The DMS37 rebate mounted with the MW142/144 surface mounted are a near perfect match. So perfect that when you design the crossover you will be in for a surprise. I did up a nice 1st order xover, put in a whole lot of components and when measuring and listening I started taking out components. In the end I had one high grade cap left (5.6uf from memory) and the woofer was just taking it's feed straight from the amp. These two drivers just love each other. The relationship is much more important than the individual drivers.

Terry
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Old 11th October 2009, 02:11 AM   #10
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Hey Terry straight from the horses mouth! I didn't think you frequented the forums! I just checked your profile and found you are the person I alluded to in my previous post in this thread

I can't believe it is nearly six years since I first contacted you about the morel drivers! I'm going to get there eventually... Was starting to gain momentum again but have hit a wall for a little while, hopefully in a month or two will be back into it and get these things finished! and start enjoying them!

Tony.

edit: Nice to know when I did my prototype that I wasn't going crazy when I thought it sounded brilliant with just a cap on the tweeter and the mw144's running full range too!
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