Mirage SM-.5 Woofer Impedance

[JRosenb88]

I picked up a pair of these speakers from GW for $20 only downside is it doesn't have the orginal woofers. The woofers that are in it are 8ohm and these speakers get really weak bass response. I'm thinking maybe it's suppose to have 4 ohm woofers maybe that's why the bass response is so lacking? Is there anybody that has these and can confirm what Impedance the woofers are does anybody know where or how I could find this information? TIA.

 

[elnaldo]

Not many info on the web about your speakers..

I think the weak bass is because the woofer is not designed for that enclosure, not just the 4/8 ohms issue. It could be efficiency of the new woofer, Qts parameters, and a lot of things all together.

You have 2 routes: Optimize what you have, or try to get the right replacements for that enclosure-crossover.

 

[JRosenb88]

I was thinking the same thing and I have polyfil quilt batting and I messed around with that.... A LOT. But, it didn't seem to make a difference so I don't think it's the cabinet itself.... efficiency would make sense for sure. I'm going to hope I find out from someone what impedance the woofer is. I currently have a lead on that. I think make the crossovers just.... don't deliver? I'm not sure though and don't feel like spending the dough especially since, about an hour ago my SA-8800 died. :tears: Anyway, here's a link to the replacement woofers that I found in them.

http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-1240-/55-1240

 

[JRosenb88]

I'm kind of wondering a new crossover and woofers will make these puppies shine as I like the cabinets. I might even just want to sell them. Not too sure yet.

 

[elnaldo]

Sad to know about your SA8800 ..... But this happens, I burned my amp 2 times by myself...

That woofer is quite sensitive (91 dB) so that's not the issue. It's response is quite high, up to 5000Hz. If your crossover is not designed for that, it could be that mid-frequencies are too forward and tame the bass. Qts for that woofer is a bith high, but normal, it requires a quite large cabinet.

Can you post some info about your actual crossover? I mean, what is between the signal and the driver, everything and every connection... Perhaps some easy tweak can give you an acceptable result...

 

[dumptruck]

I'm kind of wondering a new crossover and woofers will make these puppies shine as I like the cabinets. I might even just want to sell them. Not too sure yet.

Not unless the crossover is properly designed by somebody.. Not sure what you could do here that would make any financial sense... I guess we could try to make the cab work for the woofer and see where that leaves you (presumably still with some crossover problems).

That woofer doesn't exactly need a large cabinet, and porting it is probably the way to get bass in your cabinets, if there is one. Figure out the internal volume and report back . Maybe if we get the woofer operating decently, a small crossover tweak could finish the job well enough. Any solution involving buying new drivers would put you in a realm where choosing a published DIY design that fits the box size would make more sense.

 

[JRosenb88]

I don't think it's the volume of the box as I messed around with adding a little then a little more than a bunch than a substantial amount, then stuffing it full of polyfil batting. Didn't make much difference at all and adding polyfil slows down the sound waves, so adding polyfil will make the box think it's bigger. There is also not a port on the speaker at all. I will take the woofer out and take some pictures tomorrow.

 

[elnaldo]

As dumptruck suggested, post here the box volume, and confirm that the woofer is exactly that one you linked before. Box can be calculated from the manufacturer data, and if needed, a port can be added to your actual cabinet.

Also, post the diagram of your actual crossover, the way everything is connected, to see if some tweak can help.

 

[dumptruck]

Yes, you need large changes in volume to make much difference in a sealed box, but that's not the point. Need to know the volume of the box to see what's going on and to add a port.

 

[JRosenb88]

I used a box calculator and it came up with .556 ft cubed.

 

[dumptruck]

That appears to be a rather crappy 1st order high pass for the tweeter with the woofer running wide-open. Something like 2-6kHz, depending on the tweeter impedance.

 

[Franksta]

OK I went and found my pair of SM-.5's. They must be fairly rare because I remember asking about them once and I got very little. Here are my observations.........

I refoamed my pair but I did not recap them. They sound very good but maybe not great. I only auditioned them for a short time and I became more impressed the more I listened.

They are acoustic suspension design with a thick and substantial wood cabinet. MDF with vinyl wood grain that looks like a burl design. The woofer is a heavy/thick paper cone with a rubber like coating. They appear stiff and offer a lot of resistance to movement. They are obviously well built with the heavy cabinets nice woofers and a dome tweeter that has a thick felt surround to minimize baffle reflections. Binding posts and nice square drive screws show the quality of workmanship.

As for the sound qualities...They are slightly subdued in the high end and have a good bass response without sounding boomy or tubby. They must be fairly inefficient because I wanted to keep turning them up. I had them sitting on the floor when I listened. They were dying to get up to ear level where I am sure they would really shine. I feel like with sufficient power and correct placement these are very nice keepers. There is a lot of competition in their size category. They are smaller than Dynaco A-25's and about the size of the Realistic MC-1401's that I have. If given a choice in this size range I would much rather have my EPI 100's they also have a simple 1st order designed crossover and they sound wonderful!

I would try to find woofers that would match the cabinets better than what you now have instead of cutting a hole in them and trying to guess what kind of port to use. I have some pictures below. The numbers on the tag you see on the woofer are PL1J4 (1st line) and SM-5W (2nd line). I didn't see a reference to the OHM rating and I don't have a meter to measure it. I have always assumed these were 8 ohms. Hope all this helps and gives info for anyone else that finds a pair. Good Luck! Franksta

 

[dumptruck]

I would try to find woofers that would match the cabinets better than what you now have instead of cutting a hole in them and trying to guess what kind of port to use.

I disagree. We know the parameters of the replacement woofers (we think). We do not know anything about the tweeter to make a good woofer choice, nor good crossover design, so why bring more random drivers into the mix? Thanks for posting the pics.

However, there's nothing you can do with a port in that volume except increase 100Hz boom, and you should already be getting some. You may be able to eek out an f3 around 65-70 sealed. Stuffing will mainly serve to drop the 100Hz boom. What's probably happening here is that the woofer has a rising response into the upper midrange, and with no crossover on the woofer, that's what you're going to hear more than anything else. Got any inductors?

What's that white resistor connected to?

 

[sax6]

OK I went and found my pair of SM-.5's. They must be fairly rare because I remember asking about them once and I got very little. Here are my observations.........

I refoamed my pair but I did not recap them. They sound very good but maybe not great. I only auditioned them for a short time and I became more impressed the more I listened.

They are acoustic suspension design with a thick and substantial wood cabinet. MDF with vinyl wood grain that looks like a burl design. The woofer is a heavy/thick paper cone with a rubber like coating. They appear stiff and offer a lot of resistance to movement. They are obviously well built with the heavy cabinets nice woofers and a dome tweeter that has a thick felt surround to minimize baffle reflections. Binding posts and nice square drive screws show the quality of workmanship.

As for the sound qualities...They are slightly subdued in the high end and have a good bass response without sounding boomy or tubby. They must be fairly inefficient because I wanted to keep turning them up. I had them sitting on the floor when I listened. They were dying to get up to ear level where I am sure they would really shine. I feel like with sufficient power and correct placement these are very nice keepers. There is a lot of competition in their size category. They are smaller than Dynaco A-25's and about the size of the Realistic MC-1401's that I have. If given a choice in this size range I would much rather have my EPI 100's they also have a simple 1st order designed crossover and they sound wonderful!

I would try to find woofers that would match the cabinets better than what you now have instead of cutting a hole in them and trying to guess what kind of port to use. I have some pictures below. The numbers on the tag you see on the woofer are PL1J4 (1st line) and SM-5W (2nd line). I didn't see a reference to the OHM rating and I don't have a meter to measure it. I have always assumed these were 8 ohms. Hope all this helps and gives info for anyone else that finds a pair. Good Luck! Franksta

I'm glad to see those in an original version for i'm a very nostalgic audiophile
about Mirage product made by Inception audio. Bought my SM-1 in Montreal
back in 1982. Now long gone, ( with former girlfriend ) never saw another pair
anywhere. Would pay for another one

 

[elnaldo]

What's probably happening here is that the woofer has a rising response into the upper midrange, and with no crossover on the woofer, that's what you're going to hear more than anything else.

+1, that's exactly what I think, if the replacement is that woofer linked before, that goes up to 5000Hz, you could need at least 1 inductor as a low pass filter.

It would be good to know the capacitor value and the tweeter impedance, to guess the actual crossover point.

Try to draw a schematic with both drivers, and the cap and the resistor values.

Did you try e-mailing mirage speakers asking for info? Was the original a Peerless woofer?

 

[JRosenb88]

The more posts I read the more I realize I don't know diddly

Of a limited number of crossovers I have seen these seemed to be the most pitiful.

I am unwilling to put a hole in the cabinet anywhere anyway. (it's sealed for a reason!)

I do not have any inductors nor do i know what that is and the white reistor is connected to the tweeter.

I can hook the other up to my sx-3600 / PC and run a frequency generator and get a good idea probably within 1,000hz at least.

I can try to make a schematic
the white tweeter resistor says 6-2ohm 10%
the blue cap says 6.8uf and ce85c 33sv
and the brown tooth lookin thing says 39 5% CD

I did not try emailing mirage, that is an excellent idea why didn't I think of that

 

[elnaldo]

Of a limited number of crossovers I have seen these seemed to be the most pitiful.

It's not, it's just a 1st order crossover for the tweeter (1cap, perhaps 2 in parallel, what is the same), and a woofer running full range, without any crossover, what is a normal design and many great sounding speakers are made like this. Genesis I, EPI 100, Infinity Qa, just to name some of them...

The cabinet is sealed for a reason: The specs of the original woofer. Some woofers work better in ported enclosures, some in closed boxes. But perhaps just adding an appropriate inductor, and changing (or not) that resistor, things can improve to a reasonable level.

That "tooth like" thing I think is an small film capacitor in parallel with the electrolytic cap.

Do you have the impedance of the tweeter, or any model on the label?

 

[JRosenb88]

---- Tweeter all these are on the yellow wire
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-----white resistor
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(picture of crossover I took)
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---red wire goes to woofer
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-black wire attaches to terminal on back of speaker and to the woofer and tweeter


I'm not sure if this is what is needed as a schematic as my electronics knowledge is limited to a basic electronics class I took a few years back in college.

The lowest setting on my multimeter for resistance is 200ohms and then I put the leads on the tweeter I get 7.8 ohms which I assume makes it an 8 ohm tweeter.
I've always saw this as somewhat correct as I have measured other speakers that I knew the impedance and it has been relatively close to the rated impedance.

 

[JRosenb88]

The tweeter is a Philips AD 11600/T8
and I rather like the sound of them, when I bought these one of the tweeters was busted so I bought 2 replacements to match them up since the replacements had broken.... defletors? over the tweeter itself.

 

[dumptruck]

I can never remember which vintage Philips dome is which, but they are nice and easy on the ears in general. I'm pretty confident that to make this woofer work, you're going to have to knock down it's midrange response with either an inductor, and inductor with a resistor in parallel, or perhaps both of those in series. I wouldn't feel great about sending you out to order inductors based on totally guessed values, though..