toxcrusadr
Omelette au Fromage
Oh, puzzle glue! I didn't know that's what it was called.
Gauntlet throwdown for a maligned speaker - The Challenge
- Thread starter onwardjames
- Start date
Oh, puzzle glue! I didn't know that's what it was called.
Much thanks, it's only a thread for comments and fun ideas. My impressions of these, having owned them for 25 years, is that the woofer, while too big, is actually pretty fast. It's just not heavily built. The low end does indeed go rather low, but that may be the box. I've tinkered with port length too, and improved it somewhat.
Regrettably, no. They're currently doing duty on my covered porch, where I work out. And they're so efficient, I can hear them in my garden when I'm pulling weeds.
The thing is, my father and mother bought these for me back in 1989, or 90, I forget which, and selling them would seem an insult. So I'm just trying to find ways to make them more enjoyable.
I sold my 2205 Marshall 50 watt stack they got me, plus a 1986 Fender Strat. Ought to have my ass kicked. Plus, the Olds saxophone they bought me got stolen.
Hence, my attempts at improvement.
Oh, put some wine corks under the front, giving them a tilt. Definitely helped.
The main complaint I have, is that everything coming out of them sounds like a saxophone.
Methinks this project is at a point, where only an RTA/frequency response plotter, and a woofer parameter analyzer (such as the Dayton DATS/WT3) is going to help.
Get some good measurements of the individual drivers, and you will find out whether the drivers have any practical hope of being properly blended together, and if the drivers are appropriate for the box. If there looks like hope, then that data will also help in a new/better crossover design and better box tuning...
From past experience, I have a feeling that the midrange drivers are reasonably capable.
The tweeter can probably be tuned, via passive crossover design, to do reasonably well.
My really serious question is whether the woofer is going to cooperate with the rest of the plan...
Regards,
Gordon.
Get some good measurements of the individual drivers, and you will find out whether the drivers have any practical hope of being properly blended together, and if the drivers are appropriate for the box. If there looks like hope, then that data will also help in a new/better crossover design and better box tuning...
From past experience, I have a feeling that the midrange drivers are reasonably capable.
The tweeter can probably be tuned, via passive crossover design, to do reasonably well.
My really serious question is whether the woofer is going to cooperate with the rest of the plan...
Regards,
Gordon.
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Xover to tweeter is way too high for the dual mid arrangement, and probably a bit high for getting smooth horizontal polars too. Replacing the tweeter would be the most economical way to deal with that. If somebody wants to drop one at my house for a while, I'd be happy to do it, but not interested in talking about doing it without measurements.
I would be very surprised if any slow/boomy/etc. impressions of the woofer could not be solved by an xover redesign and/or cabinet adjustments, btw. The driver's probably just fine for its range.
From looking at that type tweeter- I see no reason, if a sufficiently steep slope was used (probably 18db/oct.), that the tweeter couldn't be crossed over low enough to do much better. I'd expect it should be able to cope with 3500 Hz, if not lower...
IIRC, the original crossovers in those were 6dB/octave. That's why the frequencies were so high...
With that much midrange cone area, I'd expect a 440Hz/3500 Hz crossover should work just fine. Maybe even 400/3200, if the tweeter was up to it...
I suspect that the woofer has an extremely high Q, at least in that box. Even sealed, it may well have a Qtc of well over 1, in the original enclosure. If that's the case, then nothing short of drastically modding the woofer or increasing cabinet volume would help much...
Regards,
Gordon.
IIRC, the original crossovers in those were 6dB/octave. That's why the frequencies were so high...
With that much midrange cone area, I'd expect a 440Hz/3500 Hz crossover should work just fine. Maybe even 400/3200, if the tweeter was up to it...
I suspect that the woofer has an extremely high Q, at least in that box. Even sealed, it may well have a Qtc of well over 1, in the original enclosure. If that's the case, then nothing short of drastically modding the woofer or increasing cabinet volume would help much...
Regards,
Gordon.
I love it when you guys talk all technical.
With a Q of that size, is open baffle totally out of the question?
I don't think anyone is real crazy about that shallow TALL box they're in. I know I hate how they will not stand erect on carpet. Always in danger of falling over.
With a Q of that size, is open baffle totally out of the question?
I don't think anyone is real crazy about that shallow TALL box they're in. I know I hate how they will not stand erect on carpet. Always in danger of falling over.
borus
Luthier tube guy
If you know the ports length and they are not bent (elbowed) filling them with drinking straws can have a positive effect. I don't remember where I got this from but it has worked it is reversible and cheep. I would also think that the midranges might need more enclosure space especially if you lower the crossover Hz
Another more expensive option: Figure out your internal volume, find a kit were the 152's volume will work and redo the whole speaker. Maybe this:
https://www.madisoundspeakerstore.c...o-sb12.3-sb-acoustics-12-dual-midrange-3-way/
or
http://www.visaton.com/en/bauvorschlaege/mehrwege/index.html
Again more expensive but you are keeping the Infinity's Mom and Dad gave you.
https://www.madisoundspeakerstore.c...o-sb12.3-sb-acoustics-12-dual-midrange-3-way/
or
http://www.visaton.com/en/bauvorschlaege/mehrwege/index.html
Again more expensive but you are keeping the Infinity's Mom and Dad gave you.
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dc270
Now Off the Reservation
See my avatar-SM 150's pulled everything, rebraced the whole insides. rebuilt the baffles to include DVC 12" Morels with a custom made 15" PR below, Morel 6.5" on top, Morel 40 tweeter topping that on threaded rails to time align! Custom built Link/Riley networks.
Sound unbelievably good! That's my custom SM story. While many folks find them abhorrent- I found a challenge and made good from it. Hope you can too!
DC
Sound unbelievably good! That's my custom SM story. While many folks find them abhorrent- I found a challenge and made good from it. Hope you can too!
DC
Both my Kappa 8's and Kappa 9's are tall and shallow, and both the RS 2.5 and RS 4.5 are quite tall and shallow, and all off them are quite capable.
I never owned the SM series but from the pairs I saw that I passed on, I always thought the cabinets were made with wood that is to thin. All the bracing in the world is still not going to address a problem if the wood is to thin.
I never owned the SM series but from the pairs I saw that I passed on, I always thought the cabinets were made with wood that is to thin. All the bracing in the world is still not going to address a problem if the wood is to thin.
dc270
Now Off the Reservation
Typically when I "brace" a box I will use min. 2" x 2" wood bats. While that helps at each end of the bat to prevent the thin wood side walls from "breathing", what I do different is to put a 10" or 12" .75" thick circle I have cut out from a previous project on centre of each end of the bat. A couple of bats front to back, a couple side to side, each one having a .75" thick circle on the end of each bat, well glued in place. This way I use up scrap wood and spread the wall thickness out from each bat used. This effectively creates wall thickness and prevents the box from breathing due to under sized wall thickness! Sure the SM's cut some corners, but can be made right again!
You have to remember to calculate the loss all these circles and bats create so you can re-tune the cabinet/ driver. It's a small price to pay to now have a much sturdier box and tuning modified.
DC
All good ideas, and interesting takes on this most hated of speakers.
Ken, I CERTAINLY didn't mean to imply tall and shallow = bad.
Just in this case, it does.
And dc270, that's a helluva mod you did, very impressive. The force is strong with this one.
Ken, I CERTAINLY didn't mean to imply tall and shallow = bad.
Just in this case, it does.
And dc270, that's a helluva mod you did, very impressive. The force is strong with this one.
SoundOfSound
Super Member
Can you post a pic of what they made the crossovers from?
StimpyWan
Addicted Member
Are those SMs ported? If so, I'd close the port, and convert the cabinet to a passive radiator design. Add a 15" passive, and retune to a higher Q, to tighten things up.
Also, with dual mids, maybe try a MTM layout, with the tweeter centered around ear height. That should improve imaging.
Plus, I like the idea of slightly shifting the crossover points. 500Hz and 5.5KHz aren't the best points for those drivers. Maybe 350Hz and 3.5KHz. And you should at least use some Dayton caps. Good and cheap. Even L-Pads for the mids and highs.
None of these changes would be expensive. Afterwards, you could end up with a very decent speaker. Especially for HT.
Good luck.
Also, with dual mids, maybe try a MTM layout, with the tweeter centered around ear height. That should improve imaging.
Plus, I like the idea of slightly shifting the crossover points. 500Hz and 5.5KHz aren't the best points for those drivers. Maybe 350Hz and 3.5KHz. And you should at least use some Dayton caps. Good and cheap. Even L-Pads for the mids and highs.
None of these changes would be expensive. Afterwards, you could end up with a very decent speaker. Especially for HT.
Good luck.
NeonDriver
Well-Known Member
Since you mentioned open baffle several time, give it a quick try. Take a sheet of cardboard maybe 2x3' and mount the woofer in the cardboard slightly off center and see if makes decent sounding bass. If so, then you might have good candidates for open baffles.
Have you tried spraying the pots with deoxit just so you don't have to deal with them getting noisy so often.
If someone has a pair for sale in CT I might be interested in taking a look at them. I like the challenge of taking them to another level.
Do you know if this is the correct schematic for the crossover?
http://911manuals.com/preview/Infinity/Sm152.png
What are the DC resistances of the drivers?
Have you seen these mods?
http://myhobbiesandprojects.blogspot.com/p/infinity-sm-150-modifications.html
I would start by bracing the box.
Then fill the top 1/3 of the box with damping material, pack polyfill in there.
Line the rest of the box but put nothing close to the port.
Is there a test report showing the input impedance, do we know the port tuning frequency?
I'd lengthen the port for a 32 Hz tuning if it is tuned higher stock.
If someone has a pair for sale in CT I might be interested in taking a look at them. I like the challenge of taking them to another level.
Do you know if this is the correct schematic for the crossover?
http://911manuals.com/preview/Infinity/Sm152.png
What are the DC resistances of the drivers?
Have you seen these mods?
http://myhobbiesandprojects.blogspot.com/p/infinity-sm-150-modifications.html
I would start by bracing the box.
Then fill the top 1/3 of the box with damping material, pack polyfill in there.
Line the rest of the box but put nothing close to the port.
Is there a test report showing the input impedance, do we know the port tuning frequency?
I'd lengthen the port for a 32 Hz tuning if it is tuned higher stock.
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I dunno, Doug. The system sensitivity on those is listed as 102dB (probably a bit optimistic, but still pretty high). I haven't seen a TB mid/woofer that was higher than about 87 or so. It would take a whole herd of mids to get that up to match the rest of the system.
James, can't remember where in Ky you are (Lexington area?) but I'm only about 10 or 15 miles from the west side of the state. If you want to play sometime, let me know, throw them in the family truckster, and we'll do some damage.
Zilch would measure the drivers, both impedance and frequency response. Then he would simulate the woofer in the box and see what needed to be changed to get them to match as nicely as possible. Then he would simulate and redesign crossovers for the mids and tweeter. He was pretty vocal about eschewing comb filtering so he would try to drive down the mid/tweeter XO as low as possible, like Gordon said.
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