I think it's worth trying a few simple crossover mods for an MTM. Cheap entertainment.
We are trying to get near this:
SBA-16-MTM
Is your cabinet separate chambers for the two drivers since it was originally a 2.5? Did you try the Rinjani circuit?
Rinjani - Sbacoustics
Troels uses 20mm plywood for his offset in time aligned solutions. Which is in agreement with Matt's suggestion of 21mm.
SBA-16-MTM
SBA-761
I would guess his tweeter filter is single cap and Fs notch around 700Hz which traditionally gives 12dB per octave.
Much interesting stuff from Troels here about filters on flat baffle and time aligned:
18W-8434G00
We are trying to get near this:
SBA-16-MTM
Is your cabinet separate chambers for the two drivers since it was originally a 2.5? Did you try the Rinjani circuit?
Rinjani - Sbacoustics
Troels uses 20mm plywood for his offset in time aligned solutions. Which is in agreement with Matt's suggestion of 21mm.
SBA-16-MTM
SBA-761
I would guess his tweeter filter is single cap and Fs notch around 700Hz which traditionally gives 12dB per octave.
Much interesting stuff from Troels here about filters on flat baffle and time aligned:
18W-8434G00
#System7, my cabinet is a single chamber. I did not know that for 2 1/2 way they need to be separate lol. I can make the cap change really quick to see if it cleans up the tweeter. When I get back from Vacay I will look at changingf the baffle; So you are saying just make it an MTM rather than a MMT? Should I still set back the tweeter in an MTM? What about a waveguiide?
MTM and MMT work exactly the same on axis, but an MTM has symmetrical lobing. An MMT will sound different above and below axis. Same filter though.
A 2.5 way is an slightly different animal with 3 filter sections, of course.
I double posted the Troels MTM design. What I meant to post was this:
SBAcoustics-61-MFC
Looks like a second order plus LCR Fs resonance correction on the tweeter, with big value capacitor, otherwise why use an electrolytic?
The low pass must be bass coil plus LCR notch at around 6kHz to reduce breakup.
Interesting.
Amusing remark by Troels here in this repeated link:
Didn't someone advise you to buy that one ? 🙄
18W-8434G00
TBH, I thought you had an MMT these days. But waveguide tweeters would save you some complex carpentry.
Waveguides to get time-alignment on a flat baffle? This is a good one, the Morel CAT 378 but it is 94mm:
MOREL CAT 378 Soft Dome Horn Tweeter – AmpsLab
Finch (Morel CAT378 + Vifa PL18W0-09-08) – AmpsLab
Mike Chua is such a pleasant guy he might send you his FRD and ZMA files along with the filter if you ask him nicely.
I don't know the details of the SEAS DXT but another competent waveguide on 104mm:
H1499-06 27TBCD/GB-DXT
Would work on a capacitor and Fs correction, for sure. I think SB do a waveguide too.
A 2.5 way is an slightly different animal with 3 filter sections, of course.
I double posted the Troels MTM design. What I meant to post was this:
SBAcoustics-61-MFC
Looks like a second order plus LCR Fs resonance correction on the tweeter, with big value capacitor, otherwise why use an electrolytic?
The low pass must be bass coil plus LCR notch at around 6kHz to reduce breakup.
Interesting.
Amusing remark by Troels here in this repeated link:
Didn't someone advise you to buy that one ? 🙄
18W-8434G00
TBH, I thought you had an MMT these days. But waveguide tweeters would save you some complex carpentry.
Waveguides to get time-alignment on a flat baffle? This is a good one, the Morel CAT 378 but it is 94mm:
MOREL CAT 378 Soft Dome Horn Tweeter – AmpsLab
Finch (Morel CAT378 + Vifa PL18W0-09-08) – AmpsLab
Mike Chua is such a pleasant guy he might send you his FRD and ZMA files along with the filter if you ask him nicely.
I don't know the details of the SEAS DXT but another competent waveguide on 104mm:
H1499-06 27TBCD/GB-DXT
Would work on a capacitor and Fs correction, for sure. I think SB do a waveguide too.
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Lots of choices. I like the idea of the Morel. Not sure how far it is set back but if I just modify my current baffle that might be easier. Not sure of the performance of the Morel compared to the 29R
OK so I removed the resistor (midrange leg) and replaced the tweeter cap with a 5.6uf. There is definitely an improvement. I think there is a bit of a shelf below 1K that is stronger by about 3 db.
I have a choice to make: Waveguide the tweeter or step it back by redoing the baffle. Any preference?
A step will cause diffraction, so not ideal. I'd go with a waveguide - Well, I'd actually take measurements and design the crossover properly rather than change anything.
I looked but I dont see a waveguide available for my tweeter. Do modelling tools allow you to model a WG or is it done purely by measurement.
Reporting back on the recent upgrades that were suggested on this forum for my speakers. I want to thank all for the suggestions after extended listening sessions they are now performing how I wanted. Note that I did not redo the baffle. Question is is it worth stepping the tweeter back? I can make another baffle but that means major reassembly lol. As we used to say "Is the juice worth the squeeze"
OK I am now ready to disassemble my speakers and make a stepped baffle. How far should the step back be? How do I calculate that?