Salvage project
Reviving an old thread, I built the doubled up version of the MLTL from the dimensions found in post #24. However, I placed the drivers on the front and back and wired them in parallel. The results are less than great.
The drivers (made in Taiwan not Thailand) are very dark sounding and beam. The speakers, however, are not bassy. There is bass but subjectively much less than my little BIBs with Fostex fe108es. They are also fatiguing even though there is little treble. The room is quite large, about 50sq meters and 4m high, and the amps used are a First Watt F2 and a tpa3116.
Any suggestions? I used the Acousta Stuff in the amount recommended. The cabs are built from 2.2 cm poplar ply.
Some pics:
Comparison with fe108es BIB
I know, I had just received my Kreg Pocket hole jig and went a little overboard!
Reviving an old thread, I built the doubled up version of the MLTL from the dimensions found in post #24. However, I placed the drivers on the front and back and wired them in parallel. The results are less than great.
The drivers (made in Taiwan not Thailand) are very dark sounding and beam. The speakers, however, are not bassy. There is bass but subjectively much less than my little BIBs with Fostex fe108es. They are also fatiguing even though there is little treble. The room is quite large, about 50sq meters and 4m high, and the amps used are a First Watt F2 and a tpa3116.
Any suggestions? I used the Acousta Stuff in the amount recommended. The cabs are built from 2.2 cm poplar ply.
Some pics:
An externally hosted image should be here but it was not working when we last tested it.
Comparison with fe108es BIB
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I know, I had just received my Kreg Pocket hole jig and went a little overboard!
OK, so for the record, did you make the 45” x 9.5” x 6” dims outside [o.d.] or inside [i.d.]?
Port = 2” dia. or is it larger since the baffle thickness is > 19 mm? It looks to be higher up than spec’d also.
Also, did you use an inductor to roll off the rear driver’s mids/HF output? The lack of perceived tonally balanced bass strongly implies you either didn’t or used one that allows way too much mids/HF output to ‘leak’ through. Also, near wall mounting will preload it, varying with frequency, which will not only make the bass sound even weaker, but make the HF sound rolled off with even more beaming than it already has by design due to excessive mids/lower HF emphasis.
All that said, manufacturers have a habit of replacing drivers with inferior performing ones, so while you can solve most of your problems by tonally balancing the driver pairs over a very wide BW, they may still not perform as well overall in the HF as the older versions, same as happened to the RS 40-1354 over time.
One tweak that often improves whizzer cone driver sound quality [SQ] is the $0.98 mod.: Modifications
Also, did you chamfer out the rear the driver baffle mounting holes > 45 deg and preferably > 60 degs? Deep baffles can shroud the driver’s rear output enough to audibly ‘color’ it.
Ditto mass [pre]loading the driver with a fixed or adjustable brace, which can work wonders on flimsy stamped frame drivers:
GM
Port = 2” dia. or is it larger since the baffle thickness is > 19 mm? It looks to be higher up than spec’d also.
Also, did you use an inductor to roll off the rear driver’s mids/HF output? The lack of perceived tonally balanced bass strongly implies you either didn’t or used one that allows way too much mids/HF output to ‘leak’ through. Also, near wall mounting will preload it, varying with frequency, which will not only make the bass sound even weaker, but make the HF sound rolled off with even more beaming than it already has by design due to excessive mids/lower HF emphasis.
All that said, manufacturers have a habit of replacing drivers with inferior performing ones, so while you can solve most of your problems by tonally balancing the driver pairs over a very wide BW, they may still not perform as well overall in the HF as the older versions, same as happened to the RS 40-1354 over time.
One tweak that often improves whizzer cone driver sound quality [SQ] is the $0.98 mod.: Modifications
Also, did you chamfer out the rear the driver baffle mounting holes > 45 deg and preferably > 60 degs? Deep baffles can shroud the driver’s rear output enough to audibly ‘color’ it.
Ditto mass [pre]loading the driver with a fixed or adjustable brace, which can work wonders on flimsy stamped frame drivers:
GM
Attachments
Thanks for the quick, comprehensive reply! I used the interior dimensions recommended, but used 122cm for the height with an internal divider to keep the internal height and port distance the same. The port is 2" in diameter but the baffle thickness is 22mm. Not sure if that would make much of a distance.
I have no inductor added.
When listening to the speakers I pull them a little over 1m from the back wall, although in my new room this has become more annoying. If I were to roll off the back driver, could the speakers then be pushed back up against the wall or would I have to place both on the front (complicating the fix)?
The drivers are made in Taiwan - I remember reading somewhere that the quality went down with the move in production to Thailand. I have a pair of Fostex horn tweeters that I could add if I can get these to perform to a decent level.
I have chamfer the cutout approx. 45º. Will definitely try the $.98 cent mod (.89€ mod?) and the bracing, although more complicated with the drivers directly behind one another.
I have no inductor added.
When listening to the speakers I pull them a little over 1m from the back wall, although in my new room this has become more annoying. If I were to roll off the back driver, could the speakers then be pushed back up against the wall or would I have to place both on the front (complicating the fix)?
The drivers are made in Taiwan - I remember reading somewhere that the quality went down with the move in production to Thailand. I have a pair of Fostex horn tweeters that I could add if I can get these to perform to a decent level.
I have chamfer the cutout approx. 45º. Will definitely try the $.98 cent mod (.89€ mod?) and the bracing, although more complicated with the drivers directly behind one another.
No, the extra port length isn't enough to be audible, I was just curious.
You need the inductor or equivalent EQ no matter what, but it will allow you to place the speaker near the wall, which will affect at what frequency the rear driver needs to begin rolling off.
Yes, for folks with keen HF hearing, many so called 'FR' drivers need a super tweeter, especially if listened to off axis.
Actually, in-line bipoles are easy to preload, just hot melt or caulk 'glue' on a length of closet rod, PVC or heavy cardboard pipe or similar to the front driver's magnet just long enough that there's a very small gap between the rear driver and baffle once tightened down, then either make a soft material gasket to suit or just caulk it.
GM
You need the inductor or equivalent EQ no matter what, but it will allow you to place the speaker near the wall, which will affect at what frequency the rear driver needs to begin rolling off.
Yes, for folks with keen HF hearing, many so called 'FR' drivers need a super tweeter, especially if listened to off axis.
Actually, in-line bipoles are easy to preload, just hot melt or caulk 'glue' on a length of closet rod, PVC or heavy cardboard pipe or similar to the front driver's magnet just long enough that there's a very small gap between the rear driver and baffle once tightened down, then either make a soft material gasket to suit or just caulk it.
GM
Thanks again!
So when calculating the inductor I can't just use 395hz (Baffle Step with baffle width of 11.5")? Ideally I would like to have these pushed back against the wall or nearly so.
Am I looking for a 6db roll off? I get a 3.2mH inductor and an 8 ohm resistor. Does that look about right?
Any thoughts on using a cap instead of an inductor like in this thread:
Best Sounding Single Drivers
It looks like I would have to wire the speakers up in series for a 16ohm load though.
Sorry for the very basic questions...
So when calculating the inductor I can't just use 395hz (Baffle Step with baffle width of 11.5")? Ideally I would like to have these pushed back against the wall or nearly so.
Am I looking for a 6db roll off? I get a 3.2mH inductor and an 8 ohm resistor. Does that look about right?
Any thoughts on using a cap instead of an inductor like in this thread:
Best Sounding Single Drivers
It looks like I would have to wire the speakers up in series for a 16ohm load though.
Sorry for the very basic questions...
It would be really helpful to have a microphone measurement. Even the built in mic on your laptop and REW is better than nothing. It sounds like you may need a BSC circuit. Although bipoles usually don't need BSC but could be as GM says about mids and HFs leaking out the back and making sound too fatiguing. You should have good bass if the TS parameters are close as I would imagine MLTL like this should hit 60Hz easy.
Move farther from wall - at least 5ft for bipole to work otherwise there is a back wall reflection that causes a huge cancellation around 150Hz to 200Hz (according to typical sims of bipoles that Inhave done). The farther the better.
Move farther from wall - at least 5ft for bipole to work otherwise there is a back wall reflection that causes a huge cancellation around 150Hz to 200Hz (according to typical sims of bipoles that Inhave done). The farther the better.
You're welcome!
Not IME since the wall loading impacts it; plus, and more importantly, we're not you [or who you may be accountable to] nor do we have your room, electronics combo, so while we all hear fundamentally the same, we don't all perceive sound reproduction the same, though of course short of accurate measurements, using MJK's or similar BSC design routines is a good place to start and adjust as required.
Again, its roll off slope depends on needs of the app, though 1st order is usually sufficient when the best overall performing XO point is found.
Never read/heard anything WRT using caps to roll off the HF, only to enhance it, so will have to research it as time permits. Hopefully, someone knowledgeable will chime in.
Why would you wire the drivers in series?
GM
Regarding using a cap and wiring the drivers in series, here is the relevant quote from Danny Richie in an old Audiocircle thread:
This was suggested using the FR-125 drivers in what looks to be a narrower bipolar mltl so perhaps not relevant. And the caps look to run nearly as much as the Monacors so experimenting could be too pricey.
This was suggested using the FR-125 drivers in what looks to be a narrower bipolar mltl so perhaps not relevant. And the caps look to run nearly as much as the Monacors so experimenting could be too pricey.
Thinking about what I could have done wrong in the build I am questioning how I stuffed the cabs. Is it .5lbs ft/ft3 using the entire cab volume which would calculate to .74lb stuffing per cabinet or only the volume from top to 28" down which would calculate to .46lb stuffing.
As I understood it I placed the teased stuffing from the top of the cabinet to 28" down, where I placed a fine screen to hold the stuffing from falling down. I used the larger quantity of stuffing. Have I done this correctly? Thanks!
As I understood it I placed the teased stuffing from the top of the cabinet to 28" down, where I placed a fine screen to hold the stuffing from falling down. I used the larger quantity of stuffing. Have I done this correctly? Thanks!
Hmm, all things considered, I'll stick with the inductor, especially since you have an F2 [he says 'green' with envy].
GM
Yes
That said, it seems like every design I did where folks followed the stuffing density and reported back, preferred less, sometimes even when suggesting 0.2-0.25 lbs/ft^3, so finally just recommended 'damping to 'taste''.
FWIW, except for some ~aperiodic alignments where I packed the cabs with R-19 or higher fiberglass insulation, all my cabs were just lined with 1" acoustic fiberglass insulation [AKA Owens-Corning 703 'duct board' nowadays] at the top [i.e. wall opposite the port], one side and back for sealed, reflex and down ~60% for [ML]TLs.
GM
Yes
That said, it seems like every design I did where folks followed the stuffing density and reported back, preferred less, sometimes even when suggesting 0.2-0.25 lbs/ft^3, so finally just recommended 'damping to 'taste''.
Thanks! I will try removing some stuffing but I think the real "culprit" is the lack of BSC. Is it still referred to as baffle step if I am trying to create a 1.5 way?
After reading MJK's article on BSC it looks as if lower amounts may be more appropriate (and less expensive) to start with. I understand it is difficult to "guess" what may work for someone else's situation but does a 1.8mh inductor and a 5ohm resistor looks "better"?
Would this allow me to push it closer to a back wall? It also appears that a cap would help with some of the missing HF, although I am tempted to wire in the FT17's I have lying around.
update
I have been using these as my main speakers for a few months now and have made some progress. The mods GM suggested have made a subtle but noticeable improvement, especially the dowel joining the magnets of the drivers. The drivers have also opened up a bit with more bass and some more high frequencies. Still a dark sounding speaker but very natural sounding with good bass.
I was able to move the speakers 1.5 meters from the back and side walls and I can now appreciate the potential of the speakers. Pulled out this far the shoutiness is gone and I actually had goose bumps listening to Okkervil River the other night.
As this placement is not a long term solution I would like to place both drivers on the front baffle and push them against a wall. I will then add the inductor to roll off one driver.
Would placing the other driver on top (or below) of the existing hole negatively affect the sound of the speakers? This would move the zdriver by nearly 3". This would change the driver position from 24% line length to either 18% or 31%. Thanks for any help.
I have been using these as my main speakers for a few months now and have made some progress. The mods GM suggested have made a subtle but noticeable improvement, especially the dowel joining the magnets of the drivers. The drivers have also opened up a bit with more bass and some more high frequencies. Still a dark sounding speaker but very natural sounding with good bass.
I was able to move the speakers 1.5 meters from the back and side walls and I can now appreciate the potential of the speakers. Pulled out this far the shoutiness is gone and I actually had goose bumps listening to Okkervil River the other night.
As this placement is not a long term solution I would like to place both drivers on the front baffle and push them against a wall. I will then add the inductor to roll off one driver.
Would placing the other driver on top (or below) of the existing hole negatively affect the sound of the speakers? This would move the zdriver by nearly 3". This would change the driver position from 24% line length to either 18% or 31%. Thanks for any help.
Well, along a pipe, all locations will affect its undamped performance, so all of the preferred locations are viable, they just may need different stuffing densities to sound smooth, though 'smooth' with higher densities can 'kill' too much of it 'liveliness' for some folks.
With that in mind, these are the common choices:
~even order harmonics, though these are better suited to tapered pipes IME_ 0.25, etc.
~odd order harmonics_ 0.33, 0.2, 0.143, etc.
MJK's 0.349 offset
my proprietary offset based on CSA:height ratio, which is 0.354 in your case
So.... ~31% is the nearest, but since the driver will be rolled off fairly low, shifting it to either ~0.354 or even 0.4 would be my choice and make the one on top the rolled off one to both lower the floor bounce frequency, amplitude and have the 'FR' in the 'smoother' position and tilt it back as required [damp rear of cab if near a wall/corner] to offset as much HF 'darkness' as practical. That, or cap off a 3/4" [preferably smaller] super tweeter as required. I imagine one of those little 'bullet' mobile audio tweeters will perform well, at least the original Infinity Kappa series did.
GM
With that in mind, these are the common choices:
~even order harmonics, though these are better suited to tapered pipes IME_ 0.25, etc.
~odd order harmonics_ 0.33, 0.2, 0.143, etc.
MJK's 0.349 offset
my proprietary offset based on CSA:height ratio, which is 0.354 in your case
So.... ~31% is the nearest, but since the driver will be rolled off fairly low, shifting it to either ~0.354 or even 0.4 would be my choice and make the one on top the rolled off one to both lower the floor bounce frequency, amplitude and have the 'FR' in the 'smoother' position and tilt it back as required [damp rear of cab if near a wall/corner] to offset as much HF 'darkness' as practical. That, or cap off a 3/4" [preferably smaller] super tweeter as required. I imagine one of those little 'bullet' mobile audio tweeters will perform well, at least the original Infinity Kappa series did.
GM
Thanks GM! Very helpful.
I will go with the zdriver centered at .354, so second driver down 20.86" from top. Is this correct? That separates the drivers quite a bit but I guess comb filtering won't be an issue as the top driver gets rolled off.
I have a pair of ft17h lying around -- will these work?
Once wired up I will try out REW on my laptop as xrk suggested to see if I can nail down the baffle step point for the inductor.
I will go with the zdriver centered at .354, so second driver down 20.86" from top. Is this correct? That separates the drivers quite a bit but I guess comb filtering won't be an issue as the top driver gets rolled off.
I have a pair of ft17h lying around -- will these work?
Once wired up I will try out REW on my laptop as xrk suggested to see if I can nail down the baffle step point for the inductor.
You're welcome!
Hmm, isn't the internal height 45"? 45*0.354 = 15.93".
The FT is kind of large, so the spacing will be ridiculously too long for the ideal, but then I'm guessing you just need some top end 'air', in which case you're going to be capping them off at > ~30 kHz, so with our hearing acuity being so poor above ~5 kHz, it will probably be fine, but lashing up a cardboard/whatever OB of the same width as the cab to test before cutting up the cabs is a good plan.
GM
Hmm, isn't the internal height 45"? 45*0.354 = 15.93".
The FT is kind of large, so the spacing will be ridiculously too long for the ideal, but then I'm guessing you just need some top end 'air', in which case you're going to be capping them off at > ~30 kHz, so with our hearing acuity being so poor above ~5 kHz, it will probably be fine, but lashing up a cardboard/whatever OB of the same width as the cab to test before cutting up the cabs is a good plan.
GM
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