Thanks for that attachment, @zobsky. If I had a dollar for every time I referred to that exact paper in the last ~10 years, I could pay for the MTM iteration of this project you hinted at.
Now that all assumes two main things if we’re banking on Gallo’s research and results for the 5LS as our benchmark for success in a Strada MTM line array ( #risky ? ) :
(1) The undisclosed vertical attenuation for CDT’s in the 5LS is the same as in Strada’s: 30° - not less.
(2) There is not significant difference in behavior/performance between CDTII’s (5LS and I think the Ref 3.5/Strada) and CDTIII’s (Strada 2) despite a couple thousand Hz difference between the two.
I think (1) is possible, but would be difficult for me to measure without a 5LS specimen on hand.
I think (2) is theoretically highly unlikely, so to employ the same variation as used in an older model expecting similar results makes me fear exactly what you defined - negative interference from tweeters’ signals intersecting in the near field listening space. With my current 13.5” spacing, while there must be gaps in the extreme near field (where few will listen), it takes more distance from the speakers to suffer from combing - maybe more distance than is available in my room.
Just the same, if space and money were not an issue, I’d absolutely try it. 8.5-9’ ceiling for 12 MTM monitors per channel; 12’ ceiling for 16 MTM monitors per channel.
Cost-to-performance ratio of such an approach? Likely not up to snuff with my current rendition. But until someone [else - “I call NOT IT!!!”] tries, all we can do is imagine and assume, hey!? 😁
Can’t do it with the current monitors because if I rotated them 90°, the CDT’s would only have 30° lateral dispersion, but the sudden 180° vertical dispersion would create problems a few pieces of felt would probably not cover [line array pun #3].
The other issue is WAF goes out the window with MTM. In my case it could be literal, as the big window behind my speakers slides open floor-to-ceiling - if I switched from a version that is 5” wide, to a version that is 13.5” wide (x2 channels, mind ya), in a 13’ wide room, I worry she’d have me grabbing at edges of those open windows lookin’ like a cat forced into a sink bath! 😹
I’m guessing the HPF in the TR3-D sub is more geared for the small satts Gallo specializes in, which would make the tendency to recommend Strada’s run full range sensible.
Seeing this depicted on your thread is interesting! Your setup looks very near-field, especially at the desk, so while it’s no workaround for the bass issue I find, it’s something I’ll probably try if I get another pair of subs. I see that originally you had each pair suspended horizontally, centered underneath and perpendicular to your array; other than the present vertical orientation being in contact with the floor, did you find either way to be optimal? I’ve never seen “budget bass” produced with this dual opposing woofer approach - I would’ve suspected the timing to be more of an issue with cheap amplification and/or thin plastic housings. Wow. Go little D-class amps, GO! I hope they never kick the bucket.
The inverted V setup you mention is used successfully with Gallo Strada 2’s, and also Ref 3’s, it seems:
…but theirs (Mapleshade; Omega Micro, respectively) are reeeally esoteric setups, and even with my considerable respect for woodwork and craftsmanship, don’t fit into any version of what I want out of in-home music playback.
With any line array, even a unidirectional one, leaning it should change the nature of how reflections are produced not only from the walls, but also the floor/ceiling boundaries. I used my x2 Strada benches this way when I broke in the last 4 Strada’s, leaned back by perhaps 10-15°, as they were on the floor under a high ceiling. Even after break-in, things didn’t sound right. Not bad, just not right.
I won’t reduce the length of this array. That it fits perfectly between wood floor and wood ceiling crossbeam is too much kismet to squander 😉 and the larger-than-life sound I get… it’s a lotta fun to watch people walk into an 11’ ceiling apartment that seems huge (by local habitat standards), only to be further dumbfounded by a sound they can’t comprehend comes from such-a-suddenly-seemingly-small space.
Now if ever the chance arose to mount another dozen Strada's down the backsides of these 90° Gallo’s poles and play with phase etc. … 🧐🤔
With my subs, I think the horizontal suspended version sounded better than the vertical floor standing version but I think that was mainly due to less interaction with the floor and probably room placement rather than the horizontal/vertical difference.
I understand why you want to keep the floor to ceiling array. I heard a demo of full size Magnepans once and I imagine it’s a similar experience.
I was actually thinking of a horizontal V rather than the vertical Vs shown in your pictures.
So, repeated units of this:
M M
T T
M M
where the angle in the horizontal plane can be varied from something small to 180. Again, not too confident this is a good idea but I’d be interested in trying it, particularly at 180 degrees.
I’ve done a bit of googling of the word ‘dispersion’ and it is in fact used differently in different contexts. You were using it with what is apparently the accepted meaning in the audio context. I was using it somewhat carelessly with an alternative meaning related to the separation of a wave into its constituent frequencies. I think my usage was not appropriate in this context. Hence the misunderstanding.
Tried running the arrays through the subs’ HPFs, but couldn’t to follow your suggestion to the letter. Stereo amp speaker outs —> sub high level (speaker) ins [HPF - 100 Hz] —> sub high level (speaker) outs —> arrays. Sorry if any engineers see that - I probably butchered the symbols and abbreviations for pathways.
The HPF in this sub is not what you recommend. It’s passive, set to 100 Hz, and according to the original, more explicitly detailed manual (2012 vs. 2016 ) for this sub model, is intended for use with small satellite speakers. Their (2012) value recommended for sub takeover from large L/R stereo speakers was 80 Hz. Because the sub’s HPF is 100 Hz (the value needed by AGA small satellites), I’m guessing AGA didn’t expect many folks to be running floor standers through the sub HPF. As my arrays are well off the walls (~3’), a higher crossover closer to 100 Hz seems helpful as judged by ear.
However, even given this, it did not sound good to run the arrays through the subs’ HPFs. There is clearly plenty of sound below 100 Hz coming from those 4” drivers, and that degradation is before even considering what a cheap crossover is doing to the signal.
The extra detail on how your dual-woofer subs are set up is helpful. Thanks again @heb1001.
Next, I’ll run the stereo bass signal to each sub (in other words, make both subs’ output mono) and put them face-to-face on the bench - if their opposing woofers serve to cancel vibrations and improve output quality, it should be audible in mono and mounted horizontally (indirect floor contact, vs. in direct floor contact, grin). If that goes well, it’ll be cause to try vertical / horizontal suspension. Yours is a really neat idea that I wouldn’t have expected to give good results with its bare-bones approach. Love it!
With the subs, they need to be bolted together. Preferably by bolting together the frames of the drivers. The pair of drivers push and pull on each other using the bolts. The vibrations won’t cancel if you just point them at each other without bolting them together. In my case, I stuck them together using plastic tubes and superglue but that was a bit too fragile. Bolts would be better.
Duly noted - makes sense.
The sub model I’m using has 4x 1/4-20 machine screw holes on the long side of the cylinder (where the feet attach):
That won’t be ideal but, as a preliminary test before making a circular harness to attach 2x woofer rims (with grills removed, if that approach would even work here - I’m guessing these Gallo TR3-D subs are heavier than the woofers and plastic buckets you used), seems a more affordable bet.
Or does securing such a limited portion of each cylinder’s circumference seem nonsense in this scenario?
With bolts symmetrical around the circumference of the driver, the bolts would be in pure tension/compression and the resonant frequency would be safely above the sub bandwidth.
With your proposed approach of securing the feet, there will be a bending moment in the wood and the subs are presumably quite heavy so the resonant frequency of the bending could be quite low. It should still work unless the resonant frequency is within the bandwidth of the sub. If the bending mode resonates then it will go wild and maybe snap the wood in the middle. So you need to be careful about that.
With your subs, you can see in the pictures that the grille is held on by bolts around the circumference.
I’d unscrew the circular surround and remove the grille then reattach the circular surround using longer bolts and some tubes as spacers (and washers if necessary).
The length of the tubes should be such that the depth of the new bolts inside the sub is the same as it was before with the old bolts - mustn’t go too deep or they may damage something inside.
That would result in two subs with a raised ring in front of each and no grilles.
Then I’d stick the raised rings together with 3M mounting tape, making sure to get the bolts lined up precisely.
So, you’d end up with the subs connected together with bolts, tubes, the two rings and a ring of 3M mounting tape in the middle. The rings in the middle of the gap would protect the drivers a bit, depending on how wide the gap was.
You need to check that whatever the bolts are going into is strong enough to support the weight of the subs before you try to suspend them from the middle. You don’t want to rip the bolts out and damage the subs by accident.
Also make sure to disconnect from the mains and discharge any power supply capacitors before opening up the subs so you don’t get electrocuted.
I’d unscrew the circular surround and remove the grille then reattach the circular surround using longer bolts and some tubes as spacers (and washers if necessary).
The length of the tubes should be such that the depth of the new bolts inside the sub is the same as it was before with the old bolts - mustn’t go too deep or they may damage something inside.
That would result in two subs with a raised ring in front of each and no grilles.
Then I’d stick the raised rings together with 3M mounting tape, making sure to get the bolts lined up precisely.
So, you’d end up with the subs connected together with bolts, tubes, the two rings and a ring of 3M mounting tape in the middle. The rings in the middle of the gap would protect the drivers a bit, depending on how wide the gap was.
You need to check that whatever the bolts are going into is strong enough to support the weight of the subs before you try to suspend them from the middle. You don’t want to rip the bolts out and damage the subs by accident.
Also make sure to disconnect from the mains and discharge any power supply capacitors before opening up the subs so you don’t get electrocuted.
Last edited:
All good suggestions.
Mounting these subs with tape and/or suspending them from the harness will not be an option, though. Two subs together will weigh 25 kilos and the faceplate screws are many (x8), but thin.
I’m also doubtful that the internal weight is evenly distributed down the midline of each sub’s cylinder, so center suspension could wind up lopsided.
These are issues with my DIY “hackery” via pre-assembled components, as opposed to starting from the ground up (or in your specific case @heb1001, ceiling beam down), hey?
If I suspend two conjoined subs, it will need to be vertically, with a specialty double-frame, probably steel and tension cables (think yachting rig works…). Or from a shared runner to which the feet mount, in turn suspended from something larger. At those points, I’d be so far away from modular subs that I don’t know how I could possibly validate it. But the wheels are still turning 😉
Your subs are quite a lot heavier than I thought. The 3M
The tape I was thinking of will only hold 5kg per 30cm so you are right, it probably wouldn’t be sufficient. I didn’t realize your subs were so heavy. I think mine were at most a couple of kilos before I added the sand.
Yes, these are quite efficient subs (300w continuous; 600w peak, perform fast and clean in an all-concrete building; level never turns past 25% when they’re hooked up for HT), and also very dense!
Normally I’d be more interested in following the default approach of stacking 2-3 units per channel to match the Strada arrays, but I didn’t realize bracing subs in opposition could [potentially] give satisfactory results without special programming for timing etc. As you said, there are some extremely $ophistocated subs out there using this approach.
Even if the appearance / lack of modularity ultimately doesn’t permit me keeping said approach, I really want to try it. There is affordable steel work in HK (construction here relies much more on steel tubing than lumber…), so that’s not out of the question for sake of research. Just a question of whether I could find someone to do custom plate-cutting and welding for the woofer-woofer harness, for less than the cost of a third sub 😉
Normally I’d be more interested in following the default approach of stacking 2-3 units per channel to match the Strada arrays, but I didn’t realize bracing subs in opposition could [potentially] give satisfactory results without special programming for timing etc. As you said, there are some extremely $ophistocated subs out there using this approach.
Even if the appearance / lack of modularity ultimately doesn’t permit me keeping said approach, I really want to try it. There is affordable steel work in HK (construction here relies much more on steel tubing than lumber…), so that’s not out of the question for sake of research. Just a question of whether I could find someone to do custom plate-cutting and welding for the woofer-woofer harness, for less than the cost of a third sub 😉
Other than the issue of bass drop out at 18’+ (theoretically predictable), I’m finding lower bass to be extremely inconsistent in level among albums, or even tracks. Some tracks have the bass completely underemphasized (e.g. older recordings that were not remastered post-early-vinyl), and some have knock-the-walls-down bass (e.g. remastered stuff from the 80s) at the same amp level, and this in cases where all mids / highs sound quite similar in level among recordings to both my ears and the SPL meter.
I rarely noticed such difference in my previous setup (much smaller room), in which one sub (Lch) was practically in the middle of the front wall and the other (Rch) was wedged into the corner. Differential adjustment of each channel’s sub level solved issues for the MLP ( = couch 7’ from speakers).
In the newer location, both subs are equidistant from all boundaries and, when set evenly and specifically for a given track, prove excellent (to my ears and the SPL meter) in the “sweet zone” from ~3-4’ in front of the speakers to ~18’ - the bar top in photo; in other words, a pretty large space!
Seems fatiguing to make sub level adjustment for each album, though. I assume I didn’t experience this previously, perhaps only because the subs could not properly integrate in a smaller, poorly-laid-out room?
Makes me wonder how many people using full range floorstanders without subs assume their layout / equipment is problematic, when in fact it’s wildly inconsistent bass level among albums. I don’t want to hijack other threads, so I’ll ask here - any input on experiences from those of you who’ve used arrays with or without subs regarding highly variable bass among recordings / masterings? Is it something most just use DSP pre-sets for during playback? I’m betting this issue has come up before.
I rarely noticed such difference in my previous setup (much smaller room), in which one sub (Lch) was practically in the middle of the front wall and the other (Rch) was wedged into the corner. Differential adjustment of each channel’s sub level solved issues for the MLP ( = couch 7’ from speakers).
In the newer location, both subs are equidistant from all boundaries and, when set evenly and specifically for a given track, prove excellent (to my ears and the SPL meter) in the “sweet zone” from ~3-4’ in front of the speakers to ~18’ - the bar top in photo; in other words, a pretty large space!
Makes me wonder how many people using full range floorstanders without subs assume their layout / equipment is problematic, when in fact it’s wildly inconsistent bass level among albums. I don’t want to hijack other threads, so I’ll ask here - any input on experiences from those of you who’ve used arrays with or without subs regarding highly variable bass among recordings / masterings? Is it something most just use DSP pre-sets for during playback? I’m betting this issue has come up before.
I just ran through a list of bass tracks like this one https://www.whathifi.com/features/25-best-tracks-testing-bass and set the level for them. After that left it alone. Some tracks don’t have a lot of bass. That’s the way they are ;-)
Another thing I thought I’d mention is that the £5 car head unit I use with the crossover also includes a timing compensation feature. I don’t use it because my woofers are in line with my tweeters but if you needed it, a second hand car head unit is, again, a cheap way to get it.
Trying to keep as much processing away from the speakers as possible, at least for now.
One other factor I considered about your opposing subs firing horizontally vs. vertically: horizontal alignment of the sub chassis would impart the exact same gravitational force against each opposing motor / tympanum; vertical alignment would render those forces on each to be opposites. Seems like that could be an important difference. The subs sure look cool in vertical alignment, though! 😁
I have to disagree here. 😬 I’m veering off-topic, but this sort of list is exactly what can exacerbate bass inconsistency in playback.
That list of personal prefs is a good way to learn which artists certain audiophile authors enjoy, but the webpage’s purpose seems purely marketing: IP/region-specific ad banners everywhere, and Amazon purchase links for everything. While there’s nothing inherently wrong with that, the page lacks the most important music info for real-world utility: which edition of each album they use as reference. For the purpose they’re suggesting, those details are as crucial as buying a correct textbook edition for a uni class, but would also potentially invalidate the Amazon purchase links ( #kickback_killers )
Forget differences between audio formats; let’s go with their no. 5 choice - Metallica - because it’s been repressed multiple times in CD alone.
Depending on which year/country pressed (or [re]mastered) the media, it will sound different. Sometimes a LOT different.
Sadly, it seems there’s no way to permanently equilibrate bass level for this scenario without considerable pre-processing of the source material, as it’s clearly a source material issue. Sigh.
Before this setup, I too calibrated the subs’ levels with a handful of familiar tracks/formats/pressings, and just accepted the noteworthy shortcomings/inconsistencies of some others. Heck, of course I did - who would want to blindly adjust the subs’ rear-panel level knobs while kneeling under those arrays… depending on the integrity of IKEA MDF boxes!?
Now that I have the issue/luxury of playing music into a much bigger area, with ready visible access to the level dials on both subs, it seems astonishing how previously lackluster albums/pressings/[re]masters (for multiple media formats) can sound great with just tiny twists of sub levels. Or conversely, can fall flat or rattle the room’s steel floor moldings if a tiny twist of the sub level is missing. The need to adjust the stereo amp level —> arrays among albums to maintain the same SPL (of higher frequencies) seems, so far, considerably less.
I guess it’s the whole “With great power comes great responsibility” conundrum. 😅
I hadn’t thought about the effect of gravity. I think you are correct. It must make a difference unless the drivers are perfectly linear.
I’d have them horizontal if I could but there just isn’t space in their current location.
Yes, it’s an unfortunate conflict of alignment/arrangement.
I kept worrying about vertical orientation of my subs as it related to vibrations and, as an engineer friend warned, enlarging the screw (mounting) holes on them over time. Then I thought that kind of uneven force should also apply to woofer movement, potentially affecting timing and throw. The first 10” Gallo subwoofer model was down-firing; all models after that (including bass woofers on their floor-standing speakers) were front/side-firing. Guessing there is more reason behind that, than appearance alone.
So now I’m thinking I’ll keep a horizontal arrangement. If facing woofers together offers an advantage in sound quality, it’ll come at the expense of getting better ( = needed) distance out of their performance - no array benefits. Time will tell which evil is lesser, eh.
No progress in trying it your way yet - many days of unrelenting rain mean no woodwork on the roof, and I’m not doing that indoors a. Too much mess!
Still more rain in the forecast next weekend.
Time will tell.
And just in case anyone who cares didn’t see which other line we are referencing:
https://www.diyaudio.com/community/threads/1-day-ghetto-line-array-build-200.359672/page-4