Wesayso,
I am sorry to hear what happened here. It must be a very difficult time. I agree with Thoglette that we need to understand what happened here. As the threaded rods would have put it in compression and it still cracked it means that something pulled the wood apart other than the rods - the wood itself may have contracted due to the change in humidity. Frost means all relative humidity suddenly changed to low and caused the humidity in the wood to leave - shrinking the wood. The fact that the crack was almost exactly in the middle indicates that the stress pulling the wood apart was even - or originated in the wood itself. Since it was so well bonded, the stress pulled the ply itself apart.
I don't think this is irreparable at all, and may be an opportunity for you to make the system segmented for easier transport, and to avoid future cracks due to humidity. Will it be possible to remove all the threaded rods and do a clean cut and sand the wood at the crack to excise the damaged wood? Then replace the removed material with a sheet of your mass filled polymer/rubber (cut to the same outline as the wood). Perhaps do this in several more places for 4 segments total. This will allow the speakers to be 'taken down' to qnty 4 x 2 ft segments for easy transport/storing etc. And allow for future expansion/contraction joints. You could even accent the contraction/expansion joint by placing a sheet of rubber alternating with a CNC'd sheet of aluminum with a sheet of rubber. Highly polish the aluminum or black anodize the aluminum for a visual appeal. It may even help to reduce cabinet axial resonances in the future.
Whatever you decide to do, I know you will get through this, as you are a very talented engineer/constructor.
Good luck!
I am sorry to hear what happened here. It must be a very difficult time. I agree with Thoglette that we need to understand what happened here. As the threaded rods would have put it in compression and it still cracked it means that something pulled the wood apart other than the rods - the wood itself may have contracted due to the change in humidity. Frost means all relative humidity suddenly changed to low and caused the humidity in the wood to leave - shrinking the wood. The fact that the crack was almost exactly in the middle indicates that the stress pulling the wood apart was even - or originated in the wood itself. Since it was so well bonded, the stress pulled the ply itself apart.
I don't think this is irreparable at all, and may be an opportunity for you to make the system segmented for easier transport, and to avoid future cracks due to humidity. Will it be possible to remove all the threaded rods and do a clean cut and sand the wood at the crack to excise the damaged wood? Then replace the removed material with a sheet of your mass filled polymer/rubber (cut to the same outline as the wood). Perhaps do this in several more places for 4 segments total. This will allow the speakers to be 'taken down' to qnty 4 x 2 ft segments for easy transport/storing etc. And allow for future expansion/contraction joints. You could even accent the contraction/expansion joint by placing a sheet of rubber alternating with a CNC'd sheet of aluminum with a sheet of rubber. Highly polish the aluminum or black anodize the aluminum for a visual appeal. It may even help to reduce cabinet axial resonances in the future.
Whatever you decide to do, I know you will get through this, as you are a very talented engineer/constructor.
Good luck!
Wesayso,
Sorry to see this happen to your lovely tower speakers. But plenty of ideas from the community, and it might be very well possible for you to repair these.
Thinking aloud, maybe you can glue the two pieces together with wood glue (any ideas on how you can create necessary compression/pressure for a good bond?). It is likely that leaks/holes will remain from the craked layers - would application of two part epoxy work to create a seal? Mixed together, most of them form a paste like substance, which you might be able to apply across the length of crack and create a "seal"from the inside.
Sorry to see this happen to your lovely tower speakers. But plenty of ideas from the community, and it might be very well possible for you to repair these.
Thinking aloud, maybe you can glue the two pieces together with wood glue (any ideas on how you can create necessary compression/pressure for a good bond?). It is likely that leaks/holes will remain from the craked layers - would application of two part epoxy work to create a seal? Mixed together, most of them form a paste like substance, which you might be able to apply across the length of crack and create a "seal"from the inside.
For now I kinda forced it back into shape with some wood glue in between. No telling how much glue I got in there though, I could force the bolts on both sides of the stack and noticed a reduction in the seam. So I quickly added glue and went on. All in all it took some time so I do not trust this repair too much. All this while cooking dinner (lol).
I'll spend the next couple of days thinking about how to go forward. I won't quit now!
But they won't be as pretty as they were when I'm done I'm afraid. Might as well think about wrapping them with something strong and going for an all black look.
Right now you can't see it was broken. The weather is about to change again so the pressure on the threaded rods will be huge after this change!
I'll spend the next couple of days thinking about how to go forward. I won't quit now!
But they won't be as pretty as they were when I'm done I'm afraid. Might as well think about wrapping them with something strong and going for an all black look.
Right now you can't see it was broken. The weather is about to change again so the pressure on the threaded rods will be huge after this change!
I think I understand why it happened. The rods would not let the wood contract fast enough causing high stress. The differences in length in a stack like this can be huge. I noticed at least 4 mm difference in length at times.
I'm sure they were in one piece last night. So it all went pretty quick. Every other layer there is glue around the rods. That's probably what was holding back the ends to contract. My reasoning was it would spread the pressure, but I was wrong there. Lesson learned. Move on from here...
If the rods are holding the structure, I would clean up he gap a bit, maybe even enlarge it and fill with some type of silicon or rubber joint compound to create a permanent expansion joint. I would then carefully route or carve a band around the affected part of the enclosure and put some type of flexible inlay to cover the joint.
Major Combing Filtering
Wesayso,
A lovely speakers, one thing that concerns me is that mounting full rangers in a vertical plane causes "Major Combing Filtering", as one respected designer describes it as
“Running two or more of them(FR) in series/ parallel causes some major comb filtering that really destroys the response. Using a line of them running full range is even worse. You wind up with no highs.”
Also a designer from Vaughn speakers also experienced the same effect. Have you experienced this? Vaughn solved this problem by adding a ribbon tweeter on top. See image attached.
Wesayso,
A lovely speakers, one thing that concerns me is that mounting full rangers in a vertical plane causes "Major Combing Filtering", as one respected designer describes it as
“Running two or more of them(FR) in series/ parallel causes some major comb filtering that really destroys the response. Using a line of them running full range is even worse. You wind up with no highs.”
Also a designer from Vaughn speakers also experienced the same effect. Have you experienced this? Vaughn solved this problem by adding a ribbon tweeter on top. See image attached.
Attachments
The Vifa's are small enough that they can be tightly spaced to minimize the comb effect - which shows up at close range. Move back to normal listening position and it is gone. The sims support the measurements that others have made of a 25 driver line array using the Vifa's. it reaches 18 kHz just fine from what we have seen in reported measurements. In the photo above, those look like bigger 4 or 4.5 in drivers and they are not mounted as close together as possible. With proper EQ these speakers are flat from 20 Hz to 18khz.
Last edited:
Hi. I’ve been a professional carpenter and have done a lot of furniture restoration so I feel I have so knowledge to share. I’m confident that with the right approach this can be glued back together without leaving a trace of it ever having happened, as long as you can keep the brake clean and aligned as it is. You’d need a couple of bar clamps of the right length. Even though I’ve never seen them in this length, so a customized set could be an option. If gluing for some reason doesn’t work, then cutting the broken section out and replacing it with a new one would also be possible, but that would obviously mean a lot more refinishing. All in all a major setback in this build, but surely not game-over.
The only question would be, how to prevent this from happening again. The first thing that comes in my mind is to seal the wood inside and out with clear epoxy, the stuff you get at the boat chandler by West here in the Netherlands. If you take the slow curing kind and warm up the wood a little, it will soak up the epoxy like a sponge creating a good moisture barrier and also reinforcing the wood itself.
The only question would be, how to prevent this from happening again. The first thing that comes in my mind is to seal the wood inside and out with clear epoxy, the stuff you get at the boat chandler by West here in the Netherlands. If you take the slow curing kind and warm up the wood a little, it will soak up the epoxy like a sponge creating a good moisture barrier and also reinforcing the wood itself.
Re combing, it does exist in line arrays using wideband drivers. In the HF, with the shorter wavelengths, the individual sources do not / cannot combine into a single radiation. That's just the physics of the situation, and as independent sources they sum, as TD succinctly sets down, per Huygens construction producing an interference pattern depending on the phase angle from each source which is then dependent on the distance to each source at the listening position.
The effects of this are what can case a difference of opinion though. Two general areas:
1/ The 'comb-filter' often referred to, i.e. multiple deep high Q notches of interference pattern.
2/ An apparent reduction in HF SPLs since the individual sources have not summed into a single, unlike those at lower frequencies.
The second can be dealt with via Eq quite easily. Roger Russell's IDS-25 arrays receive this, as described in his AudioXpress articles. There are other examples too. Job-jibbed. Where the main differences of opinion lie are in the first point, i.e. the audibility or lack thereof of the high-Q notches / 'comb' effect. Typically, once the OA response trend has been Eq'd ~flat, if reasonably small drivers have been used & you're not sticking your bonce right up against the array but are at a sensible position -say >1m away, it rarely seems to be an audible issue for many people. Negative feedback seems more likely to be a result of those who simply can't get on with the power-response of an array, period, or for whom the inherent HF performance of wideband drivers isn't on a par with, say, a quality dome or ribbon tweeter.
The Vaughn cabinet is very short, and arrays are highly directional, vertically (i.e. you move off the vertical axis & the HF will appear to vanish). Less of an issue / not an issue for longer arrays, but a problem for shorter types, which will be why they have added the ribbon.
The effects of this are what can case a difference of opinion though. Two general areas:
1/ The 'comb-filter' often referred to, i.e. multiple deep high Q notches of interference pattern.
2/ An apparent reduction in HF SPLs since the individual sources have not summed into a single, unlike those at lower frequencies.
The second can be dealt with via Eq quite easily. Roger Russell's IDS-25 arrays receive this, as described in his AudioXpress articles. There are other examples too. Job-jibbed. Where the main differences of opinion lie are in the first point, i.e. the audibility or lack thereof of the high-Q notches / 'comb' effect. Typically, once the OA response trend has been Eq'd ~flat, if reasonably small drivers have been used & you're not sticking your bonce right up against the array but are at a sensible position -say >1m away, it rarely seems to be an audible issue for many people. Negative feedback seems more likely to be a result of those who simply can't get on with the power-response of an array, period, or for whom the inherent HF performance of wideband drivers isn't on a par with, say, a quality dome or ribbon tweeter.
The Vaughn cabinet is very short, and arrays are highly directional, vertically (i.e. you move off the vertical axis & the HF will appear to vanish). Less of an issue / not an issue for longer arrays, but a problem for shorter types, which will be why they have added the ribbon.
Last edited:
Thanks guys for saving me the trouble of acknowledging the existence of comb filtering in a line array like this. Yes, I am fully aware of that fact and the above reply does a good job of explaining the effects and a partial cure for it (read EQ).
I know what I'm getting myself in to in this regard. Somehow that isn't my main concern right now
.
Thanks for your insight Stijn, and all others that profided ideas and solutions for that matter! I won't quit now. Taking a day or two to examine my possibilities.
The tower is fixed for now, with hardly any evidence it happened in the first place. I was able to force the 2 parts back together slowly by turning the nuts at both sides (equal turns) and taking my time doing that. I'm not convinced the amount of glue I got in there is sufficient though. If I do not do anything else it will happen again I'm afraid.
Stijn, For the epoxy to work, I have to sand down the polyurethane clear coat right? Can I re-apply the stain I used? I'm thinking of using woven glass matt with the epoxy as a laminate to strengthen the enclosure. That was my original plan in the first place. I should have just went with that but tried to take an easy way out after reading success stories from translam constructions using polyurethane coatings. But I have no idea if they used threaded rods in their stacks. And I am pretty sure their stacks were smaller!
My problem is the temperatures are going down quickly outside. At best I can heat my garage 5 degrees more than the outside temperature. No real heating, just a small heater. I can't afford any better right now. So do I wait till spring to finish this? It would almost kill me to wait that long!
The thinner matt clears up with wetting by epoxy leaving me with an equal finish I have now. Still needs a clear coat for UV protection.
I even consider using a carbon/aramid matt although very expensive but that would make a possible finish. Plus the aramid fiber is a very strong fiber in the pull direction. Much stronger than glass matt.
How can I get myself to be patient enough to wait till spring
...
With a material like carbon/aramid I would have to wait. No point in experimenting with faster harder's (for lower temperatures) on a material of that price.
I'll think it over and any advice is welcome, good advice even better!
I know what I'm getting myself in to in this regard. Somehow that isn't my main concern right now
.Thanks for your insight Stijn, and all others that profided ideas and solutions for that matter! I won't quit now. Taking a day or two to examine my possibilities.
The tower is fixed for now, with hardly any evidence it happened in the first place. I was able to force the 2 parts back together slowly by turning the nuts at both sides (equal turns) and taking my time doing that. I'm not convinced the amount of glue I got in there is sufficient though. If I do not do anything else it will happen again I'm afraid.
Stijn, For the epoxy to work, I have to sand down the polyurethane clear coat right? Can I re-apply the stain I used? I'm thinking of using woven glass matt with the epoxy as a laminate to strengthen the enclosure. That was my original plan in the first place. I should have just went with that but tried to take an easy way out after reading success stories from translam constructions using polyurethane coatings. But I have no idea if they used threaded rods in their stacks. And I am pretty sure their stacks were smaller!
My problem is the temperatures are going down quickly outside. At best I can heat my garage 5 degrees more than the outside temperature. No real heating, just a small heater. I can't afford any better right now. So do I wait till spring to finish this? It would almost kill me to wait that long!
The thinner matt clears up with wetting by epoxy leaving me with an equal finish I have now. Still needs a clear coat for UV protection.
I even consider using a carbon/aramid matt although very expensive but that would make a possible finish. Plus the aramid fiber is a very strong fiber in the pull direction. Much stronger than glass matt.
How can I get myself to be patient enough to wait till spring
...With a material like carbon/aramid I would have to wait. No point in experimenting with faster harder's (for lower temperatures) on a material of that price.
I'll think it over and any advice is welcome, good advice even better!
I'm not certain it's added strength from a coating (be it fibreglass or whatever) that you would obtain or even need so much as some degree of protection from differential changes in temperature & humidity in the wood and supporting metal rods. It should help to a degree with those, providing the coating is complete, & you can as far as possible keep exposures to such changes as minimal & gradual as possible.
Impossible to Eq for off axis only....
This really puzzles me....
As a long term user of many DSP and analog crossover and Eq / filter software programmes, from Behringer to Dolby Lake with DEQX and DBX etc in between....
Please tell me which piece of kit or Eq software has the ability to Eq for off axis without affecting the on axis response? This is mega if you know how!
When I say response I mean both Frequency and phase / time, but just to keep it simple ( for my benefit!) please deal with frequency response first.
I read a lot of this sort of stuff where the poster is just repeating / quoting from the usual suspects with commercial interests in selling their own particular "patented techniques..." Hopefully you have discovered the Silver Bullet!
Given the right driver, cabinet, damping and location, in my experience, Line Arrays offer the best all round solution for domestic reproduction of music / movie soundtracks.
Thanks in advance
D.
This really puzzles me....
As a long term user of many DSP and analog crossover and Eq / filter software programmes, from Behringer to Dolby Lake with DEQX and DBX etc in between....
Please tell me which piece of kit or Eq software has the ability to Eq for off axis without affecting the on axis response? This is mega if you know how!
When I say response I mean both Frequency and phase / time, but just to keep it simple ( for my benefit!) please deal with frequency response first.
I read a lot of this sort of stuff where the poster is just repeating / quoting from the usual suspects with commercial interests in selling their own particular "patented techniques..." Hopefully you have discovered the Silver Bullet!
Given the right driver, cabinet, damping and location, in my experience, Line Arrays offer the best all round solution for domestic reproduction of music / movie soundtracks.
Thanks in advance
D.
Sorry about your hard work going a little south.I have had a few large projects were handed to me a few years ago to see if I could fix.
These were cracking so bad from moisture after coming to me it was unreal.Cracking got so bad I ened up using 2 gallons of Bondo scraping it on with a 2x4. Then reclanding them with 1/4" plywood on the exterior.
Here is a photo showing the top lag bolts around them.Then another 2 layers of Baltic Birch were placed on the top.
What I found was the torque from the bolts made it WORSE. Do not put compression on the wood.For long periods.It is different to clamping them to hold during glue drying.
In the end they worked out Great but with 3.5" thick they weighted over 280lbs and my customer got a moving company for the pick up and delivery to his place.Thankfully
Now the large arrays I did for the same customer used the same method stacked and bolted MDF baltic layered.This array was for 12AC G1 ribbons with Accuton Mids Open baffled sitting onto of 4 TC 12" woofers then the large subs in the corners with 21" Aura's
Notice the curve that happened to the cabinet
Here is them close to finished with a lot of cutting needed to get them to look like this.Book matched Paduke veneer.The outer stack was done for acoustic then the large panels the ribbons mounted to open back then the panel for the Accuton mids matching them together. This all sits on a W set of TC 12" subs OB.
In the end took my spare time over 3yrs to build as I did them
I hope you can make them work in the end but having the wood not sealed on both sides was the big thing I did in the end.
All the best
These were cracking so bad from moisture after coming to me it was unreal.Cracking got so bad I ened up using 2 gallons of Bondo scraping it on with a 2x4. Then reclanding them with 1/4" plywood on the exterior.
Here is a photo showing the top lag bolts around them.Then another 2 layers of Baltic Birch were placed on the top.
What I found was the torque from the bolts made it WORSE. Do not put compression on the wood.For long periods.It is different to clamping them to hold during glue drying.
In the end they worked out Great but with 3.5" thick they weighted over 280lbs and my customer got a moving company for the pick up and delivery to his place.Thankfully
Now the large arrays I did for the same customer used the same method stacked and bolted MDF baltic layered.This array was for 12AC G1 ribbons with Accuton Mids Open baffled sitting onto of 4 TC 12" woofers then the large subs in the corners with 21" Aura's
Notice the curve that happened to the cabinet
Here is them close to finished with a lot of cutting needed to get them to look like this.Book matched Paduke veneer.The outer stack was done for acoustic then the large panels the ribbons mounted to open back then the panel for the Accuton mids matching them together. This all sits on a W set of TC 12" subs OB.
In the end took my spare time over 3yrs to build as I did them
I hope you can make them work in the end but having the wood not sealed on both sides was the big thing I did in the end.
All the best
Ok Pulse back to normal...!
Thanks Scott,
For a few glorious moments I thought you had found the Holy Grail....!
Ah well, best put on my Indiana Jones hat and resume the quest!
Cheers
D.
Thanks Scott,
For a few glorious moments I thought you had found the Holy Grail....!
Ah well, best put on my Indiana Jones hat and resume the quest!
Cheers
D.
Oh, I read you left the rods in there......
I'd put a penny on the rods expanding and, being effectively glued in have expanded caused by the move from 'cold' to 'hot'.
Also the enclosure is 'Horseshoe' shaped, this would make it susceptible to rotational stresses
Throw in a 'bad lamination', looks like that piece had a few voids, and throw in 'transport' stresses.......
I would fix them by finding some one with a decent size band saw and chop them in half - remove enough material so each 'half' can have a bottom / top glued on.
I'd put a penny on the rods expanding and, being effectively glued in have expanded caused by the move from 'cold' to 'hot'.
Also the enclosure is 'Horseshoe' shaped, this would make it susceptible to rotational stresses
Throw in a 'bad lamination', looks like that piece had a few voids, and throw in 'transport' stresses.......
I would fix them by finding some one with a decent size band saw and chop them in half - remove enough material so each 'half' can have a bottom / top glued on.
Also read OP's bit on 'glassing' them.....
If the same thing happens and there is a layer of glass involved, it will simply delaminate from the cabinet.
Are You prepared to itch for days?
This is a HUGE problem on wooden surfboards, unless the 'shape' is treated correctly for 'grain lift' before laminating, the cloth simply peals away.
Also the resin will heat the structure, it might split again.
Last balsa board I made took - from order to delivery 3 1/2 years, about 12months to find the balsa, 8 months to 'put together' and then about the same time for all the finishing, the rest of the time was spent waiting for the seasons / weather to be right to work.
If the same thing happens and there is a layer of glass involved, it will simply delaminate from the cabinet.
Are You prepared to itch for days?
This is a HUGE problem on wooden surfboards, unless the 'shape' is treated correctly for 'grain lift' before laminating, the cloth simply peals away.
Also the resin will heat the structure, it might split again.
Last balsa board I made took - from order to delivery 3 1/2 years, about 12months to find the balsa, 8 months to 'put together' and then about the same time for all the finishing, the rest of the time was spent waiting for the seasons / weather to be right to work.