This winter's DIY-project just arrived.

Re: This winter's DIY-project just arrived.

Ossian Ott said:
When I built my keystones like 2 months ago I used only 90° cuts, polyurethane glue for the two joints in the horn fold(not the bottom one) and regular glue for the rest. No screws only nails. Seem to work good. I'm not too keen overdoing or overcomplicating things(which is why I chose to try the keystone to begin with) and you can easily knock out one cab in a day if you are effective.

I tried them... loaded with 18sw115 is impressive! Very loud and very clean and the extension works well for edm, I had to cross them at 75-80 or they started to sound a bit barky tho, any suggestions how to make it deliver a bit more neutral sounding kick?
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I agree completely with Ivan's response, screws hold up to abuse, and having a speaker that can take 6.6 horsepower (like Helge has) will create a lot of banging sufficient to pull joints apart.

Ossian, not using the correct angles for your cuts and no screws to pull joints together while the glue expands (not a fan of polyurethane glue) may have resulted in leakage responsible for the "barky" sound. That said, with no mention of what your top cabinets and alignment procedure, no frequency response measurements, no way to tell what the problems are that you encountered.

I crossed my Keystones at 100 Hz, 24dB BW, some out of band upper peak reduction and in band EQ to flatten response, then delayed the top speakers for an even phase match, the sound (and frequency and phase measurement) was smooth through the entire "kick" region, as neutral of a sound as any sub/top transition I have heard.

Art
 
Re: This winter's DIY-project just arrived.

Screws it is then :)

I'm not a huge fan of expanding glue either, but it has helped me in the past filling uneven cuts etc.

This time around I'm thinking about dropping it because all the woodwork is done at a much higher standard than I manage to archieve.


Sent from my iPhone
 
Re: This winter's DIY-project just arrived.

Helge Dr. Bentsen said:
Screws it is then :)

I'm not a huge fan of expanding glue either, but it has helped me in the past filling uneven cuts etc.

This time around I'm thinking about dropping it because all the woodwork is done at a much higher standard than I manage to archieve.


Sent from my iPhone
Click to expand...

FWIW, I've had great luck with biscuit joints adding strength to labsubs, etc,

Really cool project you have going !!
 
Re: This winter's DIY-project just arrived.

We used four clamps on each upper horn section when putting them together, very tight with many nails and with excessive PL glue of high quality. 99% certain of no leaks anywhere in the cabs. Gonna check for leaks next time im in the store
 
Re: This winter's DIY-project just arrived.

Mark Wilkinson said:
FWIW, I've had great luck with biscuit joints adding strength to labsubs, etc,

Really cool project you have going !!
Click to expand...
Uneven expansion/contraction of the biscuit joints compared to plywood can cause the glue joint to fail, as I recently found when some continental risers I had built, but never used, fell apart when I took them out of a storage trailer.

Made re-using the wood a lot easier than if I would have used screws...
 
Re: This winter's DIY-project just arrived.

Art Welter said:
I agree completely with Ivan's response, screws hold up to abuse, and having a speaker that can take 6.6 horsepower (like Helge has) will create a lot of banging sufficient to pull joints apart.

Ossian, not using the correct angles for your cuts and no screws to pull joints together while the glue expands (not a fan of polyurethane glue) may have resulted in leakage responsible for the "barky" sound. That said, with no mention of what your top cabinets and alignment procedure, no frequency response measurements, no way to tell what the problems are that you encountered.

I crossed my Keystones at 100 Hz, 24dB BW, some out of band upper peak reduction and in band EQ to flatten response, then delayed the top speakers for an even phase match, the sound (and frequency and phase measurement) was smooth through the entire "kick" region, as neutral of a sound as any sub/top transition I have heard.

Art
Click to expand...

We use Bfm dr280's as tops. There seemed to be a minor dimension error on panel G in the plans on in the keystone thread made by someone, could a very slight difference in the fold make this kind of effect, presuming no leaks? I wonder why I experienced such thing, if I could get them to play to 100 they might very well be perfect cabs.

Also using BW 24

Anyway sorry for the OT! Tell me if my intruding is of disturbance to the OP.
 
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Re: This winter's DIY-project just arrived.

Art Welter said:
Uneven expansion/contraction of the biscuit joints compared to plywood can cause the glue joint to fail, as I recently found when some continental risers I had built, but never used, fell apart when I took them out of a storage trailer.

Made re-using the wood a lot easier than if I would have used screws...
Click to expand...

My understanding of biscuit joints is that the biscuits are primarily alignment aids, and the real strength comes from gluing the entire joint. While gluing the biscuit certainly helps, it is by no means sufficient for a strong joint.
 
Re: This winter's DIY-project just arrived.

Ossian Ott said:
We use Bfm dr280's as tops. There seemed to be a minor dimension error on panel G in the plans on in the keystone thread made by someone, could a very slight difference in the fold make this kind of effect, presuming no leaks? I wonder why I experienced such thing, if I could get them to play to 100 they might very well be perfect cabs.
Click to expand...
A very slight difference in the fold should make only a very slight difference in frequency response. Presuming no leaks, you probably have a phase alignment and equalization issue.
 
Re: This winter's DIY-project just arrived.

Art Welter said:
Uneven expansion/contraction of the biscuit joints compared to plywood can cause the glue joint to fail, as I recently found when some continental risers I had built, but never used, fell apart when I took them out of a storage trailer.

Made re-using the wood a lot easier than if I would have used screws...
Click to expand...

Good to know. And thinking back, much of the "good luck" I attributed to biscuit joints was probably more due to paranoid construction !

Heck, I used biscuits and big bessey clamps for the overnight glue up...and then added screws next day when glue was set. Takes days this way to keep clamping all the joints....but the subs would be hell to break apart..
 
Re: This winter's DIY-project just arrived.

Mark Wilkinson said:
Heck, I used biscuits and big bessey clamps for the overnight glue up...and then added screws next day when glue was set. Takes days this way to keep clamping all the joints....but the subs would be hell to break apart..
Click to expand...

I prefer to drive the mechanical fasteners while the glue is still wet. What would Norm Abram do :?~:-?~:???: ?

Dave
 
Re: This winter's DIY-project just arrived.

When I did house construction I was told the screws are for clamping the piece while the glue sets. Granted most construction is designed to be compression rather than tension so it may lack some basic principles for box design.

Sent from my XT1060
 
Re: This winter's DIY-project just arrived.

Dave Pluke said:
I prefer to drive the mechanical fasteners while the glue is still wet. What would Norm Abram do :?~:-?~:???: ?

Dave
Click to expand...

That's what I do too, when I don't have enough of the right clamps to pull a joint together over its full length. IMO/IME, good clamping techniques greatly increase strength....I really can't see how commercial speaker manufacturers could take the time to fully clamp down :D~:-D~:grin: .... unless they make some kinda big jig rig
 
Re: This winter's DIY-project just arrived.

Here is my process: align panels and clamp in place, pre drill screw holes at a maximum of three inches apart. Then unclamp panels and start screws, allowing the screws to protrude through the first panel slightly. Apply glue to edge and place panel using the protruding screw tip to align , then, run in screws. Clamp joint tight, and then tighten the screws. Finally, reclamp with a piece of angle iron across the joint if possible.
 
Re: This winter's DIY-project just arrived.

Jordan Lahr said:
When I did house construction I was told the screws are for clamping the piece while the glue sets. Granted most construction is designed to be compression rather than tension so it may lack some basic principles for box design.
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Jordan,

Until houses are exposed to tornados (which frequently tear them into parts), they are not subjected to anything like the pressure and near vacuum produced from 30 to 100 times per second in a high power sub, which Helge's will definitely qualify as.

At 100 dB, there is little atmospheric pressure change, only 2 Pa(scals). At 110 dB, there is about 3 times that pressure, and you can start to feel it.

The atmospheric pressure in Pa continues to roughly triple for each order of magnitude SPL rise. 130 dB makes for 100 Pa, the equivalent of a 28 mph wind, plenty to feel SPL frequency modulated "wind" in long hair or loose clothing. Generally speaking, at high drive levels loudspeakers progressively create more SPL (and therefore Pa) on the compression (forward) wave, so there is a net flow of "wind" away from the driver or horn exit. Testing at high SPL levels (around 128 dB at one meter) I have seen 6 foot "rooster tails" of sawdust blown in front of my Keystone sub horn exit.

At 143.5 dB, the pressure is 100 times that of 110 dB, and actually equals the lung air pressure difference of normal breathing. At and above 143.5 dB SPL low frequencies will definitely modulate breathing, and it is not at all difficult to tell the difference in the frequency of modulation that the external "air pump" is working at. That level of SPL can be experienced directly in front of many of the sub woofer designs on this site, as well as commercial offerings from a number of manufacturers.

If we measured inside the IPal 21 driven Keystone, it will certainly exceed 159.7 dB, equal to 1932 Pa, more than 6 times the lung air pressure difference of normal breathing!

Use lots of screws...

Art
 
Re: This winter's DIY-project just arrived.

Helge Dr. Bentsen said:
Duly noted :)
What is your recommended screw diameter/length for 3/4 birch plywood?
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I generally use #6 x 1-5/8 inch phillips bugle-head fine thread drywall screws. With "real" 13 ply baltic birch, they need pilot holes and countersinking or the heads will break off. Some "birch" plywood uses soft fillers and you can just drill direct, though countersinking makes it more consistent when filling the screw heads.
 
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