Speaker Directivity Modifier

[rabidgerry]

Has anyone ever heard of this?

I really fancy trying this as because it sounds like an issue I could do with it.  The guy who designed it knows what he is talking about, although I still don't quite understand.  Sounds like it works though.

It may not appeal to anyone on here but it certainly interests me enough to try it.  I experience this unfortunate death ray of trebel all the time and I would like to alleviate the issue if its possible.

http://www.instructables.com/id/Guitar-Amplifier-Speaker-Directivity-Modifier-Bea/


http://www.thegearpage.net/board/showthread.php?t=470956

[rnolan]

Hey RG, try it and tell us how it goes, personally, I wouldn't bother, I'm not denying the science makes some sense, but god invented quad boxes for a reason LOL

[MarshallJMP]

Or you can change the grill cloth with some like the old basket weave cloth that marshall used back in 60's?

[rabidgerry]

I am certainly going to try this.  Honestly if you find the time start reading those threads.  I discovered by accident and once I started reading I was kinda blown away.

The whole directivity thing is a complete nightmare.  I hate only being able to stand in one spot for sound at shows and also in rehearsal room.  I always eq standing on axis so I would like to enjoy amps where it didn't matter whether I was on axis or off axis.

Not sure about basket weave stuff MJMP,  I think the theory is for all cabs that suffer from directivity issues, and in my experience that's every cab I have ever played.  The foam addition is also to only fill the speaker baffle for each driver. and this is regardless of the material used for the grill (metal/material/basketweave).  You can't just use any foam either, it has to be open cell and a certain density as well as thickness.

I'm trying it when I get the foam and the time.  Spent an entire day yesterday playing about with 4 difference speaker drivers and mixing and matching, still didn't get through everything I wanted to get through either so I will have to try the foam thing when I have a spare day that I am not rehearsing or playing on.

[MarshallJMP]

Well i've seen alot of things and solutions for various problems over the years and usually you end up making it all back original.Mostly you gain one thing and have to give up something else.But there's no harm in trying i guess 

[rabidgerry]

I hear you MJMP

what you loose doing this modification is the horrible beam on axis.  So if some people like that (I dunno who likes that??) then they will be losing out.  But then they shouldn't do the mod in the first place.  So yeah basically what you loose is the difference between on axis and of axis sound from your cab.  I personnally want to loose that beam because it's annoying as hell.

The filter (or to be correct speaker directivity modifier) acts diffrently from say a beam blocker
http://www.webervst.com/blocker.html

Those things block the centre portion of sound that travels from the driver causing comb filtering and other phase effects.  The foam solution I'm on about reduces the high frequencey like an EQ balancing the sound of the driver to have a more even frequency distribution from every postion of the speaker driver.

Sure it sounds like black magic I know lol
I'll hopefully get experimenting with it on Saturday of this week as I just got the right foam to do it.  Will let you all know.

[rnolan]

I get the idea but you will loose power (absorbed in the foam) and the freq response will change as the tops will be absorbed more (as well as diffracted (which is what you are chasing)) and this is all about top end because it's directional. I tend to use just one ADA Slant Split Stack wired stereo these days (less to lug). It's quite directional, works fine in a room, but harder on stage. Having more cabs and placing them right helps. If the gig has decent monitors, I have stereo guitar in my own 2 wedges and some more in the side fill.  Otherwise, if the cabs are being miked up, I use 2 ADA SSSs stacked on their sides facing across stage (so like turning a quad box on it's side, angle at front of stage) and up off the floor so they open up on my ears (or I tend to play too loud LOL).

[rabidgerry]

That's why you have to get the right foam, the right density of foam and the right thickness, apparently you aren't doing it right if you notice a masive decrease in output.

And...............when the hi end is cut we perceive it as a drop in volume more so than it actually is.  Just liie when yo have a bright setting but feel you need to set the volume much lower in order to sound on par with say a darker tonmal setting.  Where as on actual volume meters this might read both patches to have the same volume only the one that is bighter sounds much much louder due to the way our ears work.

So enough of that babbling, yeah reading the thread basically says if you notice too big a volume difference then you've done too much.  All you should notice is attenuated highs and no directional differences or at the very very least not as big a difference on or off access.


it actually states this on the thread:


Quote:
How much does blocking off that much of the cone reduce the overall volume?
None, if you're accustomed to playing in an off-axis position. Open cell foam in this thickness has almost no effect on sound passing through it at frequencies below ~1kHz. The doughnut will therefore cause no change in off axis response or sensitivity. It will reduce higher-frequency content directly on axis. If you're accustomed to playing with your cab aimed straight at your head, the doughnut will make it sound darker by reducing the on-axis sensitivity of the speaker in the higher frequency ranges. If you've adjusted your tone to remove the "ice pick" effect on axis, you will need to brighten it with the doughnut in place. The advantage you will gain is that your position relative to the cab will no longer matter so much: it will sound the same off axis as when you aim it at your head.

[rnolan]

Yeah I get it, the tops come from the centre of the cone combined with that, top end is much more directional, it will seem softer (though it's not much softer) coz your ears hear 1-5khz "apparently" louder (until you hit 98db, then the bass/mid/treb flatten out, then the curve reverses as you get in Metal  >:D volumes and the bass and treb appear louder than the mids). Hey RG if it works for you give it a go, I'm not as bothered by the on off axis difference (but I hear you, it's just always been parf the course for me), on a larger stage I'd go for more and better placed cabs (maybe not always an option for you). I aim my cabs at my head so I don't drown out everyone LOL and adjust my tone to suit (there are lots of ways to skin this cat ...).

A good well spread couple of cabs aiming cross stage (miked obviously) may work for you ? (has become my preference) but maybe not an easy option with the gigs you do.

[rabidgerry]

I don't get a say with mics usually at gigs and I am the same as you, I get my cabs up to ear/eye/head level as often as I can.  To me it's f**king stupid to have cabs pointed at your guts or your feet.  Most people have it at their feet I think unless they have a 8x12" stack.

I'll give you an example.  I played a festival last week.  I could not stand anywhere near my amps because of the death ray.  Now I was using two cabs 1960 marshalls that had been rented. Normally I cannot get enough of my own sound onstage, well I had to stand away from those things the whole show as it was painful to play infront of them.  Since I had no sound check (festival rules so line check only before our set) I had no time to fiddle about with stuff to tame that beam of trebel.

So applying the same problem to my own gear.  I get this beam in the practice room.  However I stand in it because I made my tone when I was standing in it.  It's when I step out of it that there is a shit drop in good sound.  So if I balance this out things should be a lot more enjoyable for me and the rest of the band and no one has to worry about stepping in and out of a stupid beam.

I also decided to tilt my 2x12" on their side in a more vertical alignment.  I like the spread alot better doing this.

Anyways I put the foam donuts last night.  I can test them at the weekend.  12" poyureathan open cell foam circle with a 3inch hole cut in the centre!  No harm in trying it.

[rnolan]

Cool, let me know how they sound. Anything that helps you get a decent sound (and for everyone else in the band) to hear helps you play better.

What will you do a gigs though with rented quad boxes ? Coz now you'll adjust your tones to having the foam donuts ?? I spose you can take them with you and annoy the sound dudes LOL (depending on who they are, I wouldn't have an issue accommodating that if I was mixing you, but I've bumped into many a sound guy that would (and they're not usually any good LOL)).

[rabidgerry]

Cool, let me know how they sound. Anything that helps you get a decent sound (and for everyone else in the band) to hear helps you play better.

What will you do a gigs though with rented quad boxes ? Coz now you'll adjust your tones to having the foam donuts ?? I spose you can take them with you and annoy the sound dudes LOL (depending on who they are, I wouldn't have an issue accommodating that if I was mixing you, but I've bumped into many a sound guy that would (and they're not usually any good LOL)).

well I did a rough test and it did work.  It didn't reduce it enough though I think so I might need to get the same foam only a little thicker.  I got 1/2" foam rather than 3/4" thick foam.  I will try again with the slightly thicker stuff.  The overal volume loss was not much if I am honest.  I wasn surprised.  I also messed my templates up.  I had them exactly 12" circles.  Little did I know the baffles were actually about 11" diameter.  So I need to adjust them all now to 11" in diameter.  So basically speaking your speakers are 12" but the baffle in your cab is a little smaller again and the 12" inch rim of the spaker sits on the wooden baffle.  The rim of the speaker is about an inch therefore the actual whole for the sound to travel through is only 11".  Makes snese but I couldn't squeeze the foam in there without it distorting and f**king up so I just need to cut them the right size and I can then give an even better analysis. 

[DesmoBob]

Hey, I saw that thread, too. I will definitely try it, but will be getting a new cab first. I'm interested in your results, as I'm planning on getting a 2x12, and I noticed you also have 2x12s. I'm probably going to get both 1/2" and 3/4" just to see which gets the best overall result in my particular application.

I also messed my templates up.  I had them exactly 12" circles.  Little did I know the baffles were actually about 11" diameter.  So I need to adjust them all now to 11" in diameter.

Later in the thread, Jay Mitchell said you didn't necessarily have to cut the foam into a donut, thus saving you some labor. The important thing was to keep the hole in the middle, and make sure the foam is big enough so no sound waves would circumvent the outer edges of the foam. The foam could then be placed between the baffle and the grill (not necessarily in the cutout), space allowing.

He also said there are other phenomena going on in multi-speaker cabs, so overall effectiveness might be less than when compared to 1x12 cabs. This was in response to the person using 2x12s.

Keep us updated with the 3/4" results.

[rabidgerry]

Hey, I saw that thread, too. I will definitely try it, but will be getting a new cab first. I'm interested in your results, as I'm planning on getting a 2x12, and I noticed you also have 2x12s. I'm probably going to get both 1/2" and 3/4" just to see which gets the best overall result in my particular application.

I also messed my templates up.  I had them exactly 12" circles.  Little did I know the baffles were actually about 11" diameter.  So I need to adjust them all now to 11" in diameter.

Later in the thread, Jay Mitchell said you didn't necessarily have to cut the foam into a donut, thus saving you some labor. The important thing was to keep the hole in the middle, and make sure the foam is big enough so no sound waves would circumvent the outer edges of the foam. The foam could then be placed between the baffle and the grill (not necessarily in the cutout), space allowing.

He also said there are other phenomena going on in multi-speaker cabs, so overall effectiveness might be less than when compared to 1x12 cabs. This was in response to the person using 2x12s.

Keep us updated with the 3/4" results.

hey Desmo this definitely worked.  They key is getting the correct type of foam.  And of course the hole in the middle.  Now I tried this and as I said it worked, however I have not had time to fully implement it yet but I finally get a chance to do it next week!!  I had to wait on more foam arriving and also I was experimenting with too many other things at one time.  I'm really keen to get it sorted because the directivity is a bloody nightmare for me.  I cannot stand moving out of the beam.  I set up my sound in the beam you see, so I get rid of ice pick head on, but then when I move suddenly it's muffled.

I did go to the trouble of cutting the foam into circles.  However, I cut them the same size as the dam speaker cones.  Here is a bit of advice.  Don't do that!!  Measure the size of the baffle that you intend to put the foam into!!  My baffle works out around 11" circumference.  So I have to modify all my circles again.  Which is tricky once you have already cut them into a circle.  Doing it from a square is easier.  So anyways I'm planning on sorting this next week.  My baffle it a little deeper than the foam (I think around 3/4")  however I chose to use the 1/2" depth foam as I wanted to gauge things gradually rather than dampen a shit load then find I needed thinner cut foam.

To try quickly I placed the foam over the front of the cab from the outside.  Worked!!  When I was looking for the foam I was worried I could not find the correct material.  Jays links are all for US retailers, I had to look for one in UK.  Thankfully the first one I tried sold open cell foam and nothing else.  I chose medium density and 1/2" thickness.  I'm not sure if it was possible to choose light density and then balance that out by picking the 3/4" thickness but I reckon I got lucky first time and I wont need to experiment with the different densities and thicknesses.  However knowing me I might just do that anyways depending 

Will keep ya posted :)

[DesmoBob]

Hey RG, updates?

I got a new cab and foam. Doughnuts will wait until the speakers are more broken in, though. (Actually that's just my excuse for being too lazy to open the cab and measure the baffle holes this week).

DOOOOUUGGH-nuts!