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Forte Modifications


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Afternoon all,

 

As part of my cosmetic refurbishment of a set of Fortes, I was curious as to mods others have done to the cabinets to stiffen and/or dampen them.  Although they are heavy, they also seem very resonant, especially with the drivers still in them.

 

Based on the use of a passive radiator, I would imagine I would want to avoid mods that reduce internal cabinet volume, or absorb the air pressure that drives the drone (i.e. stuffing, dampening on interiors).

 

Some of Moray's mods are easy to do as well (dampen horns, dampen speaker baskets, add washers to the drone), and I plan to do these.  However, after seeing some extensive mods on a set of Forte III on audiocircle, I'm wondering if I should do more.

 

Thoughts I had were to add some additional bracing, put some absorbent mass loading (sand?) in their bottom, add a few irregular foam pieces to the inside sides to break up waves, and double the front baffle thickness (externally) with a piece of HDF, either for the whole front, or up to the top of the woofer.

 

Anyone else tried any of these mods, and if so, how did they affect sound?

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17 minutes ago, ScooterMcTavish said:

Afternoon all,

 

As part of my cosmetic refurbishment of a set of Fortes, I was curious as to mods others have done to the cabinets to stiffen and/or dampen them.  Although they are heavy, they also seem very resonant, especially with the drivers still in them.

 

Based on the use of a passive radiator, I would imagine I would want to avoid mods that reduce internal cabinet volume, or absorb the air pressure that drives the drone (i.e. stuffing, dampening on interiors).

 

Some of Moray's mods are easy to do as well (dampen horns, dampen speaker baskets, add washers to the drone), and I plan to do these.  However, after seeing some extensive mods on a set of Forte III on audiocircle, I'm wondering if I should do more.

 

Thoughts I had were to add some additional bracing, put some absorbent mass loading (sand?) in their bottom, add a few irregular foam pieces to the inside sides to break up waves, and double the front baffle thickness (externally) with a piece of HDF, either for the whole front, or up to the top of the woofer.

 

Anyone else tried any of these mods, and if so, how did they affect sound?

you want to stiffen the cabinet with as little material as possible so as not to eat up cabinet internal volume. all braces are on edge. brace below and above the woofer mid and passive. on the sides top and back install on edge vertical braces and where possible interconnect all braces with stringers to effect a rigid matrix. Hope this is of interest. Cabinet shown is a Quartet which is essentially just a three inch shorter Forte cabinet. Hope this is of interest to you.

Quartet rebuild 011.jpg

Quartet rebuild 017.jpg

Quartet rebuild 021.jpg

Quartet rebuild 016.jpg

Quartet rebuild 020.jpg

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why do people modify speaker cabinets when they have no idea what impact those modifications will do to the overall sound of a speaker? I have no added bracing on my 40 plus YO Fortes and have never thought they resonate too much or need extra bracing. 

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54 minutes ago, Fido said:

why do people modify speaker cabinets when they have no idea what impact those modifications will do to the overall sound of a speaker? I have no added bracing on my 40 plus YO Fortes and have never thought they resonate too much or need extra bracing.

 

Here is a very good explanation from a site known to be more straightforward than many others:

 

https://www.audioholics.com/loudspeaker-design/loudspeaker-cabinets

 

Unfortunately, the cabinet is often the first place where costs are saved on a build. Extra costs for bracing and shipping sell less speakers than having a nice veneer vs a vinyl wrap.

 

However, making this cabinet less resonant, while also not changing its fundamental engineering should "generally improve" its sound.  Of course, improve is a subjective term, and I hope to make any mods "undoable" if they result in crap sound.

 

 

 

 

 

 

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1 hour ago, Fido said:

why do people modify speaker cabinets when they have no idea what impact those modifications will do to the overall sound of a speaker? I have no added bracing on my 40 plus YO Fortes and have never thought they resonate too much or need extra bracing. 

if you are happy and do not notice any problems then that is good for you. But because someone does not notice or care does not mean others do not notice or that they cannot make an improvement.

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I am happy! I inherited the Fortes from my father and love the way they sound as is but if anyone wants to modify their speakers they should go for it. I know you have done a lot of bracing on the speakers you have owned and love adding bracing and getting the floor standing speakers up off the ground and on to speaker stands.If that sounds better to you AWESOME!

 

Everyone hears things differently and sometimes I have no clue what to even listen to.

 

For me -its enjoying the music. 

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10 hours ago, ScooterMcTavish said:

Afternoon all,

 

As part of my cosmetic refurbishment of a set of Fortes, I was curious as to mods others have done to the cabinets to stiffen and/or dampen them.  Although they are heavy, they also seem very resonant, especially with the drivers still in them.

 

Based on the use of a passive radiator, I would imagine I would want to avoid mods that reduce internal cabinet volume, or absorb the air pressure that drives the drone (i.e. stuffing, dampening on interiors).

 

Some of Moray's mods are easy to do as well (dampen horns, dampen speaker baskets, add washers to the drone), and I plan to do these.  However, after seeing some extensive mods on a set of Forte III on audiocircle, I'm wondering if I should do more.

 

Thoughts I had were to add some additional bracing, put some absorbent mass loading (sand?) in their bottom, add a few irregular foam pieces to the inside sides to break up waves, and double the front baffle thickness (externally) with a piece of HDF, either for the whole front, or up to the top of the woofer.

 

Anyone else tried any of these mods, and if so, how did they affect sound?

IMHO, focus on bracing the widest dimension. In the case of my KLF-10's, the widest dimension is the 16" depth, the face/back are only 12" wide. They came with two stout braces spanning the 16" sides from the factory so I was satisfied.

The forte's widest dimension is the face and back. Plus the big holes in both make those two faces prime candidates for some front-to-back bracing. Something that works well that I have seen few guy use is 1.5" or 2" wood dowel. Cut four of them super tight fitting, use a bottle jack to create a tiny bit of separation between the front and back faces, glue the dowel ends and stuff them in around the woofer and radiator, putting glue on the cabinets in spots where the dowels will rest. Make sure you hold them in place (you may need more hands), then release the bottle jack. No need for clamps or weights and you'll be able to use them as foundations for your house.

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15 hours ago, Fido said:

why do people modify speaker cabinets when they have no idea what impact those modifications will do to the overall sound of a speaker? I have no added bracing on my 40 plus YO Fortes and have never thought they resonate too much or need extra bracing. 

My Forte IIs sound like a box and I am sure Is do too though I agree, you should know what you are doing before you proceed with a project like this.

 

Mods are good, just make them reversible at the start in case you don't like the results.  As MechEngVic said, concentrate on large panels if you do proceed with this work.

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If you look at this photo you can see that I have lined the inside of the cabinet as well as the larger braces on both sides to absorb upper range radiation from the woofer. This does two things first it diminishes the level of rear wave radiation and reflections and second it helps offset the small volume loss due to the additional brace work inside the cabinet, the brace work also breaks up and damps standing waves within the cabinet, most importantly the overall volume of the cabinet is totally open to resonate and couple with the passive. A brace along the length or depth of the top of the cabinet will help greatly with panel resonance. I intentionally leave the bottom of the cabinet alone for a couple of reasons. First if at some later date you or another owner wants to upgrade the crossover the bottom panel is the only available space to use so I leave it alone, second once the speakers are stand mounted (with the old ugly and dated looking risers removed) you can no longer hear any radiation from the bottom panel and so it becomes a non issue. I hope this helps.

As a final note the braces in the Quartet cabinet shown are larger than necessary. With retro brace work more is not necessarily better, for a 3/4" plywood brace the height of the brace need only be 11/4" for maximum stiffness, making the brace taller has only a minimal impact upon stiffness but it has a dramatic impact on unnecessarily using up cabinet volume.

 

Quartet rebuild 011.jpg

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Thought I would post a pic as I've decided to go with fairly minimal mods.

 

I will be putting four thin braces front to back between the woofer and passive for additional rigidity.

 

Instead of stuffing or padding, I've gone with a minimal liner to break up standing waves.  It is a thin ribbed packing foam I use for wrapping electronics when I ship them.  This does not reduce cabinet volume, yet will also not interfere with air pressure for driving the passive.

 

Last mod will be some vibration absorber on the woofer and passive baskets, and the horns.  That should be arriving this week.

 

 

OIP00006.jpg

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5 minutes ago, ScooterMcTavish said:

 

Last mod will be some vibration absorber on the woofer and passive baskets, and the horns.  That should be arriving this week.

 

 

OIP00006.jpg

 

 

What are you going to be using for your vibration absorbent on the drivers  if you don't mined me asking?

 

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A few pics of the Noico dampening material, and a set of the drivers that are dampened.

 

There was certainly a difference flicking the mid horn with a finger before and after dampening.  Whether it makes an audible amount when in use is still to be seen.

 

I am amazed that Klipsch built such a huge beautiful motor structure on the woofer, yet attached it to a sad stamped basket with only four spokes.  It's like the opposite of CVs - where a great basket is married to a less substantial motor.

 

After spending a lot of time with these speakers, they strike me as very well-designed, yet compromises were made, likely to keep them within a price point, and/or shipping weight down.

 

 

OIP00008.jpg

OIP00009.jpg

OIP00010.jpg

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The damping material on the exterior of the horns can't hurt, but that shown on the woofer, especially on the back of the magnet, well, I seriously doubt anything whatsoever was gained by that effort.  The baskets may not be as pretty as machined castings (of lighter material) but they have all the strength required for the task at hand.

 

Would likely gain more benefit (though still minuscule) by applying an absorptive-surface material to the insides of the basket webs.  To minimize reflections, not ringing.

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The Noico is on the steel basket of the passive speaker in a place that can resonate, there is no magnetic system in this place. So for me the modifications are beneficial and in any case easy as everything is already dismantled, so why deprive myself of it, I find it positive 👍

 

:)

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