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Heresy Mod - Leave Foam Tube??


joseph222

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I removed all drivers from my cabinets and have dampened the horns with rope caulk. I also lined all surfaces of the cabinet with 1.5" thick polyester fill cloth. When I removed the woofer, I was surprised to find it has a 1X10X24" piece of foam "wrapped" around the speaker that extends from the front to the rear baffle forming a foam tube around the driver. A cheap and quick way to achieve some dampening by the manufacturer? So now I'm wondering, with the rest of the cabinet now dampened with the polyester, should the foam wrap be left in place or removed? Is there a danger of over-dampening? My guess is to leave it in but I don't want to over dampen. Observations and comments from the more experienced would be most welcome.

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You have already overdamped the cabinet by lining it with the polyester material. You may well like the new sound, but it will detune the bass response.

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Thanks for your observation. I am curious to know if this round tube of foam wrapped around the woofer is a factory application, or if this was something done by a previous owner of these speakers. If I leave it out, and rely on the poly fill for dampening, should I remove some of the poly fill, say from the top, and one side, or leave it and just remove only the fill from the rear baffle? I am new to this arena and appreciate any suggestions. Thanks.

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9000,

I believe putting insulation on all surfaces ends up more than the original foam in question. Too much of a good thing is not good. Consequently he ends up with an overdamped enclosure rather than a critically damped one. Most text books that I have read seem to prefer damping on at most three surfaces.

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John P

St Paul, MN

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I don't belive the Hersey I's had any foam or such materials anywhere in cabinet. Is no damping such as the I's good? Klipsch parts list shows the k-24-k woofer for both Hersey I&II's. If the original woofer was different in the H-I wouldn't Klipsch instruct to add the foam "u" when using the k-24-k in H-I? The k-24-k woofer specs would have to have the proper box volume. The foam in my H- II's is in an upside down "u" that isolates woofer; foam is front to back, contacts the bottom of box and arc is at bottom of squawker. A rough guess would be that total box volume is 1.7 ft. Volume of "u" is substantially less. Why no foam in I's if they have same volume and woofer as II's?

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Thanks everyone for your advice and comments! I guess I should have mentioned in my first post that I have three improvement goals in mind for these cabinets. One is to tame the sometimes harsh characteristics of the horns. They have been dampened with rope putty/caulk.

Two is to improve transparence and maybe extend the presence of the hi & lo end. As I understand, this can be accomplished by upgrading the Xover capacitors? The ID numbers of my caps do not match what I have read on other posts - but I am going to post separately to keep things simple. If you're into caps you may be familiar with these other ones.

The third goal is to tighten up the bass (but not to sacrifice the lowest frequencies attainable 40-50K?). As I understand, this can be accomplished by adding some insulation material. In light of everyone's comments, here is what I shall try. I see now I screwed up by applying deadening material to every surface (except the back of the front baffle). I will leave the poly fill on the rear baffle, one side panel, and the top panel - 3 panels in all. Since the 1" foam is an original factory application I will leave the 1" foam U in one of the cabinets and remove it in the other to do some listening evaluations. I will post my findings if anyone is interested.

Note: The 1.5" poly fill (a blanket material from the fabric store), I'm using is basically identical to fiberglass insulation, but just not as thick. It is not a foam. I don't see any reason off hand it would not do an equivalent job and have heard it's use on other DIY forums. If there is some benefit to the fiberglass I wouldn't hesitate to switch to it.

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mdeneen,

Thanks for your great info and encouragement. Sometimes I think I should just go out and buy some new Bose..... :/

You have mentioned "port" in several of your postings. Am I confusing "speaker hole" with "port"? I think of these as two separates. The speaker hole being, of course, the hole the speaker goes in and the port is a hole of specific size that correlates to the cabinet volume and speaker resonating frequency? Sometimes, with tubes being used in the port so smaller size cabinets can be utilized. Think of this configuration as a "ported cabinet design as opposed to a closed cabinet. My cabinets do not have a port as such. Am I misunderstanding you or am I just wrong? frown.gif

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Well, no apology necessary - hey, I'm the one asking the naive questions...

The Dickerson book sounds good - I'm gonna try it.

I posted a question you may have some insight into under the subject Strange Caps in Heresy. I'll let you and this list know how this all turns out. There may be other owners of these later model IIs that might be interested. Thanks.

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