OT Rubber mounting the speaker

I was thinking the other day as I listened to my speakers resonate my cabinets that maybe if the speaker was somehow connected to the cabinet using a piece of rubber...say 3/8 thick industrial stuff with the white cord running through it. if this would make much of a difference? I googled the idea and found something but I didn't think to bookmark it...kinda sounded like some German high end speaker maker was doing it... You would think it would cut down a lot of the coloration. My 604 C has no gasket and mounts directly frame to baffle while the 604 E has a gasket but I can't imagine it does much since it's screwed down tight to the baffle anyways. What are your thoughts on this idea? :o

My .02 would be that the preferred remedy would be to damp/deaden the cabinet via bracing or other methods.

I think this is where I got it from... Down towards the bottom of the page.
http://www.linkwitzlab.com/frontiers_2.htm

You don't need anywhere near 3/8 inch.

There are rubber membrane rolls for roofing often about 1/16 inch or so.

http://www.rubber4roofs.co.uk/EPDM-R...Shedcover-EPDM

I used to stop by roofing places and offer a few bucks for scraps...they throw away pieces large enough for us.

Thanks Old Guy, Originally I was picturing mounting the basket of the speaker to the baffle with rubber I'm not sure I would want to risk hanging a 40lb duplex with a 1/16 thick piece of rubber but if your talking the mount the speaker by grabbing the magnet then yes 1/16th would be fine. Which after reading the link I posted I see they were saying mount it by the magnet not the basket. :2thumbsup:

I use the rubber between the frame and baffle. I use an adequate baffle the rubber is to seal,

As a general rule, about the last thing you want to do with a LF reproducer is 'float' it. The goal is to provide the most stable 'platform' practical for it to do its 'work' efficiently, so ideally it isn't attached to the cab in any way and its design is such that it has no self induced vibrations in its pass-band.

If one looks carefully at an early WE open baffle 'sub' used under the large 15a horns you'll notice that the massive LF driver(s) snuggle up to the baffle, but are not actually bolted to it, instead bolted to a separate, rigid/massive platform or floor.

Later, no doubt to cut cost, etc., for mass production, surround gaskets of the right density to damp any driver induced resonances were developed to allow rigid mounting to a sufficiently rigid/massive baffle.

WRT your 604C, I've never seen a wide BW Altec driver with no mounting gasket, but again, the driver/cab is a system, so if it didn't come from the factory with a gasket, then apparently the assumption was that it would only be used in an Altec approved cab that had taken this into account WRT material, assembly choices.

Note that the gasket design is based on a given clamping pressure, so for max efficiency the specified hardware must be torqued to spec which for most (all?) prosound drivers which I lump Altec into would be based on standard bolt size/thread torque charts which typically is much lower than the average person would hand tighten to.

All that said, if the driver has a high Qts (> ~0.7), then its mounting should be lossy, increasing with increasing Qts to mechanically damp it, effectively lowering its Qts and why those old Motorola consoles with the woofers mounted in individual Styrofoam 'cabs' sounded so good, yet when swapped into a regular cab rang like a 'ten penny nail struck with a ball-peen hammer'.

GM

Bowtie & GM have hit it right.

Idealy speaking, the driver mounting should be as rigid as possible. The box contact with floor etc also. We want all the impulses reproduced perfectly. No shock absorber theory here. The worst sufferers will be the low Qts drivers (namely Altecs). We will end up with non linear transients, especially in the lows.

We talk of sand filled cabs, to bring mass/rigidity into the system. Now the drivers will swing on their own cushions ?

Now having said all that, it is also true that every coupling has a resonance f, and it may be used to some advantage in eliminating known (troublesome ?) areas. But as I see it, it is either a heavily compromised design or a very evolved one. For the later case, it will be a very very complicated design.

Aditya

Nice to finally see mention of Siegfried Linkwitz on this forum -- never imagined that it would ever happen.

His recommendation of magnet-mounting applies to the midrange driver of the Orion loudspeaker system; it is intended to prevent driver frame/magnet resonances being transmitted to the baffle. It applies to the midrange driver of the Orion, not the LF drivers. Btw, Pioneer/TAD also made similar recommendations for MF cone drivers as well.

While ideal, it is not feasible for heavy LF drivers so a thicker baffle or extensive baffle panel bracing to push the frequency of panel vibration upwards where it is much smaller in magnitude is the best compromise.

BobR

Yes!!! Siegfried Linkwitz was the name I was reading about!! it kinda sounds German....Is this the same thing as what they did in that 6 moons article with the 604's? I remember they had some kind of clamping system on the magnet part of the speaker although if I remember correctly the speaker was mounted to the baffle too... I think it's all starting to make sense now.....your gonna get panel resonance no matter what. And you want to drive up the resonance frequency because it's less noticeable ( it gets harder to hear the resonances at higher frequencies) and to raise the resonance of course you would want stiffer just like the tighter the guitar string the higher it rings at. so Because I'm hearing what sounds like the box making the sound instead of the speaker is because the cab frequency is to low? It happens mostly when people are talking on movies.
This place has more useful knowledge that the encyclopedia Britannica. Thanks again guys for the wisdom.

Guys, being well acquainted with the EPDM product in question, I can assure you this is not something to decouple your driver from the baffle, it will act as a gasket, nothing more.

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Originally Posted by cradeldorf

I'm hearing what sounds like the box making the sound instead of the speaker is because the cab frequency is to low? It happens mostly when people are talking on movies.

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Wow--some great advice/info in several posts of this thread regarding fixing the resonance problems you're experiencing with your home-made cabs (adding bracing, using rubber, etc.). One of many testaments to how great the people here (and this forum) are. You might also want to consider trying your GPA refurbished 604's back in the original Heathkit AS - 101 cabinets that they were in when you bought them. As I mentioned in one of your previous threads (and also in a reply to one of the PM's you sent me), I used to own a pair of AS 101's. I played those speakers at volume levels ranging from extremely low to (what I consider to be) extremely high with all sorts or program material (music, movies, television--spoken word, etc.) and never once had any problems with cabinet resonance. Those Heathkit AS 101 cabinets are solid as a rock -- many prefer them to Valencia cabs although I've owned Valencias as well and never had any resonance problems with my Valencia cabs either (846A). Unfortunately, from your description of how bad your drivers sounded in those cabs, whoever modified your Heathkit AS 101 cabinets apparently didn't really know what they were doing and they seem to be horribly tuned at this point. Rather than turn those cabs into dog houses (although there are a lot of homeless dogs that would no doubt appreciate them), you might want to consider fixing the modifications that were done to them. If they were mine, I'd give them another shot -- nothing to lose but some time and potentially a lot to gain. I'd first remove the two "shelves" that someone added to them (possibly a failed attempt at dbr tuning?). Then I'd reduce the port size--from your photos and the port dimensions you posted in a previous thread the ports are most likely way too big. No wonder the drivers sounded horrible with those cabs tuned that way. You've experimented with different port sizes with your new home-made cabs (trial and error) to get them tuned optimally, I would suggest you try the same thing with the AS 101 cabs. If you want to go with the same empirical method, after you've removed the two shelves, just block off some (most?) of the port from inside the cab with a piece of wood "tacked" into place--experimenting to determine how much of the port blocked off sounds best. Once you find the ultimate sounding port size, screw the wood that you're using to block some of the port permanently/securely into place inside the cabinet. Or, build an "adjust-o-port" like you attempted at one point with your home-made cabs.... Tuned properly, those Heathkits should get WAY better bass response than the smaller home made cabs (I never had to add much bass EQ to my factory tuned AS 101's and they got GREAT bass response), so you'll most likely have to re-adjust your EQ or they'll sound like they're too boomy (too much bass) when they're properly tuned because in one of your previous threads you mentioned you had to add a lot of bass EQ for the duplexes to sound good in the smaller home made cabs (I would recommend that you reduce the bass EQ you're adding before you start experimenting to find the optimal port size). Switching from the home-made cabs to the (properly tuned) Heathkit cabs may also give you more accurate sound reproduction/cleaner more powerful sound and better/deeper bass because the cabs will be doing a lot of the work for you--the (properly tuned) cabs will be providing a much better bass response--which is preferable to having to add lots of bass EQ to compensate for small(er) cabinets. Let the Heathkit cabs do the work rather than adding a lot of bass EQ to compensate for the smaller home-made cabinets and you should have much more realistic sound with much less strain on the woofers which allows them to go louder/deeper and sound cleaner..... I'm not recommending that you don't fix/brace your home made cabs, I'm just recommending that you consider fixing the failed modifications that were done on your Heathkit cabs. If you do, I predict that you'll find they sound way better than the smaller home made cabs, and at that point you may decide not to fix the home made cabs (or maybe fix them for a future project)...... Just my opinion as a former owner of AS 101's--I LOVED the way those (rock solid) cabs sounded--and I know what kind of phenomenal bass and mids can come out of them with an Altec 15 installed (granted, a different Altec 15 and crossover), when the cabs are properly tuned.....

Thanks Vott, I think putting effort into my home made cabs would just be fruitless. those Heathkit cabs are made of particle board though and it doesn't seem very stiff or rigid? Unlike say solid oak? I was picturing solid oak with the speaker mounted to the baffle with a solid clamping system around the magnet would be the way to go? Also doesn't weight play a part too? the heavier the speaker is? or is that just my imagination.
BTW I don't think the heathkit cabs sounded horrible...they kinda sounded not good but after I switched the speakers back into my homemade cabs I realized the the HF leads needed to be switched around I think if I had done that in the heathkit cabs I'd probably still be running them.

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Originally Posted by cradeldorf

Thanks Vott, I think putting effort into my home made cabs would just be fruitless. those Heathkit cabs are made of particle board though and it doesn't seem very stiff or rigid? Unlike say solid oak? I was picturing solid oak with the speaker mounted to the baffle with a solid clamping system around the magnet would be the way to go? Also doesn't weight play a part too? the heavier the speaker is? or is that just my imagination.

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Yes, I believe my Heathkit cabs were some sort of particle board--and yes, whatever the exact term is to describe the material they are made of, it's not an ideal material. But they were rock solid and never had any resonance issues (and sounded great--noticeably better than my Valencias did)--nice full, deep bass. Most people who've heard AS 101's love the way those cabs sound--at least most of the people who's comments I've read here on this forum and over at LH before I joined here (people like Robert Bartsch and Tom Brennan just to name a couple of examples off the top of my head). They are great sounding cabs but they're not the best cabs that money can buy (or build). I wish you could hear a properly tuned AS 101 cab--you would probably not even consider building a whole new pair of cabinets from scratch--you'd want to properly tune the cabs you already own. You would presumably be using an empirical approach to find the ideal tuning for your duplexes to really get some nice deep bass out of them--you may be able to tune them even lower than my AS-101's were tuned (that housed 416's).

However, if you want to build another pair of cabs from scratch, I'd use something like the Baltic Birch westend is using for his cabs

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Originally Posted by westend9

I returned those sheets and am now using standard Baltic Birch, 5' x 5' sheets, 13 ply, purchased from a local hardwoods supplier and was able to check the origination of the product. These are the real deal.

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I'd use a proven Duplex cabinet design and wouldn't improvise this time--maybe a pair of Stonehenge III cabs or Model 17 cabs (any suggestions from the folks out there)? Cabinet building is not my area of expertise--I'm sure there are several people here who have plans or can provide links for plans for cabinets that have a proven track record for sounding great when they house Altec 604's...... If you decide to start from scratch rather than spend some time on the Heathkit cabs first, I'd follow whatever plans you end up selecting to the letter and use Baltic Birch. Yes, if you have the plans, materials, tools, skills, and time, you can build cabs that will sound better than the Heathkit cabs, but if you achieve an optimum tuning for your Heathkit cab/Duplex combination I really think they'll knock your socks off and you might be glad you saved a lot of money and time for what may have been a relatively small difference in sound.....

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Originally Posted by cradeldorf

Thanks Vott, I think putting effort into my home made cabs would just be fruitless. those Heathkit cabs are made of particle board though and it doesn't seem very stiff or rigid? Unlike say solid oak? I was picturing solid oak with the speaker mounted to the baffle with a solid clamping system around the magnet would be the way to go? Also doesn't weight play a part too? the heavier the speaker is? or is that just my imagination.
BTW I don't think the heathkit cabs sounded horrible...they kinda sounded not good but after I switched the speakers back into my homemade cabs I realized the the HF leads needed to be switched around I think if I had done that in the heathkit cabs I'd probably still be running them.

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Of course as soon as I posted my reply I saw that you edited your post to add a "BTW" note. If that's the case, I'd definitely tune those Heathkits now that you've got everything wired in phase--you've got nothing to lose but a little time and IMHO worst case scenario it will be a good investment as a learning experience and best case scenario you'll end up with speaker cabs for your Duplexes that will blow you away.....

Ok they're back in the 101's they sound good I'm gonna have to spend a couple days listening to and adjusting them. so far so good. : )

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Originally Posted by cradeldorf

Ok they're back in the 101's they sound good I'm gonna have to spend a couple days listening to and adjusting them. so far so good. : )

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Wow--Nice! No audible resonance issues with the Heathkit cabs, right? Just wondering, did you leave the "shelves" in? Please keep us posted as to how your tweaking of the cabs goes--I have a feeling once you determine the ideal port size (how much to reduce the port size from it's current size) you'll be smiling when you hear how those 604's sound in a great pair of solid, well tuned cabs.......

BTW, I have no idea why those shelves were added and of course can't guarantee the cabs will sound better without them--you may find that just adjusting the port size is all you need to do. I just think that whoever modded the cabs did such a poor job tuning them with that enormous port, that their idea to add the "shelves" (possibly an attempt at "dbr" tuning?) probably didn't work either. But, just to be safe, if you do remove the shelves, you'll want to get them out in one piece just in case the cabs sound better with them in (which I highly doubt). I'd also recommend that if you do remove the shelves--try one cab first to make sure it doesn't "hurt" the sound (before you remove them from the second cab)--less work re-installing two shelves than four (I knew my math skills would pay off someday)......

Hey Vott, I did not do any modifications to the heathkits. I just dropped in the speakers and have been tweeking the sound with the EQ. They do sound better than my cabs.... by a fair amount I think. every time I had small ports the speakers sounded distant and quelled and every time the port is a huge gaping hole they sound light and airy much more like everything is live in your living room. I'm fairly happy now and they look 1000 times better too. I guess I'll stick to building birdhouses. :D

P.S. I loved the TV show Fridays!!!...the sketch with Michael Richards where he's playing with the army men was epic!! I think there was a nativity scene one that was funny as all get out too. : )

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Originally Posted by cradeldorf

Hey Vott, I did not do any modifications to the heathkits. I just dropped in the speakers and have been tweeking the sound with the EQ. They do sound better than my cabs.... by a fair amount I think. every time I had small ports the speakers sounded distant and quelled and every time the port is a huge gaping hole they sound light and airy much more like everything is live in your living room. I'm fairly happy now and they look 1000 times better too. I guess I'll stick to building birdhouses. :D

P.S. I loved the TV show Fridays!!!...the sketch with Michael Richards where he's playing with the army men was epic!! I think there was a nativity scene one that was funny as all get out too. : )

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Glad to hear they're working out so well for you--I agree they're great looking and sounding cabs not to mention that was the easiest way to solve the resonance issues you were having with the other cabs. If they sound that good as is, maybe whoever modified them did successfully implement DBR tuning...... Not a lot of people remember that show Fridays--it was only on a couple of seasons but it was classic! I'm going to change my signature to a different Friday's clip later on....

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Originally Posted by Cal Weldon

Guys, being well acquainted with the EPDM product in question, I can assure you this is not something to decouple your driver from the baffle, it will act as a gasket, nothing more.

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Gasketing was mostly my use, a couple times covered the entire baffle with it. It definitely adds damping though, more in thicker or multiple layers. So I have to disagree a little. Maybe we had different techniques.

You can't use it to hang a speaker though.

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Originally Posted by Old Guy

It definitely adds damping though, more in thicker or multiple layers.

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Yes, in multiple layers that might apply to almost anything. It's 45 mils thick and compresses to around half that when bolting a driver so it's damping factor is reduced considerably by the time you get the density gain. I think that's what I was trying to say, so really it's acting like an air seal.

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So I have to disagree a little.

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Not really, I think we are on the same page.

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You can't use it to hang a speaker though.

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By hanging a speaker do we mean Flying a speaker or hanging drivers or what exactly do we mean here? I'm curious because I am well aware of it's strengths and weaknesses.

Thanks guys, originally yes I was talking about floating the speaker on it, but after reading GM's description of how a speaker should be locked down as tight and as solid as can be with as much weight as possible I see that as usual my thoughts are still 180 degrees away from what should be done. I like the rubber gasket idea though. (thumbs up)