Let's Build a Driver Test Box

[djk]

http://www.ehcknobs.com/selector//index.php?action=step3&family=53PSE&links=TRUE

http://www.penn-fabrication.com/cart/PreCart.asp?id=G0770

[BEC]

Dennis,

Thanks for the links.

Bob

[BEC]

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On 10/2/2004 2:01:20 AM DeanG wrote:

LOL

How's it coming together? Do you have a nice balance between the squawker and woofer?

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Dean,

The thing sounds very nice. Much better than I expected for the first shot at box, crossover and everything. In fact, nothing I can hear indicates any change is needed. It sounds very much like the Lascala that I have it paired with now with about 3db (by Radioshack meter) less sensitivity and MUCH lower bass. No measurements on how low the bass goes yet, but that difference in bass is dramatic when listening to the new box compared to a Lascala. Those differences were expected and were part of the design goal. It still surprised me with how good it sounds. I think I will go ahead with the order of a second cabinet from the cabinet shop on Monday. I really want to hear a pair of them now.

Bob

[fini]

Bob,

I have the same concerns about the screws into mdf as Henry has expressed. Threaded inserts are a good idea. Another possible temporary attachment option would be to use toggle clamps:

Here are some more links for your collection :

http://www.mjvail.com/destaco/intropage3.html

http://www.mjvail.com/destaco/destaco20.html

You might consider protecting the corners of the cabinet if it's going to be moved around a lot. Also, I'd brace the top section of the motorboard before it snaps off at the top of the LF section. Or, you could get the shop to make you a plywood motorboard...

[BEC]

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On 10/2/2004 9:25:11 AM fini wrote:

Bob,

I have the same concerns about the screws into mdf as Henry has expressed. Threaded inserts are a good idea. Another possible temporary attachment option would be to use toggle clamps:

http://forums.klipsch.com/idealbb/files/52020.jpg">

Here are some more links for your collection

:

http://www.mjvail.com/destaco/intropage3.html

http://www.mjvail.com/destaco/destaco20.html

You might consider protecting the corners of the cabinet if it's going to be moved around a lot. Also, I'd brace the top section of the motorboard before it snaps off at the top of the LF section. Or, you could get the shop to make you a plywood motorboard...

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Fini,

Thanks for the links. I don't know if you can see in the pictures, but the squawker horn is supported at the back with a metal bracket. That eliminates the "bending" effect that an unsupported squawker horn and driver would otherwise place on the motor board. The cabinet shop will of course make it out of any 4 X 8 X 3/4 material that I want. The cost would be somewhat higher using almost anything other than MDF. Probably going to the next step up in material to something like cabinet grade 3/4 inch maple plywood would add around $25.00 to the cost of each cabinet. I of course built the first of these as simply shop test speakers. Many improvements to the cabinet could be easily made to make them more fit for the living room. The way they are made now, they require a bit less than one sheet of material per cabinet.

Bob Crites

[sfogg]

Bob,

Found the link on the mounting method I was talking about.

Check out how these woofers are mounted:

http://home.comcast.net/~klone-audio/page13-12Shiva1.html

Shawn

[BEC]

Shawn,

That certainly looks like something that would work. I hope to find something quicker and simpler as far as the mounting process goes. The main problem is that if the woofer is mounted from the front, it is a relatively heavy chunk with nothing really to hold on to. The gasket extends far enough out the front to grasp it, but the gaskets are just barely glued on the new ones. I loosened the gasket on the first one I tried to install and had to reglue it. A permanent "lip" of some sort to hold the bottom of the woofer in place would help on installation since that would allow one to hold on to the frame while tilting the woofer top back and inserting the bottom inside the lip. Taking it back out though brings back the problem of the gasket being likely to be pulled off. Before someone suggests putting in the woofer while the cabinet is on its back and taking it out (and catching it) while tilting the cabinet forward needs to consider that the cabinet is heavy.

Bob

[D-MAN]

If it is strictly for use as a test bed, and looks don;t matter, why not use carraige bolts and wing nuts?

Mount the driver from the front (wing nuts out) with bolts from back of baffle.

An alternative is to use a separate motor board, again on wing nuts. This is what I do and it makes for relatively fast and easy driver changes.

DM

[fini]

How about this, utilizing D-man's separate motorboard idea:

The separate motorboard for the woofer could be like a door, hinged with a piano hinge at the bottom. Some type of door weatherstripping could seal it. When you want to mount or unmount a woofer, open the door, which can be stopped horizontal with a wooden block (propping-up the "door"). Mount the woofer from the inside, using either through-bolts with nuts, bolts and threaded inserts, or a clamping device. When the woofer is firmly attached, raise the door. securing it to the box, in whatever fashion desired. You'd have to make sure the "door" opening was big enough to pass the "swinging woofer."

[BEC]

Fini and D-Man,

I did consider that method at first but was worried (perhaps wrongly) about the vibration possibilities of that method. Anyway, I am having another box built now the same way as the first except with a place to mount 3 tweeters across the top. Before you think I have gone tweeter crazy, this one replaces the box that I now have on top of one of my Lascalas. I use it (and will use the new one) to test tweeters after I rebuild them. I can compare one to a "standard" tweeter that is always installed and can match up a pair of them. A switch arrangement will select one at a time.

Still mulling over the quick change woofer problem and I do appreciate the suggestions.

If anyone should want one of these built, let me know. The price of building one is not bad. Shipping is pretty easy since the basic box is about 24 X 24. Would be heavy though.

Bob Crites

[IndyKlipschFan]

I love the CornScala Idea myself!!

Since we know the internal size or a Cornwall box is ideal for the 15" woofer... (Klipsch has a box that is used in the "Cinema line" that is basically a Cornwall sized box just with the 15" bottom woofer only. JBL also has a box that just has the woofer that is almost exact to a Cornwall size wise... So we know were on to something here?)

Loud speakers that are "taller" e.g. the K horn seem to fill a room so much better?? why not have the bottom of the Cornwall box be the size if the cornwall.. And the top section separate like you have done "on top" of that. I see many opportunities to really fill a room better, plus allow Klipsches engineering expertise in the correct size for the woofer / box here, while also allowing for that wonderful larger Klipschorn/La Scala mid horn to finally be used with the tweeter as well.

So maybe this is better called a Klipschwall.. (top end a Klipschorn/ bottom a Cornwall?)

Just a thought?

[D-MAN]

Bob,

I have done it both ways with the wingnut thing.

Vibration is not a problem with either, but the motor-board method would require some weather stripping to seal effectively (and also prevents vibration).

If I was to do it, I would do the 4 carraige-bolts aligned in an X for mounting the driver frame. Basically stick the driver on the bolts and tighten wingnuts down.

Mount the 1/4" x 2" x 20 carraige bolts from the back of the baffle board, threads forward. Add 4 wingnuts and your golden for less than two bucks.

That way, no tools required - swapping drivers takes less than a minute. If you find that for some reason you don't like it, remove the bolts, fill the holes and there you go, no harm done. You won't need more 4 bolts to hold the driver effectively, Altec A7's (VOT) use the same method and have worked great for 50 years.

DM

[BEC]

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On 10/4/2004 10:45:33 PM IndyKlipschFan wrote:

I love the CornScala Idea myself!!

Since we know the internal size or a Cornwall box is ideal for the 15" woofer... (Klipsch has a box that is used in the "Cinema line" that is basically a Cornwall sized box just with the 15" bottom woofer only. JBL also has a box that just has the woofer that is almost exact to a Cornwall size wise... So we know were on to something here?)

Loud speakers that are "taller" e.g. the K horn seem to fill a room so much better?? why not have the bottom of the Cornwall box be the size if the cornwall.. And the top section separate like you have done "on top" of that. I see many opportunities to really fill a room better, plus allow Klipsches engineering expertise in the correct size for the woofer / box here, while also allowing for that wonderful larger Klipschorn/La Scala mid horn to finally be used with the tweeter as well.

So maybe this is better called a Klipschwall.. (top end a Klipschorn/ bottom a Cornwall?)

Just a thought?

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I think the possibilities are extensive for a speaker system starting from a basic bass box like this one and working on various high frequency "tops" for it. The basic one I had built has the motor board extending to approximately the height of a Lascala. A bit longer motor board would put the mid and tweet at the height of a Khorn. Of course the bass motor board could just end at the top of the bass cabinet and a separate HF box could set on top. Here is one that popped up inside my warped mind. Buy a set of Bose 901 with trashed drivers for almost no money. Rip out the old motor board from the Bose and put in a motor board with cutouts for a K-401 horn and a K-77 tweet. Call that one a "Bosewall"

Bob Crites

[IndyKlipschFan]

Call that one a "Bosewall"

LOL Only if you fire the mids and highs back at the corners of the room instead of forward????

[D-MAN]

Bob, BTW, those cabs DO look extremely nice. Seems a shame to not finish them for front-room display... I too like the idea of separate top and bottom cabinets.

You might consider selling flat kits, being cheaper and easier to ship.

DM

[BEC]

D-MAN,

I am sure the cabinet guy would provide them anyway anyone wants them. Since they are now in his CAD program that drives his CNC router, changes are easy and of course left flat for shipping would likely save a bit of money he charges for assembly. I should mention though that the guy can put that cabinet together so fast that he just looks like a blur to me, so, I doubt not being assembled would save much on his charge.

Now, a question. I know that I need some padding on the inside of the bass box and I am looking for suggestions on easily available material for that. I wanted to do a bit of testing first to see what difference a lack of padding inside would have and have done that now. I have a peak at around 100 hz and a dip at around 300 hz. Other than those two points, the response is very flat down to around 30 hz. At that point it drops off smoothly at the rate of about 2 db per hz down to 27 hz which is as low as I attempted to measure.

I have seen that something called "open cell" foam seems to be the thing to use for the padding but have not found any foam locally that calls itself "open cell". Some seem to use the "egg crate" foam and that stuff looks like it would be good but again, they want it to be "open cell".

Any suggestions?

Bob

[Klipschfoot]

You mounted the woof on the front and the horns on the rear of the motor board. Is this scientificly sound? I have read a few thoughts on horns' dispersion being affected by the thickness of the motorboard.

I have a couple of cabinets that are a little larger than Heresys. I have crossovers that are from decorator Cornwalls. I am planning a "Cornwall" knockoff sometime in the future if I get the drivers (or compatibles) cheap enough. The motorbard is universal in that it can be unscrewed from the box, similar to your model.

I like the open view to the horns. Could this be a precedent to have separate bass bin and horn "enclosures?"

[BEC]

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On 10/6/2004 8:46:16 PM Klipschfoot wrote:

You mounted the woof on the front and the horns on the rear of the motor board. Is this scientificly sound? I have read a few thoughts on horns' dispersion being affected by the thickness of the motorboard.

I have a couple of cabinets that are a little larger than Heresys. I have crossovers that are from decorator Cornwalls. I am planning a "Cornwall" knockoff sometime in the future if I get the drivers (or compatibles) cheap enough. The motorbard is universal in that it can be unscrewed from the box, similar to your model.

I like the open view to the horns. Could this be a precedent to have separate bass bin and horn "enclosures?"

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Just my own experience tells me that it doesn't matter much which side the horns mount on. I often test tweeters that I repair by just placing the repaired one on top of a Lascala and switch between the repaired one and the one in the Lascala to see that they are the same.

Of course, I have installed drivers in this test box with the idea of making them easy to change out as the whole thing is made (in this first case) as a driver test box. I would likely have mounted the woofer on the back of the motor board if I did not want the ease of removal the the front mount may give.

Bob

[Frzninvt]

Bob, the material you seek to line the walls of the bass cabinet is available from Parts Express. I bought some to line some '86 Cornwall II's that I had since they come with nothing inside them but bare walls and had an audible echo when you knocked on the side of them. I will see if I can dig you up a part number.

[Frzninvt]

Here is what I used.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-516

I attached it with Scotch 77 Spray Adhesive after cutting the pieces to fit in the cabinet. It did made a difference in the smoothness of the bass response in the '86 Cornwall II and removed any cabinet resonances.