building jbell's hs12

kzy

Member
2012-10-03 9:58 pm
Hello everyone,

I am building jbells hs12 from this post and came across a problem.

There should be a one inch setback for the grill but if my calculations are right there is not enough room for the driver left. The datasheet for the beta 12-a2 specifies a depth of 4.57 inch which is about exactly the room left but building it I see that I miss about 2/3 of an inch.

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Now to fix it I think I am just going to place the baffle/horn a little to the front. Would the added volume be a problem? I have tried to model it in hornresp but that was a little over my head. I hope somebody who built it as well can enlighten me.

Also, there is a vent located in the back of the speaker. Placing it tightly to the back of the enclosure would close that off and possibly impede cooling. Would that be a problem?

Then I am also worried if placing the driver tightly to the back might resonate or rattle. Should I better keep some clearance with the effect of adding even more volume?

Thanks for your help!
 

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jacobsprod

Member
2016-09-28 9:16 pm
Hello everyone.....I know this thread is a little bit dated, but have been considering building a set of stacked HS12s myself for a sound system. Like kzy, I too noticed that a lot of possible drivers will not fit the cabinet plans as released. I have a set of Delta Pro 12-450s that are an inch longer than the space alotted....even the recommended Dayton 12" really should not fit either.

Have there been any revisions to the dimensions to accommodate deeper drivers. Is it safe to lengthen the box an extra inch or so, so the drivers fit and have room to breath.

Secondly, I plan to use the compression driver option with the Goldwood horn so the cabinets can be stacked vertically.....however wouldn't twisting the horn 90 deg so it goes top to bottom in the cab also change the dispersion of the horn so it throws highs top to bottom at 90 degs and left to right at 40 degs???? How can the dispersion be widened horizontally and minimized vertically???

Thanks in advance......
 
Volume changes of +/-20% are within the error margin. So you can simply make the enclosure deeper. I would suggest that anyway because you are blocking the pole core venting anyway (which is very bad for cooling). Plus, that's much easier than fiddling with the angle and you could at any time add another little box which uses up the same volume and put it in one of the corners.
 
Thanks for the input ICG......I suppose by the time you add a couple recessed handles on the sides, you would lose some volume anyway. I guess you could also add some rigid foam insulation blocks to the inside of the cabinet to lose volume as well and not add much weight at all......

Now to solve the CD horn question.......I am curious what would couple better on a vertical stack of cabs......the GM-500PB mounted vertically, or a GT-300 PB mounted normally in the center of the box. The plan is to stack 4 per side.....

Thanks.....
 
As I said, the volume isn't that critical at all. Ok, it changes the tuning a few Hz, but that's not really an issue.

Well, I have some concerns about stacking though. The problem is the interferences in the HF, you'll get a lot peaks and dips, the phase problems will ruin the dispersion vertically (and/or, dpending if you want to stack horizontally or vertically). From what I've read from your post is you want to stack 4 of the horns vertically. You'd either have to stack them vertically and curve them or do the same the other direction. The problem is, a. the horn doesn't have a constant directivity which makes it not suitable for stacking and b. the horn is too shallow and to narrow vertically in dispersion to work in a stack, the drivers and even the horns itself will be in each others way. That could only be solved by a greater distance of the horns - but that would make the interferences even much worse! Interferences not only cause peaks, they also cause dips/cancellations at certain frequencies/angles.

My suggestion is to just buy bigger and more precise dispersing horns and matching drivers. One 1,4" driver and horn will easily outperform 4 of these horns and drivers with a much better sound. Even a good 1" driver and good horn can outperform them. Remember: Power isn't the key, efficiency is! Even 2 good/stackable horns and medicore drivers will deliver the same spl with better sound than 4 of these horns.
 

jacobsprod

Member
2016-09-28 9:16 pm
Thanks for the input, although I am a bit confused by your reply. My plan was to use the GM500 (or something better suited) and my pile of PRV Audio 280Ti drivers I have on hand.....

I believe in the original posts from jbell that he recommended either the GM500PB for stacking purposes or the dayton conical waveguide for single cabs. The pictures I have seen show the GM500 mounted with the 15" width going vertically.....ie the 90 deg dispersion is vertical, instead of horizontal as it would normally be. I know it is possible to place a diffuser in front of the horn to widen the 40 deg angle back to 90 deg....but I am concerned about the vertical coverage having severe overlap and interference.

Then again, looking at cabinets such as the Dynacord Cobra.....I see they still use a single horn in the middle of the cabinet for HF frequencies.

Thanks....
 
Stacking is used either to cover a greater spl or wider dispersion angle. For both are well defined dispersion angles over the whole frequency band needed, which the horn does not provide. On top of that, neither the horn nor the driver can get low enough for the 12" in the enclosure, the conical horn without a phase plug does not load anymore where the hf driver starts. That means, you will have a hole in the upper mids with that combination and if you stack it, you will have also have interferences, distances between the hf is simply too great.

If you want "loud for cheap, sound doesn't matter", go for it, otherwise use a different combination.