Tapped Horn Questions/Advice

[wreckingball]

Hello People,
I posted a couple of of times on Art's Keystone Sub thread, and don't wish to clutter it further, searching for advice with my particular driver.

In his last reply to me, he referenced the Dayton PA385S-8 for use in the Keystone, but upon later research, I only found a handful of posts that specifically use these drivers in the Keystone. (Principally the experimental B-Low version).

I found these drivers on clearance for $99, happy about the price, I picked up a couple...

But before I make any sawdust, I thought I'd try to confirm If these only work (as measured in post 1167{with the step-down cover}) in the B-Low cabs, as opposed to the regular sized Keystones..?

Enough for now, thanks in advance for any and all help...🙂

 

[wreckingball]

I see now that the sub in post 1167 is 48" tall, which is perfect for using my standard 4'x8' sheet of BB.

Also, I hope I didn't (but probably did) just miss something in the posts of that thread.. *sigh* such is life, living with ADD..

Again, any further help would be a blessing..😉

 

[weltersys]

I posted a couple of of times on Art's Keystone Sub thread, and don't wish to clutter it further, searching for advice with my particular driver.

In his last reply to me, he referenced the Dayton PA385S-8 for use in the Keystone, but upon later research, I only found a handful of posts that specifically use these drivers in the Keystone. (Principally the experimental B-Low version).

But before I make any sawdust, I thought I'd try to confirm If these only work (as measured in post 1167{with the step-down cover}) in the B-Low cabs, as opposed to the regular sized Keystones..?

The Dayton PA385S-8 frequency response was very similar to the BC18TBW100-4 in the B-Low version, I'd expect it to work OK in the standard Keystone as well, other than not having as much output potential and higher distortion.

 

[wreckingball]

Thanks much for the reply Art,

Well, It'd be just my luck if the Dayton didn't work nearly as well in the standard Keystone, so I reckon I need build the B-Low version...

Quick question: Did you adjust angles of the 'dividers', so that the 'turn-arounds' had the same measurements?

It would seem to my way of thinking, that if you kept the angles the same, those 'turn-around' dimensions would be a bit off...hmmm *edit* I could be way off on this, (ADD's a bitch to deal with, especially in my 50's)

Example: The first turn-around has the dimensions of 3.75, 4.42, and 4.375 inches respectively. (On the 'regular' Keystone)

Just wondering before I make any sawdust, also, I've attached the PDF plans. (*edit* they don't seen to be working properly, sorry)

If you didn't, I'm wondering if this is what Mr Steele was getting at with his various (mostly 3rd) revisions.

Cheers,
-Steve

 

[weltersys]

Thanks much for the reply Art,

1)Well, It'd be just my luck if the Dayton didn't work nearly as well in the standard Keystone, so I reckon I need build the B-Low version...

2)Quick question: Did you adjust angles of the 'dividers', so that the 'turn-arounds' had the same measurements?

Steve,
1) Since the Dayton PA385S-8 was so similar in frequency response to the BC 18TBW100 in the tall version, it's response would probably also be similar in the standard Keystone.
2) Attached are some measurements, some changes were made to the bracing to facilitate the addition of a pole socket ("Top Hat") and a ratchet strap retainer eye-bolt.

Good luck!

 

[wreckingball]

Thanks once again for the reply and the additional information Art,

OK, since you mentioned that the drivers are very similar once again...
I've decided to build a test box of the smaller version and see if the response is similar.

One more quick question, can the step down plate be used on the regular Keystone?

Cheers,
-Steve

 

[Brian Steele]

I suggest measuring the t/s parameters for those drivers before committing to any build.

 

[wreckingball]

Will do..thanks Brian..

After burning them in a couple days, I'll see, but if any are out of published specs, they can be sure I'll be sending them back...

The latest advert for them claims; "11mm of Kippel-verified XMax"

That's fine and all,. but doesn't verify the rest of the TS's..

Like I said, we'll see..

Cheers,
-Steve

Oh... while on the subject of x-max, just off the top of my head, I have a SI DS-4 that I could use in another Keystone...
TS's attached...

Not a Pro Driver per se'... but do any of you think it could stand the rigors of road use? ...

Thanks again,
...Steve

 

[weltersys]

One more quick question, can the step down plate be used on the regular Keystone?

Steve,

As mentioned in the Keystone OP, "The lower frequency response corners using a partially covered exit, ("step down" mode) is in #262."

 

[wreckingball]

I'm thinking I may swap out speakers down the road to the B&C 18"when I get more $$. (then using the 15's to replace aging EV 15's on a bass guitar rig)

Thing is, how would I go about adapting an 18" cutout to my 15" 's that I currently have?

I read somewhere in the KS thread about a donut hole adapter ...what's the best way to construct one of these as to not mess up the response of the horn?

Thanks in advance.
Steve A

 

[weltersys]

Steve,

If you think you may use B&C 18" later, best to cut the holes that size prior to building the cabinets. Then make the "donut hole adapter" large enough to cover the 18" cut out, with a 15" cut out inside. Front mount the 15" on the adapter, then install the adapter/15" driver like you would an 18".

 

[wreckingball]

Well, decided against the B-Low version as there is that real nice PDF to guide me building the standard version.

And I couldn't help myself ..went ahead and ordered 2 of the B&C drivers, so I'm building 2 using those and 2 using the Daytons.

I'm thinking I like the 10" step-down plate's response in the graph you posted, but that was on the B-Low version... hmmm.. I'll just test after I'm done building..

But for clarification, when you say to cover the top portion, say, 10", you mean vertically and not 10 square inches, right?

Also, the ratchet strap eye-bolt retainer ..is that to assist the top-hat pole stability-wise, or... ?

I know those questions sound very rudimentary, but whenever I mess something up, it's usually something very simple ..and bam! there goes another trip to buy a couple hundred dollars worth of supplies...ughh..

Thanks in advance..

 

[weltersys]

I'm thinking I like the 10" step-down plate's response in the graph you posted, but that was on the B-Low version... hmmm.. I'll just test after I'm done building..

1)But for clarification, when you say to cover the top portion, say, 10", you mean vertically and not 10 square inches, right?

2)Also, the ratchet strap eye-bolt retainer ..is that to assist the top-hat pole stability-wise, or... ?

1) The various "step down" sizes probably refer to the reduction of the Keystone exit vertically, but without the thread post #, hard to know exactly what you are referencing.
2) The ratchet strap eye-bolt retainer is used to triangulate the top cabinet while using a long pole mounted in the sub's top-hat, while also providing something to hang on to when tipping the cabinet back on a two-wheel dolly.

 

[wreckingball]

Disregard last questions, I sorted things out.

 

[wreckingball]

Whoops, posts overlapping here. Yea, I sorta figured that out about the eye fastener.

Post #1167 in Keystone thread has the graph I was referencing...
10" step down seems a good compromise between a lower, LF corner vs reduced output ..but like I said, that graph seems to be tied to the B-Low version. (I'll have to experiment/measure, unless of course, you have a graph of the step-downs using the standard KS laying around).

I just wanted to clarify that the 10" measurement meant fully closing 10" from the top of the KS opening down, and not a cover whose area is 10 square inches or some such thing.. (almost positive it's the former after re-reading the KS thread)

Cheers,
--Steve

 

[wreckingball]

D'oh..RE-read #262, I have the graph, just want to confirm the last question about the 10" measurement..

Sheez... *******' losin" it...😱...

 

[weltersys]

D'oh..RE-read #262, I have the graph, just want to confirm the last question about the 10" measurement..

Sheez... *******' losin" it...😱...

Steve,

Better if you post questions about the Keystone Sub in the Keystone thread!

Post # 262 shows response with the Keystone exit partially covered, but the description is wrong- oops.

"TH18S20" has the upper 5 inches of the exit covered with plywood, the exit measures 20" from bottom to top. The "step down" cover results in as much as an 8 dB increase in 30 Hz level (with only 8" from bottom to top left open), but with progressive losses in the upper bass range, so for most music the trade off is not worth the extension, which results in a peak around Fb.

I'd suggest making the cabinet with the standard 25" exit, and "T-nut" a cover plate over the exit if you want a lower tuning with less upper headroom.

Art