Keystone Sub Using 18, 15, & 12 Inch Speakers

maybe we would know if they would post a complete spec sheet....

There is a spec sheet at Usspeaker.com that looks complete for this woofer. If not then how about double 15TBW100's? My church is building a new building and the sound engineer told me he wanted 25hz. I just thought maybe we could do something DIY, because there arn't many options that low. The room might be something like 5ox70. Need 4 cabs that get to 25hz. Originally I thought about telling them about the new Danley BC218 that goes to 25hz, but that's going to be very expensive.
 
Widening the cab and using two 15TBW100 would work, but the Keystone response is around 20 dB down at 25 Hz. Josh Ricci's Gjallerhorn can do 25 Hz well, or his Othorn for around 28 Hz IIRC.

Art


Thanks Art,

I thought about those two, I just thought that your design seems a much easier build. I think maybe the Othorn would be my choice, close enough to 25hz and if used in a block of 4 maybe further extension.

Shaun
 
Hey Art,
Have you ever measured the impedance of the Keystone? You can do that with REW on a Mac or PC. It would be nice to know FB, I'd guess it's in the mid 30's but I'd really like to know.
Dan,

No, never measured the impedance, but checked Fb by measuring excursion, Fb was 36 or 37 Hz as I recall. There are excursion measurements at 5 Hz increments of the various speakers tested in post #1.

Art
 
Thanks Art,

I thought about those two, I just thought that your design seems a much easier build. I think maybe the Othorn would be my choice, close enough to 25hz and if used in a block of 4 maybe further extension.
Shaun,

You won't see further extension in TH in multiples, just smoother response and the usual +12 dB for a block of 4, plus a bit more on axis sensitivity than that due to the increased frontal boundary. The Keystone has a larger frontal area than the Othorn, so would show a slightly better increase in forward gain than the Othorn.
The Keystone design could be made taller for a longer path length to extend the frequency response lower.
 
Hey art did you ever directly compare your keystone to a JBL srx 728?
I compared the WS 2xLab12" bass reflex cabinet to the SRX 728, and by duplicating the same drive settings have compared the BC18SW115-4 loaded Keystone to it, so the comparison of the frequency response and sensitivity is as in the graph below.

JBL mistakenly published the Xlim/Xmech rating for the 2268H woofer used in the 718 and 728 in place of the Xmax rating, more than double it's actual Xmax of around 8mm. The BC18SW115-4 has almost double the Xmax of the 2268H, so a single Keystone can almost equal the output of a pair of SRX 728.

Art
 

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maybe we would know if they would post a complete spec sheet....

Shaun,

You won't see further extension in TH in multiples, just smoother response and the usual +12 dB for a block of 4, plus a bit more on axis sensitivity than that due to the increased frontal boundary. The Keystone has a larger frontal area than the Othorn, so would show a slightly better increase in forward gain than the Othorn.
The Keystone design could be made taller for a longer path length to extend the frequency response lower.


Hi Art,

Can you work up a 28-30hz Keystone in your spare time? And decide which is better, (2)15TBW100's or single BC18SW115-4. Might be advateges of spreading the load through 2 drivers with less Xmax. Also there is a size discrepancy of 2 vs 1 driver; smaller and lighter being the single 18.

Thanks Shaun
 
just makes me shake my head..... why do people rate the 728 so highly? I've got a couple people running around with CLONES of the 728 and they get plenty of gigs on the 728 name alone.


The 728 pre-dates a lot of the so called 'super woofers' that are now on the market, even to this day it has a respectable output/size/weight ratio and there is enough of them in the wild you can rent more when needed.

We own 12 728's along with a pile of 725, 715 and 718. They are manageable when moving them by yourself and rider friendly up to a certain point. You can pick them up used for not much more than woofers and lumber for a lot of the popular DIY subs.

That said, I concur with Art's assessment of the Keystone VS 728, the Keystone is my first experience with a Tapped Horn and I never expected a single 18 to do what this sub can do.

Hyperbole mode on: chest thumping, nose tickling bass even when you're a few feet away, at close range it makes you light headed. Sticked my head in the mouth to check excursion made me feel down right dizzy.

I've stood in front of stacks of BR subs that didn't have that effect, the only single sub I've personally experienced that bests the Keystone is the super sized sized Jason Audio J61HPs, and those are still loaded with a pair of 2242s and could house a lower class family.

The Keystone has definitely piqued my interest in Tapped Horns.

Hyperbole Mode off: I'll try to get some hard data to back up this gush fest I've subjected you guys to.


Sent from my iPhone using Tapatalk
 
just makes me shake my head..... why do people rate the 728 so highly? I've got a couple people running around with CLONES of the 728 and they get plenty of gigs on the 728 name alone.

I don't rate it high I was just asking because it's such a POPULAR cabinet. So it's a great "benchmark" so to speak, and for the spreading of information...someone can say ohh I heard the 728's, how much better are the keystones? Then they can go from there. Ya kno?
 
Hi Art,

Can you work up a 28-30hz Keystone in your spare time? And decide which is better, (2)15TBW100's or single BC18SW115-4. Might be advateges of spreading the load through 2 drivers with less Xmax. Also there is a size discrepancy of 2 vs 1 driver; smaller and lighter being the single 18.

Thanks Shaun

Also, I don't want to loose SPL. Is there a way to not loose SPL with the Keystone sub when lowering to 28-30hz extension?
 
Also, I don't want to loose SPL. Is there a way to not loose SPL with the Keystone sub when lowering to 28-30hz extension?

Going to a lower tuning in the same size cabinet lowers voltage sensitivity.
Also when lowering tuning excursion demands go up even if you make the cabinet bigger to try and get back some of the sensitivity.

2- 15TBW100-8's in 1 cabinet, you could try 1- 21SW152-4"?
 
Great stuff! The curve suggests tuning around 34 Hz as another poster has indicated. The flattened impedance dip around 70 Hz and the slightly misshapen peak above that suggests the possible impact of panel flex, but it would take more testing to confirm if this is the case.

I'm new at this so whatever measurements I make - take with a grain of salt. Panel flex would not surprise me - the cab vibrates a lot. Overall the construction is pretty tight though. The 3/16 gap at the top right face panel section is the worst one on the box (oops) - cut everything with a skill saw and carbide blade. I used TiteBond, deck screws, and sub floor adhesive to seal all joints so no air leaks or rattles.

When choosing wood I went for a serviceable quality within a budget - not marine grade or anything - it's an oak veneer 24/32 9 ply as I recall. It is not too bad for voids but a bit softer/less dense than the good stuf. I figured the oak would give me a tough exterior surface under the planned Duratex coating.

I'm looking forward to running some sweeps with REW as soon as I get time. I want to see what the response looks like compared to what I am hearing - because what I'm hearing is excitingly good.