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Keystone Sub Using 18, 15, & 12 Inch Speakers
Keystone Sub Using 18, 15, & 12 Inch Speakers
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Old 8th February 2018, 09:45 PM   #1181
Brian Steele is offline Brian Steele  Grenada
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Quote:
Originally Posted by treukauf View Post
Brian this intrigues me as I would like to get a flat response as close to 30 hz as I can. 35hz Flat would be fine as well. Any idea what sort of maximum spl your revised keystone loses to a traditional keystone?
I'm not sure, but I doubt that it would be much. Bear in mind that the output of the KS is influenced significantly by the shape, size and location of the mouth, which can't be modelled effectively in Hornresp.
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Old 27th March 2018, 05:20 AM   #1182
Cableaddict is offline Cableaddict
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119 pages? OMG. That "PPSL" thread was bad enough!


I'd like to consider A 12" or 15" Keystone design. (The 18" is way too large for my use.)
I assume they are in this thread, somewhere.

Does anyone have that data, already copied & "collated" & can repost it? Just the basic data, with whatever drivers were used:

Dimensions & weight, frequency response, & efficiency? - plus what post #'s are involved.
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Old 27th March 2018, 05:28 AM   #1183
Cableaddict is offline Cableaddict
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Skimming through a little bit, I REALLY like the fact that the removable waveguides can be added for an extra 3 dB or so.

This is a very nice feature for guys like me, where sometimes space is limited. Having them as options, and being able to transport them in a separate space, is a HUGE deal.

I'm still leaning towards PPSL, though.

Last edited by Cableaddict; 27th March 2018 at 05:32 AM.
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Old 27th March 2018, 06:38 AM   #1184
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post
1)119 pages? OMG. That "PPSL" thread was bad enough!
2) I'd like to consider A 12" or 15" Keystone design. (The 18" is way too large for my use.)
3) I assume they are in this thread, somewhere.
4)Does anyone have that data, already copied & "collated" & can repost it? Just the basic data, with whatever drivers were used:
Dimensions & weight, frequency response, & efficiency? - plus what post #'s are involved.
5)Skimming through a little bit, I REALLY like the fact that the removable waveguides can be added for an extra 3 dB or so.
6)I'm still leaning towards PPSL, though.
1) Unlike that thread, this one has actual frequency, phase and distortion measurements.
2) All the Keystone (other than the B-Low) measurements for 2x12" and 15" drivers used the same 45" x 25.5" x 22.5" cabinet. It could be made "thinner" for the smaller drivers with a loss of output.
There are smaller TH available that would fit any size you want.
3) The OP has reference to other posts of interest to the OP and readers ;^).
4) All those details can be found in the OP and references to the pertinent posts.
5) "Waveguides" or "Barn Doors" will increase level in front of any bass cabinet you decide on.
Large road cases can work well as "Waveguides" or "Barn Doors" too. Leave no turn unstoned..
6) The Keystone has a bit more output level than a PPSL bass reflex containing double the drivers using twice the power occupying the same trailer space.
The PPSL would have a few % less THD than the Keystone, as would a standard BR. That said, if not driven past Xmax, I doubt any sound engineer I've met in the last 42 years would notice that the even order distortion had been reduced and the odd order went up in comparison of the two.

However, that 6 dB sensitivity gain requires only 1/4 the power to achieve the same sound level, and in typical "plug the amp in the wall" situations, that four times the power demand can result in voltage drop that severely limits the potential of the less efficient system.
80% of the sound engineers I've met would notice the drop in SPL between the two systems under "brown out", the other 20% would be too effed up to care.

And anyone paying for twice the drivers and amplifiers will notice a difference..

Cheers,
Art

Last edited by weltersys; 27th March 2018 at 06:44 AM.
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Old 30th March 2018, 04:48 PM   #1185
Kageyb is offline Kageyb  United States
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Art did you measure the B&C18TBW100-4 in the regular KS?
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Old 30th March 2018, 08:32 PM   #1186
weltersys is offline weltersys  United States
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Originally Posted by Kageyb View Post
Art did you measure the B&C18TBW100-4 in the regular KS?
No, just in the "B-Low" version.
There are comparative SPL and power estimates with the various drivers in the OP.
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Old 4th April 2018, 12:22 AM   #1187
Cableaddict is offline Cableaddict
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Well, I'm near giving up, as I can't for the life of me figure out what design is best.

The problem with so many of these threads si that the original designer doesn't always explain the pros & cons of the design. That should almost be a requirement.

Also, size and weight of the finished product, once it has actually been built.

And frequency response, of course.
---------------------------------------------------

So Art, here's where I'm at:

I know you think this is the ultimate design for me, but despite your huge amount of correspondance & info (which I am grateful for) you nevver once said WHY this was the right design.

have 2 problems with it.

1: A bit too large, and I assume too heavy. (I can't find the weight listed anywhere, but it must be at least 150 lbs.)

2: I really want to build PP, if possible, to minimize even distortion. Granted, some high-end drivers already do minimize this *using phase plugs or whatever) so who knows.... This is a big problem when building something you can't actually hear first.

As best I can figure, the main advantage of this Keystone design is efficiency. That's great, no doubt, but I don't need the MOST efficient boxes possible, for a given size. I just need a few db more than I was getting with my old sealed Bag End 18's. (2 per side.)
That's not exactly hard to accomplish.

I also don't need these to be near flat at 30 Hz. Reasonably flat to around 38 - 40 Hz is probably more than I need. I'm more concerned with tightness, cleanliness, intelligibility, integration with the tops, etc. I therefore don't see why a 15" version needs to be the same dimensions as the 18" version. Unless I'm missing something. (Always a strong possibility.)
============================

So, WHAT I MIGHT BE ABLE TO USE:

You mentioned a slimmer version. THAT could work. I mainly need something not too deep, as I cluster them in the center and stage space is often a problem. (Also, some managers etc freak out if the subs are too large. Tall, wide, and shallow doesn't "appear" as big as it actually is.
And finally, tall but shallow makes it much easier to move the subs around, and especially to flip them into my pickup truck.

I can deal with 45" high, in fact in some ways that's ideal. 26.5" wide can also work, though that's getting onto the "scare the manager" territory. - But maximum depth is limited by the wheel well in my Tacoma, which is about 42.5", and I'd need about 1/2" for the covers. so 21" deep, absolutely the most.

If that can be done, mayb with a 15" or dual 12", then I would consider this strongly (although I still lean towards some kind of a push pull concept) However, even at 45" x 26.5" x 21", and using expensive neo drivers, I fear these will be awfully heavy.

Last edited by Cableaddict; 4th April 2018 at 12:27 AM.
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Old 4th April 2018, 06:35 AM   #1188
USRFobiwan is offline USRFobiwan
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Keystone Sub Using 18, 15, & 12 Inch Speakers
Since the Keystone is almost the same size as any double 18 used around the world. I do not know why you are trivial about size and weight. For small gigs use small speakers, for big gigs use large speakers. (or a combination) It's that simple.

Also you worries about distortion, I say what distortion? You only distort TH's if you push it TOO hard or use a driver not suited for the design. In my own experience TH designs are exceptional clean in output. Build many (12 or more) and you never ever have to worry about distortion, you can play it at moderate amp settings, you're probably not want to play it louder or else you're bringing down the building.

You don't need to be flat to 30...So crossover it at 31,31,33,.. 50, 60.. whatever rocks your boot.

It seems like you have strong 'feelings' for a PP design.

Why don't you build a prototype of both the Keystone and any PP from cheap ply or MDF. and test it. And then decide. Both are relative simple builds.
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Old 4th April 2018, 04:14 PM   #1189
phivates is online now phivates  United States
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Have a look at the PAL 12, a TH using a single 12"
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Old 4th April 2018, 05:22 PM   #1190
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post

A)I know you think this is the ultimate design for me, but despite your huge amount of correspondance & info (which I am grateful for) you nevver once said WHY this was the right design.

have 2 problems with it.

1: A bit too large, and I assume too heavy. (I can't find the weight listed anywhere, but it must be at least 150 lbs.)

2: I really want to build PP, if possible, to minimize even distortion. Granted, some high-end drivers already do minimize this *using phase plugs or whatever) so who knows.... This is a big problem when building something you can't actually hear first.

3:As best I can figure, the main advantage of this Keystone design is efficiency. That's great, no doubt, but I don't need the MOST efficient boxes possible, for a given size. I just need a few db more than I was getting with my old sealed Bag End 18's. (2 per side.)
That's not exactly hard to accomplish.

4:I also don't need these to be near flat at 30 Hz. Reasonably flat to around 38 - 40 Hz is probably more than I need. I'm more concerned with tightness, cleanliness, intelligibility, integration with the tops, etc. I therefore don't see why a 15" version needs to be the same dimensions as the 18" version. Unless I'm missing something. (Always a strong possibility.)

5: I can deal with 45" high, in fact in some ways that's ideal. 26.5" wide can also work, though that's getting onto the "scare the manager" territory. - But maximum depth is limited by the wheel well in my Tacoma, which is about 42.5", and I'd need about 1/2" for the covers. so 21" deep, absolutely the most.

6:If that can be done, mayb with a 15" or dual 12", then I would consider this strongly (although I still lean towards some kind of a push pull concept) However, even at 45" x 26.5" x 21", and using expensive neo drivers, I fear these will be awfully heavy.
A) I have never claimed any design is the "ultimate" for anyone.
You primarily have complained about distortion.
I have explained many times that distortion is related to three things:
1) Driver design. (phase plugs have nothing to do with LF driver design..) Good designs have little distortion below Xmax, bad designs can have far more distortion even well below Xmax.
2) Driver excursion. More excursion=more SPL and more distortion.
3) Cabinet efficiency-a more efficient design requires less excursion for a given output.
1: Depending on the drivers and type of plywood used, 150 pounds is a reasonable estimate. More weight if Baltic Birch and ceramic magnets are used.
2: If you look in post #758 of "A Thread for those interested in PPSL enclosures", (or on ProSoundWeb), you will note that Mark 100's tests using the his slot load cabinet in both push-push and push pull demonstrates that the BMS 18N862 speaker design using triple shorting rings is not only very low distortion, but also has a very linear suspension and motor in terms of deviation between "push" and "pull".
The even order differences between the "push" and "pull" stroke are cancelled in PP mounting, but lacking that difference, either way of mounting works basically the same, with the exception of the suspension and coil vent noise more audible with a "reversed" driver.
In other words, don't expect push pull to "improve" good drivers.
3: You say you don't need "much more" efficiency , but complain of distortion at low volume in your 2x12", and not enough output in your 18". See "A".
4: Any version of the Keystone could be made thinner (reducing the 26.5" dimension) without affecting the basic frequency response, just reducing efficiency. Reducing depth would reduce path length, which would reduce LF output. The Keystone Response drops below 37 Hz.
5:Get a trailer!
OK, since you won't do that, you could cut the Keystone in half making two cabinets using 12"
drivers, exterior dimensions 45" x 22.5" x 13.75", go three wide and one sideways on the tail. The Keystone exit was done empirically to get the optimum blend between LF output and upper smoothness, that process would be required again for the thinner cabinet, though reducing the width of the exit by 50% and retaining the same aspect ratio would be a good starting point.
6: A pair of the "split" Keystones would be about 1/2 sheet heavier than one due to the extra side-wall wood, but would come in under 100 pounds each.

Cheers,
Art
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