TH-18 Flat to 35hz! (Xoc1's design)

[Djim]

Making a set 'expandable' is always a good thing...




More info about the Cyclops CBe LINK

[kctess5]

Djim aren't those cabinets almost the exact same size? You said it was bigger. I discounted it at first because of that but now that I look its only like .2 cubic feet larger.

So you would suggest that one over the TH-18? Have you had experience with both or just looking at the sims?

That response seems almost too good to be true, but Hornresp is generally pretty good...

Luckily if I decided to go with that design I wouldn't have to change the order at all

[kctess5]

Any chance you could post the hornresp input? That would be quite helpful

[kctess5]

Sorry for the triple post...

I finally got around to re-writing my system output calculator spreadsheet (old computer died) and worked up some figures.

With my original plan: TH-18s @300 watts each......138.7dB max
Original half system: TH-18s @300 watts each........132.7dB max

The revised plan: Cyclops @ 550 watts each...........142.3dB max
Half system (2 subs): Cyclops @ 700 watts each.....137.4dB max

So to recap... I get 3.5dB more power basically for free in the whole system. But even better is the half system, in which I get 4.7dB, thats only 1.3dB down from the original full system output. The amps are set up bridged, instead of just one sub per channel. This not only gives me more power output, but also cuts down the number of cables I need. I don't need 2 10' signal cables I had before, and I don't need 2 25' power signal cables. That substantially lowers the cost, I am able to fit in measuring equipment with the extra budget

[NEO Dan]

Originally Posted by kctess5

Any chance you could post the hornresp input? That would be quite helpful

Agreed. It would be nice to see the Hornresp, I think the difference is that the CBe looks shorter on path length and tuned higher. Also note that there are no actual measurements posted...

You don't need a spread sheet for multiple enclosures in Hornresp, just (crtl)+k and enter the number of boxes in parallel/series...

Fewer boxed = less LF directivity. And IMO 4 boxes is of benefit especially if you are shooting for 40Hz or lower.

Having FB in the heart of the passband increases the thermal load on the driver because it can't move, add some dubstep to that and you'll need some re-cones. Spreading the thermal load across several drivers is an advantage with todays newer electronic material.

The 18PS76 has the spider on the lower landing in the basket = less clearance so it's easier to bottom, proceed with caution as x-dammage is not listed.

[kctess5]

You don't need a spread sheet for multiple enclosures in Hornresp, just (crtl)+k and enter the number of boxes in parallel/series...

I know, its just handy for doing a lot of comparisons fast, and i don't have hornresp on the mac. I just enter sensitivity, power, and number of speakers and it tells me output level at various distances. It's easier than doing each by hand

The 18PS76 has the spider on the lower landing in the basket = less clearance so it's easier to bottom, proceed with caution as x-dammage is not listed.

Using less than optimum power will help in that regard...

It will also help thermally...

My last post wasn't suggesting that I only build half the system, as you say more boxes is better, I only mentioned that because the system will be modular for smalller venues around the school where they won't be using anywhere near 137dB

think the difference is that the CBe looks shorter on path length and tuned higher

Maybe a tiny bit but the F3 of those two cabs is almost exactly the same, looking at the graph.

Fewer boxed = less LF directivity. And IMO 4 boxes is of benefit especially if you are shooting for 40Hz or lower.

Directivity is definitely a plus for this application. I don't need to be playing music for the neighbors. I'm aiming for 40hz solid and then dropping off right after that.



The speakers will face the sitting area, at the edge of the field, about 100' apart.

So to try to get a general consensus...

Does anyone think that 4 cabs @ 550w each will be inadequate for a relatively small high school football field?

[Djim]

Hey guys,

There is nothing 'secret' behind the Cyclops. It shares many things already discovered in the 50ties in traditional horn design, such as split-horns and symmetric loading. Dan, you are right, the extra efficiency is only a matter of more volume and higher tuning. The Cyclops is a proven concept and uses the advantages of an 'Symmetric' load/folding-style.

In a ‘Symmetric’ TH (STH) the 18” driver sits always at the beginning of the horn, rather than the usual 30cm upwards position. That’s why the first system resonance is more closely to the ¼ wavelength of the horn. The result is a steeper roll-off.
Traditional 'Danley-style' TH’s have their driver 90 degrees flipped in relation to the horn. That means at one end of the driver the movement is ‘behind’ and it increases non-linear movement. Because STH’s don’t have a ‘flipped’ driver and use a minimum of two horn channels the forces are more equal distributed (in a symmetric order) over the surface of the cone. Also, every part of the cone has a more or less similar distance towards the mouth. All these things not only lead to an improvement of the linear movement but also improve the phase response, which increase the usable bandwidth.

There are a few things that need attention. Since there is no compliance volume to play with (by the absence of an S1-S2 section) you have less parameter for the horn to tune it. Although some see this as a disadvantage, it is actually not. It means you need to optimise the horn which leads to less system losses in the end. The biggest disadvantages of ‘Symmetric’ TH’s are; they lead to bigger volumes and use more wood. In other words, designing them for 20Hz makes them impractical large and heavy.

Thanks kctess5 for the notification since it looks like I have been uploading the wrong drawing, you need the Cyclops CBX version which corresponds to the HornResp plot I showed earlier. The Cyclops CBX needs a low-cut of 35Hz (or 32Hz for more specialised extended low frequency drivers). You can use a small band eq to improve the roll-off a little.

About HornResp inputs, Staiper (the designer) hasn’t shared them with the community. I can’t blame him since it will lead to needless discussions about the system volume that end up higher than it really is. That is the only way to simulate it with HornResp since the program hasn’t enough parameters to deal with the plenty corners. For instance the dip above 100Hz is not as big as predicted. Staiper did upload a quick measurement between a Jbell SS15 and a Cyclops Standard (smallest version) both loaded with a 15" Eminence 3015lf driver.

[kctess5]

Alright so lets compare these

TH-18 Pros:

• Smaller
• Lower response
• Lighter
• Less wood (cost)
• Better form factor (tilt and roll w/ low center of gravity)
• More tried and true

Cyclops Pros:

• 2dB more sensitive
• Greater bandwidth (not important to me)
• More even cone loading?

So basically I have to decide if it is worth the extra weight and size for 2dB. It looks like I could build them with the amount of wood I am buying anyways (10 5'x5' sheets of baltic birch) so there wouldn't be an added cost. The top end bandwidth isn't very important to me as I will be crossing somewhere between 80 and 100hz.

I was originally going to build 4 of the C/E/X FT30 6 folds, but I went with the TH18 for the added efficiency. So I am reluctant to give any more low end extension up.

I think this might be something to consult the ASB about, as they will be the ones carrying it around. Luckily its a choice I can make even after all the stuff is ordered

[Djim]

Lol, the Cyclops is a year older, a proven concept and build many times (probably more than Xoc1-TH18's). That it is less known on DIY is another matter. If you google more smart you can find out that the Cyclops is especially appreciated for large outdoor events. Actually, that was the original goal of the designer.

Generally speaking, response below 38Hz for outdoors is only practical if enough efficiency and power are available, otherwise its a waist of energy. Remember you want to 'fill' a stadium. When you have limited power the part that you loose to amplify < 40Hz frequencies could be used more efficiently to higher the levels above 38Hz. Like Dan already pointed out the range above is much more important.

But you are right about the downsides, it costs more to build, it is larger, needs two people to move around and has less low frequency extension compared to an optimised Xoc1-TH18 (and it is not optimised yet).

[Tom Danley]

[QUOTE=Djim;3137676]Hey guys,


Traditional 'Danley-style' TH’s have their driver 90 degrees flipped in relation to the horn.



Not always, look up a VTC els118 which will look very familiar and was designed in 2008, put in production in 2009. Also considering the wavelengths involved, would be hard to find an acoustic reason for improved phase response and actually one can’t make that assertion based on measurement unless one has built an identical horn but laid out differently.
Best,
Tom