FINALLY, RTA trace of half of WiSound(4xTHT, OTop 212s)

[la malta]

Hi everyone. First I want to say thanks to Justin once again for letting me come by and check out his system. Half his set-up was in Buffalo which made it really nice and easy for me to come hear it. I did bring 2 of my DIY vented 18"s but I didn't bother doing an RTA. By the time we did the a/b between the 2 sets of cabs I heard pretty much what I needed to hear.

I think probably the easiest thing for me to do is list my observations in somewhat chronological order and write up a conclusion at the end. So...

1. Speakers were very LIGHT, at least in comparison to my cabs. It almost made me nervous for some reason, like it wasn't "strong enough". My 18"s are made of 3/4" Aruaco with a non-neodymium driver in them and a heavy expanded metal grill, 30" x 22.5" x 30". Definitely a difference in weight, and a balance there of since I always carry my speakers from the front where all the weight is and my buddy will get the back. Conveniently Wi built his THTs 24" wide which is exactly how wide I was going to build my T36s, so it was nice to get a real perspective of the size and weight of what I will be dealing with if I choose to build them.

2. We fired up 4 of his cabs and listened to some dub-step and DnB with the otops before we did an a/b of our cabs. Sure enough its hard to explain at first what it was that I heard from the bass of his THTs which was my primary focus, and it is likely that Bill will say it is what bass should sound like with less distortion. I will agree and accept that. It was quite pleasant.

3. When it came down to the a/b of our cabs its hard for me to say objectively that either one sounded "better" I suppose. Sure enough I'm more used to my speakers and accustom to how they sound, but I was undoubtly impressed by the THTs, particulary in that they seemingly put out quite a bit more volume. Since there was an impedance difference between the two 18"s and 2 of his horns we guesstimated at giving them equal amounts of wattage by most unscientific methods I'm sure. What is not in question is how impressed I was at the volume coming out two 13" drivers in comparison to my monster 18"s, though this may not surprise any of you at all. What I made most note of also was how his horns seemingly "carried" out to longer distances than my subs. I realize this may not make sense as both speakers should follow the 6db down of every doubling of distance rule, but it is just the impression I got. My theory behind this is perhaps having matched volumes at close range we were getting the harmonics etc. of my vented 18"s up close making them seemingly more loud then they truly were and quieter than expected at a distance, whereas the horns are free of these harmonics? Who knows.

4. Wi had my RTA figured out in like 15 mins probably better than I do, with the behringer RTA mic on one of those flexy mic stands that we had sitting on top of my subs to raise it to proper height. Like I said it doesn't have a whole lot of options and frankly it being behringer might make it suspect. At points in the demo we had turned down EQ sliders and did experimentation on different low frequency cuts, and I will say that in my most humble opinion I DID in fact notice a difference in cutting out frequencies below 30hz, even down to 20hz as I recall. Now, whether this was just simple tactile feeling or unmusical rumble as noted by jcmbowman I don't know, but I did find it rather enjoyable with the music both Wi and I cater to. So my dilemma of choosing between the t48 and t36 got a hell of a lot easier for myself, pretty much ruling out the t48.

I have to go to work now but at some later time I will post my opinions of the Otops and other general observations of the evening. Again thanks bro for giving me the demo, and no problem for the stella! I'm sure I'll see you fairly frequently in our travels.

[Bill Fitzmaurice]

What I made most note of also was how his horns seemingly "carried" out to longer distances than my subs. I realize this may not make sense as both speakers should follow the 6db down of every doubling of distance rule, but it is just the impression I got. My theory behind this is perhaps having matched volumes at close range we were getting the harmonics etc. of my vented 18"s up close making them seemingly more loud then they truly were and quieter than expected at a distance, whereas the horns are free of these harmonics? Who knows.

We know.
http://billfitzmaurice.net/phpBB3/viewt ... f=10&t=999

[la malta]

Well, yea, it was more of a rhetorical question I guess.

My impressions of his otops were initially that they were LOUD. They also sounded better to me the farther out we walked which is kinda odd since he had melded arrays, but I think it was just because it was too loud while we were getting up close to tweak the rack etc. Justin got the system to a desireable EQ curve and thats when we both agreed it sounded very damn good. There is not a doubt in my mind his 4 THTs and pair of otop 212s could handle a fairly large gathering of people outdoors.

I know Wi has gotten criticism for his choice of horn sub and drivers, and I realize he and the rest of you know more about this sort of thing than me. But if there was any question on the overall volume or quality of his system I'll just flat out say I was very impressed.

Conclusively, if when we cut out the 20, 25, 31.5hz bands of sound that's actually what was happening, I can verify as best as I can recall that I did hear a noticeable difference in bass. I know the RTA curve is probably not ideal but I hope it provides him and the rest of you with some kind of closure or further knowledge, or perhaps debates.

My decision between building the t36 or t48 is more or less solved. I imagine Wi's decision on building the THTs, besides having some suitable drivers on hand was probably based on a similar dilemma, of the t36 vs t48 situation being a matter of extension vs spl at given frequencies. Judging by the charts it seems like a THT vs t36 is more of the same situation with the t36 being louder at frequencies but the THT having a longer horn so it plays lower? Don't know. I imagine whether anyone actually needs to go lower than 20hz is probably a whole other debate, but in the end I have to give Wi a "hats off" in that he HAS a system that can go there regardless. It was awesome, bro.

Perhaps further thoughts on this later.

[bitSmasher]

I want to do a wharehouse gig someday, I think that would be just plain fun

Rattling corrugated iron roofs with bass alone is great, warehouse reverb has to be experienced to be appreciated - it's a sound that etches in your mind forever.

I'd love to see what sort of SPL you can generate down low with these boxes, that'll be your next challenge.

[phil]

Why is the same size Tuba36 not near as flat as the THT? The home theater part of my cd didn't work so I can't look at the plans right now.

I was going to build a herd of t36's, but now I'm seriously considering the THT's.

[Bill Fitzmaurice]

Why is the same size Tuba36 not near as flat as the THT?

Because it's not supposed to be. It has higher sensitivity above 50 Hz where the bulk of music requirements lie. And don't forget this is a trace of four THTs, not one. If you're not familiar with this: http://billfitzmaurice.net/phpBB3/viewt ... ?f=1&t=398
you should be. T36 is intended for use in pairs or more, preferably V coupled, which flattens response. THT is intended for use as a single cab, so it has flatter response but lower average sensitivity.

[Sydney]

phil: I encourage you to read the various horn articles that have been published; particularly audioXpress 2/07 The "Tuba HT".
The 1st paragraph established the Tuba HT is "specifically for home theater". And how it differs from a horn designed for Pro-Sound.
"The Tuba HT sacrifices broadband sensitivity for flatter response ...when compared to Tuba36S"
Speaker designs ( horns included ) can be optimized for a particular goal, but there are always compromises involved.

[la malta]

Should one presume that 4 t36s vs 4 THTs would be louder and become flat as the THTs once they become grouped in 4?

I don't mean to ruffle any feathers, I just ask because I've always found this SPL chart of the t36 in groups (http://billfitzmaurice.net/phpBB3/viewt ... f=12&t=541) to be sort of funny in that the frequency response doesn't even out or become flatter to lower frequencies with the trace of 4 compared to a single cab.

Best regards.

[Bill Fitzmaurice]

Should one presume that 4 t36s vs 4 THTs would be louder and become flat as the THTs once they become grouped in 4?

I don't mean to ruffle any feathers, I just ask because I've always found this SPL chart of the t36 in groups (http://billfitzmaurice.net/phpBB3/viewt ... f=12&t=541) to be sort of funny in that the frequency response doesn't even out or become flatter to lower frequencies with the trace of 4 compared to a single cab.

Best regards.

It would take at least 16 T36s in half space to flatten the response all the way down. With boundary loading, less. With boundary loading and V coupling, less still. Add in cabin gain, again less. Wi's THTs as measured have both boundary loading and cabin gain, his result is not even close to that in half space, so it can't be even remotely compared to the same number of T36s in half space anechoic.

[Bill Fitzmaurice]

They were in an open garage door facing outdoors, not sure how that would impact the gains from boundary loading and cabin gain, but it was definitely not a standard or optimal setup.

The pic above was last spring when I went over them, I think Tristan nailed a pic of what we were doing... I'll see if I can grab it and throw it up here.

For a half-space result measure in an open field at least 200 feet from any buildings.

[la malta]

If this still has any bearing:

I believe that was Wi getting out his ray-gun to some DnB.

"It would take at least 16 T36s in half space to flatten the response all the way down. With boundary loading, less. With boundary loading and V coupling, less still. Add in cabin gain, again less. Wi's THTs as measured have both boundary loading and cabin gain, his result is not even close to that in half space, so it can't be even remotely compared to the same number of T36s in half space anechoic."

Where I'm confused I guess, is that I'm under the impression placing 2 cabs side by side next to each other is pretty much the same as having one speaker with the same mouth size and driver count. I'm pretty sure I've read somebody mention that before, be they incorrect. Is this true? Because when I look at the SPL chart for the 36" wide two 15" loaded T36 and see the response get louder to lower registers, I figure that makes sense under that principle, but then the chart of 2 individual T36s together does not share a similar response.

Generally a moot point as I don't want to try and fit anything larger than 24" through my doorways, but I'd like to know for the sake of knowledge.

[la malta]

Does anybody have an answer to my question? Still not sure about this 2 smaller cabs vs 1 big cab the same size = same response issue.

[jcmbowman]

Where I'm confused I guess, is that I'm under the impression placing 2 cabs side by side next to each other is pretty much the same as having one speaker with the same mouth size and driver count. I'm pretty sure I've read somebody mention that before, be they incorrect. Is this true? Because when I look at the SPL chart for the 36" wide two 15" loaded T36 and see the response get louder to lower registers, I figure that makes sense under that principle, but then the chart of 2 individual T36s together does not share a similar response.

Generally a moot point as I don't want to try and fit anything larger than 24" through my doorways, but I'd like to know for the sake of knowledge.

A pair of 18" T36s with a single 3015LF in each would generate the same output as a single 36" T36 with double 3015LFs in it.

I think the confusion on the SPL chart for the dual-15 T36 is that that is just a theoretical plot - Bill even said on that page that he wasn't about to build one just to measure it.

[la malta]

Fair enough. Thanks!