Single sheet TH challenge

[Don Snyder]

Originally Posted by hellonwheels

Screamer was using a little hyperbole to say that his DIY TH-15 would introduce unheard of level of fidelity to a "pro guy" used to direct radiators. I gave an example of pro woofers that are more far more linear and more extended. (granted they are more SD, displacement and power handling)


I fail to see what relevance a Lab sub stack has to do with a different alignment, used singly or pairs. You know as well as I TD has claimed that large stacks of FLH will trump TH for efficiency.

You said that the ports were big enough that (your choice) vented boxes had no port linearity issues. Both Danley and Cowan have said otherwise.
If you make ports large enough, they get long enough to have organ effect problems. TH have no port problems.

The reference to LabSub's was to bring up Danley's comments that ports are the problem with dual 18's.

Tom's quote was that once your stack of THs have a full horn mouth, they have no advantage over a FLH. By the way, a full horn mouth for a LabSub
in 4Pi is 16 units. In 2Pi, a stack of 4 TH118's will trump 4 LabHorns!

[hellonwheels]

Originally Posted by Don Snyder

You said that the ports were big enough that (your choice) vented boxes had no port linearity issues. Both Danley and Cowan have said otherwise.
If you make ports large enough, they get long enough to have organ effect problems. TH have no port problems.

The reference to LabSub's was to bring up Danley's comments that ports are the problem with dual 18's.

It's physics not opinion, the speed of sound doesn't change. If the port airspeed is low enough at the required SPL you don't get nonlinearities more than what is normally there at lower levels.

If you check bigger boxes 300L or more there's no problem tuning to 28Hz-40Hz and large ports, and surely you realize that TH also have resonances above the passband. I would think this would be somewhat elementary.

Otoh, attached is a quote from cowan who seems to have "discovered" a hole in the inverse square law. Extraordinary claims require extraordinary proof. Danley is making no such claims.

Danley here accidentally (I believe) substituted a single 12" port where as Iand modeled 2x10" ports which is much more reasonable for a high SPL design. Simply look at the peavey qw218 or this 2x15" with what looks to be at least 4 times the single 12" port danley modeled.

to see that commercial manufacturers do pay attention to port compression.

My point isn't that TH isn't a great alignment for some purposes, but there's hyperbole saying that is low distortion, extended LF, and high SPL cant be found with a vented alignment. Or that I a "pro guy" have been missing out because Screamer's TH alignment is so much better than I have heard. I will stop participating further discussion of this without actual quotes from TD, measurements or at least models because there's no point to me. At some point its like arguing speaker wire.

Originally Posted by cowanaudio

We have all been looking in the wrong place for the Tapped Horns hidden advantage.

This came to me while lying in bed at 2:00 this morning (as I am often inclined to do when faced with a challenge).

A loudspeaker radiating into half space has an output that decreases at -6dB with every doubling of distance. With a vented box, the origin is the driver or the port, depending on the freq the box is being driven at. Now a front loaded horn does the same thing, but the origin is still the driver, not the mouth of the horn. That means if you took a measurement at 10M out from a 4M long horn and compared it with a measurement 10M out from a vented box, the results would be very different, even if the horn output matched the VB output at 1M. I've measured this effect with front loaded horns and would have to assume it holds in a tapped horn. Tom measures his speakers at 10M for a VERY GOOD REASON. He could argue, and I'd have to agree, it more closely matches real life use. It accounts for the excellent output and efficiency seen in all the tapped horns that have been discussed here.

Ian, you are right in that a Tapped Horn has no advantage at one meter from the mouth when compared to a well designed vented box. As the distance increases, the advantage increases.

The plot thickens.

Cheers

William Cowan

Tom Danley>>>>>
Hi Iand,
when I model a pair of the 18ps76’s in a vented box, what I see is a sensitivity between 101 and 102dB 1W1M, about –3dB down from the TH-115.
Also, with that alignment one reaches Xmax in the 65Hz to 35Hz region at about 350 Watts total input and even a 12 inch port has noticeable loss.
So far as Tapped horn excursion, I believe the issue arose from Akabak giving a different predicted value from Horn response at the time, I don’t know if they agree now or not.
I can tell you is that if you want to know what the excursion is, the easiest way to do it is to put a window in the box with a light inside and a white dot on the cone next to a scale.
My point then was that if one sees an increase in sensitivity of say 10dB, one also sees a reduction in cone motion of about 3 for the same SPL.
Also, it has been my observation that often the “Q’s” of the hf resonances are over stated in the computer models, some times a hf feature is predicted that is totally absent in the measurement.
“P.P.S. Also a large array of tapped horns may indeed gain more in efficiency, but this is only relevant in big concert sound systems”
I would agree in part, clearly I have seen that the advantage one can get from a TH is related to being “big enough”.
The TH allows the Horn portion to be somewhat smaller than a normal horn but it still has to be large enough.

[jbell]

hellonwheels:

Littlemike has said many times that moving from pixel pushing to sawdust making... makes a lot of difference. It's kinda like 2 old farmers arguing about how many teeth a horse has. The argument ends when one of them opens up the horses mouth and looks.

I submit to you to buy a 3015lf, build 2 like sized cabinets, one ported, one tapped horn. (My ss15 cabinet is a good size to compare to a ported for example.) Go outside, turn them up to a reasonable volume (like 28 volts) move back 100 meters and listen... Take a hand held spl meter if you don't trust your ears.

At that point, you'll know how many teeth a horse has.

[Chaps]

Hi JBell ..

I'm new here, but i think your design is very interresting as I am about to build som sub-boxes for myself in the same league .. I don't know is this is the right place to ask, but here it goes

I have seen you mentioning a earlier design of yours referred to as the "cube". Is this a similar design to CUBO15/18 and Beyma SB18? .. If it is, can you then tell me about the advantages of your new design compared to the "Cubes"? .. I'm not that much into speaker theory, so i have a little hard time figuring out, if this new design will match the Cubes SPL-wise, when it's driver (3015LF) is rated under half the power of the drivers recommended for the other designs .. Of course i know that it has something to do with the sensitivity differences, but is it that much? Will this new design really go as loud, but with that less power? - Thanks very much in advance!

[jbell]

Originally Posted by Chaps

Hi JBell ..

I'm new here, but i think your design is very interresting as I am about to build som sub-boxes for myself in the same league .. I don't know is this is the right place to ask, but here it goes

I have seen you mentioning a earlier design of yours referred to as the "cube". Is this a similar design to CUBO15/18 and Beyma SB18? .. If it is, can you then tell me about the advantages of your new design compared to the "Cubes"? .. I'm not that much into speaker theory, so i have a little hard time figuring out, if this new design will match the Cubes SPL-wise, when it's driver (3015LF) is rated under half the power of the drivers recommended for the other designs .. Of course i know that it has something to do with the sensitivity differences, but is it that much? Will this new design really go as loud, but with that less power? - Thanks very much in advance!

Hey chaps, welcome.
Here's a link to the 'cube' http://www.diyaudio.com/forums/subwo...ml#post2242426 that I designed. From about 60-100hz, the single sheet design is about 5db louder at 1watt. Well that doesn't sound like much, right? well here's my take on sensitivity and power handling. ALL speakers suffer from power compression. When you put a bunch of power into a sub, the coil heats up, resistance goes up, and spl goes down.... where and when that all happens depends on a bunch of factors, but it happens. What this means to me is that a 5000 watt rated sub is usually not a good deal... You may get LESS output at 5000 watts verses 1000 watts. So, if having a sub that is rated in the kilowatts doesn't 'really' get you more output, efficiency is the only other place to get it. That's why every db in efficiency is priceless.

The other factor in play here is that a tapped horn has a polar (directional) pattern. If you are outdoors -- you are not wasting bass on the birds and the bugs -- and more bass reaches your audience. That is also priceless.

Here's also a few quick numbers to keep in mind.

It takes (not counting power compression) to get from 1 watt output:
100 watts to increase 20db
1000 watts to increase 30db

You lose in distance:
20db in the first 10meters
30db in the first 100meters.

Doubling cabinets and doubling power nets you about 6db. (3db for each)
The ear hears about 10db as 'double' volume.

Horns are different than bass reflex cabinets. When you stack horns together, they play lower, and they get more efficient. (up to a point)

Hope this is helpful.

[tb46]

You have a type in your SPL v. Distance:

20dB for every decade (20 for 10m / 40 for 100m),
or
dB = SPL - (20*log10 (D2/D1)).

Regards,

[Chaps]

Thanks a lot!
That definitely helped my understanding of sensitivity, and how much a few dB's means ..
Am i correct if that means, that if i have 2 boxes, one rated at 100dB and the other rated 103dB, it will take twice the power to get the first box as loud as the other?

Do you have any thoughts on the Cubo and SB18 design vs. your single sheet tapped horn? I would really like the loudest box i can get in that size (of course sound quality is importent too, but i think that all of these boxes can deliver good quality sound), but there is just sooo many designs out there that meets my needs for size an freq respsone, and i think it is hard to compare them, when have haven't ever listened too them or is able to simulate them .. So, you gotta ask the pro people

[jbell]

Originally Posted by Chaps

Thanks a lot!
That definitely helped my understanding of sensitivity, and how much a few dB's means ..
Am i correct if that means, that if i have 2 boxes, one rated at 100dB and the other rated 103dB, it will take twice the power to get the first box as loud as the other?

Do you have any thoughts on the Cubo and SB18 design vs. your single sheet tapped horn? I would really like the loudest box i can get in that size (of course sound quality is importent too, but i think that all of these boxes can deliver good quality sound), but there is just sooo many designs out there that meets my needs for size an freq respsone, and i think it is hard to compare them, when have haven't ever listened too them or is able to simulate them .. So, you gotta ask the pro people

Thanks for correcting my typo oliver -- I should have proof read that post better.

Chaps:
On your question about a 100 vs a 103 box -- you are right on the money. Now put that in terms of 500 watts vs 1000 watts, and you can see where a 103 box shines. AND, with power compression, the 100db box @1000 watts, is not even keeping up with the 103box @500.

Here's one of my all time favorite measurements..... Look at the 40hz area..... ProSpeakers Forum - Fitzmaurice Titan 48 - Wayne Parham, October 21, 2007 at 14:31:26
and then compare 100watts vs 800 watts...

On the cubo, it's in the grey area between bandpass, ported, tapped, etc... It's a hybrid that really doesn't fit a description very well. I know the hornresp models don't line up exactly with the designers spl charts, but then I haven't built one and measured, so I can't comment otherwise.

[djk]

"Look at the 40hz area"

No increase in output from 400W to 800W, but the distortion goes up at least 6dB.

[Chaps]

Originally Posted by jbell

Thanks for correcting my typo oliver -- I should have proof read that post better.

Chaps:
On your question about a 100 vs a 103 box -- you are right on the money. Now put that in terms of 500 watts vs 1000 watts, and you can see where a 103 box shines. AND, with power compression, the 100db box @1000 watts, is not even keeping up with the 103box @500.

Here's one of my all time favorite measurements..... Look at the 40hz area..... ProSpeakers Forum - Fitzmaurice Titan 48 - Wayne Parham, October 21, 2007 at 14:31:26
and then compare 100watts vs 800 watts...

On the cubo, it's in the grey area between bandpass, ported, tapped, etc... It's a hybrid that really doesn't fit a description very well. I know the hornresp models don't line up exactly with the designers spl charts, but then I haven't built one and measured, so I can't comment otherwise.

Wow, those numbers really put things in perspective!
Now i got to ask, in the SS15, what will be the SPL "limiter"? Will it be power to the driver, XMAX or something else to concider? I think i have read somewhere that PE was a factor in this, but i don't know what that is?