diyAudio

diyAudio (https://www.diyaudio.com/forums/index.php)
-   Subwoofers (https://www.diyaudio.com/forums/subwoofers/)
-   -   Keystone Sub Using 18, 15, & 12 Inch Speakers (https://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers.html)

Scientific 6th May 2015 04:10 AM

The DSL spec for the TH118 speaks of sensitivity as being 108 dbspl at 1m. If that means 2.83 volts into a 4 ohm load, then I can assume the SPL is still 105 dbspl for 8 ohms. Still great considering the useful lows down to 35hz. 105 db for 1 watt (assuming little compression) might give 138 db for 2000 watts. I notice the website says 137 dbspl max or 143dbspl peak. (The Cerwin Vega TS42 also quotes max SPL of 144 db.)
Does the Keystone give the same average levels of SPL? I am reading that the keystone reaches 130 db. If I add 3 db for max I still only get 133 db.spl. Well these might just be numbers on paper or am I missing something? What do the measured and subjective tests show? Thanks in advance for clarifying.

http://www.danleysoundlabs.com/danle...spec-sheet.jpg

zettairyouiki 6th May 2015 06:54 AM

Quote:

The DSL spec for the TH118 speaks of sensitivity as being 108 dbspl at 1m. If that means 2.83 volts into a 4 ohm load, then I can assume the SPL is still 105 dbspl for 8 ohms.
As far as I know, that spec (105db/1W nominal) is still considered questionable by a lot of people. Far more sensitive than both the keystone and TH18 have been measured as, both of which are very similar.

NEO Dan 6th May 2015 07:13 AM

The time/resolution info at the top of the graph on the data sheet lead me to believe the measurement is actually pretty far from anechoic, but then again I'm not a TEF user.

djk 6th May 2015 08:05 AM

So it's clearly 102dB/2V/1M at 40hz.

sine143 6th May 2015 03:08 PM

Quote:

Originally Posted by NEO Dan (https://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers-post4317028.html#post4317028)
The time/resolution info at the top of the graph on the data sheet lead me to believe the measurement is actually pretty far from anechoic, but then again I'm not a TEF user.

Its definitely NOT anechoic, however it is optimized for the highest frequency resolution. assuming they were 400 feet or so from boundaries, it should be an accurate 2 pi chart, and givin how fine the freq resolution is, we would be able to clearly see any reflections represented in the chart.

NEO Dan 6th May 2015 03:19 PM

IIRC Ivan took the measurement for the TH118 at DSL and they do not have a very big lot.

sine143 6th May 2015 04:15 PM

I only say 400 feet (should have said 459 ft) because that is the distance at which the TEF was configured to "reject reflections" from (can see it on the chart). with a freq resolution of 2, any notches should be clearly evident (granted they have 18 percent smoothing enabled as well).

the only thing I suspect (IF there is anything wrong with the graph, which I honestly dont believe) is improper mic calibration (resulting in a "too high" sensitivity reading).

I just got a TEF 25 last week though, so dont take my word on it... stilllllll learning how to implement it correctly.

weltersys 6th May 2015 06:47 PM

Quote:

Originally Posted by Scientific (https://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers-post4316947.html#post4316947)
The DSL spec for the TH118 speaks of sensitivity as being 108 dbspl at 1m. If that means 2.83 volts into a 4 ohm load, then I can assume the SPL is still 105 dbspl for 8 ohms. Still great considering the useful lows down to 35hz. 105 db for 1 watt (assuming little compression) might give 138 db for 2000 watts. I notice the website says 137 dbspl max or 143dbspl peak. (The Cerwin Vega TS42 also quotes max SPL of 144 db.)
1)Does the Keystone give the same average levels of SPL?
2)I am reading that the keystone reaches 130 db. If I add 3 db for max I still only get 133 db.spl. Well these might just be numbers on paper or am I missing something?
3)What do the measured and subjective tests show? Thanks in advance for clarifying.

1) Probably quite similar, if measured the same.
2) Peak response in calculated manufacturer's specs don't consider Xmax, the 130 dB I quoted is at Xmax.
3)Measured response with a "normal" SPL meter verify that the Keystone can do around 130 dB in the LF.
PASC used the same 18 Sound driver in an Xoc TH18 (same size and similar fold to the DSL TH-118) and the Keystone and found the Keystone to be slightly louder and cleaner.

Here is a comparison of a DSL TH118 to an EAW SB1000z:
https://soundforums.net/threads/6793-TH118vsSB1000z

My observations are in post #8.

David Gunness, former designer at EV and EAW, now with Fulcrum Acoustics has explanations of the specs "game" in post #18 on 4/10/14:

https://soundforums.net/threads/9905...or-Stick-mains

"OK, here we go. Once more into the breach. The reason I hate this is that in the process of explaining how our industry does specs, it appears that I am justifying practices that I actually don't agree with.

One of the reasons I don't like peak SPL specs is that "SPL", at least in textbooks, is defined as the RMS sound pressure (referenced to 2x10-5 pascals). So theoretically, there is no such thing as "peak SPL". OK, maybe that's too pedantic: we could interpret it as "peak sound pressure, expressed in units of SPL". Let's go with that.

The point is that "Peak SPL" as it is treated in the professional loudspeaker industry, is peak pressure, not "highest reading of an SPL meter" (SPL meters only measure RMS; even if there is a peak hold function, it is the "highest rms reading observed", and that includes the selected averaging time). Anyway, peak pressure is calculated using the peak voltage of the amplifier. With non-powered systems, the assumption is that a user will supply an amplifier with twice the power rating of the loudspeaker, and that the peak voltage of the amplifier is 3 dB higher than that, because amplifiers are rated with sine waves. Hence, the peak pressure should be 6 dB higher than the maximum continuous SPL.

Keep in mind that maximum continuous SPL is a survival rating, not a useability rating. Of course what would be more useful is "maximum useable SPL", but that would be signal dependent and would have to be subjectively determined. So we're stuck with a calculated value that serves only as a point of comparison: "This one's red line is 2 dB higher than this one's red line."

As for the TS215ac, here is the math (with one more significant figure than the whole numbers on the spec sheet):
Equalized Sensitivity: 99.2 dB
Maximum Peak Voltage of the Amplifiers: 150 V
"Peak Power" into 2 ohms (actually two channels driving 4 ohms each): 11,250 W
Peak Power, expressed in decibels: 40.5 dB
99.2 dB + 40.5 dB = 139.7 dB, which rounds to 140 dB"



Back to subjective/measured response, prior to building the Keystones, I got a chance to compare four of my small ported dual twelve cabinets using Lab 12 speakers to eight dual 18 Meyers 650P cabinets.

On a two stage side by side outdoor show I got a chance to compare four of my small ported dual twelve cabinets using Lab 12 speakers to eight dual 18 Meyers 650P cabinets, measurements done on a RTA at the same point equidistant from both sub set ups.

The four 22.5 x 22.5 x 26.5 dual Lab 12” (fB 36 Hz) driven by a pair of Crest CA-9 amplifiers put out 4 dB less at 60 Hz, but 2 dB more at 40 Hz than the eight 650P, using a small fraction of the power, the whole PA was run off two 20 Amp 120 volt circuits. Those four cabinets equal the size of a pair of Keystones.

8)12” cones, 3600 watts, 31 cubic feet of truck space, 400 LBS.
Compared to the eight Meyers 650P :
16) 18” cones, 9920 watts ”burst capability”,140 cubic feet of truck space, 1768 LBS.

A pair of Keystones using the 18SW115-4 driven with the same amplification are louder than the four dual Lab 12, which were louder at 40 Hz than the Meyers 650P, and the Keystones are several dB louder at 60-100 Hz than the four dual Lab 12.

At any rate, if you look at the Meyers 650P specs, you can see a large disparity between "paper" and subjective/objective reality.

Art

djlivex 11th May 2015 06:02 PM

I have looked at the plans seems a simple build I have built subs before (BFM T24s, Cubo Sub 18) and have 2 sheets of 4X8 BB 13 ply I have a PD 184 new in the box shipped to me 2008, can I use this driver low Qts, will use this for low power sub Djing 100-250 capacity venue weddings indoors so no real high volume needed here. https://www.solen.ca/documents/pdf/p...ices/PD184.pdf
Big thanks!

weltersys 11th May 2015 07:37 PM

Quote:

Originally Posted by djlivex (https://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers-post4322735.html#post4322735)
I have a PD 184 new in the box shipped to me 2008, can I use this driver?

Any driver can be used in any box, you can use the Hornresp inputs from post 96 or 130 and enter in the PD 184 parameters to get an idea of the response, and if it will do what you want.

Response should not look too bad, but will have at best -6 dB less output than the BC18SW115.

Art


All times are GMT. The time now is 03:56 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio

Wiki