radulescu_paul_mircea

I will soon build two TH118 ,identical enclosures to the original, which I will build only for tests to compare them to the Xoc1 design using both the original drivers, 18 ID and 18 Ipal and also to some other designs with other drivers

Some real life tests between 2 Xoc1 TH18 vs 2 L-acoustics SB28 on a clone and on an LA8 amp.measurements,opinions and discussion can be found in the comments

https://www.facebook.com/groups/733449990043427/permalink/1471064019615350/

http://www.audioxpress.com/article/test-bench-b-c-speakers-21ds115-21-inch-woofer

Bench test review. The factory can provide also their own LSI Klippel results that can be compared to these ones and adding that to the tests Ricci did, I can say this is a very interesting driver at a very good price IMO.

That APO EQ brigs some serious distortions and it has some glitches. I used it for a while but when I turned it off, I realized how bad it changes the sound

The 4 ohm version can be seen on bcspeakers.com. when you select the driver, you have to click on the 8 ohm or 4 ohm icon right beneath the picture.

You are right about the average power. I was referring at that power into both.I didn't get that number from somewhere specific, all I did was to take the TruPower limiter setting for my BC18SW 115 in my Xoc 1 TH18 subs and double them. Off course, my gain strategy is to engage those limiters only on occasions when needed not to keep them engaged constantly.so the average power these get is a bit over half of that.

Regarding the content, I was speaking from experience, when in a comparison of my 2 TH18 vs 2  BR with dual 18TBX100 tuned to 36 Hz, those 2 were louder than mine on average because even though the max clean SPL  was the same on paper and on measurements, on tehno music, long term the 2 were taking more voltage with less heat, so the limiters were not engaging on them.

The kind of music I was referring to was techno,dance, minimal etc.. that music is much more focused in that passband but it doesnt mean there is no content outside of it.

Bigger, for sure!!

Now let's think why. the main thing with this is from the fact that putting a horn in front of the speaker, the general sensitivity in the pass band will be increased, and also the efficiency. 

Grey Bass Reflex 522 L, Black SKHorn 522 L, SPL at 145 V,  same tuning frequency

Efficency

The main issue appears when using more than one and using a specific type of music material. Techno music is most of the time centered around 45-80 hz .there is right where this sub has its impedance minimum. If it is to be chosen between this SKHorn and 2 dual 21DS115-8 in very small enclosures, like 310 litters net each, with similarly big ports as the SKHorn, those would be better equipped to withstand a whole night of using them to their limit. Why? because of the content type.

Most of the energy being centered in that band, the RMS limiters for an SKHorn would engage to keep the average thermal power into the sub at under 2-2.2 Kw (which IMO is very  risky, given the fact that the excursion is lower exactly where the power input is higher so the cooling is poorer) so even though the peak SPL capability of this sub would be within 2 dB of that couple, in use, those 2 would be much louder than this one because the RMS limiters would not engage if set to the same threshold. also the power compression would be higher on the SKHorn, and extremely low on the 2 dual BR because most of the time the drivers in the BR would see under 1 KW in the 40-75 HZ range and in that range more power will leave the voice coil firstly because the excursion would be higher, so better cooling and secondly the power conversion efficiency would be higher so more energy would be converted into sound instead of heat.

In Grey is 2 dual 21 BCDS115-8 310 L net BR Efficiency

In Grey is 2 dual BCDS115-8 310 L net BR input power 145V on 2 series Ipal, 160 V 2 drivers paralel, 2 subs parallel

In Grey is 2 dual BCDS115-8 310 L net BR Max SPL 145V on series Ipal, 160V on 2 drivers paralel, 2 subs parallel

So yes, the two would be heavier, a bit larger, more expensive to make, but would require far less power from the wall and will give more long term output than a single SKHorn. So for people who would carry these around from a gig to another, using them mostly on EDM and Techno, it would be a better solution. it wouldnt sound as clean as the horn, having the driver in front. and also it wouldn't be anything spectacular, but it would be useful for this sort of app which is the most commonly used

So here comes the conclusion. Making it bigger would also make it more efficient. increasing the horn side would gain efficiency higher in frequency, increasing the back chamber and/or increasing the tuning frequency a bit  would gain efficiency in the lower parts. 

Off course, making a sub tuned exactly for that genre would be even better, like a Danley DBH 218 horn which keeps the efficiency very high but also it keeps the excursion low for a clean sound, but high enough from the high pass crossover to help the drivers cool down.

The DBH218 sounds very nice, but it's more of a 40 hz horn. This year at Pro Light and Sound they had 4 of them with a J3-96 each side of a stage but I wasn't there so IDK how they sounded. Last year they had 2 BC218 with 4 DBH at the ends of the stage with 2 SH96HO. Those BC are crushing but these M-Force horns are over them

So I heard these for the first time.

They are more than wonderful. That system goes down to 27hz clean and immensely powerful.they are so loud I was shocked. I heard the Danley BC218 last year but these are in another league. The cabinets are rock solid, even the back wheels inspire quality. The amp is clamped on in the back but they didn't make a personalized case for it

To be honest, I checked this thread 3-4 times a day waiting for results. And when you published them, it was better than expected. Cool

They have opened it . I've seen a pic last year but now it's clear

Edit: in fact that is their new bass reflex m force sub

Cool!! Finally

Let's see the results now !

I know how time consuming these things are and the work they involve so you are a special guy for sharing these with us.

Thank you and I will wait patiently :-D

So,how's the weather? :-D

I think Dominican Republic

If one ever wondered how stupid loud would 12 21" Ipal be in a relative small bandpass enclosures tuned to 50 HZ

https://www.youtube.com/watch?v=k4ncqcAv0fE#t=1.877333

)

Related to the Ipal Technology, I found a test with the 18 ID driver

http://www.audioxpress.com/article/test-bench-eighteen-sound-18id-18-inch-woofer

Cool. How does it behave at high excursions?

ONCE those start showing up at all the major B&C vendors I wouldn't be surprised to see street prices below $500. Perhaps well below.

:-D more or LESS

I really have to know what those drivers are made of, cause I can get them at a hell of a good price but there has to be somewhere it doesn't perform as well as the 152. I can't wait to see what this sub is capable of also.

As it turns out Ricci, the fact that the joint point of the driver is too small and the long term pressures and acceleration are to high for the diaphragm materials, they keep braking in use because the producers are not developing their own specific membrane to suit their application.

I have this information from a sure source now so this is not only a speculation anymore.

This sounds better than Netflix ) can't wait, man. I would also like to see 21ID and 18Ipal tested and some subs like the Funktion F132 . Also ,as daydreaming material, if Rockford could build a 24 T3...:-D

And also if you have the will and money , a M-Drive module used for this sub if one is using the Ipal drivers

That would be a killer. Probably in the same range as K-Array KS8 ( which costs 10000$ :-0) I think even better as that one is using the 21ID and Ipal MOD

Looks like it's probably a 4th order bandpass with a bit of shaping and flaring to the front vent unless there's entry from a secondary somewhere into the mouth behind that grill.

 

Interesting that there were reports of subs having thermal protection issues. Those drivers are seriously low impedance. The average is much higher than normal due to the extremely large impedance peak but near the minimums like in a vented cab it will still be very low and that has to be difficult for an amp to dump current into a 0.5 ohm load especially if the content has a repeating note near a minimum.

The input is this.

Then with the added eq one will get this

Could be better go sure

Taking to account the eq and crossover the port velocity would be up to 70m/s and the front velocity would be at around 30 m/s at 25 mm excursion. It would be very chilly

Yes , I like it a lot. The driver is backwards and stuck to the grill to increase cooling.I simmed it and it can get 142 dB în HR from 31 hz with only band pass filter and 3 PEQ entered.Quite easy to set it. port particle velocity at 50 m/s so not bad.at the mouth it will go to about 28 m/s and that will act as an efficient cooling method. The efficiency is very high, more than 12% from 33 hz up in singles