Recommend for pair of 12" sealed passive subwoofers

[voodooless]

HO is high output, HF is high frequency. The HO has a heavier cone and coil, giving more power handling and a bit lower extension. The HF will play a bit higher in frequency, and do that a bit more efficiently.

 

[Wolf]

I'm hoping they don't discontinue the Ultimax, but the RSS-HE seem like they will replace them. FWIW, they handle more power with the 3" coil, and actually work in about the same volumes as the Ultimax do. For example, the RSS-HE265 will work in the Overdrive10 configuration, and do it quite well. It's just that they are a LOT more money too.

The first time I heard the RSS315HF I thought it was amazingly clean and transparent. The Ultimax can get louder and work in smaller boxes, but the RSS are cleaner monsters.

 

[Andrej]

I have built multiple subs with 10" Ultimax and also with 12" RSS with dual 4+4 coils, and both are good. Hard to compare exactly as the sub designs were significantly different, but the 12" in 3 ft3 matrix enclosure tuned at 20 Hz and the response adjusted within a digital crossover were my preferred choice.
Between the 12" UM and 15" RSS, I would definitely pick the 15" one, with the caveat of how big a box one can one handle. Same when it comes to the choice between HO and HF - big box = HF, small box (higher forces thus the need for a sturdier driver) = HO.
I would always build a vented sub, with low tuning. To me the choice is clear when you compare performance graphs for the BMS 18" driver on data-bass.com. With in-room equalization, otherwise it is a random guess without prior experience with that listening space.

Data-Bass: Subwoofer Measurements

data-bass.com

vs.

Data-Bass: Subwoofer Measurements

data-bass.com

 

[Davide]

According to my simulation, with SPL the RS 15 inch is better than the Ultimax 12 inch in the same cabinet (slightly).
Distortion cannot be simulated though...

 

[Jdunk54nl]

According to my simulation, with SPL the RS 15 inch is better than the Ultimax 12 inch in the same cabinet (slightly).
Distortion cannot be simulated though...

You can slightly investigate this with how close they are to Xmax under that same power. Usually, the closer something is to xmax, the more distortion it will have.

 

[voodooless]

You can slightly investigate this with how close they are to Xmax under that same power. Usually, the closer something is to xmax, the more distortion it will have.

That is if power is actually the only factor. The bigger woofer will always have less excursion than the smaller one at the same SPL (in the same box).

 

[Jdunk54nl]

That is if power is actually the only factor. The bigger woofer will always have less excursion than the smaller one at the same SPL (in the same box).

Right, that is why I said you can slightly investigate. With most simulation software that us mere humans have, there aren't great ways to simulate this, at least that I know of with winisd or the likes.

 

[voodooless]

Right, that is why I said you can slightly investigate. With most simulation software that us mere humans have, there aren't great ways to simulate this, at least that I know of with winisd or the likes.

Well, you basically can't because the data to do this is missing . In general, the differences from product to product are so large that there really is no telling which one has the best distortion within the physical limits of the woofers.

 

[Jdunk54nl]

Well, you basically can't because the data to do this is missing . In general, the differences from product to product are so large that there really is no telling which one has the best distortion within the physical limits of the woofers.

So, if I look at two drivers and look at how the cone excursion compares to the xmax of that driver (some smaller drivers have bigger xmax's compared to larger drivers) under the same power, the one that is farther from xmax usually has lower distortion, we can see this in a bunch of the distortion graphs as you increase the power being applied, the one that is starting to "tap out/run out of gas/etc" is also the one increasing the distortion the most.

Like the rs 15 ho has 12mm xmax, HF has 14mm
The Ultimax 12 has 19mm of xmax.

If we say put 500w to each of these, If the HF was at 12mm excursion (86%), the HO was at 9mm (75%), and the ultimax 12 was at 15mm (78%), I would bet that the HO would have less distortion than the ultimax and the HF. But the ultimax and the HO would be very close and more tests would be needed to truly figure out which is better. The HF would, in my opinion and looking at past data of woofers running out of gas, would have the most distortion. It has always been my experience that as a driver gets pushed closer to its limits, the distortion it produces increases. There drivers and systems that handle this better than others, but even the purifi woofer increases it's distortion as it gets closer to its limits, just much better at handling this and reducing distortion as much as possible.

Granted I did not put any of this into winisd and would need to in order to figure out the true excursions under that power and see. You would also need to take into account spl in the simulation to see if that is greatly impacted by the size of the cone and the excursion it is using. If the ultimax 12 is at a lot lower SPL compared to the HO 15, I would 100% go with the HO 15 in that case. But I would be more leaning towards the ultimax 15 with 19mm excursion compared to the HF or HO.

 

[Davide]

I found this on Audioholics which seems interesting to me: Link

I understand that a low Qts and Fs driver in a sealed cabinet with Qtc of 0.707 is preferable in order to make it work in acoustic suspension, and therefore benefit from a lower distortion due to the greater linearity of damping of the internal air, as well as a gentler rolloff downward in the frequencies.
This would favor the Dayton HO 15".
But Dayton recommends for this driver (for 0.707 Qtc I suppose) a cabinet of 1.58 cuft that gives 50hz F3......
It doesn't seem like the best fr...
Scandinavian and German drivers seem to suit best these characteristics... I have to simulate with one of them...

Edit: On the web I find written more or less everywhere that low Qts are suitable for ported and high Qts for sealed. Contrary to what I understood from the article.
Am I doing something wrong?

 

[Davide]

I also found this other article particularly comprehensive: Link

Choosing a low Qts and Fs driver paired with a cabinet with an overall Qtc of about 0.7 and volume equal to 1/3 Vas, seems the best solution for SQ and design simplicity.

So Scan Speak's 30W/4558T00 driver appear to be the best option.
Among other things, Scan Speak already provides a suggestion on the volume of the cabinet for a Qtc of 0.707 through their excel calculator (67 liters with F3 of 34hz).

What remains for me to understand is how to calculate the stuffing material in order to target an equivalent cabinet value of 67 liters (due to Q influence).
Can anyone help me with this last thing?

 

[manisandher]

Wasn't sure where to put this, and thought this thread might be appropriate...

I've just received 4x passive subs built by KJF Audio, who are local to me here in the UK:



The specs for each sub are as follows:

- 91L sealed enclosure
- 1x 12" SB driver (19Hz fs)
- no crossovers
- low-passed 36dB/octave @ 80Hz using DSP
- 25mm MDF
- beautiful built and veneer finished
- 37Kg

Here's how they look alongside my speakers:



They work exactly as I had hoped. The mid-horn is band-passed 80Hz to 500Hz, relieving it of doing any heavy lifting low down, resulting in a nice uptake in mid-bass performance (to my ears at least - not taken any extensive measurements yet).

A massive shout out to Stefan @KJF audio. Top man. Absolute pleasure to do business with. (He also builds great Hypex-based amps .)

Feel free to ask any questions should you have any.

Mani.

 

[Jukka]

Whatever you build/buy, remember two things:
1) most drivers are tuned for vented box, so pay attention datasheets and simulators or go with a kit.
2) MiniDSP SHD. It has 4 outputs, so you can crossover, time-align and fine tune to your hearts content. I use it and brag to my friends that each driver has a dedicated amplifier and one or more dedicated dsp channels.

 

[manisandher]

Whatever you build/buy, remember two things:
1) most drivers are tuned for vented box, so pay attention datasheets and simulators or go with a kit.
2) MiniDSP SHD. It has 4 outputs, so you can crossover, time-align and fine tune to your hearts content. I use it and brag to my friends that each driver has a dedicated amplifier and one or more dedicated dsp channels.

Agree. Stefan at KJF Audio has a degree in Sound Engineering - he knows what he's doing .

My approach to crossovers is outlined here: https://audiosciencereview.com/foru...ctive-crossover-using-roon.29882/post-1046848

Mani.