Added SKRAM ported horn subwoofers!

[Pieter1267]

So I finally pulled the trigger and received my first new custom build SKRAM subwoofer. Its a ported horn design cab for high output over a long range and versatil in setup with 4 adjustable ports to change the character from its original mid bass chest punch base to a more low extension for home theater purposes.

Ive really gotten convinced that higher crossover work best, even with big main floorstanding speakers. These SKRAMS measure flat way past 110hz and deliver up to 130hz up to 90% still.

Because im only using it for music i think im gonna keep full open ports or just one port blocked. The room gain is such that even with 1 port blocked i sometimes need to turn down the bass control on the pre amp a notch. It could also be that i have just one cab and with 2, the bloaty feeling might be more controlled. I also suspect it might be only with bad produced tracks.

That said already this one SKRAM is the best subwoofer ive ever had, and blows my previous 2 Dayton Ultimaxes out of the water. Its loaded with a B&C 21DS115-8 and gives my inuke 6000 a good workout. The mid bass is just awesome. At volume you feel and hear a big air mover at work, like an airplane taking off.

Ill post some measurements later. Some extended considerations on these SKRAM designs when i have number 2 and better comparisment.

Here are some pics. They are big yet not as big as keystone, th18 or gsg devastator. The smallest near PA level subwoofer with hifi quality delivery. Josh Ricci designs are fantastic.

They are still measuring 91x83x60cm and weigh about 90kg plus driver. Look next to my main speakers the F208 Revel. Not sure how to get them to @amirm if he would like to test them

 

[kemmler3D]

Now that's a sub! Do you have a link to measurements or anything? Curious what it can do in the bottom octave. My preferences tend toward extension over SPL, but both are good if you can get them...

 

[Pieter1267]

Now that's a sub! Do you have a link to measurements or anything? Curious what it can do in the bottom octave. My preferences tend toward extension over SPL, but both are good if you can get them...

Ill add some preliminary REW measuments later today. The on axis close measurements look great and MLP im very happy too.

I always thought you need to make a choice either great low extension or fantastic slam but this guy can do both. And because the driver is huge, even with all ports open in its base 28hz tune config, its low extension is massive. Massive! And its so controlled. It wasnt cheap and total spend on 2 is about €3000 (the birch plywood is a big big part) but itll eat any SVS alive for sure.


10cm in front on axis:

Isnt this a beauty?


sub+mains @ MLP, Fc 100/105 LR 24db all ports open:

Ditto, one port closed:

 

[Pieter1267]

At the moment having fun with different Fc. Linkwit-Riley or Buttersworth24db? At low volume the latter sounds better when all ports are open. Closing ports quickly becomes too much bloating on high volume and I really need a second SKRAM to see what is what.

Is that bump below 50hz I should flatten with DSP?

And this youtube set from techno God Rodhad: is it me it sounds too much bass? Lots of other music including other techno is fine but this and other Youtube sets Somehow dont sound right. I had the same on my former subs.

 

[ppataki]

At the moment having fun with different Fc. Linkwit-Riley or Buttersworth24db? At low volume the latter sounds better when all ports are open. Closing ports quickly becomes too much bloating on high volume and I really need a second SKRAM to see what is what.

Is that bump below 50hz I should flatten with DSP?

And this youtube set from techno God Rodhad: is it me it sounds too much bass? Lots of other music including other techno is fine but this and other Youtube sets Somehow dont sound right. I had the same on my former subs.

Yes, I would definitely correct that peak with DSP because currently that part dominates the bass region and it might sound as a 'one-note bass'
I would also fix the peak at 130Hz

If you use Dirac Live or equivalent it will take care of that automatically, otherwise you can use REW to generate correction filters

One other thing to try is to apply a low-shelf filter to elevate the SPL below 30Hz - your Inukes shall have no problem coping with that

For the crossover I would recommend using Linkwitz-Riley, 24dB/oct., symmetrical, since it will ensure flat phase summation at the crossover region

 

[tmuikku]

Nice. Most Hifi speakers are a joke, "real low end" that makes real emotional impact requires quite serious sized system.

 

[witwald]

So I finally pulled the trigger and received my first new custom build SKRAM subwoofer. Its a ported horn design cab for high output over a long range and versatil in setup with 4 adjustable ports to change the character from its original mid bass chest punch base to a more low extension for home theater purposes.

Would not a similarly large, 450-litre no less, vented-box enclosure produce similar, if not more, bass extension? These SKRAM so-called "subwoofer" enclosures are very big after all. However, the examples I've seen don't seem to do much below 40Hz, which really is not subwoofer territory.

Ive really gotten convinced that higher crossover work best, even with big main floorstanding speakers. These SKRAMS measure flat way past 110hz and deliver up to 130hz up to 90% still.

But won't most decent subwoofers achieve that if their design allows for it? 130Hz is not really all that high, not even being one octave above the "traditional" 80-Hz crossover frequency. In any case, doesn't the LFE channel in home theatre be able to contain frequencies up to around 120Hz or so, which requires that the subwoofer is capable of that sort of high frequency extension?

Because im only using it for music i think im gonna keep full open ports or just one port blocked. The room gain is such that even with 1 port blocked i sometimes need to turn down the bass control on the pre amp a notch.

Sounds like a sealed enclosure might be a better choice?

It could also be that i have just one cab and with 2, the bloaty feeling might be more controlled. I also suspect it might be only with bad produced tracks.

Does that imply that, high SPL capability notwithstanding, these types of low-frequency enclosures may not be an ideal choice after all? There seems to be a bit of contradiction happening amongst the subjective assessments.

That said already this one SKRAM is the best subwoofer ive ever had, and blows my previous 2 Dayton Ultimaxes out of the water. Its loaded with a B&C 21DS115-8 and gives my inuke 6000 a good workout. The mid bass is just awesome. At volume you feel and hear a big air mover at work, like an airplane taking off.

A 21-inch driver, especially one with high linear excursion capability, can be expected to achieve very high SPLs, and those will definitely be impressive in and of themselves.

Below is a simple 350-litre (effective volume) vented-box low-frequency subwoofer enclosure design based around the B&C 21DS115-8 21-inch woofer. This hits "real" subwoofer territory, and is a lot simpler to build.

 

[Pieter1267]

Would not a similarly large, 450-litre no less, vented-box enclosure produce similar, if not more, bass extension? These SKRAM so-called "subwoofer" enclosures are very big after all. However, the examples I've seen don't seem to do much below 40Hz, which really is not subwoofer territory.

But won't most decent subwoofers achieve that if their design allows for it? 130Hz is not really all that high, not even being one octave above the "traditional" 80-Hz crossover frequency. In any case, doesn't the LFE channel in home theatre be able to contain frequencies up to around 120Hz or so, which requires that the subwoofer is capable of that sort of high frequency extension?

Sounds like a sealed enclosure might be a better choice?

Does that imply that, high SPL capability notwithstanding, these types of low-frequency enclosures may not be an ideal choice after all? There seems to be a bit of contradiction happening amongst the subjective assessments.

A 21-inch driver, especially one with high linear excursion capability, can be expected to achieve very high SPLs, and those will definitely be impressive in and of themselves.

Below is a simple 350-litre (effective volume) vented-box low-frequency subwoofer enclosure design based around the B&C 21DS115-8 21-inch woofer. This hits "real" subwoofer territory, and is a lot simpler to build.

View attachment 469940

I disagree. The horn (though short) adds something fundamental to this SKRAM. When you put your head in front of the horn output you feel and hear its difference. If anything, i feel its port part is a bigger problem and needs precise care. And for a pure port design i wouldnt use the ds115 but the sw115. But if i ever change i would go back to a bms 850 sealed i think. Or try open baffle in my new house. But sofar these SKRAMs are here to stay. Smallest experience of a ported horn PA sub you can get.

Im an ex-DJ so used to trust my ears and what I need. This SKRAM fills all the holes in my very wide selection of music genres. I feel this is perhaps also misunderstood. Different genres need different solutions. I dont like the pure low extension of a ported sub and would add a kick bin later. The SKRAM tackles that both and does that well.

But thanks for the input! Ill post more experiences later. The more I use it the better i like it. Good at low spl and when i like some big bass pounding its there. And this is just the one! As far as power is concerned i dont think i need a second one but room modes yes i didnt think i would miss a 2 subwoofer so much.

 

[witwald]

And this youtube set from techno God Rodhad: is it me it sounds too much bass? Lots of other music including other techno is fine but this and other Youtube sets Somehow dont sound right. I had the same on my former subs.

@Pieter1267 Is there a specific point where you believe there is "too much bass"? I'm listening now, but it's a longish clip, so your guidance would be appreciated.

My initial analysis indicates that there is not much happening below 50Hz. Maybe a quick listen to The Dark Side Of Moon will recalibrate you to what low-frequency bass really is...

 

[Pieter1267]

@Pieter1267 Is there a specific point where you believe there is "too much bass"? I'm listening now, but it's a longish clip, so your guidance would be appreciated.

My initial analysis indicates that there is not much happening below 50Hz. Maybe a quick listen to The Dark Side Of Moon will recalibrate you to what low-frequency bass really is...

View attachment 469968

Mr Witwald you are amazing. Thank you! The youtube techno God is not a subwoofer test perse but its ongoing bass wobbling i just cant get right. Very quick it starts to bloat. What i hate about current techno djs is constantly turning bass up and down. But between minute 15 and 19 its kind of constant and he leaves it alone.

Now busy with reggea. Mr Yellowman. SKRAM config in 3 port block, high pass at 15hz 6db butt, low pass o5hz butsworth. Linkwitz riley messures a bit better but buttersworth sounds more whole in this reggea session.

 

[witwald]

But between minute 15 and 19 its kind of constant and he leaves it alone.

I did a frequency analysis of the section referred to above. The results are shown below, and it is apparent that there is even less low-frequency bass content than was identified in the prior analysis.

Below is a snapshot of a representative portion of the low-frequency waveform.

 

[sigbergaudio]

I think reducing the peak at 45-50hz will remove a lot of the perceived bloat.

 

[Pieter1267]

@Pieter1267 Is there a specific point where you believe there is "too much bass"? I'm listening now, but it's a longish clip, so your guidance would be appreciated.

My initial analysis indicates that there is not much happening below 50Hz. Maybe a quick listen to The Dark Side Of Moon will recalibrate you to what low-frequency bass really is...

View attachment 469968

Mr Witwald you are amazing. Thank you! The youtube techno God is not a subwoofer test perse but its ongoing bass wobbling i just cant get right. Very quick it starts to bloat. What i hate about current techno djs is constantly turning bass up and down. But between minute 15 and 19 its kind of constant and he leaves it alone.

Now busy with reggea. Mr Yellowman. SKRAM config in 3 port block, high pass at 15hz 6db butt, low pass o5hz butsworth. Linkwitz riley messures a bit better but buttersworth sounds more whole in this reggea

I think reducing the peak at 45-50hz will remove a lot of the perceived bloat.

I really need to 2nd skram to see where its going. At the moment the all ports open and, buttersworth 24 slope at hz low pass, high 12dB pass at 27hz plus a good 2-3 dB down at 47hz is the most versatile. The huge soundsystem reggea bass doesnt need any pre amp adjustments and all other genres are also very good. Maybe its also the 21ds115 has Fs of 31hz i think. Its not ment to do lower well. That said the room is also not big enough. Again, ill see when number 2 comes in. A few more weeks. Luckily im swamped with work.

The 40-100hz feels so unbelievably tight. Soooo much better than the Daytons. Its all very personal of course but I love this config, the b&c 21ds115 driver very very much.