Controlling excursion below tuning frequency

[j.burtt]

Is there a subsonic filter most are using with the pro amps to control excursion below the tuning frequency on the LLT enclosures? I loaded Winisd Pro and have been modeling some of the designs some of you have already built to try to get an idea if my thinking is correct or not and when I got to the excursion field, the measurenment goes vertical.

James

[Quake25]

I think most eventually lean towards getting a Reckhorn B1 subsonic filter, but there is usually a built-in "rumble" filter on most amps that, although usually come with a bass boost, can also help to mitigate the low-end frequencies.

As a last resort, the WinISD should model the excursion at a certain point for both Freq. and Wattage. Something as simple as lowering the sub's main volume can also help to avoid this effect (not the prefered method).

[atledreier]

You can model in WinISD and make sure your amp fall off enough to not damage your driver below tuning.

[mayhem13]

Here's a great, yet inexpensive product to help fine tune a ported sub that includes a subsonic filter as well as 2 channel PeQ. It's nice to have something for those sneaky scenes where the LFE channel runs away with itself unexpectedly. Not all Pro Amps have subsonic or rumble filters and some do at too high a frequency that's not defeatable. Remember to check the Specs.

http://www.edesignaudio.com/product_...roducts_id=657

[Sonnie]

I do wish the Reckhorn B1 offered infrasonic filtering below 10Hz. Most everything I have been modeling only needs from 5Hz to 8Hz filtering. And for the same price, the ED offers down to 5Hz HPF and the PEQ ta boot. Maybe we can get Bob at CSS to source us something similar to the ED.

[Mike P.]

The Reckhorn B1 with some of the E.D. features would sure be nice. Too bad the E.D. has problems working with pro amps.

[mayhem13]

Does the SMS-1 feature any highpass/subsonic control?

[Sonnie]

Mike P. wrote:

Too bad the E.D. has problems working with pro amps.

What problems might those be and why didn't you tell me before I ordered two of them?

[Ricci]

Apparently the ED's have low voltage that doesn't push the pro amps very well.

I always model the intended sw with the maximum amount of power that might possibly be dumped into the driver. Wherever the excursion goes past xmax below tune, plan the SSF accordingly. This is worst case scenario, which probably would never happen, but better safe than sorry.

The Rane PE-17 is a nice filtering unit too. Adjustable down to 10hz and also with 5 band fully parametric eq and signal boosting. $140 give or take on the bay.

[Sonnie]

That is definitely a shame on the ED. They lost a sell for that. I know of nothing else that filters as low as 5Hz... without mortgaging the farm that is.

I with you on the modeling Josh. I think in most cases we probably won't be pushing the absolute full power into our subs... as in 1950 watts from an EP2500, especially at 10Hz and below, but I would rather be safe in the modeling in case of something unforeseen.

Of course we can always model without the HPF to see what it looks like at a more normal listening level. That will give us a good idea of what we will be listening to most of the time.


You know... the EP2500 has a 5Hz HPF in it, but in order for it to be active you have to have the 30Hz or 50Hz HPF turned on, which doesn't make a lot of sense. I wonder if someone can make it work without having to engage the 30Hz/50Hz filter... OR how can we disable those filters.

[Ricci]

Hmmm. I did not know that. Seems weird to have it set-up that way.. Perhaps ask Neo-Dan about the 5hz filter. He's messed with the EP2500 a lot.

[NEO Dan]

My EP2500 measurements:
Off, 30Hz, 50Hz


(Chasw?)Chuck) over at AVS performed a through bench testing of the ED unit. The unit basically has no gain, when it's cranked you are at unity gain.

The RANE PE17 and Behringer MIC2200 are good units. Altough the route to a 10Hz HPF on the Behringer is not as straight as you'd hope for
The results are good though:

[NEO Dan]

[NEO Dan]

I have a couple PE17's and the MIC2200 and I was using the Behringer. It worked great.

[pietsch288]

hey a little off base........I don't need a subsonic filter (I have the SMS-1), but I am looking for two units to adjust phase and or polarity. Is the ED the least expensive out there???? Background time.......I have 4 svs cs ultras running off of 1 ep2500, two dead center of the front wall and two dead center of the back wall. But I was thinking of moving the subs so 1 sub would be dead center of all 4 of the walls (front-back-each side). I all ready have a second ep2500 so each sub can have its own channel but I am assuming that I will need to adjust phase for each sub individually. The frond and back subs are opposite polarity so I've been reversing them on the amp (works perfectely) but if I move two of them to side subs I assume I would need to do some adjusting. First of all is it worth the extra money to have 1 sub dead center of all 4 walls or is it just as good having them center of the front and back walls??? I do have a front couch and a back couch so my thinking is that by moving a sub to the center of all 4 walls the bass will be more even between the two couch's. The difference between REW graph's are almost upsetting between the two couch's so I would like to even out the bass for both couch's if at all possible, thanks rich

[Sonnie]

Actually that probably needs a thread of its own, but you are still going to run into the gain issue.


Wow Dan ... that 2200 creates a literal cliff instead of a gradual roll off starting at a higher frequency. I think I actually like that better than anything else I have seen.

[NEO Dan]

Sonnie,
it's a combination of HPF(20Hz)not as advertised) and EQ. The net result is a very steep filter with an Q=~1, great for ported boxes tuned near 10Hz. For your specific venture into the infrasonic you could possibly be better off without engaging the units HPF, just using the units natural roll off and possibly making minor tweaking with the PEQ.

Here is the unit's stock response with the HPF off(magenta), On,(red), On+PEQ(yellow):

[NEO Dan]

pietsch288 wrote:

I have 4 svs cs ultras running off of 1 ep2500, two dead center of the front wall and two dead center of the back wall. But I was thinking of moving the subs so 1 sub would be dead center of all 4 of the walls (front-back-each side).

You might try 2 up front splitting the wall into thirds, take a distance measurement with the AVR's auto cal mic (YPAO/Audesee) if possible.
Then disconnect the front 2 and start moving and measuring(start with 1 sub) the distance(using the AVR's auto cal routine) for the back 2 subs until you match up the distance. I'd try a sidewall placement in the rear third of the room if possible.
For me this whole process is and ultimately I ended up with my subs up front between the mains.

Sonnie is right, you need to start a thread.

Regards,
Dan

[Sonnie]

Definitely something to experiment with.

It is probably one of the most flexible units I have seen to apply an infrasonic filter.

[SteveCallas]

Really no need for a proper LLT. Not only have I been using mine for over 3 years without one incident, but if you take a look at Ilkka's measurements of the quasi LLT using a ~17hz tune, there were never any problems aside from increased distortion even at the highest sweep level down to 10hz without any highpass.

[Ricci]

Unless you know the roll off of your electronics chain I would not count on it solely to protect the driver. The lower you tune the safer you will be to run without a ssf. At 10-12hz you may be ok with some electronics roll off. At 15hz and up I would not run without one even with the brawniest driver, unless it was music only. I have seen numerous damaged drivers from over excursion in ported cabs. Including a pair of TC2000 15's tuned to 16hz similar to the one in Illka's test, that were destroyed by a CE4000, which rolls off everything below 10hz. If you are smart about it and know what you are doing like Steve, you might be fine. What if though? Your listening tastes also matter greatly. Are you a reference level kind of person or a -15 from reference kind of person? it makes a big difference.

[Sonnie]

Yeah... it really doesn't cost much at all to be on the cautious side of things.