RT-2 Horn sub, the result

[Elbert]

jbell, that really looked interresting in deed.

But looking at the group delay plot, well.. it looks a bit "dramatic" how would this really sound??

But in terms of sheer output and extension vs cone excursion, it looks very good in deed!

Tried the same sim with the peerles SLS woofer, and that was all over the place with wild dips and peaks!

And regarding unloading of woofers below system resonance, i guess the trick is to build a system with low enough resonance!

I did a BR calculation for the Perless SLS, and sure enough, at a certain frequency at a certain power level, cone ecursion would just zoom off in to sky. But as this only happened at sub 20 Hz frequencies, I guess it would matter too much in real life!

Worst case, one could throw in a subsonic filter..

greater Xmax = greater Distortion? I wouldn't say that this is a given, but building a good driver that can deliver high Xmax AND low distortion comparable to a lower Xmax driver, that is perhaps another story.

[GM]

Originally posted by Elbert

And regarding unloading of woofers below system resonance, i guess the trick is to build a system with low enough resonance!

With a 0.707 Qtc sealed rear chamber the driver never unloads, though of course it can be overheated to excessive thermal power compression/destruction, so using an Fs, Qts to fit the max Vb the horn allows seems the best compromise, but it appears that in 1pi space this horn is going to need considerable EQ to be tonally flat to its theoretical ~42 Hz (IIRC) sealed cab limit, i.e. a decent mid-bass horn, but not a bass 'shaker'.

If you can increase the rear chamber Vb, then lower Fs, higher Xmax drivers to go lower is an option, but all things considered, optimizing the RT-2 and adding 'sub' TL's, tapped horns or large EBS vented alignments tuned <20 Hz is what's required for high SQ to the limits of audibility combined with plenty of power to get the desired tactile feel of a live event.

GM

[Elbert]

Hi GM,

Yes looks like with all the EQ hammering required to tame the horn, there is not that much benefit left afterward compared to say a BR enclosure..

[Elbert]

Looking at some alternative solutions...

Enclosed is a frequency plot done with WinISD with a Peerless SLS 12 in a 230 l vented cabinet. (about the same volume as the RT-2 horn)

http://www.mamut.net/dynabel/subdet329.htm

At near maximum linear excursion, the plot shows a flat response down to a -3 dB at 23 Hz

I guess a horn would have to be pretty big to do the same..

Of course a horn might play 20-30 dB louder, but i guess 110 dB will be acceptable for domestic use anyway..

I've read that the SLS woofers are only suited for closed box, but the data sheet states that extended response can be achieved in a vented design of 55-75 L..

Again, the sim I did was for an enclosure significantly larger than that.. Am I missing something out here, or might this driver actually work as well as it looks in such a very large BR enclosure??

[tinitus]

Originally posted by Elbert

I've read that the SLS woofers are only suited for closed box, but the data sheet states that extended response can be achieved in a vented design of 55-75 L..

Again, the sim I did was for an enclosure significantly larger than that.. Am I missing something out here, or might this driver actually work as well as it looks in such a very large BR enclosure??

Carefull, there a risk of sloppy bass doing that

Its true, many genuine sub drivers have high Qts, indicating the use of closed box, yet they are widely used in BR...well, I honestly dont understand it really, but it could be part of a commercial interest making it look better in BR

[Elbert]

Sloppy bass...that doesn't sound like a nice thing....

To me, the highly subjective term "sloppy" would indicate uncontrolled cone movement of some sort, perhaps the sort of result one gets when an enclosure stops loading the driver acoustically below the resonance frequency?

Perhaps the reason that some drivers are not recommended for BR enclosure is that the enclosure then needs to be very large for the system to work properly?

[tinitus]

Well, its theoretical as I dont know any of these woofers, in which case I prefer follow the rules

But I kind of look at it like this

A small woofer may not present any poblem doing like you suggest
But a big woofer goes much lower, where there are higeher demands fore absolute control

Further a closed design rolls of very gradually and controlled, and due to that it may not present so much of a problem playing a bit of the lows
A BR on the other hand is going on at full blast, which is a whole different situation
Actually you will often see that the best woofers suited fore BR isnt actually going much lower than a closed, due to low Qts
In between theres a lot of good woofers that will do both, where the BR will do a little better in a small area, but the deepest lows are the same fore both closed and BR, and even sometimes a closed go deeper, only with less output

In these times it seems like its only possible to get really low with high Qts sub drivers in BR...I think its a compromise, and may be one reason why so many people experience that a sub is best fore films, and less good fore music
And theres room gain too, which many seem to forget

Its possible to design a sub driver suited fore music going really low, without the use of very heavy cones and huge stiff surrounds...but it wouldnt be good at very high SPL, which seems to interest most people, so the market may be too small

Well, SBAcoustic seems to be going in the right direction

But mostly it all begins with looking at the compromices on hand...seems we cant have it all in one

Oh yes, I have always heard that the best sub is one you dont hear, and its main feature is improvement of the soundstage, which has nothing to do with playing loud...probably many people will be very dissapointed with that

[AndrewT]

Originally posted by tinitus
Oh yes, I have always heard that the best sub is one you dont hear, and its main feature is improvement of the soundstage, which has nothing to do with playing loud...probably many people will be very dissapointed with that

I'll remind you what I said about my modified Tannoy B950.

Listening the the TannoyB950 + Satellites Tannoy Reveal6D was good.
Listening to the Satellites on their own was poor. Switching them to wideband improved but nowhere near the support from the B950.
Listening to the B950 on it's own, there was almost no sound to be heard.
But, when both were on, it was very obvious that the bass was there.
BTW, the cross over was LP=150Hz 4pole and the HP was 80Hz 2pole + 150Hz 2pole.

[bjorno]

… Enclosed is a frequency plot done with WinISD with a Peerless SLS 12 in a 230 l vented cabinet…I guess a horn would have to be pretty big to do the same...

… Enclosed is a frequency plot done with WinISD with a Peerless SLS 12 in a 230 l vented cabinet…I guess a horn would have to be pretty big to do the same...

Of course a horn might play 20-30 dB louder, but i guess 110 dB will be acceptable for domestic use anyway…I've read that the SLS woofers are only suited for closed box, but the data sheet states that extended response can be achieved in a vented design of 55-75 L…

Hi Elbert,

You are right a horn would be huge but not if a BP-TQWT, See picture 1(2).

Actually the 230 L BR box you mentioned can be compared to the about 215 L simulated BP-TQWT in picture 2(2) where the difference can be observed.

Note: A BP-TQWT is stuffed like an ordinary TQWT and the ripple over 90 Hz is negligible (IME) if simulated as can be seen using MJK:s TL programs with about 8 kg/m^3 stuffing density.

IME. A tapped horn with a series inductance or not/ BR-box has much lower SQ than a BP-TQWT that is FR QW extended, traded for BW from mid-bass efficiency.

IMO 110 dB is more SPL I heard in an ordinary living room that I could copy with.

b

1(2)

[bjorno]

2(2)