Film-Tech Forum ARCHIVE: Subwoofers JBL 4642A vs. EV TL880D vs. QSC SB-7218

This is topic Subwoofers JBL 4642A vs. EV TL880D vs. QSC SB-7218 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=011183

Posted by Chase Taylor (Member # 778) on 03-10-2012, 10:21 PM:

We have talked about it before but have not included the QSC SB-7218.

I'm trying to make a decision and can't make up my mind. So what is your vote for the best sub out there currently?

EV TL-880D
JBL 4642A
QSC SB-7218

Thanks
Chase

Posted by Brad Miller (Member # 2) on 03-10-2012, 10:39 PM:

Absolutely the QSC in that lineup, but don't discount their awesome 21" monster, the SB-15121. There is absolutely nothing better.

Click here to drool

Posted by Steve Guttag (Member # 268) on 03-11-2012, 07:25 AM:

Yeah, I would have picked "none of the above." JBL's 4645C is my go-to sub. With B-6 filtering, one can normally get it flat down to 20Hz. Comparing same-same, two of them will also get one 1600-watts of continuos pink-noise capability and 100dB 1W/1m sensitivity. If one wants it in a single box (like the 4642A), order the 5749. That is the bottom section of the 5742 screen system. Do use a B-6 filter to realize the extended response. My biggest critique of the JBL sub is their box construction is really wanting. QSC's cabinetry has been nothing short of excellent.

While the TL-880 may have once been a decent sub...EV has screwed with the EVX-180 driver too much over the years...its response is less predictable and I would stay away from it and other EV products (they just don't sound good).

Posted by Louis Bornwasser (Member # 3063) on 03-11-2012, 10:02 AM:

4645c as many as you can afford! Best sounding one, and, no more foam surrounds on the c model. Louis

Posted by Robert D Hall (Member # 5674) on 03-11-2012, 12:54 PM:

We started out with the EV-TLs and they sounded good.But the owner wanted more. So we got some BGW 2200s and now thats all we use. I have never heard any other sub put out the kind of sub bass the BGWs do. We have to watch and make sure we dont run them to hot because they will no jokeing tare the building apart. We have had hand rails lights and tiles fall from the sub bass.

web page

Posted by Brad Miller (Member # 2) on 03-11-2012, 02:32 PM:

Steve / Louis,

Have either of you used the SB-15121? It walks all over the 4645C.

Posted by Steve Guttag (Member # 268) on 03-11-2012, 04:55 PM:

I can't say that I have. The specifications though don't make it more favorable than the 4645C and I have verified the 4645C's response zillions of times. As a reconer, I've yet to see a driver constructed as well as the 2242H...aside from physically damaging it, it is near indestructible.

From what I can tell, the QSC will give you a wider response without B-6 but less flat in the pass-band (again, using their own specifictions)...with B-6 on the JBL, the JBL will be flatter and have deeper bass.

Louis, while the 2242 does not have foam surrounds as the 2245 had, one thing it DID have to give up is a naturally deeper bass. The stiffer you make the system the higher the "Fs" of the driver. The 2225H in a 12ft^3 enclosure could go deeper than all that have been mentioned, thus far. Another drawback of the 2245H was that it really only could handle about 350W continuous PN...so one needed a gazillion of them to handle real-world power requirements. So if the foam didn't rot on you, most people, sooner or later once digital hit, shot them out of the air gap. The 2235 (15" version) suffered similar fates...though the mass-ring in th 2235 would often shoot out through the dust cap).

Posted by Brad Miller (Member # 2) on 03-11-2012, 05:36 PM:

Give it a shot. You will be surprised.

Posted by Louis Bornwasser (Member # 3063) on 03-11-2012, 08:47 PM:

Classic loudness versus flatness debate! Louis

Posted by Steve Guttag (Member # 268) on 03-11-2012, 11:24 PM:

Considering I have yet to hear any QSC DCinema speakers I have not liked, I wouldn't be surprised if I didn't like it.

That said, they seem pretty emphatic that it needs a 20Hz high-pass and since the 4645C can go flat down to 22Hz (B-6)...the 4645C is going to have a wider/flatter repsonse, with the power handling to exceed the QSC...it is something that I'm going to have to hear and tune for it to displace my champ.

Posted by Chase Taylor (Member # 778) on 03-12-2012, 07:13 AM:

Thanks for all of the information. I have not had the chance to do many projects lately using new sound and needed some advice. I had thought about the QSC SB-15121 but had not the JBL 4645C because it was a single 18" cabinet.

Talk to me about B-6 filtering and how is that implemented?

Thanks for the help.

Chase

Posted by Steve Guttag (Member # 268) on 03-13-2012, 05:57 PM:

The 4645 series have always been single-18 systems and one just uses as many as one needs...there is no need to always use double-18s though I like the fact you CAN get it now as a double-18 by ordering the 5749 (4642A box but with two 2242H drivers).

B-6...it is a means of designing a system with a predictable roll-off with the intention of applying a complimentary filter to compensate for the roll off. Think of it as "slit loss" but for bass. The net result is a VERY flat response down to the cut-off frequency and then it sharply drops.

The problem without such an "alignment" is that the LF response will naturally decay as one goes towards the lower frequencies so it will not put out as much level at 25Hz as it does at 40Hz, for instance. Even without a B-6 alignment, there is a region, defined by the driver and the box resonance, where the driver will "unload" and behave as if it is hanging outside of the enclosure. Thus, one should always high pass a bass system so that the driver does not play in this region (it won't be efficient and will waste power trying to play frequencies it has no capability to play).

So, a typical B-6 filter will have a 6-dB boost at 25Hz with a Q of 2. One applies a High-Pass filter at 20Hz to protect the driver, you will end up (presuming the system can handle it and was designed properly) with a system that plays pretty flat down to about 20Hz with nothing more than that one filter in the signal (rather than a bunch of filters...adding all of their distortions and time variances).

Posted by Chase Taylor (Member # 778) on 03-14-2012, 09:48 AM:

Steve

As always you explain things wonderfully. Thanks for your help!

Chase