no crossover for sub 1500

[MJC]

Being that a receiver or pre/pro does bass management, there is no need to have a crossover in the sub. My 2 current subs I have the crossovers bypassed for this reason.
In the case of a pre/pro that has a variable output to the sub, that output can be set to match the low end of the main speakers. In using the L212s that low point is 70htz, and everything below that will go to the sub. So the only thing, I think, that would be needed, besides maybe an EQ, is a high-pass filter to keep out the Fs or would that be the Fc?
The published Fs is 25, but Gisard, you showed in another post that the Fs is 21.47. So is my thought process be right?

[boputnam]

Unless I'm confused - likely :yes: - not having a high-cut filter rolling off the SUB1500 (or any sub for that matter...) will/could result in a muddy sound in the 55Hz to 110Hz (or wherever) range that overlaps with the mid-bass. The sub will naturally roll-off, sure, but you might get improved imaging with a filter.

FWIW, I've done quite a bit of testing on neighbors systems with their powered subs, and universally found improved imaging and bass response by rolling-off the sub as low as possible to "mate" with the LF roll-off of the mid-bass.

[Mr. Widget]

MJC,

If you use a processor or receiver with bass management you will most likely only need EQ or B212 type filter. If the Sub 1500s were less robust you would need a high pass to protect them. I am using my pair in just this way and with no additional filter the Sub 1500s will play scary loud. (and sound incredibly good as well) When I ran the small sealed boxes EQ or the B212 type filter was definitely called for. Either of these approaches will reduce your maximum output capability, but you will probably still have enough acoustic headroom. If not you may need a high pass at 20-25Hz. By going sealed you loose about 10dB of maximum output capability at 20Hz. If you use the B212 type filter you will have improved transient response over both the EQ'd sealed box or the vented solution.

Bo,

I totally agree with you in most cases in music only systems adding a sub as low as possible is generally the best solution. I have my powered sub in the upstairs system come in at around 50Hz.

Widget

[Robh3606]

I quess is practice you are correct but I like the added flexabillity. What really drives this is how flexible that bass mangement is and if it can work in your room. I run 3 subs and all three are set up differently because of room and placement issues. No two crossover points or drive levels are the same. I use an M552 crossover between the mains and stereo subs and built in lowpass in the LFE sub. I also using steep filters on the stereo sub 24db L/R because the shallow 12db didn't do the job for me. One of the reasons I tried the M552. You know your room. If you can set it up and it works for you then great.

Rob:)

[MJC]

Thanks for the info guys. Been out of town for a couple of days.
I'm still trying to get my bearings, being until I started building the new L212s about 18 months ago I hadn't done any speaker building for over 30 years. The L212s sounded so good I didn't need to. But then came 5,6,7 channel sound.

[Mr. Widget]

MJC,
Are you planning a 7.1 set up? That's a bunch of speakers.

Widget

[MJC]

Originally posted by Mr. Widget
MJC,
Are you planning a 7.1 set up? That's a bunch of speakers.

Widget

I've already got 5 L212s up and running. Along with 2 mis-matched subs(the reason for buying two 1500). And have one extra 066 and 2105 and enough crossover parts for a 6th. Just waiting for the pair of 112a to show up from ebay.(one of the 5 is short a 112a)
Still don't know what amp I'm going to use for the subs. A pair of PE plate amps are the right price, 2000w for $700. But they don't have a bypass/THX switch, which means that the crossover has to be set to its highest setting so it won't interfere with the pre/pro crossover. And a Crown K2 is $2500.

[JuniorJBL]

Originally posted by MJC
And a Crown K2 is $2500.

Who quoted you that price. You can get 2 and an active crossover for that price here in denver. If you need help with this pm me.!:D
shane

[4313B]

Originally posted by MJC
Being that a receiver or pre/pro does bass management, there is no need to have a crossover in the sub. My 2 current subs I have the crossovers bypassed for this reason.
In the case of a pre/pro that has a variable output to the sub, that output can be set to match the low end of the main speakers. In using the L212s that low point is 70htz, and everything below that will go to the sub. So the only thing, I think, that would be needed, besides maybe an EQ, is a high-pass filter to keep out the Fs or would that be the Fc?
The published Fs is 25, but Gisard, you showed in another post that the Fs is 21.47. So is my thought process be right? I managed to get two L212 side panels hooked up with a single 1500 SUB (4.0 cu ft sealed) this weekend. I used the bass management in the H/K AVR 7200 with the sub output going to a strapped Citation 22 power amplifier. The low pass in the AVR7200 is 24 dB/octave LR at 40, 60, 80, 100, or 200 and the high pass is 12 dB/octave LR at 40, 60, 80, 100, or 200. I finally settled on a crossover frequency of 80 Hz. Overall the performance was not on par with a single Citation 7.4 sub. As would be expected, when I corner loaded the 1500 SUB enclosure it did perform better than when I merely placed it along a wall. The Citation 7.4 (JBL LE14H-1, 3.4 cu ft vented, no EQ) simply has a better balanced response. The potential of the 1500 SUB is quite obvious however.

All this was pretty much expected though. I have no doubt at all that EQ (either VLF EQ boost or B212-type low pass cut) or vented would "fix" the 1500 SUB's response. Case in point, the HB1500 is vented and the REVEL 15 is sealed plus EQ'd. One thing left to try is the B212-type cut filter. This filter consists of a 3.3 kohm resistor in series followed by a 1.0 uF parallel capacitor followed by a 13.0 kohm resistor in series followed by a 0.22 uF capacitor in parallel, all in front of a high impedance load (~ 100 kohm).

This filter is passive but one can make it active using input and output buffers if their amplifier has too low an input impedance. Basically it cuts the response in the 30 Hz to 70 Hz region. At the 70 Hz "crossover" point of the L212 and B212, both systems are down roughly 9 dB. The L212 side panels roll off at a rate of ~ 12 dB/octave below 70 Hz and the B212 rolls off at a rate of ~ 10 dB/octave above 70 Hz. Acoustically this makes for a very nice response with excellent transients and circumvents that "80 Hz bloom" that is quite common. With this filter the response of the sealed 1500 SUB should be quite similar to the B212.

[John Y.]

Originally posted by Giskard
As would be expected, when I corner loaded the 1500 SUB enclosure it did perform better than when I merely placed it along a wall.

Giskard,

This would be a good time to ask whether the C39 corner reflex that we have recently discussed in the forum would make an excellent enclosure housing two 1500's in a single unit. It certainly would be attractive and is capable of mounting dual 15 inchers. Not sure what the interior volume is, but I could scale it from the illustrations, or we could ask Oldmics to measure one, since he is restoring some.

John Y.

[4313B]

One would probably have to use a separate amp for each transducer. Minimum impedance for one is just under 4 ohms. One would also probably want to divide it into two separate subenclosures.

[MJC]

Originally posted by JuniorJBL
Who quoted you that price. You can get 2 and an active crossover for that price here in denver. If you need help with this pm me.!:D
shane
That is what I thought I saw on the Crown web site.

[MJC]

Originally posted by Giskard
[B
All this was pretty much expected though. I have no doubt at all that EQ (either VLF EQ boost or B212-type low pass cut) or vented would "fix" the 1500 SUB's response. Case in point, the HB1500 is vented and the REVEL 15 is sealed plus EQ'd. One thing left to try is the B212-type cut filter. This filter consists of a 3.3 kohm resistor in series followed by a 1.0 uF parallel capacitor followed by a 13.0 kohm resistor in series followed by a 0.22 uF capacitor in parallel, all in front of a high impedance load (~ 100 kohm).
[/B]

In that case I think I'll try the 1000w plate amps, being they have EQ. Besides I'd like to see(hear) how good they are. And if I don't like the sound then build the B212 filter and forget the EQ. Or send them back and get a Crown or other amp.
Would I assume that the 1500 would work better in a 4cuft instead of a 2.6cuft? Or 4cuft with B212 filter; 2.6cuft with EQ?

[4313B]

I wouldn't worry too much about 2.6 cubic feet or 4.0 cubic feet. It is my opinion that anything sealed using this transducer, regardless of volume, will need some kind of manipulation in order to balance the response - EQ boost in the VLF or EQ cut in the LF, skillful use of boundary reinforcement, etc.

If you go vented then I can't imagine having to worry about EQ at all. That response is a bit more balanced. It offers greater efficiency at the expense of transient response and group delay. But EQ also affects transient response and group delay.

Again, there are trade offs regardless of solution. If you recognize the inherent benefits of vented systems and can live with their compromises then go vented and forget about EQ. Just plug and play with your AVR of choice. Forget about transient response and group delay and port/duct distortion and all that crap. If it sounds good, go with it. On the other hand, if you recognize the inherent benefits of sealed systems and can live with their compromises then go sealed and use EQ boost or EQ cut.

My solution of choice with this specific VLF transducer is sealed with EQ cut in the spirit of the B212-type voltage drive based on the type of main loudspeakers I plan to use. These are all medium efficiency sealed systems using 112/2108, 115, 2122 and LE10 transducers. In other words, my specific interest in this transducer is to replace the 121A/121H B212 transducer. It's a natural.

I think this transducer is versatile enough that others will find various uses for it that will fit their specific requirements.

[andresohc]

Has anyway thought of using the Sub1500 instead of the 2245 in the clone 4345 with biamping, will the 2122h get down into the upper range of the sub 1500, might allow a smaller package. I have both speakers and havent started the cabs yet, hmm...

[Mr. Widget]

I would not recommend using the Sub 1500 up to 300 Hz. The response rises which would require EQ and the mass of the cone would really limit it's upper frequency sonics.

Widget

[MJC]

[i]

My solution of choice with this specific VLF transducer is sealed with EQ cut in the spirit of the B212-type voltage drive based on the type of main loudspeakers I plan to use. These are all medium efficiency sealed systems using 112/2108, 115, 2122 and LE10 transducers. In other words, my specific interest in this transducer is to replace the 121A/121H B212 transducer. It's a natural.

I think this transducer is versatile enough that others will find various uses for it that will fit their specific requirements. [/B]

The whole reason for upgrading the L212 system to a 5 or 6 channel system is I want more than just a HT system. I want a MUSIC system that will do HT better than most. And the B212 was a big part of that system, it had great bass. So the closer I can get those big 15" beasts to the B212 the better, and with a lot more power!
So a sealed sub it is.

[4313B]

Originally posted by andresohc
Has anyway thought of using the Sub1500 instead of the 2245 in the clone 4345 with biamping, will the 2122h get down into the upper range of the sub 1500, might allow a smaller package. I have both speakers and havent started the cabs yet, hmm... I used the 2122 and 112/2108 extensively. Both have usable response down to ~ 70 Hz in their little sealed subenclosures. The 2122 is ~ 3 dB more efficient. I think the 4343/4344/4345 10-inch 3-way coupled to the 1500 SUB's could potentially be quite interesting...

[4313B]

Originally posted by MJC
Would I assume that the 1500 would work better in a 4cuft instead of a 2.6cuft? Or 4cuft with B212 filter; 2.6cuft with EQ? Visiting this again, the 1500 SUB with B212 filter in a 2.6 cu ft enclosure has usable response down to ~ 14 Hz and the 4.0 cu ft can get down to ~ 12 Hz. Big deal! Who cares! I'd go with the smaller volume.

The 121A/121H in the B212 enclosure is usable down to ~ 12 Hz. When one adds in room gain the trouble starts real quick. No wonder those old geezers crack plate glass picture windows when used in pairs and quads.

Anyway... I'm sure the 1500 SUBs will cause considerably more damage if one were to use them offensively.