Fiddling Around With the 250Ti and subwoofers (long)

I tend to agree with the folks who have posted here that the 250Ti does not really need a sub. However, I have a pair of Kinergetics SW-800 subs (five 10 inch woofers per 5 foot high column) in my listening room that I used with my Martin Logan CLS ESLs. The ESLs are boxed-up in my basement but the subs remain in the room— they are too damn big to move anywhere and I’m not ready to give up on them!

So, their presence in my room inevitably fueled speculation— I wonder what the subs might sound like with the 250Tis? Initially I did not bother because the JBLs get down into the mid-to-low 30 Hz region by themselves— who needs lower than that? Finally, curiosity got the better of me and I decided to connect up the SW-800s to see how they might sound with the JBLs.

I used, as a rough guide, the basic approach documented by JBL in their Low Frequency Systems Instruction Manual for the B380/B460/BX-63 sub/crossover combination. That is, first order high pass and third order low pass for the mains and subs respectively. Subs front plane positioned within 3 feet of the front plane of the 250Tis. I used a sub-to-mains crossover of 60 Hz rather than the 63 Hz used in the BX-63 since I have a couple of electronic crossovers that can be set to 60 Hz. I have 2 subs instead of a single 'monoized' one but I think the guidelines in the JBL literature make sense to start with.

Trying the Kinergetics electronic crossover first, I noticed a large rise below 40 Hz when testing the 250tis and SW-800s using a 1/3 octave analyzer (Phonic PAA2) and pink noise. Some of the rise is due to the room (13 x 22 x 9) but I think the Kinergetics crossover is adding some EQ. I suspect Kinergetics assumed the SW-800 subs would be placed next to the CLS, well out into the room, and away from any room boundaries, hence the EQ. However, I can only place the SW-800s behind my 250Tis and up against the wall to the rear of the JBLs so a “room gain” rise in the deep bass is not a big surprise.

I substituted my Bryston 10B sub crossover (set up with 60Hz crossover frequency, first order high pass and third order low pass) and the low frequency rise mostly went away. What remains is an essentially flat response that extends all the way down to 20 Hz and which is pretty flat around the crossover of 60 Hz. An extra benefit appears to be that a shallow dip in the response of the 250Tis by themselves in the 50-100 Hz region appears to be lessened when using the subs with this setup.

BTW, using a third order high pass resulted in a markedly less flat response around the crossover region with this set-up and no improvements were noted when switching polarity of the subs relative to the 250Tis. I have not tried crossover frequencies other than 60 Hz (yet).

Of course, 1/3 octave spectral analysis using pink noise is not a high resolution measurement for the low frequencies but it does give a rough indication of performance. I am going to try some sinewave sweeps from about 200Hz down when I get around to it.

Overall, a pretty good result and I think I will keep the subs in-line for a while. In musical terms, though, adding a small amount below 30-35 Hz does not really add all that much. But there is some nice support for really low pipe organ pedals and similar kinds of music that becomes apparent when using the subs, along with a bit more oomph in the 50-100Hz region that helps some rock and jazz music. So far, I don’t hear any added nasties like bass boom or response suckouts caused by the subs.

One minor downside—I had to resort to using a couple of older Mac amps because I could not eliminate the hum and buzz I got when using my Parasound HCA-3500 and Hafler 9505 amps, despite the usual cheater plug/plug orientation games. Not a big deal.

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...pair of Kinergetics SW-800 subs (five 10 inch woofers per 5 foot high column) in my listening room that I used with my Martin Logan CLS ESLs.

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There was a time I'd have given my left nut for that combo... To me it sounded much better
that MLogan's top of the line system.

I have 2 prs. of 250ti's .....1 set for sale shortly.

also thought that the 250 does not need a sub, but with time on my hands, I wired one in anyway. it does make a subtle difference.
used a M&K . they are notorious for weak plate amps , so I run signal to an old 40wpc NAD receiver ....turn down the treble and tune the bass ...since the sub is dual VC , L & R both go to the sub. for a cheap solution, it works OK.
Yesterday I acquired an L212 UltraBass ...going to hook it in today and demo.
Was told that the UB was JBL's original solution for the 250 before the B460 was designed.

we'll see.

My experience with both the L250 and PS1400/PT800 stacks has been that both are more than adequate down to 40Hz, room conditions notwithstanding. This presumes abundant power and appropriate setup, EQ, etc.

Given most source material having pretty scant content below 40Hz, this will rarely be a concern. However, that does not mean that those setups with less than "abundant" power won't benefit from subs relieving the strain on the main channel amps. The higher the crossover to a sub, the more power is available on the main channels, so that's one scenario where subs will make a decidedly audible improvement. I would expect that here lies the primary benefit, again given the more common 40Hz limitation.

I do have a number of pipe organ recordings, both stereo and multi-channel, with LOTS of content below 40Hz, and for those I usually like to put the L250 or PS stacks on a 40Hz crossover. It reveals a noticeably cleaner and more accurate VLF, more musical with distinct notes instead of general rumble.

So in a roundabout way I'm saying that this question has no one answer and depends more on the amps than the speakers, although the source content is easily as big of a factor.

OKAY ...slid the UB into the system ...for a 12, it really can produce ....seems smoother than the M&K.

testing it on the 2011 Immersion re-release of "Wish you Were Here" , lots of LF that I didn't know was there ..lots of machinery noises....have been adjusting phase and gain (straight up seems best) ..placement locations are limited in my LR , but even here in the rear of the house..I can feel it.

Hey RD ...is it auto ON/OFF ? yes, I know there is a power switch, but light is out.

My experience with the 250Ti and subs follows closely to what rdgrimes is explaining. The system has been through three different sub configurations. The latest being a single 2245H @ ~500 watts. Until this point my ears told me something is just very wrong. The sub isn't there until it's called upon and it's fairly clean when it's doing the job. The midrange performance is improved during heavy bass notes. I can understand that a person's listening preferences may not justify adding a sub. The real enjoyment from the sub comes from the wide variety of genres that I listen to. It's not in the system all of the time and it's nice to have a simple way to bypass it.

I can agree that the 250Ti gives excellent bass performance for most material when paired with the proper amp. The proper surrounds on the LE14H-1 are also very important as I learned later. The original foam is very compliant compared to many of the re-foam kits out there. I can say that these speakers do such a great job at everything. It's made it difficult to add a sub to the system and make a marked improvement.

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Originally Posted by grumpy

There was a time I'd have given my left nut for that combo... To me it sounded much better
that MLogan's top of the line system.

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Well, I did not sacrifice THAT much for the combo ( :eek: ) but I agree it was, and is, a pretty good system. It was a challenge to get the pair to work in my room and after a while I starting looking for something different. My fundamental issue with the CLS/SW-800: getting a really good transition between the CLS and subs. Without the subs, CLS bass was not going to hack it for me; with the subs it was hard to get a smooth response overall. In a bigger room I can see the pairing working out much better. I sort of knew that going in but I got both the CLS and subs cheap; they aren't beautiful but the panels and sub drivers are in great shape.

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Originally Posted by rdgrimes

I do have a number of pipe organ recordings, both stereo and multi-channel, with LOTS of content below 40Hz, and for those I usually like to put the L250 or PS stacks on a 40Hz crossover. It reveals a noticeably cleaner and more accurate VLF, more musical with distinct notes instead of general rumble.

So in a roundabout way I'm saying that this question has no one answer and depends more on the amps than the speakers, although the source content is easily as big of a factor.

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I'm going to try different crossover points with the Bryston and I think it will go down to 40 Hz so I'll give it try.

I agree with your observation that there is no one answer here; after living with these subs and listening to say the old M&K Realtime Direct to Disk LP of the Power and the Glory (pipe organ with 32 foot pipes), they really do make a substantial difference versus the 250Ti full range. Gotta run, its Valentines Day and my honey is home!

I do in fact prefer my 250ti without subwoofer, even though I've used it also with a B460 (and several others).

Paired up with a good and powerful amp I honestly doesn't miss any bass from the 250ti and they do play way below 40hz! It's only when watching movies I feel they need help, for music I think they sound best alone :)

Update-- I tried using a Linkwitz-Riley crossover with 50 Hz and 70 Hz crossover frequencies, fourth-order symmetric slopes. Between the two, I preferred the 70 Hz crossover and while it produces a really flat 1/3 octave pink noise response, I felt it changed the character of the bass too much. With the L-R 70 Hz crossover, the 250Ti/SW-800 combo sounded a bit too lean in the bass, not what I am looking for when adding a sub. Ideally, I would want to preserve the low end sound of the 250Ti full range with just the extreme bottom filled in. This is not what I got when using the L-R crossover @ 70Hz. It is a somewhat puzzling result since I preferred the L-R crossover when using the SW-800 subs and the CLS.

Oh well, I am very happy with using the Bryston 10B @ 60Hz with first-order high pass and third-order low pass crossover slopes.

Its possible that the placement of the 250ti will affect the outcome of different XO frequencies. That rear port can create a lot of gain, or not, depending on placement.

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Originally Posted by rdgrimes

Its possible that the placement of the 250ti will affect the outcome of different XO frequencies. That rear port can create a lot of gain, or not, depending on placement.

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The front plane of each 250Ti is 5 feet from the wall behind it and the center of each woofer is about 3 feet from the side wall. The room is narrow so I don't have a lot of options with side wall distance; I can move them forward or rearward a good bit though, maybe I'll try some more experimentation there. The subs are up against the real wall and towards the corners; there are not a lot of options for moving them around given their size and the narrowness of the room.