Talk:Crossover

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Can the B1s handle the load?


Can the B1s handle the load?
Hi, I'm a longtime follower of Bose's unique product line. I have a technical question involving the performance of the Bose PAS's B1 bass module. I have been involved in Home Theater for a very long time (though not with Bose equipment - a _bit_ out of my price range). My question is this: I see that your B1 bass module only contains two 6.5" woofers. I notice that the way the B1s hook up is from the PAS into one B1, and then into the next B1, and so on, which implies that each B1 has an impedance that is twice the lowest impedance that may be driven by the PAS's amplifier. This would tell me that the 250-watt amplifier is only actually delivering 125 watts into a single-B1 setup. I find that I am highly skeptical of the B1's ability to produce bass that can keep up with the 500 watts that go into the Cylindrical Radiator speaker. One of the biggest fundamentals of audio theory that I know of is that "there's no replacement for displacement". So what I'm really asking is, how well does the B1 keep up with the PAS's own speaker?

Also, are there any plans to release a B2 bass module (with a pair of 10" woofers, perhaps) for those bass players and percussionists who find that even two B1s don't quite cut it?
For clarity, this "buz" is not "buz-at-Bose".

Thanks for your question. The system, balanced, and undistorted, will reach its full output with two B1s. When you use one B1, it is equally balanced sound across the whole spectrum, but has a little less total maximum output.

The math is not simple, and there's no tricks here. Perhaps one way to think about it is that those 125 Watts are all going into only about two octaves, while the 500 Watts powering the L1 are going into seven octaves.
It's been my understanding, however, that it takes a huge amount of extra power to drive bass frequencies because of the extra driver excursion required - again that "displacement" I was referring to. In fact, I would expect a PA system with 500w mains to feature a full 1500w per side for the subwoofers. And since the B1 covers the range between 40 and 180 hz, it is essentially a subwoofer for the PAS.

My point here is that even though your B1 module is only covering two octaves, those are the most demanding octaves of them all.

Perhaps the answer is moving to powered "B2" bass modules? Weighing in at 800w each, with two high-excursion 10" drivers I'm sure that solution would work well to allay the fears and skepticisms of even your most demanding customers.

This post might not get approved, anyway, since I might be getting too technical.
buz,
I really appreciate your logic, and understand the math, as Ive been down the "old school road", . . and I may be totally wrong, but I think I get this stuff. Bose uses lower amounts of energy to produce waves of sound that travel farther without having to be much louder at their source than they are at their point of dissipation. That is to say, they create sustainable sonic resonance, using every acoustic surface in unknown spaces. It does seem unacheivable, . . but those are the secrets these guys aren't stupid enough to share!
buz, the price is right, the trial is 100% including freight! Hear it, . .mess with it, . .send it back or keep it!
Oh, . . No, . . I have a wife and two kids myself, and no current spendable $$, so I've sold everyone in my circle to try it, and I'll ring in asap.
The box is not your friend! Step out and rethink! I know, it'd be nice if Bose would enlighten us, . . but we'll find out eventually! Hell, you'll probably be the one to figure it out first!
Let me know!
dfwtbewaitinformyshotatit
Buz,

Good comments, and I would generally agree with them in theorey. One minor technical point: I think the bass subwoofer crossover point is at 100Hz, by the way.

For people who want more juice in the low frequencies, Bose says you can just run a line from the Amp 3 Out on your main PS1 to *another* PS1, from which you can drive as many as 6 more B1s (two per channel, of which there are 3 in the PS1 since you won't have a tower plugged into it). That gives 1000W total into the bass range for those who want it.

But that's where the discussion takes an interesting turn. I'm a bass player in a loud rock band and also in a not-so-loud party band. I have an 18V active preamp on my bass with 3 EQ knobs for boost/cut on low, mid, and treble. In ye olden days, going through either my 1x12" 100W combo amp, or my 2x10" + 1x15" 600W@8Ohm bass rig, I generally played with the mid and treble knobs flat, and the bass at about 3/4 boosted.

I first plugged into the PAS and within 10 minutes I had rolled that bass boost back to maybe 1/4 boosted. The sound of the bass was still there, but without that uncomfortable, muddy THRUM that I was accustomed to. I tried doing the same thing through my bass rig later (rolling back the bass) and instead of clearing up the mud and giving me a nice clear low, it cleared up the mud and gave me a gutless little hum, which is what you're assuming you'll hear with a scant 250W of bass power with a PAS.

Maybe my ears were fooled, and your mileage will certainly vary, but for my bass purposes, 2 B1s seem to do the job just fine for now.

---------
Hourglass http://www.hourglassband.com
It seems that they are a few misconceptions about the B1, what it does and how it works. First and foremost the B1 offers a "scaleable" solution for bass requirements. One B1 is plenty unless you are a bass player, drummer or play back recorded music and gernally play (either of these) loud. So far singers, guitar players, keyboarder, horn players seem very happy with a single B1 or in many cases even no B1. Different instruments have different requirement and the B1 is intended to address that need through scalability.
Most bass players and drummers seem to do okay with two B1s. If you are playing really loud and/or larger venues you can add up to six more (using an external PS1 or power amp) for a total of up to 8.
That should provide ample low end but if even that is not what you need or want you can hook up an external powered subwoofer to the "Bass Line Out" and don't use any B1s at all.
We certainly don't want to create the impression that a single B1 outperforms a 250 pound 2x18 subwoofer, although I would claim that you'll be hardpressed to find a cabinet with similar efficieny, bandwidth, power output capabilities at 28 pounds of weight (or thereabouts).
However, these things are difficult to put in numbers. Please read this and this post to learn why that is.
I found in the past (both as an active musician and as an engineer) that my preconception about what a 6.5" woofer does or what an 10" woofer does weren't really justified. Designing bass boxes is complicated and a large variety of factors play a role. Cone diameter and nominal power handling are important ones, but they are only a few amongst many others and not neccessarily the most important ones. Bose Corporation has a long history of trying to get a lot of bass out of small enclosurese and we certainly put all we know into the B1.
In the end the only thing that will tell you whether what it actually does are your own ears.

Hope that helps

Hilmar
oops I forgot,
Crossover is actually 180 Hz, but it is an intelligent crossover, i.e. it changes frequency and gain depending on how many B1s are attached. This is another advatage of having a complete system, all components know about each other and can truly be optimized.
Hi all,

Here's what I've been experimenting with. I have two PAS for our band. I'm the bass player and play through an Ampeg SVT4PRO and two PR410HLF cabs. I also have a PR15H cab with a JBL 2226H 4ohm driver. First of all, if I connect the PR15H to the B1 I get ALOT of bass, but is there an impedance problem? The other experiment I,ve tried is using the Bass Line Output out of the PAS into one of the channels of my SVT4PRO (490 watts)then to either the PR15H or one of the PR410HLFs. The other channel powers a PR410HLF. Now here where it gets interesting. I run a cord from the line out on my Ampeg head to input 3 on the PAS. I then run the level up on the PAS to "just enough". It really sounds AMAZING! By the way, the other B1 goes to the other PAS to make two on that side. All four of us sing and use inputs 1 and 2 on each side. The next step will be to use a small Peavey RQ200 mixer to mic the drums and mix in the guitars. Our lead player will play through his Marshall head and "gain it up" then line it out to the PAS. The rhythm guitarist will plug directly into the mixer. The mixer is a stereo one so we can pan the guitarists to their respective positions keeping with the Bose philosophy. The drummer will mix to the center with the kick drum primarily to the "big bass " side. Left to right, bass, drums, lead and rhythm. Now the funny part...we haven't got together to try all this yet! I just got tewo Bose systems and have only used them for vocals, so far with amazing results. Anybody out there as bad a tweek-geek as me? Anybody got any coments or suggestons?
Hello Billybass,
What an inventive way to use the Personalized Amplification System. This is one of the most unique applications for bass reproduction I have heard of. Congrats!!

Quote 1 “First of all, if I connect the PR15H to the B1 I get ALOT of bass, but is there an impedance problem?”

The total resistance on a single output is 8ohms. Each B1 bears an 8 ohm load (4ohm each when 2 B1s are connected in parallel). So according to the specs of your PR15H cab (4ohm JBL 2226H , 4-pin Speakon connector), impedance-wise, combining your cab with a B1 in parallel (2.6ohm) will be an issue. Also keep in mind, when a B1 is plugged into the power stand , all of the outputs of the power stand are EQ’d for B1 specific use. So, there is an EQ curve being sent out of the power stand, down through the B1, and into your cab.

Quote 2 “Our lead player will play through his Marshall Head and "gain it up" then line it out to the PAS.”

I recommend that your guitar player research some of the insightful information left in this string about getting great tone from a Head and then playing through the Personalized Amplification System. Tube Amp Trends

You seem like you have an advanced grasp of how to apply multiple instrumentation to your 2 existing systems. Your external mixer idea is right on track and I think you’ll have great success. Keep up the creativity because your input will help everyone else (including us) get the most out of this system.

This message has been edited. Last edited by: <Greg-at-Bose>, Tue May 11 2004 01:57 PM
Thanks Greg,

Actually the PR15H has a JBL 2226G which is a 4ohm driver. If I plug it into the B1 I'll get 3ohms...right? Is that too low for the amp?

The second option, which I like better, has me using the bass line output back to one of the power amp inputs of the Ampeg amp. What are the crossover specs for that output?
Let me chip in here, if I may.

Warning: you may run your power amp with the wrong load

If you are actually using a 4 Ohm driver in the PR15 Cab, then the total impedance from the B1 and the PR15 would be only 2.6 Ohm. That's actually to low for the power amp. Its protected against "underload" but its only defense mechanism is to shut down and that's most likely to happen when you are rocking&rolling on the gig which also happens to be the moment were you really don't want it to happen. If it does happen, you simply need to power cycle the unit to get it up and running again.
I do not recommend running two different cabinets off the same amp. They may interfere with each other and cause cancellation at some frequencies.
You can try to run the PR15 without the B1 directly off the AMP3 out That makes sure that the power amp is happy again. In the absence of the B1 the power amp will produce a "flat" signal which may be just what you want. In this case also the crossover is moved down to 110 Hz. That may cause too much heavy lifting for the L1. To avoid that, you can simply take a spare 1/4 plug (no cable attached) and put it into the Bass Line Out. In this case the PS1 thinks you have an external sub connected and will move the crossover back up to 180 Hz (but still flat without an EQ).
If you are using the Bass Line Out anyway, the cross-over is already taking care off. I hope that all makes sense to you, if not please post back.

Happy experimenting and let us know what you find.

Hilmar
So does this mean that when the B1 is absent, the L1 runs down to 110hz?

...and if I tap a signal out of the bass line out, (to my external subs), that signal is crossed at 110hz without a B1 and at 180hz with a B1 present?

quote:


Originally posted by RGB:
So does this mean that when the B1 is absent, the L1 runs down to 110hz?



That's correct as long as there is no B1 nothing is attached to the bass line out.

quote:



...and if I tap a signal out of the bass line out, (to my external subs), that signal is crossed at 110hz without a B1 and at 180hz with a B1 present?



Not really. Whenever you connect something to the Bass Line Out, the system will detect that, assume that you have something attached that can do the heavy lifting and set the crossover to 180Hz.
There is a difference however, whether you attach a B1 or not. If a B1 is there, it will assume that there are more B1s connected through the Bass Line Out (using a second PS1 power stand or an external power amp). Therefore the signal on the Bass Line Out will be equalized specifically for a B1.
If there is no B1 connected to AMP3 out, the system assumes you have a 3rd party subwoofer atatched and will provide a flat 40Hz to 180 Hz output.
That is a little complicated, but the system attempts to guess what you are trying to do and adjusts itself accordingly. I hope that makes sense to you.

Hilmar
Yes Hilmar, it makes perfect sense to me and I thank you for your help!

I just ordered my system yesterday, (L1 w/2 B1's), from MF and should have it within the next two weeks.

One other question, will my new system have the upgraded remote and the B1 bags?
Unfortunatley that is hard to tell. The remote should have a lable on the back that says "Model R1 ver. 2". If the "ver. 2" part is missing, you have got an old remote and can call (877) 335-2673 to have it replaced. If there are no B1 bags, you'll have to wait a few more weeks until we can ship them to you.

Please enjoy your new system and let us know what you find.

Hilmar
Will do!....and thanks again!

Rick
I currently use an L1 with 2 B1s, primarily as a bass amp. I'm considering adding a powered sub for a little more low end, and hopefully more punch, too. After re-reading all the posts in this thread I think I'm clear on the fact that with B1s attached, the L1 crosses over at 180 Hz. With no B1s and/or with a cable plugged into the bass line out jack the L1 crosses over at 110 Hz. So I'm assuming that with 2 B1s attached and with a line out to a powered sub, the L1 is still EQ'd at 180 Hz. I've been looking at a few different powered subs and it seems most of them only go up to 100 or 120 Hz. I want to use the B1s (and the amp in the L1) that I already own and possibly add a larger speaker and 200-300 more watts for added depth. I'm wondering if there will be something missing in the 100-180 Hz range by using both the B1s and a powered sub that crosses over at 100 Hz. Do you know of a powered sub that crosses over at 180 Hz? Also, would it be possible to easily modify a sub to cross over at a higher frequency, like 180? I'm thinking that a lot of the punch that we bassists seem to be missing is in the 125-175 Hz range. Any suggestions?
Hi Dan -

For added low-end with the L1/2-B1 PAS I've been using an Eden Nemesis NC210, 2x10-225W combo. It adds plenty of extra thump, with more headroom left on the amp. This will not go to full-rumble like an SVT or equivalent, but is plenty loud.
At 47lbs it's heavier than a B1 Big Grin , but it is one of the lightest 2x10 combos available.

Feeding the PAS Bass Line-out to the Nemesis Effects-return lets me use the 3-band + semi-parametric EQ section on the Nemesis to fine tune the low-end sound. I haven't noticed any gaps in frequency response when set up this way, but haven't specifically tried to identify whether there are any, so maybe I've just been dialing in the EQ to compensate without realizing it.

With this setup (Ch 2, presets v2 #65/66, PAS Remote EQ: Bass Flat, Mid -3dB Treble -6dB) I've found that I generally have to roll off the Nemesis Bass control about -9db, or the PAS line-out causes speaker flatulance. Treble is also rolled off a little, with mids flat. I sweep the parametric EQ until things sound subjectively "good".

TLR
Hi, troberts. Thanks for the reply. Ironically, a Nemesis combo was what I was using before I bought my Bose system. One of the reasons I went with the Bose system is that I couldn't fit the Nemesis into the trunk of my little red sports car. The Bose fits in there with room to spare!
OK, here's my experience with the B1...

We are playing through a PAS, with a KLH E-8FS powered subwoofer. After using the B1 a few times, I was very unhappy with the "rumbling" undefined boomy sound of it. I had picked up the KLH (8"woofer/100W) a few months earlier, on sale for $50, and when I plugged it in to see how it sounded, I was blown away. It was punchy (in fact tonite, when we started up, someone came up to us seriously bewildered, as he could hear the "bass player", but couldn't see one!), plus it has both a gain control & crossover control. I was disappointed too, that the Bose has no adjustment possible....

Both my guitarist & percussionist agree it blows the B1 away....how could this be?


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