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The Dude

JBL 2445 vs P. audio BMD 750 Series II

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Has anybody had a chance to compare these 2 drivers. Price on the P audio is 169.00 from U.S. Speaker, and if you shop around you could get the JBL's used for about the same price.

I figure if anyone has it probably would be DJK, I just wonder if the JBL's would have better sound or would handle crossing over better at around 550ish give or take.

If I went this different route, I would be mounting them on JBL 2365's or 2360's.

Thanks.

Edited by duder1982

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This is a side note.

I have used the JBL driver on the 2360 horn. At a component level, the horn will sound better if you cross at a higher fequency (say, 700-800Hz). I am not sure what you are doing for the bass bin, so I don't know if this crossover point is appropriate at a system level.

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Thanks Tom,

As for the bass bin, I am using the Jamboree. I don't know how high I can cross it, I just shot for the 550ish as that is what seemed to be the overlapping point of the hf driver I am using now on top of the Jamboree. I would have to run a test and see how high I could cross the Jamboree.

So from what I gather what your saying is, that the JBL would do better crossed higher.

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Nick,

I think he is saying the horn will sound better crossed higher, no matter which driver you use. Some of that will also depend on the levels at which you listen to your music. Since this series of horns (I have some 2365 horns) have a diffraction slot, they can overload more easily.

Bruce

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Bruce hit the nail on the head.

As a system, there are a number of considerations that go into picking a crossover point. This is one of them.

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What does it mean to over load, according to the spec sheet on those horns it claims they can be crossed as low as 300 hz with the right driver. I guess this is something that lead me to believe that most horns low frequency cut off is all so do to the driver capabilities as well. Not questioning anyone's knowledge just trying to understand more of this.

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If you cross too far below the horn's cut off, you lose the loading from the horn, and the diaphragm will bottom out. Horns and drivers form a system, and you won't know what that system will be comprised of until you know something about the parts and how they are going to interact with each other.

The lower the order of the filter, the higher you want to cross. OTOH, if you cross too high, the power response will suffer and the system won't sound cohesive.

The K-400 has a Fc of about 270Hz. When attached to the motorboard, the added air mass lowers it to 240Fc. Using a first order network, PK crossed this horn at 400Hz, which is almost a full octave above its Fc. Crossing too low increases distortion, so most try to get an octave or more above Fc. As you steepen the slope of the filter, you can get closer to the Fc of the horn. This however, is a gross oversimplification. There's a lot to this that most don't take into consideration.

https://www.aperionaudio.com/blog/crossover-design-and-theory

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If you cross too far below the horn's cut off, you lose the loading from the horn, and the diaphragm will bottom out

So basically you are no longer using the horn for what it is attended for, and making the driver do all the work running the risk of damage.

There's a lot to this that most don't take into consideration.

I am finding this out, but hey I am young enough if it takes me another 20 years to learn. I will but up there with the rest of you :D . All I know when ever I try to learn something about this stuff, I google things and get a very long explanation on the subject. Take for instance I googled how to find or figure a horns Fc, here is what I get.

http://www.quarter-wave.com/Horns/Horn_Physics.pdf

https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf

Dean thanks for taking the time to explain that, it gives me something to read and take time to understand.

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When attached to the motorboard, the added air mass lowers

This had me thinking too, does this happen to every horn, and could this be a good thing since in a way it lowers the Fc. I don't think you could do this with the JBL as it has a weird lip. But with the EV hp640 you could mount it like the K400, If all of this is true, how much would it help the sound with this horn when mounting to a motor board.

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If I'm remembering this right, and there's a good chance I'm not - I believe the motorboard thing is how PK justified truncating the horns - I think they're supposed to be longer than they are. I can't speak to the effect with other horns, because I honestly don't know. This is an example of me simply regurgitating information without really understanding how it works.

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simply regurgitating information without really understanding how it works

That is usually what I do, then I tell people I stayed at a holiday inn express.

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This is a side note.

I have used the JBL driver on the 2360 horn. At a component level, the horn will sound better if you cross at a higher fequency (say, 700-800Hz). I am not sure what you are doing for the bass bin, so I don't know if this crossover point is appropriate at a system level.

I agree with the Xover point. Having owned measured and listened to that 2360A horn for almost 2 years, I'm backing that one 100%. I would look for a used JBL 2446 driver because you can put the True Extent Beryllium as an upgrad. But honestly, in the horn, I prefer the EV DH1A driver, which is available for about $90 on Ebay. Just make sure you get original EV diaphragms, and not knockoff replacements. Either JBL or EV is a good choice, but the EV is cheaper, so represents a better bang for the buck. Again based on ownership, measurement, and long term listening drives my points here.

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Thanks Tom,

As for the bass bin, I am using the Jamboree. I don't know how high I can cross it, I just shot for the 550ish as that is what seemed to be the overlapping point of the hf driver I am using now on top of the Jamboree. I would have to run a test and see how high I could cross the Jamboree.

So from what I gather what your saying is, that the JBL would do better crossed higher.

If you are using K-33's in the Jamborees, the mass break point is too low to cross high. Your best bet would be EVM 15B or L's. Next would be the Eminence 15C, or the 15 LFC, which models very much like a Klipsch K-43.

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If I'm remembering this right, and there's a good chance I'm not - I believe the motorboard thing is how PK justified truncating the horns - I think they're supposed to be longer than they are. I can't speak to the effect with other horns, because I honestly don't know. This is an example of me simply regurgitating information without really understanding how it works.

On the right track here, but it's more about making the small mouth behave like a bigger mouth. In conversation, I remember distinctly PWK saying that he thought his K-400 was "a lot longer than it needed to be" after he designed and measured the K-500's performance for the Belle.

Personally, I think that the full length of the K400 was better because it reduced the time delay between the Khorn woofer section and the midrange and gave the lowest rolloff possible to mate with the mass rolloff of the woofer.

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What does it mean to over load, according to the spec sheet on those horns it claims they can be crossed as low as 300 hz with the right driver. I guess this is something that lead me to believe that most horns low frequency cut off is all so do to the driver capabilities as well. Not questioning anyone's knowledge just trying to understand more of this.

You can probably cross lower than 700 Hz., but in my case, I had a Peaveay MB-1 from 180-700 to fill that gap, since the mass rolloff of K-33's hits at about 180, which were in MWMs bins at the time. With active digitial Xover you can PEQ it down to 450-500, but no lower since all drivers that are designed to be shelved as 2-ways can't get much lower. On an EV DH1A, you can go to 450 Hz. but that would be the bottom. JBL would be similar but you would need 4th or 8th order Linkwitz-Riley or Butterworth slope either way. You can measure, but your ears would be a better judge of what sounds best.

Personally, I would upgrade the woofers to higher BL and higher mass rolloff. But to save money, you PEQ up the K-33's or just go with the EVM 15L recommendation. DJK pointed out an old JBL as being roughly equal to the EVM but I don't recall. Maybe it's in my Quarter Pie thread. $$ play into this as much as your ears.

Edited by ClaudeJ1

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This issue about the crossover point is a tricky one.

We have already discussed where the JBL 2360 sounds best (avoiding the distortion when crossing too low). Others have chimed in about how high the woofers can go.

So you also need to know how well-behaved the the amplitude and phase spectra are near the candidate crossover region. Addionally you will need to know the distortion of the bass bin in this region. Finally, you should try and cross where the dispersion of the bass bin and the horn are comparable (certainly in the horizontal dimension). This last point is what most of DIYers overlook.

There are many pieces to this puzzle, but it can be solved. It is also the reason electronic crossovers make life easier.

Good luck,

-Tom

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Tom, before you run off. Could you give some insight on comparison between the JBL 2360 and EV hp 640, I could be wrong but I thought you have had a pair of the EV's as well(don't know if you actually compared the 2).

Guys I want to give you my thought process on these projects so you kind of get a feel what I am trying to accomplish. It all starts with what brought me here, and that is Klipsch Heritage. I have all ways be fine with the stock sound in from my Heresies and Cornwalls. But for my DIY theater room, bar area, I wanted to go above and beyond and try some wonderful products at there. After some time playing with this or that I have the same theory you can call it if you want, and that is if the basic parts inside the Cornwalls and Heresies sound this good to me why do I need to spend a tone of money on products that might not make that big of difference. One thing I have learned from that is sometimes you have to buy a higher end product to get it to do what you want.

After spending some time with my set up now (Jamborees with K-33's/ EV hp 640 with the Faital drivers). I wonder what the rave is about bigger horns such as the K402, and Dean said it best in another thread about the cost. So I look for the next best thing, I heard that the JBL's are the next best thing. So back to some of my thought process is, why not sell the higher end Faital drivers and purchase some decent drivers that would work on the JBL 2360's or 2365's. To be honest I was hoping my wife would buy me a pair of K402s for my birthday, but funds may not allow, so maybe I might get lucky with a pair of JBL 2360's.

I think Tom is right as well there are a lot of things DIYers such as myself over look. Kind of like the farmers mechanic vs the formula one racers mechanic. The farmers say it will work to get the job done, but the formula one racer needs to be precise to win.

But honestly, in the horn, I prefer the EV DH1A driver, which is available for about $90 on Ebay

Basically your saying the best bang for the buck driver, I guess for the price I could give a try on the EV horn to see how it sounds. Then decide from there.

Guys good stuff here and again thanks for all your help.

  • Like 1

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I sold my Faital drivers, and I am going all EVDH1A drivers for my 2360 horns, and EV horns.... I might even look for more JBL horns and just run JBL horns with EV drivers if I like the sound of them over the EV horns.

Edited by ellisr63

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Duder, yes I have played with both the EV HP640 and JBL 2360 (bith with the JBL 2446 driver). The can both sound good when crossed high enough. The EV is narrower in dispersion and will not control vertical dispersion until about 2000 Hz or so (the JBL controls to a lower frequency) and that will be part of the equation.

I ended up preferring the EV HP 640. In my application (two-way crossed at about 500 Hz). I ultimately ended up preferring the Klipsch K-510 (the little guy). Things changed when got the Klipsch K-402 (the big guy). That was the final winner overall. It has been a journey.....

Let me add: the issue about the horn is important, more important than the driver (if it has sufficient bandwidth). However the differences may be obscurred depending on the room (dispersion is less of an issue in a larger room, higher ceiling). It will also be obscurred if the crossovers are not set with care (and that can be tiresome task and does require measuremnt equipment).

Good luck,

-Tom

BTW, the EV HP 640 is a real bargain if money is tight. I have an extra pair if someone wants to try them.

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I sold my Faital drivers, and I am going all EVDH1A drivers for my 2360 horns, and EV horns.... I might even look for more JBL horns and just run JBL horns with EV drivers if I like the sound of them over the EV horns.

You need to give those a try and let me know what you think, however I will warn you if you set up your system you never get your room done as you will spend too much sitting around listening to music like me.

At those prices I may purchase one my self and give it a try.

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