Quick & Dirty 4430-Inspired Two-Ways Part II

[Zilch]

Zilch - what I'm curious about is why you're even experimenting with the 2032H? Or did I miss something?

Yeah, I'm not using 2032H, and don't intend to.

Here's what's going on: I wanted to try approaching this project from a different angle. Instead of pushing the HF response of a general-purpose mid driver, how about using a "real" tweeter like the new 2407H and pushing its low end to mate with the woofer? While a "similar" device (BMS 4540, 5/16" shorter "snoot" bottoms on some JBL horns,) has a manufacturer's recommended crossover frequency of 1.9 kHz, but can be used lower, apparently.


So, I look to what JBL is doing with 2407H, particularly in combination with my favorite PT waveguides, and find that JBL's using it at 1.3 kHz. I know from prior experience in this thread that's workable with extended-bass woofers like 2235H and LE14, but my first tries with it sounded bad, as confirmed by Toddalin coming by to listen. They're being pushed too low, perhaps.

Back to JBL's use of them as model. It's done with 24 dB/octave crossovers. I try that biamping with M552 active crossover. Much better, so I build the AM4212/00 crossover, with good result. That product uses 2023 as woofer, but I need 24 dB/octave on the LF as well, so I'm using AM4212's LF filter with LE14H-3 instead, is all, a mismatch. There are consequences, as outlined above. Not fatal, surely, and perhaps beneficial, even.

That's what we listened to last time you were here, using the inexpensive PT-F95 horns.

[Zilch]

Now this is a damned nice two-way... anything else is just a compromise.

Welcome back, Mr. Widget!

Yeah, those are SO beautiful, I wouldn't give a WHIT what they sounded like!

[Apologies to a forum canine....]

[Robh3606]

Hello Zilch
"how about using a "real" tweeter like the new 2407H and pushing its low end to mate with the woofer?"

That's a direction I would be careful going in. Pushing a tweeter lower is asking for increased distortion and break-up. You are also reducing it's power handling. A two way is not as simple as it sounds to get one to really work well. Pushing the driver bandwidths with a crossover in the 1k-2k range is asking for trouble. Your ear is sensitive in that region and having one or both drivers run short in the transition is not going to make your life any easier. You can try steeper slopes but you still need enough output from both in the crossover region or they won't blend right. I think you are better off using one of the 1" or 1.5" drivers that can get down below 1K with no issues. Can the wave guides get you down low enough??? That could be an issue as well.

Rob

[4313B]

Why did JBL design their most recent large format monitors (44xx, DMS-1) as two-way designs, do you suppose? It seems to me that these need to be wide bandwidth systems in order to fulfill their design goals.

I'm on the fence about the best approach myself. I'm thinking of going back to a two-way for simplicity's sake, but as you also said, they both have their pros and cons.

I can't possibly post on a public forum what JBL really thought of the DMS-1... (although I think Don actually did at one point).

As for the 4430 and 4435, please read David's article! - http://www.audioheritage.org/html/pr...bl/4430-35.htm

2, 3 or 4 way?
A lot of the systems that preceded the 4430/35 were 3 or even 4 way designs. Adding an 8” lower midrange would certainly improve power handling and also clean up the sound at high levels where the woofer’s excursion gets significant. Putting a crossover between the main horn and a small super tweeter type horn is problematic, though. The main horn usually had a lot of depth whereas a super tweeter (such as a 2207) would be considerably shorter. There would be several wavelengths of separation if they are both front mounted on the cabinet, leading to comb filtering in the crossover region. Pushing the supertweeter back to the point where the voice coil planes are aligned can remove the comb filtering although it isn’t always practical and doesn’t work over much of a vertical range of angles. If your main horn has the bandwidth then you are better off equalizing a bit than crossing over to a super tweeter at a high frequency. (This is just my opinion and I do realize that a lot of great JBL speakers were designed contrary to this.) - David Smith

Also, D.B. has said several times, the 2-ways are "nice" but once you add something like an 045Be to the top end it's a whole new ball game.

But, as always, build whatever you want.

[Zilch]

Giskard, so a bottom feeder like me might understand, what would be another word for "bandwidth"?

In this case, I believe the reference is to the available usable frequency response of the drivers employed, which, in current technology, is limited by the laws of physics as relates to their design.

In two-way systems, it's difficult to get the full audio spectrum covered without using one or both drivers in "compromised" response areas. Overcoming those comprmises is a major quest here; the improvements are incremental, but the trade-offs remain.

Fine. It's not world-class audiphile high-end, perhaps, but it's mightily satisfying listening nonetheless, as you have found with the ones you just built. And lotsa FUN, as well.

There are other trade-offs and compromises with three- and four-way systems, too. I ain't up to the challenge....

[4313B]

Zilch - what I'm curious about is why you're even experimenting with the 2023H?

He's not, he's experimenting with a network designed for the 2023H. It would be prudent to understand what the 2023H is doing so the design of the network becomes clear. It isn't suitable for an LE14H-1 or 2235H.

[4313B]

Giskard, so a bottom feeder like me might understand, what would be another word for "bandwidth"?

You're a lawyer!?

[Zilch]

Pushing the driver bandwidths with a crossover in the 1k-2k range is asking for trouble. Your ear is sensitive in that region and having one or both drivers run short in the transition is not going to make your life any easier.

Thanks, Rob. From the distortion specs Giskard just posted, it looks pretty safe with this driver. There is a bit of a peaking around 1 kHz, tho.

Note the SPL at 1 watt. Having enough with these isn't an issue. I've got 'em padded down an additional 9.5 dB from what the crossover delivers, as well.

As you observe, the other sonic quality issue is whether the LE14H-3 is playing nicely up to 1.3 kHz. From the curve for it, there's a nasty peak just above there. I'm trusting that the 24 dB/octave rolloff is mitigating this.

I need other listeners to assist in determing how they sound, tho, having been listening to so many different combinations here. Perhaps Mr. Widget will have a chance to drop by soon.

I think you are better off using one of the 1" or 1.5" drivers that can get down below 1K with no issues. Can the wave guides get you down low enough??? That could be an issue as well.

Indeed. If the way the 1.5" drivers play on the big 2352 horns is any indication, there are issues with the smaller waveguides not working well below 1 kHz that could benefit from some attention. I'll try steeper slopes for starters....

[Zilch]

Don C's castoff L55's (2 cuft.) get inverted with their feet removed, original port, crossover, and tweeter openings blocked off, and LE14A's rehabbed by Berkeley's Audivex installed. New 3" diameter x 7.25" rear exit port (original was 4", same length) retunes the cabinets from ~39 Hz to ~31 Hz per BB6P, and allows easy installation of 6" more damping insulation inside at the rear.

http://audioheritage.org/vbulletin/s...543&#post80543

RTA shows nearfield woofer performance at 6". I don't know how much of the port output is getting around to the front to be read, but it looks to be on design target.

Gotta LOVE them old LE14A's, yup....

EDIT: Easy enough to read the port, too. Bottom curve. Toddalin could sum them, I betcha....

[Zilch]

Inverting the cabinets gets the woofers more up to listening level. Crossed at ~1.2 kHz, LE14A is playing substantial midrange program material, and it needs to be up off the floor and closer to the horn, in my view.

NL200t3 crossover mates them with 2416H-1's on 2342 horns.

After padding down the HF 3 dB, AutoEQ says they're running +/- 2.5 dB "Outta the box."

LE14A sensitivity is 91.77 dB (calculated) according to BB6P. No clue what L200t3's 120t3 is. 95 dB in the range of interest, perhaps?

See similar NL200t3 crossover results per Hamilton and John W:

http://audioheritage.org/vbulletin/s...2&postcount=12

http://audioheritage.org/vbulletin/s...1&postcount=28

If a couple more builders get the same response, we'll work up a broad, shallow parallel notch filter to flatten ~4.5 - 10 kHz. To me, they sound a bit better (less "bright") with that hump EQ'd out.

And how DO they sound, actually? Well, VERY nice, I must say. 2 cuft. is BB6P's recommended "Optimum Hi-Fi" alignment for LE14A, and it's apparent in both the measured and listening performance. New 2342 Biradial horns are still available from JBL parts, and a variety of JBL thread-on drivers will mate with them using this simple crossover.

Alternatively, integrate the horn into a larger (taller) cabinet similar to L200t3 (bottom pics) for an "Extended Bass" alignment using LE14A:

http://audioheritage.org/vbulletin/s...2070#post82070

[Hamilton]

You're a lawyer!?

lol

Actually I was worse, much worse. For 23 years I was an auto mechanic...

[Zilch]

Question: All of the two-way designs I'm working with here rely on the midrange (800 - 1200 Hz) performance of extended-bass woofers.

Does using more damping to increase the virtual volume of the cabinet as I have done with the smaller boxes alter the performance in this region?

If so, for better, or worse?

[grumpy]

I would -expect- that damping on the rear wall (especially) would have the potential
to change the sound (dissipate midrange energy that could come back through the cone
or a large port opening)... if that's already been properly done, adding -more- stuffing
would seem likely to provide diminishing returns at the frequencies you're talking about.

Take out some stuffing and listen/measure . It would be interesting (to me, at least).

-grumpy

[toddalin]

EDIT: Easy enough to read the port, too. Bottom curve. Toddalin could sum them, I betcha....

Assuming one 3" diameter port and a 14" diameter woofer, columns are:
Freq (Hz)/measured cone referenced to 100 dB/measured port referenced to 100 dB/Relative Port Contribution (=Port Volume+10*LOG((1*(1.5^2*3.14159))/(7^2*3.14159))/Combined Frequency response.

…..Freq…..Cone…..Port…..Port%.....Resp
…..20…..38.0…..61.0.....47.6…..48.1
…..22…..38.0…..64.0…..50.6…..50.9
…..25…..37.5…..65.0…..51.6…..51.8
…..28…..40.0…..65.5…..52.1…..52.4
...31.5…..41.0…..66.5.....53.1…..53.4
....35…..46.0…..67.0…..53.6…..54.3
….40…..48.5…..68.0…..54.6…..55.6
…...43…..54.0…..67.0…..53.6…..56.8
…...50…..54.0…..66.5.....53.1…..56.6
…..55…..56.0…..65.0…..51.6…..57.4
…..63…..57.0…..64.5…..51.1…..58.0
…..70…..58.0…..63.0…..49.6…..58.6
…..80…..58.5…..60.0…..46.6…..58.8
…..88…..58.0…..59.0…..45.6…..58.2
…100…..58.5…..57.5…..44.1…..58.7
....110…..58.0…..55.0…..41.6…..58.1
…125…..58.5…..52.5…..39.1…..58.5
...142.....60.0…..51.5…..38.1…..60.0
….160…..59.5…..47.0…..33.6…..59.5
…178…..59.5…..49.5…..36.1…..59.5
...200…..60.0…..48.0…..34.6…..60.0

[Zilch]

Assuming one 3" diameter port and a 14" diameter woofer....

Down 6 dB at 34 Hz, 12 dB at 20 Hz.

From listening, these have plenty good bass, I affirm.

WAY cool, Todd. When CLIO gets here, I'll try ground plane and mic-in-cab for comparison....

[HEY! Where IS CLIO, anyways? ]