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Hello to all,
I recently , for some crazy reason decided,to have built a pair of speaker cabinets. They were completed in late Jan. They comprise JBL 123-A Twelve inch bass drivers powered by (for now) a Niles 1230 solid state power amp @30w per channel. The mids , and upper frequencies are handled by a pair of Klipsch 400 squawkers,and the Bob Crites upgraded high freq horn, as used in the Klipsch La Scala. They REALLY do look fantastic.
The Klipsch 400 sits on top of the bass cabinet, isolated, by a sandwich of sorbathane and walnut, at the front and a custom made bracket of machined aluminum, that allows the horn to be moved forward or backwards, and vertically by about 3.5 inches. Ok, here's the problem( two actually) No1: not enough Bass. The cabinet has a 1.75 inch thick front baffle. The rest is 1" MDF, and about 5 cu ft. with lots of acoustic material.(ultra touch acoustic batting, and acoustic foam). No2: No pinpoint imaging. The soundstage is kinda diffuse, is this typical of horns? P.s. The Klipsch horns are powered by a pair of Audio Research tube monoblocks (M-60, circa 1969)THANKS IN ADVANCE FOR ANY HELPFUL SUGGESTIONS.
Edits: 07/28/12Follow Ups:
There is something strange here.You have what seems to be an aftermarket / DIY / custom klipsch crossover copy. Looks like a B&K board or a copy of one (both use white sonicaps). B&K does custom Klipsch crossover replacements/upgrades.
So we need to know a few things:
QUESTION: If this is indeed a LaScala crossover, there could already be a high-pass filter in the midhorns crossover circuit in addition to a low-pass filter (if they even used one). After all, the LaScala was a three way and had a horn loaded woofer plus the two horns, right? And they would have HAD to put some high-pass circuitry on the midhorn else fry it or just make it sound terrible...
IF there is no passive high-pass on the midhorn, you are obviously (or should be) running a high-pass from the Urei for the horns. (THis is in addition to the low-pass you are running to the 123A's).
IF there *IS* a passive high-pass already there you need to do one of two things:
a) Remove it and use the Urei for the midhorn high-pass. (yikes)
b) Mirror the final acoustic response of the midhorn / midhorn filter combination. (This may or may not be do-able with the Urei)Once a flat response is achieved perform the correct baffle step compensation/equalization. This is NOT do-able with the Urei because you want an ~600hz crossover point and the baffle step frequency is ~300Hz. There is no way to increase the baffle step frequency because you are limited by bass driver diameter. (Even going with a super-thin 12" wide enclosure will only increase the BSC frequency to 380Hz.) Baffle step in this case will affect the overall level of the mid-horn and tweet horn. Only the woofer response will need a "shelving filter". THis can be done passively, even if you're using the Urei (as an add on eq circuit) or it can be done actively. The Urei is the limiting factor here. You *could* use the UREI and do BSC by using TWO stereo channels for the bass. One you would cross over at 600Hz (the upper woof) and the lower woof you would cross over at 380Hz. The relative levels between the upper/lower woofers can then be adjusted to suit the amount of BSC you want. So two woofs is indeed an option.
You need to answer those passive filter questions, or post sufficient detail about the horn's passive crossover so this can be examined.
Cheers,
Presto
Edits: 08/01/12 08/01/12 08/01/12 08/01/12
Hi Presto,
The high pass is for the tweeter. low CUT for the mid. It's more of a band pass (600-6000k)it's based on the Lascala xover with the Urie doing the grunt work with the JBLs. Hope this makes sense.
Thanks,
Cosmickat
I presume everyone noticed he said he had a 12" woofer?
My first thought was it might be too small for the application (relative to the other drivers/horns)
??
Do you have any on/off axis frequency response measurements of the individual drivers and how they sum acoustically?
Or did you use "manufacturers curves"?
Or none at all?
Yes Presto, I think you are getting to the crux of the matter. The truth is I did not measure anything before I built,DUH! mainly because the specs on this particular driver were not that easy to come by...but a friend already had them in a pair of butt ugly cabinets, I mean REALLY UGLY... but Oooh, the SOUND! It wasn't exactly hi-end, but it was very REAL, so I went ahead, and purchased a pair(123-A)on ebay, and had very solid well built cabinets made, and here we are. My only concern is did I make them too big, at around 5 cubic ft? and is this why I appear to be missing some low end frequency.
Even if "textbook" filters can get a lucky newbie "close"... you have zero baffle step compensation for these. Push them up against the wall (if they are not already) and you might find the bass situation improves.
Is your box ported or sealed? Did you use any T/S parameters to come up with this box size?
http://www.jblproservice.com/pdf/Thiele%20Small%20Parameters/Theile%20Parameters.pdf
That's where you can see the 123A T/S parameters for your speakers there. Of course, your drivers could have slightly different T/S parameters - although JBL is likely going to have decent drive-unit consistency.
Adding volume to a box is not that hard - add a chamber on the back or bottom. Reducing volume is also easy - fill the cabinet with a sealed internal void. It can be a square box made of wood - or even a fire log if you're on a budget.
When you're building a crossover for a PA woofer coupled with horns, you absolutely NEED to measure. Factory "specs" and factory response curves will not get you too far.
Cheers,
Presto
Presto, I did move the speakers closer to the wall, they were about 3' from the front wall, and after I moved them closer I think there might be a slight increase in bass frequency,but I will move them back again just to be sure. As far as the cabinet, yes they are sealed, and measure 38x16x22. there is a lower chamber filled with Ultratouch acoustic insulation, and acoustistuff from Madisound. I do have a question-what is Baffle step?
Finally, I am seriously thinking of putting a second 123-A below the existing speaker to increase bass response. I have posted a photo of the finished cabinet. Thanks!
Baffle step is a decrease in on-axis response for frequencies below a cut-off point determined by the width of the baffle. For example, your cabinets there, if they are about 15" wide, will have a baffle step frequency of about 300hz.
To correct for this, they use a technique called baffle step compensation. Since in the passive domain we can only cut and not boost, the trick is to attenuate all frequencies ABOVE the baffle step frequency in order to get a smooth response.
Since you're using an active crossover at 600Hz with no DSP capabilities, you have no baffle step compensation. If you're trying to 'compensate' by adding "more bass" at 600 down, then you're ultimately going to be creating a midbass hump between 300 and 600Hz. This of course assumes your crossover to the midhorn is summing flat in the first place...
The big question is: Does this midhorn have a passive low/high pass or just a low-pass filter. Aka, was it designed with a specific woofer in mind (like the LaScala bottom end)? Likely so... and if that is the case, you need to "tune" the crossover for the 123A, or in other words, you need to get the acoustic response of the woofer to work with the acoustic response of the midhorn so that the response sums flat. If there is already a high-pass filter in place on the midhorn, this means the crossover point, slope and "Q" (shape) of the lowpass on the woofer is anything but arbitrary. If this is the case you can experiment with the knobs on the Urei for 100 years and never get a flat response.
Cheers,
Presto
Presto, thank god I didn't try to build a jet propulsion engine, apparently my house would have been a pile of rubble by now:) But seriously, thank you for taking the time to share your amazing knowledge and expertise with me and all others who read this. I will try to make improvements that are practical, affordable and actually make the MUSIC MORE REAL.
Cheers,
Cosmickat
you'll need to take measurements. That'll take some research, but is really the best way to go about it.
If you want to simply leverage "known" response curves, get PCD (Jeff Bagby's software) and simulate- you'll need to take some steps like considering baffle step as Presto mentioned.
Bass is supposed to sound big. 6.5" is not a woofer size.
here is the result from my 1st speaker build. thanks for all your positive input.
Unless they're demagged- which can be an issue with these alnico woofers.
That said, of the 123A/2213/123A-3 I've tested, they've all been spot on to JBL's spec.
Bass is supposed to sound big. 6.5" is not a woofer size.
I would sell the Klipsch mid and HF parts and consider this driver/horn combo:
(Bob Crites can source these)
hi djk, I did post a reply further down this thread. but have also posted a photo of the speaker. I am seriously thinking of adding a second 123-A to the lower half of the cabinet...this would increase the bass significantly should it not?
your efficiency 3dB through most of the driver's range- and if in parallel, sensitivity will also rise 6dB. But, with a low DCR woofer like the 123A, you'd be facing a 3 ohm impedance or so through most of its operating range- got a beefy amp lined up?
Also, it will make raising the crossover point higher as I suggested elsewhere in this thread more of a questionable proposition- lobing concerns.
Bass is supposed to sound big. 6.5" is not a woofer size.
Ok Badman, so in layman's terms are you saying this would be a very good way to make this speaker system really kick ass! at the chance of repeating myself, there is a pic of the finished cabinet that I posted last night. The dimensions are 38x16x22. I can give you more details about the construction if needed. Thank you in advance.
BTW, I am definately going to buy a new solid state power amp, probably a Threshold S200 or S300.
The JBL 123A No=0.68%, or 90.33dB/W/1M, the K55V/K400 is 110dB/W/1M.
30W seems kind of small on the woofer, unless you listen exclusively to little-girl-with-guitar type music.
What kind of crossover do you have?
The K400 is kind of lame, but if you damp it well it will help. The Crites tweeter should be crossed at 4Khz or so, 18dB, and a low-pass should be used on the K55V, 12dB at 4Khz. The level of the tweeter will need to be boosted to match the mid, alternately the mid can be attenuated. With the tube amplifier the tweeter and its network may be connected to the 8Ω tap, and the mid and its network to the 4Ω tap, this will give the proper levels between the two.
The tweeter should be mounted in the same plane as the mid, and delay will need to be used on the woofer.
The crossover between the woofer and the mid, I would probably try about 800hz or so to start with.
Hi djk, not 2 big 2 jail, ha ha, I like that, almost as funny as you're "little girl with guitar music" comment, unless you consider, Muddy Waters, Jimi Hendrix, Keith Richards, little girls? not that I am oppossed to said girls with guitars, in fact have you had the privilege of listening to Esperanza Spauling, I believe she could possibly be the best acoustic Jazz bassist on the planet, and I do still listen to Nora jones, from time to time. But yes, 30W is a bit skimpy, thats why I'm eying a Threshold S 200.
The JBL123-As are crossed over at around 6k, using a Urie 535 electronic xover. the Klipsch are crossed over using the Crites upgraded passive crossover,with sonic caps, and custom made cables, by sain line systems (recently reviewed in Stereophile mag. i'm not a techie type, so I can't get too technical. I did have the Klipsch 400s sandblasted, then all the voids were filled with bondo, then sanded. The inside was hand sanded to a very, very smooth finish(not repainted) and the exterior was spray painted to match the bare aluminum on the inside. they are well damped, and there is no "honk" that I or anyone of my hi fi buddies have commented on, but maybe the power amp dept could do with beefing up a little. but overall they are quite close to being "there" I will try to post some pics. Thanks for you helpful suggestions.
It's a lovely wideband driver but 6k is REALLY pushing it. And 100WPC should be requisite for them, though 50WRMS is what they're rated for (Unless it's a serious 50WPC).
You have a VERY narrow dispersion in the band key to imaging- 1k-6k, since it's laserbeam from the driver by 2k
I'd start with the crossover and go from there.
Bass is supposed to sound big. 6.5" is not a woofer size.
Hi badman, your probably right on both counts. The crossover point is easily remedied though, with the electronic xover, and I did start at the recomended 4k, but as you say the123A has a lot of sweet music in the 4.5-6k range, and I'm thinking 100w per channel at least for more bass. Do you happen to know min/max cabinet size for this driver? I've heard 3 cubic ft in a sealed box is a winner, but I have around 5 cu ft...is the cab too big for this driver, and is this the main reason of not enough bass?
Which you can do just by loading some bricks into the existing cabinet. You'll have more midbass at the expense of the deepest stuff- which is probably a good tradeoff.
Bass is supposed to sound big. 6.5" is not a woofer size.
badman, thanks I will spend some google time looking into ALL this GOOD STUFF!
Cheers,
Cosmickcat
Hi badman, just to clarify, The 123-As are going through the Urie 535 electronic xover at around 450-600Hz NOT 6000K sorry my mistake.
But now you're too low- asking too much from the horn on the bottom end most likely, and you'll get a better directivity match around 1200Hz or so.
Take a little google time with "econowave" and you'll see some utilization of the 123a in 2 way horn systems, and some idea of directivity matching.
Bass is supposed to sound big. 6.5" is not a woofer size.
Them toed in? Even horn speakers need "some toe in"! Either that or maybe something in the crossovers is causing them to be out of phase? Doe you have them hooked up correctly (- to -/+ to +)?
Hi tube Tom, yes have them toed in,have tried different angles, and always seem to come back to the same place! I have also checked for polarity, by reversing the speaker cable. All of this was followed through carefully when the Cardas binding posts were installed.
I think my room is a big drawback...old house, creaky wood floors, lots of character, you get the picture. Just hoping something might come to mind...cause you know sometimes the smallest thing can make a big difference in the crazy world of hi fi. thank you for your suggestions :)
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