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lodoc
08-25-2005, 01:09 PM
I've recently acquired a pair of 4612B's for my shop. They've also served duty 'borrowed' by my 19y/o for 2 grad parties and a bday party. He's an even bigger JBL fan now:applaud:

Members have suggested the Boston Acoustics PV series and components to build my own with a JBL spkr. The PV series don't appear to be very plentiful on the used market and for now I'd like plug and play. I really don't want to step into a bi-amped system for this application. An internally amped sub fed from the outputs on the 4612's would suit my immediate needs. There seem to be a myriad or brands, styles, speaker diameters and amplifier sizes to choose from on the used market. Is that because the folks buying them were disappointed and are now 'moving up'?

What subs have members successfully mated to the 4612's with good result?
What are the respectable brands with reasonable compatibility?

Chas
08-25-2005, 01:19 PM
You might look into Tannoy. I use a PS-350 (I am not 100% sure of the model number) in my HT with a pair of 4430's. 15" with a 350W amp built in. Works well for me. :)

GordonW
08-25-2005, 02:18 PM
The Tannoy PS-350 would certainly do the job! 15" woofer in a vented enclosure, with a 350w amp. VERY potent, good extension to 30 Hz and slightly below. Very good voicing, clean, tight, agile... all the good stuff.

Regards,
Gordon.

johnaec
08-25-2005, 10:02 PM
An internally amped sub fed from the outputs on the 4612's would suit my immediate needs.If you get something with an internal amp I'd highly recommend getting the signal from either a pre-amp or active crossover output, not from the same signal driving the 4612's, which would be speaker-level power, not a normal line-level for driving amps. That means you'd have to heavily pad the signal, plus you'd be getting all the inherent distortion and noise from the amp.

If you don't want to spend what it'd cost for factory units, I'd recommend getting raw JBL drivers, (extremely reasonable deals can be found on eBay), building your own cabinets, then putting plate amps from Parts Express in them - these usually have crossovers, (or at least low-pass filters), already built in, and you'd be ready to go. K140's or E140's would give very good response to below 40hz, and would be a perfect match for the 4612's, unless you're looking for something that goes flat to 20hz, etc., (low E on a bass guitar is about 41hz).

If you're interested in something like this, several members here could likely build you a set of utility cabinets for a very reasonable price. I might even consider it...:hmm:

John

lodoc
08-26-2005, 11:12 PM
I'd highly recommend getting the signal from either a pre-amp or active crossover output

Sounds like good advice. Not sure what an 'active crossover output' entails but I'll look it up. Am I to assume the output on the 4612's doesn't meet this criteria? I don't have much for outputs with my MC240 tube amp/ pre amp-tuner combination. But I can see more equipment in my music future. This hi-fi disease that has been in remission for quite a while is starting to recur.

Good used, build, built by others... I'm quite receptive. If anyone has existing componentry or is willing to assemble that which would suit my needs in exchange for small green pieces of paper please contact me. I'm just trying to do my homework so I've got a reasonable chance of obtaining something I'm happy with on the first go-round.

johnaec
08-26-2005, 11:38 PM
Not sure what an 'active crossover output' entails but I'll look it up.An active crossover is a unit that goes after your pre-amp and before the amps driving the 4612's and the subs. It sends mid and high frequencies to the amp running the 4612's and low frequencies to the amp running the subs.


Am I to assume the output on the 4612's doesn't meet this criteria?The 4612's don't have any output that's usable for driving anything electronic, like an amplifier. The electrical signals only go in to the 4612, not out. That's why you would use a crossover to separate the frequencies.

The other option I mentioned, using a "plate" amp, (a small power amp that usually mounts right into the back of the sub cabinet), with a "low-pass" filter, would probably be ideal for running the subs with the 4612's. That way you wouldn't even need a crossover between the different cabinets. You'd just run a full-range signal to the amps running the 4612's and the amps running the subs. The 4612's would reproduce everything they'e capable of, but only the low frequencies would be "passed" to the subs, since a "low-pass" filter only lets low frequencies through to the subs.

Here's a good example of an inexpensive plate amp from Parts Express: http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-794

This particular one has a 125 hz low-pass filter, which means everything above that would only be reproduced by the 4612's, which is exactly what you want. This one also has the inputs summed to mono output if desired. This means you'd only need one amp to run two subs, (or one), in mono, with the 4612's still being stereo. Or you could order two [possibly] less powerful amps if you want separate amps running each of two subs, for full stereo at the subs.

Here's a link to more plate amps at Parts Express: http://www.partsexpress.com/webpage.cfm?&Webpage_ID=3&DID=7&CAT_ID=43&ObjectGroup_ID=505&SO=2

John

lodoc
08-27-2005, 08:20 PM
we're getting a lot of information and directions going simultaneously, but here goes...

Re: active crossover:
I assume I'm buying equipment. what do I need as an interface btw my amp, and/or receiver to provide a signal to the subs?

Re: 4612B's output:
What is the application of the output connection on the 4612B's? If it cannot provide adequate signal to feed a sub "what do it do?"

I like the idea of a 'pass filter'. Is it adjustable? I'm not seeking the ultra-low freq. not even sure my eqip can reproduce it. just looking for something that reproduces 'bottom end' to some extent. btw- if the equipment is turned on to FM stereo, what is the frequence response it can reproduce? or as they say in the limbo vernacular : "how low can it go" ?

johnaec
08-27-2005, 09:59 PM
OK - the confusion lies in JBL's use of the term "Output" for the second jack on the 4612's. What this really is is simply a jack in parallel with the Input jack that only gets switched on when you plug something into the Input. It's just for sending the same power signal to another speaker, so that you don't have to send the cable to the second speaker, (if used), all the way back to the amp. A signal coming from this "output" is exactly the same as what's going into the Input, from the amp. This signal is high-power, i.e. whatever watts your amp is sending to the speaker. These high-power signals are inappropriate for driving another power amp, since signals that drive the inputs of most power amps are usually measured in the milliwatt level, (thousandths of a watt).

Since you've stated this is not for an ultra-high fidelity system, rather, you just want to get more lows than the 4612's have, I wouldn't even bother with an active crossover and separate power amps for the subs, as long as the amp driving the 4612's has sufficient power to run subs and 4612's, and can drive a 4 ohm load. I'd just pick up a couple K140 or E140 15" speakers, put them each in a cabinet about 4 cubic feet, port them to around 30 hz, and simply run them in parallel with the 4612's. The 4612's drop off naturally below 100 hz, but the 15" would be taking care of everything below that. For even better results, you could insert a passive low pass filter in the 15" circuit to keep anything above around 100hz out of the LF cabinet.

The next step up, and just about the ideal solution, is to use one, (mono LF), or two, (stereo LF), of the plate amps like those I previously linked to. Besides the built-in filters, etc., this means you also wouldn't have to worry about having to have an amp that can run at 4 ohms, which is what you get if you run the 4612's and subs off the same amp, without crossovers. It undoubtedly would play cleaner, too. The plate amps get their input signal from pre-amp outputs, (or tape monitor outputs on a receiver). The low-pass filters then remove all the mid and high frequencies from the signal before the plate amps drive the subs.

Either way you do it, using 15" speakers like I mentioned will give you really solid response to below 40 hz, which is as low as 95% of most popular music goes down to.

What you really need to do is come up with a budjet first - that will really determine how optimal you can go. Once you've decided what you're willing to spend, it will be much easier to narrow your options. You don't necessarily have to use JBL for the subs, but as nice as the 4612's are, it'd be a shame to compromise the sound by using something inferior for the low end. If you only want to spend $100 - $200, you probably won't be able to use JBL, but you could still get something together that might be satisfactory for the bass level you need. But if you can find some used JBL 15's at a good price on eBay, etc., ('probably $100 - $150 each), you could put together a system capable of outputting clean LF at the same levels the 4612's are capable of - literally, "live sound" levels. Cheap generic 15's would likely be OK for nominal listening levels, but probably really start to fag out at much more volume than that, and likely well before the 4612's start to fade...

John

johnaec
08-27-2005, 10:49 PM
Here's something interesting I just found on the local craigslist: http://www.craigslist.org/nby/ele/93855666.html

It's a mono JBL PSW-D115 15" subwoofer system, that comes with a built-in 350 watt amp that can be driven either by line level inputs or speaker level inputs. It's set up to act as a single mono sub in a stereo system. Here's the operating manual: http://manuals.harman.com/JBL/HOM/Owner%27s%20Manual/PSWD115%20om.pdf

I don't know how rugged these things are, and I'm sure it's not capable of the same volume levels K140's, E140's, and 4612's will attain, but it might do what you need. These also show up on eBay a lot.

John

Titanium Dome
08-28-2005, 03:32 AM
I don't know how rugged these things are, and I'm sure it's not capable of the same volume levels K140's, E140's, and 4612's will attain, but it might do what you need. These also show up on eBay a lot.

John

The entire PSW sub line was sometimes a bit weak on the QC, if you know what I mean. I've never recommended one, even to someone I was mad at. ;)

I have known one or two folks who had very good luck with them, however.

lodoc
08-28-2005, 11:35 AM
Thanks johneac, that helps a lot. Zilch gave me some input on subs in a prior post but my severe lack of audiophile expertise limited me. Reading all the various sub posts has given me some additional insight but some of the terminolgy is still like reading a foreign language.

I'm able to overcome budget restraints. Therefore I will aim for the 'ideal'. I will still seek out a temporary solution of a solid manufactured sub such as a tannoy that could serve portable duty or go with one my kids to college.

Regarding the ideal solution I'll seek out and eventually find JBL's. It would be unacceptable to me to mate other inferior speakers with the 4612's to save $. The 4 cu/ft box is somewhat intimidating. I would not consider a 4 cu/ft box to be very portable for parties, etc - hence perhaps an additional manufactured sub. I've got a large shop and I'm sure I can fit something of this magnitude inside it. Right now I've got a pair of Bozak B-200's up on shelves between car restoration parts. They must weigh over 100# each and measure approx 40x24x18 inches.

Reading prior posts it appears the size of the enclosure is critical. It does not appear I can use the bozak cabs mated with any of the recommended 15 in speakers. Some quick math estimating internal dimensions would put them in the 7cu/ft (small refigerator) size. Plus I would hesitate to guess what the internal pressures would do to the 40 y/o cabs. Any guesses out there?

When I undertake this project I'd like to select the optimal components. I realize everyones ear is different and there are subjective considerations but is it the consensus E140 or K140 is the desirable driver to mate with a plate amp and the 4 cu/ft cab? I have seen references to E145, K145 and the sub 1500's as quality components as well. I realize none of these are available except in the aftermarket and I'll have to start beating the bushes and watching the audio sales but that isn't that what makes the hobby fun?

Zilch
08-28-2005, 12:47 PM
To reiterate, Zilch would watch for 4625(B) Cabaret sub (or a pair of them) to go with 4612's.

They're 4 cuft. with E140 in them.

They have handles on the sides. :D

johnaec
08-28-2005, 01:52 PM
I realize everyones ear is different and there are subjective considerations but is it the consensus E140 or K140 is the desirable driver to mate with a plate amp and the 4 cu/ft cab? I have seen references to E145, K145 and the sub 1500's as quality components as well.The Sub1500 would sound best, but takes a ton of power to drive well, plus they're about as rare a speaker there is. The E/K145 would be next, (also somewhat rare), then the K/E140, (lots of them available).

Assuming the K/E140, if you wanted to build in stages, you could start out with just one cabinet and that single plate amp from Parts Express, which would probably be sufficient for most use. Then you could add a second cabinet when you want, and still run it off the original plate amp, but even though you'd have two sub cabs, it's still be mono if only one amp. Lastly, you could add a second amp so both subs would have their own amps for full stereo.

That amp looks just about ideal for your needs, since it has an adjustable low pass frequency, phase and level controls, can be summed for mono, and will use either speaker level or line level for the inputs. Even driving two speakers, one amp would still give them over 135 watts each. If you later added a second amp, each sub would then get 180 watts, (8 ohms).

A cabinet with external dimensions of about 21.5" x 28" x 15" would be about 4 cubic feet internally, and fit right under the 4612's. A system like this would be capable of very clean, full range, high level output, something you could even use for block parties, etc. That's definitely the way I would go. The cabinets would be functionally identical to the 4625's Zilch mentioned, with the plate amps being perfect for your application.

John