Jack or what have you sanity check

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Charles Jenkinson
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Jack or what have you sanity check

#1 Post by Charles Jenkinson »

Hello,
I've been perusing this website on and off for about a week, trying to work out a way forward for my amplification requirements. Let me first of all explain that I like good quality, efficient, powerful sound gear, and would spend the money, if I had it, to achieve such. I play bass guitar (5 string), piano-keyboard, and violin (both electric, and acoustic with in-board DPA miniature mic). I have 3 different amps at the moment, some of which do what they do 'ok', but are NOT top quality: My bass 'amp' is a 120w Hartke head (like in the kick back) with a home made 12” (celestion sidewinder) ported cab. For improving sound level and bottom end I've been augmenting that bass amp with a Carlsbro 90w (Cobra) combo keyboard amp with a 15” and separate tweeter in it. (A sound guy friend (with loads-of-money guitar type gear) recently looked at me, and with concern asked why I use two separate amps for bass :) ). Thirdly, I have a Behringer 120w stereo 'acoustic' amp with twin 8” cones - it has some convenient reverb settings on it – I use this last one when mic'ing the violin up.

Now, if money was no object, I'd go the AER route for the violin. A bass player friend has an Ashdown stack (4x10 on top, with a 15 on bottom) and to me that pretty well kicks and handles the low B just fine, but only when the 15 is coupled up. And for keys, well the Carlsbro is OK for that, but neither my current bass amp/s or violin amp give me great joy. (I do have a lexicon reverb unit so am not bothered about ditching the Behringer). So, that explains where I'm at at the moment. Now, for what I'm looking for: I had no idea I could potentially find something until I happened on BFM's website - Ideally, I'd like to be able to have one full range system that would replace the 3 amps I currently have, but would do the whole thing much better.

My current thinking is a pair of Jack 112's, plus a PA amp with different preamp units for bass and violin. My only reticence is will the pair of Jack 112's do the bottom B string justice or is there noticeable lack of umph due to Jack 112 frequency range? I think the bass duties is perhaps the most demanding aspect – not massively loud requirement but I do get gigs in any one of a 60's band, church acoustic rock type band or covers band and I like the bottom B to be there without rolling off. Violin and keys definitely needs the full range – whether they need the bottom B capability I don't know, but with the system I'd build they'd get it, if required. I've bought the Jack 112 plans, but before I get stuck into it, I'm looking for a sanity check before I commit further. Any ideas? (...I should also perhaps say that I'm half interested in building a small PA, which is a slight influence in going Jack, however, I don't want that to cloud this just for now – it needs to be right on the monitor / backline score which is the primary requirement). Any thoughts greatly appreciated.

Charles Jenkinson
Manchester, UK
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Harley
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Re: Jack or what have you sanity check

#2 Post by Harley »

I play 5 str bass in similar groups to you.

I use whatever is closest to the garage door at the time to take to a gig - 2 or 3 J110s, or 2 J112s or a J115.

Most gigs have bass going through FOH, some I have my cab/s as a backline.

I have no problem getting authority on my 5str bass throughout the range.

Your J112 x 2 solution will not disappoint.

Your other option would be an Omni12..but...Jacks do it for me if you want the easiest build.
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Gauss
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Re: Jack or what have you sanity check

#3 Post by Gauss »

Just a thought on the b-string: Whichever cab you build, it will go lower and louder than what you have been using and comparably-sized commercial products.
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The Big M
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Re: Jack or what have you sanity check

#4 Post by The Big M »

This is a very common question. Jack 12's are not difficult to build, are efficient,sound great and can be used for your keyboards. you won't be disappointed.

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Harley
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Re: Jack or what have you sanity check

#5 Post by Harley »

The Big M wrote:This is a very common question. Jack 12's are not difficult to build, are efficient,sound great and can be used for your keyboards. you won't be disappointed.
Agree - make two J112s though, not just one.
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Charles Jenkinson
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Re: Jack or what have you sanity check

#6 Post by Charles Jenkinson »

Thanks gents. All is confirming this is the way to go.

Whilst I'm here and the thread's live, I've looked but cannot find the answer to the following: I've been checking the UK supplier, CPC, for the Goldwood piezo's. People on Basschat.co.uk are saying the UK piezo is the MPT-016 - fair enough! BUT, it's freqeuncy response is from 3k upwards not the 2k of the J112 cross over, ...which even then needs a slope off down below, (correct?). I'm guessing this aspect of the system design is not a precise science in some aspects, but 1k out is quite a bit surely. Similarly, the Freq Response of Goldwood 1016's on the U.S. suppliers' website's seem to be 3k upwards or more (3.5k) in some cases. Is the 2k cross-over OK?

The MPT-016 from CPC ( http://cpc.farnell.com/_/mpt-016/piezo- ... dp/LS02367 ) has very good power levels. Is there any merit in doing a smaller melded array with less piezo's in it, say 8 per cab? What cross-over mod would be required to match it up? (Hand holding would be brilliant, but pointers in right direction would also be great)

Also, where is the schematic for the switchable cross-over (i.e. zero, half and full whack)?

Cheers,

Charles
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Charles Jenkinson
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Re: Jack or what have you sanity check

#7 Post by Charles Jenkinson »

Here's a U.S. Goldwood offering. 3.5kHz lowest Frequency response! Not near 2kHz cross-over frequency....? I don't know much about this subject - just going off the numbers.

http://www.parts-express.com/pe/showdet ... er=270-041
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Bill Fitzmaurice
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Re: Jack or what have you sanity check

#8 Post by Bill Fitzmaurice »

You cannot use the response of one tweeter to predict the response of a dozen, and beside that the high-pass filter changes response as well.

CPC sells two grades of 1016. The cheaper is shite, the more expensive (of course) corresponds to the Goldwood. Their price is outrageous; you can order them from Leland far cheaper even after shipping and the Queen's share.

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Charles Jenkinson
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Re: Jack or what have you sanity check

#9 Post by Charles Jenkinson »

Ok. So I'm 'off piste' by asking why the J112 cab has a 2kHz crossover frequency, when the piezo's lowest frequency response is 3kHz or higher?

Charles
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LelandCrooks
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Re: Jack or what have you sanity check

#10 Post by LelandCrooks »

Because the Goldwoods have good response to 2k. They're about the only ones that do. I've tested about everything I could get my hands on, and they're the only ones.
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Charles Jenkinson
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Re: Jack or what have you sanity check

#11 Post by Charles Jenkinson »

Thank you for that Leland.
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