Phil Starr

[quote name='LawrenceH' post='969678' date='Sep 27 2010, 04:59 PM']I certainly wanted the piezos to sound good. But to me at least they really didn't and I consequently feel a bit sceptical about other people's glowing reports. Maybe some people just don't hear what I hear, or maybe there's some gross distortion using comp drivers that I'm strangely immune to (other than the usual harshness at the lower end of their useable frequency response). It wasn't a subtle difference though.

We fitted the not-really-a-true-phase-plug as recommended in the Jack plans and found the performance difference negligible. I'm interested to know if you'd think a more complex design would lead to a real-world noticeable improvement.[/quote]
Hope Gilmour doesn't mind us taking over his thread like this, The problem the phase plug solves is that there are different path lengths in the cavity between the speaker and the mouth of the horn and you get destructive interference at the higher frequencies which limits the top end performance of the horn. in this case the mid range frequencies you describe as missing. Ideally I'd try to make a cross shaped piece extending back towards the cone but obviously clearing it and then extend the phase plate forwards to reduce cancellation across the mouth. If this bridged the gap between the 10" speakers and the horns then yes, it should make a real world difference. I haven't tried this though.

Just as an added point I've noticed that the quoted specs for these size of piezos vary from a bottom frequency of 2kHz to 4.5kHz so I guess they are not all the same.

[quote name='LawrenceH' post='969448' date='Sep 27 2010, 01:40 PM']Hi Phil,
I thought I'd chip in here as my father and I built a set of 4 Jack 110s using Deltalite IIs and the piezo arrays (2 with 12 piezso, 2 with 6, piezos imported from Speaker Hardware in the States). We initially tried them on bass without piezos and found the sound to be very good, smooth and with excellent clarity despite the lack of tweeters.
However.
On PA duties, the piezo arrays to my ears (and my dad's, a relatively experienced sound engineer) sound dreadful, and we spent a long time trying to EQ them and fiddling around with crossover frequencies. The Jack 10s were very boxy sounding overall, and the gap between the speaker cut-off and the piezos kicking in properly (from memory, somewhere like 1-2k is much more audible than the graphs led me to think it would be, and we found impossible to restore with EQ in a way that was satisfactory. I tried a bit of modelling in hornresp using the jack 10 design, and found it behaved pretty similarly to what was predicted, the cut-off is just too low for those piezos. Additionally, overall the mid/upper mid-range response sounded flat and lifeless yet somehow also harsh. Above 2-2.5k it's there, but it's not nice. And yes, although everyone on the BFM site insisted the wiring must be incorrect, we double and triple-checked and basically lots of tweeters together pretty much sounded to us like a phasey version of one on its own. I A/B'ed against an Eminence tweeter (NSD2005 I think? OEM in Yamaha PAs) coupled to a horn and that was significantly better especially lower down, although it's still far from perfect. Much greater clarity across the usable frequency range.

The Jack 10s are very loud though and as I said they did sound bizarrely nice on bass guitar. I actually think they'd work well as part of a 3-way design (although the lower-mid hump does make them very boxy so you'd really want to cross at about 800 max) but that sort of defeats the point of them. BFM insisted EQ was essential for any PA rig, I have to say I don't agree with that philosophy for little portable rigs but it is so for the Jacks as their untweaked response is very uneven indeed. But our experiences illustrated the point quite nicely that there's a lot more to speakers than flat frequency response. This works in the Jack's favour across some parts of the frequency range (I liked the upper-bass/low-mid clarity) but not others (anything 800-ish up).

My 2p, take or leave it! Others say they're very happy with theirs and good for them, this is just our experience although I will say we did try and exhaust possbilities of faults/errors on our part before making up our minds.[/quote]
wow, thanks a lot. The jacks are just an undersized conical horn with a reflex port, a nice design with some neat bits of improvisation but for me the phase plug needs to intrude into the cone area to avoid cancellation at high frequencies and the horn is a long way short of optimal. I'm open minded however I used to build my version of a horn/reflex hybrid years back for a number of bands and they always sounded sweet I was kind of expecting the sorts of things you are describing from the Jack though. That Yamaha is the horn I'm using for A/B 'ing with piezo's at the moment. The nearest I've got is with a 1" piezo driver with a big moulded horn which sounds pretty good but won't quite handle the power. Using multiple piezo's gives the phasing problems you describe. I'd love to use the piezo's because they are electrically more robust than the coil versions and I hate expensive crossovers. I know I'm going to end up with 'proper ' horns and an electronic crossover in my heart but I just want to try a couple more experiments first.

[quote name='gilmour' post='965866' date='Sep 23 2010, 05:40 PM']My biggest concern is still the Piezo array and it's fragility, once it's all glued together an screwed to the wood it's certainly a lot stronger, but still feel like it needs some extra bracing somewhere - I even used solid copper to wire the piezos, definitely overkill for sound, but added a bit of strength.

I'm surprised but just how loud these are as PA cabs, for most gigs I'm doing they will actually be overkill, which I hadn't realised at the start, but two of these, running at 4ohms each, is a 1k rig! I don't need that for 80 people at a wedding lol. Anyway because of his they can cope with just about anything I throw at them, which is nice.[/quote]
I'm really interested in how you find these as PA speakers. What do you put through them? How are they on vocals? I've never managed to squeeze the sound I want out of piezos but they are working hard in my designs. The array means you are working each one much less but there are technical problems when high frequencies come from multiple sources spaced like these. The test of course is what they sound like and vocals are very revealing.

I guess I ought to check up on your gig diary next time I come up to Reading.

If it is not too late the dome can simply be stuck back down with some latex based adhesive like Copydex. Ive done this lots and so far it works every time.

You could try stuffing then with rolled up socks, seriously. Make sure you can pull them out though. You should get deeper cleaner bass but less of it.Most of the sound will be unaffected so don't expect dramatic changes

Guess you are still having computer trouble bu it would be lovely to hear how your speakers are sounding

Cheers

[quote name='ironside1966' post='961310' date='Sep 19 2010, 04:57 PM']In the past I have done quite a bit of work where the band leader wanted to keep the volume as low as possible and its great, you can really hear what’s going off. Sometimes it’s nice to listen how the harmony works, hear the subtle arrangements and tasteful little runs or riffs , it’s nice to work with great vocals where the singers not to screaming to get over the band.
I know that groove and feel are important and you don’t have to lose it because you are quiet.
Any musician in a group or ensemble is only as good as their contribution to the said group or ensemble if the musician brings the music down by playing too loud or over playing then I question the ability or musicality of the said musician.[/quote]
I'm pretty much in sympathy with what you say and I love the sound of drums but not all drummers are good enough to control the volume and keep the same level of attack, just as I'm not a particularly good bass player. Should we just not play and let down our singer who is rather good? I'm just saying that it is the overall sound of the band that matters and not just that of one musician,

The devil in me wants to ask what you think of the sound of an upright rather than an electric bass or even an electric guitar rather than an acoustic?

Just did a first gig with a new drummer who uses an electronic kit. It doesn't sound as dynamic as skins but the band sounded a whole lot better overall. In fact modify that statement about sounding dynamic, the kicks really came through and we really locked in (me bassist) when things picked up later in the set. In addition our singer just took off. With a lower on stage volume and no bleed through on the vocal mics. she could really hear her own voice and there was so much more nuance to her singing.

A drummer with a volume control... bliss.

Ashdown have probably the most helpful attitude around so email them or ring them for advice.

If it is happening with both basses then it isnt that. Try swapping for a new jack lead. Then try a different head or your head with a different speaker. It could be an earthing issue so try a differnt kettle lead and also try plugging it into another mains socket as it could be the house wiring.

I borrowed one of these from a friend a couple of years ago and they do sound good. The Black Widow speakers sound really fast for 15's and you can still buy the replacement cones if they burn out. The only problem is that the cabs aren't tuned properly. I built my own case for a Black widow and it tightened up the bass dramatically. I also used to put the kick drum throug the spare channel on the amp from time to time.

The Fane sovereign 12-200 would match your cab and give you an old school thump. The Eminence beta's would also work OK and have a bit of midrange hump which might help them cut through the mix. If you want a gorgeous sound then try the Beyma SM212 bur these will set you back £300 for four. I have two and they really sound good with bass.

The good news is that if this is a closed box then it is a lot less critical and you can probably get away with a wide range of speakers. There are definitely good and bad choices and the matching will affect your sound but only at the bottom end. You won't damage your speakers by mismatching them.

Basically each speaker needs to be matched with a certain volume of air. If the volume of air is too big and heavy then the bass will be weak and will tail off gradually from quite high up. If the box is small then this raises the resonant frequency and the bass will be boosted around this frequency and then cut off quite quickly. Somewhere in between is the ideal match where the frequency response is flat down to as low as that speaker will go and then there is a gradual and predictable cut out. Many designs for musical instruments exploit the bass hump of a small cab to make the cab sound bassier which gives a nice thump to the bass.

If you want a recommendation for this cab then you need to tell us a little more. Do you want to replace all the speakers or just the broken one? What sort of sound do you want? What is your budget?

A 4x12 for bass is unusual, are you sure it is a bass cab?

Bon chance!

[quote name='stevie' post='828509' date='May 5 2010, 03:11 PM']I’m not really a great believer in optimum cab sizes. Ported cabs for bass guitar are quite flexible in terms of what works. For example, all the speakers I listed will work quite nicely in a 35-litre cab although, as you mention, the Fane is more comfortable in a smaller cab than the pressed steel Celestions.

In response to your question, I haven’t got a lot of personal experience of the Chinese Celestions. I’ve tried a couple (not the bass guitar ones), and they were better than I expected - certainly better than the older Celestion PA speakers I have tried. Other people I know have been impressed with them. Whoever is designing their drivers is very capable. I’m impressed, for example, with the way the top end is very controlled – unlike many drivers which go into uncontrollable spasms before they roll off.

I understand what you mean about the high resonant frequencies. 73Hz does sound too high, although this is largely a factor of the suspension stiffness. Also, the Qts of this driver is relatively high, which compensates. You could drop the resonant frequency by fitting a softer suspension, but then Qts would drop, VAS would rise and you’d end up with exactly the same performance. I modelled the two pressed steel chassi Celestions, one with 73Hz and the other with 64Hz resonant frequency and their low frequency performance was identical.

If I were choosing from the three pressed steel drivers based on their parameters, I’d go for the Fane as you did because the heavier cone helps it produce more bottom end. Oddly enough, the parameters of the Celestion NTR driver are very close to those of the Fane. Although the NTR is a very expensive option, it is probably in the same class as B&C, 18Sound and Beyma.

4mm coil overhang is quite acceptable for a 10 - even the JBL 2226 only has 5.5mm of physical overhang. If it were a B&C or an Eminence, the spec sheet would say 8mm xmax.

What do you think the problem is with the top end of the Fane, Phil? Have you measured it?[/quote]
Hi Stevie, I lost track of this thread over the Summer what with gigs and holidays. Yeah I also modelled the two Celestions. I haven't got round to measuring the Fane yet. In the end I couldn't make my mind up between the Fane 10-275 and the 10-125 so I bought two of each to experiment with and built them into a temporary 4x10 but with a partitioned cab and wired as two 2x10's. The Fane data shows a more extended top end for the lighter coned 10-125 with a smoother break up pattern and this is the speaker Fane recommend for bass guitar but because I have come from a hi fi direction I was attracted to the cleaner bass promised by the low Q and bigger magnet of the 10-275.

So, I effectively have two 2x10's with the 10-125's in undersized cabs tuned to 55Hz and the 10-275's in optimum cabs (SBB4). the only testing I've done so far is to play bass through them.

Firstly I'd confirm what you say about optimum cab size. The modelling on the undersized cab shows a real hump of just under 3dB (from memory) but the bass sound when playing isn't dramatically different from the 10-275's. Certainly much less than that caused by tweaking the eq or changing strings

The 10-275's do give a more clean and controlled bass, but again it isn't dramatic. I doubt that it would be noticeable once the band get playing around me. They also roll off at about 3000Hz and their is no dramatic resonance peak unlike the Celestions or equivalent Eminence speakers so they don't sound particularly lively and I play with my 15" Peavey driven cab on top to pick myself out of the mix the 10-275's are very bassy and the Peavey gives a lot more mids. Finally they weigh a ton and a 4x10 with these in will be a hell of a lift. They do make for a nice small box though.

I'm not the worlds greatest bassist so the speakers haven't had much of a workout yet. I'm going to do some measurements and try out an optimum sized 2x10 with the 10-125's which sound better than I expected in the undersized cabs. I'm also intending trying the 10-275's in a 2x10 on their own to see if they are up to the job as a compact cab. My wife is going to kill me.

[quote name='gilmour' post='942368' date='Sep 1 2010, 05:10 PM']Sadly no - the insurance company are really dragging their heels, it looks like the whole thing will have to be replaced as not only is the screen damaged but the CD drive is knackered and the hard drive corrupt

So I only have intermittent internet access.[/quote]
Bad luck

Interesting, I've got the same sort of problem with my Cort. I spent a lot of time fiddling with pup heights and eq settings but could only mask the problem. I mainly use Rotosound 66's and when these are new the problem isn't so pronounced although I am still aware of it whatever the strings. I've even thought about upgrading the pups but without the promise of a cure it seems a lot to spend on what is basically a cheap bass. Is this a common problem with P-bass pickups?

Got that laptop fixed yet? Hope so, I can't be the only one looking forward to the next post.

I used to build custom cabs.

Materials costs for a cab would be £30-£50 for a basic finish + about 6 hours labour for a one off cab. All very approximate as it depends upon the cab design and to a lesser extent how much expensive gear you have to speed up the build. The box is going to cost £100+ to build.

A cheap Celestion or Fane driver will be £30-40ish up to £100 for a Precision Devices driver of someting else a bit better for a 10" unit.

Add in the time it takes to market, talk to the customer, deliver,test, provide after-sales support etc. Also allow for the costs of renting and equipping a workshop and it is pretty difficult to produce a speaker for under £200. Add in the costs of shipping and the profit margins of the retailers/wholesalers and/or importers and you get a retail price of £400.

Mass production in China can cut the costs to half of these prices but such speakers are usually engineered to keep costs low with a compromise in performance. Having said that the engineering is usually well thought out and great value for money.

Sadly very few people in this business from the musicians upwards make good money, we all do it for love first and sometimes manage to scratch out a living.

I don't think this is what you should be looking at for this function unless you think you will want to use it with a full band at some future date. Something like this [url="http://www.amazon.co.uk/Yamaha-Stagepas-300-P-A-System/dp/B000RW037G"]http://www.amazon.co.uk/Yamaha-Stagepas-30...m/dp/B000RW037G[/url] is much better suited. It sounds great with vocals and acoustic instruments and is amazingly light and portable offers you all the mixing you need and reverb on vocals if you want it and is really simple to use.

The only minuses are that it won't go to rock band levels and the stand mount points (you'll need stands too) are non standard so you'll have to buy adaptors. We have one which we use for a full band in rehearsal and as our monitors at gigs. You'll have some quality kit and can then spend whats left on decent mic's

I'm following this with interest mainly because I want to see what you all think of the piezo arrays. I love the simplicity of piezos and they sound ok to me except that the sound output is ultimately limited as is their power handling. The array gets around this but I've always suspected that with the spacing of the drivers corresponding to the wavelengths of sound they are reproducing there will be serious interference problems. It's a problem with all line source arrays. I guess in the end I will have to try it out myself but with Gilmour building these ...

Another solution I've tried is these

[url="http://www.bluearan.co.uk/index.php?id=SKT902490&browsemode=category"]http://www.bluearan.co.uk/index.php?id=SKT...semode=category[/url]

Which screw in to a standard horn flare

[url="http://www.bluearan.co.uk/index.php?id=SKT902384&browsemode=category"]http://www.bluearan.co.uk/index.php?id=SKT...semode=category[/url]

I've tried these with some PA speakers I built and for the price (£10ish) they are remarkable. They claim 105dB/W though I measured them (very roughly) at 103. I used series caps to reduce the voltage across them to use them with a 500W amp and to match them with the bass drivers and of course tried them with my bass. Bloody fantastic if you like a DI'd sound.

You mention pokey and hi-fi. If you mean a flat sound then why not use a PA speaker. They usually handle bass pretty well and often go lower than a bass cab and being produced in large numbers they work out pretty good value for money. I use a 12+horn PA speaker for smaller gigs and if I'm honest it sounds much nicer than my 4x10 + 15. If you go for an active version then the drive units have built in protection so you won't need to worry about blowing anything.

Most bands have some sort of PA so its pretty easy to try this out without spending anything up front.

[quote name='Dom in Somerset' post='898088' date='Jul 18 2010, 02:50 PM']I'm about to order the electrics for my latest project, I know nothing about the subject, happy to follow a wiring diagram.
CH guitars do wiring kits for certain basses and guitars, they do two for Jazz bass, one with a ceramic capacitor one with poly- what difference does it make (if any?)[/quote]

going back to the original question I really don't think it will make an audible difference. In high end hi fi you wouldn't use a ceramic but you really aren't going to hear a difference through a bass amp/speaker. I recommended poly because I've found them more reliable.


[quote name='stevie' post='910572' date='Jul 30 2010, 07:36 PM']Despite thousands of unsubstantiated claims to the contrary all over the internet, yes. The driver itself changes quite a lot, but its real-life performance in a box doesn't.[/quote]

Actually this isn't true. The sound does change and you can hear the changes, they can be subtle or quite dramatic depending upon the speaker in question. Its not all down to Thiele/Small small signal changes either. Stevie is right about changes to Vas and Q being to an extent self cancelling and this is discussed in Bullock on Boxes (ISBN 0-9624191-5-X). These changes affect the bass response a little.

More important i suspect is the changes in the cone itself which will soften with time becoming less rigid. It will flex more and resonances will change which will change the upper frequencies.

Having said that we are all discussing angels dancing on the heads of pins. In reality we all use speakers for more than a few hours so they all get 'broken in' eventually and one person's dramatic change is another's subtle difference. Our hearing also makes fools of us all at times. I think where Stevie got us all so excited was by giving us actual data, a rare commodity on the internet. When I get time I'm going to have another look but for now I really ought to get some practice done.

Great debate guys, I dread to think what it says about bass players.

These problems are caused mainly by resonances. Different rooms and structures will have resonances that emphasize different notes that will in turn be picked up by a mic. These resonances will be dependant upon the wavelength of the sound and simply moving the drums, bass stack or mic may well sort out the problem. Obviously a bouncy stage will also resonate.

If you get this problem again then try setting it up so that the resonance is just starting and then try moving things around a little. You should be able to shift the 'hot spot' so it doesn't coincide with the mic in question. You could also try using the tone controls to tune the problem out.

If you use a combo then try using a stand to point it at your ears. You get better monitoring and the stand will help decouple the amp from the stage.

[quote name='stevie' post='909493' date='Jul 29 2010, 05:55 PM']Here is some data on an Eminence Kappalite 3012LF, with measurements before and after running in. There are a few minor discrepancies, but this was not designed as a scientific exercise: I was simply checking the parameters against the manufacturer's figures. The parameters on the left are for the new driver; the ones on the right are the same driver, but run in.

The interesting information is on the right - a simulation of how they perform in an identical box.

I can't say this is conclusive and absolute, but it's certainly repeatable by anyone who wants to do so.[/quote]
Love the thread and this is interesting data. The figures show the sort of increase in compliance you would expect after a breaking in period though why Qes would change beats me.

The cone and surround of high power speakers are usually made of plant fibres (in turn made of lignin and hemicelluloses) and this is normally treated with some sort of latex or plastic. The spider is usually some sort of treated woven cloth. The fibres vary in their strength and some will break when subjected to repeated vibrations. The weaker ones will break early on and the process will continue throughout the life of the speaker until the surround (usually) fails. In addition you would expect there to be gradual chemical changes in the polymers used. All this means that there will be gradual changes in the mechanical characteristics of both the suspension and cone of the speaker throughout its life. This will be most rapid early in the life of the speaker which is what causes the breaking in period.

I've noticed that the impedance/frequency curve of a speaker changes over time to the extent that I won't tune a reflex port until a speaker has had a period of use and you can definitely hear the changes in response.

Love my Peavey micro bass. look for one secondhand.