Phil Starr

there you are then EA claim that both sets of ideas are true at the same time and their cabs have all the advantages. [url="http://www.eaamps.com/index.php?p=translines&m=tech"]http://www.eaamps.com/index.php?p=translines&m=tech[/url] Mind you, there is no way this is a transmission line. the line itself has to have the cross sectional area of the cone at the speaker end to avoid pressure changes and as Bill says is 1/4 wavelength so that's 6 cu ft packed inside a 2 cu ft box. Truly amazing! And 103dB sensitivity at 45-12,000 Hz with no excursion limiting at 200W, obviously the laws of mere physics no longer apply at EA. [url="http://www.eaamps.com/index.php?p=wizzym&m=products"]http://www.eaamps.com/index.php?p=wizzym&m=products[/url] These may be great speakers but I wish people would be honest

[quote name='Bill Fitzmaurice' post='1219340' date='May 3 2011, 11:17 PM']Transmission lines are 1/4 wavelength resonant pipes. The 1/4 wavelength resonant frequency coming out of the terminus acts much like the port in a bass reflex. The line is stuffed with damping material to suppress the harmonics of the pipe frequency. The advantage to a TL is that below the pipe frequency response rolls off at 12dB/octave, like a sealed cab, rather than the 24dB/octave of a bass reflex, so you get sealed cab 'tightness' with reflex efficiency. The downside is that they need that 1/4 wavelength pipe, which is 5.7 feet for 50 Hz, 7 feet for 40Hz. They're just too big to be practical for electric bass.[/quote] I said there was controversy. Strictly speaking what Bill is describing isn't a true transmission line, but it is the only practical version you'll see today and the one the computer models work on. The original transmission line was just as I described an attempt to absorb all the rear radiation with a zero resistance at the far end of the line to prevent pressure being reflected back along the line where it would arrive out of phase with the speaker cone. Lots of magic went into stuffing the line to achieve this. In the 70's people questioned this and said that the cab acted as a reflex cab in exactly the way Bill describes. Supporters of the original theory will point out, quite correctly, that measurement of the output of the port/termination of the line is much lower than you would expect from a reflex port. The computer models don't predict measured bass response particularly well for these speakers. I'm agnostic about this and ultimately a bit sceptical about the claims for transmission lines. there are some nice sounding TL's in the hi fi sphere but I reckon a lot of this is due to a well behaved impedance load and the massive internal cabinetry which cuts down on a lot of cabinet resonance. In any case Bill is right, there is no real place for TL's in electric bass cabs.

Hi Gus, great question, or rather questions. It should keep us going for months. the easiest one to answer is your transmission line question. Although there are some technical controversies over these the whole point is to absorb the rear pressure and to stop it reflecting back to the speaker so you lose all the energy from the rear of the speaker and you have a decent mass of air in the line. Transmission lines promise lower resonance and smooth low end response with good transients but low efficiency. Older speakers (I used to design speaker cabs back in the early 70's) tended to have limited power handling due to inferior materials available for the voice coil assembly and the expense of amplifier watts. This meant they were designed to be as efficient as possible by packing a lot of voice coil inside as powerful a magnet as you could afford. The cost of this is that excursion (Xmax) was usually very limited. Speakers weren't really designed for bass specifically anyway most of the time. Excursion limiting wasn't a big issue if you were limited by amp power. Thiele's research wasn't widely known about either, and a lot of design was hit and miss, so a lot of speakers were put in cabs that we now recognise as too small resulting in a marked bass hump in the frequency response which made them seem loud and warm sounding. I suspect this could be the reason for the difference between your cabs.

[quote name='Arrakis' post='1215856' date='Apr 30 2011, 02:58 PM']Ok thanks for the replies. Its going to used in a supportive role rather than a lead sound playing detuned stoner/doom pushing out lots of fuzz/drive going to be running in conjunction with a 2x15, the 2x15s dont especially sound great at pushing out the fuzz. Now I have had a very mixed response about this on various forums including this one, theyre going in a Matamp Retro 4x12, now Ive phoned the factory and their view is that it should be fine to swap out the guitar speakers for bass drivers, now before people start saying thats wrong I have also spoken with someone whos done it with good results so my point to this thread is to basically find out what drivers on the market are good for specific styles/sounds etc[/quote] [quote name='voxpop' post='1215866' date='Apr 30 2011, 03:08 PM']Now this could be utter bull, but from my limited experience of swapping out speaker Celestions have a rough rock type sound and Eminence have a cleaner slightly brighter sound. (possibly)[/quote] This kind of illustrates the problems designers have. We don't have a lot of words to describe sounds and those we do are ambiguous. For me fuzz is a certain type of harmonic distortion as created by a fuzz box but it could be any sound you think of as fuzzy. It is relatively easy to work out why a musician describes a sound the way they do after the fact. For example the Eminences sounding 'brighter and cleaner' is largely due to the big peak in frequency response at around 2-3kHz that many of their speakers display and this in turn is caused by the way the cone behaves under breakup. It is much harder to work the other way and create a sound from a verbal description using your knowledge of the science. Much of what bass players think of as 'musical' in a cab is often actually down to a distortion of the sound their guitar makes. Just swapping your guitar speakers for bass speakers will 'work' as the guys at Matamp are telling you in the sense that they will make a sound and you can put lots of bass through them. It may be that they sound how you want or they may not. How the bottom octaves sound depends upon matching the cab and the speakers, if your mate had the same cab as you and you put in the same speakers as him then you should get the same result and you don't need us to help. If you put any other speakers in or your cab is a different size or shape then the results are unpredictable without much more information. The bass could be very thin or very overblown and resonant depending how your speakers match. It sounds as if you really want a lot more upper mids/top to me and the eminence Delta's and Basslites both have peaks in this area so might give the sound you want. I don't know if they will work well in your cab or if they will go with your other speakers. I hope you realise people aren't being awkward. It is just about impossible for anyone to say 'this is the speaker you want' because there are too many variables and none of us wants to be responsible for you spending a lot of money and not getting the sound you want. If you want to go ahead and take a gamble then you might be lucky, you can always put the guitar speakers back and sell the new ones on ebay if it doesn't work out. You might be better tracking down Alex and listening to some of his cabs and homing in on the sound you want since you live in that area. Good luck

The computer modelling programs are great if you know what you are doing because they cut down the calculation time but if you don't understand the theory then they can easily mislead you. Qts is very low for these speakers which means that any cab you build will be overdamped and will have a bass that tails off very noticeably. Fs is high but Celestion make bass speakers which have a high fs and it seems to be true that the fundamentals aren't as important as the harmonics in the way we hear somaybe that's how they get away with it. Anyway these look like midrange speakers to me too whatever the seller/manufacturers say. Another problem may be the amp. I love those old Peaveys but you seem to be operating 6x 8ohm speakers in parallel giving a 1.3 ohm load. The amp won't do this and will power limit to protect itself. You could try wiring the cabs internally in series (16 ohms each) and then running them in parallel giving a load of 5.3 ohms which the amp will be happy with. Alternatively go back to the supplier and tell them the speakers are not bass speakers and ask them what they can do about it

[quote name='Arrakis' post='1211447' date='Apr 26 2011, 09:04 AM']Well the reason i want the extra cab is that the 2x15 isnt particularly good at dishing out the fuzz, I like more drivers for that they seem to sound better, the 8x10 i used to have sounded great for that. I was contemplating trying to make a new baffle for 10s but figured it would be easier to swap out the 12s for bass ones though obviously this doesnt seemto be such a gd idea. As for the 2 cubic feet, Matamp Retro cabs are pretty beasty in size so perhaps putting 2 drivers in with the other holes blocked or on a new baffle would work. Not sure I fancy running the 2 amp ideas as its more to go wrong and lug around (says the bloke wanting 2 massive cabs lol) etc What I dont understand is that I have used bass 4x12 before of the same dimensions of this cab, a marshall and a old trace elliot cab both branded bass 4x12 both the same size... so whats up with that?[/quote] There is probably no technical problem in changing the drivers for bass ones other than just choosing the right ones. If you start with a ready built cab then the choice is going to be limited. Most bass cabs are ported cabs for the very good reason that this is the best way of getting a decent level of bass out of a relatively small cab. Tuning a ported cab is critical for a decent sound and you'll need to get to grips with all this to get a good result. If you tell me the size of the cab I can suggest some drivers that you might consider. The internal dimensions would be good. You should realise however that there may be some woodwork involved in adapting the cab. Four 12" bass speakers are going to cost you £200-300 for anything reasonable and more if you go for lightweight or better quality. You'd probably get as good a result with less hassle by selling your cab and putting in that extra for a bass cab you can try before buying. Not all 4x12's or even 4x10's sound the same or give the fuzz you want. On the other hand you may enjoy fiddling around with speakers and you'll learn loads in the process. If you can afford £200 and don't mind if it is only a partial success then you'll find loads of people here to give advice. Over to you

It's almost never worth trying to adapt an existing cab like this because of the problems of matching speaker to cab volumes. Cabs with the original drivers are usually worth more than ones with replacements anyway, even if the replacement is an 'upgrade'. That doesn't mean it can't be done however. Why do you want to do this I wonder? Do you have a sound in mind that you are trying to achieve? Do you think you need extra volume? Is it because a full stack looks cool, you could always take the 4x12 and not connect it! You wouldn't be the first person to do this by a long way. Speakers don't have a 'sound' which is solely ,or even mainly, connected with their size. Just substituting speakers will be unpredictable in the sound you achieve unless you know a lot about interpreting data and speaker design, even then there is still a bit of luck involved, thought he more experienced you are the luckier you get. I reckon that if you tell people what you are trying to achieve you'll get some good advice.

Try Rapid [url="http://www.rapidonline.com/Electronic-Components"]http://www.rapidonline.com/Electronic-Components[/url]

To get decent bass out of a speaker the speakers and cab have to be matched as Mr Foxen has said. This rather than the brand should determine which way to go. I'd avoid using 4ohm speakers without checking Xmax which is the excursion. 4 ohm speakers generally have shortened voice coils and wimp out earlier than 8's. In any case you want two 8's to get 4ohms.

The centre chamber will act as an acoustic filter removing some high frequencies from the two centre speakers. they claim a resonant centre chamber with side ports but for this to work properly the centre chamber would need to be sealed at the front, have they removed a panel for the photo I wonder? This sort of design was worked out before the work of Thiele was widely known and probably is technically dubious. A sort of "throw lots of big speakers at it and make it look good" approach.

The Me 15-200 is exactly that a 15" 200W speaker Qts 0.59, Vas 224 l,Qes 0.67 fs 46Hz if you want the T/S parameters. It was probably made in the early 1990's

Since you've tried so many rigs it's actually unlikely to be that. I'll bet the audience isn't hearing what you hear on stage, that would defy the laws of physics by the way. For a bassist the grass is always greener on the other (audiences) side. Either get a mate to play while you listen to your rig or get a female jack/jack socket and join your two longest leads together and get right out there. If you are still unhappy with the sound you have to listen to other bassists and plump for ones who have the live sound you want. It could be the rig but it could be the guitar, the strings or eq. You've been trying a lot of respectable gear, I suspect youre just not hearing what the audience hear.

Hi Jack, I think Mr Foxen is right, if you want that exact sound then a 1x10 or 2x10 will give you the sound with portability and a sealed cab is the easiest build anyway so long as the box is airtight. I wouldn't worry too much about the impedance unless you are using a valve amp. The few dB you lose shouldn't be a problem in a recording situation. Sealed cabs typically have better controlled bass with better transient response. The cost is a higher cut off point with a longer slower roll off in output below that along with lower maximum output. When you are recording you can use eq to lift the bottom end and this works well with the 12dB/octave roll off of these cabs. You also don't really want a lot of high power fundamental in a small room. The 'problem' with multiple drivers is that the sound travels different path lengths to get to a particular point. This means that for frequencies where the speakers are spaced roughly a wavelength apart or more the sound from adjacent speakers might be arriving out of phase and cancelling or in phase and reinforcing each other. They get very directional at high frequencies and a lot of highs get lost. this gives them their 'vintage' sound. If you are mic'ing closer than the diameter of the speaker then you are effectively mic'ing the speaker and not the cab. You need to find out if it is the cab sound or the specific Jensen driver that you like the sound of. I've got a little digital recorder that I use fior recording gigs/practice. I'd take it out with my normal recording mic and go round the shops recording samples on the cabs they have on offer to see what sounds i could get, then I'd have a better idea of how critical a particular driver is.

I'm surprised you haven't been inundated, Your best bet is Lemonrock where you can check out dozens of local bands, listen to mp3's of most of them and check their song lists and diaries. If they'll travel Snappa (not my band)are a great party band who are totally professional but you'll probably get someone more local. Good luck

No experience with the cab but I have a Mag 600 which has been good as gold. Ashdown have great after sales, really helpful.

Isobariks are borrowed from hi fi designs, 'Normal' speakers operating in a sealed cab change the air pressure as they move to and fro'. putting a second speaker behind with an air chamber means the radiating speaker is operating under constant pressure (hence the name) and promises more linear movement of the cone and higher fidelity. Linn made particularly successful speakers this way. Even for hi fi there is little real advantage in isobariks and they remain a niche product. For bass it is just mad, twice the weight and twice the price for a very similar result. Just as Bill says. You'd get a better result by just using a better single driver.

[quote name='LawrenceH' post='1177372' date='Mar 26 2011, 05:12 PM']Also, incidentally that graph is very revealing about axial rotation on the string movement. I assume that the rise-dip-rise response on the 1st harmonic (or 2nd, depending on preferred nomenclature!) is because the plane of string vibration shifts from horizontal to vertical back to horizontal in relation to the pickup poles. Makes me realise that there's another potential source of audible 'beats' to a note, on top of any pitch-based phase interference (as in when tuning by harmonics). It also makes me think that a volume drop in low frequency harmonics in my slap playing v fingerstyle is probably because I'm hitting the string too vertically, and I should aim for a different angle of string attack to better excite the pickup. Who'd have thought that a frequency response graph could teach you something about playing technique? [/quote] It's an interesting graph the even harmonics are showing a very different decay to the odd numbered harmonics, I wonder why. I'll bet there's some sort of series in the maths. Back when i taught science we used to stretch a long steel wire over a bench and watch the vibration with a strobe light. You could clearly see the nodes moving as the vibration decayed.

I can think of several good reasons why effects should change with volume. One is the equal loudness effect which Alex Claber has recently written on. Basically (no pun) as volume increases you hear bass and treble better so it sounds the same as if you had adjusted your EQ. At high sound levels there can be an audible doppler effect if one speaker is trying to reproduce all the frequencies. Also at high frequencies the speaker will become less linear as the voice coil moves out of the magnet gap. Fuzz involves extra high frequency energy and this can overload a tweeter or kick in the protection circuit. None of this helps though as you would have to experiment to find the best settings at any given volume for any given speaker. At least you know you aren't imagining this effect,

The HK Lucas speakers are also highly rated and though I can't find specs for your system which seems to be discontinued I cetainly wouldn't expect the Proels to be any louder, However there does seem to be something wrong here, it probably is time to get back to the dealer.

It doesn't sound right for it to buzz/hum with nothing connected. Is the hum coming out of the speaker or is it coming from something inside the cab. I've had poorly made transformers be really quite noisy especially when you first switch them on. It is fine for your mic to be able to overload the system. You'd want to be able to get the full wattage out of even a low output mic so the 'hotter' mic's would be able to overload the amp. you just have to turn down.

[quote name='yorks5stringer' post='1170112' date='Mar 20 2011, 09:53 PM']No, it's not a perception thing...if I plug via the Mixer into the Mic In on the Speakers then there is plenty of power but the clip light comes on with the gain on at 9 oclock (zero is at 6 oclock) If I plug into the Line In, they are about half the volume and no louder than my Hi Fi even on full gain. Both with an MP3 track which rattles the other PA This is coupled with a buzz when first switched on which does not go by pressing ground loop switches or swapping to different mains circuits. Gigged with them last night, plenty of power when into Mic In but clip light on as above. Have tried fiddling with EQ's but surely I should be going into the Line In and getting adequate volume: the Mic In is really too sensitive( hence the early clipping)? Could'nt get to the back of the pub to listen last night as the cordless bass thing was on the blink![/quote] OK I think we may be confusing gain with power. The position of the volume control is irrelevant, it doesn't matter if the volume control is at 9 o'clock or 3.30. You may just be dealing with a mismatch between your mixer and your new speakers. Let's say your mixer gives out 100mV, the mic input is expecting 1mV and the line input 1000mV. This means your mixer is swamping the mic input unless it is turned right down. When you transfer the output to the line input the 100mV aren't enough to drive the amp to its full capacity. You can't get full output. The hum and noise the mixer put out will have a fixed component which is unaffected by the position of the volume controls on the mixer, especially the hum. Let us say it is 1/10th of a mV. When you were driving your old amp the hum wasn't noticeable as it was only a thousandth of the signal. Into the much more sensitive mic input it is now a 1/10th of the signal and you hear it all the time. A little test you can do is to set it up for maximum hum and then turn off the mains to the mixer, but not to the amp. It should keep going for a second or two but the hum will magically disappear. Another problem is that the mic input is probably 300ohms or low impedance and the mixer may be designed to match a high impedance input. Alex Claber has an article on this site [url="http://basschat.co.uk/index.php?showtopic=3730"]http://basschat.co.uk/index.php?showtopic=3730[/url] which might be worth reading. There's a number of things you could do, borrow another mixer with a higher output and see if the problem goes away. You can buy booster pre amps which will give you a little extra gain so you can match the line input. One cheap way of doing that might be to buy a simple little stereo mixer or even a graphic with a bit of gain to go between mixer and amp. If the Behringer is like the one I used to use then you might find one of the other line outputs or the control room output is a better match for your speakers. Let us know how you get on

The Proels ought to be OK, as you say they have reviewed extremely well. They use well rated Celestion drivers and claim a peak output of 128dB. The cdx1-1731 compression driver gives 110dB @ 1W and handles 75W giving 128dB which matches the Proel claim well enough. Proel say the amp is 400+100W 'continuous' and I'd use a 100W with this horn driver so the ratings probably are 'RMS' The bass driver looks like the TN1230 which will 'only' give 124dB at 400W however. The Celestion drivers don't have particularly good excursion so low frequencies might be limited at very high power. The HK's aren't bad speakers but the Proels ought to be louder. The only possible explanation I could guess at is that the lack of a bass bin is leaving you a little short here or that the flat response of the Proels is making them subjectively quieter. Alternatively the limit Leds may be coming in too soon. I've just re read your post. The noise when you switch on shouldn't happen. It may indicate some instability in the system which is eating up power. If they are under warranty get it checked out. Good Luck

This brought back memories, I designed something similar back in 1974. Bill is being a little harsh, though he is spot on with his date. It was around this time that the work of Thiele and Small was beginning to circulate which put the design of bass reflex/ported cabs on a firm theoretical basis. Before this the design of ported cabs was down to experience and inspired guesswork. We knew well enough how to tune the cabs as the physics of Helmholtz resonators was well enough known. Practical cabs were developed by measuring impedance plots. My theory was that by using a wedge shaped port I could produce a broader and flatter impedance peak for the 'horn' to better match the impedance peak at resonance of the speaker. It sounds a little far fetched to me now and I would explain it all in terms of Q but it was an honest attempt at the time, blown away now by better theoretical understanding and much better drivers. The speaker itself sounded quite good by the standard of the day and I sold quite a few. Enjoy your speaker as it is but don't waste money trying to upgrade it.

Those are PA speakers, I have some Yamaha monitors which are slightly older than these and they are awful! I also have some S112's and they are great. At some stage Yamaha started manufacturng in the USA using eminence speakers and as far as I can see the 15's could be eminences. If the S prefix indicated they are part of the club series then they are likely to be quite good speakers

firstly I don't believe this to be a universal truth, I am sure a lot of valve amps work perfectly happily with a lot of ported speakers. If there is a grain of truth in this I would suspect the interaction between the amp and speaker at low frequencies. The underlying reason for the impedance changes in the post above is that the speaker creates electrical currents as it moves in the magnetic field, these are in the opposite direction to the original signal. The biggest back EMF is created in a sealed cab at the bottom resonance but the sealed air in the cab controls the movement of the cone and hence the back EMF below resonance, in a ported cab the resonance peak is reduced but there is very little to control the movement of the cone below resonance and the back EMF can be quite large. Solid state amps differ from valve amps in three ways which would interact with this back emf. They usually have much larger amounts of negative feedback designed into the circuits which (sort of) compares the output of the amp with the input and corrects for any distortions. Secondly they usually have lower output impedances than valve amps and hence better damping factors. Thirdly the output transformers of valve amps are going to react in a fairly complex way with the back emf which will already be out of phase with the signal. A lot of this can be got rid of by filtering subsonic signals and most amps do this either by accident or design anyway. At a practical level this is not something I would worry about. Your ears will tell you if a particular amp and speaker work well together.