Bill Fitzmaurice

[quote name='fatback' post='1370248' date='Sep 12 2011, 06:36 AM']I think it cures the feedback just because the cab is not so near the body of the bass rather than because of lost frequencies.[/quote]The distance would not make any difference. It's the notch filtering that accounts for it.

[quote name='fatback' post='1369701' date='Sep 11 2011, 02:09 PM']I've been raising my Midget to chest height by putting it on a keyboard stand. The idea is to stop my upright feeding back, and that's working a treat. However, I seem to be losing a significant amount of volume.[/quote] If the volume you're losing is at the frequencies where feedback occurs it's moot, because if you don't lose the volume you don't lose the feedback. An exact figure is difficult to arrive at, as there are a number of variables. To vastly oversimplify you'll lose about 6dB, centered at the frequency where 1/4 wavelength is equal to the distance between the cab and the floor.

[quote name='CraigPlaysBass' post='1368425' date='Sep 10 2011, 06:40 AM']Good shout guys, ME3008s they are! Spoke to the seller yesterday, he informed me that 3 of them had gone open-circuit and that I could have them all for free if I picked them up. So I did, they were screwed into massive 2x12 scoop bass bins, and had obviously seen some heavy usage. Will check them all today and see if they're repairable at all, if not, I have one that works... Any one got any good ideas for what to use it for? If it's so terrible for bass? [/quote] Between the short xmax and low Qts all it's really suited for is guitar.

[quote name='CraigPlaysBass' post='1367267' date='Sep 9 2011, 03:10 AM']Maybe rebadged was the wrong word, the model evolved into, may be a better one. I'm not normally one to blindly trust what a google search comes up with, but that's the best I could come up with.[/quote] The Delta 12 has a 56oz magnet. Those in question appear to have at the least 80oz, if not 109oz; see the picture of the Kappa 12 on the Eminence website. In this case seeing is believing, and I firmly believe these are not Delta 12s.

[quote name='Linus27' post='1367336' date='Sep 9 2011, 04:38 AM']Should I connect one speakon connection from the back of the amp into one speaker and the second spearkon connection on the back of the amp to the other speaker or one speakon connection from the amp head into one speaker and the from the back of that speaker, a speaker lead into the second speaker? Never really known which is the best way to do it or if it makes any difference.[/quote]Electrically both are parallel circuits, but with two cables to the amp each cab has a separate current pathway. With daisy chaining the current for both cabs must pass through the single cable attached to the amp. With cables of adequate gauge there's no problem with daisy chaining, but if your cables are questionable separate feeds is the safer method. [quote]Apparanly the shorter the cable, the better the sound quality, so daisy chaining would allow shorter cables.[/quote]True with 50 foot cables on PA, not a concern with six foot cables.

[quote name='CraigPlaysBass' post='1367079' date='Sep 8 2011, 05:12 PM']From what I've read, in a few places now, the EM12-2008s were rebadged as the Delta12s, so I will use their specs to build my cab, and see what happens![/quote]Look at the picture of the Delta 12 on the Eminence website. Clearly they're not the same as what you have. Before cutting any wood I'd find someone who has the gear to test the driver T/S specs.

[quote name='CraigPlaysBass' post='1366541' date='Sep 8 2011, 10:50 AM']The seller has just informed me, they are Eminence ME12s and are 300W and 8 ohms. I assume they are the Me12-2008 speakers, which were rebranded as the Delta 12s. There seems to be a few arguments online as to whether they are suitable for electric bass or not. At £25 a driver, however, I'm thinking 'Why Not'.[/quote] They appear to have a much larger magnet than the D12. Rumor has it that Eminence made drivers that look very much like this for Mesa, which Mesa called the Black Shadow, basically a stamped frame EVM12L copy. I had one 25 years ago, and the look was similar, especially the magnet size. It was a very good guitar driver, but not so much for bass, with too short an excursion.

[quote name='JTUK' post='1366069' date='Sep 8 2011, 04:21 AM']Is that a pressed chassis...??? cheaper production model ..??? if so I wouldn't be putting 400w into one.. I'd be think 400w the pair.[/quote] Steel chassis are common with OEM. It doesn't affect the power handling in the least. It does impact driver durability; cast frames are stronger and stiffer, and are better able to handle the weight of a heavy magnet without flexing. To account for that flexing the gap tends to be larger, and that reduces sensitivity, especially in the highs. One would expect a driver of this sort to be optimized as a PA woofer, not as a full range electric bass driver.

[quote name='davideleira' post='1363033' date='Sep 5 2011, 11:18 AM']I don't want to buy another cab... Is there another solution?[/quote]Not really. You can only get so much out of a 210, and more power probably won't help.

[quote name='JTUK' post='1357135' date='Aug 31 2011, 02:58 AM']The last time this was an issue, I just took most of the bass off the amp and that worked.[/quote] It works, but the bandwidth of a bass EQ, or for that matter even a graphic EQ, is so wide that you remove a lot of desired content along with the boom. A parametric is much better. Lifting does the same, removing the boundary reinforcement in the midbass without bothering the lows, but finding the right cab lift height for the boom frequency of the room is a chore.

[quote name='Bankai' post='1357083' date='Aug 30 2011, 07:52 PM']Having had to do similar things with turntables, we had best results by first placing a paving slab on the stage, a block of insulation foam on top of that, and then tennisball halfs on the four corners of the cab where it makes contact.[/quote] That's a very different situation. Vibration of the floor induced by its resonating in concert with the acoustical output of the speakers is transferred mechanically through the stand to the turntable to the cartridge, which results in a feedback loop. Isolation as you did will fix that. There's nothing in a speaker cab or amp that will cause a mechanical feedback loop.

[quote name='Ian Savage' post='1356855' date='Aug 30 2011, 04:01 PM']Auralex Gramma Pad seems to be a solution many around here are very happy with; never used one myself, but the principle of 'em's sound and I HAVE used very similar pads for my studio monitors.[/quote] IME if it works the cab is defectively flimsy. The floor vibrates in response to acoustical pressure, unless the cab itself vibrates excessively. Otherwise all the pad can absorb is the vibration that it might impart to the cab. Lifting the cab 2 to 3 feet will reduce some of the boundary coupling in the midbass, and that can help reduce midbass boom. A parametric EQ is perfect, allowing you to notch the precise frequency of the boom at the source so the floor won't vibrate and/or boundary reflection modes are compensated for, without killing broadband response.

[quote name='Jamesrt2004' post='1344053' date='Aug 18 2011, 04:26 AM']Ok, so at my rehearsal room's[/quote]What are the room dimensions? In smaller rooms amp and speaker response can be totally swamped by the room response.

[quote name='BigRedX' post='1355585' date='Aug 29 2011, 02:33 PM']I would be very reluctant to buy one directly from them.[/quote] You'd also find it impossible.

[quote name='bobbytodd' post='1354037' date='Aug 27 2011, 08:15 PM']if it sounds right and the person it happy with it whats the fuss[/quote] Well, if you paid for a 16 ounce steak and were served an 8 ounce steak would you be happy just because it tastes good? [quote]I can't see this fake claim as being any more unethical as quoted car mpg figures or health claims for diet drinks[/quote]It certainly is no more unethical, but also is no more excusable. I really have to wonder about the personal values of those who not only seem not to to care when they've been defrauded, but even defend the actions of the defrauder.

[quote name='Rich' post='1353435' date='Aug 27 2011, 06:17 AM']Bill -- for the total thickies among us (i.e. me), could you explain the difference between 1st order high-pass and 3rd order?[/quote] [url="http://www.bcae1.com/xoorder.htm"]http://www.bcae1.com/xoorder.htm[/url]

[quote name='aldude' post='1352875' date='Aug 26 2011, 01:58 PM']Still.... does anyone know the power output at 2.7 ohms? [/quote]That brings up the second part of the TC epic. They state that three of their 8 ohm cabs may be used, but not three of anyone else's. Why? Because their cabs aren't 8 ohms. Impedance is based on the driver DCR, with DCR being approximately 0.7 x impedance (Z). The average 8 ohm cab therefore has a DCR of 5.6 ohms, plus or minus 10%. The DCR of the TC cab is 7 ohms, making it a nominal 10 ohm cab. They don't call it a 10 ohm cab of course, and the only logical reason why is to not upset the 'I can't use a 10 ohm cab, I won't be able to get all of the watts out of my amp' crowd. I suppose that would upset them all the more if they knew they only had half the advertised watts to begin with. Obviously TC has tested them amp with three of their cabs and found it works. Only they know if they've done so with three 8 ohm cabs, and whether it works with them or not.

[quote name='thodrik' post='1352449' date='Aug 26 2011, 09:11 AM']The fact that it is 236 watts does not make it any less of a giggable amp.[/quote]Quite right. Only 167 HP doesn't make a Mazda MX-5 any less of a drivable car, and they see no need to advertise it as 300 'super special Mazda horsepower' as a result. The discussion isn't about how the amp works, it's about ethics. If you don't think it's bad form to lie that's your lot to deal with.

[quote name='Merton' post='1352340' date='Aug 26 2011, 08:05 AM']Haha! About to respond to your PM sir As for this thread, what a lot of nonsense. Who gives a f*** what the rating is as long as it sounds good to the person using it. And the audience, I guess [/quote] There are two distinct camps on this issue at TB. One (which I subscribe to) says that lying about the power ratings of their amps is just plain wrong. The other, which is typified by responses like yours, says that as long as it sounds good we don't care if they are advertising fraudulent power ratings. Consider that attitude the next time you go to the petrol pump that may, or may not, be giving you every liter you've paid for.

[quote name='AsterL' post='1350329' date='Aug 24 2011, 10:08 AM']What things should you keep in mind when looking for replacement speakers for bass cabs? I'm looking into upgrading a 210 cab from 200 watts @ 8 ohms to 600 Watts @ 4 Ohms[/quote]T/S specs that are compatible with the cab, midrange frequency response that meets your requirements, and the realization that wattage ratings mean very little. It's excursion (xmax), frequency response and sensitivity that determine output. As for impedance, seldom is there an advantage to a 4 ohm cab.

What's the displacement limited power of the Midget? If it's 600w then the most additional output you might get is 3dB. If it's 300w or less you won't get any more output. A second Midget will get you 5 to 6dB with your existing amp.

[quote name='MoonBassAlpha' post='1348166' date='Aug 22 2011, 12:12 PM']Re reading the original ad: "Pair of New Trace Elliot LeSon WRT300 High Frequency Tweeters 40W RMS PA/Hi-Fi Speaker. New Old Stock - these tweeters have been stored in a sealed box for about 14 years are in mint condiditon, have never been used but have been fully tested. They were used in various Trace products including the TAPA Acoustic PA System and the Revo 8 Monitors. We chose them as they sound excellent and are extremly reliable; we used 1000s of them and never had a failure. They were made for Trace by LeSon of Brazil, famous for their magnetic phono cartridges and made to a very high standard. They have a built-in crossover at around 5KHz and have a high impedance so can just be added to any system to extend the frequency response right up to 22KHz." And: "All the specifications: • 3" High Frequency Tweeters 40Wrms (AES standard) power handling and 105dB sensitivity Frequecy response....................... 5KHz - 22KHz Built-in Crossover.............. 4u7/63V 6dB/Octave PowerRating ............................................40Wrms Chassistype .................................................... ABS Magnettype.................Ferro-Electric Transducer OverallDiameter ...........................................85mm Overalldepth................................................. 48mm Cut outdiameter........................................... 75mm Numberof mounting holes.................................. 4 Mountingslot PCD........................................85mm" Implies that an additional xover shouldn't be needed, though the casings are glued closed, so not much scope for fiddling with what's inside. So, armed with this info, wiring series or parallel, or just try one first? At xover of 5kHz, would 40W be enough handling power, I'm guessing just about?[/quote]There's no useful technical information there. Lacking that all you can doi is to use them as they are. I'd cross fire them at a 30 to 45 degree inward toe on each.

[quote name='MoonBassAlpha' post='1347834' date='Aug 22 2011, 05:38 AM']Tweets arrived this morning. They are Le Son (Brasil) and some kind of piezo but with a transformer built in. Can't find much in a quick search, but the us patent 4845776 suggests they are a bit different to standard piezos. Looks like SWR might have used them at some point too. Hopefully not junk, but I don't want to destroy them straight off![/quote]It all depends on their impedance. If the transformer results in a standard 4 or 8 ohm load then you can use a filter configured for that. A standard piezo is a high impedance capacitive load and requires something entirely different.

[quote name='MoonBassAlpha' post='1347573' date='Aug 21 2011, 04:48 PM']I should have put what (little) detail I have of them. They're of a type used in old Trace Elliot PA cabs (NOS) and 105dB sensitivity, apparently. I see what you're saying Bill about the xover though, this will only be 6dB down at 2.5KHz (or is that 9?) Thanks for the input though, I really value your opinion. Cheers Jules[/quote]If they originally ran with a 5kHz first order filter then they could probably be run to at least 3kHz with third order filtering yet still have far better protection. That's key, as not even tens are capable of decent off-axis response above 2.5kHz. It would be good to know exactly what they are to be sure of what their capability is.

Either vertical or cross-fired. But with a 1st order high-pass I wouldn't count on them lasting very long. 3rd order is the minimum acceptable IME. And if they're low sensitivity home hi-fi or autosound tweeters they won't contribute much.