Bill Fitzmaurice

[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.

[quote name='ficelles' post='1346366' date='Aug 20 2011, 09:41 AM']My SWR head is a lot pokier into 4 ohms rather than 8 even though it only bumps it up from 120W to 160W... it seems to change the sound as well. The amp does run quite hot but the manual says to expect it to. ficelles[/quote] The power increase is moot, so changes in the sound are due to other driver and cab specs. BTW, most 4 ohm rated drivers aren't. For example, the DCR of the average 8 ohm driver is 5.5 ohms. By the same token the DCR of the average 4 ohm driver should be 2.7 ohms, but in fact it tends to run around 3.5 ohms. That makes the impedance of the average 4 ohm rated driver closer to 5 ohms. It gets even more complicated. A two driver 4 ohm cab would be loaded with 8 ohm drivers, so it would be a true 4 ohm cab. A four driver loaded 4 ohm cab would be loaded with either 4 ohm or 16 ohm drivers. 16 ohm drivers tend to have DCR values around 11 ohms, so the impedance of a 4x16 ohm cab would be 4 ohms, that of a 4x4 ohm cab 5 ohms. Then you take into consideration all the other spec differences between different impedance drivers, most notably inductance, and it quickly becomes apparent that the rated impedance in and of itself doesn't count for much.

[quote name='alexclaber' post='1345333' date='Aug 19 2011, 07:22 AM']And there's inductance to think about too![/quote]There are some who believe that inductance is the primary concern. [url="http://www.stereointegrity.com/docs/WooferSpeed.pdf"]http://www.stereointegrity.com/docs/WooferSpeed.pdf[/url] And since the ten, twelve and fifteen inch versions of the same driver have similar inductance, no surprise as they usually share the same voice coil, it renders the varying Mms figures rather moot.

[quote name='ironderby' post='1344860' date='Aug 18 2011, 03:59 PM']I heard from someone that you can't mix a 2x10 and 1x15 cab because its dangerous or could ruin your amp. Is this true? because i want to add a 1x15 for a little punch, thanks.[/quote] So long as there are no impedance issues there's no reason you can't, but the results are completely unpredictable. With matched cabs the results are totally predictable, it's what you have but more of it. OTOH if you don't like what you have the best route is to find a cab you do like for tone, and use as many as required for adequate output. BTW, fifteens don't inherently have any more punch than tens or twelves, so adding a fifteen to get more punch is operating under a mistaken assumption.

[quote name='Marvin' post='1343962' date='Aug 18 2011, 02:59 AM']I was just wondering what potential benefits and disadvantages there were to using a 4ohm cab.[/quote] To using it? Only a very modest increase in output, if any, while making it impossible to run a second cab if your amp doesn't have 2 ohm capability. The exception is a valve amp that has no 8 ohm tap. To offering it? So you won't lose a sale to someone who 'needs to get all the watts out of my amp', even though doing so is of little to no value.

[quote name='gafbass02' post='1343561' date='Aug 17 2011, 02:20 PM']I'm thinking of at backline only gigs having a bass cab and a guitar on either side of the stage for maximum and even spread, silly idea?[/quote] With guitar it would be OK, with bass you end up with cancellation effects that can result in less output and dispersion, not more. This explains why. What applies to PA subs also applies to bass cabs. [url="http://www.prosoundweb.com/article/in_search_of_the_power_alley/"]http://www.prosoundweb.com/article/in_sear...he_power_alley/[/url]

[quote name='Mr. Foxen' post='1343791' date='Aug 17 2011, 05:45 PM']Speaker efficiency and voicing.[/quote]Mainly the voicing, I'd suspect. Most combos have high Q drivers in cabs that are technically too small, which results in no true deep lows but an exaggerated humped midbass response. That makes them sound louder than cabs with lower/flatter response. The difference in what a 300w amp and 150w amp can produce is at best only 3dB, the midbass hump of a combo can be 6dB, easily making up for the power difference and more.

[quote name='flyfisher' post='1343497' date='Aug 17 2011, 01:40 PM']Because the bass and guitar frequencies are well separated in the mix[/quote]The problem is that they aren't. And if you're getting all the mids from a guitar cab at ear level you can't hear any of the mids from your cab down below waist level. The technical explanation is called Precedence Effect. It's tough enough to hear your mids with the cab down low and not tilted back, it's impossible with the mids from the guitar masking them.