fonzoooroo Posted March 11, 2011 Share Posted March 11, 2011 I recenty got hold of a "COMPACT Sound MKII" 1x15" folded horn cab. It's labelled as 100W at 8 ohms. The logic was simple: At £12.50 I couldn't go wrong! I checked it worked. After an hour with the kitchen cleaner, rags, superglue and finally boot polish, it looked presentable. I then whipped the driver out, replaced the world's thinnest speaker cable with some that has copper in(!) and that's it. The size of the cab is fantastic. nice and easy to load into cars for practices etc... and it'll take HUGE power. (I'm running a bass POD/1000W InterM Power amp setup)... I've (just to try it - wouldn't fancy it long term!) run the amp bridged and kept turning it up - No distortion right up to the "clip" lights... So it's perfect? ... Well...... No... My gigging cab is a Peavey Hisys 3 (2x12" with mid and horn) with Eminence Delta 12 LFs (with port tuned to compensate) replacing the black widows (which were dead when I got it) and the smooth, effortless bottom end is fantastic... There's just loads of smooth, clean bass. (at the expense of efficiency, I might add... but that's OK!) I'd love to get more of this characteristic out of the little 15". Now, I know the folded horn 15" can't compete with this in the treble range, but I can't help but think that a modern driver with a stiffer cone would help get more bottom end out of it. (the outer suspension is barely softer than the cone itself - in fact I guess the cone's actually bending pretty significantly when it's playing) and hence get a lot closer to the sound of the Hisys. What do you think? Pics and dimensions to follow... Quote Link to comment Share on other sites More sharing options...
alexclaber Posted March 11, 2011 Share Posted March 11, 2011 The bottom you can get out of it is mostly dependent on the length of the horn and the size of the mouth, so unless that cab is huge (like bigger than an 8x10") you're never going to get deep lows. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted March 11, 2011 Share Posted March 11, 2011 [quote name='fonzoooroo' post='1157631' date='Mar 11 2011, 03:28 AM']I recenty got hold of a "COMPACT Sound MKII" 1x15" folded horn cab. What do you think?[/quote]'compact' and '1x15 folded horn' is an oxymoron. Pics and dimensions will reveal if any improvement is possible. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted March 11, 2011 Share Posted March 11, 2011 Also, the reason you can't hear breakup is the horn tends to filter out the higher harmonics of which the speaker breakup sound consists. That is why in pro sound horns, they use voltage limiters tuned to the cab, because protesting speakers won't be audible. The idea of horns isn't to take huge power, it is to get a lot of sound from not much power, the tradeoff is size, and limited frequency band. The W horns (Jaco and JPJ's Acoustic 360s) sound great because that limited frequency band is just in the right place (plus I think they aren't acting as a horn over a chunk of the range). Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 pic: dimensions: overall internal height: (incl. horn mouth)570mm overall internal width: 570mm overall internal depth: (measured from inside face of baffle) 300mm horn mouth: 570x150mm horn throat (correct term?) 570x40mm the driver: inside: Quote Link to comment Share on other sites More sharing options...
voxpop Posted March 12, 2011 Share Posted March 12, 2011 (edited) wow, that looks and measures very close to my 1980's Vox VR115 bass cab. [attachment=74607:vox_vr115.jpg] (stock picture) I put a Deltalite driver in mine after I using a speaker design program to match all current 15" drivers to the dimensions of the cab. Edited March 12, 2011 by voxpop Quote Link to comment Share on other sites More sharing options...
RichardH Posted March 12, 2011 Share Posted March 12, 2011 (edited) Forgive me if I'm being stupid, but isn't that a normal ported cab - i.e. direct radiator rather than a horn, but just with a tapered port? EDIT - doh - it's not a tapered port, just a trick of the photo. Edited March 12, 2011 by RichardH Quote Link to comment Share on other sites More sharing options...
voxpop Posted March 12, 2011 Share Posted March 12, 2011 [quote name='RichardH' post='1159015' date='Mar 12 2011, 09:19 AM']Forgive me if I'm being stupid, but isn't that a normal ported cab - i.e. direct radiator rather than a horn, but just with a tapered port?[/quote] I dont think it is a true horn design. Its more of a large vented port the exits the back of the drive unit and vents into a large area at the base of the cab. This kind of cab was very popular in the 1980's....I am sure someone could explain the design and why it went out of fashion. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted March 12, 2011 Share Posted March 12, 2011 Also appears to be made of chipboard, which kind of makes it not especially worthy of driver investment, if the current one works. Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 Yes, "Folded horn" seemes the best way to describe it with no research... I've only ever mucked about with sealed and ported cabs before... Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 [quote name='Mr. Foxen' post='1159102' date='Mar 12 2011, 11:14 AM']Also appears to be made of chipboard, which kind of makes it not especially worthy of driver investment, if the current one works.[/quote] Well that all depends on what driver, and what cost... Obviously, I'm not keen to whack a £150 driver in, but the cab is convenient, was REALLY cheap etc, so Icould justify chucking a bit of money at it... Quote Link to comment Share on other sites More sharing options...
alexclaber Posted March 12, 2011 Share Posted March 12, 2011 That's a ported cab - funny shaped port but nevertheless it is. Use a sine wave generator to find the tuning frequency, calculate the internal volume, then you know where to go with drivers. It'll need a lot of bracing to handle high power drivers, it needs lining with damping throughout and it's not going to be terribly robust because of the chipboard... Quote Link to comment Share on other sites More sharing options...
chris_b Posted March 12, 2011 Share Posted March 12, 2011 I had a cab like this, a Musicman 212 with EV speakers, in the late 80's. It sounded great, probably because of the EV's, but it was so heavy that it rarely went out of the house. Sounds like you enjoy a challenge and if you improve the sound by replacing the speaker then good. From a starting point of £12 you can spend a little more on it before you exceed any possible resale value. Quote Link to comment Share on other sites More sharing options...
voxpop Posted March 12, 2011 Share Posted March 12, 2011 [quote name='alexclaber' post='1159120' date='Mar 12 2011, 11:27 AM']That's a ported cab - funny shaped port but nevertheless it is. Use a sine wave generator to find the tuning frequency, calculate the internal volume, then you know where to go with drivers. It'll need a lot of bracing to handle high power drivers, it needs lining with damping throughout and it's not going to be terribly robust because of the chipboard...[/quote] I lined my Vox with acoustic foam and measured the vent to get the correct dimensions for the port and calculated the internal volume. Next down load a program from the web to calculate which driver to use. I then went to Celestion, Fane, Eminence websites and got info on 15" drivers and put the specs into the speaker program. I selected the best driver for a flat (ish) frequency responce. Of coarse you can select any drive unit to suit your sound.... from flat to warm over blown bass. Give it a go its free and could get you a great sound. Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 [quote name='alexclaber' post='1159120' date='Mar 12 2011, 11:27 AM']That's a ported cab - funny shaped port but nevertheless it is. Use a sine wave generator to find the tuning frequency, calculate the internal volume, then you know where to go with drivers. It'll need a lot of bracing to handle high power drivers, it needs lining with damping throughout and it's not going to be terribly robust because of the chipboard...[/quote] I'll look into it... Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 I assume taking the average WxH dimensions x overall length for the port dimensions? Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted March 12, 2011 Share Posted March 12, 2011 (edited) [quote name='voxpop' post='1159019' date='Mar 12 2011, 04:25 AM']I dont think it is a true horn design. Its more of a large vented port the exits the back of the drive unit and vents into a large area at the base of the cab. This kind of cab was very popular in the 1980's....I am sure someone could explain the design and why it went out of fashion.[/quote] Correct. It resembles a rear-loaded folded horn, but it's at best half the required size to function as one. Even a 50 Hz horn is no less than six feet long. Many cabs of this sort were produced in the 60s and 70s by companies who had no trained acoustical engineers on staff. They scaled down real folded horns, like the Jensen Imperial and JBL Keele bins, not realizing that you can't do that with a successful result, and what you end up with is a bass reflex cab with a flared duct. The result was no better than any other bass reflex cab. But as well engineered bass reflex cabs didn't come along until roughly 1975 they did hold their own until then. Interestingly these faux horns were produced by some very well known companies, including Sunn and Music Man, and no, they did not have trained acoustical engineers on staff. Sunn advertised the 200S as a rear loaded folded horn, and it was anything but. Designer Conrad Sundholm admitted that he called it a rear loaded folded horn after seeing the term used, though he had no idea what a rear loaded folded horn actually looked like or how they worked. Edited March 12, 2011 by Bill Fitzmaurice Quote Link to comment Share on other sites More sharing options...
voxpop Posted March 12, 2011 Share Posted March 12, 2011 [quote name='Bill Fitzmaurice' post='1159350' date='Mar 12 2011, 02:42 PM']Correct. It resembles a rear-loaded folded horn, but it's at best half the required size to function as one. Even a 50 Hz horn is no less than six feet long. Many cabs of this sort were produced in the 60s and 70s by companies who had no trained acoustical engineers on staff. They scaled down real folded horns, like the Jensen Imperial and JBL Keele bins, not realizing that you can't do that with a successful result, and what you end up with is a bass reflex cab with a flared duct. The result was no better than any other bass reflex cab. But as well engineered bass reflex cabs didn't come along until roughly 1975 they did hold their own until then. Interestingly these faux horns were produced by some very well known companies, including Sunn and Music Man, and no, they did not have trained acoustical engineers on staff. Sunn advertised the 200S as a rear loaded folded horn, and it was anything but. Designer Conrad Sundholm admitted that he called it a rear loaded folded horn after seeing the term used, though he had no idea what a rear loaded folded horn actually looked like or how they worked. [/quote] Thanks for the info........... Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted March 12, 2011 Share Posted March 12, 2011 [quote name='voxpop' post='1159356' date='Mar 12 2011, 09:47 AM']Thanks for the info...........[/quote] As for a driver for it, standard box modeling software cannot easily be used. A more sophisticated program like AkAbak or Hornresp is required, unless you can find someone with the requisite gear and expertise to measure the cab impedance. Then you can find out its resonant frequency and use that along with a standard box program to model different drivers in it. Quote Link to comment Share on other sites More sharing options...
xgsjx Posted March 12, 2011 Share Posted March 12, 2011 I'd take it apart & measure all the bits of chipboard, then go & buy some 1/2 decent plywood, burn all the chipboard & get a set of plans off Bill for a decent designed cab. Quote Link to comment Share on other sites More sharing options...
fonzoooroo Posted March 12, 2011 Author Share Posted March 12, 2011 [quote name='Bill Fitzmaurice' post='1159350' date='Mar 12 2011, 02:42 PM']though he had no idea what a rear loaded folded horn actually looked like or how they worked.[/quote] Excellent. Thanks for that reply - It's cleared a lot up! Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted March 12, 2011 Share Posted March 12, 2011 [quote name='fonzoooroo' post='1159617' date='Mar 12 2011, 12:48 PM']Excellent. Thanks for that reply - It's cleared a lot up![/quote] Somewhat OT, but not completely, I once reviewed a book entitled 'How to Build Speakers' or something of the sort. It wasn't a DIY book, it was a tutorial for potential production managers on how to set up a speaker building factory/assembly line. It was written by a chap who owned a fairly successful speaker company in the 1980s. In the book he admitted that he didn't know anything about acoustical engineering, nor did any of his employees. He got his designs the old fashioned way: he copied them from other companies. Trouble was, he didn't copy JBL or EV or the like, he copied others who apparently didn't know any more than he did. He didn't care how they sounded, he only cared if they looked right, as he knew that's what sold speakers. He was right. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted March 13, 2011 Share Posted March 13, 2011 (edited) 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. Edited March 13, 2011 by Phil Starr Quote Link to comment Share on other sites More sharing options...
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