Pete Fowler Posted March 9, 2004 Share Posted March 9, 2004 My buddy Thermio and I both scratch built a set of LS bass cabs and he did the djk mod to them. He took measurements on one cabinet as the mods progressed. Here is the data: 200 160 125 100 80 63 50 40 31 25 20 HZ 77 80 79 73 72 78 68 60 61 52 51 dB Stock, mouth braced 76 78 78 73 69 75 65 60 66 56 52 4.5 cuft, no ports 76 78 77 75 74 80 70 60 68 54 54 Two 4"dia 10" ports 76 79 78 76 75 80 71 60 68 54 53 Ports cut to 7" The interesting thing with 10" ports is the boxes went deep, but the snappy, fast horn sound was lost! Cutting the port length to 7" brought the snap and speed back to same as stock, plus the lows remained, esp. at the 31Hz box tuning point. This data is with K33E driver and light stuffing. We think a K43E in this box would be superb, but haven't tried it yet. I'm going to try the mods using two 4" ports with both ends flaired (Thermio used 4" PVC). Flaring is supposed to reduce distortion and possibly increase the gain. Parts Express sells the kits. Neither of us is going back to stock. Pete Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 9, 2004 Share Posted March 9, 2004 Pete, That is just awesome. I have been wanting to see someone post some real data on this mod. Many thanks! Marvel Quote Link to comment Share on other sites More sharing options...
rtaylor Posted March 10, 2004 Share Posted March 10, 2004 ---------------- On 3/9/2004 7:59:10 PM Pete Fowler wrote: My buddy Thermio and I both scratch built a set of LS bass cabs and he did the djk mod to them. He took measurements on one cabinet as the mods progressed. Here is the data: 200 160 125 100 80 63 50 40 31 25 20 HZ 77 80 79 73 72 78 68 60 61 52 51 dB Stock, mouth braced 76 78 78 73 69 75 65 60 66 56 52 4.5 cuft, no ports 76 78 77 75 74 80 70 60 68 54 54 Two 4"dia 10" ports 76 79 78 76 75 80 71 60 68 54 53 Ports cut to 7" The interesting thing with 10" ports is the boxes went deep, but the snappy, fast horn sound was lost! Cutting the port length to 7" brought the snap and speed back to same as stock, plus the lows remained, esp. at the 31Hz box tuning point. This data is with K33E driver and light stuffing. We think a K43E in this box would be superb, but haven't tried it yet. I'm going to try the mods using two 4" ports with both ends flaired (Thermio used 4" PVC). Flaring is supposed to reduce distortion and possibly increase the gain. Parts Express sells the kits. Neither of us is going back to stock. Pete ---------------- Pete. I just received the 4 4inch ports for this mod from parts express after being back ordered and they are not flared. Just a heads up. The one end does have a flange for attachment but it is not flared. Randy Quote Link to comment Share on other sites More sharing options...
Pete Fowler Posted March 10, 2004 Author Share Posted March 10, 2004 Hey Randy, The port I'm referring to is the 4" Precision Port, part number 268-352. I've seen the Parts Express sourced port and you're right, its not flared. The precision port does have flares at both ends and its a bit more expensive. I'm not sure I buy their claim of 3dB increased efficiency, but every little bit helps, ya? Quote Link to comment Share on other sites More sharing options...
KCM Posted March 10, 2004 Share Posted March 10, 2004 Thanks for the info, Pete ! This is something I'd like to try, as well. I plan to extend mine off the bottom of the existing cabinets so that I don't have to permanently alter anything. Did you do any equalization as described elsewhere ? That's the one part I didn't fully grasp..... -Ken Quote Link to comment Share on other sites More sharing options...
Pete Fowler Posted March 10, 2004 Author Share Posted March 10, 2004 Hey Ken, I can't help you with a full LaScala - I'm only using the bass horn portion with my Oris 150 horns. That said, this mod seems to lose some energy in the upper bass (250 to 120Hz range), so you'll want to boost that by 2-4dB (or cut the mid-horn and tweeter 2-4dB). I don't know if the LS crossovers have L-pads or something else that will allow you to do this. Others on this forum should be able to help. You'll find the music loses impact if you don't adjust for this loss. Shortening the port length to 7" really helps restore the mid-bass speed and slam, too. The EQ that djk mentions is designed to boost the lower bass up to the level of mid/upper bass output of the horn. I believe the LS is only horn-loaded to around 100Hz. You can still perform this mod without adding low-end EQ and have a respectable boost in mid-lower bass energy. But if you're a low bass freak it won't be enough. :-) Here are a couple other things Thermio and I ran across while experimenting... 1. The LS bass cabinet was designed so that the side walls can vibrate and add energy to the "perceived" mid-bass. If you expand the woofer chamber and port it, you no longer need the sidewall "enhancement". In fact, it muddies up the sound something terrible, well into the midrange! I see you want to keep the mods reversible, but I highly recommend bracing the sidewalls (as Frode has done - see his pics) to clean up the sound. As an experiment, I did the sidewall bracing first and the improvement in the mids is definitely due to suppressing the cabinet resonance. However, the midbass drops off a lot so you'll need the expansion/porting mod to bring it back. I'm trying to give you the big picture so you can make intelligent tradeoffs. Porting + side braces = great, but one without the other is not good in my opinion. 2. Put the LS on spikes - I thought Thermio was nuts to suggest it since the speakers are so heavy to begin with, but on carpet it makes a big difference. I've never tried it on hardwood or tile flooring. Hope this helps! Quote Link to comment Share on other sites More sharing options...
KCM Posted March 10, 2004 Share Posted March 10, 2004 I think I've got the idea, now. Thanks again, Pete ! -Ken Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted March 10, 2004 Share Posted March 10, 2004 Pete, Thanks for the post and disciplined testing on the LS. One question about that 4" port flared on both ends. I was looking at that for a project that is supposed to have a 4" port that is 6" in length. I was wondering if the flares would require the length of the port to be changed. Your take (and others) would be appreciated. Quote Link to comment Share on other sites More sharing options...
Pete Fowler Posted March 10, 2004 Author Share Posted March 10, 2004 Hey D-Dee, Yes, you must add length to the port to compensate for the flares. The rule of thumb I seem to recall is 1" per flare, so a 6" port flared at both ends should be 8" total - flare to flare. I think this is documented on the Precision Port website... Hope this helps! Quote Link to comment Share on other sites More sharing options...
JohnA Posted March 10, 2004 Share Posted March 10, 2004 Pete, Am I reading your table correctly? You got +2 dB at 25 and 31 Hz, +7 dB at 40 Hz (impressive), +3 dB at 63 Hz and roughly +/- 2 dB from 63 to 200 Hz? Can you run the numbers on a bass horn without and with the sidewall braces up to 500 Hz? Did they take out the 150 Hz to 300 Hz "bump'? I don't believe the vibrating sidewalls is a design feature. It's more like a flaw for which the cure is more expensive than Klipsch was willing to endure. What were the test conditions for your measurements? How was the bass horn situated in relation to walls? Please post pics. I'm looking for a pair of La Scala bass horns or Peavey FH-1s for a PA project. If you decide to sell them look me up! Quote Link to comment Share on other sites More sharing options...
rtaylor Posted March 10, 2004 Share Posted March 10, 2004 ---------------- On 3/10/2004 9:36:54 AM Pete Fowler wrote: Hey Randy, The port I'm referring to is the 4" Precision Port, part number 268-352. I've seen the Parts Express sourced port and you're right, its not flared. The precision port does have flares at both ends and its a bit more expensive. I'm not sure I buy their claim of 3dB increased efficiency, but every little bit helps, ya? ---------------- Thanks Pete, didn't see the 268 in the catalog I had. Back to the store! Quote Link to comment Share on other sites More sharing options...
Pete Fowler Posted March 10, 2004 Author Share Posted March 10, 2004 Howdy, Sorry the table is hard to read - the forum SW compresses spaces...with the ports cut to 7" and the sides braced: -1 at 120 on up +3 at 50/60/80/100Hz +0 at 40Hz +6 at 31Hz +2 at 25Hz/20Hz Thermio only ran up to 200Hz because we use these cabs as bass bins below 180-160Hz with Oris horns. Can't answer your 300-150 hump question. The cabinet is on a side wall about 1.5 ft out from the wall, sitting on spikes with carpet over concrete. We used a CDP with a test tone CD and a RadioShack digital SPL meter. No room compensation, etc. included. Frode posted pics of his project in the thread below "...pictures anyone?". Ours look essentially identical. Now, all the data and facts aside - its sounds really good which is the real point of the mod, ya? Acoustic jazz, rock, vocals - you name it. Thermio is a really particular guy when it comes to clean, articulate bass... You might try building a pair - they're simple boxes and the K33E drivers are around $105 ea. Can't beat it... Quote Link to comment Share on other sites More sharing options...
JohnA Posted March 10, 2004 Share Posted March 10, 2004 I don't have the tools to build them. I have a couple of friends in town that do if I can persuade them to do it. Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 10, 2004 Share Posted March 10, 2004 John, Have you ever been in the Roland Hayes auditorium in the UTC Fine Arts building? Looks like a coulpe of LS bass bins up in the ceiling. My youngest son was playing in a Chattanooga Youth Symphony concert there on Monday and I finally noticed the speakers up abve the stage. They don't use them for those concerts, so I had noticed them before. The hardest part of cutting the wood is the angles on those pieces for the doghouse. You have to have the wood clamped in a vertical position. That has been part of the talking I have done with the college carpenter/cabinet maker. He has helped me work through some of those issues, even though I haven't built anything yet. Marvel Quote Link to comment Share on other sites More sharing options...
BackBurner Posted March 11, 2004 Share Posted March 11, 2004 So who has the plans for building a bass bin from scratch ? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.