Vintage HiFi Audio Forum
Repair / Help Forum => Repair / Help => Topic started by: Slim-Shaddy on September 06, 2012, 08:31:46 PM
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I'm FINALLY going to recap my main speakers, and I was wondering while I'm in there, should I do the resistors too? Also, what would happen if I changed the value of one of the resistors? The biggest complaint I have about the speakers is the fact that they are a bit weak on bass. There is a 5 ohm resistor going to the woofer. Would I get more bass without muddying the sound by putting a 4 or 3 ohm resistor in there instead?
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I'm FINALLY going to recap my main speakers, and I was wondering while I'm in there, should I do the resistors too? Also, what would happen if I changed the value of one of the resistors? The biggest complaint I have about the speakers is the fact that they are a bit weak on bass. There is a 5 ohm resistor going to the woofer. Would I get more bass without muddying the sound by putting a 4 or 3 ohm resistor in there instead?
Sorry I personally cannot help you.
But as Bob Caver say's TRY IT AND FIND OUT
and then let us all know
Brian
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Changing the resistor value may also change the xover frequency.
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http://www.audiokarma.org/forums/attachment.php?attachmentid=249521&d=1294770546 (http://www.audiokarma.org/forums/attachment.php?attachmentid=249521&d=1294770546)
here's the schematic...
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I'm not an AK member so I can't view the schematic, but, I'm with Ron. Changing the value of a resistor can change the crossover parameters.
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I think it depends on where the resistor is placed... that's where I get confused
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I'm not sure how to attach a PDF file... we'll try this
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changing that resistor would change the transfer function of the x-over (as sunny wrote), but you may like the result. So try it, specially if the change will be subtle (like 5 to 4ohms or even 3). If it sounds god, that is all that matters. Keep the old resistor in case you wish to revert.
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Thank OBG. I may try it out. I just don't want to create a boost or gap in the FR between the woofer and low mid.
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Hey Ed!
Have you ever tried to do a frequency sweep of your listening room with some test tones and a SPL meter? You may have some nodes in your room that are either contributing factors or, the root problem for lacking a little bass. This is a very common problem. Your speakers, electronics, etc. may not be the issue.
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Carl,
I've thought about it, but have never done it. I have an SPL meter (granted it's a cheapy from the Rat Shack), but no test tone generator. I'm going to recap regardless... The speakers are 30 years old, so it's past due. Since resistors are cheap, I'll probably replace them too while I have the board out. If it turns out that the room is the issue, is it resolved by moving furniture and adding sound absorption materials, or would I have to do some EQing?
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The absolute foremost resource on those speakers is still alive and kicking. Email Roger Russell.
The truth of the matter is, in any circuit, when you change one parameter, all other parameters are effected in one way or another. See Mesh Analysis: http://en.wikipedia.org/wiki/Mesh_analysis (http://en.wikipedia.org/wiki/Mesh_analysis)
Changing the value of your resistor up or down an Ohm would have only a minor effect on the overall function of the crossover, but, I don't think that it would give you any more bass. It would slightly alter crossover points as well as change the overall impedance of the system, albeit most likely not very significantly by going up or down one Ohm. Assuming that the speakers remain in their current position, more bass would come from changing the T/S parameters of the low frequency drivers or changing the volume or configuration of the boxes.
If you REALLY want to know how much each of those values would change in the crossover network, you can build your system of linear equations using Mesh analysis. You can then throw your immense system of equations into MATLAB or LPSolve and find out.
Or you could just change them and see if you like how it sounds. ;D
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If you want to increase the bass response you should upgrade the inductors and leave the resistor values as is.
As for changing the resistors while in there, do it. I suggest using Mills 12 watt where the values permit.
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Would upping the inductance of one inductor in a circuit have some side effects other than serving to increase bass output such as changing the frequency at which the signal is being filtered?
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You're not upping the inductance, you want the values to remain the same. You would replace the stock inductors with higher quality air core versions. Solen and Janzten are excellent choices. Since the gauge and DCR values are not noted, you'd need to have the stock inductors tested.
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Ed,
Pianos n Stuff in Blawnox rents (or used to rent) equipment to measure your room. A Rane RA 30 provides full bandwith Pink noise and a 1/3 octave RTA. It will show where your room has humps, or dips in frequency response. Even with out an EQ, you will be able to instantly see changes due to variations in speaker or furniture placement or through use of tone controls. You might also be able to measure changes in the speakers performance before and after xover mods. The rental cost was reasonable the last time I used one.
My personal experience suggests proper EQ will make more difference than xover component changes (except for repair of defective parts). It can make good speakers sound great and great speakers blow you away.
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Sorry Jesse. I should read more carefully.
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Thanks for all of the input. As far as contacting R Russel.. I've asked him before about replacing the caps and he seemed to really dislike the idea, sating that there is no reason for it becaufse they should all be fine. He is great to talk to for advice about repair, but when it comes to updating or altering the speakers in any way, he seems to almost get offended.
Jesse,
Changing the inductor that goes to the woofer seems like a good idea.
klaus,
I would love to pick up a MQ, just to throw it on the system to see what kind of difference it makes, but they are not cheap. To be honest, I think it's asinine how much they are going for. For about the same price KRK makes a digital room corrector with a mic, which should remove the guesswork, and seemingly be an easier solution.
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My SS-315X has a spectrum analyzer. If you can find the mic cheap on ePay, we can use that to measure SPL at various frequencies about your listening area.
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I should have also mentioned that upgrading the electrolytic caps to film/foil types WILL result in an increased bass response. You might want to try that first before changing inductors to see if that cures the bass shy issue.
I know some folks say that the shunt caps don't matter, etc., etc., but I beg to differ. Normally, I'd recommend Sonicap Gen I's, but the values needed are too high, so you'll have to go with Solen or maybe Dayton for the shunt caps.
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I looked around a bit, but didn't find the info on your speakers that I was looking for. Are they ported, sealed or what?
What are the -3dB specs?
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I looked around a bit, but didn't find the info on your speakers that I was looking for. Are they ported, sealed or what?
What are the -3dB specs?
They are sealed with a 12" woofer, 8" lower mid, 1.5" upper mid, and 1" tweeter. I don't know what the FR is, but they are the first speakers designed by Roger Russell that didn't need an EQ for bass.
From the Roger Russell site:
4-way floor system has 12" woofer, 8" lower mid, 1-1/2" dome upper mid and 1" soft dome tweeter. Walnut finish. Black grille cloth.
Red and yellow level indicator lights at bottom right. Red light indicates tweeter fuse blown. Yellow light indicates maximum power level. Main and tweeter fuses are located at the back of the cabinet.
This was the first of the smaller systems to be designed in our new anechoic chamber.
Crossover frequencies: 250Hz, 1.4kHz and 7kHz
Impedance: 8 ohms
Output: 89dB @1w/1m
Power rating: 150w
Size: 35-5/8"H, 17-1/2"W and 11-3/4"D
Weight: 75 lb
Sold from: 1980 to 1985
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Yeah, that's the same info I found. Interesting that they don't list the frequency response.
Since they are sealed there is a tweak you might be able to do depending on the location of the driver screw holes on the baffle. If you can do this it will help clean up the mid-range and improve the bass response. This assumes the drivers are simply screwed into the baffle with wood screws right now.
Install Hurricane nuts (not T-nuts) with an 8-32 thread pattern by drilling out the holes to accommodate the Hurricane nut shaft size. You want to use a drill size slightly under the nut shaft diameter. Then use 8-32 cap screws to mount the drivers to the baffle. This couples the drivers much tighter to the baffle than can be done with wood screws. It really works. Also, be sure to check the driver gaskets for any damage.
While you have the drivers out, if the baskets are stamped steel, go ahead and add Dynamat Exteme to the spokes. This helps eliminate ringing, which will also help clean up the mid-range.
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Another worthy tweak to increase bass response is to add spikes to your speakers.
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Mac never stated frequency response characteristics until after Roger retired and Mac moved to 4 ohm ratings. I'll speculate the speakers (XR 16's if I recall correctly) have some useable output at 20hz, depending on the room and placement. I have measured this model before, in more than one room. They tend to rise just a bit over 10k hz, plateau and then start to roll off at the last 1/3 octave, maybe a bit lower, again depending on the room and placement. They sound very good with a little bit of a hump (just a db or two) at 50hz.
You don't need an EQ to benefit from measuring the room-it's very helpful to determine placement, height off the floor, toe-in, etc. If you can, try raising them until the tweeter is just above ear level (it may look bad, spousal harmony comes into play here). This reduces low frequency floor bounce and let's the high end open up a bit.
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While you have the drivers out, if the baskets are stamped steel, go ahead and add Dynamat Exteme to the spokes. This helps eliminate ringing, which will also help clean up the mid-range.
Wow. That's great advice. I never would have thought of that. Simple, but very effective.
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Be back in an hour - need to hit Ace for hurricane bolts and see if Bebst Buy still carries Dynamat.
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I doubt Ace carries the Hurricane nuts and cap screws, so if they don't have them you can order them from Parts Express.
A tip for mounting the Hurricane nuts. After drilling out the holes place the nut in position on the backside of the baffle. Use one of the cap screws with a thick washer and drive the cap screw into the Hurricane nut. This will pull the nut into the hole, which is better, easier and safer than trying to hammer the nut in from the backside. Don't go crazy with the torque, you just want to seat it.
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Is this what they look like?
[imghttp://home.comcast.net/~mc_audio/XR16.jpg[/img]
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Sorry, bad url; here: (http://home.comcast.net/~mc_audio/XR16.jpg)
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Thanks for posting that pic, Gary.
I agree with MacGeek that they would benefit from being raised up, which could be done with spikes. Adona has exactly what you need, their Multi-Element cones would kill two birds with one stone. They are 2.5 inches tall bringing the tweeter much closer to the ideal height while getting the woofer off the floor.
http://adonacorporation.com/tweaks.html (http://adonacorporation.com/tweaks.html)
I installed a set on my HT sub as it was just a little too close to the carpeted floor. Very nice quality and definitely improved the bass performance.
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Is this what they look like?
[imghttp://home.comcast.net/~mc_audio/XR16.jpg[/img]
Yep, that's them