It sounds to me like the speakers are getting a lot more boundary reinforcement in your room than what the designer anticipated, and reducing the amount of bass they put out may be a lot easier than changing your room's acoustics.
I have zero experience with the Eufrodites, but eyeballing the speaker, I see four woofers and a big port, and the description sounds like it's a transmission line variant. You might try attenuating the port's output via damping materials. Open-cell foam, polyester batting, a bath towel, whatever you have on hand. The idea is to find out if this general approach makes a net improvement, and then you can fine tune it from there. You might get better results (tighter bass with decent impact) by solidly sealing off the ports completely, turning the bass system into a sealed box, perhaps even with that damping material inside.
Duke
dealer/manufacturer |
"What material would be best to use for an appropriate stuffing?"
I'm not sure. With the towel, what you did was add flow resistance to the port; you made it significantly harder for the low frequency energy to get out of the port. If the towel was filling the port completely, then you added a lot of flow resistance; the more airspace around it, the less flow resistance.
My suggestion is, trial and error. Bigger towel, smaller towel, see which is a step in the right direction. Maybe open-cell foam (when you "haaaaah" into the foam, can you feel the heat form your breath on the other side? If so, then it' open-cell foam), again I can't tell you how completely you should fill port, or how deep the foam should extend into the port.
Long-hair wool was mentioned. That's great for stuffing a transmission line, but imo the intention here is different - we're trying to reduce low bass output, rather than facilitate it. Unless you packed it tightly into a cloth bag and crammed it into the port - then, it would be behaving more as flow resistance than as gentle damping along the length of the line. Imo you can accomplish the same thing for less money with tightly packed polyester batting or fiberfill.
The variovent is itself a flow resistance device, and one with a rather strong flow resistance, maybe more like packing the port tightly with a towel than like open-cell foam. You'd want to turn the cabinet almost into a sealed box, with the only pathway between the inside and outside being through the variovent (which is dense fiberglass compressed inside a plastic housing that has airflow holes in it).
Duke |
Using absorbent material in the ports isn't the ideal, but if the Eufrodites' way of working isn't working for you and your room, then imo it's reasonable to try to find a solution that is a worthwhile net improvement.
I design speakers too, and most of my designs have user-adjustable ports, because I can't always reliably predict in advance what the room acoustic situation will be like, where the speakers will be positioned, and/or what the output impedance will be of amplifiers they might be used with. I have one customer (a single-ended triode amplifier manufacturer) who went all the way to plugging the ports on his speakers, so they are now sealed boxes. Yeah that theoretically goes against their "way of working", but it's what works best for him, his amps, and his room (speakers up against one wall, listening couch up against the opposite wall, so lots of boundary reinforcement).
As for optimizing the type and amount of damping material, I'm afraid it's a matter of trial and error, and a juggling of tradeoffs.
Duke |
This is a long shot, so consider it just the ravings of an insomniac:
It is possible that the enclosure is a transmission line/tuned port hybrid of sorts, and if so, you might be able to tighten up the bottom end a bit by lowering the tuning frequency. One way to do so would be to reduce the cross-sectional area of the port over its entire length.
Remove the stuffing from the port, then measure how far the port extends into the box (horizontally). Cut several boards that long, and just wide enough to fit into the port. Stack enough such boards in the port to roughly cut its cross-sectional area in half.
If the box functions as a reflex box, we've just lowered the tuning frequency somewhat. And that just might be a better "fix" than stuffing the port with damping material. If the results seem promising, find the optimum number of boards by trial-and-error, and then if you want to, glue and/or screw the boards together to make a solid block, and maybe wrap the ends with electrical tape or some such to give you a snug, rattle-free friction fit.
Theaudiotweak's suggestion of improving the coupling between speaker and floor may work very well, I don't know, I have less experience with that approach. I don't see how it could do any harm (unlike the things I've recommended, which very well could be detrimental, especially in the wrong dosages... but at least they're easily reversible).
Duke |
"It would be very interesting to compare the "absorbing" product to the "mechanical grounding" method to hear which is more effective in minimizing/eliminating the bass boom."
It's not necessarily either/or; neither excludes the other.
Also, IF lowering the tuning frequency of the port by reducing its cross-sectional area (as described a few posts up) actually works, I think that approach holds out more promise than port-stuffing because it is less likely to have a downside.
Duke |
"I'm also not 100% sure I understand the way the wood boards have to be inserted into the bass port. Can you clarify? Does it matter which wood to use and what the thickness of the board should be?"
Suppose the port is 150 mm tall by 200 mm wide by 300 mm deep. And suppose you have access to 18 mm plywood (the kind of wood really doesn't matter - its main function is to take up space). In this case, I would suggest cutting four or five boards, each about 199 mm wide by 300 mm long, and of course 18 mm thick. See if placing some or all of the boards in the port, thus reducing its cross-sectional area, makes a worthwhile improvement. The theory is, if the box is acting like a vented box down in the bass region, this will lower the tuning frequency and hopefully reduce any upper bass bumpage without detrimental side effects.
"Duke, If one product`s purpose is to "absorb" or hinder vibrantion/resonance(attempting to isolate), this is different than "mechanical grounding"(MG). With MG there`s no attempt to absorb, rather you allow the vibration/resonance a rapid and complete exit channel to "gound" this energy into the floor.One seems opposite from the other.An example of the MG approach is the Star Sound system brass points and stands."
I don't see these two approaches as opposites. Your approach addresses mechanical vibration, and mine addresses airborne vibrations, better known as sound waves. One can have a speaker with a resistive port (such as a Variovent, or a DIY variant like I described above), and that speaker can also be sitting on brass points. The opposite of your approach would be de-coupling the cabinet from the floor, via something like Herbie's Big Dots.
I have not experienced mechanical grounding to make a significant difference in the frequency response of a loudspeaker system. From the description, it sounded to me like a large change in the bass response was called for, and so I suggested a possible acoustic solution. Nothing wrong with trying a mechanical solution as well.
Nothing against bass traps or speaker re-positioning either. The more options Amuseb has available, the greater his chances of success. I'm just trying to add to his options by describing a couple of unorthodox approaches that are inexpensive and easily reversible.
Duke |
Sorry the boards-in-the-port didn't help.
Equalization or a solid state amp are probably your least room-intrusive possibilities at this point. And nothing wrong with room treatment.
Unfortunately I don't have any more inexpensive suggestions.
It is possible that a couple of small, cheap subwoofers, placed one behind each of your speakers and operating out-of-phase, would introduce enough cancellation to smooth things out.
Duke |
"I will probably call for some expert opinion on the room acoustics in the coming days." May I recommend Jeff Hedback of Hedback Designed Acoustics. Jeff's day job mostly consists of designing recording studios, and his studios have been honored in the past three "Best of The Year" issues of Mix Magazine (2011, 2012, and 2013). But he has done work for a growing number of home audio and home studio rooms. He doesn't sell any products, just analysis and recommendations, which he still offers at a reasonable rate. Hedback Designed AcousticsWhy not just get bass traps and put them on the corners? Because room acoustic treatment is a little bit like crossover design: Not that hard to do, but quite hard to do really well. One person may say, gee that crossover needs some more capacitance, but the real question is, how much, and where should it go in the circuit? Likewise with bass traps - what kind, how much, and where for most cost-effective and aesthetically acceptable results, are questions that are hard to answer really well. I have worked with Jeff on several projects, and am continually amazed at the innovative solutions he comes up with. Duke |
