Speaker setup changes

[Canetoad]

I’ve been tinkering with the setup of my main speakers (MTM floorstanders) and am both pleased and confused with the results and whether any further modifications might achieve.

I was wanting to get rid of a lot of the bass boom I was hearing, so I thought I'd try putting a granite slab (Tesco cutting board) under each speaker. While it tightened up the bass no end and removed the boom, I thought it was also over accentuating the midrange and, as a result, made the speakers sound a bit shouty. After about a week of using them I removed them and put the speakers back on the carpet (suspended floor). This was a few months ago.

After doing a lot of headphone listening lately, it was plain to me I wasn’t hearing the treble sparkle from my speakers that I was hearing via headphones. I’m now back to the point where bass boom is even more obvious! While I think the headphones can sometimes be a little bright I wasn’t happy with the sounds from the speakers anymore. I was starting to think I might have to replace the speakers to improve matters.

I then decided to re-install the granite and have another listen. Wow! I now realise the midrange isn’t shouty at all! It’s more prominent because the bass boom is gone. Bass is still seismic but much cleaner and tighter. Mind you, since the last time I tried this, I’ve also made an upgrade to my Caiman DAC, so this is also adding to the resultant sound quality improvements I’m hearing. Granite will definitely be staying!

I’m now wondering if a set of spiked bases would be an improvement over the granite? These would couple the speakers to the floor. I’m confused as to what the granite is actually doing. Surely it isn’t coupling the speakers to the floor but rather decoupling them?

I might make up a couple of MDF bases with spikes and experiment to see if I can get further improvements.

I’d appreciate any thoughts. :)

[DSJR]

What speakers are they? Do they have bottom spikes and can you pull them further into the room. if they're firing down the length of a rectangular room, can they work across it?

In no way am I going down the current "AVI thinking" that all big passive speakers boom and three ways with the lower crossover in the middle of the midrange is kiss of phasey death, but I am minded of something told me decades ago - that it's bad enough getting a two way speaker to work properly, let alone a three way one. bringing this up to date with the poncy columns on sale, most of which having organ-pipe resonances and this "sounding off" being an excuse for bass (even the uber-expensive Wilson Benesch Act 1's did it at 60hz or so, although it was tamed somewhat by loads of bracing inside to interfere with the airflow).

Sorry of I've gone totally off the track here, but some pics and knowledge of what you actually use would be helpful..

[panos_adgr]

Hi Bernie! The granite receives the energy of the speaker better than the suspended floor and due to its big surface and mass releases the energy in the floor faster and this why you don't have remaining energy in the cabinet walls of the speaker. Now if you put spikes under the granite then you will make a mechanical ''insulation'' between floor and granite - speaker.That means that the energy of the cabinet will go in the granite mass and be absorbed only there and will not go in the floor. Now if you put granite on the floor and put the spikes under the speaker then you will make a mechanical ''insulation'' between speaker and granit-floor. This way you will have more solid speaker stand and will also reduce the boom effect and will clear mids and highs a bit. And finally you can put spikes under granite and under the speaker to have maximum results but all these are dependable on your speakers behavior, space interaction, and finally personal taste of each result. In any case before spending money in new speakers you have to experiment in the matters of speaker positioning in the room, then fine tuning them with spikes and granites or whatever and cables. Speaker position and support can make miracles in details sometimes.

Hope I was helpful (sorry for bad English sometimes)

[bobbasrah]

Interesting Panayotis,
Spikes are usually cited as coupling devices not insulating, although I have my own thoughts on that. However..

Bernie,
It may be that the bass boom is being created in the floor cavity and that the granite acts better to attenuate direct acoustic radiation into it, or it is perhaps increasing the mass of the cabinet slightly to alter it's resonance? It is doing something helpful to your enjoyment in any instance.

Could I suggest playing with some thick tap-washers, under the slab, and/or between the slab and speakers.....Cheap enough...

My own sand filled bases have small 4mm thick leather spacers between the spiked base and the cabinet and are very effective indeed. A rock solid platform off the floor containg absorbant mass....

[Canetoad]

Here is a picture. They are a set of Jaycar JV60 kit speakers that I built my own enclosures for. They use Vifa drivers.

http://img837.imageshack.us/img837/9115/20120222shit0177.jpg (http://imageshack.us/photo/my-images/837/20120222shit0177.jpg/)

[jandl100]

Granite slabs under speakers. Hmm. :hmm: I've tried that a few times with a few speakers and always end up unhappy with the sound. It seems it inevitably gives a kind of hollow sound in the mids and a thumpy bass when I've had a go. It sometimes takes a while to realise this ... I recall standing my SD1's on slabs for well over a month before I wondered why I wasn't enjoying my system so much any more --- HUGE relief when I took the bloody slabs away! :lol:

Nice, interesting looking speakers, there, Bernie! :)

[panos_adgr]

Interesting Panayotis,
Spikes are usually cited as coupling devices not insulating, although I have my own thoughts on that. However..

Bernie,
It may be that the bass boom is being created in the floor cavity and that the granite acts better to attenuate direct acoustic radiation into it, or it is perhaps increasing the mass of the cabinet slightly to alter it's resonance? It is doing something helpful to your enjoyment in any instance.

Could I suggest playing with some thick tap-washers, under the slab, and/or between the slab and speakers.....Cheap enough...

My own sand filled bases have small 4mm thick leather spacers between the spiked base and the cabinet and are very effective indeed. A rock solid platform off the floor containg absorbant mass....


Spikes are for decoupling. It happens because you reduce in the minimum (spike points) the surface that energy can be transmitted from one surface to the other. And coupling is when you remove the spikes and the touching surface is larger and energy is transmitted from on surface to the other. simple physics.

[jaym481]

Coupling is any interface that transfers the energy, and spikes couple, they don't isolate. The granite provides some isolation as it's a different medium than both the cabinet and the floor, and it's mass will damp vibrations somewhat.

A very knowledgable system set-up guy, Jim Smith, suggests using a rigid and heavy base, like the granite, but then isolating it from the floor (he suggests something like Herbies Gliders, so the whole assembly can be adjusted by sliding it). This method is particular to springy wood floors, and may not have the same result if applied to a concrete slab floor.

I'll likely be trying it over the next few months, as I have just moved from a concrete slab to a laminate floor.

[The Grand Wazoo]

I agree with Jerry on this - granite has never worked under speakers for me.

Turntables? Always.
Pre-amps? Usually (esp. valve ones).
CD players? Sometimes.

Those findings have been made on 3 different types of floors - suspended wood, concrete, solid wood over concrete floors.

[jandl100]

Yep, I've a concrete slab under my Pioneer tt. :thumbsup:

You've got me thinking, Chris - mayhap I should try some under my electronics! :)

[jaym481]

I have two spare slabs of slate. If the Home Secretary approves, I'm going to try them under my speakers. Not sure what to do between the slate and floor though, as I don't have anything handy. Maybe a bit of corrugated cardboard (again, subject to WAF).

[Canetoad]

Nice, interesting looking speakers, there, Bernie! :)

Thanks Jerry! They're now 14 years old so I must have done something right when I built them. :)

The fact that the granite makes such a big difference to the sound confirms that it's an area I should definitely be looking at for further experimentation. I'll be listening for a while more and I'll then remove them again and compare.

Next experiment may have to be an MDF platform with spikes coupling it to the floor to see what that sounds like. :scratch:

Thanks to everybody for their input. Very enlightening.