Redesign a factory speaker

[sazaks]

I own a pair of Quest Q610 (Canadian Brand...JBL Drivers) 2 way bookshelf speakers.
http://www.futureshop.ca/catalog/pr...-web2&biasid=Q81UXFUJ3NVQ8LMK9MEJH9SGAV4X1FF5
I am quite satified with the sounds quality but I would like to know if there is room for improvment? Can we improve the sound of a factory set of drivers by redesigning the inclosure using better materials? Or is this a waste of time?

 

[Super]

Redesigning a relatively simple enclosure can definitely be worthwhile. You have the option of adding additional bracing or materials to the enclosure, thereby reducing resonances. It also enables you to change stuffing density, and vary port lengths to tune the speakers to your liking.

 

[sazaks]

Redesigning a relatively simple enclosure can definitely be worthwhile. You have the option of adding additional bracing or materials to the enclosure, thereby reducing resonances. It also enables you to change stuffing density, and vary port lengths to tune the speakers to your liking.

Where do I start? (materials, enclosure design) Any information would be greatly appreciated. I have an extensive knowledge of woodworking and building materials but a very limited knowledge of speaker knowhow!

[Edited by sazaks on 11-13-2001 at 03:39 PM]

 

[Æ]

Best thing is to identify the..

Weaknesses of your loudspeaker first. Then go about fixing them. Don't automatically think that each and every change will make it sound better. What is it that you don't like about your loudspeakers? Or what seems to sound wrong to you? Attack the problems, otherwise you might end up being more dissatisfied.

 

[walker]

Sazaks, I don't know what experience you have with speaker building already. I would highly recommend that you read as much as you can before diving in. If you do open 'em up make sure that you seal them up well, very important with ported designs!
There are many changes that can be made, some that are simple like hard wiring, (soldering) the drivers with heavy gauge wire, trimming inductors or replacing iron core with air core and remounting them to reduce any cross coupling and replacing capacitors with better types and tighter tolerances.
Some will argue that some of these upgrades are inaudible but few will argue that they can degrade the speakers. Cheaper speakers benefiet most from these tweeks.
More complex upgrades, like changing drivers and boxes should not be done without considerable research. If you realy want to try new enclosures probably best to retain the original internal dimentions and use thicker MDF.
Regards WALKER

 

[sazaks]

Re: Best thing is to identify the..

Weaknesses of your loudspeaker first. Then go about fixing them. Don't automatically think that each and every change will make it sound better. What is it that you don't like about your loudspeakers? Or what seems to sound wrong to you? Attack the problems, otherwise you might end up being more dissatisfied.

The main problem I have with these loudspeaker is resonance...what causes it and how do I go about fixing it? Should I be building new boxes with thicker material and then stuff if with egg crate foam? How do I approch this problem?

 

[walker]

Sazaks, at what frequancy is the resonance? Could it be room induced?
Regards WALKER

 

[Æ]

RESONANCE,

You need to run a series of test tones through your system then you will be able to identify any resonance and where it is comming from.
Stiffening/reinforcing an enclosure will eliminate some resonance, and adding a compliant mass type of damping material, such as a DYNAMAT (peel and stick) to the insides of the walls will help even more. Sometimes a woofer frame or the metal can magnetic shield will resonate also. So apply damping material to the woofer frame will fix that.
Also some combinations of crossovers and electronics or speaker cables will not get along well, and can resonate. Running a sweep of test tones will reveal that also, right through the crossover region.

 

[walker]

Another quick thought, ported speakers are DESIGNED TO RESONATE at the port frequency, (I hope this comment doesn't offend reflex lovers). I prefer closed boxes, (heavily damped big ones).
Regards WALKER

Lookout, incoming!

 

[sazaks]

Re: RESONANCE,

You need to run a series of test tones through your system then you will be able to identify any resonance and where it is comming from.
Stiffening/reinforcing an enclosure will eliminate some resonance, and adding a compliant mass type of damping material, such as a DYNAMAT (peel and stick) to the insides of the walls will help even more. Sometimes a woofer frame or the metal can magnetic shield will resonate also. So apply damping material to the woofer frame will fix that.
Also some combinations of crossovers and electronics or speaker cables will not get along well, and can resonate. Running a sweep of test tones will reveal that also, right through the crossover region.

Thanks for the great info!!! Now one last question!!! If I wanted to build a new enclosure, could I change it's shape while keeping the same volume (i.e. wider and not as deep). How would this affect the sound?

 

[walker]

Changing the dimensions and keeping the volume the same will change the box resonances. If you build a cube you'll end up with only one box resonant frequency, but it'll be a BIG one! Some recommend keeping to the golden ratios, (1.618:1:0.618).
It seems to me that you may be better off building new ones and leaving your speakers as they are. The drivers aren't that expensive and if you do build new enclosures for your old drivers you may well end up with worse resonances! The speakers may also need changes to the crossovers.

Regards WALKER

Sorry for raining on your parade.

 

[Æ]

Only one way to know for sure.

Try it and see for yourself.
Changing the width or height of the front baffle will cause a change in frequency of the baffle step. Also known as cabinet diffraction loss. I can't explain it all to you. Go to:
http://www.trueaudio.com/st_diff1.htm