I have built a pair of towers using vintage drivers I salvaged from beat EPI-400 speakers. They turned out really nice and sound pretty good overall, but bass is a little weak/undefined at lower frequencies. I suspect they could benefit from a little effort at fine tuning them, but I would like to take semi-educated guesses at what might be best to try. Hoping to pick the low hanging fruit first.
Relevant clues that some modifications are necessary:
Relevant clues that some modifications are necessary:
- Woofers bounce a at high volume.
- There is fairly significant cabinet vibration while they're playing.
- These are 6" woofers and they unfortunately do not have any thiele/small information published about them.
- EPI didn't build any double 6" woofer speakers so I went through some extremely exact math (wink wink) to determine internal volume. I determined the percentage change in volume between a single 8" woofer EPI two-way to a double 8" woofer EPI two-way, and applied the same percentage change to single 6" woofer model from their line-up. End result was a 3600 cu. in. enclosure before bracing, I think ~3400 after. For reference the quadruple 6" woofer EPI-400 these came out of was ~5000 cu. in.
- The speakers are built out of 3/4" MDF, have internal bracing front-to-back and side-to-side, and are stuffed with fiberglass.
- The surrounds are original butyl surrounds. They are not that particularly stiff or cracked.
- Polarity has been double and triple checked
- I have messed around with placement some as well. They do better against the wall than they did away from the wall (like in the below picture), I've also found they're fairly directional speakers. Bass is definitely improved when you're dead center and near the back wall.
- Decrease internal volume
- Increase quantity of bracing, though would have to get creative with this since their are fully veneered now
- increase/decrease quantity of stuffing. Amount/compactness of fiberglass is in line with other sealed enclosures I've seen
- New surrounds
Add a lot of removable weight on top, initially at least as much as they weigh and go from there if need be to mass load them to quell vibration, the need for more bracing before doing anything else as you may find the bass much improved. Best to perch them on a massive plinth also to further load them to the room.
FWIW I used potted plants when there was a S.O..
FWIW I used potted plants when there was a S.O..
This is purely technical, and not necessarily a solution to your question.
With an average to small sealed enclosure >
1. If you had plenty of power to spare, adding a series power resister of say 6.8 ohms will increase the audible bass output at the resonant frequency.
( this doesn't really address bass extension, and I see you don't have a powerful amp. )
2. Adding some mass to the cone (centrally around or on the 'dust cap') will lower the resonant frequency and add bass extension. (strong epoxy glue)
3. Adding volume to the enclosure will also add bass extension.
I would say, finding the right amount of 'internal stuffing' and using your Bass control is actually your best solution 🙂
With an average to small sealed enclosure >
1. If you had plenty of power to spare, adding a series power resister of say 6.8 ohms will increase the audible bass output at the resonant frequency.
( this doesn't really address bass extension, and I see you don't have a powerful amp. )
2. Adding some mass to the cone (centrally around or on the 'dust cap') will lower the resonant frequency and add bass extension. (strong epoxy glue)
3. Adding volume to the enclosure will also add bass extension.
I would say, finding the right amount of 'internal stuffing' and using your Bass control is actually your best solution 🙂
Yeah, if the EPI400 had 4 woofers and you only use 2 and keep the same crossover, the 'cutting point ' would change.
I don't mean to be 'snooty', but mentioning the crossover network really has little to do with low frequency performance >
that is unless there is a very low-quality/lossy inductor driving the woofers 😕
that is unless there is a very low-quality/lossy inductor driving the woofers 😕
SILLY ME >
Of course, 'taming down' all or some frequencies above the bass using XO tailoring WILL effectively increase the bass output.
Of course, 'taming down' all or some frequencies above the bass using XO tailoring WILL effectively increase the bass output.
The appropriate volume for a pair of the 6” woukd be half the volume of the 400.
38" x 14" x 14” with ¾” material, no bracing > 93 litre, so 46.5 litre for your MTM.
The XO on all the EPIs of this generation was a single cap onthe tweeter.
dave
Note: the woofers really benefit from puzzlekoat/ModPodge.
38" x 14" x 14” with ¾” material, no bracing > 93 litre, so 46.5 litre for your MTM.
The XO on all the EPIs of this generation was a single cap onthe tweeter.
dave
Note: the woofers really benefit from puzzlekoat/ModPodge.
This
Many threads talking about this...
First the tower...
The concept is to better the (sonority of) bass. First you have to exclude the contribution to overall sound of the back wave, which is the error signal. More chaotic & random signals ( not if analyzed with FEM!) are imparted to the structure by the mechanical forces generated by the moving parts.
Now, the gravity attracts this body to the floor, the residual analysis I'll leave it to you...
How do their sound compared to those ADS (either L710 or L810) speakers next to them? Those ADS speakers are also closed enclosure system. I used to listen to the L810 once, and I thought their bass response was decent enough.
You can measure the T/S parameters yourself. Then you will be able to assess how close you are to having an optimum enclosure. Hopefully you can then convert your existing volume into a bass reflex.
First off, thank you all for the replies!
Crossover, an obvious component I forgot to mention, d'oh!. These are not wired the same as the 400's were. All the early 70's EPI speakers had very simple crossovers. It's my understanding that Burhoe intended for the woofers to be "full range", so the crossover in most of the speakers only consisted of a capacitor acting as a high-pass for the tweeter. Some models included a couple resistors and a switch for tweeter control, which I threw in for giggles, but the switch is left in normal mode. Wired as such (the caps are the Dayton polypropylene):
Looking on HumanSpeakers a little bit just now it would appear that some of the double "module" EPI speakers such as the Epicure 20+ also had inductors, This Would an inductor potentially affect things here?
----------
To make sure I'm understanding: you're suggesting to mass load them externally as a means of checking whether or not more internal bracing will help? Basically: if added mass improves things = more bracing likely will too?
----------
I would definitely like to leave the crossover as close some original EPI variety as possible. I know I very much like the EPI sound and would otherwise like to approximate that as much as possible with my little experiment here. #2 seems difficult to do precisely and also non-reversible, Regarding #3, isn't there a point of diminishing returns with cabinet volume? I only have at best a passing familiarity with all the parameters in speaker design, but couldn't a too large enclosure negatively affect the "springiness" of the air and lead to excess vibration and/or the over extrusion I mentioned? I'm already well over 50% the volume of the 4 woofer EPI-400 so that's why I was thinking eating up some more volume might help.
----------
I'd been lusting after getting to try some 710's for a while and paid a pretty penny for these. Overall I'm actually fairly dissapointed in them. Compared to my mini-towers they're definitely louder and more balanced in the low end, but they're also fairly muddy down there. The towers have much more clarity to the bass articulation.
Crossover, an obvious component I forgot to mention, d'oh!. These are not wired the same as the 400's were. All the early 70's EPI speakers had very simple crossovers. It's my understanding that Burhoe intended for the woofers to be "full range", so the crossover in most of the speakers only consisted of a capacitor acting as a high-pass for the tweeter. Some models included a couple resistors and a switch for tweeter control, which I threw in for giggles, but the switch is left in normal mode. Wired as such (the caps are the Dayton polypropylene):
Looking on HumanSpeakers a little bit just now it would appear that some of the double "module" EPI speakers such as the Epicure 20+ also had inductors, This Would an inductor potentially affect things here?
----------
To make sure I'm understanding: you're suggesting to mass load them externally as a means of checking whether or not more internal bracing will help? Basically: if added mass improves things = more bracing likely will too?
----------
I would definitely like to leave the crossover as close some original EPI variety as possible. I know I very much like the EPI sound and would otherwise like to approximate that as much as possible with my little experiment here. #2 seems difficult to do precisely and also non-reversible, Regarding #3, isn't there a point of diminishing returns with cabinet volume? I only have at best a passing familiarity with all the parameters in speaker design, but couldn't a too large enclosure negatively affect the "springiness" of the air and lead to excess vibration and/or the over extrusion I mentioned? I'm already well over 50% the volume of the 4 woofer EPI-400 so that's why I was thinking eating up some more volume might help.
----------
I'd been lusting after getting to try some 710's for a while and paid a pretty penny for these. Overall I'm actually fairly dissapointed in them. Compared to my mini-towers they're definitely louder and more balanced in the low end, but they're also fairly muddy down there. The towers have much more clarity to the bass articulation.