speaker query

[Paul Joppa]

So far this particular thread does not mention the SEXy speaker linked off the SEX amp page. This is still my recommendation for a budget approach with the SEX amp. The 6.5" Fostexes are around 96dB.

When we were looking at this, I tried a larger ported box with a FE167, designed with the increased Q due to a SET amp. This allowed it to get deeper in the bass than the standard Fostex ported design, so it was a fullrange design with no external bass augmentation (no subwoofers). In the end we didn't like the excursion-limited bass, and went with the SEXy design instead, but some people might be happy enough with it - a non-audiophile insisted on buying the prototypes from me even after I explained why I didn't like them.

There is an open-baffle 2-way design floating around using the 4" Fostex as tweeter with a high-efficiency 12" woofer, that is said to sound pretty good. I have not run across one yet, but the design is well explained on the web and a similar design could probably be make using one of the 6.5" Fostex drivers, for greater efficiency.

[denti alligator]

I went ahead and got those Klipsch Reference 61s, which were on sale at Crutchfield, so if I didn't like anything about them I knew I could return easily. I'm not up for building right now, so the SEXy speakers are out. The single-driver Tektons are the only under $500 and I was concerned about them being too "dark."

These Klipsch definitely don't have that problem. They sound really open and clear. Bass is fine.

The only thing I'm surprised about is how much I have to turn the volume pot to get them going really loud. I realize the sensitivity is still a couple db under what is desired (they're at 95db), but I figured moving from my 89db Paradigms there would be a dramatic difference. There really isn't. I've got to get it up to well over 50% to get them nice and loud. Granted, I now have them in a different place in the same room, about 10 feet away, where the old ones were only about 2 feet away. Still...

[2wo]

People put too much into the position of the pot. This is an issue if the first click is too loud, or all the way up isn't enough. You can read Paul's white paper on the subject, if you want all of the gory details but the short version is. If you can adjust the pot as low as you want and as loud as you want, without hitting a stop and the 2 points are not too close together . you're good to go...John   

[denti alligator]

I wouldn't have thought anything of it, if it weren't for the comparison with the other speakers. I thought 3db difference in sensitivity was comparable to double the power; 6db difference to quadruple the power.

The 50% point on the 89db Paradigms is not much different than the 50% point on the 95db Klipsch. I found that odd. You're saying there's nothing odd about it?  If so, that's good, I guess.

[Doc B.]

Along with the sensitivity you also need to factor in the impedance of the speaker. There may be differences that help to account for some of the reason output levels seem closer than they should, for example if the more sensitive 8 ohm speaker is more on the 10 or 12 ohm side and the less sensitive one is more on the 6 ohm side and both are playing from the 8 ohm tap.

[denti alligator]

Thanks. I need an embarrassed emoticon for what's to follow. I'm woefully ignorant in this area, so please forgive me.

So the SEX amp outputs 2 watts per channel, right? Is that dependent on the volume level? The speakers can output up to 150 watts. With the SEX I'm assuming I'm outputting more than 2 watts. What's the equation that explains how this works? The factors are watts in; impedance; sensitivity; and watts out, no? [/ducks with embarrassed look]


Let me add another question: what exactly am I missing out on by using speakers with less than the recommended 97db sensitivity? Is it just a question of loudness, or is the quality of even low-volume music affected?

[Grainger49]

Sam,

I should have waded in last night but didn't.  As long as you are getting a satisfying volume and don't hear distortion you are fine.  The position of the volume control really doesn't matter (mine are almost all the way open).

The power is probably specified as 2W at a nominal 8 ohm load.  The output transformer will deliver the specified power into each load as you change the taps for the speakers.  Here is where it goes screwey, an "8 ohm" speaker might be 8 ohms at three maybe four places in its impedance curve.  At other frequencies it might dip to 3.5 ohms and at resonance it might hit 45 ohms.  So the 8 ohm tap produces 2 watts maximum at some frequencies.

SET amplifiers are known to react with the speaker impedance curve and therefore there are speakers known to be SET friendly.

You probably don't get to 2W listening anyway.  As I said when I started, if it sounds good and gets loud enough you are fine.

[denti alligator]

Thanks. I'd still like to know if it's just loudness that would distinguish using a >98db speaker over a <98db speaker with the SEX amp.

[Doc B.]

If the only criterion you are considering is sensitivity then yes, a <98 dB speaker will simply play louder at the same volume setting than one that is >98 dB as long as they are both of the same impedance and playing from the same output tap.

[Grainger49]

My guess, educated a bit, would be that you know the answer.  You said, "Granted, I now have them in a different place in the same room, about 10 feet away, where the old ones were only about 2 feet away."  We all know that sound dissipates with distance.  

Take that into account and that the manufacturer's specs might be a little off, that might account for the volume setting difference.

Doc posted while I did, to add to his statement, the speakers would have to be in the same place in the room and you in the same listening position.  Moving either the speakers or the listener changes everything. 

[denti alligator]

Thanks. I put the old ones right on top of the new one and switched back and forth. They are only slightly (very slightly) quieter.

But the Klipsch are so far superior that it hardly matters. Anyway, I'm rarely going to turn the volume higher than 75%, and when I do want to I hope by then to have purchased the Heresys.

[Japhy]

I'd go for a set of used Herseys.  I'm using a set of Forte's in a modestly larger room and they sound absolutely wonderful at pretty respectable sounds levels I may add.  A used set of the small Herseys can be had for a reasonable price, and if you're into DIY'ing you can tinker with the crossovers to replace the old caps.....fun all around!

[denti alligator]

Ok, so I ended up finding a used pair of Forte IIs with upgrades all around. Had to drive 2+ hours and the deal wasn't stellar, but these speakers are definitely in a different class and are a much better match for the SEX: 99db sensitivity, for one, plus much better bass. I'm hoping upgrading the irons on the SEX will improve bass even more. These are pretty sweet speakers.