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Adding a Sub to a SET amp system


David Pritchard

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First, thank you for giving me the courage to rediscover Klipsch speakers. My system is as follows: Marantz Sa11S1 cd player directly into an Art Audio PX-25 amp (with volume control). Speaker wires go to the Klipsch KLF-25 towers ( with Bob Crites crossovers and his titanium tweaters). So I have no level line out or tape monitor input- output. The sub will have to accept speaker wire input and have to have speaker wire outputs. I talked directly to Velodyne- they no longer sell a sub that will accept the speaker wire as an input and then out put to the Klipsch's. I listen only to 2 channel music not home theater. I am currently making do with a 12 year old Infinity BU-2 12 sub. Any thoughts on a tighter better sub? My room- office is 17x13x12 with a cathedral ceiling.

Price range $500.00 to $1500.00 hopefully used on Audiogon.

Thank you for your expertise.

David Pritchard

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  • 2 weeks later...

"I talked directly to Velodyne- they no longer sell a sub that will accept the speaker wire as an input and then out put to the Klipsch's."

I don't know who you talked to at Velodyne, but they told you wrong. I use two Velo DLS4000R subs with my two-channel rig. They have speaker level inputs and outputs. There are so many Velodyne subs, I can't say for sure which ones do or don't have speaker-level connections, but I know mine do and I think all the DLS-R and the new DEQ-R lines do. Many SVS subs do too.

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Did you mean KLF-20 and not KLF-25? I'm not aware of any 25 version...

Also,
what are you hoping to accomplish with the subwoofer? It seems to me
like most SET users aren't a huge fan of bass...and certainly not bass
that is typical of an undersized box sub.

Also, the speakers
outputs from most every sub with speaker level inputs are just going to
be full-range....which proves to be problematic when properly
implementing the crossover to the sub. In other words, if you have the
KLF-20, then you'll be wanting to use around a 30Hz to 40Hz lowpass
filter to the sub, but I'm not sure if that's going to satisfy your
desires because I'd wager the SET amp probably has a harder time
driving the KLF-20 at around 100Hz to 150Hz where there should be the
first impedance minimum...in which case, you might be wanting the sub
to help cover that range, but it'll be hard to do unless you can high
pass the mains...

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At least some models in Velodynes DLS-R line have selectable 80/100Hz 1st order high-pass filters on their speaker-level outputs. On their DEQ-R series, it is fixed at 120Hz. I'm not sure of the slope on those.

At least one Parts Express plate amp has a high-pass filter on it's speaker-level outs. I'm not sure of the model number but it is rated at 240W and is supplied with their 10" Titanic III sub.

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Hmmm, I'm surprised by that actually....a high pass filter in that application is going to be at a different frequency depending on the impedance of the speaker. Going from a 4 ohm to 8 ohm speaker will shift it up an octave. Also, the impedance response of the speaker isn't flat...so the xover point is going to change with frequency (it moves higher with increasing impedance).

That should produce some exciting results near the low-end of a speaker where the impedance is going all crazy style. It'll effectively make it steeper initially, which I suppose is ok, but the starting point is going to be within an octave or so...

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Thanks to all who have participated in this thread. The speakers are the KLF-20's. Concerning the Velodynes, I talked to Curt(Kurt) in customer support. He is 72 years old and said he knew Paul Klipsch(" as he has been in the audio world for years"). He was not helpful and said that a Velodyne would not work. Since the old Infinity 12 inch BU-2 is an improvement in my listening enjoyment, I have ordered the new SVS 12 sub (to be released in November). It will accept the speaker outputs from the amp and also has high level outputs to the main speakers (the KLF-20). It also can be returned if I do not like the sound. I will post a follow up after installation and evaluation.

David Pritchard

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Hmmm, I'm surprised by that actually....a high pass filter in that application is going to be at a different frequency depending on the impedance of the speaker. Going from a 4 ohm to 8 ohm speaker will shift it up an octave. Also, the impedance response of the speaker isn't flat...so the xover point is going to change with frequency (it moves higher with increasing impedance).

That should produce some exciting results near the low-end of a speaker where the impedance is going all crazy style. It'll effectively make it steeper initially, which I suppose is ok, but the starting point is going to be within an octave or so...

Yup. The literature with my two Dayton Titanic 10" powered subs that I use in my HT room mention that the speaker impedence will affect the hi-pass filter.
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It is a good looking amp that really makes the Klipsch speakers sing. The SVS sub should ship in November- it is their new 12 inch model. It certainly a lot of fun listening to music with one watt of power. Of course there are 5 more watts in reserve should the need arise!

Back to the music- best wishes for a joyous weekend.

David Pritchard

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