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Old 1st June 2007, 06:30 AM   #1
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Default Upgrade X250.5 to X350

Hello all,

I am new here and would like some help from this friendly forum. Ideally if Mr. Nelson Pass can reply that would be ideal, but others are welcomed too if they have personal experiences related to my question.

I currently have a Pass Labs X250.5 driving a pair of Von Schweikert VR-4 SRs in a room size roughly 20'L x 17'W x 8'H. The speakers are 92 db sensitive, the bass cabinent are 4ohms nominal. I sit about 10' away from the speakers, I assume this would be far-field listening. Although I won't call the X250.5 weak for my speakers, but some how I feel I am missing out on some bass output from my VR-4 SRs. They have twin 8.5 inch bass drivers and I feel I should be feeling more bass impact not just hearing it. If I upgrade to the older X350, will I get more bass output since it has more wattage in 8 and 4 ohms respectively. Right now the X250.5 is providing 250 watts at 8 and 500 watts at 4 ohms. The X350 would give me 350 watts at 8 and 700 watts at 4 ohms, will that help and provide stronger bass output? If it does provide stronger bass output with the bigger X350, what qualities would I lose by switching from X250.5 to the older but bigger X350? Also would I enjoy more Class A watts by getting the X350 vs. the X250.5 ?

Thanks in advance.
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Old 1st June 2007, 08:04 AM   #2
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Although I am far from being NP, I will try to answer your question, because I know both amps verly well.

Turning an X250.5 into an X350 isn't an upgrade but a severe downgrade in terms of sound quality. The .5-series features a lttle bit of "single ended class A feeling", because it is that what it does at low output levels. I have experienced the X250.5 as definitely more open, subtle and faster then the older models, and the differences are not too small. I would never give up those advantages for more power.

Second, it is hardly possible to turn an X250.5 into an X350 (or an X350.5, which would be more useful). You'd need more output devices, more heatsinking and a bigger power supply, which wouldn't fit the 250 cabinet.
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Old 1st June 2007, 08:19 AM   #3
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Quote:
Originally posted by cuttingedge168
VR-4
Just out of curiosity: you own 1st ed. VR-4s or the updated ones ?
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Old 1st June 2007, 02:13 PM   #4
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Default Upgrade X250.5 to X350

Hi HBarske ,

Thanks for your response. Just to clarify, when I mean upgrade I meant to buy another amp, in my case I was asking whether I should buy an X350 and sell my X250.5. I am seeking more bass output as I feel the Von Schweikert VR-4 SR's twin 8.5 inch aluminum woofers should be providing more bass output than it currently is with the X250.5. I am thinking (out loud) perhaps the 4 ohm load on the bass cabinent requires a little more power wattage to make the bass drivers come alive.

I got the mark one edition of the VR-4 SR Gen IV.

Thanks guys.
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Old 1st June 2007, 02:42 PM   #5
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I wouldn't expect 8.5" drivers to fill a room that size with chest-pounding bass. You may be blaming the amp for something that's not its fault.

Grey
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Old 1st June 2007, 05:42 PM   #6
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Default Upgrade X250.5 to X350

The VR-4 SR has two 8.5 inch woofers per side and can go as low as 20Hz per manufacturer, and speaking with other VR-4 SR owners, some measure even 18Hz in their larger room than mine. But they use a Class D amp rated at 500 watts at 8 ohms (1000 watts at 4). So definitely the speakers can produce strong powerful pass, but perhaps require matching it with the correct amp that can drive these woofers with authority??? I am an old school guy, and like the conventional huge looking amps with huge power supplies (big transformers and capacitors). Not into these new flimsy looking Class D amps, perhaps they do perform well, but it's not my cup of tea, so I would like to buy a conventional amp for my application.
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Old 1st June 2007, 08:00 PM   #7
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As I recall, those are the SEAS drivers on the bottom, and as
a breed they do indeed go quite low.

I suppose it's possible that an X350 could work better for you,
but I think you would definitely want to try it (and other amplifiers)
before making a commitment. I doubt that it's actually a wattage
issue, but a control/tonality issue. Usually the complaint will
revolve around attack characteristic - aka punch.

Placement is also a big issue here, and I assume that you have
tried moving the speaker around, checked the wiring phase, etc.

By the way, try wiring the speakers out of phase (I seem to
remember they are bi-wirable) or checking the phase of the
woofers with a D cell. Occasionally stuff does get mis-wired.
In otherwords, play around with the system and see what you
get.

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Old 1st June 2007, 08:59 PM   #8
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Thanks Nelson and others for taking time to respond.

I actually played around with the placement of the speakers and have come to the best position for them, currently about 9 feet apart from each other, 3 feet from the side walls and 4.5 feet from the front wall and I sit about 10 feet from the front tweeters. At this point with the X250.5 I do get bass, but just not as much as I would like especially with these good sized aluminum drivers. I am looking for a thump in my chest, or that "moving impact" type bass that can be felt like as if I was in a live performance or small jazz club.

How do I wire the speakers out of phase? Do you mean connect the right speaker to the left channel of the amp and left speaker to the right channel of the amp?
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Old 1st June 2007, 09:33 PM   #9
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Ah, but the question is...20Hz at what SPL?
The implied question is how loud are you wanting to listen and to what kinds of music?
There's a difference between low and loud.
Louder? Yes, more wattage will help. Deeper? That gets more complicated.
Something that frequently gets lost in the shuffle is that the "feel it in your chest bass" in the impact sense isn't really all that low; more like 60-80Hz. That's something you get lots of at a rock concert, for instance, even though there's almost nothing below 50Hz from an average PA system. 20Hz is good for flapping pants legs, but not so much like getting punched in the chest.

Grey
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Old 1st June 2007, 10:00 PM   #10
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Quote:
Originally posted by cuttingedge168
At this point with the X250.5 I do get bass, but just not as much as I would like especially with these good sized aluminum drivers. I am looking for a thump in my chest, or that "moving impact" type bass that can be felt like as if I was in a live performance or small jazz club.

How do I wire the speakers out of phase? Do you mean connect the right speaker to the left channel of the amp and left speaker to the right channel of the amp?
Like I said, what you're looking for is a coherent attack, and
assuming that the speaker is flat, usually the problem is phase
relations down in the 100 Hz or so region.

Now I haven't heard the VR4's, so I have no basis for comment
as to what we should expect. It's possible that Albert's crossover
doesn't do what you are looking for, but it's unfair to start with
that assumption.

It is, however, a common problem, particularly when you mate
woofers with electrostats or full range drivers.

So first off, some experimentation is in order. If the VR4's are
bi-wirable then you have access to the woofers and mid/hi
separately, so you are in a position to try flipping the phase,
+ for - on the input terminals. Try flipping the phase of both
woofers at once, then one woofer at a time - left and then right,
then put the woofers backto normal and flip the mid/hi phase
one at a time, left and then right.

This makes for 5 different sounds plus the original.

Note what sound you get for each setting. Is there any setting
that sounds better than what you had?

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