Seeking freq curve/response info for SVT

[Testing_123]

Can anyone point me to some typical frequency response data for Ampeg SVTs?

They clearly have a characteristic tonal "punch" and "oomph" (technically speaking...). Where on the EQ range does that signature baseline tone come from? What makes a cranked SVT sound like an SVT?

[JimmyM]

check out bass gear magazine's issue 4...they dissect a 74 svt.

[KramerBassFan]

IMHO, the SVT sound is a combination of things, not just its EQ range.

The big transformers, six 6550's, the Preamp, so on.

But good luck!

[seamonkey]

Google: SVT impulse response
And pick up a convolution that will let you play through these.

Many choices from commercial Peavey Revalver down to Voxengo Boogex for free.
Or just go for Ampeg SVX which is selling for $100 until the end of the month.

Keep in mind that for all impulse libs and modelers have a "Gold Stardard" to sample from problem. You're going to read reviews of how players claim a modeler doesn't sound like their own amp. Go to a store and try a couple SVT's and see if they sound the same next to each other. Which gold standard should companies who sample the ideal amp use?

[tombowlus]

Originally Posted by JimmyM

check out bass gear magazine's issue 4...they dissect a 74 svt.

Here, I'll make it easy for you!

Issue #4 - the Ampeg Issue

[Stompin Tom]

Originally Posted by tombowlus

Here, I'll make it easy for you!

Issue #4 - the Ampeg Issue

Thanks! Fun read.

[Hoover]

Originally Posted by KramerBassFan

IMHO, the SVT sound is a combination of things, not just its EQ range.

The big transformers, six 6550's, the Preamp, so on.

ime it's the reciprocal combination of a head that's voiced oddly thin on the very bottom end with a speaker cabinet that has gobs and gobs of low end...disproportionately more than would ordinarily be deemed necessary. (If you've ever played an SVT head through someone else's cabinets, or vice-versa, this becomes surprisingly clear.)

But man, put those two together (SVT head + SVT cab) and it's magic! Bwana Dik speaks, the heavens will part!

[JimmyM]

Originally Posted by Hoover

ime it's the reciprocal combination of a head that's voiced oddly thin on the very bottom end with a speaker cabinet that has gobs and gobs of low end...disproportionately more than would ordinarily be deemed necessary. (If you've ever played an SVT head through someone else's cabinets, or vice-versa, this becomes surprisingly clear.)

But man, put those two together (SVT head + SVT cab) and it's magic! Bwana Dik speaks, the heavens will part!

it's actually the reverse, hoov. the cab rolls off at around 55hz and the head has a big low end.

short version...set flat, an svt head has a big low end culminating in a large hump between 100 and 125 hz, then it has a gradual rolloff of everything else above that in almost a diagonal line. you can flatten it out with eq if that's your thing...personally i think my flat settings sound more flat than bass gear's bass 11:00, highs 2:00, mids 3:00 @ 800hz. that hump might make some think that the lows are rolled off, but they're there, just not as prominent. but yes, bwana dik does speak no matter how you set it!

[Hoover]

Originally Posted by JimmyM

it's actually the reverse, hoov. the cab rolls off at around 55hz and the head has a big low end.

I don't (necessarily) doubt the cab rolls off @ 55Hz, but what I've found every time I connect a non-SVT head to an SVT 8x10 cab is that I have to dial back my lows and add more mids & highs than I ordinarily with those non-SVT heads into non-SVT cabs...which leads me to believe that the low end on the SVT cab is disproportionately louder than the mids & highs.

The SVT head thing we've discussed before: Jim Williams of Audio Upgrades (an audio engineer whose client list would make most of us on TB spooge, and a bassist as well) has gone on record claiming the frequency response of a 1970s SVT preamp is dramatically attenuated below 80Hz, and I've never heard (nor seen) anything in my years of playing with SVTs to make me question his claim. Plug an SVT head into a BagEnd or Hartke cabinet and then see where you need to set the bass control to get the same monster low end that it had with an SVT cab; ime you'll need to add ~6dB boost on the bottom to make up for the rolled-off response of the SVT electronics and/or the bass-heavy response of the (missing) SVT cab.

[greenboy]

Could just snoop around on BFM's forum, where one version has been shown in graph form for years now. I've seen FR graphs when googling too.

[Alex1984]

I found my SVT to have a lot of low end as well, although the low-mid hump kinda makes it feel rolled off. Jimmy, I think your settings will be a bit more edgy than flat, but that's pretty much how I EQ mine.

Hoover, judging from what you wrote, I'm guessing you might've gotten some of the late SLM cabs with the really dark speakers?

[lem8r]

Originally Posted by Hoover

ime it's the reciprocal combination of a head that's voiced oddly thin on the very bottom end with a speaker cabinet that has gobs and gobs of low end...disproportionately more than would ordinarily be deemed necessary. (If you've ever played an SVT head through someone else's cabinets, or vice-versa, this becomes surprisingly clear.)

But man, put those two together (SVT head + SVT cab) and it's magic! Bwana Dik speaks, the heavens will part!

Maybe because SVT cab is sealed and other cabs were ported?

[JimmyM]

Originally Posted by Alex1984

I found my SVT to have a lot of low end as well, although the low-mid hump kinda makes it feel rolled off. Jimmy, I think your settings will be a bit more edgy than flat, but that's pretty much how I EQ mine.

depending on the amp and the tubes in it, it can be edgy. and i do back off the mids slightly to cut that down a bit. but i matched it up with my markbass lmii as best i could, and it had near flat response when nooned, and that's what i got in mine.

Hoover, judging from what you wrote, I'm guessing you might've gotten some of the late SLM cabs with the really dark speakers?

word.

[Hoover]

Originally Posted by Alex1984

Hoover, judging from what you wrote, I'm guessing you might've gotten some of the late SLM cabs with the really dark speakers?

Almost all of my experience with SVTs is with silver/gray grillclothe units from the 1970s...does that correspond to the "late SLM" (St. Louis Music, I presume) period?

[Alex1984]

Those should be the 70s cabs, which I personally found to be punchy and a little bass shy compared to modern cabs.

[JimmyM]

Originally Posted by Hoover

Almost all of my experience with SVTs is with silver/gray grillclothe units from the 1970s...does that correspond to the "late SLM" (St. Louis Music, I presume) period?

it doesn't, of course...you knew that but most people don't think of those cabs that way, especially old ones.

[lem8r]

Originally Posted by lem8r

Maybe because SVT cab is sealed and other cabs were ported?

Here is my assumption. Ported cab has higher impedance spike in low end than sealed one. It is transformed in to higher than usual load to output tubes. Than than higher load is shunted by inductance of primary windings which cause loss of output in that freq region. Of course gnfb can help, but in tube amps it is not 'deep' enough and with some cabs we can hear the difference.

[Calaverasgrande]

I have always found svt cabs to be a bit lean on the low-low end and the upper mid/treble. The typical SVT tone to me is LOTS of low mid, and a bit shy in the sub low.

There is also that the eq on the svt is very unconventional. At least on the older SVT the mid is based around a massive inductor. Like 5-10lbs! This undoubtedly is the source of the svt "thickness". No other mp I know of is built like that. I alo wonder if the newer models use a gyrator circuit to save money.

[lem8r]

Originally Posted by Calaverasgrande

I have always found svt cabs to be a bit lean on the low-low end and the upper mid/treble. The typical SVT tone to me is LOTS of low mid, and a bit shy in the sub low.

There is also that the eq on the svt is very unconventional. At least on the older SVT the mid is based around a massive inductor. Like 5-10lbs! This undoubtedly is the source of the svt "thickness". No other mp I know of is built like that. I alo wonder if the newer models use a gyrator circuit to save money.

that toroidal inductor mounted inside the preamp board, it is not looking to weight as much.

[Arjank]

Originally Posted by lem8r

Here is my assumption. Ported cab has higher impedance spike in low end than sealed one. It is transformed in to higher than usual load to output tubes. Than than higher load is shunted by inductance of primary windings which cause loss of output in that freq region. Of course gnfb can help, but in tube amps it is not 'deep' enough and with some cabs we can hear the difference.

The impedance spike is not necessarily higher then that of a closed cab. A ported cab has actually two spikes, one under and one above the Fb. You can smooth out the 2nd impedance peak with an LCR.