sub wiring question

i just bought 2 SPL Velodyne sub ,im using them for 2 chanel music , the sub has SPEAKER LEVEL INPUT and RCA LEVEL INPUT , im using A308 cr musicalfidelity power amp , my amp has rca output , so my question is which way should i connect between SPEAKER INPUT or RCA INPUT , could you guys tell me which way the best for my sub , and without
affecting the performance of the amplifier ,Any help would be amazing.
Connect the R preamp output to the RCA level input on the R Velodyne.

Connect the L preamp output to the RCA level input on the L Velodyne.

Then use the setup/balance procedures in the Velodynes to integrate them with the main speakers. What this constitutes depends on which version of the SPL subs you have.

Also, this will not roll off the bass in your main speakers. To do this, you might make use of the Tape Monitor loop and the RCA outputs of the Velodynes.

for 2 channel, i recommend speaker level connections; ime, it integrates w/ main speakers better than with line level. just set the crossover on the sub at or below where your mains drop off. i use line level only for lfe w/ 5.1 surround. ymmv
If you have an extra $450 available, I'd grab a Velodyne SMS-1 and run pre
out R and L into the SMS line in R and L with RCAs and then the same scheme
from the SMS line outs into the subs. This will roll off your mains and your
subs. If you have 2 sets of RCA out from your pre, you may wish to run one
set per Kal's set-up and one per mine. This will run your mains full-range.

Either way, IME, you'll be happier.


PS search "SMS" in these forums and you'll see my (never ending -
sorry!) commentary on this excellent product.
Another excellent option is the nht x2 crossover which is much more flexible than the SMS, although it lacks the EQ.

So, which SPL sub do you have? With or without the auto EQ?


yes it has auto EQ, i have 2 SPL 800 R
Re: Kal's comment on NHT X-2

I use an X-2 for high pass and an SMS for low pass and EQ

IMHO, this is a "best of all worlds" solution, but I thought maybe more complicated than the OP wanted to hear about.


PS the auto EQ on the SPLR subs leaves something to be desired. The SMS satisfies those desires.
Use the speaker level inputs, it lets the flavor of your main amp come through the subs amps and blend better with your main speakers.
Use the speaker level inputs, it lets the flavor of your main amp come through the subs amps and blend better with your main speakers.

speaker level input has lelf and right so which one should i connect, because im using two subs , do i need to use biwire or just single wire
Which connection you choose should depend on your main speakers. If they are capable of producing clean bass, then either connection method will work equally well. If they are stand mount or small floorstanding speakers, then you should consider Kal's and Marty's suggestion of the NHT X2 filter and high-pass your main speakers. The X2 supports two subs. Taking the bass load off your main speakers can be an ear-opening experience.
A few quick further notes:

I used a pair of SPLR 8 subs (recently replaced) in my 14'x23'x17'high room. IME, if you want flat, extended bass response, the internal EQ in the SPLRs won't get you there. I had 3 significant suckouts below 100hz which couldn't be addressed as well as audibly diminished SPLs below 40 or 45 hz.

Replacing the 8" Velodynes with 12" subs reduced the need for EQ dramatically. However, the SMS was still tremendously valuable in determining the best location for the new subs.

Kal has much more experience with these devices than I do, so I'd believe him when he says that you can do better than the SMS-1. However, since my experience in 2 channel room analysis + bass EQ is limited to this device, I can offer no comparative assessment - other than to no room analysis + bass EQ at all. I can tell you - pretty much unequivocally - that the SMS is MUCH BETTER than no room analysis + bass EQ at all.

The SMS allowed essentially ruler flat response to 25hz with the SPLR 8s.


PS Replacing the subs didn't substantially change the on-axis, in-room response, but it did significantly change the sound of the system. I mention this because I don't want to overstate the impact of room analysis + bass EQ. Clearly, there's more to it than merely flat response. However, flat response (from either set of subs) was - IMHO - vastly superior to the alternative.
i have readed the SMS1 manual last night and i thoght it is hard to use but i try to read more and more , im using bookshelf apair Jm lab micro be , im happy with the sound but after i have readed the REL manual , they say it is better to use with SPEAKER INPUT , but mine are VOLODYNE , so any different between VOLODYNE sub and REL sub? the VOLODYNE manual does not recommend which input is better , so please advise which way the best without affecting the performance of the amplifier

The SMS is tricky to use - no doubt about that. Once you figure it out, it's great.

REL uses a very different approach than Velodyne. The whole "speaker level input" idea is closely associated with REL. I don't like this approach, but many others prefer it. I can give you many reasons why my preferred approach is "better", but in the end everyone must choose the approach that produces sound they like.

Chocolate ice cream or vanilla?

Any idea anyone ?
Neither approach necessarily affects the performance of the amplifier. If you use a bass management controller like the NHT X2, you could remove the bass load from your amp, but that shouldn't be an issue with your amp. The main concern is the impact on your main speakers. Since you haven't said anything about your main speakers, I can't say which approach I would choose.

Though since you have two subs, an NHT X2 makes a lot of sense and, as Kal said, gives you a lot of flexibility You don't need an SMS-1 since that functionality is built into your subs.
can you tell me what exactly SMS1 do ? i try to read SMS1 manual over and over again, does it really improve the sound quality?

The SMS-1 does 3 or 4 critical things:

1) A very flexible low pass crossover - frequency, slope, phase, & polarity all have very fine dgree of control. Some subs have this type of functinality built-in. Very few have this HIGH DEGREE of functionality. Critically important IMHO.

2) Parametric EQ. When added to the above, you can match the level of the subs to the main w/great precision. You can also choose a crossover frequency where response isn't too "lumpy" & use EQ to smooth whatever humps & dips ther are. This is IMHO critical to seamless x-over.

NOTE: You need a video monitor to take advantage of this. When the readout looks "flat" from the x-over frequency on down, you're pretty much golden. You also use the monitor to help place your subs for smoothest response before applying any EQ - again, very important IMHO.

3) EQ allows you to "fix" major humps and dips in the subwoofers output, without impacting the signal to the mains (if you run those full range or use a different high pass unit).

4) Depending on the sub, the EQ will allow you to boost the lowest frequencies to extend the botom end. I used to own 2 Velodyne 8" SPLRs and this was very important. I now own 2 12" Rythmik subs and this isn't really important at all.

Hope this helps.

I have another question on wiring the SMS. I'm using both the RCA and XLR on the SMS. One is for my two channel and one is for HT. Because I'm suing both does this fix the either xover @ 80hz or can I go into the setup and change the xover and slope?

The high pass filter (AKA - the low cut filter) for the main speakers is fixed @ 80hz, with (IIRC) a 6db/octave slope. This will affect only the low frequency roll off of your main speakers.

The low pass filter is variable for both frequency and slope. In the set-up menu, you can set preset #1 for your 2 channel and preset #2 for HT use. This will only affect the subwoofer's high frequency roll-off. When using the system, you can simply press either preset selector button #1 or button #2 on the remote to select the appropriate subwoofer roll-off.


Thanks Marty
thanks for everyone feedback