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View Full Version : questions concerning intergrated amp and sub. please help!



vokuro
06-07-2005, 02:58 PM
afternoon everyone, ive had my cbm-170's and a rotel RA-02 http://www.rotel.com/products/specs/ra02.htm for almost a year now. while i love these little speakers ive been yearning for a bit more bass extension lately. ive settled on the MRS-10 http://www.acoustic-visions.com/~acoustic/products/subwoofers/pre_finished/mrs10.shtml as ive heard great things about the musicality of this sub. my questions lies in the actual coming together of the two. the rotel has a pair of preamp-out jacks, but im not entirely sure how to continue from there. any help with this matter would be greatly apperciated!

BradJudy
06-07-2005, 03:35 PM
There are two primary options: Use the pre-outs on the Rotel to the line-level inputs of the sub amp or run the Rotel speaker level outputs to the speaker level in on the sub amp and the sub amp speaker level outputs to the CBM-170s. Either way, then play with the crossover point (try around 60-80Hz) and the sub amp level to get a blending that sounds best to you. Personally, I would start by using the pre-outs from the Rotal into the sub because it's simple and you likely have the required cables sitting around (maybe you also have a spare set of speaker cables). You could use a set of test tones and an SPL meter to help set the sub volume level or do it by ear. If you really want to get into it, you could map the frequency response with different crossover points to find a good setting, or also do that by ear.

vokuro
06-07-2005, 07:30 PM
thank you bradjudy your reply really helped me out. as far as SPL meters go can you recommend a cheap effective meter? also, correct me if im wrong but isnt subwoofer cable just a cable thats terminated on both sides by RCA plugs? and because its mono i only need one? also people have been mentioning this product: Behringer DSP1124P Feedback Destroyer. do you feel its something necessary to smooth the frequency response? thanks again

BradJudy
06-07-2005, 08:17 PM
The RadioShack SPL meter is a decent, inexpensive one that is widely used. It does have either A or C weighting and you'll find compensation factors for C weighting on the internet listed as RadioShack SPL meter correction factors.

Yes, a sub cable is an RCA terminated cable, but you want a stereo one, not a mono one. Although there is only one speaker in a sub, you want it to be playing the combined left and right low frequencies. A typical stereo RCA cable will work fine. If you are doing a longer length, you might want to make sure you have a shielded one.

The usefulness of a BFD (or any other EQ equipment) depends on the response in your room and your ability to change the location of the sub for the best response. It also depends on your willingness to spend time measuring the response and tweaking the EQ to compensate (this typically takes several iterations). Is it required? No. Would it make your sub sound better? Very possible. Is it worth the cost, time and effort? Depends on your priorities.

vokuro
06-08-2005, 12:22 PM
brad your patience is virtuous as i know these are rudimentary questions you are fielding. however perhaps you could endure a few more?

im deciding between the MRS10 and the svs PB10 however the latter doesnt come with a crossover feature. what options do i have? external crossover? can i defeat frequencies over 80hz with the DFB? another question, a lot of talk is centered around flattening the response of subs, but what about mains? can i use the DFB to flatten the in room response of my CBM 170's? also, maybe you can offer a bit of subjectivity on the issue. i listen to an assortment of musical genres, usually focused around dance/synth pop and rock. care to make a sub recommendation? room dimensions are 10x20x8. thanks again for all your help!

BradJudy
06-08-2005, 01:42 PM
Your questions are good ones and this discussion should be helpful for others with similar questions.

The PB-10ISD isn't a good option for your situation because of the lack of crossover and the single input. It's designed specifically for use in home theater where the receiver is handling crossover and signal summing. There are simple, in-line filters that you could use in place of a crossover (http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-252). Even with this, you need a way to combine the left and right signals into one which would mean a basic mixer ($30-50).

I would recommend the Hsu Research STF-2 as an alternative (http://www.hsustore.com/stf2.html). It's a very good sub and one of the best sub values at $400. It has speaker level inputs, but only a single line-level input, so it could only be used with the speaker level inputs in your situation. Their VTF-2 Mk2 has stereo line-level inputs, more power and is tunable, but runs $500. I own a VTF-2 Mk1.

The AV123 ELT SW-10 is another <$400 option with both stereo line-level and speaker level inputs. http://www.av123.com/products_product.php?section=subwoofers&product=5.1

I wouldn't worry about using an EQ on your mains unless you have a known problem that can't be fixed otherwise (i.e. room treatment/position). The response of my CBM-170s in room is very flat with the exception of a reflection point (the floor).

vokuro
06-08-2005, 02:50 PM
brad quick question before i head off to work. where can i get a program that will measure the frequency range of a given sound file (.wav, .mp3, whatever) therefore allowing me to see how low i need the sub to go with my style of music?

BradJudy
06-10-2005, 06:13 AM
Hmmm...I haven't played with that at all, so I don't know a good application off of the top of my head. I know some audio applications will show things like waterfall plots of audio, so they are available.