RM30 has very little bass

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mjmessina

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RM30 has very little bass
« on: 30 Nov 2014, 02:32 pm »
Have a set of RM30's that seem to start kicking in around 100hz and get to a good level around 150+.
I had them for awhile. It never was an issue because I was using my Super towers as subs.

Now that I am looking at new subs, having a crossover at 150-200hz seems kind of high.

Do I have a defective set? or is this typical of these speakers?

John Casler

Re: RM30 has very little bass
« Reply #1 on: 30 Nov 2014, 05:49 pm »
Have a set of RM30's that seem to start kicking in around 100hz and get to a good level around 150+.
I had them for awhile. It never was an issue because I was using my Super towers as subs.

Now that I am looking at new subs, having a crossover at 150-200hz seems kind of high.

Do I have a defective set? or is this typical of these speakers?

The RM30C (no side firing woofer) should go easily into the 50's
The RM30M (side firing active 10") should go into the 40's
The RM30 Series II (side firing 10" PR) should also go into the 40's

Your problem could be:

1) Room related
2) Some kind of  woofer problem

or both.

Try turning the L-Pads as far counter clockwise as possible and listen.

This will reduce the total Mid and HF output relative to the woofers.

Also check the woofers and PRs (by touching them) to see if they are active during bass passages.

mjmessina

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Re: RM30 has very little bass
« Reply #2 on: 30 Nov 2014, 07:06 pm »
Thanks for the reply John.

They are RM30 series II.  They are in my basement and the room size is about 900sq ft.
So maybe they are just getting lost and need some good subs.

I took the jumpers off the top post and only drove the woofers, plus did what you suggested (turned both pots down).

The woofers do move just a little at 40hz, very low sound.
as the frequency increases, so does the sound level.  I would say around 100 to 120hz is where the level is consistent.

Not sure if this is typical of these speakers.

I am going to go with two Dayton UM15-22's  http://www.parts-express.com/dayton-audio-um15-22-15-ultimax-dvc-subwoofer-2-ohms-per-coil--295-514
I looks like these will easily cross over at 150 to 200hz.

DFaulds

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Re: RM30 has very little bass
« Reply #3 on: 1 Dec 2014, 11:47 am »
To me that sure sounds like the woofers are connected out of phase in one channel.  This would cause cancelation in the lower frequencies, and your observations of 100-150 HZ certainly seem to fit the bill for this type of a problem.

HAL

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Re: RM30 has very little bass
« Reply #4 on: 1 Dec 2014, 12:35 pm »
What are you driving the RM30's with? 

mjmessina

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Re: RM30 has very little bass
« Reply #5 on: 1 Dec 2014, 01:34 pm »
I am driving them with an ADCOM 5503 (it puts out 350watts @ 4ohms), should be plenty of power.

DFaulds stated it may be a cancellation issue.  Which I now think it is, the sound level in general is very low on the RM30s.
I thought the RM30s were just power hungry.  My super tower IIs play a lot louder than these do. I had to set my subs and rears  at 4dbs lower.

HAL

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Re: RM30 has very little bass
« Reply #6 on: 1 Dec 2014, 01:41 pm »
Is the Adcom 5503 being driven full range by a preamp? 

Are there any HP filters due to an AV preamp?


mjmessina

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Re: RM30 has very little bass
« Reply #7 on: 1 Dec 2014, 01:52 pm »
When I run the test, no.
I have my pre amp set to pure direct, and to be sure, I set my speakers to large (which runs at full frequency).  I also use my super tower IIs as a bass reference, which produce plenty of bass.
I don't expect my RM30s to come close, but the bass is pathetic on the RM30s right now.  My computer speakers out perform them.

HAL

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Re: RM30 has very little bass
« Reply #8 on: 1 Dec 2014, 01:57 pm »
As stated above, check the woofer phasing.

You can use a 1.5VDC D cell and check to see if they both move in the same direction when connected the same on both woofers. 

mjmessina

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Re: RM30 has very little bass
« Reply #9 on: 1 Dec 2014, 02:08 pm »
Great advise! can't wait to get home tonight and try it.

Carl V

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Re: RM30 has very little bass
« Reply #10 on: 1 Dec 2014, 03:15 pm »
Great advise! can't wait to get home tonight and try it.

How long have you owned these speakers?
In other words what would cause them to be wired
out of phase now?  I understand that  you may have
masked this problem all along with your super towers.

Nice speakers....years ago an acquaintance had three with
mega (?) sub...he used a triaurnal (sp?) processor. Spooky
good Soundstage with the right source material.

John Casler

Re: RM30 has very little bass
« Reply #11 on: 1 Dec 2014, 03:31 pm »
The possibility of the woofs being out of phase is a good call.

There are a couple of ways that you should check:

1) check each speaker to see if BOTH woofers move in and out at the same time
2) check that the pairs also move in and out at the same time

That is, it could be that the top and bottom woofers are out of phase, or that the left and right woofers are out of phase with each other.

mjmessina

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Re: RM30 has very little bass
« Reply #12 on: 1 Dec 2014, 03:32 pm »
I have owned them for 2yrs now.  I was disappointed with the bass since day one.
They are probably the last RM30s ever made. Brian died soon after I received them.
So I never pushed the issue. I gave up, and just set my cross over freq to 150hz and let the super towers take over.

Now that I want to sell them, I am being more critical of what the RM30s are producing.
Recently, my suspicion have been confirmed that there is a whole spectrum of frequencies not being heard.  I hope it is the woofers being out of phase.

John Casler

Re: RM30 has very little bass
« Reply #13 on: 1 Dec 2014, 03:54 pm »
They should NOT be HUGE on bass, but your description shows something is certainly amiss.

I remember one year in Vegas we had the RM-30s with a pair of subs.

One morning the sub amps didn't get turned on (we normally left everything on, but someone turned them off) and we didn't even miss them, because the bass seemed totally adequate.  The only way we discovered it, is someone noticed the LED wasn't lit.

So while not particularly a bassy speaker, the RM30 certainly has reasonable bass.
« Last Edit: 1 Dec 2014, 06:59 pm by John Casler »

*Scotty*

Re: RM30 has very little bass
« Reply #14 on: 1 Dec 2014, 03:59 pm »
Assuming your basement has a 7 ft. ceiling, your basement would have a volume of ~ 6700 cu.ft..You are asking the equivalent in cone area of an 8 inch driver in each loudspeaker to deliver enough bass to balance out the mid-range and tweeter output which will be almost impossible for them to do in this situation. You might try putting the speakers directly against the front wall to get some more room boundary reinforcement in the bass frequencies and see if this helps any.
 You would encounter a similar lack of bass if you listened to the speakers outdoors. In this case there would be no boundary reinforcement except that which comes from the surface the speakers are resting on.
 The bigger the space you are trying to fill with bass energy the more cone area you need devoted to this frequency range.
Assuming that there are no phasing or mechanical problems, the speakers may produce an adequate amount of bass in an average sized living room which typically will be as much as 4 times smaller in volume than your basement.
Scotty

mjmessina

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Re: RM30 has very little bass
« Reply #15 on: 2 Dec 2014, 02:32 am »
I just checked my RM30s, the speaker phasing is correct.
All the woofers on both speakers extend in the same direction when applying a DC battery.  Rechecked all the wiring too and did a speaker-by-speaker test.

I have an old set of 626s (the original ones with the two 6 1/2 woofers).
They seem on par (as far as bass) with my RM30s.  I would even say they go a tad bit deeper.

I did an A-B test of my pure direct & direct settings.
Where pure direct does not perform a HP 150hz cut off.
The direct setting does perform a HP filter at 150hz..
There was just a little improvement in the bass produced with pure direct.

I am going to write this off to my room size (as Scotty pointed out), and set my crossover to 150hz.

The good news is the RM30s have incredible imaging and detail at the mid and high-end. When I pair them with my Tower IIs (as subs), I get jaw dropping expressions from friends and family on the sound. Can't beat a 5.1 VMPs setup!.


John Casler

Re: RM30 has very little bass
« Reply #16 on: 2 Dec 2014, 04:54 am »
The 626R has an amazingly deep and quality bass response for its size.  I am not sure how that equates to the regular 626 (no-R).

Depending on placement, it easily might sound deeper than the RM30 (again depending on placement)

Try playing the RM30s with some good bass and stand in the corner of the room.  If you hear deep bass, then IT IS being produced, but the room is not allowing you to hear it at the listening area.

As well if your subs (for the HT) are not playing from the same position as the RM-30s but from another room position, that might be what is needed in that room.

Doug Ravizza

Re: RM30 has very little bass
« Reply #17 on: 3 Dec 2014, 03:33 pm »
As a point of reference, I've been very pleased with the bass response of my RM30 Series IIs (w/ OXO and TRT options) having downsized from a pair of RM40s. FWIW, here are some response curves as measured by a Velodyne SMS-1 (20-200Hz sweeps). Room size is 13' X 19-1/2' with 10' ceilings. The PR putty was last touched by Brian when he came to my house to replace a failed Neo-panel.



DFaulds

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Re: RM30 has very little bass
« Reply #18 on: 4 Dec 2014, 12:30 pm »
I would expect that a relatively large cabinet like the 30’s with two decent 6.5” woofers should get response down to at least the mid 30’s, especially considering the fact that Brian designed them.  My Direct Acoustics are very small floor standers with a single 6.5” and they easily go to the low 30’s.  Of course, Win Burhoe knows a thing about bass alignments as well.

If it’s not out of phase drivers I would suspect room placement issues.

Hipper

Re: RM30 has very little bass
« Reply #19 on: 7 Dec 2014, 11:19 pm »
My RM30Ms (first edition from 2006) easily go down to 30Hz and according to the website should go down to mid 20s:

http://pointillistic.com/vmps-audio/RM30.htm

The low crossover is at 280Hz but I understand the neo panels also produce below this frequency.

I'm not clear if you have the 'M's or 'C's but if 'M's with the side firing woofer, the suggestion for larger rooms is to have them firing outward. In my room (14' x 13' x 8', or 1,456 cu ft) I have them firing inwards.

Surely if you go close to the woofers you should hear the low bass. If you can't then there must be something wrong. I have plenty of bass traps in my room which mean I mostly hear just the speakers. Even though your room is four times the volume of mine you should get something. Surely the sort of room size you have is similar to the show rooms at CES where these speakers were exhibited.