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Author Topic: Ideal subwoofer  (Read 2434 times)

Nige Eastick

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Ideal subwoofer
« on: March 18, 2018, 04:06:09 am »

Hi everyone a newbie here.
If this is the wrong section then i apologise.
Ive got a basic understanding of bridged and stereo on pa amp. Ive got a wharedale mp 1800 amp.
Specs below
Key Features

8 Ohms x 2: 330W RMS
4 Ohms x 2: 600W RMS
2 Ohms x 2: 1900W RMS
8 Ohms Bridged: 1200W RMS
4 Ohms Bridged: 1800W RMS
Class AB Technology
Suitable for touring, rental and installation
3 x Speakon and bare wire outputs
Peak and protect LEDs
Rear panel ground lift switch
All steel construction
Continuously variable speed fan
Stereo and Bridge modes
2 x XLR, 2 x 6.3mm jack inputs.
What it is im a drummer, and at larger venues to have my own 18" subwoofer for the kick/ bass drum sound reinforcement,  just the one sub at front in the  middle, when i do decide to get a sub, would i better off at 8ohms or 4 ohms?
I understand when you bridge a amp it cuts the impedance by half, ie 8ohms =4 ohms and 4ohms =2 ohms.
So my understanding would be if i do have to bridge my amp a 8ohm 18" would be better? As its running in 4ohms. And if later on get another 8ohm speaker daisy chain the two so its still going into 4ohm bridged in the amp.
I do understand though, if my amp is powerful enough to drive a speaker in stereo mode then will do that.
Much appreciated for any replies.
Nige.
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Keith Broughton

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Re: Ideal subwoofer
« Reply #1 on: March 18, 2018, 07:46:01 am »

You will get some answers once you post with your real name as per forum rules.
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Nige Eastick

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Re: Ideal subwoofer
« Reply #2 on: March 18, 2018, 08:59:56 am »

You will get some answers once you post with your real name as per forum rules.
Blimey there is some real sticklers on here, with the rules!!! 😀.
I've put my name down now, or is it a alias? 😀
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Ivan Beaver

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Re: Ideal subwoofer
« Reply #3 on: March 18, 2018, 09:28:11 am »

Blimey there is some real sticklers on here, with the rules!!! 😀.
I've put my name down now, or is it a alias? 😀
In a professional environment, everybody plays by the rules.

It also keeps the discussion real.

If you want to hide behind an alias, then that only shows how little you care about yourself, your questions and your opinions.



But to answer your question, there is no simple answer.

Why do you have an amp and no speaker?  Why did you choose that amp?

First of all, the idea of a drummer bringing his own sub is a BAD idea, for many reasons.  The biggest of which is all the sound it puts on the stage that gets into all the other mics, and the sound guy not having any control over it.

A single 18" driver is probably going to sound very unsatisfactory for a kick drum, since it is limited in freq response.  A lot of the kick "sound" comes from the higher freq.

What is your speaker?  Matching an amp to a unknown speaker is kinda hard.

Bridging will reduce the damping factor in half, so the "tightness" will be less.

A higher impedance speaker will have a higher damping factor.

Some people get hung up on damping factor, i am just providing the information.

Running a higher impedance speaker will reduce the loss of signal over the cable, but so will running a large gauge cable or making it shorter.

It is all a matter of tradeoffs.  There is no perfect solution.

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Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Nige Eastick

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Re: Ideal subwoofer
« Reply #4 on: March 18, 2018, 09:50:41 am »

Hi Ivan.
Thanks for your reply,.
 I'll answer your questions i play in a rock band, and to be fair most of the time we play in small pubs/clubs. Sometimes we also play outside events which then my bass drum can get lost, there is two guitars, bass and keyboards and vocals. 
The singer has is own PA 12" tops no subs, so my idea of getting my own sub or even subs, will go into the mix, via a active crossover, im looking at speakers at mo on e-bay at mo, and since come into pairs, I'll probably get a pair to balance things up.

As for the amp, i got the amp cheap £60 been serviced and works well, mind you it weighs a ton!!.
As for speakers I'll go 2nd hand at the moment im looking at some Behringer P1800S  euro live, 4ohms 425 rms and with my amp at 600 @4ohms per channel, ive still have some headroom. If not and i can find a single better speaker then I'll go with that.
As i have a large van, and still feeling strong humping gear a 7piece drum kit, rack hardware  and a 15" active speaker monitor!!.

Regards Nige
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Nige Eastick

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Re: Ideal subwoofer
« Reply #5 on: March 18, 2018, 09:56:16 am »

Also i forgot to add, i also have a channel  powered mixer amp, so can do my EQ on there. And go from the outputs L-R from mixer to input on amp, and use the channel knobs per mic input.

Nige
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Keith Broughton

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Re: Ideal subwoofer
« Reply #6 on: March 18, 2018, 01:17:05 pm »

Behringer P1800S  euro live, 4ohms 425 rms and with my amp at 600 @4ohms per channel
Considering you have no subs, this would be a place to start.
Make sure the speaker cones are in good shape and have no tears or are damaged in any way.
If possible, run a tone gen through your amp at a very low freq to make sure the cones are not rubbing or "scratchy"
Don't forget to high pass the subs on the crossover
Then, have fun :D
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Rob Spence

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Re: Ideal subwoofer
« Reply #7 on: March 18, 2018, 02:34:16 pm »

What speakers are the 12Ē ones in the PA? What crossover are you considering?
What mixer (specifically) do you and the singer have. The more specific details you give us, the better advice we can offer.

Watts are not a measure of sound loudness. When choosing pa gear you need to start at the required performance (loudness, frequency response, money available, weight, size and likely more) and then find the parts that satisfy those needs. Usually, first up is speakers followed by amplifiers that will make the speakers perform as required. Sometimes, you canít do what you need to due to other factors like cost, size or weight.
Usually, you go around the selection process a few times to choose the best compromise.


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Nige Eastick

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Re: Ideal subwoofer
« Reply #8 on: March 18, 2018, 02:42:15 pm »

Hi Keith.
Yeah i will make sure they will work, or demonstrate hence why ive put in a reasonable distance, my budget for subs is around the £250 mark, either a single or pair, 2nd hand doesn't bother me, if they have been looked after, not overloaded or trashed!!.

Is there any thoughts on the Wharfedale pro lx18mb 4ohm 18" subs?.
I fully appreciate that the more you spend the better you get, and with a gigging band things do get knocked around, and it's not every gig i will use.
Just the reinforce bass drum at larger or outside gigs.

Regard Nige
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Ivan Beaver

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Re: Ideal subwoofer
« Reply #9 on: March 18, 2018, 02:49:19 pm »

and it's not every gig i will use.
Just the reinforce bass drum at larger or outside gigs.

Regard Nige
So will your singer be using his same PA at these larger gigs?

Is his PA large enough for those shows?
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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