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Portable Battery 2 way speaker

Printed From: Speakerplans.com
Category: Plans
Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
URL: https://forum.speakerplans.com/forum_posts.asp?TID=106952
Printed Date: 01 October 2022 at 6:34am
Software Version: Web Wiz Forums 12.05 - http://www.webwizforums.com


Topic: Portable Battery 2 way speaker
Posted By: Jack1991
Subject: Portable Battery 2 way speaker
Date Posted: 16 March 2022 at 8:42pm
Planning on making a portable speaker. Bought a few bits for it already but thought id make a build thread and hopefully get opinions on it to make sure im going the right way about it. Doing it as a bit of a experiment and a learning curve and just a bit of fun really. Hoping it to weigh under 15kg in total.

What im using:
P-Audio 410 Tweeter, spl 105db
8" Fane Sovereign 8-225, spl 97db
2.5k convair crossover (making use of one i already have)
NE5532 Preamp
TPA3255 amplifier board (using just 1 channel to get around 80w at 35v 8Ω)
18v Makita Battery
Dc step up converter (to step up the 18v to around 35v)
12mm Baltic Birch Plywood

As im only using 1 channel on the amplifier circuit board i will have to make the input mono. I will only ever use my phone with it so ill just set my phone setting to combine channels to mono.

Been on winisd for ages trying different drivers to try and find the 'best' for what i am after. Im still a n00b on here so a bit of assuming took place. So be good to get confirmation that im right according to the graphs. I tried a few drivers to get it as low as possible and the fane turnt up best. Also at 97db spl it seemed the best bang for buck especially as its on a 12v system.

Box exterior size at the moment is roughly 45cm high X 27cm wide X 37cm deep. The woofer chamber is 23378cm³. And then after speaker/port displacement it works out to 21 litres tuned to 57hz. I had to go slot port to keep air velocity to a minimum. From what i have read under 20m/s is best to avoid chuffing?  I planned on using a 2" round port at first but then after checking cone excurision it was sky high! Up in the 60/70 m/s. And using a bigger round port it had to be far too long. So slot port works out perfectly... I hope anyway.

I am kind of plucking the box tuning hz out of thin air to be honest. I cant imagine what different hz would sound like as i dont play any instruments or anything. So i have just aimed to get it as low as possible. I know the lower it plays the bigger the box so its a bit of a trade off. And this seemed like the biggest i would like the box to be. But will it be low enough? I play reggae/dub/dnb/jungle and just general dance electronic tunes.













Replies:
Posted By: Jack1991
Date Posted: 20 March 2022 at 7:30pm
Made it today. Heres a couple pics during glueing & screwing





The empty compartment behind where the tweeter will be is to house the battery, crossover, amplifier and the dc step up. Needed it big enough to get my hands in to screw the parts in place, seems just about right. Will find out soon if it is or not. Also it will have a little door on it which will be fitted later.


Posted By: Jack1991
Date Posted: 26 March 2022 at 3:44pm
All built and tested, not fully finished, just a test with external amplifier but it sounds good! One thing i wish i done was put the port on the front. As from behind the bass sounds pretty pumping for the size of it, i was impressed. But the front not so much, until i turn it right up then can hear it more.





Would it work the same on the front as i have the 15mm overhang lip on the front. I was thinking if i had the port at the bottom under the 8".  But because it has the 15mm extra length at the bottom of the port, would that affect it? The top of the port would finish in line with the face. Hope that makes sense to you?



If it will work i will remake it all with a front port. I enjoyed making it and the wood is free off a mate anyway so its all good.


Posted By: Jack1991
Date Posted: 09 April 2022 at 11:57am
*V2 ready for testing*

Hopefully having the port on the front makes it sound better. Definitely looks better i think! (obviously the cable wont be like that when its finished proper)




Posted By: Lucasdude
Date Posted: 09 April 2022 at 12:58pm
Nice work! I'm interested to hear your opinion on the port location difference in free space. Imho, a box folded grille would look nicer than the round one. Maybe just leaving the port open.  What are you considering as a finish?


Posted By: Jack1991
Date Posted: 09 April 2022 at 2:21pm
Originally posted by Lucasdude Lucasdude wrote:

Nice work! I'm interested to hear your opinion on the port location difference in free space. Imho, a box folded grille would look nicer than the round one. Maybe just leaving the port open.  What are you considering as a finish?

Cheers man!
 

Ah yeh a box folded grille would look quite cool actually.

Its more of just a fun little experiment at the moment though. But i might consider changing it in future. Im not sure the lip would be thick enough to cater for a box grille, its a 15mm lip. How do they fix them in too?

Yeh i cant wait to hear it too. I will test it out tommorow or monday as im out for the day now. It 




Posted By: Lucasdude
Date Posted: 09 April 2022 at 2:39pm
For that baffle size, I would just look for 4x15mm rubber spacers and use wood screws with small washers, but check the woofer excusion clearance first! The guy at speakergrilles can box fold grilles to your custom size.


Posted By: Jack1991
Date Posted: 10 April 2022 at 6:54pm
Cool cheers. Been thinking about it today and going to stick with what i got now. But good to know for future projects.

Also tested it in the garden earlier today and it sounds loads better with the port on the front! Need to take it out somewhere though to proper test it turning up the volume. Didnt want to play it loud in the garden.

Another thing ive changed from the start is im going to run it off of a 18v Makita Battery. And also i am going to probably need to use a preamp too.



Posted By: Lucasdude
Date Posted: 10 April 2022 at 8:55pm
If you're using a phone or similar as a music source, try the "Poweramp" app. The SQ and file support is great, it's an easy way to sum to mono, and you can also use the EQ as a high pass filter so you're not robbing the battery power with inaudible frequencies. When I'm using a battery system, I also have a little Sony laser projector than can display the visualization from the app, if you're ever in that sort of mood...


Posted By: Jack1991
Date Posted: 10 April 2022 at 9:31pm
Cool cheers just downloaded it now its really good! Thats a good idea too with to use it as a filter to save wasting battery.

I cant find how to sum to mono on there though?

Also sorry only just realised i didnt answer your question about what im using for finish. Osmo Oil, ts my favourite wood finish really brings out the grain, with barely no shine, nice natural look.


Posted By: Lucasdude
Date Posted: 10 April 2022 at 10:26pm
In Poweramp, under EQ click the middle knob looking icon at the top middle. You'll find mono setting there. You can also boost the output with "Preamp" in the EQ.
   I like the sound of just oiling a well sanded finish. Maybe 4 stout rubber feet will protect the bottom from grass damp.
  Looking at the specs for that power amp, the maximum input voltage is 40v, so you could also consider using 2x 18v batteries in series and lose the step up converter. I'm not sure which batteries you have, but I remember the red ni-cad ones being crap. Those slim black Li ones are half the weight and much better.


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:52am
Cool yeh the preamp bit looks good too.

Yeh ive been thinkiing maybe 4 black rubber feet might look good. Also nice to raise it off ground.

I was thinking that too but someone over on another 12v forum said not to push those amps too hard  and said around 30v would be max. As he blew a few at 36v.

I did try finding better amps but all i can really find is chinese ones like that TPA3255 etc.

Yeh i have the black 18v li-ion batteries 5AH so should be all good hopefully.


Posted By: infrasound
Date Posted: 11 April 2022 at 11:41am
Depends on your exact TPA3255, but I have run good quality ones above 50V into difficult 4R loads with active cooling.

If you're just using one channel at 8R, I really wouldn't worry too much about higher power. Bear in mind the max voltage per pack is probably 21V, therefore you could see 42V total.

However, battery life may suffer, and you could run into problems with excursion / port velocity.



Posted By: Jack1991
Date Posted: 11 April 2022 at 11:54am
Oh right cool thats good then, cheers man.

From looking online though i have only come across 1 type. Heres the one i have bought. Its not arrived yet though.




Heres the preamp & the dc step up converter i have bought too.

Preamp



DC Step Up Converter



Posted By: Lucasdude
Date Posted: 11 April 2022 at 12:45pm
I have no idea what those amps sound like. My solution for a good portable amp used to be a small Caliber Competition  and a motorbike battery! How things have moved on.


Posted By: Jack1991
Date Posted: 11 April 2022 at 1:00pm
Originally posted by Lucasdude Lucasdude wrote:

I have no idea what those amps sound like. My solution for a good portable amp used to be a small Caliber Competition  and a motorbike battery! How things have moved on.

I have no idea either to be honest. Im part of a 12v Sound System forum on Facebook and i regularly see people using cheap chinese amps like this and they seem to rate them. So im hoping it will sound good enough.

I need small parts as its going to be portable so all needs to fit in neatly into the top compartment. This seemed like my only option really


Posted By: Lucasdude
Date Posted: 11 April 2022 at 1:28pm
Is that amp bridgeable? If not, does the cross over you're using allow for blamping?


Posted By: Jack1991
Date Posted: 11 April 2022 at 3:41pm
The amp is not bridgable unfortunately no. Also i have no idea what blamping is?

It was quite hard to find a amplifier that would give enough power into 8Ω
And i couldnt find any speakers 4Ω that the box size was small enough and go low enough. Bit of a compromise.

Hopefully the amp is good enough. If not hopefully people give suggestions on here.


Posted By: Lucasdude
Date Posted: 11 April 2022 at 4:30pm
Biamping would allow you to drive the woofer and tweeter separately with a channel each of a stereo amp, albeit still using the passive crossover you have. It's not as good as active driving, where the frequency dividing happens before the amps, but it would be a better use of what you have. Which Convair crossover is it?


Posted By: Jack1991
Date Posted: 11 April 2022 at 4:48pm
Ah right cool i see. It is this one 2.5k convair crossover.


Also yeh if there is better things i can buy e.g amplifier or preamp or better ways to do what im doing i am more than happy to do that. Obviously price wise within reason. Im just going off what i have read online, dont have much expierience with it all.




Posted By: Lucasdude
Date Posted: 11 April 2022 at 6:33pm
It's not difficult to work out watts watt on that board. It won't gain you much, but driving the 2 halves of the network with a channel each might mean less chance of HF driver damage due to clipping, and might sound a bit better.


Posted By: Jack1991
Date Posted: 11 April 2022 at 6:48pm
Ah right ok cool how would i go about that i dont really understand?

I thought 1 channel of the amplifier goes to the 'IN' on the crossover and there wasnt any other way round i could do it?

Also there are no gain controls, would that not mean i would be getting too much power to the highs?


Posted By: Lucasdude
Date Posted: 11 April 2022 at 7:29pm
I won't try and explain how you might go about it as I don't want you to damage anything. If you are interested then you'll find some help online. If you do proceed and use Poweramp summed to mono, you will be able to control the level to each driver using the "balance" control in the app. This might also help if the drivers you are using aren't the spec that the crossover was designed for.
  incidentally, I did notice that one of those Convair 2.5k crossovers needs to have the HF polarity reversed, so that might be something to try at some point.


Posted By: Lucasdude
Date Posted: 11 April 2022 at 7:59pm
Just another thought on that. I assume you have another identical one of those crossovers? If so, you may aswell try the same thing but use a separate board for each driver.


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:08pm
Ok cool yeh i just googled and i partly understand now here is 1 photo which i assume is what you meant.

I would be wiring it like the first photo. But it sounds like your saying to wire it like the bottom photo? Amplifier 1 and Amplifier 2 being just each channel i assume too?




Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:12pm
In your case it would be passive biamping, so picture 2. The "X" at the input of each driver denotes "crossover". In picture 3, the X is before the amps so that is active biamping.
  Yes, on your mono system you can treat each amp channel as a separate amp.
  If you have 2 identical 2 way boards, just use one for each amp channel connected to the relevant driver.


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:16pm
Ah right ok cheers yeh i see what you mean now.

And yes i do have another exact crossover. I wasnt planning on using it but will consider it now. As long as there will be enough room inside to fit it ill do it.

My only concern is that passive crossovers eat battery power i have heard, so having 2 in there would make battery power worse wouldnt it?


Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:19pm
No, using one half of each board is effectively the same as using the whole board of one.
  In addition to splitting the frequency band, the crossover may also resist one part to balance the end frequency response of the drivers. The purest dividing network is probably just a single capacitor in series with the the HF to ensure it doesn't handle any low frequencies.
  Cheap components on a passive crossover sound poor, and using too much resistance to balance drivers will certainly rob available amp power.


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:20pm
Oh cool that makes sense then.

Just reading about biamping now and sounds like you get a nicer clearer sound and deeper bass.


Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:30pm
On one of my battery projects recently, I used a 4 channel high quality car amp to actively biamp a small pair of speakers. Because  car audio is used to such things, it was easy to put a low pass on 2 channels and a high pass on the other 2. The amp also had a variable subsonic high pass, so I can use that in the same way we discussed to stop the system robbing power due to inaudible frequencies.


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:31pm
Originally posted by Lucasdude Lucasdude wrote:

No, using one half of each board is effectively the same as using the whole board of one.
  In addition to splitting the frequency band, the crossover may also resist one part to balance the end frequency response of the drivers. The purest dividing network is probably just a single capacitor in series with the the HF to ensure it doesn't handle any low frequencies.
  Cheap components on a passive crossover sound poor, and using too much resistance to balance drivers will certainly rob available amp power.

Oh ok would it be better to just do away with the passive crossover and fit a capacitor in series?

If so happens to the woofer though to stop it playing too much highs?


Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:35pm
I didn't see any damping in the main chamber of your speaker. I would suggest you use something. On that design, maybe just 5 small bitumen panels would do it. The only downside is a bit more weight, but I think the result would justify it.


Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:40pm
Originally posted by Jack1991 Jack1991 wrote:

Originally posted by Lucasdude Lucasdude wrote:

No, using one half of each board is effectively the same as using the whole board of one.
  In addition to splitting the frequency band, the crossover may also resist one part to balance the end frequency response of the drivers. The purest dividing network is probably just a single capacitor in series with the the HF to ensure it doesn't handle any low frequencies.
  Cheap components on a passive crossover sound poor, and using too much resistance to balance drivers will certainly rob available amp power.

Oh ok would it be better to just do away with the passive crossover and fit a capacitor in series?

If so happens to the woofer though to stop it playing too much highs?

I don't know if that would work for you. If you go the biamp route, and are able to balance the channels as we discussed then it might, but to make that sound right you would have to take measurements of the bass driver response with a full range signal. Then note the roll off rate and work out the type of HPF the tweeter would need. A single series capacitor would only provide a 1st order slope, so that may or may not be ideal.
  Having said all that, it's all good fun!


Posted By: Jack1991
Date Posted: 11 April 2022 at 8:45pm
Originally posted by Lucasdude Lucasdude wrote:

I didn't see any damping in the main chamber of your speaker. I would suggest you use something. On that design, maybe just 5 small bitumen panels would do it. The only downside is a bit more weight, but I think the result would justify it.

I havent fitted anything yet but i have here some 'medium wadding' from blue aran, its what i bought to use in here. Would that be ok? If so what walls would be best to do?


Posted By: Lucasdude
Date Posted: 11 April 2022 at 8:58pm
In such a small enclosure it will make a big difference. Imho, the rear panel will be the first to treat. The "woodiness" of lower vocals is what needs to be addressed. The only problem is that bass response will suffer if you put too much in.
  Make sure you keep it away from the port entrance though. If it were me, I would still consider some bitumen panels. Wickes sells various sizes under "roof flashing". You can check the difference it makes just by feeling the panels at different frequencies. That's also a good way to check all the panels are sealed correctly. Did you use anything to seal the inside joints?


Posted By: Jack1991
Date Posted: 11 April 2022 at 9:03pm
Cool ok yeh ill try that then. This is the stuff i got, is this ok to use for it, or is bitumen better to use? I have never heard of bitumen being used before.

Also is it worth covering the whole panel or just sections? I know i need to not put any covering the port at all.



Yes i sealed all the joints with CT1


Posted By: Lucasdude
Date Posted: 11 April 2022 at 9:11pm
In an ideal world, the vibration of the cabinet panels wouldn't contribute to the sound of the speaker. Some may call this colouring effect "character", but I don't feel the same.
   I'm not one for just doing stuff for the hell of it, but if I can get a small gain for a small effort and a small expense then I'm all up for it.
  If you use bitumen panels on all 5 (excluding the baffle), I'm very confident it will result in a better sounding speaker.
  Do take into consideration that adding this to all the panels will reduce the effective internal volume and therefore raise the cabinet tuning frequency. You might want to calculate the differnece before committing!


Posted By: Jack1991
Date Posted: 11 April 2022 at 9:17pm
Ah ok i see so the bitumen isnt for standing waves in the cab, they are just to stop panel rattle?

So it might be worth adding bitumen and the wadding i showed too?

And yes understandable it will reduce the volume in box. 


Posted By: Lucasdude
Date Posted: 11 April 2022 at 9:25pm
Try using a tone generator app and feel each panel at various frequencies. There will be a couple of resonant peaks which, although can't really be eliminated, may be mitigated. I've found that these frequencies affect different styles of music to a greater or lesser extent.
 Using a tone generator can also be helpful when you apply pressure to opposing panels, as these are often the easiest to brace.


Posted By: Jack1991
Date Posted: 11 April 2022 at 9:37pm
Cool perfect cheers mate ill try these different tips this week and see how it goes.

I have been testing it using my pioneer car amplifier.

Also i just remembered i have some Dodo Deadn Hex Mat leftover from my camper build. Which is litterally used to dampen vibrations. So ill try that out. Unless bitumen has better certain properties?


Posted By: Lucasdude
Date Posted: 11 April 2022 at 9:40pm
If it's black, thin and tacky inside I'm sure it's similar stuff. What camper do you have?


Posted By: Jack1991
Date Posted: 11 April 2022 at 10:02pm
Cool its perfect stuff then.

Its only a VW Caddy Maxi. Litterally just finished it. Nothing too fancy inside just sound deadened, insulated and carpeted and altro flooring down. Keeping it basic and just using it for weekend aways and festivals.


Posted By: Lucasdude
Date Posted: 11 April 2022 at 10:07pm
Sweet. If you see or hear an army green VW T4 dropping some basslines then say hi!


Posted By: Jack1991
Date Posted: 11 April 2022 at 10:16pm
Haha cool will do man! And cheers for all your help so far!


Posted By: Jack1991
Date Posted: 13 April 2022 at 6:39pm
The amplifier finally arrived. Just looking at positioning now for the Amp, Preamp, Crossover, and the DC step up.

I want them fitted toward the front, on the side walls, nearest the tweeter as possible really. Just to keep it all away from peoples fingers, should someone else open it to change the battery or that. The battery holder will then be fitted in the middle nearest the door end.

Is there any downsides to that at all? With the tweeter having the big magnet on it. The tweeter will be the last thing fitted but here is a photo just to show you how it is, and so i can work out roughly how things will go.

There is about a 4cm gap between the tweeter magnet and the tallest part which is the amplifier.

Heres a photo just so you can see what i mean





Posted By: Lucasdude
Date Posted: 13 April 2022 at 8:07pm
From a practical point of view, I would pay some attention to weight distribution when it's being carried. You already have 2 heavy magnets at the front. It might be an idea to mock up all the components inside, then work out the centre of gravity before banging a couple of t-nuts in for a hand carry strap.


Posted By: Jack1991
Date Posted: 13 April 2022 at 8:13pm
Yeh i did think about the weight but not too sure i can do much about it, without it all being near the back towards the door. 

Also the door has 2 holes in which are for air flow and also for your fingers to get in to remove the door. I got no idea how hot the electronics will get but thought its best to have 2 holes for air flow? Another reason thought to keep away from the holes incase of rain or liquid getting in. Chances are low but even lower with things away from there.

But yeh completely agree with you about weight distribution.



The holes can easily be blocked off on the inside if they arent necessary.


Posted By: Jack1991
Date Posted: 28 April 2022 at 6:15pm
Just finished it today well happy with it. The preamp makes such a difference. Sounds clearer and cleaner, and also louder at lower volumes.

Needs a bit of eq'ing, that poweramp app is really good, but could also do with some pointers in what best to set for it on the parameteic eq.

No idea how long the battery will last yet only tested for 15mins in the garden at half volume was loud enough with neighbours and that 😆 will take it down the field soon to give it a good blast.














Posted By: Lucasdude
Date Posted: 29 April 2022 at 6:32pm
Looking good! Can you swap out the battery easily? Maybe you could rig up some sort of charger using one of those small camping solar panels? I've heard good things about Anker ones, but charging 18v will be a challenge!


Posted By: Jack1991
Date Posted: 29 April 2022 at 6:46pm
Cheers man! Yeh swaps the same as if it was on a tool, its attached to 1 of these in photo.



Haha that would be pretty cool solar charging it. Way beyond my knowledge at the moment though.

One thing someone said on another forum was i should fit a 'low voltage cut off relay' so the battery cuts out at 15v minimum or it can damage them permanently and wont recharge. Or to just keep an eye on the voltage. So bought a little voltmeter the one in the photo. Id rather that as im interested in seeing how long it lasts, with different styles of music, so be good to actually see the voltage itself. Waiting for it to arrive to fit it next week. Its only small around 3cm.



That poweramp app is really good too! I like the parametric eq bit. Although im not 100% sure on what to change so have just been having a play around with it and seeing what sounds good. I think if i had a measurement microhphone it might be better so i can actually see what frequencies need changing. Although i havent done that before so would be a bit of playing around with that. As im not actually sure what i am aiming for with EQ'ing, is it that the freqeuency line should be as flat as possible?


Posted By: Lucasdude
Date Posted: 29 April 2022 at 9:33pm
I've never found anywhere quiet enough to do any serious measurements outside. However, with 2 smart phones and a tone generator app on one, spl meter on t'other, I've managed to lose a few solitary hours!


Posted By: Jack1991
Date Posted: 29 April 2022 at 9:46pm
Thats not a bad idea. As im not super audiophile so im reluctant to fork out for a umik-1 mic to maybe not fully understand it to get the most out of it. But would like to be able to eq it nicely.

What spl meter app and tone generator app do you use please? Does it show a frequency response line too?


Posted By: Lucasdude
Date Posted: 30 April 2022 at 12:34am
For Android, I have Frequency Sound Generator, and Sound Meter. Where Apple scores points over Android is their control of both hardware and software, but that's still no reason for me to use them. There are fairly large differences in the audio performance of Android phones, so I would suggest you use the best quality ones you can and also use the same brand. I've used Samsung Galaxy and A series for the last 10 years or so, and they test very well for line output.


Posted By: Jack1991
Date Posted: 02 May 2022 at 12:32pm
Cool thanks man i will try them out soon. Do you just do it outside 1m away and with the speaker and phone on the floor?

Also what is the main aim for a frequency response curve, i assume its just to get rid of peaks and dips and to get as flat a line as possible?


Posted By: Jack1991
Date Posted: 08 May 2022 at 6:40pm
Any reccomendations for the frequency sweeps? Ive been reading up to try and answer this myself but im still not 100% sure.

Im assuming Linear and Sine Wave. But not sure on sweep time?

Hoping to have a play this evening or 1 evening this week, once the other noises die down in my garden and neighbours.

Also i fitted a volt meter this weekend too. To keep an eye on the battery levels. Have been told 15v is the lowest you should let a 18v lithium Makita battery get to before it will ruin it. Weirdly a fully charged 18v makota battery is 20.4v



Posted By: Jack1991
Date Posted: 30 May 2022 at 7:36pm
Took it down the field on Friday just gone, with a few mates and we had it on about 1/2 volume for a couple hours, then about 3/4 volume for a further couple hours and it proper pumps! Im well happy with it. The voltage only dropped from 20.4 to 20.2 in that whole time aswell, so i rekon it would last ages on 1 battery. That was 1x brand new 18v makita li-on 5ah battery.

On the poweramp app i was fiddling around with it for ages, but find it just sounds nicest with the bass knob set to 60% and the treble to 25%.
However as i increase the volume to around 3/4, the bass then needs to be reduced to around 40% or it starts to distort, but doing so didnt make it less bassy just kept it from distorting, if that makes sense.

Now i have heard it 'empty' although im happy with the sound i like to experiment anyway so i will try adding in some sound deadening on the 5 panels like Lucasdude suggested. And i will add on top in the centre of 3 opposing panels a bit of dacron dampening. And see how it sound with that.



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